HORSES

Question 1

What is the approximate life span of RBCs?

Answer 1

145 days

Question 2

“Splints” or Intraosseous desmitis

Answer 2

Is inflammation of the intraosseous ligament between the 3rd metacarpal (or metatarsal) bone with the small metacarpal (or metatarsal) bones. Periostitis occurs with new bone formation along the splint bones or small metacarpals (or metatarsals) usually due to repetitive concussion, excessive training, poor conformation, or improper shoeing. Radiographs are necessary to distinguish this condition from fractures of the splint bones.
Treatment: rest and NSAIDs

Question 3

What is the neutrophil lifespan?

Answer 3

10-11 hours

Question 4

A 5-year old female Quarterhorse has been tentatively diagnosed with duodenitis-proximal jejunitis (DPJ). What other cause of equine colic can DPJ closely resemble?
a. Ascarid impaction
b. Salmonella
c. Small intestinal obstruction
d. Nephrosplenic entrapment

Answer 4

small intestinal obstruction; both small intestinal obstruction and dodenitis-proximal jejunitis (DPJ) present with similar clinical signs. The problem is that a small intestinal obstruction will be a surgical disease, and duodenitis-proximal jejunitis responds better to medical treatment. The cause of duodenitis-proximal jejunitis remains unknown. Clinical signs include acte colic with increased respiratory rate, heart rate, and pain. Additionally, there will be lots of gastric reflux. After decompression of the stomach via nasogastric intubation and removal of excess gastric/intestinal fluid, horses with DPJ may appear much more comfortable.

Question 5

What body systems are primarily affected by equine herpesvirus?
a. GI & CNS
b. Respiratory & Integument
c. Respiratory & Reproductive
d. Integument & Reproductive
e. GI & Reproductive

Answer 5

Respiratory & Reproductive; the main signs seen with equine herpesvirus (EHV-1) or equine viral rhinopneumonitis are copious nasal discharge in foals and abortion in mares. It can also cause CNS signs and occasionally can cause neonatal death from pneumonia. The nasal discharge in foals is sometimes referred to as “Snots” in horses and may be serous or purulent if there is secondary bacterial infection.

Question 6

Normal position for an equine fetus ready to be delivered is ____________?
a. anterior presentation, dorsopubic position with forelimbs extended
b. posterior presentation, dorsosacral position, with forelimbs flexed at the carpi
c. anterior presentation, dorsopubic position with forelimbs flexed at the carpi
d. anterior presentation, dorsosacral position with forelimbs flexed at the carpi
e. anterior presentation, dorsosacral position with forelimbs extended

Answer 6

anterior presentation, dorsosacral position with forelimbs extended; this means the fetus’s head is coming out first rather than the rear end. It is positioned such that the dorsum of the fetus is adjacent to the sacrum of the mare, and the forelimbs are completely extended forward. Abnormal postures lead to the fetus takin up more room in the pelvis and can lead to dystocia if not corrected.

Question 7

Which tapeworm is not found in horses?
a. Paranoplocephala mamillana
b. anoplocephala perfoliata
c. dipylidium spp.
d. anoplocephala magna

Answer 7

Dipylidium spp.; dipylidium tapeworms are found in dogs and cats. The other three tapeworm species can occur in horses. Clinical signs include unthriftiness, anemia, and colic. Infejctions can be treated with praziquantel. Pyrantel salts are only effective against Anoplocephala spp. but not P. mamillana.

Question 8

Which is true about a patent urachus?
a. Patent urachus is considered normal in foals up to 2 weeks of age
b. patent urachus, as described in this case here, will resolve with administration of a NSAID, such as flunixin meglumine
c. chemical cautery is the most effective treatment for patent urachus, which should be performed as soon as possible in this case
d. patent urachus, as described in the case here, requires systemic antimicrobial therapy and possibly surgical removal
e. patent urachus is a heritable sex linked traint on the X-chromosome and the foal and mare should not be bred

Answer 8

patent urachus, as described in the case here, requires systemic antimicrobial therapy and possibly surgical removal; some neonatal foals have a patent urachus for a few days and leak clear, yellow urine. However, if the history describes a purulent discharge which would suggestion an infection it’s a more serious condition. Thus systemic antimicrobials are indicated to eliminate infectious agents. In some instances (large urachal abscess, urachal necrosis, uroabdomen), surgical removal and repair are indicated. Cases of acquired patent urachus associated with navel infection should not be treated with cauterizing agents as this will potentially seal the urachus and prevent drainage of the infection. In the absence of infection, many cases of patent urachus will close on their own. However, if the problem persists, an US should be performed to reveal any abnormalities associated with the internal structure of the umbilicus. Patent urachus is not know to be a genetic mutation.

Question 9

How much sodium bicarbonate must be given to a 470kg horse that has a base deficit of 13 to completely correct this deficit?
a. 1100 mEq
b. 900 mEq
c. 600 mEq
d. 4500 mEq
e. 2400 mEq

Answer 9

2400 mEq; 0.4 x BW x Base Deficit = sodium bicarbonate –> 0.4 x 470 x 13 = 2444

Question 10

What is the equation for calculating how much sodium bicarbonate is necessary to correct a base deficit?

Answer 10

0.4 x BW x Base Deficit

Question 11

How do you calculate a patient’s base deficit?

Answer 11

Normal HCO3 concentration - patient’s HCO3 concentration = base deficit. (normal blood HCO3 concentration is arround 22-24 mEq)
23 - patient’s HCO3 = base deficit

Question 12

A horse has numerous annular lesions of alopecia and scaling on it’s face and neck. It is treated with Ivermectin and resolves. What is the most likely diagnosis?
a. Onchocerca cervicalis
b. Culicoides spp.
c. Borrelia burgdorferi
d. Habronema muscae

Answer 12

Onchocerca cervicalis; clinical signs result from hypersensitivity to dying microfilariae. However, most infected horses will remain asymptomatic. Lesions include patchy to diffuse alopecia, erythema, scaling. The lesions are usually not pruritic, although there are few reports of severe pruritis. A “bulls-eye” or circular lesion in the center of the forehead is highly suggestive of onchocerciasis. Ventral midline dermatitis is also commonly associated with the disease.

Question 13

Name this abnormality in a 2 month old Thoroughbred.
a. Subchondral bone cyst
b. Osteoarthritis
c. Carpus valgus
d. Carpus varus
e. Septic arthritis

Answer 13

Carpus valgus; outward (or lateral) deviation of the limb. Carpus varus is the inward deviation of the limb.

Question 14

What is the most common infectious cause of infertility in the US in the horse?
a. Taylorella equigenitalis
b. Pseudomonas aeruginosa
c. Klebsiella pneumoniae
d. Streptococcus equi ssp. zooepidemicus

Answer 14

Streptococcus equi ssp. zooepidemicus; this is a common inhabitant of the external genitalia of mares and stallions and causes disease when there is a predisposing factor such as immunosuppression, pneumovagina, or damage to the endometrium. Taylorella equigenitalis is the causative agent of contagious equine metritis, which is rare in the United States. Kelbsiella and Pseudomonas can both cause infertility but are consdiderably less common than Streptococcus zooepidemicus.

Question 15

What is a cause of diarrhea that is seasonal and is associated commonly with laminitis?
a. Clostridium sordellii
b. Corynebacterium pseudotuberculosis
c. Salmonella typhimurium
d. Neorickettsia risticii (Potomac Horse Fever)

Answer 15

Neorickettsia risticii (Potomac Horse Fever); commonly causes diarrhea in the warmer months and is observed in horses stabled near bodies of water. Although a trematode vector is suspected the exact pathogenesis remains an area of study. The treatment is oxytetracycline. While many causes of diarrhea can result in laminitis, PHF has been associated with laminitis frequently. Salmonella can also result in the clinical signs noted, but is not restricted by season.

Question 16

What is a first-degree atrioventricular block characterized by?
a. a widening of the QRS complex
b. an increase in the P-R interval
c. a lack of P waves
d. an increase in the S-T interval

Answer 16

an increase in the P-R interval; the impulse is still able to transmit through the atrioventricular conduction system, it just takes longer, hence the increased P-R interval

Question 17

What is a second-degree atrioventricular block characterized by?
a. a widening of the QRS complex
b. an increase in the P-R interval
c. a lack of P waves
d. an increase in the P-R interval until a QRS is dropped

Answer 17

an increase in the P-R interval until a QRS is dropped; intermittent AV block in which some but not all P waves are conducted to the ventricles

Question 18

What is a third-degree atrioventricular block characterized by?
a. a widening of the QRS complex
b. an increase in the P-R interval
c. a lack of P waves
d. an increase in the P-R interval until a QRS is dropped

Answer 18

lack of P waves; there is complete dissociation between the P waves and the QRS complexes. Frequently in third-degree block, the HR is slower than normal because a subservient pacemaker (i.e. in the AV node or ventricle) has to fire to cause ventricular contraction

Question 19

What does a melting ulcer indicate?
a. Trauma
b. Globe rupture
c. Descemetocele
d. Infection
e. Indolent ulcer

Answer 19

Infection; when a corneal ulcer takes on a melting appearance this indicates that the ulcer is deepening into the stroma of the cornea due to infection. A melthing ulcer can exist without having a descemetocele or globe rupture. If this is the case, you should consider swabbing the ulcer for cytology and culture to treat the ulcer most effectively. In horses, melting ulcers are most commonly due to infection with Pseudomonas.

Question 20

What does Gasterophilus cause in horses?
a. Dermatitis
b. Diarrhea
c. Gastritis
d. Anemia
e. Vomiting

Answer 20

Gastritis; the larvae of Gasterophilus embed themselves in the mucosa of the stomach and can cause a mild gastritis or no clinical signs. The eggs are laid on the hairs of the horse but do not typically cause dermatitis. They do not develop diarrhea from these infections and horses do not vomit. Anemia does not occur with Gasterophilus infections.

Question 21

What stimulates antidiuretic hormone (ADH) secretion in the horse?
a. hypoosmolality and decreased circulating volume
b. hypoosmolality and increased circulating volume
c. hyperosmolality and increased circulating blood volume
d. hyperosmolality and decreased circulating blood volume

Answer 21

hyperosmolality and decreased circulating blood volume; ADH increases renal water reabsorption and urine osmolality by increasing permeability of the collecting tubules. Osmoreceptors in the hypothalamus detect subtle changes in plasma osmolality. If osmolality rises, you will hope to see ADH secretion so that the urine excreted would be more concentrated. The same is true if circulating volume decreases; thus, a lesser voume of water would be lost. ?When ADH secretion does not occur or if kidneys are unable to respond to ADH, this is likely diabetes insibidus, and animals will be very PU/PD and have extremely dilute urine.

Question 22

A 16 yr, pregnant Standardbred mare presents with an acute onset of colic. ?On presentation she has a HR of 64, RR of 32, and is pawing, CRT is 3 seconds, MM are red, rectal temp is 101.3F. Gastrointestinal sounds are completely absent, and gastric reflux yielded 16L of brown to yellow colored fluid. What is the possible diagnosis?
a. left dorsal colon displacement
b. cecal impaction
c. right dorsal colon displacement
d. nephrosplenic entrapment
e. mesenteric rent

Answer 22

mesenteric rent; this can result in a strangulating intestinal obstruction. Other causes of strangulating intestinal obstructions include intussusceptions, hernias, epiploic foramen incarceration, volvulus, and strangulating lipomas. Left dorsal colon displacement is the same thing as splenic entrapment and will typically not result in a colic presentation is severe.

Question 23

An 8 yr old Warmblood gelding is presented for repeated but intermittent clinical signs of exercise intolerance, weakness, muscle fasiculations and a stiff abnormal hind-limb gait. The owners do not ride their horse regularly, but notice these clinical signs most often at the start of a trail ride. Based on the histroy, signalment and clinical signs, which of the following diseases do you suspect?
a. malignant hyperthermia
b. immune-mediated myositis
c. polysaccharide storage myopathy (PSSM)
d. Glycogen branching enzyme deficiency (GBED)
e. hyperkalemic periodic paralysis (HYPP)

Answer 23

Polysaccharide Storage Myopathy (PSSM); based on the breed and clinical signs this should be a top consideration. A subset of horses have a storage disorder in which there is an accumulation of glycogen and abnormal polysaccharide within the skeletal muscle. PSSM has been linked to an autosomal dominant mutation of the glycogen synthase gene in Quarter Horses. However, other breeds, such as Paint, Appaloosas, Warmbloods and draft horses caan also be affected. Horses with PSSM often have elevations in creatine kinase and aspartate aminotransferase; rhabdomyolysis in PSSM likely results from an energy deficiency within the contracting muscles.

Question 24

What should antibody levels be in a newborn foal using an ELISA to have effective passive transfer?
a. > 800 mg/dL
b. 600-800 mg/dL
c. 400-600 mg/dL
d. < 400 mg/dL

Answer 24

> 800 mg/dL; foals are born immunocompetent but lack antibodies when born, therefore they must ingest maternal antibodies through colostrum. For adequate passive transfer, antibodies should be greater than 800 mg/dL.

Question 25

A one-week old female foal is having eye problems - blepharospasm and epiphora. On exam the lower eyelid margin is inverted inward, what is the diagnosis?
a. ocular onchocerciasis
b. entropion
c. fungal keratitis
d. ectropion
e. chelazion

Answer 25

Entropion; this is a common condition in foals where their lower eyelid is inverted and can cause conjunctivitis or keratitis. The conditon will usually correct sponataneously but sometimes will require treatment to evert the lid. One method for this is to use a local anesthetic, mechanically evert the lid, and staple it. Alternatively, surgical correction can be performed, but is rarely indicated. Ectropion is the opposite condition where the eyelid everts out and can lead to exposure keratitis, but this is uncommon in horses. Ocular onchocerciasis is caused by microfilariae and is seen in about 50% of horses with cutaneous onchocerciasis.

Question 26

A Quarter Horse gelding is presented for symmetric ataxia, weakness, and spasticity of all limbs, but worse in the hind limbs. When walking, the horse frequently drags his toes and the hind limbs frequently interfere with one another. Based on the signalment, history and PE findings, what is the most likely diagnosis?
a. Equine Protozoal Myeloencephalitis (EPM)
b. Equine Degenerative Myeloencephalopathy (EDM)
c. Botulism
d. Cauda Equina Syndrome
e. Equine Motor Neuron Disease (EMND)

Answer 26

Equine Degenerative Myeloencephalopathy (EDM); the clinical signs are most consistent with EDM. Cervical Vertebral malformation (Wobblers) is also a possibility, but was not an option. The cause of EDM is unknown, but this disease typically affects young horses (<2-3 years of age; but older horses can develop the disease). Clinical signs are aa result of diffuse neuronal fiber degeneration of various portions of the central nervous system. This disease has been associated with low serum vitamin E concentrations, suggesting the oxidative damage may play a role in the development of disease. EMND is typically associated with muscle tremors, shifting of weight while standing, muscle atrophy and recumbency. Botulism is assoicated with generalized muscle weakness. Cauda equina syndrome causes analgesia of the perineum. EPM can cause a range of clinical signs, but is typically with asymmetric neurologic deficits.

Question 27

A 1 yr old Thoroughbred presents for a pre-purchase exam. On PE, there is a mild gait abnormality at the initiation of exercise which then diminished. Additionally, the horse is very heavily muscled. An electromyographic examination reveals a crescendo-decrescendo signal of high-frequency repetitive bursts with a characteristic ‘dive- bomber’ sound. What is the diagnosis?
a. Hyperkalemic periodic paralysis
b. phosphorylase deficiency
c. hypocalcemia
d. myotonia
e. exertional rhabdomyolysis

Answer 27

Myotonia; these clinical signs and findings are consistent with a horse with myotonia. Etiology is not completely understood, but a fenetic component is suspected. The ‘dive bomber’ sound heard on EMG is produced by repetitive firing after contraction of affected muscle fibers and is essentially pathognomonic for myotonia. Hyperkalemic periodic paralysis would be seen in Quarter Horses, Paint Horses, and Appaloosa horses rather than Thoroughbreds.

Question 28

What cytologic finding of a bronchoalveolar lavage (BAL) fluid would be supportive of Recurrent Airway Obstruction (RAO) also known as chronic obstructive pulmonary disease?
a. Eosinophilic inflammation
b. Mononuclear inflammation
c. Mixed inflammatory response (neutrophils, macrophages, and eosinophils)
d. Neutrophilic inflammation

Answer 28

Neutrophilic inflammation; in health BAL fluid primarily consists of macrophages. However, in RAO, neutrophils are the predominant cellular finding. RAO typically affects older horses aand is aa response to environmental allergens. The classic case is the horse that is stalled in the winter and possibly house in the vicinity of hay storage. When the horse is exposed to hay allergens (via inhalation), bronchoconstriction and neutrophilic inflammation occur.

Question 29

A fundic exam is performed on the eye of a horse and a worm appears to be migrating through the conjunctiva. Due to the location and appearance of this parasite what parasite is suspected?
a. Dirofilaria
b. Toxocara
c. Oxyuris
d. Thelazia

Answer 29

Thelazia; genus of nematode worms (eyeworms) which are found in the ocular tissues. Adults are usually found in the eyelids, tear glands, tear ducts, or the nicitating membrane. They may be found in the eyeball itself under the conjunctiva or in the vitreous. Thelazia are transmitted by Diptera (flies) which do not bite but feed on tears. Toxocara, which causes ocular migrans, usually causes granulomas which may be seen in the retina and appear more circular.

Question 31

When can a horse that has been treated for Strangles be reintroduced to the other horses in the stable?
a. It is best to wait until the horse has negative serology to antibodies against the SeM virulence factor
b. It is never safe to reintroduce the horse because most horses become lifelong carriers and shed the organism
c. He should vaccinate all of the horses at his stable and then reintroduce the horse 3 weeks later
d. It is best to wait for 30 days after resolution of signs and then perform 3 consecutive weekly negative nasopharyngeal cultures
e. Strangles is not contagious to other horses

Answer 31

It is best to wait for 30 days after resolution of signs and then perform 3 consecutive weekly negative nasopharyngeal cultures; strangles can be a difficult disease to control and vigilant preventative measures are necessary to minimize transmission as a small percentage of horses develop persistent infection of the guttural pouches associated with purulent inflammation or the presence of chondroids. These carriers can be detected either by culture or by detection of S. equi DNA using the polymerase chain reaction (PCR) test. PCR is a more sensitive test but also more expensive and may have false positives in recently infected horses due to residual DNA from dead bacteria. If an animal tests positive an endoscopic evaluation of the guttural pouch is recommended, chondroids removed, and guttural pouches treated by flushing and infusing 5 million units of penicillin G in 3% gelatin. In additon, these horses should be treated with penicillin G IM for 7 days, isolated for 30 days, and then retested with the 3 consecutive series of nasopharyngeal swabs and cultures. Vaccine against S. equi are available.

Question 32

A horse was found dead in the pasture, on examination the mucous membranes are cherry red and there is an almond smell to the horse. What is the most likely diagnosis?
a. Cyanide toxicity
b. Carbon monoxide toxicity
c. Rhododendron toxicity
d. Black walnut toxicity

Answer 32

Cyanide toxicity; cyanide does not allow hemoglobin to release oxygen, thus causing the cherry red lips. It is found in cherries, chokecherries, arrow grass and Sudan grass. Large amounts must be consumed. There is a bitter odor of almonds to the GI tract with this toxicity. Treatment is sodium nitrate and sodium thiosulfate. Prognosis is poor due to rapid onset. Carbon monoxide can cause cherry red mucous membranes, but would not cause the almond smell.

Question 32

A hot July day in Michigan, an adult horse develops acute dpression, high fever and profuse watery diarrhea. On presentation the horse’s HR is 80bpm, RR 36brpm, and temperature is 103.4F. The horse is moved to isolation and it seems to be very sore on it’s forelimbs. What would the top rule-out be and how would it be confirmed?
a. Salmonella typhimurium, supportive test - culture of feces
b. Canthairdin toxicity (Blister beetle toxicity), Supportive test - measure blood cantharidin
c. Neorickettsii risticii, Supportive test - a PCR of blood or feces
d. Clostridium chauvoei type A, Supportive test - measure clostridial toxins via ELISA

Answer 32

Neorickettsii risticii, Supportive test - a PCR of blood or feces; the causative agent of Potomac ?Horse Fever (PHF). The clues that indicate PHF are the time of year (typically occurs in summer in northern states), the high fever and diarrhea, presence of laminitis. The horse is also dehydrated and has a profound leukopenia.

Question 33

Where do carpal fractures in horses most commonly occur?
a. 3rd and 4th carpal bones
b. ulnar and accessory carpal bones
c. radial and 3rd carpal bones
d. accessory, 2nd and 3rd carpal bones

Answer 33

Radial and 3rd carpal bones; most carpal fractures in horses occur at the dorsal aspect of the carpal joint, particularly at the radial and 3rd carpal bones. Both chip and slab fractures may occur. These fractures usually result in immediate swelling and severe lameness. Diagnosis is based on radiographs and arthroscopic surgical repair is frquently the treatment of choice.

Question 34

For neonatal isoerythrolysis to occur, which of the pairs must mate?
a. Stallion negative for Qa and mare positive for Qa
b. Stallion positive for Qa and mare positive for Qa
c. Stallion positive for Qa and mare negative for Qa
d. Stallion negative for Qa and mare negative for Qa

Answer 34

Stallion positive for Qa and mare negative for Qa; for neonatal isoerythrolysis to occur, the mare must develop antibodies to the foal’s RBC antigens. Aa and Qa are the two antigens most frequently implicated in this condition. For this condition to occur, the foal must inherit the Aa or Qa antigen from the stallion, and the mare must be negative for the antigen. Then, when the mare becomes exposed to the foal’s RBC antigens she makes antibodies. When she passes these antibodies to the foal through colostrum an acute hemolytic event will occur in the foal. In most cases the first time a mare has a foal with the antigen she will not produce sufficient antibodies to cause severe damage tot he foal. Therefore, this condition is usually seen in multiparous dams or in mares that have previously had a blood transfusion that exposed them to the RBC antigen.

Question 35

A 7yr old, Arabian gelding is presented for clinical signs of fever and lethargy of 2 days duration along with signs of hind-limb ataxia and muscle fasiculations of the face and neck. A CBC, Chem, and CSF tap from the lumbosacral space are performed. What is the most likely diagnosis and the most appropriate diagnostic test to confirm?
a. EHV; isolation of buffy coat, nasal swab and/or CSF
b. West nile Encephalitis (WNV); erum immunoglobulin M (IgM) capture ELISA
c. Cervical vertebral malformation (CVM); Myelography of the cervical spine
d. Equien Protozoal Myelitis (EPM); Western Blot of CSF
e. Verminous encephalitis (Micronema deletrix); culture of CSF

Answer 35

West nile Encephalitis (WNV); erum immunoglobulin M (IgM) capture ELISA; the mosquito born flavivirus that affects horses in multiple areas of the US. Clinical signs are variable and can be mild (muscle fasiculations, slight ataxia) to severe (recumbency). Of note, muscle fasiculations is somewhat characteristic of WNV, but fever may be detected in all patients. A readily available diagnostic test is the serum IgM capture ELISA which will detect infection, even in the face of vaccination. There is a vaccine available for WNV, making the clinical presentation less common.

Question 36

What statement is most accurate regarding the Coggin’s test for equine infectious anemia?
a. it is effective at diagnosing infection in chronic asymptomatic carriers
b. it is most effective during an acute episode of anemia
c. the test is effective in foals because it detects antigen
d. false negatives can occur in foals due to maternal antibody interference

Answer 36

it is effective at diagnosing infection in chronic asymptomatic carriers; the Coggin’s test is a test for antibody; therefore it carries several drawbacks/limitations. In acute episodes of equine infectious anemia (EIA), there is often not yet adequate production of antibody to detect by this test. In foals, false positives can occur due to acquisition of the antibody in colostrum. Persistently infected horses constitute the majority of cases, and because they are under constant antigenic stimulation, they maintain aantibody production and can be very accurately diagnosed with the condition by the Coggin’s test.

Question 37

What is the underlying pathophysiology of osteochondrosis in horses?
a. a defect in the production of aggrecans and glycosaminoglycans
b. a defect in endochondral ossification
c. a defect in cartilage production
d. a defect in the synovial lining
e. a defect in the rate of bone growth

Answer 37

A defect in endochondral ossification; osteochondrosis develops when there is an abnormal endochondral ossification resulting in the production of a cartilaginous flap within a joint. In young horses, a diagnosis is frequently made when first training. Severity of lameness can vary greatly. Osteomyelitis, trauma, and septic arthritis may be good differentials.

Question 38

What is the most common way in which Equine Herpesvirus-1 is transmitted?
a. Blood sucking arthropods
b. fecal-oral
c. inhalation
d. venereally

Answer 38

Inhalation; EHV-1 or equine viral rhinopneumonitis is a rapidly-spreading disease that is spread by inhalation directly or indirectly from infected nasal discharge, aborted fetuses or placenta. EHV-3, the cause of equine coital exanthema is spread venereally. Both EHV-1 and EHV-4 are cause of rhinopneumonitis, but they are very important because they also result in abortions. EHV-1 is also assoicated with myeloencephalitis and has resulted in various outbreaks in the U.S and abroad. EHV-1 is the main cause of paresis, abortions, and neonatal foal deaths.

Question 39

A 2 yr old mare presents for intermittant left thoracic limb lameness which resolves after working the horse. On PE, a palmar metacarpal bulge and inflammation could be palpated. What is your diagnosis?
a. Tendonitis
b. Laminitis
c. Suspensory ligament desmitis
d. Subsolar abscess

Answer 39

Tendonitis; the intermittant lameness and bulge at the metacarpals are classic for bowed tendon or tendonitis.

Question 40

A 3 month old Arabian colt is presented for 3 episodes of penumonia; the first episode of penumonia was observed at 7 weeks of age. Each episode of pneumonia is responsive to oral antimicrobials, but when these are discontinued, evidence of respiratory disease occurs several days later. A complete blood count reveals that the foal is persistently lymphopenic. What conditon do you suspect?
a. Leukocyte adhesion disorder
b. viral penumonia
c. Combined immunodeficiency
d. IgM deficiency

Answer 40

Combined immunodeficiency; any arabian foal with persistent infection should be suspected of having this heritable immunodeficiency of B and T lymphocytes. Typically, foals with CID do not demonstrate evidence of repeated infection until maternal antibodies begin to wane. There is no treatment for this disease.

Question 41

A 3 yr old steeplechaser horse presents for lameness. The owner reports that the horse developed a short-striding lameness of the left pelvic limb after an event and that the horse is reluctant to bear full weight on the left hind leg. On exam, there is a prominent bump to the left of midline on the topline of the hindquarters (croup). What is the most likely daignosis?
a. Sacroiliac luxation
b. Stringhalt
c. Upward fixation of the patella
d. Gonitis
e. Ruptured peroneus tertius

Answer 41

Sacroiliac luxation; jumping horses are commonly affected. The short strided gait is consistent with but not specific for this condition. The raised croup differentiates sacroiliac luxation from other options in this case. Upward fixation of the patella is not a traumatic condition as you should suspect based on the history. It does cause a short strided gait and toe-dragging. The tell-tale sign of this conditionis a hind limb in rigid extension that is unable to flex. Gonitis is a term indicating stifle arthritis that is nonspecific to the underlying cause. Stringhalt is involuntary flexion of the hind limb and is usually bilateral. Stringhalt is treated with lateral digital extensor tenectomy. A ruptured peroneus tertius is characterized by the ability to simultaneously extend the hocke and flex the stifle.

Question 42

Which of these is not indicated as the initial treatment of a suspected Streptococcus equi ssp. equi infection, causing mandibular and retropharyngeal lymph node abscessation in a 2 year old horse?
a. isolating the horse
b. systemic penicillin
c. lancing the abscess ventrally
d. aspirating the lymph nodes for culture and cytology

Answer 42

Systemic antibiotics; stretococcus equi ssp. equi is the agent causing strangles in horses. When they have lymph node abscessation, antibiotivs are contraindicated because they will prolong the course of the disease but will not eliminate it. Because this disease is spread by direct contact, isolation of the horse is important. To obtain a definitive diagnosis, the lymph nodes could be aspirated. The treatment is to lance the abscesses ventrally and dispose of the material to prevent spread of the organism.

Question 43

Which of the following is not considered a predisposing factor to a horse developing laminitis?
a. high carbohydrate diet
b. endometritis
c. excessive weight bearing on a single limb
d. acute systemic disease
e. application of horse shoes

Answer 43

application of horse shoes; laminitis is an inflammatory conditoin of the lamina in one or more feet of a horse. It is often a manifestation of systemic disturbances such as endometritis and salmonellosis. A high carbohydrate diet (carbohydrate overload), excessive weight bearing on an individual let, and corticosteroid administration also predispose a horse to laminitis.

Question 44

While examining the blood smear from a horse, multiple intracytoplasmic inclusion bodies are seen inside the neutrophils that appear as aggregates of round dark purple dots. What do you suspect these indicate?
a. Neorickettsia risticii
b. Herpesvirus type 3
c. Borrelia burgdorferi
d. Anaplasma phagocytophilum

Answer 44

Anaplasma phagocytophilum; (previously known as Ehrlichia equi). Anaplasma phagocytophilum infection can cause morulae to be present in neutrophils and eosinophis. Neorickettsia risticii (PHF) can cause morulae in monocytes but these are rarely seen on blood smears. Borrelia organsims are not seen in the peripheral blood and herpes inclusion bodies are intranuclear and would not be seen in a blood smear.

Question 45

A 3 month old paint colt presents after flipping over backward while being led by the owner the previous day. Clinical signs at the time of presentation are show below (head tilt, flaccid ear, muzzle deviation). Based on the history and clinical signs, what cranial nerves are damaged and what is the most likely diagnosis?
a. Cranial nerves VII and VIII (right side); fracture of the basisphenoid bone
b. Cranial nerves V and VII (left side); atlanto-occipital malformation
c. Cranial nerves VII and VIII (left side); fracture of the basisphenoid bone
d. Cranial nerves V and VII (right side); atlanto-occipital malformation
e. Cranial nerves V and VIII (left side); fracture of the sphenoid bone

Answer 45

Cranial nerves VII and VIII (left side); fracture of the basisphenoid bone; this is a common injury when a fractious young foal rears up and falls backward on the poll. The basisphenoid bone becomes injured resulting in injury to cranial nerves VII and VIII. Damage to the facial nerve results in the muzzle deviation (opposite direction of the side of injury, in this case deviation to the right), ptosis of the left eye and drooping of the left ear. Damage to the vestibular nerve results in head tilt.

Question 46

What is the average gestation length of a mare?
a. 265 days
b. 225 days
c. 345 days
d. 305 days
e. 405 days

Answer 46

345 days; gestation can range from 330-360 days. Artifical lighting is often used in mid-December to promote estrus to occur in mid-February to increase the likelihood the horses will foal in mid-January which is the best time for race horses (since all horses have a January 1st birthday). Most foals are considered premature if born prior to 320 days and prolonged gestation is associated with greater than 365 days.

Question 47

When does neonatal isoerythrolysis occur in horses?
a. in utero
b. 1-4 week old foals
c. 1-4 month old foals
d. 0-4 day old foals

Answer 47

0-4 day old foals; in utero, the foal is protected from the mare’s antibodies due to epitheliochorial placentation. The foal takes in colostrum during it’s first 24 hours of life from the mare and develops the condition fairly acutely. Remember NI develops because the newborn foal expresses alloantigens on its RBCs inherited from the sire that the mare does not have. If the mare becomes sensitized to the sire’s specific antigen, maternal antibodies are produced and absorbed by the foal soon after birth. This subsequently results in lysis of the RBCs. Pre-parturient blood testing between the mare and stallion may help in identifying the likelihood of this occurring.

Question 48

A 2 yr old mare reared over backwards and came up with epistaxis. She is ataxic and has a slight left head tilt. Endoscopic exam confirms the origin of the epistaxis in the guttural pouch. What is the top differential diagnosis?
a. laceration of the maxillary vein
b. ruptured longus capitis
c. maxillary fracture
d. ethmoid hematoma

Answer 48

ruptured longus capitis; the longus capitis and rectus capitis ventralis insert onto the basisphenoid and occipital bones. Rupture is usually caused by rearing over backwards. Epistaxis and varying degrees of brainstem signs are typically seen. Treatment for a ruptured longus capitis is primarily symptomatic and consists of stall rest and antibiotics to prevent secondary infection. Prognosis depends on the severity of neurological damage. Ethmoid hematoma is a progressive and locally destructive mass of the nasal passages or sinuses. This disease process could cause epistaxis but is not consistent with the recent trauma or the endoscopic findings in this case. Maxillary fracture would likely result in additional clinical signs at the fracture site and would not explain the brainstem signs or endoscopic findings. The maxillary vein is a branch of the external jugular vein. Traumatic laceration is very uncommon and depending on the location of the laceration, would cause external hemorrhage rather than epistaxis.

Question 49

When performing a fundic exam on a horse with uveitis, there are multiple dark dots on the tapetum, what do these dots likely indicate?
a. a normal finding
b. hypertension
c. fungal infection
d. previous chorioretinitis
e. active chorioretinitis

Answer 49

A normal finding. The equine tapetum is penetrated by small choroidal vessels that appear as dark dots. These are sometimes affectionately referred to as the stars of Winslow.

Question 50

A 18 yr old horse presents for not shedding out this spring and having less energy. The horse is hirsute, has loss of muscle mass, and has evidence of chronic laminitis. The owner also complains that the animal drinks twice as much as the other horses and seems to urinate a lot. What diagnosis is at the top of the differential list?
a. Hypervitaminosis D
b. Pituitary pars intermedia dysfunction
c. Hyperthyroidism
d. Parathyroid gland malfunction
e. Adrenal hyperplasia

Answer 50

Pituitary Pars Intermedia Dysfunction (Cushing’s); this condition is a result of hypertrophy, hyperplasia and micro- or macroadenoma of the pituitary pars intermedia that secretes increased amounts of propiomelanocortin peptides. Adjacent pituitary tissues are compressed and secrete less of some other peptides. Data suggests that horses with this disease have hypothalamic dysfunction and decreased amounts of dopamine.

Question 51

What is the most common gastric neoplasia in the horse?
a. lymphosarcoma
b. squamous cell carcinoma
c. mesothelioma
d. adenocarcinoma

Answer 51

SCC; presenting signs are weight loss and colic

Question 52

A 4 month old Thoroughbred colt with a 2 week history of weight loss, fever, and increased respiratory rate. Pneumonia is suspected, based on the picture of the lesion on thoracic US, what is the most likely cause?
a. E. coli pneumonia
b. Equine herpesvirus pneumonia
c. Streptococcus zooepidemicus pneumonia
d. Rhodococcus equi pneumonia

Answer 52

Rhodococcus equi pneumonia; R. equi is the most likely cause resulting in pulmonary abscess formation that may be noticed on thoracic US. In the US, the capsular structure with an anechoic center represents a fluid-filled abscess. R. equi is typically observed in older foals (2-6 months of age) and demonstrates a slow insidious onset characterized by some or all the following findings: weight loss, fever, cough, nasal discharge, increased respiratory effort, and ill-thrift. US of the chest can provide a quick screening test for foals with R. equi pneumonia. All the other pathogens can cause pneumonia but are not classically associated with abscess formation.

Question 53

Which region of the body is the most common site of melanoma formation on gray horses?
a. ear tips
b. prepuce
c. perineum and tail base
d. periocular and face
e. dorsal trunk

Answer 53

perineum and tail base; melanomas occur in up to 80% of gray horses. They occur most commonly on the perineum and tail base but can arise anywhere on the body. Most melanomas of gray horses are benign with varying degrees of invasiveness. They have potential to develop into malignant tumors. Treatment includes surgery or cryosurgery. Horses that develop one melanoma are predisposed to developing others in the future.

Question 54

An 18 yr old mini horse mare is presented with signs of lethargy, anorexia, and mild diarrhea of 5 days duration. Upon PE the mare is quiet and lethargic, HR = 56bpm, RR = 16brpm, rectal temp 102.8F. The mare postures to urinate but only produces. asmall volume of urine. In addition, intestinal borborygmi are slightly increased and loose feces is noted staining the tail. It is suspected the mare has colitis. What would be the most abnormal clinicopathologic data measured from your blood sample based on the appearance, history and clinical exam?
a. hyponatremia, hypochloremia and hypokalemia suggestive of AKI
b. neutropenia, hyponatremia and metabolic alkalosis suggestive of colitis and pre-renal azotemia
c. elevation in serum triglycerides, gamma glutamyl transpeptidase (GGT), and sorbital dehydrogenase (SDH) suggestive of hyperlipemia and hepatic lipidosis
d. elevations in serum fatty acids and cortisol along with hypoglycemia suggestive of pituitary pars intermedia dysfunction (equine Cushing’s syndrome) with secondary colitis

Answer 54

elevation in serum triglycerides, gamma glutamyl transpeptidase (GGT), and sorbital dehydrogenase (SDH) suggestive of hyperlipemia and hepatic lipidosis; unlike other larger sized horses, minis are susceptible to the development of hyperlipidemia and hepatic lipidosis as a result of anorexia; the anorexia typically results from a primary disease, in this case mild colitis. Because of the negative energy balance, fats are mobilized in excess resulting in the opaque appearance of the serum. AKI is associated with hyperkalemia and equine Cushing’s syndrome is associated with hyperglycemia.

Question 55

A 4 year old horse has a distorted hoof in the right front foot. When the horse walks the weight of the horse is not distributed uniformly with a focal area on the left side of the heel receiving most of the impact. Closer examination of the hoof reveals that the heel bulb on the left side of the foot is 1 cm higher than the opposite heel when viewed from behind and the coronary band is displaced proximally on the left side. There is flare of the hoof wall on the right side. No hoof cracks or wall separation is present. What is the name for this conditon?
a. Gonitis
b. Club foot
c. Seedy toe
d. Sheared heels
e. Scratches

Answer 55

Sheared heels; which is an asymmetry of the heels that is acquired due to imbalance of the foot resulting in one side of the heel contacting the ground before the other. This creates a shearing force and results in asymmetrical growth. Sheared heels are the best treated with repeated corrective trimming of the hoof and application of supportive bar shoes. The prognosis is good when the condition is corrected before additional complications arise. Seedy toe is characterized by a change in the character of the horn such that the inner surface is crumbly and there may be a cavity due to loss of substance. Scratches is a condition of chronic seborrheic dermatitis of the palmar/plantar aspect of the pastern. Club foot is a condition seen in horses secondary to contracture of the distal interphalangeal joint leading to a steep hoof wall and shortened toe. Gonitis is a term indicating stifle arthritis that is nonspecific to the underlying cause.

Question 56

Which enzymes are liver specific?
a. Gamma Glutamyl Transferase (GGT) and Alanine Aminotransferse (ALT)
b. Sorbitol Dehydrogenase (SDH) and Gamma Glutamyl Transferase (GGT)
c. Alanine Aminotransferse (ALT) and Aspartate Aminotransferase (AST)
d. Alkaline Phosphatase (ALP) and Sorbitol Dehydrogenase (SDH)

Answer 56

Sorbitol Dehydrogenase (SDH) and Gamma Glutamyl Transferase (GGT)l; SDH is found in the liver of all animals - an increase in serum SDH concentration suggests hepatocellular injury. Elevation in serum GGT is predominantely associated with biliary epithelial cells and is also liver specific. The other enzymes may be increased with liver disease, but may also arise from bone (ALP) or muscle (ALT, AST)

Question 57

12L of gastric reflux with a pH of 6.5 in a horse is most indicative of which of the following?
a. obstruction
b. gastric ulceration
c. colon displacement
d. normal finding

Answer 57

Obstruction; a pH that is greater than 5 suggests that small intestinal contents are refluxing into the stomach, resulting in an increased pH. Small intestinal ileus is another differential but was not an answer choice.

Question 58

A mare in the last month of gestation develops ventral edema from the udder to the xiphoid. She then becomes acutely painful and tachypneic and does not want to ambulate. What condition did the mare experience?
a. uterine torsion
b. ruptured prepubic tendon
c. colonic torsion
d. vaginal cystocele

Answer 58

ruptured prepubic tendon; this tendon courses along the ventrum and provides the major support for all the structures in the equine abdomen. It can rupture in late pregnancy, especially in obese draft mares. This is usually preceded by ventral swelling. If such swelling is noted, preventative measures should be taken such as restricting activity and possibly slinging the abdomen to provide support. This condition is very painful to the mare and may affect the ability to increase intra-abdominal pressure during parturition. Assisted parturition by a veterinarian should be strongly considered. A body wall hernia may also result in similar signs as a ruptured prepubic tendon.

Question 59

A 3 month old foal presents with a coal. On exam the RR = 50, temp = 103F, wheezes are present on auscultation and abdominal tucking on inspiration. Thoracic rads show an alveolar lung pattern with multifocal nodular, cavitary regions. What is most likely the diagnosis?
a. aspiration pneumonia
b. pneumocystis carinii
c. Streptococcus equi ssp. equi
d. Rhodococcus (Corynebacterium) equi

Answer 59

Rhodococcus (Corynebacterium) equi; the signalment and clinical signs are most consistent with Rodococcus equi infection. The radiographic finding of an alveolar pattern with multiple nodular regions is very indicative of Rhodococcus infection causing suppurative pyogranulomatous pneumonia. The nodular densities are Rhodococcus abscesses. Pneumonia from the other diseases in the answer choices might have an alveolar pattern on thoracic radiographs but would not be likely to have nodules. Pneumocystis is an opportunistic pathogen that can infect foals that are immunocompromised and cause interstitial penumonia.

Question 60

A horse presents with severe colic. At surgery, an infarction of a mesenteric artery is noted, what organism is aassociated with this lesion?
a. Strongyloides westeri
b. Dictyocaulus arnfieldi
c. Draschia megastoma
d. Strongylus vulgaris
e. Parascaris equorum

Answer 60

Strongylus vulgaris; migration of the larvae of Strongylus vulgaris and the corresponding immune response can result in thrombosis of the cranial or anterior mesenteric arteries leading to colic and infarction of the bowel. Paarascaris equorum causes colic in foals by causing intestinal impaction. Strongyloides westeri is a cause of foal heat dirrhea and caan migrate through the lungs causing damage. Dictyocaulus is a lungworm. Draschia megastoma is another migrating parasite that can cause focal granulomas in the lung.

Question 61

Which of these would be least expected in an adult horse that had ingested preformed Clostridium botulinum toxin?
a. Proprioceptive deficits
b. Dyspnea
c. Tongue hanging out
d. Mydriasis

Answer 61

Proprioceptive deficits; these are not usually present with botulism because it is not a myelopathy but is a neuromuscular disease. The toxin blocks release of acetylholine at neuromuscular junctions. The protruding tongue is a common early sign of botulism. Mydriasis occurs due to decreased pupillary response to light. Dyspnea occurs from paralysis of the diaphragm.

Question 62

A Thoroughbred racehorse is presenting for exercise intolerance. The only abnormality on exam is an irregularly irregular heart rhythm when the horse is at rest, with a heart rate of 45 beats/min. What is the most likely diagnosis?
a. sinus bradycardia
b. ventricular fibrillation
c. sinoatrial block
d. atrial fibrillation
e. sinus arrhythmia

Answer 62

Atrial fibrillation; is most commonly associated with exercise intolerance. There is no underlying rhythm to the heart beats. The ECG reveals absence of P waves and widely variant Q-Q intervals. There may or may not be a serious underlying heart disease.

Question 63

A 4 yr old Quarter horse presents for progressive neurologic signs of ataxia and paresis. There is asymmetric muscle atrophy of limb musculature noticed on exam. Which conditon is suspected?
a. Cauda equina neuritis
b. Wobbler syndrome
c. Equine degenerative myeloencephalopathy
d. Equine protozoal myeloencephalitis

Answer 63

Equine protozoal myeloencephalitis; can affect any age horse and is caused by Sarcocystis neurona. It should be suspected in this caase due to the asymmetry of clinical signs, as it is a multifocal disease of the CNS. Wobbler syndrome and degenerative myeloencephalopathy are diseases seen primarily in younger horses (<3-4 years of age). Degenerative myelopathy causes symmetrical ataxia. Cauda equina neuritis typically causes tail rubbing and urinary and fecal incontinence.

Question 64

What is the normal blood lactate in a healthy foal or horse?
a. Less than 2.5 mmol/L
b. Less than 7.5 mmol/L
c. Less than 5 mmol/L
d. Less than 10 mmol/L

Answer 64

Less than 2.5 mmol/L; it is important to remember a general reference range for all diagnostic laboratory data; lactate is commonly performed on a hand-held lactometer that does not provide a reference range. Lactate is produced from pyruvate in anaerobic environments to keep the process of glycolysis running. When a horse/foal is hypovolemic, blood lactate may increase because of poor blood perfusion to the body. Several studies have investigated blood and peritoneal lactate as a means of predicting survival in neonatal sepsis and equine colic. It may be necessary to look up these studies if you want exact findings, but not surprisingly, the higher the lactate, the poorer the prognosis.

Question 65

Which would not be seen on a navicular bone radiograph in a horse with navicular syndrome?
a. bone remodeling
b. osteolysis
c. osteophyte formation
d. enlarged vascular channels

Answer 65

osteolysis; navicular syndrome is a chronic degenerative condition of the navicular bursa and navicular bone. The precise etiology is unknown and is likely multifactorial involving the navicular bone, the suspensory ligament, the coffin joint, the navicular bursa, and the deep digital flexor tendon. Osteophyte formation, bony remodeling, and enlarged vascular channels are the hallmark radiographic findings in horses with navicular syndrome. Osteolysis is generally not a component of this conditon.

Question 66

What is chronic synovitis of the tibiotarsal joint known as in horseman’s terms?
a. Bog spavin
b. Sweeney
c. Curb
d. Bone spavin

Answer 66

Bog spavin; also known as tarsal hydrarthrosis, is often due to poor conformation and can result in increased synovial fluid formation. Both hindlimbs are usually affected. The horse is usually not lame from this condition. Distension may spontaneously appear and disappear in young horses. Bone spavin is osteoarthritis of the hock. Curb is thickening of the plantar tarsal ligament due to strain. Sweeney is supraspinatous contracture.

Question 67

A 6 yr old Quarter horse presents with the lesion in the photo, which of the following is true regarding equine sarcoids?
a. they usually regress spontaneously without treatment
b. surgical excision is nearly always curative
c. metastasis is common with advanced lesions
d. Papillomavirus is believed to play a role in the pathogenesis

Answer 67

Papillomavirus is believed to play a role in the pathogenesis; sarcoids are one of the most common tumors in horses. They are considred non-metastatic tumors in virtually all cases. For this reason, small lesions are sometimes treated with benign neglect, but they are not expected to regress. More advanced lesions or tumors in certain sites do need to be treated more aggressively. Unfortunately, no single treatment is universally effective. Recurrence rates after surgical excision are approximately 50%. Although there is still controversy surrounding this issue, either bovine papillomavirus or an equine variant is thought by many to play a role in development of these tumors.

Question 68

An 8 yr old horse presents for weight loss, dark urine, poor appetite, and loss of energy. On exam the temp is 101F, HR 56, RR 40. The urine is dark red and the sclera is slightly yellow. Labwork finds that SDH, GGT, ALP, AST, total bilirubin, direct and indirect bilirubin are all markedly elevated and PCV is 23%. What is the diagnosis?
a. West Nile Virus
b. Immune mediated thrombocytopenia
c. Equine infectious Anemia
d. Hepatic failure with secondary hemolysis
e. Thyzzer’s disease

Answer 68

Hepatic failure with secondary hemolysis; when the liver fails in the horse, it often results in a hemolytic crisis as RBCs become more fragile due to toxic metabolites in the blood. This crisis is usually fatal and indicates terminal stages of liver failure in the horse.

Question 69

A 2 yr old pony presents for lameness that worsens after activity or work. The pony displays mild lameness on your exam and is sensitive to deep palpation of the third metacarpal bone of the left front limb. Radiographs reveal periostitis and new bone formation along the second metacarpal bone. No fracture is present. What term describes this conditon?
a. Thoroughpin
b. High ringbone
c. Osselets
d. Splints
e. Sidebone

Answer 69

Splints; or metacarpal exostosis which involves periostitis of the interosseous ligament between the third and second metacarpal (or metatarsal) bone. Treatment usually involves rest and anti-inflammatory medications, although if the bony exostosies impinge on the suspensory ligament, surgical removal of the proliferative tissue may be indicated. Sidebone refers to ossification of the alar cartilage of the coffin bone. High ringbone refers to osteoarthritis of the proximal interphalangeal (pastern) joint. Osselets are inflammation of the periosteum on the dorsal distal epiphyseal surface of the third metacarpal bone and fetlock joint. Thoroughpin is the term for effusion of the tarsal sheath (sheath of the deep digital flexor).

Question 70

A 12 yr old mare presents for infertility and abnormal sexual behavior. On rectal palpation one ovary feels large and multicystic and the other feels very small. What is the most likely diagnosis?
a. Granulosa-thecal cell tumor
b. Ovarian hematoma
c. Cystic ovarian follicles
d. Ovaritis

Answer 70

Granulosa-thecal cell tumor; the clinical signs and palpation findings are both consistent with this diagnosis. The other choices listed may create a palable ovarian mass, but would not caause atrophy of the contralateral ovary and should not cause infertility.

Question 71

What breed is predisposed to development of recurrent uveitis and equine night blindness?
a. Arabian
b. Quarterhorse
c. Thoroughbred
d. Appaloosa

Answer 71

Appaloosa; equine night blindness is a congenital disease that is bilateral and nonprogressive, wherein horses have variable degrees of decreased vision in the daark. Recurrent uveitis is a very important condition in the horse and is actually the most common cause of blindness in the horse. Appaloosas are overrepresented, but the disease can occur in any breed. It is thought to be related to certain paathogens including Leptospira, Onchocerca, Toxoplasma, Brucella, and other infections, but these relationships are poorly characterized. Affected horses have recurrent bouts of inflammation, and each episode causes progressively worsening intraocular damage. The condition is sometimes referred to as moon blindness.

Question 72

What percentage of a horse’s dry matter intake should be protein for an adult horse with maintenance requirements?
a. 12%
b. 24%
c. 18%
d. 30%
e. 6%

Answer 72

12%; a horse requires about 1.3g of protein per kilogram body weight or about 40g of protein per 1000 calories. This corresponds to about 12% of dry matter intake. Obviously, other factors play some role, including the quality of the protein source. /in general, excess protein does not cause horses any health problems, but it can be an unnecessary expense for owners. Too little protein can result in malnutrition problems.

Question 73

What is the causative agent of equine protozoal myeloencephalitis?
a. Sarcocystis neurona
b. EHV-1
c. Neospora caninum
d. Toxoplasma gondii

Answer 73

Sarcocystis neurona; clinical signs of the disease vary in that they may be focal, multifocal, or diffuse in nature. One may observe focal muscle atrophy, and a neurologic exam may show ataxia and incoordination of all four limbs. However, you may only see one limb affected also. Muscle atrophy is most commonly seen in the quadriceps and gluteal regions of the hindlimbs. Horses may also have brainstem involvement and therefore exhibit a head tilt, facial paralysis, circling, and acute recumbency. Neospora caninum has recently been found as a cause of abortion in cattle. Toxoplasmosis can result in abortion and stillbirth in sheep. Other clinical sings seen with Toxoplasma gondii include diarrhea, cough, dyspnea, seizures, chorioretinitis, meningoencephalomyelitis, and myositis. Animals affected are usually immunocompromised and usually include young kittens, pigs, and dogs. EHV-1 is mainly recognized for resulting in respiratory disease and sometimes may cause abortion and infrequently neurologic disease.

Question 74

Which is NOT a manifestation of Mare Reproductive Loss Syndrome (MRLS)?
a. fetal or neonatal hemoabdomen
b. early fetal loss
c. late-term abortion
d. neonatal foal deaths
e. fibrinous pericarditis

Answer 74

fetal or neonatal hemoabdomen; all other choices listed were potential disease manifestations of MRLS. The exact pathogenesis of MRLS is still unknown, but the presence of eastern tent catipillars was strongly associated with the disease.

Question 75

Which test is used to diagnose a Corynebacterium pseudotuberculosis infection with internal abscesses in horses?
a. Coggin’s test
b. Zinc sulfate turbidity test
c. Synergistic hemolysis inhibition test
d. KOH test

Answer 75

Synergistic hemolysis inhibition test; other clinicopathologic data that would support an internal abscess would include leukocytosis, hyperfibrinogenemia and hyperglobulinemia. A KOH test is used to diagnose dermatophytes. The zinc sulfate turbidity test evaluates for failure of passive transfer. The Coggin’s test is for equine infectious anemia.

Question 76

A 9 day old foal is experiencing mild diarrhea. What is the most likely diagnosis?
a. Clostridium perfringens
b. Rhodococcus equi
c. Foal heat diarrhea
d. Lactose intolerance

Answer 76

Foal heat diarrhea; foal heat diarrhea is mainly seen at the age of 7-14 days and is usually very mild in nature. Rhodococcus equi will result in diarrhea in foals that are between ages 1-4 months, but this organism also causes respiratory disease. Clostridium perfringens Types A, B, C will usually result in an acute to peracute diarrhea in foals, leaving most of them dead in 48 hours if treatment is not instituted.

Question 77

A 26 year old horse presents for evaluation of increased thirst and urination. On exam, the horse has long curly hair which has developed in the past 6-9 months. Which diagnostic test would be most useful in confirming the diagnosis?
a. Serum total and free T4 levels
b. Water deprivation test
c. Blood glucose curve
d. Trypsin-like immunoreactivity
e. Plasma ACTH concentration

Answer 77

ACTH concentration; this is the typically presentation of equine pituitary pars intermedia dysfunction (PPID), sometimes referred to as Cushing’s disease. The disease is a progressive disorder of pituitary enlargement (adenoma). The condition usually affects horses greater than 15 years of age and may affect any breed but ponies and Morgan horses have increased incidence. The classic symptom which is highly suggestive of this condition is hirsutism which is the symptom of a long curly hair coat that does not shed properly. Other symptoms include PU, PD, laminitis, lethargy, excessive sweating or lactation, decreased muscle maass, infertility, and susceptibility to infections such as tooth root abscesses. Horses with PPID will have elevated plasma ACTH concentrations. The TRH stimulation test has also been suggested as a test for PPID.

Question 78

A 12 yr old horse was recently in a barn fire. The epidermis, dermis and adnexal (i.e. hair and sweat glands) structures are involved. What would the burn be classified as?
a. 1st degree burn
b. 3rd degree burn
c. 2nd degree burn
d. 4th degree burn

Answer 78

3rd degree burn; involves the epidermis, dermis, and adnexal structures. 1st degree involves the epidermis only. 2nd degree (partial thickness) involves the epidermis and may go down to deep dermis. 4th degree involves the total destruction of the skin, fat, fascia, bone and muscle.

Question 79

A 4 yr old Thoroughbred race horse presents for further evaluation one day after a race. Blood was noticed on the nostrils immediately after racing, the horse was previously healthy and although rats are in the baren, there is no documented exposure to rodenticides. What would be the best diagnostic test for diagnosing the most likely condition?
a. Proteins induced by vitamin K antagonism/absence (PIVKA)
b. Buccal mucosal bleeding time (BMBT)
c. Prothrombin time (PT)
d. Bronchoscopy

Answer 79

Bronchoscopy; the horse is most likely afflicted with exercise induced pulmonary hemorrhage (EIPH). The pathogenesis of this conditon is not entirely understood, but the condition is most commonly seen in racing horses. Bleeding may not always be evident and clinical signs include labored breathing, loss of speed during a race, and poor performance. Bronchoscopy of the ariway to visualize evidence of hemorrhage is the best diagnostic test in this list of possible answers. Cytologic examination of a BAL for evidence of hemorrhage is also another way to diagnose the condition. A PIVKA test is used in small animals to help diagnose exposure to rodenticides. A buccal mucosal bleeding test will test platelet function. PT evaluates the extrinsic and common pathways of the coagulation cascade.

Question 81

An 11 month old Paint gelding is presented for symmetric ataxia, weakness, and spasticity of all limbs. When walking, the hind limbs frequently interfere with one another. Based on signalment, history and PE, equine degenerative myeloencephalopathy (EDM) is suspected. What diagnostic test would support this suspicion?
a. Analysis of CSF demonstrating increased protein and normal nucleated cell count
b. no definitive antemortem diagnostic test is available; low serum vitamin E levels are suggestive of EDM
c. Cervical radiographs and measurement of the saggital ratio
d. electromyogram (EMG) demonstrating diffuse increase in motor unit aaction potentials (MUAP) and positive sharp waves
e. Biopsy of the sacrocaudalis dorsalis medialis muscle demonstrating muscle atrophy of type 1 muscle fibers

Answer 81

no definitive antemortem diagnostic test is available; low serum vitamin E levels are suggestive of EDM; it can only be confirmed through histopathologic examination of the spinal cord and brainstem and the identification of diffuse neuronal fiber degeneration of the white matter. However, many cases of EDM have been associated with low serum vitamin E concentrations; so measurement of vitamin E is suggestive of disease. The exact etiology of EDM is unknown, however, oxidative stress and damage to the CNS is a prominent theory.

Question 82

Which vaccine administered IM is most likely to cause a local reactionat the injection site of a horse?
a. Tetanus antitoxin
b. Rabies
c. Rhinopneumonitis
d. Strangles

Answer 82

Strangles; has been associated with a soft tissue reaction. More recently an intranasal vaccine has become availbale which is associated with local protection without any injection reaction.

Question 83

The owner of a horse farm in Southeastern US has seven ill horses after a wind storm knocked down tress and power poles. On exam they are lethargic, anorexic, dyspneic, icteric and have coffee-colored urine. Which is most likely the cause?
a. Red maple (Acer rubrum) poisoning
b. Equine infectious anemia
c. Copper poisoning
d. Rattlesnake bite
e. Babesiosis

Answer 83

Red maple; horses seem to eat the leaves when branches are available, the plant contains an unidentified hemolysin in wilted leaves. Ingestion can be fatal.

Question 84

A 4 yr old mare has bilateral swelling and drainage of the mandibular lymph nodes. Rectal temp is 101.8F. What is the most appropriate plan for this horse?
a. administer corticosteroids
b. administer penicillin
c. Inform the state veterinarian
d. culture the discharge for bacteria

Answer 84

culture the discharge for bacteria; the most likely diagnosis for this horse is equine strangles. Strangles most commonly affects younger horses (<5 yeaars), but can cause disease in any age horse. The etiologic agent of this disease is Streptococcus equi subsp. equi. Currently, the diagnostic test of choice to confirm equine strangles is bacterial culture, but recently there is a trend towards PCR testing on guttural pouch samples. While waiting for results, the horse should be separated from any other horses as strangles is highly contagious to other horses. Antibiotic therapy is controversial and thought to lengthen the course of disease rather than shorten it when given at this stage; also, it may possibly interefere with the natural immunity acquired from natural infection. Don’t forget to report positive caases of S. equi to the state veterinarian.

Question 85

A horse ranch has an ongoing problem with Streptococcal infections (Streptococcus equi subsp. equi). On endoscopy, there are several hard, smooth, stone-like structures within the guttural pouch. What is the most important intervention?
a. initiate a 1 month course of oral itraconazole
b. initiate a 1 month course of IM penicillin G
c. remove the objects and thoroughly flush the guttural pouches
d. no action is needed

Answer 85

remove the objects and thoroughly flush the guttural pouches; these objects are chondroids which are hardened pus filled concretions with bacteria. They most commonly occur when horses develop guttural pouch empyema which is an accumulation of purulent exudate in the guttural pouch due to mucosal infection or drainage from the retropharyngeal lymph nodes from Streptococcus equi subsp. equi. The persistence of pus provides refuge for the bacteria and allows for continued bacterial shedding. When exudate persists, it can become increasingly dense, forming solidified concretions that are difficult to extract and serve as a source for continued prolonged shedding of the organism. To reduce shedding and transmission the chondroids should be removed and the guttural pouch should be flushed with Penicillin G. In addition, these horses should be treated with Penicillin G IM for 7 days and isolated for 30 days and then retested with 3 consecutive series of nsopharyngeal swabs and culture.

Question 86

A 4 month old male Arabian presents with a one-week history of ataxia, hypometria, conscious proprioceptive deficits, and generalized weakness. On PE, there is no muscle atrophy or cranial nerve deficits and normal mentation. Additionally the temp is 100.2F. Which is not likely based on the clinical signs?
a. Cerebellar abiotrophy
b. cervical vertebral stenotic myelopathy
c. equine degenerative myeloencephalopathy
d. occipito-atlanto-axial malformation (OAAM)

Answer 86

Cerebellar abiotrophy; the cerebellum is responsible for the coordination and regulation of range, rate and strength of movement along with balance and posture. Clinical signs associated with cerebellar disease include intention tremors, hypermetria, hypometria, and ataxia. In addition, weakness is not observed with cerebellar abiotrophy. Mentation will be normal if the disease is strictly confined to the cerebellum. The key clinical sign not observed in this question is intention tremors. The clinical signs and presentation are definitely compatible with equine degenerative myeloencephalopathy, cervical vertebral myelopathy, and occipito-atlanto-axial malformation (OAAM). CT is needed to rule in or rule out cervical vertebral myelopathy and OAAM. OAAM is relatively rare, but is most requently observed in Arabian foals. These foals may be born dead, or may develop ataxia at several months of age. Histopathologic examination is the only way to definitively diagnose equine degenerative myeloencephalopathy.

Question 87

What is the preferred treatment for a saacroiliac luxation?
a. closed reduction and an Ehmer sling
b. open reduction and an Anderson sling
c. total hip arthroplasty
d. supportive care

Answer 87

supportive care; sacroiliac luxations in horses are generally considered untreatable. The condition will often stabilize with time and supportive care with rest and NSAIDs. Some horses may return to their previous level of activity or competitiveness but most have residual limitation. Reduction is not typically an option. Total hip arthroplasty has been reported in horses but is typically reserved for severely injured horses that do not improve with supportive care.

Question 88

Which neurologic disease has been associated with a deficiency in Vitamin E?
a. Cerebellar abiotrophy
b. Dandy-Walker syndrome
c. Cervical vertebral stenotic myelopathy
d. Equine degenerative myeloencephalopathy

Answer 88

Equine degenerative myeloencephalopathy; Dandy walker syndrome is a rare conditon seen in Arabian and Thoroughbred foals which results in a midline defect of the cerebellum and cystic dilation of the fourth ventricle. The pathogenesis of cerebellar abiotrophy still remains unknown, although genetic, toxic and infectious causes have all been incriminated. Cervical vertebral stenotic myelopathy is a developmental disease which is not associated with vitamin E deficiency. The disease results in either continuous or intermittent compression of the spinal cord at the cervical region. Equine degenerative myeloencephalopathy is the conditon recently associated with vitamin E deficiency. Clinical signs are usually in the form of a wide-based stance, conscious proprioceptive deficits, ataxia, paresis, and spasticity, which is worse in the hindlimbs.

Question 89

A 3 yr old mare is presented for multifocal, round, crusty lesions on her ventral abdomen, which are not particulaarly pruritic. There have been an increased number of flies around the mare and nearby cattle. What is most likely the diagnosis?
a. culicoides hypersensitivity
b. sarcoptes scabei equi
c. haemotobia irritans
d. dermatophytosis

Answer 89

haemotobia irritans; this fly is commonly known as the horn fly it causes ventral midline dermatitis as described. They are often found around the horns, back and sides of cattle on cooler days and will affect the ventral abdomen on hot sunny days. Horn flies feed on blood and cause great economic losses in cattle. It can also serve as an intermediate host to Stephanofilaria stilesi, a filarial parasite that causes plaque lesions on the ventrum of cattle. Treatment and control of flies is relatively easy with insecticide sprays, dust bags, or insecticide feed additives. Sarcoptes scabei infections and Culicoides hypersensitivity are extrememly pruritic. Dermatophytosis is a good differential, but Haematobia is a better choice since the horses are affected by flies and housed near cattle.

Question 90

A 6 month old colt has a 5 day history of lethargy, intermittent diarrhea, weight loss, and ventral edema. PCV = 30% (28-42%) and TP 3.2 g/dL (6.8-8.2 g/dL). Abdominal ultrasound demonstrates thickening of the small intestinal wall. What is the most likely diagnosis?
a. intermittent jejunal intussusception
b. salmonella infection
c. lawsonia intracellularis infection
d. clostridium difficile enteritis

Answer 90

lawsonia intracellularis infection; not as commonly as in pigs, but it can infect horses. Similar to pigs, the infection usually involves weanling age horses and causes thickening of the small intestine and hypoproteinemia. The low protein is commonly observed as ventral edema clinically. Both Clostridium and Salmonella can cause diarrhea at any age but are not as commonly associaated with ventral edema.

Question 91

What autosomal dominant trait causes hyperkalemic periodic paralysis (HYPP)?
a. defect in voltage-dependent magnesium channels
b. defect in voltage-dependent calcium channels
c. defect in voltage-dependent sodium channels
d. defect in voltage-dependent potassium channels

Answer 91

defect in voltage-dependent sodium channels; in this disease, a population of sodium channels fail to inactivate and remain open. This, in urn, results in depolarization of the muscle membrane (closer to threshold) and hyperexcitability of the muscle. With futher depolarization, the muscle cell membrane becomes unexcitable and paralysis may occur. The reason for the hyperkalemia is paartially because of the movement of potassium out of the muscle cell as the myocyte repolarizes.

Question 92

A 7 month old colt has reared up and subsequently flipped over backwaards and hit his head on the cement drive. Based on the image, trauma likely occurred to which structure?
a. fracture to the basilar bones (basisphenoid/basioccipital)
b. fracture to the occipital bone
c. fracture to the hyoid bone
d. fracture to the frontal bone

Answer 92

fracture to the basilar bones (basisphenoid/basioccipital); left head tilt, dropping the left ear and deviation of the muzzle to the right are present in the image. These clinical signs are suggestive of cranial nerve VII and VIII injury, which are located in close proximity tot he basilar bones. The most likely fracture resulting in these lesions is fracture of the basilar bones, a common form of traumatic nerve injury in the foal.

Question 93

How often should tetanus antitoxin be administered to a horse?
a. at 3, 4, and 12 months of age, then annually
b. to all foals and after any wound
c. annually and 1 month prior to foaling
d. after surgery or a wound in an unvaccinated horse

Answer 93

after surgery or a wound in an unvaccinated horse; the antitoxin should be used only when needed due to the risk of causing serum sickness or Theiler’s disease. The toxoid should be given at 3, 4, and 12 months then anually and 1-2 months prior to foaling. It should also be repeated after wounds or surgery in a vaccinated horse. The antitoxin should be reserved for horses that are unvaccinated and receive surgery or a wound. It should also be given to foals from an unvaccinated dam soon after birth. It can also be given in a horse showing signs of tetanus.

Question 94

Which of these control measures would be LEAST effective for reducing Culicoides hypersensitivity in horses?
a. placement of ceiling fans
b. insect repellants
c. pyrethrins
d. corticosteroid therapy
e. antihistamines

Answer 94

Antihistamines; in general antihistamines are ineffective at reducing clinical signs associated with cutaneous hypersensitivity diseases in horses. The most important aspect of therapy is reduction of insect exposure. This can be achieved by moving horses away from breeding habitats, frequent bathing, and application of insect repellents. Corticosteroid therapy is required for management of many horses. Short acting corticosteroids should be used first.

Question 95

A 3 yr old Appaloosa mare presents with progressive neurologic signs over the past 2 weeks. She has an ataxic, spastic gait, knuckling on the left legs. She also has a right-sided head tilt and atrophy of the temporal and masseter muscles on the right side. There is muscle atrophy of the left gluteal muscles. Based on the most likely diagnosis what is the prognosis for this horse with treatment?
a. most horses recover completely with treatment but a small subset of horses relapse when treatment is discontinued
b. treatment will likely prevent further progression of the disease but the existing deficits are unlikely to improve. c. most horses improve with treatment but relatively few make a complete recovery
d. it is unlikely that treatment will significantly delay the progression of the disease

Answer 95

most horses improve with treatment but relatively few make a complete recovery; this is a caase of EPM. The 3 A’s: asymmetry, ataxia and atrophy are the key findings. The onset of clinical signs are frequently gradual but rapid progression is seen in some cases. The prognosis for horses with EPM is often described as variable. Studies show that about 70% of treated horses will improve but only up to 25% recover completely and perform normally. In addition, a subset (5-20%) of horses may improve while undergoing treatment but then relapse when treatment is discontinued. It is unclear whether relapse represents reemergence or persistence of resistant paarasite or re-exposure.

Question 96

A 9 yr old Thoroughbred mare presents for intermittent left-sided epistaxis over several months. There is no history of trauma. The horse has mildly increased respiratory effort on PE. Which is most likely to cause recurrent, intermittent, unilateral epistaxis in this animal?
a. Warfarin Toxicity
b. Exercise induced pulmonary hemorrhage
c. Purpura hemorrhagica
d. Ethmoid hematoma

Answer 96

Ethmoid hematoma; this is a progressive and locally destructive mass that resembles a tumor but is not truly neoplastic. The most common clinical sign is mild, persistent, spontaneous, intermittent epistaxis that can be unilateral or bilateral. Warfarin is not as likely in this horse due to the recurrent nature of the condition and the fact that it is unilateral. Exercise-induced pulmonary hemorrhage actually causes epistaxis only about 10% of the time. Also, since the bleeding is pulmonary in origin, the epistaxis would likely be bilateral. Epistaxis with this condition also occurs immediately after exercise, which was not reported in this horse. Purpura hemorrhagica is a vasculitis that results from a type III immune complex hypersensitivity after a streptococcus equi infection. This leads to vasculitis and the main clinical sign are petechia and ecchymoses of mucous membranes.

Question 97

If a patient exhibits a head tilt to the right, circling to the right and has normal strength, what type of lesion does it have?
a. Right side - peripheral vestibular dysfunction
b. Left side - peripheral vestibular dysfunction
c. Left side - central vestibular dysfunction
d. Right side - central vestibular dysfunction

Answer 97

Right side - peripheral vestibular dysfunction; peripheral vestibular dysfunction causes signs of head tilt, nystagmus, circling and asymmetric ataxia with preservation of strength. The head tilt towaard the affected side as in circling towards the lesion. Comparatively, central vestibular disease has similar clinical signs but general conscious proprioceptive deficits, weakness and cranial nerve deficits may also be present along with depression.

Question 98

Treatment of stringhalt in a horse involves which of the following?
a. Tenectomy of the lateral digital extensor
b. suspensory ligament desmotomy
c. splinting the leg in extension
d. palmar digital neurectomy

Answer 98

Tenectomy of the lateral digital extensor; stringhalt is a myoclonic disease affecting one or both pelvic limbs. It causes spasmodic hyperflexion of the leg. The etiology is unknown but sweet pea poisoning is thought to be associated with the condition. Diagnosis is based on clinical signs, but electromyography can be used to confirm the diagnosis. Treatment invovles tenectomy of the lateral digital extensor; however, not all cases respond to treatment.

Question 99

Which is NOT hepatotoxic to horses?
a. Aphanizomenon
b. Microcystis
c. Anabaena
d. Canthaaridin

Answer 99

Cantharidin; aka blister beetle toxicity results in endotoxic shock and renal failure. Horses affected may be found dead, colicking or in cardiovascular shock. Vesicles may form in the mouth and tongue, and if the animal lives long enough, you can expect to see watery feces. Renal tubular damage will be profound, and you will probably observe cardiac arrhythmias. The blister beetle may become processed with hay or pellets; the horses then eat the toxic part of the beetle by accident. Anabaena, Aphanizomenon and Microcystis are all blue-green algae that cause hepatotoxicity.

Question 100

A 14 yr old Saddlebred gelding with an acute onset (24 hours) history of profuse watery diarrhea. PE findings: HR = 65bpm, RR = 28 brpm, temp = 102.7F. The horse is lethargic and not willing to eat. What is the blood gas showing?
a. the horse is hypoxemic
b. metabolic acidemia with respiratory compensation
c. respiratory acidemia with metabolic compensation
d. respiratory acidemia with metabolic compensation
e. metabolic acidemia without respiratory compensation

Answer 100

metabolic acidemia with respiratory compensation; the pH is low which suggests acidemia, the HCO3 is low which suggests the cause of acidemia; the PCO2 is low and respiratory rate is high which suggests respiratory compensation.

Question 101

An ECG was performed on a Thoroughbred mare which shows an increase in the P-R interval followed by occasional P waves that are not followed by a QRS-T complex. What does this finding mean?
a. this horse is predisposed to developing an electrical mechanical disassociation and needs further diagnostics before purchasing
b. This is a first-degree atrioventricular block and should be treated immediately with quinidine
c. this is a second-degree atrioventricular block, which is commonly seen in athletic horses
d. this mare most likely has ventricular septal defect and should not be purchased

Answer 101

this is a second-degree atrioventricular block, which is commonly seen in athletic horses; first-degree and second-degree blocks are considered variations of normal in the horse aand are usually associated with high vagal tone. They are not predisposed to electrical-mechanical disassociation. An electrical rhythm is an ineffective method in trying to determine if there is a ventricular septal defect. If such a defect is suspected, the best way to evaluate the horse is by performing a cardiac ultrasound.

Question 102

A club foot in a horse is a result of __________.
a. superficial digital tendon rupture
b. deep digital flexor tendon rupture
c. superficial digital tendon contracture
d. deep digital flexor tendon contracture

Answer 102

deep digital flexor tendon contracture; there are multiple causes for flexural deformity of the distal interphalangeal joint (deep digital flexure contracture) included rapid bone growth, excessive feeding, faulty nutrition and lack of exercise. The distal check ligament controls the stretch in the long tendon of the deep digital flexor. If this becomes functionally too short, flexion of the interphalangeal joint occurs, resulting in a club foot. If medical therapy is not successful, surgical correction is recommended.

Question 103

What is the treatment of choice for a carpal hygroma in a horse?
a. carpal arthrodesis
b. aspiration of fluid from the hygroma
c. local injection of corticosteroids
d. surgical exploration and drain placement
e. systemic antibiotics

Answer 103

surgical exploration and drain placement; a hygroma is a fluid filled swelling at the carpus, usually seen from repeated trauma leading to local bursitis. Horses are usually not lame from this condition, but have restricted range of motion of the joint. Simply aspirating the fluid and/or injecting corticosteroids is rarely effective and the swelling usually recurs. Surgicial excision of the bursal lining may be indicated when recurrence is a problem.

Question 104

Which of these nerve blocks is used to examine the eyes of a horse?
a. oculomotor nerve block
b. auriculopalpebral nerve block
c. trigeminal nerve block
d. corneal nerve block

Answer 104

auriculopalpebral nerve block; blocking this branch of cranial nerve VII (facial nerve) disrupts the motor innervation to the orbicularis oculi, which is the muscle that closes the eye. In the horse, this muscle is very strong and can prevent a thorough ocular exam. To perform this block, lidocaine is injected subcutaneously at the caudal aspect of the zygomatic arch where the nerve is palpable. Because this is a motor nerve, the eye will not be able to close as well, but there is no anesthesia of the tissue.

Question 105

Two mares present for crusting dermal lesions on their dorsum and pasterns. The lesions are “paintbrush” like lesions and have purulent material exudating from them. A direct smear of the lesion shows branching, filamentous, gram positive bacteria. What is the most likely diagnosis?
a. Sarcoid
b. Corynebacterium pseudotuberculosis
c. dermatophytosis
d. onchocerciasis
e. dermatophilosis

Answer 105

Dermatophilosis; dermatophilus congolensis is a gram positive, non-acid fast, facultative anaerobic actinomycete. It causes a crusting dermatitis in large animals when there is high moisture on the skin as well as mechanical irritation. Horses with long, wet haircoats are often affected. Lesions are commonly on the dorsum and pasterns of horses and are classically described as paintbrush lesions. It can be diagnosed with a direct smear preparation. Treatment includes keeping the haircoat clean and dry and penicillins if the lesions are severe. Lesions typically heal rapidly.

Question 106

A horse presented for severe colic. At surgery, there is an infarction of the mesenteric artery. What organism is associated with this lesion?
a. Parascaris equorum
b. Strongyloides westeri
c. Draschia megastoma
d. Dictyocaulus arnfieldi
e. Strongylus vulgaris

Answer 106

Strongylus vulgaris; migration of the larvae of strongylus vulgaris and the corresponding immune response can result in thrombosis of the cranial or anterior mesenteric arteries leading to colic and infarction of the bowel. Parascaris equorum causes colic in foals by causing intestinal impaction. Strongyloides westeri is a cause of foal heat diarrhea and can migrate through the lung causing damage. Dictyocaulus is a lungworm. Draschia megastoma is another migrating parasite that can caause focal granulomas in the lung.

Question 107

Which of the following stallions should definitely not be used for breeding?
a. A stallion with 180 degree rotation of the testicle
b. A stallion with a positive bacterial culture from a pre-ejaculate swab
c. A stallion with previous infection with Taylorella equigenitalis
d. A stallion with a previous infection with coital exanthema

Answer 107

A stallion with previous infection with Taylorella equigenitalis; this organism is thought to be eradicated in the US, but is the causative agent of contagious equine metritis, which can lead to infertility (there is usually no clinically apparent disease in the stallion). It is okay to breed a stallion with a history of coital exanthema (Equine Herpesvirus-3) as long as all lesions are cleared. A 180 degree rotation of the testicle is common and of no clinical significance as is a positive bacterial culture from a pre-ejaculate swab; however, heavy growth of Pseudomonas or Klebsiella may make you think twice, as they can be associated with causing endometritis in mares.

Question 108

Consumption of yellow star thistle results in which lesion?
a. Nigropallidal encephalomalacia
b. Destruction of the lateral and medial geniculate nucleus
c. Leukoencephalomalacia of the reticular system
d. Destruction of the pons

Answer 108

Nigropallidal encephalomalacia; consumption of the yellow star thistle destroys the globus pallidus and the substantia nigra. These lesions will result in a characteristic dysphagia.

Question 109

A 4 yr old Thoroughbred has intermittent epistaxis. What is the most likely diagnosis?
a. nasal adenocarcinoma
b. exercise induced pulmonary hemorrhage
c. guttural pouch mycosis
d. ethmoid hematoma

Answer 109

ethmoid hematoma; these lesions are angiomatous masses that originate from the mucosal lining of the ethmoid conchae or walls of the maxillary or frontal sinus. Guttural pouch mycosis also can result in epistaxis, but the blood originates from the lungs. In the radiograph provided, notice the smooth, well-defined soft tissue mass in the sinus region of this horse. No osseous changes or fluid lines are apparant. In this particular case (ethmoid hematoma), the soft tissue mass is actually dorsal to the ethmoid turbinates (ethmoids are normal appearance in this case). Upon surgical removal, a definitive diagnosis of ethmoid hematoma was confirmed.

Question 110

A 4 month old foal has clinical evidence of weight loss, fever and tachypnea. What is the best diagnosis based on the clinical signs and radiograph?
a. pulmonary abscess
b. congestive heart failure
c. pulmonary aneurism
d. pulmonary carcinoma
e. rhinopneumonitis pneumonia

Answer 110

pulmonary abscess; the two horizontal lines represent fluid or pus capped by gas within cavitary lesions. In foals, this occurs most frequently with Rhodococcus equi pneumonia.

Question 111

A 4 yr old horse presents with mucopurulent nasal discharge, lethargy, and depression. On PE, the horse has a temp of 103.7F, markedly enlarged mandibular and retropharyngeal lymph nodes. Strangles is suspected. What would be expected upon aspiration of an enlarged lymph node?
a. fungal hyphae and granulomatous inflammation
b. granulomatous inflammation and gram negative cocci
c. reactive lymphocytes and macrophages with no bacteria
d. purulent inflammation and gram negative rods with large capsules
e. purulent inflammation and gram positive cocci with large capsules

Answer 111

purulent inflammation and gram negative rods with large capsules; the causative agent of strangles is streptococcus equi ssp. equi, a gram positive cocci with a large capsule. It causes enlargement and suppurative abscessation of the mandibular and retropharyngeal lymph nodes.

Question 112

What is a horse’s maintenance fluid rate?
a. 60ml/kg/day
b. 45ml/kg/day
c. 90ml/kg/day
d. 100ml/kg/day

Answer 112

60ml/kg/day

Question 113

A horse is found to be approximately 7% dehydrated after a several day trail ride. Assuming there are no other ongoing losses and the horse weighs 500kg how many liters will need to be given to the horse over a 24 hour period to correct the deficit and account for maintenance requirements?
a. 75L
b. 65L
c. 40L
d. 35L
e. 125L

Answer 113

65L; the deficit is 35L
(deficit x BW ) –> 0.07 x 500 = 35L
maintenance is 60ml/kg/day = 30,000ml/day =30L
30L + 35L = 65L

Question 114

A 6 yr old race horse has been experiencing decreased performance. On auscultation, the heart rate is slow at 16bpm with an irregular rhythm consisting of occasional dropped beats. An ECG confirms the presence of a second degree atrioventricular block. What should be told to the owner?
a. This conduction finding is common in racehorses and is unlikely to contribute to poor performance
b. This conduction finding is a common cause of poor performance and is not treatable; the horse should be retired
c. This conduction finding is a common cause of poor perfromance and is usually effectively treated by quinidine
d. This conduction finding is a life-threatening abnormality and placement of a pacemaker is indicated
e. This conduction finding likely indicates serious underlying pathology in the heart and further diaagnostic tests are needed

Answer 114

This conduction finding is common in racehorses and is unlikely to contribute to poor performance; second-degree atrioventricular block is commonly seen in athletic horses. First-degree and second-degree blocks are considered variations of normal in the horse and are usually associated with high vagal tone. Horses with second-degree atrioventricular block are NOT predisposed to electrical-mechanical disassociation. This is not a cause of poor perfromance or a concern in horses because high vagal tone is overcome by sympathetic tone during exercise.

Question 115

In what cell of the horse does Anaplasma phagocytophilum survive in?
a. Monocyte
b. Erythrocyte
c. Myocyte
d. Neutrophil
e. Hepatocyte

Answer 115

Neutrophil; anaplasma phagocytophilum causes equine granulocytic ehrlichiosis. It can survive in host neutrophils and eosinophils and can be seen on a blood smear during the acute phase of disease. This in contrast to Neorickettsia risticii, the causative agent of Potomac Horse Fever, which survives in monocytes and is rarely found in a blood smear. Clinical signs of Anaplasma phagocytophilum include depression, limb edema, petechiation, icterus, and ataxia and is commonly treated with tetracyclines.