Horses II Flashcards
At what age does Galvayne’s groove begin to appear in the horse?
- 5 years
- 15 years
- 9 years
- 6 months
Answer: 9 years
Explanation
The correct answer is 9 years. This is useful for the purposes of aging horses. It is a longitudinal groove noted on 13. 11 erupts at 2.5 years, 12 erupts at 3.5 years, and 13 at 4.5 years. The canine tooth erupts at 5 years. The cup from 11 disappears at 6 years, 12 at 7 years, and 13 at 8 years. Galvayne’s groove is half way down the tooth at 15 years and then completely down at 20 years of age.
Which of the following fractures in an adult horse has a grave prognosis for return to function?
- P3 (distal phalanx)
- Ulna
- Tibia
- P1 (proximal phalanx)
Answer: Tibia
Explanation
The correct answer is tibia. Fractures of the tibia are usually non-reconstructable comminuted fractures. Due to the lack of soft tissue coverage, these fractures are highly susceptible to infection, which makes them poor candidates for recovery. As long as the articular surface of P3 is not involved, P3 fractures carry a good prognosis. Most P1 fractures are fairly easily repaired with lag screws as long as they are not comminuted. Ulnar fractures are usually treated with bone plates and have a good prognosis, with about 70% of horses returning to function.
A 2-year old Quarter Horse presents for intermittent muscle fasciculation followed by weakness. What condition should you suspect?
- Grass tetany
- Myotonia
- Stringhalt
- Hyperkalemic periodic paralysis
- Tetanus
Answer: Hyperkalemic periodic paralysis
Explanation
The correct answer is hyperkalemic periodic paralysis (HYPP). HYPP is seen in Quarter Horses due to a point mutation in a key part of a skeletal muscle sodium channel subunit. This results in elevation of the resting membrane potential to increase the likelihood of depolarizing. Excess concentrations of potassium can result in failure of the sodium channels to inactivate. Therefore, treatment is directed at decreasing dietary potassium.
***PowerLecture: Musculoskeletal Disorders
Which condition is associated with apical fracture of the proximal sesamoid bones, avulsion fractures of the palmar aspect of the third metacarpal bone, or fractures of the distal third of the small metacarpal bones in horses?
- Suspensory ligament desmitis
- Superficial digital flexor tendonitis
- Sweeney
- Deep digital flexor tendonitis
Answer: Suspensory ligament desmitis
Explanation
The correct answer is suspensory ligament desmitis. The presence of these fractures would indicate ultrasonography as the next diagnostic test to evaluate for suspensory ligament desmitis, since these fractures are present with this condition 25% of the time.
A 9-day old foal is experiencing mild diarrhea. What is the most likely diagnosis?
- Clostridium perfringens
- Lactose intolerance
- Foal heat diarrhea
- Rhodococcus equi
Answer: Foal heat diarrhea
Explanation
The correct answer is foal heat diarrhea. Although any of these answers could be correct, sometimes this is all you have to go on for some exam questions. To answer this question you need to know at what time periods foals get what diarrhea and the severity.
Foal heat diarrhea is mainly seen at the age of 7-14 days and is usually very mild in nature, making this the best answer choice.
Rhodococcus equi will result in diarrhea in foals that are between the ages of 1-4 months; however, remember that this organism primarily causes respiratory disease, so look for that too.
Clostridium perfringens Types A, B, and 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.
Primary lactose intolerance is rare in foals.
***PowerLecture: Foal Diarrhea
A 9-day old foal is experiencing mild diarrhea. What is the most likely diagnosis?
- Clostridium perfringens
- Lactose intolerance
- Foal heat diarrhea
- Rhodococcus equi
Answer: Foal heat diarrhea
Explanation
The correct answer is foal heat diarrhea. Although any of these answers could be correct, sometimes this is all you have to go on for some exam questions. To answer this question you need to know at what time periods foals get what diarrhea and the severity.
Foal heat diarrhea is mainly seen at the age of 7-14 days and is usually very mild in nature, making this the best answer choice.
Rhodococcus equi will result in diarrhea in foals that are between the ages of 1-4 months; however, remember that this organism primarily causes respiratory disease, so look for that too.
Clostridium perfringens Types A, B, and 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.
Primary lactose intolerance is rare in foals.
***PowerLecture: Foal Diarrhea
What is the causative agent of Tyzzer’s disease?
- Clostridium botulinum
- Clostridium perfringens
- Clostridium chauvoei
- Clostridium piliforme
- Clostridium difficile
Answer: Clostridium piliforme
Explanation
The correct answer is Clostridium piliforme. This is a motile, filamentous, gram negative, spore forming bacterium. Of note, all Clostridia are categorized as gram positive organisms with the exception of Clostridium piliforme, which is gram negative (yes, Microbiology is confusing). Clinical signs associated with Tyzzer’s include depression, anorexia, coma, convulsions, and jaundice. Horses between 6 days and 6 weeks of age are affected; however, most are affected at 1-2 weeks. Affected foals will have elevated liver enzymes, marked hypoglycemia, and acidosis.
The syndrome of right dorsal colitis in horses is associated with which predisposing factor?
- Parasitic damage of the intestinal arteries (i.e. right colic artery)
- Colitis as a result of Salmonella infection
- Administration of beta-lactam antimicrobials at excessive dosages (i.e. Ceftofur)
- Administration of non-steroidal anti-inflammatory drugs (i.e. phenylbutazone)
Answer: Administration of non-steroidal anti-inflammatory drugs (i.e. phenylbutazone)
Explanation
Right dorsal colitis is associated with the administration of NSAIDs. The dose of NSAIDs may be within the normal range or higher than recommended dosages. This disease is also usually associated with more chronic administration of NSAIDs (>1 week). Some horses may be more sensitive to NSAIDs, with clinical signs such as inappetence, intermittent colic, and hypoproteinemia commonly observed.
***PowerLecture: Gastrointestinal Disorders
A mare has aborted due to an equine herpesvirus-1 infection. What would you tell the owner about her future as a breeding horse?
- Future breeding are still possible, and the mare can still produce healthy foals in the future.
- She will be latently infected and should not breed this mare again.
- She should be treated with oral acyclovir for at least 3 weeks to avoid future abortions.
- The mare can maintain a future pregnancy, but the fetus is likely to be born with equine herpesvirus with a low chance of survival.
Answer: Future breeding are still possible, and the mare can still produce healthy foals in the future.
Explanation
The correct answer is future breeding possibilities should be unaffected, but the mare likely has a latent herpesvirus infection. Vaccination of the mare during her next pregnancy against EHV (gestational months 5, 7 and 9) may help lessen the chance of abortion in the future. Acyclovir, while active against herpesvirus is not indicated (and is not well absorbed orally anyway).
A horse presents with urticaria, edema of the extremities, petechiation of the mucous membranes, and a stiff gait. On physical exam, you suspect the horse to have purpura hemorrhagica. Which of these abnormalities is associated with purpura hemorrhagica?
- Anemia
- Prolonged PT and PTT
- Thrombocytopenia
- Hypoproteinemia
Answer: Anemia
Explanation
The correct answer is anemia. Purpura hemorrhagica is a possible sequela of streptococcus equi infection exposure or vaccination. It develops from a Type Ill hypersensitivity resulting in immune complex deposition in blood vessel walls and vasculitis. Common clinical signs are as described in the question. This is a nonthrombocytopenic purpura (most horses will have a normal platelet count). Common findings include anemia, hyperproteinemia, hyperfibrinogenemia, hyperglobulinemia, and neutrophilia.
A 28 year old Paint stallion presents with an acute onset of colic. On presentation he has a rectal temperature of 99.8F (37.7 C), heart rate of 75 beats/min, respiratory rate of 24 breaths/min, and is pawing and trying to lie down. CRT is approximately 3.0 seconds, and mucous membranes are purple-red. Gastrointestinal sounds are completely absent, and gastric reflux yielded 18L of brown-to yellow-colored fluid. Peritoneal fluid analysis yielded a cloudy yellow fluid with a protein of 3.2 gm/dl and white blood cell count of 11,000/ul. Which of the following is a possible diagnosis?
- Strongylus vulgaris infestation
- Strangulating lipoma
- Right dorsal colon displacement
- Cecal volvulus
- Left dorsal colon displacement
Answer: Strangulating lipoma
Explanation
The correct answer is strangulating lipoma. Lipomas are a common cause of small intestinal obstruction in older horses. Typically, a section of the small intestine becomes intertwined with a pedunculated lipoma, resulting in obstruction and possible devitalization of the small intestine. Surgical correction is necessary to correct this problem. None of the other answer choices typically result in the clinical signs described, particularly gastric reflux. Left dorsal colon displacement typically have milder clinical signs, and the diagnosis can be made by rectal palpation and ultrasonography.
This neurologic disease has been associated with a deficiency in vitamin E.
- Cerebellar abiotrophy
- Cervical vertebral stenotic myelopathy
- Equine degenerative myeloencephalopathy
- Dandy-Walker syndrome
Answer: Equine degenerative myeloencephalopathy
Explanation
The correct answer is equine degenerative myeloencephalopathy.
Dandy-Walker syndrome is a rare condition 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 condition 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.
***PowerLecture: Neurologic Disorders
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?
- Small intestinal obstruction
- Ascarid impaction
- Nephrosplenic entrapment
- Salmonella
Answer: Small intestinal obstruction
Explanation
The correct answer is small intestinal obstruction. Both small intestinal obstruction and duodenitis-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 acute 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.
***PowerLecture: Gastrointestinal Disorders
A race horse that has been overworked for the past week presents for a stiff gait, lethargy, anorexia, and oliguria. What is the most likely diagnosis?
- Ischemic renal failure
- NSAID toxicity
- Pigment nephropathy
- Pyelonephritis
Answer: Pigment nephropathy
Explanation
The correct answer is pigment nephropathy. Pigment nephropathy occurs as a result of myositis (tying up), which this presentation is consistent with. Nephrosis and subsequent renal failure is caused by large amounts of myoglobin being filtered by the kidney. This usually occurs in horses that have been subjected to extreme conditions such that the animal breaks down a substantial amount of muscle. The same condition can occur with intravascular hemolysis. In this case, the hemoglobin pigment is the culprit. However, this scenario seems to be less common in the horse.
Alpha 2 receptor agonist drugs are routinely used for sedation of horses. Which of the following alpha 2 receptor agonists has the lowest receptor affinity and shortest duration of action?
- Xylazine
- Medetomidine
- Ketamine
- Detomidine
- Romifidine
Answer: Xylazine
Explanation
The correct answer is xylazine. Xylazine has the lowest receptor affinity, duration of action, and has the largest dose requirement of the alpha 2 agonists. Sedative effects of xylazine last for about 20 minutes. Sedative effects of detomidine typically last approximately 90 minutes; however, peak sedation is achieved for 10-20 minutes. Romifidine is similar to detomidine; however, the side effects are supposed to be decreased. Ketamine is a dissociative agent and not an alpha 2 agonist.
Which of these is not an expected lab finding in a horse with pituitary pars intermedia dysfunction (also known as Cushing’s disease)?
- Low urine specific gravity
- Stress leukogram
- Elevated alkaline phosphatase
- Hyperglycemia
Answer: Elevated alkaline phosphatase
Explanation
The correct answer is an elevated alkaline phosphatase. The horse, unlike the dog, does not have a steroid- induced isoenzyme of alkaline phosphatase. Hyperglycemia is common due to the counter-insulin effects of cortisol. Low urine specific gravity is a common feature of Cushing’s seen in dogs and horses and is the reason affected animals are polyuric and polydipsic. The stress leukogram (neutrophilia, lymphopenia) is due to the effects of cortisol as well.
A 2-year old Thoroughbred race horse presents for lameness evaluation. The trainer reports that the lameness has been slowly progressive over the past 3 weeks. You observe the horse walk and see a short, choppy gait in the front legs. There is swelling over the front of both fetlock joints and palpation and flexion of the fetlocks elicits pain. Radiographs show no evidence of new bone formation in the fetlock. You diagnose the horse with osselets (periostitis of the distal dorsal cannon bone). What is the best treatment recommendation?
- Deep digital flexor tenotomy
- Rest, phenylbutazone, and intra-articular injections of sodium hyaluronate
- Palmar digital neurectomy
- Arthrodesis of the fetlock
Answer: Rest, phenylbutazone, and intra-articular injections of sodium hyaluronate
Explanation
Cases of osselets that are caught before the development of osteoarthritis often respond completely to medical management consisting of rest, anti-inflammatories (such as phenylbutazone) and intra-articular injections of sodium hyaluronate or polysulfated glycosaminoglycans (Adequan).
Fetlock arthrodesis is reserved for more advanced fetlock injuries. Deep digital flexor tenotomy is used to treat certain cases of chronic laminitis. Palmar digital neurectomy is used to treat navicular disease and results in desensitization of the heel.
***PowerPage: Top 9 Equine Lameness
You are called to a small farm owned by an associate in South America, where you are on vacation with a friend. The associate has a few horses that you were going to ride, but they now have fevers and lesions on the tongue. You notice that a few of his pigs seem lethargic, are not eating, and have snout lesions. You check several and find they are febrile. Based on these findings, you tell your associate that his animals appear to have what disease?
- African horse sickness
- Vesicular stomatitis
- Foot and Mouth Disease
- Encephalomyocarditis virus
- African swine fever
Answer: Vesicular stomatitis
Explanation
Vesicular stomatitis is common in Central and South America and occasionally occurs in the southwestern USA. It is one of the few vesicular diseases that affects both horses and pigs (as well as cattle).
What is the most frequently observed side effect associated with acepromazine use in horses?
- Paraphimosis
- Hypotension
- Seizures
- Arrhythmias
Answer: Hypotension
Explanation
The correct answer is hypotension. Acepromazine will reliably cause hypotension. Acepromazine may cause paraphimosis in male horses, but this is not very common. However, because of this, many veterinarians will not use acepromazine on stallions. Acepromazine actually has anti-arrhythmogenic properties. Acepromazine does reduce the seizure threshold, but seizures are not as common as hypotension.
By what mechanism does Parascaris equorum typically cause colic in foals?
- Larval migration
- Intestinal impaction
- Thrombosis of the mesenteric artery
- Immune mediated hypersensitivity
Answer: Intestinal impaction
Explanation
The correct answer is intestinal impaction. In foals, a significant ascarid burden with Parascaris equorum can lead to intestinal impaction and associated colic.
Thrombosis of the mesenteric artery occurs with Strongylus vulgaris infestations.
Immune mediated hypersensitivities may occur in adult horses with Parascaris equorum infestations but is unlikely to be a significant cause of the morbidity seen in foals.
Larval migration can occur with Parascaris equorum but typically will affect the lungs or liver and this stage of the parasite does not lead to colic.
You are asked to evaluate some radiographs of the carpal bones of a newborn foal that may be premature. Upon examination of the radiographs what can you conclude (see picture)?
- The carpal bones are incompletely ossified, suggesting that the foal is premature
- The carpal bones are fully ossified, suggesting a full-term healthy foal
- The carpal bones are partially ossified, which is normal in a full-term healthy foal
- The carpal bones are lytic, suggesting septic arthritis in a newborn foal
Answer: The carpal bones are incompletely ossified, suggesting that the foal is premature
Explanation
The carpal bones are partially ossified in this radiograph. Normal ossification of the cartilage precursors in the carpus occurs in the last part of gestation. Therefore, incomplete ossification suggests that this foal was born prematurely. The carpal bones will ossify as the foal ages, but they can collapse with the weight of the foal placing pressure on the soft cartilage, which may result in misshapen carpal bones and chronic lameness.
A 2-year old Standardbred mare presents for alopecia, erythema, and crusting of the skin around the saddle region. A KOF (potassium hydroxide) preparation shows hyphae and arthroconidia. What is the best treatment option for this horse?
- Excision with wide margins
- Topical anti-fungals
- Oral ketoconazole
- Penicillin
- Cephalexin
Answer: Topical anti-fungals
Explanation
The correct answer is topical anti fungals. The horse in the question has dermatophytosis, or ringworm. Horses are most commonly affected with Trichophyton equinum, T mentagrophytes, and Microsporum gypseum. M canis, M equinum, and T verrucosum are also sometimes the causative agents. The disease typically causes alopecia and crusting around the saddle and girth regions. Diagnosis is made by dermatophyte test media (DTM) or visualization of the fungal elements on KOH preps. Topical azole antifungals are most useful in treating the disease. Systemic antifungals are expensive and have unproven efficacy. Antibiotics such as penicillin and cephalexin are not effective against fungus. Excision of the lesions is not necessary.
You are presented with a 5 year old gelding that stands with his left foreleg in the position shown, with dropped elbow and flexed carpus, fetlock, and digits. When he is walked, he drags the limb and is unable to advance the leg. The horse was placed in left lateral recumbency for a 4 hour surgical procedure to the guttural pouch yesterday. What is the correct diagnosis of his problem?
- Ulnar nerve paralysis
- Equine wobbler syndrome
- Brachial plexus tumor
- High radial nerve paralysis
- Equine dysautonomia
Answer: High radial nerve paralysis
Explanation
The radial nerve is susceptible to damage from pressure when a large animal lays on it without adequate padding and circulation for a prolonged period. The advent of warm water beds for padding this area has greatly decreased the incidence. Rapid and aggressive treatment and excellent nursing care can allow some animals with radial paralysis to recover.
A horse owner in Louisiana calls you frantically concerned that he has heard reports of African Horse Sickness in adjacent states and he wants to know what he can do to protect his horses. Which of the following is the best recommendation for preventing transmission of this disease?
- The owner should not travel to any of the states where the disease is present because the virus is transmitted by fomites and can survive for extended periods
- Institute strict arthropod control measures because the disease is transmitted primarily by Ixodes ticks
- Stable all horses in insect-proof housing, particularly at night because the disease is transmitted primarily by Culicoides flies
- Separate all horses from each other and all other animals because horses are most commonly infected by direct contact with infected animals
- Treat all horses with oxytetracycline because the etiologic agent is exquisitely sensitive to this antibiotic
Answer: Stable all horses in insect-proof housing, particularly at night because the disease is transmitted primarily by Culicoides flies
Explanation
African horse sickness (AHS) is a viral disease of equids that is transmitted by insects, primarily Culicoides.
African horse sickness is endemic in sub-Saharan Africa and outbreaks have periodically extended to the Middle East and southern Spain. The primary and biological vector is Culicoides but the virus may also be transmitted by mosquitoes. The virus has been isolated from certain ticks but arthropod transmission is not believed to play a significant role.
Clinical signs of AHS typically develop 5-7 days after infection and begin with fever and conjunctivitis. Some animals may recover but many go on to develop the pulmonary and/or cardiac forms of AHS. The pulmonary form consists of acute respiratory distress, coughing, sweating, and foaming from the nostrils; this form is usually fatal. The cardiac form consists of edema of the head and neck as well as abdominal pain and depression. A characteristic sign is swelling in the indentation above the eyes (also referred to as swelling of the supraorbital fossa). About 50% of animals with the cardiac form die from heart failure while the rest gradually recover after about one week.
Diagnosis can often be made based on history of exposure to endemic areas, clinical signs and lesions but must be confirmed by viral isolation and/or serology. There is no effective treatment and prevention/control can be accomplished by vector control and vaccination. There are multiple serotypes of virus and animals immunized against certain serotypes are still susceptible to others. In an outbreak situation, affected horses should be removed/euthanized and remaining horses should be vaccinated with a polyvalent vaccine until the specific serotype can be determined and then animals should be revaccinated with the corresponding vaccine.
For importing equids from Africa, a 2 month quarantine is required and then horses must test free of virus.
Presence of antibodies does not disqualify a horse from importation. Because of the vector-borne nature of the disease, it is recommended that planes flying from endemic areas be sprayed with insecticides on arrival to disease-free countries.
Two pet horses on a ranch are presented for extreme pruritus at their ventrum. The owners report the pruritus has gotten worse during the summer, and they notice increased numbers of small flying insects around at dusk and dawn. Examination of the horses reveals excoriations, alopecia, and thickening of the skin at the ventrum. One of the flies collected in the field by the owner is a small fly with mottled wings. What is your most likely diagnosis?
- Onchocerciasis
- Tabanus fly bites
- Mosquito hypersensitivity
- Culicoides hypersensitivity
- Chrysops fly bites
Answer: Culicoides hypersensitivity
Explanation
The correct answer is Culicoides hypersensitivity. Culicoides hypersensitivity is extremely pruritic and is also known as “sweet itch”. Horses can be affected on their ventrum or dorsum, depending on the species of the fly.
The horse develops a type 1 hypersensitivity to the flies’ salivary antigens and develops excoriations, alopecia, and thickened skin as a result of scratching. The flies are more prevalent during the warmer seasons and are most active during dusk and dawn. Treatment includes controlling the fly population.
Stabling the horses at dusk is often helpful because the flies rarely enter barns. Insecticides, stable blankets, and fans for circulating air dain saling the horting air in the stables may also be useful. The extreme pruritus and seasonality of the clinical signs is often enough to differentiate the Culicoides hypersensitivity from other skin diseases. Onchocerciasis is vectored by Culicoides, but has seasonal variability and is not nearly as pruritic. Mosquitoes can be an annoyance and, more importantly, are vectors for more serious diseases such as the equine encephalitides. Tabanus flies and Chrysops flies cause pain to horses by lacerating them with their mouth parts to feed on their oozing blood.
They do not cause pruritus and can be differentiated by their large, robust size.
One of your clients recently purchased a horse that she plans to add to her stable. She is concerned about potential exposure of the horse to Streptococcus equi subsp. equi. Which of the following is the most sensitive test for detecting carriers of the disease?
- Serology for antibodies to S. equi M protein (SeM)
- Nasopharyngeal culture on Columbia CNA (colistin, nalidixic acid) agar with 5% sheep or horse blood
- PCR of a guttural pouch wash for the S. equi M protein (SeM) gene
- Guttural pouch culture Columbia CNA (colistin, nalidixic acid) agar with 5% sheep or horse blood
Answer: PCR of a guttural pouch wash for the S. equi M protein (SeM) gene
Explanation
Testing for Streptococcus equi subsp. equi can be complex. The 3 major tests are PCR, serology, and culture.
PCR and serology both detect SeM which is an important virulence factor for the bacteria. Culture is best performed on Columbia CNA agar with 5% sheep or horse blood.
While there are pros and cons to each test, the key to answering this question correctly is focusing on the issues of sensitivity and detecting carriers.
PCR is approximately 3 times more sensitive than culture. In general, sampling the guttural pouch is a better way to detect carriers than the nasopharynx because it is where most carriers harbor the organism.
Serology is the best test for assessing exposure but is not a good tool for detecting carriers. This is because antibodies may be elevated after an infection has been cleared or even after vaccination. It may also be falsely negative if an exposure was recent.
To summarize the best uses of culture, PCR and serology:
Culture is the gold standard for diagnosing a horse with an infection.
PCR is best for detecting asymptomatic carriers, establishing infection status prior to or following transport, and to determine the success of elimination of S. equi from the guttural pouch. PCR cannot distinguish live DNA from dead DNA and may have false positives after a cleared infection. Using PCR in combination with culture may be helpful in such an instance.
Serology is best for determining exposure and the need for vaccination as well as for supporting diagnoses of S equi associated purpura hemorrhagica or of bastard strangles.
A 12-year old Quarter Horse gelding is presented for progressively worsening clinical signs of ataxia, intermittent head pressing and prolonged recumbency over the last month. The heart rate is modestly elevated (HR-48 beats/min) but the temperature and respiratory rate are within normal limits. The CBC and biochemistry profile are relatively unremarkable except for mild elevations in the CK and AST. Based on the suspicion of neurologic disease, you then collect cerebrospinal fluid (CSF) from the lumbosacral space yielding the following results:
CSF fluid analysis:
Total nucleated cell count: 86 cells/microliter (reference interval < 6 cells/microliter)
Protein: 118 mg/dL (reference interval 50-80 mg/dL)
Cytology: 14% neutrophils, 57% lymphocytes, 20% macrophages, 7% eosinophils, and 2% basophils.
Based on the above information, what is the most likely cause?
- Hepatoencephalopathy
- Verminous encephalomyelitis (Halicephalobus deletrix)
- Cervical vertebral malformation (Wobbler syndrome)
- Equine protozoal myeloencephalitis (Sarcocystis neurona)
- Equine herpes myeloencephalopathy (EHV-1)
Answer: Verminous encephalomyelitis (Halicephalobus deletrix)
Explanation
This is a tough question, but the correct answer is verminous encephalomyelitis caused by H. deletrix.
Aberrant migration of helminth or fly larvae through the CNS of horses is uncommon, but is a reported cause of neurologic disease. Causative organisms include Halicephalobus deletrix, Draschia megastoma, Hypoderma, strongyloid nematodes, as well as others. If you did not know the answer immediately, you can deduce the correct answer with knowledge of the other diseases.
Wobbler syndrome is usually observed in younger horses (< 5 year of age) and typically does not cause changes in the CSF.
Equine herpes myeloencephalopathy is a consideration, but clinical signs are typically related to hind-limb paresis, bladder dysfunction, and fecal retention along with a xanthochromic (yellow) CSF from the break-down of RBCs that are associated with the vasculitis induced by the herpes virus.
Hepatoencephalopathy could cause the clinical signs observed here, but no evidence of hepatic failure was presented in the question.
Finally equine protozoal myeloencephalitis (EPM); typically EPM does not cause head-pressing but may be possible. In addition, EPM infection does not typically change the CSF. Therefore, by eliminating these other choices, you are left with verminous encephalomyelitis. Also take note that there is an elevation in eosinophils within the CSF, suggesting a parasitic cause.
A 3-year old Thoroughbred race horse presents for lameness evaluation. The trainer reports that the lameness has been slowly progressive over the past 6 weeks. You observe the horse walk and see a short, choppy gait in the front legs. There is swelling over the front of both fetlock joints and palpation and flexion of the fetlocks elicits pain. Which of the following is the most likely diagnosis?
- Osselets
- Low ringbone
- High ringbone
- Navicular syndrome
- Sidebones
Answer: Osselets
Explanation
Osselets are inflammation of the periosteum on the dorsal distal epiphyseal surface of the third metacarpal bone and fetlock joint. As in this case, they are often (but not always) bilateral. Osselets typically begin from chronic stress injury to the front fetlock(s) from repeated concussive forces during racing and hard training.
Horses with long or upright pasterns may be predisposed. The major clinical signs are increasing lameness and a short choppy gait. Thickening and soreness of the fetlock are also frequently seen. Early diagnosis and intervention is important because once the condition progresses to osteoarthritis, the prognosis is much worse.
If recognized early and treated with rest, anti-inflammatory medications, and intra-articular sodium hyaluronate injections, many horses can recover completely.
None of the other choices listed are associated with the fetlock. Low ringbone is osteoarthritis of the distal interphalangeal (coffin) joint. High ringbone is osteoarthritis of the proximal interphalangeal (pastern) joint.
Sidebones are ossification of the collateral (alar) cartilages of P3. Navicular syndrome affects the heel.
Sesamoiditis is usually caused by which of the following in horses?
- Extension of tendonitis
- Penetrating wounds
- Chronic sesamoid fractures
- Septicemia
- Tearing of the ligamentous attachments
Answer: Tearing of the ligamentous attachments
Explanation
The correct answer is tearing of the ligamentous attachments. During strenuous exercise, the insertion of ligaments on sesamoid bones can tear, leading to sesamoiditis. Clinical signs can be similar but are generally less severe than sesamoid fractures (lameness, inflammation). Radiographic findings in sesamoiditis can include new bone formation or osteolytic lesions and radiolucent lines which are prominent vascular channels.
Treatment involves long term rest and NSAIDs. Prognosis is guarded to poor.
You diagnose Pneumocystis carinii pneumonia in a 6-week old Arabian foal. A complete blood count shows:
hematocrit=31% (27-43 %)
neutrophils- 1,300/ul (2,900-8,500/ul)
lymphocytes- 227/ul (1,160-5,100/ul)
monocytes- 800/ul (0-700/ul) eosinophils- 700/ul (0-780/ul)
Which of the following is the most likely reason for this problem?
- Severe combined immunodeficiency
- Exposure to Pneumocystis via infected mosquitoes
- Ingestion of moldy feed
- Aberrant migration of Pneumocystis into the lung
- Failure of passive transfer
Answer: Severe combined immunodeficiency
Explanation
Arabian foals that are homozygous for the SCID gene appear normal at birth but then develop fatal infections, often from unusual organisms like Pneumocystis. The SCID trait is autosomal recessive. A genetic test now exists for this disease.
The lesion associated with this horse’s source of colic is pictured below. The lesion causing the pathology seen in the intestine has been separated and is seen to the left of the image. What is the most common signalment for this cause of colic.
- Mid- to older (15-20 years of age) geldings
- Adolescent (3-5 years of age) mares
- Any age stallions
- Horses less than 1 year of age
Answer: Mid- to older (15-20 years of age) geldings
Explanation
You must first identify the cause of colic as being a strangulating lipoma. The lipoma is to the left and has been untangled from the intestine where it was strangulating part of the small intestine (notice the normal colored small intestinal serosa as compared to the dark purple section). There is a strong association with strangulating lipomas occurring in older horses, especially geldings. Thus, mid-to older age geldings is the best answer.
***PowerLecture: Gastrointestinal Disorders
A Paint horse mare gives birth to an all white foal (see image). What clinical sign would you expect to see in a foal with lethal white syndrome?
- Regurgitation
- Constipation
- Anhydrosis
- Ataxia
Answer: Constipation
Explanation
The correct answer is constipation. Lethal white foals have aganglionosis of the intestines which leads to hypomotility, megacolon, constipation, colic, and death.
***PowerLecture: Foal Neuromuscular Disorders
A 2-month-old Thoroughbred foal presents with the onset of profuse watery diarrhea and you suspect salmonellosis (see image). There are three specific diagnostic parameters that you, as the clinician, must assess to determine whether or not this patient should be confined to isolation. What are the three diagnostic parameters?
- There are no specific diagnostic parameters for isolation qualification. Any foal or horse with diarrhea should be admitted to isolation.
- Diarrhea, fever, and neutropenia. All 3 of the diagnostic parameters must be present to qualify for isolation.
- Diarrhea, fever, and neutrophilia. All 3 of the diagnostic parameters must be present to qualify for isolation.
- Diarrhea, fever, and neutropenia. Any 2 of the 3 diagnostic parameters qualify for isolation.
- Diarrhea, fever, and neutrophilia. Any 2 of the 3 diagnostic parameters qualify for isolation.
Answer: Diarrhea, fever, and neutropenia. Any 2 of the 3 diagnostic parameters qualify for isolation.
Explanation
The correct answer is diarrhea, fever, and neutropenia. Any 2 of these 3 parameters meet the criteria to admit any equine patient into isolation. The most likely cause of the neutropenia is bacterial septicemia and endotoxemia due to gastrointestinal disease. Other common diseases that can cause a neutropenia are metritis and coliform mastitis.
You are examining a 12 year old Quarter Horse that was recently in a barn fire (see image). You suspect that the epidermis, dermis and adnexal (i.e. hair, sweat glands) structures are involved. Based on the structures involved, you would classify this as what type of burn?
- 4th degree burn
- 2nd degree burn
- 1st degree burn
- 3rd degree burn
Answer: 3rd degree burn
Explanation
A 3rd degree burn involves the epidermis, dermis, and adnexal structures. Alternatively, a 1st degree (superficial) burn involves the epidermis only; a 2nd degree (partial thickness) burn involves the epidermis and may go down to the deep dermis. 4th degree burns involve total destruction of the skin, fat, fascia, bone and muscle.
This classification scheme would generally apply to all animals, not just horses.
Which of the following choices correctly identifies the leukocyte in this image of a blood smear from a horse, and the most common types of diseases to which it responds?
A - Neutrophil; wound repair and bacterial infection
B - Lymphocyte; immune disease and viral infection
C - Basophil; allergy and parasitic infestation
D - Monocyte; viral/bacterial infection, and chronic inflammation
E - Macrophage; bacterial and viral infection
Answer: Basophil; allergy and parasitic infestation
This is a basophil, typically associated with allergy or parasite infestation. Basophils (BSO), eosinophils (EOS), and neutrophils (PMNs) are the three types of granulocytic white blood cells.
Phagocytosis is an important function of EOS and PMNs but this is not a primary role of BSOs.
Granulocytic phagocytes have segmented nuclei and cytoplasmic granules - orange/pink in EOS; purple/dark blue in BSOs; pale pink in PMNs.
The granules of basophils contain many mediators of inflammation and large amounts of histamine.
They commonly respond to allergic conditions and parasite infestation, similar to eosinophils.
For more info and images, see the Cornell Clin
Path website:
Hematology Atlas, and Equine blood cells.
Image courtesy of Guy Waterval.
https://eclinpath.com/atlas/hematology/
