Horses Flashcards
A horse presents to your clinic after ingesting a large amount of grain. What is your major concern?
A. Choke
B. Torsion
C. Impaction
D. Laminitis
E. Acidosis
Answer: Laminitis.
The correct answer is laminitis secondary to endotoxemia. Laminitis, endotoxemia, and diarrhea are commonly associated with grain overload and appropriate therapy to evacuate any remaining stomach contents, ameliorate endotoxin and prevent laminitis should be instituted immediately. Laxatives such as mineral oil are commonly administered.
Which of the following is not known to classically cause crusting dermal lesions on horses?
Pemphigus foliaceus
Generalized granulomatous disease
Corynebacterum pseudouberculoss
Dermatophilosis
Dermatophytosis
Answer: Corynebacterium pseudotuberculosis
Explanation
The correct answer is Corynebacterium pseudotuberculosis. Corynebacterium pseudotuberculosis is also known as pigeon fever. It causes an ulcerative lymphangitis and abscesses in the pectoral region of horses. Treatment is aimed at hot packing the swellings and draining the abscesses. Antibiotics can be administered but have been known to prolong the disease by delaying abscess formation. The other four answer choices classically present as crusting dermal lesions on horses.
A 4-year old male Thoroughbred horse presents to you for colic. During your work up, you note a painful enlargement at the root of the mesentery on rectal palpation. You suspect that the cause of the horse’s colic are adults from the egg shown in the
picture below. Which of the following drugs effectively kills the adult organisms that can cause this condition?
A. Rifampin
B. Metronidazole
C. Praziquantel
D. Piperonyl butoxide
E. Ivermectin
Answer: Ivermectin
Colic with an associated painful mass at the root of the mesenery is suspicious for verminous arteritis caused by damage to the cranial mesenteric artery and its branches by Strongylus vulgaris. The strongyle egg shown in the picture confirms the cause in this question. A number of anthelmintics are effective including benzimidazoles, pyrantel and ivermectin.
Praziquantel is effective against tapeworms. Rifampin and metronidazole are antibacterial drugs. Piperonyl butoxide is a pesticide synergist used in insecticide mixtures in horses.
A client notices that her 8-year old Paint Horse gelding is lethargic, inappetant and looks to be in pain when forced to walk. Additionally, your client collected a urine sample for you to examine (see image). You collect a plasma sample to help determine the cause and it appears clear and normal. Which of the answer choices accurately describes a likely clinical scenario?
Extravascular hemolysis based on urine color and normal-appearing plasma
Normal urine based on the fact that horse urine has ample calcium carbonate crystals
Hemoglobinuria based on urine color and a normal-appearing plasma sample
Myoglobinuria based on urine color and a normal appearing plasma sample
Answer: Myoglobinuria based on urine color and normal appearing plasma sample.
Explanation
Myoglobinuria is characterized by brownish urine that does not clear on centrifugation along with normal-colored plasma. Myoglobin does not bind to serum proteins and is quickly excreted before reaching levels that would discolor the plasma. Also, the painful gait suggests a myopathy that may be related to the myoglobinuria.
Conversely, hemoglobinuria is associated with a reddish discoloration of the plasma because hemoglobin is maintained in the plasma longer and is lost in the urine more slowly.
A 9-month old foal presents with difficulty walking. You immediately note that the foal appears to have a flexural deformity of the right forelimb consisting of an increased dorsal hoof wall angle of 80 degrees such that the heel does not contact the ground. The coronary band is prominent. You take radiographs which confirm a broken forward hoof-pastern angle. What is the most appropriate treatment for this type of flexural limb deformity?
- Superior check ligament desmotomy
- Lateral digital extensor tenectomy
- Desmotomy of the accessory ligament of the deep digital flexor tendon
- Transection of the insertion of the semitendinosus
Answer: Desmotomy of the accessory ligament of the deep digital flexor tendon
Explanation
This case describes a severe flexural deformity of the distal interphalangeal joint, also known as “clubfoot”. This is typically a congenital condition in young horses although it can be acquired. A genetic component is suspected. Mild cases can sometimes be managed conservatively with NSAIDs, farriery, exercise and nutritional changes. Severe cases often require surgery; the surgical procedure of choice is desmotomy of the accessory ligament of the deep digital flexor tendon (also known as inferior check ligament desmotomy). The accessory ligament of the deep digital flexor tendon (inferior check ligament) runs from the palmar surface of the proximal metacarpus to the deep flexor tendon in the mid-metacarpal region.
The superior check ligament originates above the knee and attaches to the superficial flexor tendon, and its primary purpose is to support the tendon. Superior check ligament surgery is used to treat a bowed tendon.
Lateral digital extensor tenectomy is a procedure used to treat stringhalt. Transection of the insertion of the semitendinosus is used to treat fibrotic myopathy.
It is a rainy April and you are visiting a horse farm to evaluate a horse with itchy and flaky skin lesions on the pastern and mild lameness. On examination, you see an exudative seborrheic dermatitis of the plantar aspect of the pastern that is slightly malodorous. Which of the following is a term used to describe this condition in horses?
Sweeney
Summer sores
Sweet itch
Scratches
Ringbone
Answer: Scratches
Explanation
Scratches is a condition of chronic seborrheic dermatitis of the palmar/plantar aspect of the pastern. The condition is sometimes referred to by several other names including “grease heel”, “dermatitis verrucosa”, “dew poisoning” and “mud fever”. It is not specific to the underlying infectious cause but the condition is generally associated with horses kept in wet or muddy environments.
Summer sores are caused by Habronema spp. and Draschia spp. stomach worms of the horse. The larvae in feces are ingested by the maggots of flies, and the flies can deposit them at susceptible moist skin areas, damaged skin areas, or mucous membranes where the larvae cause an eosinophilic granuloma as a reaction to their migration.
Sweet itch results from a Type 1 allergic reaction to Culicoides spp. Clinical signs of sweet itch are usually in the form of self-trauma due to pruritus.
Sweeney is the common name for shoulder atrophy in the horse. The muscle atrophy is caused by damage to the suprascapular nerve which innervates to the infraspinatus and supraspinatus muscles.
Ringbone refers to osteoarthritis or bony exostosis in the pastern (high ringbone) or coffin (low ringbone) joints.
A 9-year old Standardbred stallion comes to see you for evaluation of muscle atrophy. You examine the horse and note atrophy of the lateral thigh and gluteal muscles. When the horse is backed up, spasmodic hyperflexion of either hindlimb occurs resulting in a high-stepping gait. Which of the following is most likely responsible for the observed signs?
Black walnut intoxication
Sweet pea intoxication
Senecio or groundsel intoxication
Castor bean intoxication
Red maple intoxication
Answer: Sweet pea intoxication
Explanation
This case describes a horse with stringhalt or sudden flexion (contraction of the lateral extensor tendons) of one or both hind legs. It is most evident when the horse is backing up slowly or turning. It can involve one or both hind legs. The etiology in some cases is unknown but the condition can be associated with chronic intoxication of sweet peas (Lathyrus spp.). Australian stringhalt has been associated with flatweed ingestion (Hypochoeris radicata). The precise pathogenesis is not understood, but a mycotoxin affecting the long myelinated nerves in the hind limbs has been suggested based on the types of nerve damage seen in affected horses.
Black walnut intoxication is associated with laminitis and colic after exposure to wood shavings of black walnuts.
Red maple intoxication is associated with acute hemolytic anemia. Senecio or groundsel intoxication is associated with liver disease after chronic exposure. Castor bean intoxication is associated with severe gastrointestinal irritation and hemorrhagic diarrhea.
You are assessing welfare of horses at a lesson barn. Most captive horse welfare concerns develop due to which of the following?
Social hierarchy issues
Colic
Lack of exercise
Escape
Neglect
Answer: Neglect
Explanation
The majority of animal welfare concerns in captive horses are due to neglect.
Which of the following is true regarding equine rabies vaccination in the United States?
It is not required by law but recommended
It is mandated by state law in all 50 states
It is mandated by federal law
It is required by state law only in endemic areas
Answer: It is not required by law but recommended
Explanation
Rabies vaccination in horses is only recommended in endemic areas and is not required by law. In endemic areas, boosters are usually performed annually.
The American Association of Equine Practitioners (AAEP) recommends rabies as a core vaccine in horses.
You wish to sedate a horse to re-check a lesion on the hind leg. Which of the following choices will provide the shortest duration of action?
Xylazine
Romifidine
Medetomidine
Detomidine
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. Although xylazine will provide the shortest duration of action, clinicians are told to be careful when using xylazine and working with the hind limbs because these horses can have a sudden rapid limb movement known as a phantom kick. 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 believed to be decreased.
Which of these would be appropriate for a horse with hyperkalemic periodic paralysis (HYPP)?
Timothy hay
Alfalfa hay
Beet molasses
Brome hay
Answer: Timothy hay
Explanation
The correct answer is timothy hay. Of these choices, the only feed with low potassium is timothy hay. A low potassium diet is the most important nutritional modification in the treatment of HYPP. Regular exercise and feeding smaller, frequent meals can also reduce clinical signs. This disease is inherited in an autosomal dominant fashion, and owners should be discouraged from breeding affected animals.
***PowerLecture: Musculoskeletal Disorders
For a horse with hyperkalemic periodic paralysis (HYPP), timothy hay is the appropriate feed because it is low in potassium, which is crucial in managing HYPP. A low potassium diet, along with regular exercise and smaller, frequent meals, helps reduce clinical signs. HYPP is an autosomal dominant inherited condition, and breeding affected animals should be discouraged.
Hyperkalemic Periodic Paralysis
Hyperkalemic periodic paralysis (HYPP) is marked by sudden attacks of paralysis which, in severe cases, may lead to collapse and sudden death. It is an inherited mis-sense mutation in the gene encoding the alpha chain of the adult skeletal muscle sodium channel, resulting in increased sodium permeability across the skeletal muscle cell membrane. Quarter horse, Paint horse, and Appaloosa progeny tracing back to the Quarter horse sire “Impressive” can be affected with this disease and must be eliminated from any reproductive program. Most affected horses are heterozygotes. A sequela of HYPP in horses that undergo general anesthesia is malignant hyperthermia syndrome.
Which nerve block would be most specific for alleviating pain associated with laminitis?
Suspensory ligament block
Abaxial sesamoid block
Palmar digital block
High 4 point block
Answer: Abaxial sesamoid block
Explanation
The correct answer is the abaxial sesamoid block. The four basic blocks used by equine clinicians are the palmar digital, abaxial sesamoid, low four point and high four point block, each desensitizing more of the limb as your blocks move more proximal on the limb. The palmar digital desensitizes the palmar third of the foot whereas the abaxial sesamoid desensitizes the entire foot. As laminitis is associated with separation of the dorsal lamina, the abaxial sesamoid block would be most likely help with laminitis. Of note, desensitizing the foot during acute laminitis is not typically employed as a standard treatment but is rather used to help alleviate pain so that the clinician can perform radiographs of the feet or trim the feet. The low 4 point block desensitizes the palmar aspect distal to the distal end of the second and fourth metacarpals. The high 4 point block desensitizes the leg distal to the carpus or tarsus. The suspensory ligament block desensitizes the deep branch of the lateral palmar nerve at the level of the carpometacarpal joint.
***PowerPage: Nerve Blocks
You diagnose this 15-year old mare in the picture with a mild, acute laminitis. Which of the following can be used as treatment for this horse?
Trimethoprim sulfa
Phenoxybenzamine
Application of horse shoes
Prednisone
Answer: Phenoxybenzamine
Explanation
The correct answer is phenoxybenzamine. Phenoxybenzamine is an alpha-adrenergic antagonist promoting vasodilation and restoration of blood flow to the digits. Prednisone is contraindicated in laminitis because corticosteroids are believed to induce the condition. Antibiotics are not indicated unless a secondary bacterial infection develops. Application of a horse shoe would not help and would be very painful in an already sensitive and painful condition. Other medications used to restore blood flow to the digits include acepromazine, isoxsuprine hydrochloride, dimethylsulfoxide (DMSO), heparin, and nitroglycerine.
A Thoroughbred race horse has been moved from California to Florida in July and is experiencing poor performance, exercise intolerance and tachypnea. You observe the horse working out one hot afternoon and see these signs, but you also note that the horse is not sweating. You check the rectal temperature and note that it is 104F (40 C). What is the diagnosis?
Equine Cushing’s
Hypothyroidism
Influenza
Anhidrosis
Diabetes insipidus
Answer: Anhidrosis
Explanation
Anhidrosis is the inability to sweat, which can be fatal if not addressed. The cause is unknown. It tends to occur in hot humid climates, and may occur in horses raised in the climate, or more commonly, horses brought into the climate. The most successful treatment is to move the horse back to a more favorable climate.
What body systems are most affected in an anaphylactic reaction in a horse?
`
Lungs and colon
Liver and lungs
Kidney and colon
Liver and kidneys
Heart and small intestine
Answer: Lungs and colon
Explanation
The correct answer is lungs and colon. These are referred to sometimes as the shock organs in the horse. When a horse undergoes an anaphylactic reaction from an allergen or chemical stimulus, the primary signs will be respiratory and lower Gl and will include dyspnea or severe respiratory distress and diarrhea. Other common signs include anxiety, tachycardia, piloerection, and sweating. Treatment of anaphylactic shock usually includes injection with some combination of epinephrine, corticosteroids, and an antihistamine.
Measurement of blood lactate is commonly used in foals and adult horses as an overall reflection of cardiovascular status. What is the normal blood lactate in a healthy foal or horse?
Less than 2.5 mmol/L
Less than 5 mmol/L
Less than 10 mmol/L
Less than 7.5 mmol/L
Answer: Less than 2.5 mmol/L
Explanation
The correct answer is 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 hand-held lactometers that do not provide a reference range.
As you may recall, 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 (different reports provide different findings), but not surprisingly, the higher the lactate, the poorer the prognosis.
***PowerLecture: Failure Of Passive Transfer And Foal Septicemia
You suspect disseminated intravascular coagulation (DIC) in a 16-year old Arab mare presented for colic and epistaxis (see image). Which of the following parameters is NOT associated with a diagnosis of DIC?
Prolongation of Prothrombin Time (PT)
Elevation in D-dimers
Decreased antithrombin Ill activity
Thrombocytopenia
Abbreviated (shortened) activated partial thromboplastin time (aPTT)
Answer: Abbreviated (shortened) activated partial thromboplastin time (aPTT)
Explanation
Disseminated intravascular coagulation is a complex disorder that can be described as widespread activation of the coagulation system, resulting in a pro-coagulant state with systemic thromboses and secondary diffuse hemorrhage throughout the body. DIC is secondary to pathologic conditions such as sepsis, localized infections, colitis, neoplasia, trauma, hepatic or renal failure, vasculitis, and various other disorders. DIC is associated with thrombocytopenia (from platelet consumption), prolongation of coagulation times such as PT and aPTT (from consumption of coagulation factors), elevations in D dimers (from degradation of fibrin), and low antithrombin Ill (from consumption). Thus the correct answer to this question is shortened aPTT. These criteria for DIC apply to all species, not just horses.
Disseminated Intravascular Coagulation (DIC) in Veterinary Medicine: NAVLE Study Guide
Definitions and Etiology
• DIC: A secondary, life-threatening condition characterized by widespread intravascular coagulation leading to microthrombi formation and subsequent multiorgan failure, accompanied by paradoxical bleeding due to the consumption of platelets and clotting factors. • Causes: DIC can arise from numerous conditions, including sepsis, severe infections (e.g., canine parvovirus, FIP), neoplasia (e.g., hemangiosarcoma), trauma (e.g., heatstroke, burns), and immune-mediated diseases (e.g., IMHA).
Pathophysiology
• Mechanisms: Excessive thrombin generation leads to systemic fibrin formation and microthromboses. The consumption of clotting factors and platelets results in thrombocytopenia and hypocoagulability, causing hemorrhagic diathesis. • Fibrinolysis: Impaired fibrinolysis due to increased plasminogen activator inhibitor (PAI-1) leads to an accumulation of fibrin and reduced clearance of microthrombi.
Clinical Signs
• Phases of DIC: • Peracute/Hypercoagulable: Rapid onset with microvascular thrombosis, shock, and multiorgan failure. • Acute Consumptive: Characterized by widespread hemorrhage, petechiae, and ecchymoses. • Chronic Silent: May present with subtle signs such as intermittent bleeding or thrombosis, often seen in malignancies. • Specific Signs: Spontaneous bleeding (e.g., hematuria, melena), shock, organ dysfunction (e.g., renal failure), and neurological deficits.
Diagnosis
• Laboratory Tests: • Coagulation Tests: Prolonged PT, aPTT, elevated D-dimers, reduced fibrinogen, and low antithrombin (AT) levels. • Blood Smear: Presence of schistocytes. • Advanced Diagnostics: Thromboelastography (TEG) for monitoring coagulation status, D-dimer assays for fibrin degradation products.
Treatment
• Primary Goal: Treat the underlying cause (e.g., antibiotics for sepsis, surgery for tumors) and manage coagulopathy. • Supportive Care: • Blood Products: Fresh frozen plasma (FFP) or fresh whole blood to replace consumed clotting factors. • Anticoagulants: Heparin or low-molecular-weight heparin (LMWH) during the hypercoagulable phase, particularly if AT activity is sufficient. • Novel Therapies: Experimental treatments in human medicine, such as recombinant activated protein C (APC) and antithrombin concentrates, may have potential in veterinary practice.
Prognosis
• Outcome: Varies based on the underlying cause, stage of DIC, and response to treatment. The prognosis is generally guarded to poor, with early detection and intervention being critical to improving outcomes.
Key Points for Veterinary Professionals
• Monitoring: Regularly assess coagulation status in patients at risk for DIC using a combination of clinical signs and laboratory tests. • Intervention: Early, aggressive treatment of the underlying cause and careful management of coagulopathy are essential. • Emerging Therapies: Stay updated on advancements in DIC management, particularly those translating from human to veterinary medicine.
Which antibiotic is contraindicated in foals?
Cefazolin
Enrofloxacin
Ampicillin
Amikacin
Gentamicin
Answer: Enrofloxacin
Explanation
The correct answer is enrofloxacin. Enrofloxacin is a fluoroquinolone and thus, its mechanism of action involves the inhibition of DNA gyrase. The reason you don’t want to use it in foal is because it can result in arthrotoxicity and subsequent erosion of cartilage. Ampicillin, gentamicin, and amikacin are commonly used to provide broad-spectrum coverage against potential septicemia. Ampicillin is a penicillin; gentamicin and amikacin are both aminoglycosides. Cefazolin is a first-generation cephalosporin that is occasionally used in the face of septicemia if a penicillin is not available.
Which of these vaccines administered intramuscularly is most likely to cause a local reaction at the injection site of a horse?
Rabies
Tetanus antitoxin
Rhinopneumonitis
Strangles
Answer: Strangles
Explanation
Historically, an intramuscularly administered Strangles vaccine has been available and has been associated with soft tissue reaction. More recently, an intranasal vaccine has become available, which is associated with local protection without any injection reaction.
Which of the following is one of the biggest welfare concerns for wild horses and burros?
Fighting
Lack of veterinary care
Exposure to weather
Rough terrain
Overpopulation
Answer: Overpopulation
Explanation
Overpopulation is a major welfare concern and can lead to starvation and death without proper herd management.
Horses that are used to pull carriages in tourist destinations, so-called “carriage horses”” commonly experience leg and hoof issues that impact their long-term welfare. These issues stem from:
Excessive time spent on very hard surfaces such as concrete
Inappropriate training
Injuries caused by neglect
Lack of insufficient nutrients to support bone health
Answer: Excessive time spent on very hard surfaces such as concrete
Explanation
Carriage horses spend hours at a time on hard asphalt or concrete, which increases the incidence of hoof and leg conditions.
A 4-year old Arabian mare is shipped from the United Arab Emirates to New York where you examine the horse. You note that the horse has a mucopurulent discharge from the nares and has labored breathing and cough. Heart rate is 24 bpm, respiratory rate is 40 breaths per minute and temperature is 104.9 F (40.5 C). You make a smear of the discharge and see large numbers of extracellular straight Gram-negative rods with rounded ends. Which diagnostic test is most likely to confirm your clinical suspicion?
PCR of the exudate for SeM protein of Streptococcus equi subsp. equi
Biopsy of the mandibular lymph node
Mallein test
PCR of the exudate for Rhodococcus equi virulence associated plasmid
Viral culture of a guttural pouch wash
Answer: Mallein test
Explanation
The horse’s history of arrival from the United Arab Emirates along with the clinical and cytologic findings are consistent with the nasal form of glanders.
Burkholderia mallei causes 3 different forms of disease; nasal glanders, pulmonary glanders, and cutaneous glanders (also referred to as Farcy).
The nasal form presents with high fever, loss of appetite and labored breathing with cough. Viscous mucopurulent discharge or crusting may be present around the nares. There may be ulceration of the upper respiratory passages that resolve in the form of star-shaped cicatrices (“stellate scars”). Regional lymph nodes may be enlarged and indurated and may rupture or adhere to deeper tissues.
The pulmonary form often develops over several months, beginning as a fever with dyspnea and cough. Lung lesions commence as light colored nodules surrounded by hemorrhage or as diffuse pneumonia. The nodules may become caseous or calcified and discharge contents to the upper respiratory tract. Nodules may also be found in other organs.
The cutaneous form develops over several months, beginning with cough and dyspnea as well. Eventually, nodules develop in subcutaneous tissue along the course of the lymphatics of the legs, costal areas, and ventrum. They can rupture and excrete infectious purulent exudate. Infected lymphatics may form thickened cord-like lesions that sometimes coalesce into a string of beads appearance known as “farcy pipes”. Nodular lesions of other organs may also be found.
Burkholderia mallei can be identified in smears made from fresh lesions as mainly extracellular straight Gram-negative rods with rounded ends. Several diagnostic tests exist including PCR, ELISA, and Western Blot but the two that you actually need to know about because they are used in international trade are complement fixation (CF) serology and the mallein test. The mallein test is considered the most reliable, sensitive, and specific test; it involves injection of mallein purified protein derivative intradermally into the lower eyelid. The test is read at 24 and 48 hours and a positive reaction is characterized by edematous swelling or purulent discharge.
Horses should not be treated; local authorities should be notified if a case is suspect and if disease is confirmed, horses must be humanely destroyed and affected carcasses should be burned and buried.
The most likely test to confirm glanders in a horse with a history of arrival from the UAE, mucopurulent nasal discharge, labored breathing, and Gram-negative rods in the discharge, is the mallein test. Glanders, caused by Burkholderia mallei, can present in nasal, pulmonary, or cutaneous forms. The mallein test involves injecting purified protein derivative into the lower eyelid and checking for a reaction. If glanders is confirmed, the horse must be humanely destroyed, and the carcass appropriately disposed of.
Glanders: Overview
Causative Agent
• Bacteria: Burkholderia mallei.
Pathophysiology
• Transmission: Direct contact with infected animals, ingestion of contaminated food/water, inhalation.
• Invasion: Bacteria enter through mucous membranes, spreading via lymphatics and bloodstream, leading to multiple organ involvement.
Clinical Signs
• Acute Form: High fever, nasal discharge, nodules, ulcers.
• Chronic Form: Progressive weight loss, nodular lesions in lungs and spleen, cutaneous form (“farcy”) with nodules along lymphatics.
• Latent Form: Inapparent infections, may reactivate under stress.
Diagnosis
• Tests: Mallein test, culture, PCR, serology (e.g., CFT, ELISA).
• Necropsy Findings: Granulomatous nodules, caseous material in organs.
Treatment and Prevention
• No Effective Treatment: Euthanasia recommended.
• Prevention: Quarantine, strict biosecurity, disinfection, and controlling animal movements.
Zoonotic Potential
• Humans: Can contract glanders through direct contact, presenting with pneumonia, septicemia, and skin infections. Fatal if untreated.
A 4-year old Arabian mare is shipped from the United Arab Emirates to New York where you examine the horse. You note that the horse has a mucopurulent discharge from the nares and has labored breathing and cough. Heart rate is 24 bpm, respiratory rate is 40 breaths per minute and temperature is 104.9 F (40.5 C). You make a smear of the discharge and see large numbers of extracellular straight Gram-negative rods with rounded ends. Which diagnostic test is most likely to confirm your clinical suspicion?
PCR of the exudate for SeM protein of Streptococcus equi subsp. equi
Biopsy of the mandibular lymph node
Mallein test
PCR of the exudate for Rhodococcus equi virulence associated plasmid
Viral culture of a guttural pouch wash
Answer: Mallein test
Explanation
The horse’s history of arrival from the United Arab Emirates along with the clinical and cytologic findings are consistent with the nasal form of glanders.
Burkholderia mallei causes 3 different forms of disease; nasal glanders, pulmonary glanders, and cutaneous glanders (also referred to as Farcy).
The nasal form presents with high fever, loss of appetite and labored breathing with cough. Viscous mucopurulent discharge or crusting may be present around the nares. There may be ulceration of the upper respiratory passages that resolve in the form of star-shaped cicatrices (“stellate scars”). Regional lymph nodes may be enlarged and indurated and may rupture or adhere to deeper tissues.
The pulmonary form often develops over several months, beginning as a fever with dyspnea and cough. Lung lesions commence as light colored nodules surrounded by hemorrhage or as diffuse pneumonia. The nodules may become caseous or calcified and discharge contents to the upper respiratory tract. Nodules may also be found in other organs.
The cutaneous form develops over several months, beginning with cough and dyspnea as well. Eventually, nodules develop in subcutaneous tissue along the course of the lymphatics of the legs, costal areas, and ventrum. They can rupture and excrete infectious purulent exudate. Infected lymphatics may form thickened cord-like lesions that sometimes coalesce into a string of beads appearance known as “farcy pipes”. Nodular lesions of other organs may also be found.
Burkholderia mallei can be identified in smears made from fresh lesions as mainly extracellular straight Gram-negative rods with rounded ends. Several diagnostic tests exist including PCR, ELISA, and Western Blot but the two that you actually need to know about because they are used in international trade are complement fixation (CF) serology and the mallein test. The mallein test is considered the most reliable, sensitive, and specific test; it involves injection of mallein purified protein derivative intradermally into the lower eyelid. The test is read at 24 and 48 hours and a positive reaction is characterized by edematous swelling or purulent discharge.
Horses should not be treated; local authorities should be notified if a case is suspect and if disease is confirmed, horses must be humanely destroyed and affected carcasses should be burned and buried.
The most likely test to confirm glanders in a horse with a history of arrival from the UAE, mucopurulent nasal discharge, labored breathing, and Gram-negative rods in the discharge, is the mallein test. Glanders, caused by Burkholderia mallei, can present in nasal, pulmonary, or cutaneous forms. The mallein test involves injecting purified protein derivative into the lower eyelid and checking for a reaction. If glanders is confirmed, the horse must be humanely destroyed, and the carcass appropriately disposed of.
CGPT: Glanders in Horses and Other Animals - Comprehensive Veterinary Information
Glanders: Overview
Causative Agent
• Bacteria: Burkholderia mallei.
Pathophysiology
• Transmission: Direct contact with infected animals, ingestion of contaminated food/water, inhalation.
• Invasion: Bacteria enter through mucous membranes, spreading via lymphatics and bloodstream, leading to multiple organ involvement.
Clinical Signs
• Acute Form: High fever, nasal discharge, nodules, ulcers.
• Chronic Form: Progressive weight loss, nodular lesions in lungs and spleen, cutaneous form (“farcy”) with nodules along lymphatics.
• Latent Form: Inapparent infections, may reactivate under stress.
Diagnosis
• Tests: Mallein test, culture, PCR, serology (e.g., CFT, ELISA).
• Necropsy Findings: Granulomatous nodules, caseous material in organs.
Treatment and Prevention
• No Effective Treatment: Euthanasia recommended.
• Prevention: Quarantine, strict biosecurity, disinfection, and controlling animal movements.
Zoonotic Potential
• Humans: Can contract glanders through direct contact, presenting with pneumonia, septicemia, and skin infections. Fatal if untreated.
A 9 year 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 your physical exam. Which of these is the most likely cause of recurrent, intermittent, unilateral epistaxis in this animal?
Exercise induced pulmonary hemorrhage
Ethmoid hematoma
Purpura hemorrhagica
Warfarin toxicity
Answer: Ethmoid hematoma
Explanation
The correct answer is ethmoid hematoma. An ethmoid hematoma 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 Ill immune complex hypersensitivity after a streptococcus equi infection. This leads to vasculitis, and the main clinical signs are petechia and ecchymoses of mucous membranes.
The most likely cause of recurrent, intermittent, unilateral epistaxis in a 9-year-old Thoroughbred mare is an ethmoid hematoma. This is a locally destructive mass that causes mild, spontaneous, and intermittent nosebleeds, which can be unilateral or bilateral. Other conditions like warfarin toxicity, exercise-induced pulmonary hemorrhage, and purpura hemorrhagica are less likely due to the specific nature of the symptoms and their typical presentations.
Progressive Ethmoid Hematoma in Horses: NAVLE Study Guide
Definitions and Etiology
• Progressive Ethmoid Hematoma (PEH): A non-neoplastic mass in the nasal passages or paranasal sinuses of horses, characterized by recurrent submucosal hemorrhage and subsequent encapsulation. The exact cause remains unknown.
Pathophysiology
• Expansion: PEH grows by repeated hemorrhage within the submucosa, leading to a well-encapsulated mass that can distort surrounding tissues and bone.
• Location: Originates from the ethmoidal labyrinth, potentially extending into nasal cavities or sinuses, causing local destruction and distortion.
Clinical Signs
• Common Symptoms:
• Epistaxis: Mild, intermittent, unilateral nosebleed, often the first sign.
• Respiratory Noise: Stridor due to airflow obstruction.
• Facial Deformities: Distortion of facial bones or swelling over the maxillary sinus.
• Advanced Signs: Head shaking, coughing, or dysphagia if the mass extends into the nasopharynx.
Diagnosis
• Initial Assessment:
• Endoscopy: Visualization of a greenish-yellow to purplish-red mass in the nasal cavity.
• Radiography: Lateral projections showing a soft tissue opacity in the ethmoidal labyrinth area, often with fluid lines.
• Histopathology: Definitive diagnosis through biopsy revealing submucosal fibrous tissue, hemorrhage, and inflammatory infiltrates.
• Advanced Imaging: CT or MRI can assess the extent of the mass and potential bone involvement.
Treatment
• Surgical Excision: Traditional method via frontonasal bone flap, often associated with significant hemorrhage.
• Complications: Hemorrhage, respiratory distress, recurrence (30-60%).
• Cryosurgery: Sequential freezing and surgical removal, potentially reducing hemorrhage but with risks like brain damage if improperly applied.
• Laser Surgery (Nd:YAG Laser): Precision excision with reduced morbidity, but risk of complications like respiratory distress and meningoencephalitis.
• Intralesional Formalin Injection: Minimally invasive, leading to mass regression but risks include nasal discharge and severe complications like neurological signs if the cribriform plate is compromised.
Prognosis
• Long-Term Outcome: Guarded to poor due to high recurrence rates despite treatment; regular follow-up and re-evaluation are necessary.
Key Points for Veterinary Professionals
• Early Detection: Crucial for better outcomes; regular endoscopic evaluations are recommended.
• Comprehensive Management: Treatment choice depends on mass size, location, and available resources.
• Multimodal Approach: Combining surgical and conservative treatments may offer the best outcomes.
What is the treatment for persistent epistaxis from guttural pouch mycosis?
Systemic itraconazole
Occlusion of appropriate artery or arteries
Ligation of the external carotid artery
Ligation of the external jugular vein
Answer: Occlusion of appropriate artery or arteries
Explanation
The correct answer is occlusion of appropriate artery or arteries. This closes off the artery over the guttural pouch, which has been destroyed by the fungal infection. Systemic itraconazole will not stop the bleeding.
The treatment for persistent epistaxis due to guttural pouch mycosis is the occlusion of the appropriate artery or arteries. This procedure stops the bleeding by closing off the artery that has been damaged by the fungal infection. Systemic itraconazole is ineffective in stopping the bleeding.
Guttural Pouch Mycosis in Horses - Comprehensive Veterinary Information
Definitions and Terminology:
• Guttural Pouch Mycosis: A fungal infection of the guttural pouch, often life-threatening.
Causative Agents:
• Primary Fungus: Aspergillus spp.
Physiopathology:
• Location: Fungal plaques form on the caudodorsal aspect of the medial guttural pouch over the internal carotid artery.
• Complications: Damage to cranial nerves and arteries, leading to hemorrhage and nerve dysfunction.
Clinical Signs:
• Epistaxis: Spontaneous, severe nasal bleeding, possibly recurrent.
• Neurologic Signs: Dysphagia, Horner syndrome, dorsal displacement of the soft palate, facial paralysis.
Diagnosis:
• Endoscopy: Visualization of fungal plaques.
• Clinical Signs: Observation of epistaxis and neurologic deficits.
Treatment:
• Antifungal Therapy: Prolonged topical and systemic antifungal treatment.
• Surgical Intervention: Occlusion of affected arteries (ligation, balloon catheter, or transarterial coil embolism) to prevent fatal hemorrhage and arrest fungal growth.
Prognosis:
• Varies: Based on severity of hemorrhage and neurological involvement.
A horse presents to you in respiratory distress. You perform blood gas analysis and get the following results: PaCO2-60 mmHg, Pa02- 75 mmHg, pH 7.255, Base excess= -1.8. How would you describe this horse’s status?
Hypoventilation, respiratory alkalosis
Hyperventilation, respiratory acidosis
Hyperventilation, respiratory alkalosis
Hypoventlaton， respiatoy acdoss
Answer: Hypoventilation， respiratoy acidosis
Explanation
The correct answer is hypoventilation, respiratory acidosis. Hypoventilation is defined by the PaCO2. Normal is about 40 (35-45). This horse has an elevated PaCO2 indicating he is under-ventilating and not blowing off sufficient CO2. This increase in CO2 causes a respiratory acidosis because CO2 is an acid that interacts with carbonic anhydrase to form carbonic acid. This is why the horse’s pH is low (normal pH is about 7.4). The relatively normal base excess indicates there is minimal metabolic component to this horse’s acidosis.
The horse’s status is hypoventilation with respiratory acidosis. The elevated PaCO2 (60 mmHg) indicates inadequate ventilation, leading to CO2 retention, which causes respiratory acidosis by forming carbonic acid. The low pH (7.255) confirms acidosis, and the normal base excess suggests minimal metabolic involvement.
You suspect pleuropneumonia with pleural effusion in a horse. What is the proper site for thoracocentesis for pleural effusion removal in the horse if ultrasound is not available?
7th rib space at costochondral junction
10th rib space in the dorsal third of the chest
10th rib space at costochondral junction
13th rib space at costochondral junction
4th rib space at costochondral junction
Answer: 7th rib space at costochondral junction
Explanation
Thoracocentesis can be performed at different locations; however, the 7th rib space at the level of the costochondral junction is the most appropriate answer available. The 4th rib space is near the heart, whereas the 10th or 13th rib space involves the caudal aspect of the thorax. This 7th rib space is a good choice because it is one of the more dependant regions where fluid will tend to accumulate; it is also caudal to where the heart should sit and well cranial to the diaphragm. When available, ultrasound guidance should be used to guide placement.
*** PowerPage: Pneumonia and Pleuropneumonia
The proper site for thoracocentesis in a horse suspected of pleuropneumonia with pleural effusion, when ultrasound is not available, is the 7th rib space at the costochondral junction. This location is optimal because it is a dependent region where fluid accumulates and is safely positioned away from the heart and diaphragm.
Comprehensive NAVLE Study Guide: Equine Pleuropneumonia
Definitions and Etiology
• Pleuropneumonia: A severe, often polymicrobial lung infection affecting the pleura.
• Causative Agents: Primarily Streptococcus equi subsp. zooepidemicus, Pasteurellaceae, anaerobes like Bacteroides, Fusobacterium spp.
• Predisposing Factors: Long-distance transportation, strenuous exercise, anesthesia, viral infections, and aspiration.
Pathophysiology
• Initial Stage: Aspiration of oropharyngeal organisms leading to lung infection.
• Disease Progression: The infection extends from the pulmonary parenchyma to the pleura.
• Stages:
• Subacute: Early bacterial proliferation, primarily facultative anaerobes.
• Acute: Pneumonia and pleuritis with severe inflammation.
• Chronic: Anaerobic bacteria dominate, leading to abscesses, necrosis, and poor prognosis.
• End-Stage: Irreversible damage with bronchopleural fistulae and fibrosis.
Clinical Signs
• Acute Signs: Lethargy, fever, pleurodynia (pleural pain), dyspnea, malodorous breath.
• Chronic Signs: Weight loss, ventral edema, persistent coughing.
Diagnosis
• Physical Exam: Thoracic auscultation, percussion, and observation of clinical signs.
• Laboratory Tests:
• Haematology: Leukocytosis or neutropenia with toxic neutrophils.
• Bacteriology: Transtracheal aspiration, thoracocentesis for culture.
• Imaging: Thoracic radiography and ultrasonography for pleural effusion and lung abscesses.
Medications
• Antibiotics:
• Penicillin: Effective against Streptococcus and many anaerobes.
• Gentamicin: Targets Gram-negative aerobes but less effective in chronic cases.
• Metronidazole: For penicillin-resistant anaerobes.
• Ceftiofur: A broad-spectrum cephalosporin for Gram-negative coverage.
• Dosages: Dependent on the stage and severity; typically administered intravenously.
• Adjunct Therapies:
• NSAIDs (e.g., Flunixin Meglumine): For inflammation and endotoxemia.
• Bronchodilators: Limited use; examples include Clenbuterol and Isoproterenol.
• Mucolytics: Limited data; Bromhexine and Dembrexine suggested.
• Drainage: Essential for pleural effusion management.
Treatment Protocols
• Early Stage: Aggressive antibiotic therapy with thoracic drainage.
• Chronic Disease: Involves more intensive treatments, including potential thoracotomy and long-term antibiotic use.
• Prognosis: Best with early intervention; worsens significantly with chronic or anaerobic infections.
Important Considerations
• Anaerobic Infections: Anaerobes often signify poor prognosis; managing these requires specific antibiotics like metronidazole.
• Supportive Care: Includes fluids, nutritional support, and potentially corticosteroids for inflammation.
Which of the following is the most common etiologic agent causing pneumonia in foals?
Streptococcus spp.
Actinobacillus equuli
Bordetella bronchiseptica
Mycoplasma spp.
Answer: Streptococcus spp.
Explanation
The most correct answer is Streptococcus spp. Streptococcus is a common cause of pneumonia in both foals and in adult horses; however, polymicrobial infections are also common. Other common bacterial isolates associated with pneumonia include E. coli, Klebsiella sp, and various anaerobic bacteria. Rhodococcus (Corynebacterium) equi is also a common cause of pneumonia in foals 2-6 months of age. Actinobacillus can be associated with pneumonia, but the other two answers are not commonly isolated from equine pneumonia.
***PowerPage: Top 9 Equine Respiratory Diseases
Which of these viruses are normally found in the upper respiratory tract of the horse?
Equine influenza
Equine viral arteritis virus
Equine adenovirus
Equine herpesvirus
Answer: Equine adenovirus
Explanation
The correct answer is equine adenovirus. Adenovirus is normal in the upper respiratory tract but can cause a lower respiratory tract infection in immunocompromised individuals, particularly foals with failure of passive transfer or combined immunodeficiency. In fact, adenovirus is the most common cause of death in foals with those two conditions, leading to an often fatal pneumonia.
You are performing endoscopy of the guttural pouch of a 6 year old Quarter Horse gelding presented for dysphagia. What is the most likely causative organism?
Histoplasma
Aspergillus
Coccidioides
Cryptococcus
Answer: Aspergillus
Explanation
Aspergillus is the most commonly identified fungal pathogen in guttural pouch mycosis. While this disease can present with epistaxis, dysphagia is sometimes a presenting complaint. Remember, cranial nerves IX, X, XI, and XII travel through the pouch and may be damaged from mycotic lesions, thus resulting in dysphagia. If you are unfamiliar with endoscopic images of the equine guttural pouch, the mycotic lesion is seen from approximately 1 to 7 o’clock while the stylohyoid bone is evident in the left side of the image.
**PowerPage: Guttural Pouch Disease
**PowerLecture: Neurologic Disorders
A Thoroughbred racehorse presents to you for having poor performance, stopping at the ends of races, and having labored breathing. After races, the horse swallows excessively and will sometimes cough. What is your most likely diagnosis?
Dynamic airway collapse
Exercise-induced pulmonary hemorrhage
Congestive heart failure
Large airway obstruction
Answer: Exercise-induced pulmonary hemorrhage
Explanation
The correct answer is exercise-induced pulmonary hemorrhage. This has multiple other names, and horses with this condition are sometimes referred to as bleeders or as bobbling, chocking, or gurgling. It is thought to be extremely common in Thoroughbreds. In this condition, following exercise at speed and large efforts from the lungs, pulmonary damage occurs and bleeding starts, usually in the caudal dorsal lung lobes. Common clinical signs are excessive swallowing after exercise because the horse is swallowing blood that was brought up. They may also cough to clear blood from their airways. Epistaxis is actually only seen in about 10% of horses with exercise-induced pulmonary hemorrhage. The other options in this question such as airway disease and heart failure would not be consistent with this horse’s excessive swallowing after racing.
***PowerLecture: Respiratory Diseases
The most likely diagnosis for a Thoroughbred racehorse with poor performance, labored breathing, excessive swallowing, and occasional coughing after races is exercise-induced pulmonary hemorrhage (EIPH). EIPH, common in Thoroughbreds, involves pulmonary damage and bleeding, typically in the caudal dorsal lung lobes, following intense exercise. Clinical signs include excessive swallowing due to blood in the airways, though epistaxis is seen in only about 10% of cases.
Exercise-Induced Pulmonary Hemorrhage (EIPH) in Horses: NAVLE Study Guide
Definitions and Causative Agents
• EIPH: The presence of blood in the airways of horses after strenuous exercise, commonly detected by tracheobronchoscopy or bronchoalveolar lavage (BAL).
Pathophysiology
• Mechanism: High intravascular pressures during exercise lead to capillary stress failure in the lungs, causing hemorrhage. Lesions predominantly occur in the caudodorsal lung fields.
• Progression: EIPH is progressive, with repeated episodes leading to pulmonary fibrosis, vascular remodeling, and potentially chronic lung damage.
Clinical Findings
• Signs: Visible epistaxis, poor performance, and subtle signs like coughing or increased respiratory rate.
• Lesions: Hemosiderin deposition, fibrosis, and venous remodeling in affected lung regions.
Diagnosis
• Primary Tests: Endoscopic examination post-exercise is the gold standard. BAL can identify red blood cells and hemosiderophages.
• Imaging: Ultrasonography and radiography can detect lung changes, though with variable sensitivity.
Treatment and Prevention
• Furosemide: Administered IV 4 hours before exercise; it reduces pulmonary pressures, decreasing the severity and incidence of EIPH.
• Management: Includes the use of nasal strips and minimizing exposure to dust and irritants. Horses with severe EIPH may require rest and modification of training regimens.
Prognosis
• Impact on Performance: Severe EIPH (Grade 4) is associated with shorter racing careers and poorer race outcomes. Horses with less severe EIPH (Grades 1-3) can still perform well with proper management.
• Long-Term Effects: Repeated episodes may lead to significant lung damage and reduced athletic capacity.
Key Points for Veterinary Professionals
• Early Detection: Regular monitoring using endoscopy or BAL in at-risk horses.
• Prophylaxis: Furosemide remains the primary intervention, though its use is controversial due to potential performance-enhancing effects.
• Ongoing Research: Understanding of EIPH is still evolving, with continued research into its pathogenesis and management.
https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/jvim.12593?download=true&campaigns=[{“position”:”ereader-last-page”,”uri”:”uri:707b1a3c-73e6-4188-b21f-2b05b70307d8”},{“position”:”ereader-first-page”,”uri”:”uri:7691ea89-90f5-4086-9241-486673caed61”}]
Many horses in a large group develop a rapid-onset high fever, weakness, depression, and cough. What step is most likely to lead you to a definitive diagnosis?
Perform a transtracheal wash for bacterial culture
Take thoracic radiographs of several affected horses
Perform serologic testing for antibodies to common respiratory pathogens
Euthanize several affected horses and perform gross necropsies
Take nasopharyngeal swabs for viral isolation
Answer: Take nasopharyngeal swabs for viral isolation
Explanation
The correct answer is to acquire nasopharyngeal swab for viral isolation. Given the history of a rapidly-spreading infection with fever and cough, the most likely differential is equine influenza. This is caused by an orthomyxovirus. Other less likely rule-outs include equine viral rhinopneumonitis and equine viral arteritis. The way to definitively diagnose this is with viral isolation; a nasopharyngeal swab is the best sample. Growth in a bacterial culture would be more likely to indicate a secondary infection than a primary pathogen. Serology could be useful, but because influenza is so ubiquitous, paired titers are really needed to yield a diagnosis. Gross necropsy findings with influenza are fairly minimal and variable. Thoracic radiographs would not give you a diagnosis.
***PowerPage: Top 9 Equine Respiratory Diseases
The best step to definitively diagnose a rapidly spreading respiratory infection with fever and cough in a large group of horses is to take nasopharyngeal swabs for viral isolation. The most likely cause is equine influenza, caused by an orthomyxovirus. Viral isolation from a nasopharyngeal swab is more reliable than bacterial culture, serology, necropsy, or thoracic radiographs.
Comprehensive Information on Equine Influenza for BCSE Test
1. Definitions:
• Equine Influenza (EIV): A highly infectious respiratory disease caused by the influenza A virus.
- Causative Agents:
• Orthomyxovirus: Specifically A/equine type-2 (H3N8), first recognized in 1963. - Epidemiology:
• Transmission: Direct inhalation of respiratory secretions, fomites. Epidemics arise from newly introduced infected horses.
• Hosts: Primarily affects horses aged 1-5 years. - Clinical Findings:
• Symptoms: High fever (up to 106°F), depression, anorexia, serous nasal discharge, dry harsh cough, submandibular lymphadenopathy.
• Course: Symptoms appear within 1-3 days post-exposure, lasting under 3 days in uncomplicated cases. Severe cases may take up to 6 months to recover. - Pathophysiology:
• Viral Replication: Occurs within respiratory epithelial cells, leading to destruction of tracheal and bronchial epithelium.
• Complications: Secondary bacterial infections like pneumonia, chronic bronchitis, and pleuropneumonia due to compromised respiratory defenses. - Diagnosis:
• Definitive Tests: RT-PCR, viral isolation from nasopharyngeal swabs, stall-side immunoassays, antigen-capture ELISA, serology.
• Sampling: Nasopharyngeal swabs early in illness (1-2 days post-onset). - Treatment:
• Supportive Care: Rest, NSAIDs for fever control, antibiotics for secondary bacterial infections.
• Rest Period: 1 week of rest for every day of fever, minimum 3 weeks. - Prevention:
• Biosecurity: Isolation of new or sick horses, hygiene practices.
• Vaccination: Inactivated and modified-live vaccines; biannual boosters for high-risk horses. Intranasal vaccines provide rapid protection. - Medications:
• NSAIDs: Control fever and inflammation.
• Examples: Flunixin meglumine, phenylbutazone.
• Antibiotics: For secondary bacterial infections.
• Examples: Trimethoprim-sulfamethoxazole, penicillin. - Key Points:
• Vaccination and Biosecurity: Crucial for prevention and control of outbreaks.
• EIV vs. Other Respiratory Diseases: Rapid spread, high fever, and severe cough help differentiate from other viral infections like EHV-1 and EHV-4.
https://www.merckvetmanual.com/respiratory-system/respiratory-diseases-of-horses/equine-influenza
You are out in the field and you notice a horse tilt his head up and curl back his lips in a manner that makes it appear to be “grimacing”. You identify this as a flehmen response. What is thought to be happening when this response occurs?
This is a sign of sexual interest or arousal and you need to be careful if the horse is nearby
This is a sign of colic
This is a pathognomonic sign of yellow star thistle toxicity
Scents are moved to the vomeronasal organ
This is a display of aggression or dominance that a horse will display when it detects the presence of other stallions
Answer: Scents are moved to the vomeronasal organ
Explanation
The flehmen response, as described in the question, helps animals trap pheromone scents in the vomeronasal organs (VNOs) so they can be analyzed more closely. Pheromones are the chemical signals emanating from other animals.
When a horse draws in an organic odor, he curls up his lip to temporarily close the nasal passages and hold the particles inside. The upward head tilt seems to help the airborne molecules linger in the VNOs, which are located under the floor of the horse’s nasal cavity.
While sex pheromones are the most common flehmen trigger, they are not the only ones, and the response itself does not indicate sexual interest.
You are examining a 3 year old Thoroughbred gelding that just completed a race and notice discharge from the nostrils. What would be an appropriate treatment for this horse prior to the next race?
Furosemide
Plasma transfusion to replace clotting factors
Vitamin K
Vasopressin
Whole blood transfusion
Answer: Furosemide
Explanation
In this instance, the discharge is blood, with the most likely diagnosis being exercise-induced pulmonary hemorrhage (EIPH). One of the most commonly administered medications for EIPH is furosemide, which seems to decrease the incidence or lessen the severity of bleeding. The exact mechanism by which this occurs is not completely known but may be associated with reduced pulmonary capillary pressure.
***PowerPage: Exercise Induced Pulmonary Hemorrhage
You suspect that an 18-year-old Quarter Horse mare has recurrent airway obstruction (RAO, also known as chronic obstructive pulmonary disease) based on clinical signs of increased respiratory rate and effort, expiratory wheezes on auscultation, and the age of the horse. What cytologic finding of bronchoalveolar lavage (BAL) fluid would be supportive of RAO?
Neutrophilic inflammation
Mononuclear inflammation
Eosinophilic inflammation
Mixed inflammatory response (neutrophils, macrophages, and eosinophils)
Answer: Neutrophilic inflammation
Explanation
In health, BAL fluid primarily consists of macrophages. However, in RAO, neutrophils are the predominant cellular finding. RAO typically affects older horses and is a response to environmental allergens. The classic case is the horse that is stalled in the winter and possibly housed in the vicinity of the hay storage. When the horse is exposed to hay allergens (via inhalation), bronchoconstriction and neutrophilic inflammation occur resulting in clinical signs.
** PowerPage: Recurrent Airway Obstruction
** PowerLecture: Respiratory Diseases
The presence of neutrophilic inflammation in bronchoalveolar lavage (BAL) fluid is supportive of recurrent airway obstruction (RAO) in horses. RAO, often triggered by environmental allergens like hay dust, primarily affects older horses and leads to bronchoconstriction and neutrophilic inflammation, resulting in increased respiratory effort and expiratory wheezes.
Comprehensive NAVLE Study Guide: Recurrent Airway Obstruction (RAO) in Horses
Definitions and Etiology
• Recurrent Airway Obstruction (RAO): Also known as heaves, previously termed chronic obstructive pulmonary disease (COPD), a hypersensitivity-mediated, chronic respiratory condition in horses characterized by airway inflammation and obstruction.
• Causative Agents: Organic dust, including bacterial endotoxins, molds (Aspergillus fumigatus, Faenia rectivirgula), peptidoglycans, microbial toxins, forage mites, and other airborne particles commonly found in stables.
• Predisposing Factors: Age (≥4 years), breed (Thoroughbreds), winter and spring seasons, poor ventilation, and hay or straw exposure.
Pathophysiology
• Inflammatory Response: Inhaled antigens trigger a delayed hypersensitivity reaction, leading to an influx of neutrophils, mucus accumulation, bronchospasm, and airway hyper-reactivity.
• Chronic Changes: Persistent exposure results in airway remodeling, including smooth muscle hyperplasia, thickening of the airway walls, mucus hypersecretion, and airway obstruction.
Clinical Signs
• Acute Exacerbations: Increased expiratory effort, coughing, nasal discharge, exercise intolerance, and labored breathing with flared nostrils.
• Chronic Cases: Persistent cough, weight loss, and decreased performance. Some horses may develop a “heave line” due to hypertrophy of the abdominal muscles used for forced expiration.
Diagnosis
• History and Clinical Signs: Chronic cough, dyspnea, and history of exposure to dusty environments.
• Endoscopy: Visual confirmation of mucus accumulation in the trachea.
• Bronchoalveolar Lavage Fluid (BALF) Cytology: Increased neutrophils (>25%), reduced macrophages and lymphocytes.
• Lung Function Tests: Measurement of lung resistance, dynamic compliance, and work of breathing. Impulse oscillometry is the most commonly used method.
Treatment
• Environmental Management: Essential for controlling RAO; includes minimizing dust exposure by using low-dust bedding, feeding soaked or pelleted hay, and improving stable ventilation. • Medications: • Corticosteroids: First-line treatment to reduce airway inflammation. • Oral Prednisolone: Bioavailability-dependent, used to reduce airway neutrophilia. • Dexamethasone: Administered orally or intravenously, effective in severe cases. • Inhaled Corticosteroids: Beclomethasone, budesonide, fluticasone; used to deliver high concentrations locally with fewer systemic side effects. • Bronchodilators: • Beta-2 Agonists: Clenbuterol (oral), albuterol (inhaled) for short-term relief of bronchospasm. • Anticholinergics: Ipratropium, glycopyrrolate, and atropine for acute bronchodilation. • Adjunct Therapies: Antioxidants like ascorbic acid and mucolytics for supportive care.
Prevention and Management
• Stable Management: Maintaining a dust-free environment is crucial. Horses should be kept outdoors when possible, or in well-ventilated stables with minimal exposure to organic dust.
• Monitoring and Follow-Up: Regular assessment of lung function, airway inflammation, and response to treatment through BALF cytology and lung function tests.
Complications
• Chronic Airway Remodeling: Prolonged inflammation can lead to irreversible changes, making management more challenging and increasing the risk of recurrent episodes.
• Secondary Infections: Due to compromised airway defenses, horses may be more susceptible to bacterial infections.
Prognosis
• With Early Intervention: Good prognosis with appropriate environmental management and treatment. However, horses with chronic or severe RAO may have a poorer prognosis and require ongoing management.
You are examining a 4 month old Thoroughbred colt with a 2 week history of weight loss, fever, and increased respiratory rate. You suspect pneumonia and notice the pictured lesion on thoracic ultrasonography. What is the most likely cause?
Streptococcus zooepidemicus pneumonia
E. coli pneumonia
Rhodococcus equi pneumonia
Equine Herpes Virus pneumonia
Answer: Rhodococcus equi pneumonia
Explanation
R. equi is the most likely cause resulting in pulmonary abscess formation that may be noticed on thoracic ultrasound. In the ultrasound image, you should note the capsular structure with an anechoic center which represents a fluid-filled abscess. R. equi is typically observed in older foals (2-6 months 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. Ultrasonography 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.
** PowerPage: Rhodococcus equi
** PowerLecture: Rhodococcus equi
A 2-year old Standardbred gelding presents for a prepurchase exam. On auscultation you hear a loud grade IV/VI systolic murmur on the right thorax. An echocardiogram is performed, which is shown below. The cardiac chambers are labeled LV (left ventricle), RV (right ventricle), Ao (Aorta). What is your diagnosis?
Ventricular septal defect
Tricuspid valve endocarditis
Unremarkable echocardiogram
Patent ductus arteriosus
Subaortic stenosis
Answer: Ventricular septal defect
Explanation
The correct answer is ventricular septal defect. There is echo dropout immediately below the aortic valve and extending into the right ventricle. The auscultatory findings also fit with a VSD as the murmur is typically louder on the right. A PDA would cause a continuous heart murmur. There is no narrowing in the LV outflow tract so subaortic stenosis is not evident. There is no evidence of a vegetation or mass on the tricuspid valve so endocarditis is not correct.
A 2-year-old Standardbred gelding with a grade IV/VI systolic murmur on the right thorax and an echocardiogram showing echo dropout below the aortic valve into the right ventricle is diagnosed with a ventricular septal defect, characterized by louder murmurs on the right and distinct from PDA, subaortic stenosis, or tricuspid valve endocarditis.
The owner of a weanling colt has asked for a pre-purchase examination to be performed on her 4 month old colt. The colt appears in good health based on physical examination with the only abnormality noted being a holosystolic murmur heard best on the right side of the thorax. What is your diagnosis based on auscultation and echocardiographic findings (see image; long-axis view from left side)?
Patent ductus arteriosus (PDA)
Truncus arteriosus
Ventricular septal defect (VSD)
Atrial septal defect (ASD)
Answer: Ventricular septal defect (VSD)
Explanation
The image demonstrates a VSD or a hole in the intraventricular septum (identified by two markers). This is one of the more common congenital defects of the heart in horses.
The murmur occurs as blood is shunted from the left side of the heart to the right during systole. Some horses can perform normally with a VSD while others, with large defects, can demonstrate heart failure. In this case, it was an incidental finding, as the horse was bright and alert at the time of exam. The remainder of the answers (ASD, PDA, and truncus arteriosus) can occur but are less common and would appear differently on echocardiography.
It is unlikely but possible that you will be asked to interpret an echocardiogram on your board exam. If you are, this is likely to be one of the diseases you could be shown.
Ventricular septal defect (VSD) is the diagnosis based on auscultation and echocardiographic findings. VSD is a common congenital heart defect in horses, characterized by a holosystolic murmur on the right side due to blood shunting from the left to the right ventricle during systole. While some horses with VSD can perform normally, larger defects can lead to heart failure. In this case, the defect was an incidental finding, as the colt appeared healthy. Other congenital defects like ASD, PDA, and truncus arteriosus are less common and present differently on echocardiography.
The most common congenital cardiac abnormality in the horse is depicted below, what is it?
Ventricular septal defect
Tetralogy of Fallot
Patent ductus arteriosus
Pulmonic stenosis
Answer: Ventricular septal defect
Explanation
The correct answer is ventricular septal defect. Clinically, you will hear a murmur bilaterally with the point of maximum intensity on the right side. A patent ductsus arteriosus will create a characteristic continuous machinery or washing machine murmur. This will be audible throughout systole and diastole. Additionally, the point of maximum intensity is usually on the left side between the 3rd and 4th intercostal space. When listening to a tetralogy of Fallot, one can expect a loud holosystolic murmur on the left 4th-6th intercostal space. This congenital anomaly is rather rare and will automatically be lower on your differential list. Just to review, the tetralogy of Fallot consists of an overriding aorta, ventricular septal defect, pulmonic stenosis, and right ventricular hypertrophy.
Ventricular septal defect is the most common congenital cardiac abnormality in horses. It typically presents with a murmur heard bilaterally, with the point of maximum intensity on the right side. In contrast, a patent ductus arteriosus produces a continuous “machinery” murmur, most audible on the left side. Tetralogy of Fallot, which is rarer, involves a loud holosystolic murmur on the left side and includes an overriding aorta, VSD, pulmonic stenosis, and right ventricular hypertrophy. Pulmonic stenosis alone is less commonly seen in horses.
The two tracings show a horse (top) and a cow (lower) ECG with irregular QT intervals and absence of P waves. What cardiac disorder is this indicative of?
Atrial Fibrillation
Ventricular tachycardia
Ventricular fibrillation
Myocarditis
Pericarditis
Answer: Atrial Fibrillation
Explanation
These changes are typical of atrial fibrillation. Note that the horse tracing (top) also shows fibrillation waves.
A 6 year old Saddlebred is presented for lethargy, anorexia and fever. Upon physical exam, you determine that the heart rate is approximately 90 beats/min. You quickly perform an ECG using the base-apex lead (see top image). What is the arrhythmia that you observe on the ECG (also consider what medication you would use to treat this arrhythmia)? (The bottom ECG strip is a normal rhythm for reference.)
Ventricular bigeminy
Ventricular fibrillation
Atrial fibrillation
Ventricular tachycardia
Answer: Ventricular tachycardia
Explanation
The rhythm noted is ventricular tachycardia. You can tell that the horse has tachycardia when you compare the rate to the lower strip (~40 beats/min). Characteristics of ventricular tachycardia include QRS complexes that are wide, bizarre, and have no association with P-waves. However, you may see underlying P-waves occasionally within the rhythm (top strip) as the small positive deflections. The cause of the ventricular tachycardia in this horse was vegetative endocarditis; administration of lidocaine abolished the arrhythmia.
The arrhythmia observed on the ECG is ventricular tachycardia. This condition is characterized by wide, bizarre QRS complexes that lack association with P-waves, although occasional P-waves may be seen. The rapid heart rate of ~90 beats/min, compared to a normal rate (~40 beats/min), supports this diagnosis. In this case, the underlying cause was vegetative endocarditis, and lidocaine was the medication used to treat the arrhythmia by abolishing the ventricular tachycardia.
A 3-year-old Standardbred gelding presents with epiphora, blepharospasm, and severe pain of the right eye (see image). There are numerous treatment options. Which medication would be contraindicated for this case?
- Tropicamide
- Tobramycin
- Serum
- Banamine
- Neomycin and polymyxin B and dexamethasone (Neo-Poly-Dex)
- EDTA
Answer: Neomycin and polymyxin B and dexamethasone (Neo-Poly-Dex)
Explanation
The correct answer is Neo-Poly-Dex. This is an illustration of a melting ulcer. Any corneal ulcer, whether it is superficial or deep, can be perpetuated by steroid use such as the dexamethasone in this medication. Steroids increase protease activity causing the “melting” pathology, whereas, one of the primary goals in managing corneal ulcers is to decrease protease activity by using EDTA and serum.
Aggressive topical antibiotic use is also essential. Tobramycin, gentamicin, and neomycin-polymyxin B-bacitracin, among others are appropriate. Intravenous banamine is the drug of choice for ocular pain and inflammation in horses.
Tropicamide is used for its mydriatic and cycloplegic effect because all animals with corneal ulcers have uveitis.
Atropine is an alternative to tropicamide. It is important to note, even though atropine has a longer duration of action than tropicamide, atropine must be used with extreme caution in horses as it may potentiate colic.
You are presented with an 8-month old Quarter horse filly with a chronic history of urinary incontinence. The image provides one of the findings on physical examination. The remainder of the physical exam, along with a CBC and chemistry profile, is normal. What is the most likely cause of these signs in this filly?
- Equine herpes virus myeloencephalopathy
- Equine protozoal myelitis (EPM)
- Severe urinary tract infection
- Ectopic ureter
Answer: Ectopic ureter
Explanation
Urine scalding, as pictured, along with the age and gender of this patient, would lead to a high suspicion of an ectopic ureter. While this is a comparatively rare problem, it is the most common congenital anomaly of the equine urinary tract. Nearly 90% of the cases reported are fillies, with the primary complaint of urinary incontinence and urine scalding (dermatitis). Surgical correction has been successful. The chronic history in a young animal makes primary urinary tract infection less likely.
This 5 year old Standardbred mare in the picture presents for lameness in the right hind limb. There is a jerking motion as she moves the leg forward. On physical exam, you are able to extend the hock and flex the stifle simultaneously. What is your diagnosis?
- Achilles tendon rupture
- Bog spavin
- Stringhalt
- Gastrocnemius rupture
- Peroneus tertius rupture
Answer: Peroneus tertius rupture
Explanation
The correct answer is peroneus tertius rupture. Damage to the peroneus tertius muscle disrupts the stay apparatus of the hind limb. The characteristic diagnostic feature is the ability to extend the hock and flex the stifle simultaneously because an intact peroneus tertius prevents this.
***PowerPage: Top 9 Equine Lameness
Rupture of the Fibularis (Peroneus) Tertius in Horses
The fibularis (peroneus) tertius is a tendinous structure that originates from the extensor fossa of the femur and runs over the craniolateral aspect of the tibia to insert on the dorsoproximal aspect of the third metatarsal bone, the calcaneus, and the third and fourth tarsal bones. It is part of the reciprocal apparatus of the hindlimb, which means there is concurrent flexion and extension of the hock and stifle. Rupture of the fibularis tertius may occur as a result of hyperextension of the limb and usually occurs in the middle of the crus, or laceration may occur on the dorsal aspect of the tarsus. Avulsion of the origin on the fibularis tertius is rare in mature horses but may occur in young animals.
Clinical signs are pathognomonic, because rupture of the fibularis tertius means horses are able to extend the hock while the stifle is flexed. Horses are able to bear weight on the affected limb. At walk, the gastrocnemius and superficial digital flexor muscles appear rather flaccid, and there is a characteristic dimple on the caudodistal aspect of the soft tissues of the crus. At trot, an obvious lameness is usually evident, with delayed protraction of the limb due to overextension of the hock.
Diagnosis is usually based on clinical signs and can be confirmed with ultrasonography.
Conservative treatment with 3-4 mo of stall rest followed by slow and careful reintroduction to exercise usually results in complete resolution of signs and return to athletic soundness.
(Merck Manual: Peritoneus T Rupture) [https://www.merckvetmanual.com/musculoskeletal-system/lameness-in-horses/rupture-of-the-fibularis-peroneus-tertius-in-horses?query=Peroneus%20tertius%20rupture]
An 8-year old Clydesdale gelding presented to you for a 7 day history of pruritus of the distal limbs, particularly the feathered areas of the leg (see image). Upon further examination, you observe irritation, scabbing, and alopecia of the fetlock region likely due to self-induced trauma secondary to pruritus. The horse is restless and bites at the distal limbs frequently. What is the most likely diagnostic test to lend a diagnosis in this case?
- Intradermal skin testing to detect insect hypersensitivity
- Elimination diet to detect food allergy
- Skin scraping and microscopic examination of affected areas to detect Chorioptes
- Skin punch biopsy to detect pemphigus foliaceus
- Intradermal skin testing to detect Onchocerca hypersensitivity
Answer: Skin scraping and microscopic examination of affected areas to detect Chorioptes
Explanation
The correct answer is skin scraping to identify the Chorioptes mite on microscopic examination. Chorioptic mange is caused by infestation with Chorioptes equi; this mite typically affects the distal limb region but can also extend to the ventral abdomen. Draft horses are particularly susceptible because of their long feathered hair coat of the distal limbs. Chorioptes is more common in the winter months and causes intense pruritus.
In regard to the other answers, intradermal skin testing is sometimes used to detect insect hypersensitivity, but insect hypersensitivity typically affects the trunk or ventral abdomen. Food allergies are not a major cause of dermatologic diseases in the horse and pemphigus is a generalized disease. Onchocerca can cause pruritus, but is diagnosed via skin biopsy or response to ivermectin therapy.
You are examining a 5-year old pony for lethargy, anorexia, and mild intermittent colic. Upon physical examination, you notice the abnormal finding in the image. Consumption of which of the following can produce these clinical signs and physical examination findings?
- Red maple leaves (Acer rubrum)
- Black walnut (Juglans nigra)
- Yellow star thistle (Centaurea solstitialis)
- Oak leaves and acorns (Quercus sp)
Answer: Red maple leaves (Acer rubrum)
Explanation
The sclera appears icteric. In combination with the clinical signs, ingestion of Red maple leaves would result in these signs due to hemolysis and low oxygen content of the blood. Oak is toxic but causes diarrhea and abdominal pain, whereas Black walnut is associated with laminitis. Yellow star thistle causes nigropallidal encephalomalacia resulting in CNS signs.
