Week 2 Feb 17 Day 2 Flashcards
If a horse is in seasonal anestrus, which of these is the most effective means of hastening the start of the breeding season?
The correct answer is to provide 16 hours of artificial light 60 days prior to the start of breeding. To get a horse to transition out of seasonal anestrus, you can gradually increase the amount of light to 15-16 hours per day to initiate ovarian activity. It usually takes at least 60 days until physiologic breeding will occur. There are hormonal methods to promote cycling, but they are less consistent than altering light.
In a foal with uroperitoneum, the creatinine in the abdominal fluid will be at least ____________ as much as the serum creatinine.
The correct answer is twice. This finding is diagnostic for a uroperitoneum. In a foal, this is usually due to urinary bladder rupture at the time of parturition due to large pressures exerted on the urinary bladder during parturition.
Topic: Entropion in Horses
The correct answer is entropion. This is a common condition in foals where the lower eyelid is inverted and can cause conjunctivitis or keratitis. The condition will usually correct spontaneously but sometimes will require treatment to evert the lid. One method for this is to use a local anesthetic, mechanically evert the lid, and staple it. Alternatively, surgical correction can be performed but is rarely indicated. Ectropion is the opposite condition where the eyelid everts out and can lead to exposure keratitis, but this is uncommon in horses. Ocular onchocerciasis is caused by microfilariae and is seen in about 50% of horses with cutaneous onchocerciasis.
Topic: Pemphigus Foliaceus
The correct answer is immune suppressive doses of corticosteroids. Pemphigus foliaceus is an
autoimmune disease in which antibodies are formed against the intercellular adhesin proteins. In
horses, this disease causes crusting lesions of the head, limbs, and ventrum. Definitive diagnosis is
found on biopsy of the skin showing acantholysis. There are two forms of the disease in horses. The
juvenile form may result in spontaneous remission and carries a good prognosis. The adult form of the
disease carries a worse prognosis.
Topic: Potomac Horse Fever
The correct answer is Neorickettsii risticii, the causative agent of Potomac Horse Fever (PHF). The clues that best indicate PHF are the time of year (disease usually occurs in the summer in the northern states), the high fever and diarrhea, and the presence of laminitis. The horse is also dehydrated and has a profound leukopenia, both consistent with PHF. Salmonella also causes diarrhea and leukopenia, and could be a viable choice, but Salmonella can occur at any time of the year; moreover, laminitis is not as often seen with Salmonella. This question has a practical aspect to it as horses often present with the described history and physical examination findings, and the veterinarian has to decide if he or she wants to treat specifically for PHF; the drug of choice is oxytetracycline. In this clinical situation, you as a veterinarian would have to start treatment empirically as your PCR test will take several days to get results. The good news is that PHF is very susceptible to oxytetracycline.
List the parameters for DIC diagnosis
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.
What are the classic electrolyte changes seen in horses with chronic renal failure?
hyponatremia, hypochloremia, hyperkalemia, and azotemia.
Somewhat unique to the horse, hypercalcemia is noted because of the high amounts of calcium present in the diet. Serum phosphorus levels may be low because of the high calcium.
When is a placenta considered “retained” in a horse? What do you do to treat it?
Most texts state that the placenta in a mare is retained after greater than 3 hours post-parturition; therefore, this would be considered a retained placenta. Oxytocin, along with uterine lavage, will cause the uterus to contract and facilitate expulsion of the placenta. Strong physical traction on the retained placenta is generally considered contraindicated, as you may tear the placenta and leave remnants of it within the uterus, resulting in possible complications. Broad-spectrum antimicrobials are often administered to decrease the incidence of metritis but alone would not be appropriate.
What does the auriculopalpebral nerve block in the horse?
It disrupts motor innervation to the orbicularis oculi
The owner of an American Paint Horse that is frame overo has bred her horse to a Tobiano horse. The carrier rate for the autosomal recessive disease, ileocolonic aganglionosis (overo lethal white foal syndrome) is 90% in frame overo and 20% in Tobiano horses.
Based on these rates, what is the likelihood that the foal born from this mating will be affected by the disorder?
Because the trait is recessive, homozygotes will be the only individuals affected. In order for a foal to be born homozygous for the trait, BOTH parents MUST be carriers. The chances of both parents being
carriers is 90% x 20% (or 0.9 x 0.2) = 0.18 or 18%.
For any autosomal recessive trait, if both parents are carriers, the offspring will have a 25% chance of being homozygous and affected by the disease.
In this example, there is an 18% chance that both parents are heterozygous carriers for the disease.
Applying the 25% rate of passage of both diseased alleles, (0.18 × 0.25) = 0.045, or there is 4.5% chance that the foal will be affected.
Topic: Dermatophilosis in Horses
The answer is dermatophilosis. Dermatophilus congolensis is a gram positive, non-acid fast, facultative anaerobic actinomycete. It causes a crusting dermatitis in large animals when there is high moisture on the skin as well as mechanical irritation. Horses with long, wet haircoats are often affected. Lesions are commonly on the dorsum and pasterns of horses and are classically described as paintbrush lesions. It can be diagnosed with a direct smear preparation. Treatment includes keeping the haircoat clean and dry and penicillins if the lesions are severe. Lesions typically heal rapidly.
Dermatophilus has a classic “railroad track” appearance on cytology due to the long branching chains of gram positive cocci.
Topic: C. dificile Facts
The 2 main virulence toxins are toxin A and toxin B.
Transmission of C. difficile occurs via the oral-fecal route.
C. difficile is a Gram-positive, rod shaped, obligate anaerobe.
C. difficile can survive for prolonged periods of time in the spore form.
Risk factors for the development of disease include antibiotic treatment and hospitalization, but does not include administration of NSAIDs.
What is a centrally acting muscle relaxant used in horses?
Guaifenesin
Ketamine is a dissociative agent and is known for its ability to cause hypertonia. Atracurium is a non-depolarizing neuromuscular blocking agent that acts by competitively binding to cholinergic receptors at the motor endplate.
Succinylcholine is a depolarizing neuromuscular blocking agent.
Topic: Vesicular Stomatitis
VS affects horses, cattle and pigs with similar clinical signs. It is a viral disease of high morbidity and
low mortality that appears about every 7 to 10 years in the Southwestern United States. Yearly
outbreaks occur in southern Mexico and northern South America. Black flies and midges appear to be
the vectors. Affected premises should be quarantined.
Topic: Combined Immunodeficiency
The correct answer is Arabian. Arabian foals can develop combined immunodeficiency (CID) characterized by a lack of production of functional lymphocytes. No curative treatment exists, and foals will succumb to infection. In a CID foal, the foal typically has immunity from maternal antibodies for the first few months of life. However, as maternal antibodies begin to wane after 2-3 months, foals with CID will begin to develop recurrent infections that are responsive to antimicrobials. Once antimicrobials are discontinued, infection returns. Owners should be advised on the heritable nature of this disease. A genetic blood test is available to determine if a horse is a carrier of the CID trait.
Upward patellar fixation causes the gait described above. Any horse that has the hind limb in rigid extension and is unable to flex it should be suspected of having this problem. One condition that can mimic this gait is luxation of the coxofemoral joint which can lead to an inability to flex the hind limb but this can be distinguished clinically because the limb will not be extended.
Normally, when horses are standing and resting their hindlimbs, the patella elevates to the top of the femoral trochlea, and the medial patellar ligament hooks over the medial ridge of the trochlea, locking the joint and allowing the horse to rest the limbs. To flex the stifle again, the quadriceps femoris muscle contracts, lifting the medial patellar ligament free of the medial trochlear ridge allowing the patella to return to its working position. When something prevents the horse’s ability to release the stifle, the condition is known as upward patellar fixation (also called “upward fixation of the patella” or
“locked stifle”).
Most cases of upward patellar fixation can be managed conservatively (exercise (physical therapy), improved body condition). In severe and unresponsive cases, surgery to cut the medial patellar ligament is an option.
Stringhalt is involuntary flexion of the hindlimb and is usually bilateral. The problem in this case is rigid extension. Stringhalt is treated with lateral digital extensor tenectomy.
Gonitis is a term indicating stifle arthritis. It is nonspecific to the underlying cause and could be due to osteochondrosis, ligament injury, or some other problem. Upward patellar fixation and its consequences could be referred to as gonitis but this is a less specific diagnosis in this case.
Jack spavin is a lay term for cunean bursitis or irritation of the cunean tendon as a result of bone growth on the medial hock.
Thoroughpin is the term for effusion of the tarsal sheath (sheath of the deep digital flexor).
Sacroiliac luxations in horses are generally considered untreatable. The condition will often stabilize with time and supportive care with rest and NSAIDs. Some horses may return to their previous level of activity or competitiveness but most have residual limitation. Reduction is not typically an option.
Total hip arthroplasty has been reported in horses but is typically reserved for severely injured horses
that do not improve with supportive care.
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.
Topic: Calf Diarrhea Part 2 Video
Negative Predicative Value
The correct answer is approximately 99%. The negative predictive value is the proportion of test-negative animals that are truly disease negative (unaffected) in this population. In the 2X2 table, where a= Disease +, Test +; b= Disease -, Test +; c= Disease +, Test -; d= Disease -, Test -. The NPV is d/(c+d), or disease -, test - animals DIVIDED by all of the test - animals.
The answer to the question has to consider the prevalence of mastitis in the herd, which here is 5%. As the prevalence declines, NPV will increase.
The negative predictive value gives a proportion of the negative tests that are truly negative. The value is the number of true negatives divided by the sum of the true negatives and false negatives.
In this herd, the proportion of test negative animals that actually is negative is specificity × (1-
prevalence) or (0.9)x0.95) = 0.855 (d). The proportion of false negatives in the herd is (1-sensitivity) x
prevalence, or (0.1)(0.05) = 0.005 (c).
Negative predictive value = d/c+d) = 0.855/(0.855+0.005) = 0.994.
What is the most common cause of pericarditis in cattle?
Traumatic reticuloperitonitis
A necropsy of an aborted bovine fetus shows enlarged lymph nodes and spleen, destructive lesions to the thymus, and evidence of chronic granulomatous infection. What is the most likely cause of this abortion?
The correct answer is epizootic bovine abortion (EBA), also called foothill abortion. EBA is an
important disease for beef producers in the foothill and mountainous regions of California, Northern
Nevada and Southern Oregon. The lesions described in the question are consistent with this diagnosis.
The etiologic agent of EBA is a bacteria, Pajaroellobacter abortibovis and the vector is a tick,
Ornithodoros coriaceus.
Topic: Johnne’s
You diagnose an Angus beef cow with ocular lymphoma. What should you recommend to the owners?
The correct answer is euthanasia. Meat from cattle affected with lymphoma cannot be used.
Treatment for the disease is economically unadvisable for beef cattle. Enucleation is not likely to cure the disease as it is likely systemic.
Topic: Calf diptheria
Also called necrotic laryngitis, or laryngeal necrobacillosis, this mainly feedlot condition strikes randomly but can result in death or a permanently misshapen larynx. The causes appear to be
Histophilus somni and Fusobacterium necrophorum.
in upper respiratory disease video
Some lupines contain alkaloids called sparteine and anagyrine. Cows eating lupine during early
gestation often give birth to calves with cleft palates, crooked legs and distorted/malformed spines.
Six of the poisonous species implicated in “crooked calf disease” are silky lupine (L. sericeus), tailcup
lupine (L. caudatus), velvet lupine (L. leucophyllus), silvery lupine (L. argenteus), lunara lupine (L.
formosus), and yellow lupine (L. sulphureus).
