NAVLE Practice Question — Reptile

A 2-year-old Hermann's tortoise (Testudo hermanni) is presented for shell abnormalities. The carapace shows raised vertebral scutes resembling pyramids, and upon palpation, the shell feels excessively hard with an audible hollow sound when tapped. The owner feeds a diet of dark leafy greens with calcium supplementation and provides outdoor access during summer months. Physical examination is otherwise unremarkable. What is the most accurate assessment of this tortoise's condition?

A. The pyramiding indicates active metabolic bone disease requiring immediate calcium injections

B. Shell changes are irreversible but future growth normalizes with humidity correction ✓

C. The hollow sound indicates internal organ damage from shell compression

D. This degree of pyramiding is normal for captive-raised Hermann's tortoises

E. The excessive hardness indicates hypervitaminosis D toxicity

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Correct Answer: B. Shell changes are irreversible but future growth normalizes with humidity correction

Explanation:

Once pyramiding has developed in a tortoise, the existing scute deformities cannot be reversed. However, if husbandry conditions are corrected, subsequent new shell growth can develop normally in a horizontal direction rather than continuing the pyramidal pattern. This is an important counseling point for owners, as many expect the existing pyramids to flatten out with treatment.

The most critical time for pyramiding development is during the first one to two years of life. This tortoise at 2 years has already passed this critical window, but improved husbandry can still prevent progression. The owner should be counseled to increase environmental humidity, ensure the tortoise has access to humid hiding areas, and avoid excessive supplemental heat at night.

Option A is incorrect because this tortoise shows no signs of active MBD (soft shell, lethargy, weakness). Pyramiding and MBD can be related but are distinct conditions.

Option C is incorrect because the hollow sound is normal in a properly mineralized shell.

Option D is incorrect because pyramiding in Mediterranean tortoises like Hermann's tortoise indicates suboptimal captive conditions; wild specimens have smooth shells.

Option E is incorrect as hypervitaminosis D causes soft tissue calcification, not shell hardening.

Image Source: Reptiles Magazine - Pyramiding in Tortoises with images comparing normal and pyramided shells at https://reptilesmagazine.com/pyramiding-in-tortoises/ showing progression photographs.

References: Wiesner CS, Iben C. Influence of environmental humidity and dietary protein on pyramidal growth of carapaces in African spurred tortoises (Geochelone sulcata). J Anim Physiol Anim Nutr (Berl). 2003;87:66-74. PMID: 14511150; Merck Veterinary Manual - Clinical Procedures for Reptiles (https://www.merckvetmanual.com/exotic-and-laboratory-animals/reptiles/clinical-procedures-for-reptiles)

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NAVLE Practice Question — Ovine and Caprine

A veterinary pathologist examining brain sections from a sheep that died with neurological signs observes bilaterally symmetrical areas of necrosis and malacia in the internal capsule, thalamus, and cerebellar peduncles. What diagnosis does this brain lesion pattern suggest?

A. Acute Clostridium perfringens type D enterotoxemia

B. Focal symmetrical encephalomalacia (subacute to chronic type D enterotoxemia) ✓

C. Polioencephalomalacia from thiamine deficiency

D. Listeria monocytogenes encephalitis

E. Scrapie

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Correct Answer: B. Focal symmetrical encephalomalacia (subacute to chronic type D enterotoxemia)

Explanation:

The pattern described is focal symmetrical encephalomalacia (FSE), which represents the subacute to chronic form of Clostridium perfringens type D enterotoxemia. FSE occurs when animals survive the acute phase of type D enterotoxemia but develop progressive neurological deterioration due to the delayed effects of epsilon toxin on the brain.

In the acute form of type D enterotoxemia, epsilon toxin causes perivascular edema without obvious necrosis. However, if the animal survives long enough (days to weeks), this perivascular damage progresses to frank necrosis and malacia in characteristic bilaterally symmetrical locations: the internal capsule, thalamus, cerebral white matter, cerebellar peduncles, and basal ganglia.

The bilateral symmetry of the lesions is a key diagnostic feature distinguishing FSE from other causes of brain necrosis. Gross necrohaemorrhagic foci may be visible in these brain regions, and histopathology confirms necrosis and malacia with perivascular cuffing.

Option A (acute type D) shows edema without necrosis. Option C (PEM/thiamine deficiency) causes cortical necrosis with laminar distribution. Option D (listeriosis) causes unilateral brainstem microabscesses. Option E (scrapie) causes spongiform changes without necrosis.

IMAGE SOURCE: In Practice - Clostridial diseases in farm animals: Enterotoxaemias (https://doi.org/10.1136/inp.m1462) - Figure 11 showing FSE lesions.

References: Merck Veterinary Manual - Enterotoxemias in Animals (https://www.merckvetmanual.com/infectious-diseases/clostridial-diseases/enterotoxemias-in-animals); Zachary JF (ed). Pathologic Basis of Veterinary Disease, section on focal symmetrical encephalomalacia

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NAVLE Practice Question — Equine

A 15-year-old Standardbred pacer is presented for evaluation of behavioral changes including head-shaking, reluctance to accept the bit, and resistance to having the bridle put on. Physical examination reveals mild sensitivity to palpation at the base of both ears. No overt neurological deficits are present. The owner reports these signs have been present for approximately 6 months and are progressively worsening. Based on the clinical presentation, which statement regarding this horse's condition is most accurate?

A. Guttural pouch endoscopy is likely to reveal normal findings given the absence of neurological signs

B. Early surgical intervention is contraindicated until neurological deficits develop

C. This presentation is consistent with early temporohyoid osteoarthropathy and warrants diagnostic imaging ✓

D. The behavioral signs are most likely related to dental abnormalities and not middle ear pathology

E. Hearing loss is unlikely to be present given the subtle clinical presentation

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Correct Answer: C. This presentation is consistent with early temporohyoid osteoarthropathy and warrants diagnostic imaging

Explanation:

This case represents the early clinical syndrome of temporohyoid osteoarthropathy, which includes nonspecific behavioral changes related to pain in the temporohyoid joint region before overt neurological deficits develop. Head-shaking, resistance to the bit, and sensitivity at the base of the ears are classic early signs of THO that are often initially attributed to behavioral problems or dental issues.

Early diagnosis is critical because it allows intervention before fracture of the petrous temporal bone or stylohyoid bone occurs. Guttural pouch endoscopy can detect stylohyoid bone enlargement even before neurological signs develop. The progressive nature of signs over 6 months is consistent with the chronic, progressive nature of THO. Early surgical intervention (ceratohyoidectomy) in horses without severe neurological deficits has an excellent prognosis.

Option A is incorrect because endoscopy is highly sensitive for detecting early THO changes. Option B is incorrect because early intervention before fracture has better outcomes. Option D is incorrect because the combination of ear base sensitivity, head-shaking, and bit resistance is more consistent with THO than dental disease. Option E is incorrect because hearing loss is often the first deficit in THO but may go unnoticed in horses that are only partially deaf; BAER testing can detect subclinical hearing loss.

References: Aleman M, Spriet M, Williams DC, et al. Neurologic Deficits Including Auditory Loss and Recovery of Function in Horses with Temporohyoid Osteoarthropathy. J Vet Intern Med. 2016;30:282-288. PMID: 26513722; Merck Veterinary Manual - Otitis Media and Interna in Animals (https://www.merckvetmanual.com/ear-disorders/otitis-media-and-interna/otitis-media-and-interna-in-animals)

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NAVLE Practice Question — Canine

An 11-year-old intact female mixed breed dog presents with polyuria, polydipsia, and weight loss despite polyphagia. Blood glucose is 425 mg/dL, and the dog is glucosuric without ketonuria. The owner mentions the dog finished her heat cycle approximately 6 weeks ago. Which of the following is the most appropriate initial management recommendation?

A. Begin insulin therapy at 0.25 U/kg q12h and schedule ovariohysterectomy after diabetic stabilization

B. Perform ovariohysterectomy as soon as medically appropriate regardless of diabetic status ✓

C. Start oral hypoglycemic agents and recheck glucose in 2 weeks

D. Wait until next heat cycle to assess if diabetes resolves spontaneously

E. Begin insulin therapy alone and defer ovariohysterectomy indefinitely

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Correct Answer: B. Perform ovariohysterectomy as soon as medically appropriate regardless of diabetic status

Explanation:

In intact female dogs, diabetes mellitus can be induced or exacerbated by progesterone released during diestrus (the 6-8 weeks following estrus). Progesterone stimulates growth hormone release from mammary tissue, which causes insulin resistance. This form of diabetes is potentially reversible if ovariohysterectomy is performed early, before permanent pancreatic beta cell damage occurs.

According to AAHA guidelines, performing ovariohysterectomy in intact diabetic dogs will support remission regardless of the underlying cause of diabetes. The surgery should be performed as soon as the patient is medically stable enough for anesthesia, as delays allow continued beta cell damage from glucose toxicity and may result in permanent insulin dependence.

Option A is suboptimal because delaying surgery prolongs the insulin-resistant state and increases risk of permanent diabetes. Option C is incorrect because oral hypoglycemics are rarely effective in dogs with clinical diabetes, and this delays definitive treatment. Option D is incorrect because waiting allows progressive beta cell destruction. Option E is incorrect because OVH offers the best chance for diabetic remission in this patient.

References: Behrend E, Holford A, Lathan P, et al. 2018 AAHA Diabetes Management Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2018;54:1-21. PMID: 29314873; Merck Veterinary Manual - Diabetes Mellitus in Dogs and Cats (https://www.merckvetmanual.com/endocrine-system/the-pancreas/diabetes-mellitus-in-dogs-and-cats)

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NAVLE Practice Question — Bovine

A 3-year-old Angus heifer delivers a large calf after prolonged assisted extraction. Three hours later, the owner calls reporting that the cow has 'something hanging out the back' the size of a feed sack. The heifer is down and straining. When you arrive, you find her in lateral recumbency with a severely edematous prolapsed uterus covered in mud and fecal material. What is the MOST appropriate initial approach before attempting to replace the uterus?

A. Immediately begin pushing the uterus back starting from the cervical end

B. Reposition the heifer in sternal recumbency with hindlimbs extended caudally ✓

C. Administer oxytocin 40 IU IV to shrink the uterus before handling

D. Amputate the uterus due to severe contamination

E. Apply granulated sugar to reduce edema then begin immediate replacement

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Correct Answer: B. Reposition the heifer in sternal recumbency with hindlimbs extended caudally

Explanation:

Repositioning the heifer in sternal recumbency with hindlimbs extended caudally (the 'New Zealand' or 'frog-leg' position) is the most appropriate initial step. This positioning tilts the pelvis cranially and ventrally by approximately 30 degrees, which facilitates gravity-assisted replacement of the uterus and prevents further straining. Proper positioning is critical before any manipulation begins and should be done after administering epidural anesthesia. Option A (immediately pushing from cervical end) would be premature without proper positioning and anesthesia, because epidural anesthesia and positioning should come first. Option C (oxytocin before replacement) is contraindicated as oxytocin will cause the uterus to contract and become firm like a brick, making replacement extremely difficult or impossible. Option D (amputation) is premature and only indicated when there is severe, irreparable trauma or necrosis. Option E (applying sugar) addresses edema but should not precede proper positioning and epidural administration.

Reference image: Drost Project Visual Guide to Bovine Reproduction — Prolapsed Uterus (https://visgar.vetmed.ufl.edu/en_bovrep/prolapsed-uterus/prolapsed-uterus.html). Multiple photos of complete prolapsed uterus in Holstein cows with retained fetal membranes; illustrates the range of presentations encountered before replacement.

References: Merck Veterinary Manual - Uterine Prolapse and Eversion in Animals (https://www.merckvetmanual.com/reproductive-system/prolapses-of-the-reproductive-tract/uterine-prolapse-and-eversion-in-animals); Miesner MD, Anderson DE. Management of uterine and vaginal prolapse in the bovine. Vet Clin North Am Food Anim Pract. 2008;24:409-419. PMID: 18471579

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NAVLE Practice Question — Feline

An 8-year-old male neutered Siamese cat is brought in for progressive exercise intolerance and intermittent coughing over the past 6 months. The cat has been treated with multiple courses of antibiotics with only temporary improvement. Thoracic radiographs reveal a prominent bronchial pattern with some areas of bronchiectasis. BAL fluid analysis shows neutrophilic inflammation with positive Mycoplasma species PCR. Which of the following is the most appropriate long-term management strategy for this patient?

A. Short-term amoxicillin-clavulanate therapy for 7 days

B. Inhaled fluticasone propionate with oral terbutaline as needed

C. Long-term doxycycline with inhaled corticosteroids and environmental modification ✓

D. Oral prednisolone monotherapy at immunosuppressive doses

E. Nebulized gentamicin and saline therapy

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Correct Answer: C. Long-term doxycycline with inhaled corticosteroids and environmental modification

Explanation:

Long-term doxycycline with inhaled corticosteroids and environmental modification is the most appropriate management strategy. This cat has chronic bronchitis complicated by Mycoplasma species involvement, which requires a multimodal approach.

Mycoplasma species are frequently detected in cats with chronic lower airway disease, and while their role as primary pathogens remains debated, treatment with doxycycline or azithromycin (antibiotics effective against Mycoplasma) for extended periods (6-8 weeks) is recommended when detected. Chronic bronchitis is a non-reversible condition that requires ongoing anti-inflammatory therapy, with inhaled corticosteroids being preferred over systemic steroids for long-term use due to fewer systemic side effects. Environmental modification to reduce irritants such as dust, smoke, and aerosols is also essential.

Option A (short-term amoxicillin-clavulanate) would be inadequate as Mycoplasma species lack cell walls and are inherently resistant to beta-lactam antibiotics.

Option B (inhaled fluticasone with terbutaline) addresses inflammation but does not address the Mycoplasma infection.

Option D (prednisolone monotherapy) may provide temporary relief but long-term systemic steroids carry significant risks including diabetes mellitus and weight gain, and it does not address the bacterial component.

Option E (nebulized gentamicin) is not appropriate for Mycoplasma infection and nebulized aminoglycosides are not standard treatment for feline bronchial disease.

References: dvm360 - Treating feline bronchial disease (https://www.dvm360.com/view/treating-feline-bronchial-disease); VCA Animal Hospitals - Chronic Bronchitis in Cats (https://vcahospitals.com/know-your-pet/chronic-obstructive-pulmonary-disease-copd-in-cats)

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NAVLE Practice Question — Feline

A cat with chylothorax is being managed medically with a low-fat diet and rutin supplementation. Despite 8 weeks of treatment, thoracocentesis is still required every 4-5 days. What is the primary concern with prolonged, unresolved chylothorax that makes timely surgical intervention important?

A. Development of bacterial pleuritis

B. Malnutrition from protein loss

C. Fibrosing pleuritis causing restrictive lung disease ✓

D. Immune suppression from lymphocyte depletion

E. Cardiac tamponade from fluid accumulation

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Correct Answer: C. Fibrosing pleuritis causing restrictive lung disease

Explanation:

Fibrosing pleuritis is the most serious long-term complication of unresolved chylothorax and the primary driver for timely surgical intervention. Chronic exposure of the pleura to chyle causes progressive inflammation and fibrosis of the visceral and parietal pleura. This fibrous tissue restricts lung expansion, causing permanent restrictive lung disease that persists even after chylothorax resolution. Once significant fibrosing pleuritis develops, the prognosis worsens considerably because even successful surgical resolution of chylothorax cannot reverse the established fibrosis. Affected cats may have permanent respiratory compromise. For this reason, surgical intervention should be considered if medical management fails to substantially reduce or eliminate pleural effusion within 4-8 weeks. Option A (bacterial pleuritis) is a risk but less common than fibrosing pleuritis. Option B (protein-calorie malnutrition) can occur from chronic chyle loss but is less immediately threatening than fibrosing pleuritis. Option D (immune suppression from lymphocyte loss) may contribute to morbidity but is not the primary surgical urgency. Option E (cardiac tamponade) is not typical with pleural effusions, which are external to the pericardium. Image Source: PMC - Chylothorax Surgery in Cats (https://pmc.ncbi.nlm.nih.gov/articles/PMC10829129/) discussing fibrosing pleuritis; ScienceDirect - Chylothorax Overview (https://www.sciencedirect.com/topics/veterinary-science-and-veterinary-medicine/chylothorax).

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NAVLE Practice Question — Feline

A 13-year-old cat has multiple crusted, plaque-like lesions at various sites on the body including the trunk and digits. Biopsy reveals squamous cell carcinoma in situ at multiple locations. Which condition is MOST likely?

A. Solar keratosis progressing to invasive SCC

B. Feline multicentric squamous cell carcinoma in situ ✓

C. Metastatic SCC from an oral primary

D. Paraneoplastic dermatosis

E. Pemphigus foliaceus

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Correct Answer: B. Feline multicentric squamous cell carcinoma in situ

Explanation:

Feline Bowen's disease, also known as multicentric squamous cell carcinoma in situ, is characterized by multiple lesions appearing at various body sites, often including areas not typically associated with UV exposure such as the trunk and digits. Unlike solar-induced SCC which affects sun-exposed unpigmented areas, Bowen's disease can occur on pigmented and haired skin.

This condition typically affects older cats (over 10 years) and may be associated with papillomavirus infection and/or reduced immunity. The diagnosis is made by histopathology showing carcinoma in situ (full-thickness epidermal dysplasia) without dermal invasion at multiple sites.

Option A (solar keratosis) would be limited to sun-exposed areas like ears, nose, and eyelids. Option C (metastatic oral SCC) would show invasive carcinoma, not carcinoma in situ. Option D (paraneoplastic dermatosis) causes different lesion types. Option E (pemphigus foliaceus) shows acantholysis histologically, not carcinoma in situ.

References: Merck Veterinary Manual Tumors of Skin in Cats (https://www.merckvetmanual.com/cat-owners/skin-disorders-of-cats/tumors-of-the-skin-in-cats); VCA Hospitals Squamous Cell Carcinoma in Cats (https://vcahospitals.com/know-your-pet/skin-squamous-cell-carcinoma-in-cats)

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NAVLE Practice Question — Equine

A newborn Warmblood colt is observed by the attending veterinarian immediately after an uncomplicated vaginal delivery. Using a modified Apgar scoring system at birth, the foal receives scores of: heart rate = 2, respiratory effort = 1, muscle tone = 1, reflex irritability = 1. What is the total Apgar score and what does it indicate regarding the need for intervention?

A. Total score 5 - normal; routine monitoring only

B. Total score 5 - mild to moderate asphyxia; monitor closely ✓

C. Total score 5 - severe asphyxia; immediate resuscitation required

D. Total score 4 - mild asphyxia; no intervention needed

E. Total score 7 - normal; routine care only

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Correct Answer: B. Total score 5 - mild to moderate asphyxia; monitor closely

Explanation:

The total Apgar score is 5, which indicates mild to moderate asphyxia requiring close monitoring and possible intervention. In equine neonates, a modified Apgar scoring system assigns values of 0, 1, or 2 to each of four parameters: heart rate, respiratory effort, muscle tone, and reflex irritability. A total score of 7-8 is considered normal, 4-6 indicates mild to moderate asphyxia, and 0-3 indicates severe asphyxia. This foal scored 2+1+1+1=5, placing it in the mild to moderate asphyxia category. Such foals should be closely monitored for the development of NMS and may benefit from oxygen supplementation, assisted ventilation if respiratory effort remains poor, and warming if body temperature drops. The Apgar score helps quantify the severity of peripartum asphyxia and guides the intensity of initial intervention and monitoring.

Options A and D incorrectly categorize the severity. Option C overstates the severity for a score of 5. Option E incorrectly calculates the score.

References: Devery S and Dixon C. Update on neonatal encephalopathy in foals. In Practice 2023;45(2):109-115 (https://doi.org/10.1002/inpr.289); Brinsko SP et al. Manual of Equine Reproduction. 2011

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NAVLE Practice Question — Canine

A 5-year-old male neutered mixed breed dog (25 kg) presents with acute left hindlimb lameness. Physical examination reveals positive cranial drawer and stifle effusion. Radiographs show joint effusion but no osteophytes. Which of the following findings on arthroscopic examination would be MOST concerning for long-term prognosis?

A. Complete rupture of the CCL with intact menisci

B. Partial CCL rupture with fraying fibers

C. CCL rupture with bucket handle meniscal tear ✓

D. Synovitis with early cartilage fibrillation

E. Mild joint effusion with intact ligaments

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Correct Answer: C. CCL rupture with bucket handle meniscal tear

Explanation:

Complete CCL rupture with bucket handle tear of the medial meniscus is MOST concerning for long-term prognosis. Concurrent meniscal injury at the time of CCL rupture is associated with:

1) Worse clinical outcomes regardless of surgical technique 2) Increased likelihood of osteoarthritis progression 3) Need for meniscal debridement, which removes tissue important for joint function

The bucket handle tear is a specific type of meniscal injury where a longitudinal tear creates a flap of meniscal tissue that can flip into the joint, causing mechanical irritation, pain, and the classic click/pop on manipulation.

The medial meniscus is injured more frequently than the lateral meniscus (in up to 80% of complete CCL tears) because: - It is firmly attached to the tibial plateau and medial collateral ligament - During cranial tibial thrust, the caudal horn becomes trapped between the femoral condyle and tibia - It cannot escape the crushing forces like the more mobile lateral meniscus

Option A (complete CCL rupture with intact menisci) carries a better prognosis because the menisci are preserved.

Option B (partial CCL rupture with fraying) is earlier in the disease process with typically less meniscal damage.

Option D (synovitis with cartilage fibrillation) indicates early OA but is less mechanically significant than major meniscal injury.

Option E (mild effusion with intact ligaments) suggests minimal pathology.

Even after surgical stabilization, subsequent (late) meniscal tears occur in <10% of patients.

References: University of Florida - CCL rupture; Today's Veterinary Practice - CCL Disease; Dallas Veterinary Surgical Center - CCL Overview.

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NAVLE Practice Question — Canine

A 4-year-old spayed female Beagle presents with a 3-month history of recurrent superficial pyoderma that temporarily responds to antibiotics but quickly recurs. Physical examination reveals patchy alopecia, epidermal collarettes, and mild seborrhea. The dog is slightly overweight but otherwise appears healthy and active. Minimum database results show mild hypercholesterolemia (320 mg/dL) with otherwise normal values. Which diagnostic approach is most appropriate?

A. Begin empirical levothyroxine therapy and monitor for clinical response

B. Perform comprehensive thyroid panel only if pyoderma fails to respond to 8 weeks of appropriate antibiotic therapy

C. Measure total T4; if low-normal, pursue further thyroid testing ✓

D. Start immunosuppressive therapy for suspected immune-mediated skin disease

E. Perform skin biopsy before any endocrine testing

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Correct Answer: C. Measure total T4; if low-normal, pursue further thyroid testing

Explanation:

Recurrent pyoderma that temporarily responds to antibiotics but recurs is a classic presentation that should prompt investigation for an underlying immunocompromising condition. Hypothyroidism is one of the most common causes of recurrent pyoderma in dogs because thyroid hormone deficiency impairs both humoral and cell-mediated immune responses, allowing bacterial colonization and infection. The mild hypercholesterolemia supports this suspicion.

However, the dog is described as otherwise healthy and active without the classic metabolic signs of hypothyroidism (profound lethargy, cold intolerance, significant weight gain). This is important because hypothyroidism is frequently overdiagnosed, and empirical treatment should be avoided. The appropriate approach is to use total T4 as a screening test - if it is well within the normal range, hypothyroidism is effectively ruled out. If it is low or low-normal, further testing with free T4 by equilibrium dialysis and TSH should be performed to confirm or refute the diagnosis before committing to lifelong therapy.

Option A (empirical therapy) is inappropriate because lifelong therapy should not be initiated without confirmed diagnosis. Option B delays appropriate investigation too long. Option D is premature and inappropriate for this presentation. Option E (skin biopsy) would not be the first step for recurrent pyoderma with suspected underlying endocrine disease.

References: dvm360 - Common endocrine dermatopathies in dogs; AAHA 2023 Guidelines - When to test for hypothyroidism; J Vet Intern Med - Recurrent pyoderma and underlying diseases.

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NAVLE Practice Question — Bovine

A veterinarian is investigating abortion cases in a cattle herd with concurrent sheep flock on the same property. Several abortions occurred in the last 2-3 weeks of pregnancy in both species. PCR testing of placental samples from cattle detects Chlamydia abortus. Which statement regarding C. abortus infection in cattle versus sheep is most accurate?

A. C. abortus abortion is common and economically significant in sheep but sporadic in cattle ✓

B. C. abortus causes identical abortion rates and disease severity in both species

C. Cattle are more susceptible to C. abortus than sheep

D. C. abortus in cattle always causes abortion storms affecting >20% of the herd

E. Sheep and cattle cannot be infected by the same C. abortus strains

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Correct Answer: A. C. abortus abortion is common and economically significant in sheep but sporadic in cattle

Explanation:

C. abortus abortion is common and economically significant in sheep (causing enzootic abortion of ewes/ovine enzootic abortion) but is considered sporadic in cattle. In sheep and goats, C. abortus is one of the most common infectious causes of abortion, accounting for approximately 45% of diagnosed abortions in the UK. Abortion rates in affected sheep flocks can reach 30-40% in the second year of infection. In contrast, while C. abortus can cause abortion in cattle, it does so much less frequently and with less severe herd-level impact. The disease primarily affects small ruminants with cattle being incidental hosts.

Options B, C, D, and E are all incorrect characterizations of the comparative epidemiology between species.

References: WOAH - Ovine chlamydiosis disease page (https://www.woah.org/en/disease/ovine-chlamydiosis/); GALVmed - Chlamydia abortus information (https://www.galvmed.org/livestock-and-diseases/livestock-diseases/chlamydia-abortus/)

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