I85PREP
⌘ K
TSPSC Veterinary Surgeon study materials
TSPSC Veterinary Surgeon study resources

TSPSC Veterinary Surgeon practice questions

One question at a time. Build your TSPSC Veterinary Surgeon understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1Veterinary Anatomy and Histology

In the ruminant stomach, the compartment lined by a honeycomb-like reticulum of mucosal folds and bearing no papillae is the:

  1. Reticulum Correct answer.
  2. Rumen
  3. Omasum
  4. Abomasum

Explanation

The reticulum is named for the net-like crests that divide its mucosa into honeycomb cells, and its surface is free of the papillae seen in the rumen. The omasum instead carries longitudinal laminae, while the abomasum is the glandular true stomach. This internal relief allows the compartment to be identified even in a preserved specimen.

Question 2Veterinary Anatomy and Histology

The bones of the carpus in the horse are arranged in two rows; the proximal row contains which set of bones?

  1. Accessory, second and fourth carpals
  2. Radial, intermediate, ulnar and accessory carpals Correct answer.
  3. Radial, second and third carpals
  4. Second, third and fourth carpals

Explanation

In the horse the proximal carpal row consists of the radial, intermediate, ulnar and accessory (accessory carpal) bones, giving four elements. The distal row holds the second, third and fourth carpals, with the first carpal usually absent. Counting rows and elements is a standard way to identify equine carpal bones.

Question 3Veterinary Anatomy and Histology

Which epithelial type lines the alveoli of the mammary gland, and what is its functional significance?

  1. Simple cuboidal to columnar secretory epithelium, permitting synthesis and release of milk constituents Correct answer.
  2. Pseudostratified ciliated columnar epithelium, moving secretions by ciliary action
  3. Simple squamous epithelium, allowing passive diffusion only
  4. Stratified squamous keratinised epithelium, providing abrasion resistance

Explanation

The secretory alveoli are lined by a single layer of cuboidal to columnar cells whose height varies with the stage of lactation, reflecting active synthesis of milk proteins and fat. Stratified squamous and ciliated pseudostratified epithelia serve protective and transport roles elsewhere and are not found in secretory alveoli. Simple squamous lining would not support the synthetic workload of lactation.

Question 4Veterinary Anatomy and Histology

The dorsal root ganglion of a spinal nerve contains which type of neurons?

  1. Multipolar motor neurons
  2. Anaxonic amacrine neurons
  3. Bipolar photoreceptor neurons
  4. Pseudounipolar sensory neurons Correct answer.

Explanation

Cells of the dorsal root ganglion are pseudounipolar sensory neurons whose single process divides into a peripheral and a central branch. Multipolar motor neurons occupy the ventral horn and autonomic ganglia contain multipolar postganglionic cells. Bipolar and anaxonic neurons occur in special sensory pathways and retina respectively.

Question 5Veterinary Anatomy and Histology

In the domestic fowl, the long bones such as the humerus and femur are pneumatised because they contain:

  1. Cartilage canals lined by synovium
  2. Red marrow only, with no air spaces
  3. A gelatinous core of Wharton's jelly
  4. Air-filled diverticula of the respiratory system continuous with the bone interior Correct answer.

Explanation

Many avian long bones are hollowed and invaded by air sac diverticula, so the medullary cavity communicates with the respiratory system. This reduces skeletal mass and contributes to the bird's respiratory efficiency. Marrow, jelly or synovial canals do not explain pneumatisation.

Question 6Veterinary Anatomy and Histology

A section of hoof shows a thick, hard, keratinised layer with prominent tubular structures; this layer is best identified as:

  1. The stratum medium of the hoof wall Correct answer.
  2. The lamellar corium
  3. The digital cushion
  4. The perioplic corium

Explanation

The stratum medium forms the bulk of the hoof wall and is built of keratinised tubules and intertubular horn, giving it the characteristic tough, ridged appearance. The perioplic corium and lamellar corium are soft connective-tissue layers deep to the horn, and the digital cushion is a fibro-fatty pad.

Question 7Veterinary Anatomy and Histology

The characteristic enamel of a horse's incisor, which forms a central mark in the occlusal surface, is deposited in the:

  1. Periodontal ligament
  2. Infundibulum of the tooth Correct answer.
  3. Pulp chamber
  4. Root canal

Explanation

The infundibulum is the funnel-shaped invagination on the occlusal surface of the incisor, and it is filled with cement and enamel, producing the 'dental star' or central mark used in ageing horses. The root canal and pulp chamber lie internal to the dentine, and the periodontal ligament attaches the tooth to the alveolus.

Question 8Veterinary Anatomy and Histology

The avian syrinx is located at which site?

  1. At the bifurcation of the trachea into the primary bronchi Correct answer.
  2. Within the nasal cavity
  3. At the laryngeal inlet
  4. At the origin of the air sacs

Explanation

The syrinx is the voice-producing organ of birds and lies at the tracheobronchial junction, where the trachea divides into the two primary bronchi. The larynx is cranial and does not produce the song, and air sacs arise from bronchi downstream. Nasal structures are not the site of sound production.

Question 9Veterinary Anatomy and Histology

The artery that passes through the foramen of the transverse process of the sixth cervical vertebra in the horse is the:

  1. Facial artery
  2. Lingual artery
  3. Carotid artery
  4. Vertebral artery Correct answer.

Explanation

In the horse the vertebral artery traverses the transverse foramina of the cervical vertebrae, including that of the sixth, as it ascends towards the atlantic fossa. The carotid, facial and lingual arteries arise from the carotid system and do not occupy these foramina.

Question 10Veterinary Anatomy and Histology

The muscle that forms the bulk of the lateral wall of the equine abdominal cavity and is marked by a prominent aponeurosis is the:

  1. Transversus abdominis
  2. Internal abdominal oblique Correct answer.
  3. Rectus abdominis
  4. Diaphragm

Explanation

The internal abdominal oblique arises from the coxal tuber and inserts via a broad aponeurosis, forming the greater part of the lateral abdominal wall in the horse. Rectus abdominis lies ventrally, transversus abdominis is deepest, and the diaphragm separates thorax from abdomen.

Question 11Veterinary Anatomy and Histology

In a histological section of a dog's kidney, which structure is lined by a simple cuboidal epithelium with a brush border and is the site of most reabsorption?

  1. Distal convoluted tubule
  2. Thin limb of the loop of Henle
  3. Collecting duct
  4. Proximal convoluted tubule Correct answer.

Explanation

Proximal convoluted tubule cells are tall cuboidal with a pronounced brush border and abundant mitochondria, reflecting their dominant role in reabsorption. Distal tubule cells lack a brush border, the thin limb is squamous, and collecting duct cells are principally cuboidal with distinct cell borders.

Question 12Veterinary Anatomy and Histology

The annular ligament of the equine fetlock joint inserts principally on the:

  1. Third metacarpal bone
  2. Second phalanx
  3. Proximal phalanx Correct answer.
  4. Distal sesamoid (navicular) bone

Explanation

The annular ligament forms a ring around the flexor tendons at the fetlock and attaches mainly to the proximal phalanx, holding the tendons against the joint. The third metacarpal lies proximal to the joint, the navicular bone is distal within the hoof, and the second phalanx is further distal.

Question 13Veterinary Anatomy and Histology

The lymph node of a ruminant is described as 'haemal' when it contains:

  1. Abundant adipose tissue replacing the cortex
  2. Only lymphoid tissue with no sinuses
  3. Blood-filled sinuses in addition to lymphoid tissue Correct answer.
  4. A central cartilage plate

Explanation

So-called haemal nodes of ruminants (and some other species) contain blood-filled spaces within their lymphoid tissue, distinguishing them from ordinary lymph nodes. Ordinary nodes have lymphatic sinuses without blood filling, and neither cartilage plates nor fatty replacement define haemal nodes.

Question 14Veterinary Anatomy and Histology

The tapetum lucidum of the dog's eye is located in the:

  1. Choroid Correct answer.
  2. Retina
  3. Cornea
  4. Lens

Explanation

The tapetum lucidum is a reflective layer within the choroid that enhances night vision by reflecting light back through the retina. It is not retinal, corneal or lenticular tissue, though its reflection is seen through the pupil.

Question 15Veterinary Anatomy and Histology

During foetal development, the structure that shunts blood from the pulmonary trunk to the aorta in the mammal is the:

  1. Ductus venosus
  2. Ductus arteriosus Correct answer.
  3. Umbilical vein
  4. Foramen ovale

Explanation

The ductus arteriosus connects the pulmonary trunk to the descending aorta, bypassing the non-functional lungs, and becomes the ligamentum arteriosum after birth. The ductus venosus bypasses the liver, the foramen ovale shunts between atria, and the umbilical vein carries oxygenated blood from the placenta.

Question 16Veterinary Anatomy and Histology

A horse presents with a swollen, painful digital flexor tendon sheath region and the clinician suspects a 'windgall'. The structure involved lies between the:

  1. Annular ligament and the palmar/plantar aspect of the fetlock, containing the flexor tendons Correct answer.
  2. Superficial and deep digital flexor tendons within the hoof
  3. Extensor tendons over the dorsal carpus
  4. Suspensory ligament and the third metacarpal bone

Explanation

The digital flexor tendon sheath (tendon sheath of the fetlock) surrounds the flexor tendons as they pass palmar to the fetlock, deep to the annular ligament, and its distension produces a windgall. Intrathecal structures within the hoof relate to the navicular bursa, while the suspensory apparatus and dorsal extensor tendons occupy different planes.

Question 17Veterinary Physiology and Biochemistry

In ruminant physiology, which volatile fatty acid is absorbed in the greatest molar proportion from the rumen and serves as the principal precursor for de novo lipogenesis in adipose tissue?

  1. Acetic acid Correct answer.
  2. Lactic acid
  3. Butyric acid
  4. Propionic acid

Explanation

Acetate is the most abundant volatile fatty acid produced by rumen fermentation, typically contributing about 60–70% of total VFA, and it is the main carbon source for de novo fatty acid synthesis in ruminant adipose tissue. Propionate is largely gluconeogenic and butyrate is mostly metabolised to ketone bodies in the rumen epithelium.

Question 18Veterinary Physiology and Biochemistry

The sodium-potassium ATPase of the plasma membrane transports ions in which stoichiometric pattern per cycle of ATP hydrolysis?

  1. 3 Na+ in and 2 K+ out
  2. 2 Na+ out and 3 K+ in
  3. 3 Na+ out and 2 K+ in Correct answer.
  4. 1 Na+ out and 1 K+ in

Explanation

The Na+/K+-ATPase exports three sodium ions and imports two potassium ions for each ATP hydrolysed, generating an electrogenic net outward current that helps maintain the resting membrane potential. This 3:2 stoichiometry is fundamental to cell volume regulation and secondary active transport.

Question 19Veterinary Physiology and Biochemistry

Which hormone is synthesised and secreted by the corpus luteum and is essential for maintenance of pregnancy in the bitch?

  1. Prolactin
  2. Relaxin
  3. Oxytocin
  4. Progesterone Correct answer.

Explanation

The corpus luteum secretes progesterone, which prepares and maintains the endometrium for gestation; in the bitch the luteal phase is prolonged and luteal progesterone supports pregnancy. Oxytocin and relaxin have roles in parturition and pelvic relaxation rather than luteal maintenance.

Question 20Veterinary Physiology and Biochemistry

In the mammalian kidney, the segment of the nephron that is freely permeable to water but virtually impermeable to sodium is which of the following?

  1. Ascending thick limb of the loop of Henle
  2. Distal convoluted tubule
  3. Descending limb of the loop of Henle Correct answer.
  4. Proximal convoluted tubule

Explanation

The descending limb of the loop of Henle lacks significant ion transport but is highly water permeable, so tubular fluid becomes concentrated as it descends into the hypertonic medullary interstitium. The ascending limb is the water-impermeable, salt-transporting segment that builds the osmotic gradient.

Question 21Veterinary Physiology and Biochemistry

A cow with a cobalt-deficient diet develops anaemia and poor growth. Cobalt is required because it is a component of which vitamin?

  1. Vitamin K
  2. Vitamin B6
  3. Vitamin B12 Correct answer.
  4. Vitamin B1

Explanation

Cobalt is the central metal atom of cobalamin (vitamin B12), which rumen microbes synthesise; deficiency impairs propionate metabolism and causes anaemia and ill thrift in ruminants. The other listed vitamins do not contain cobalt.

Question 22Veterinary Physiology and Biochemistry

In the cardiac cycle, closure of the atrioventricular valves produces which heart sound, and at what point does it occur?

  1. Second heart sound, at the end of ventricular systole
  2. Third heart sound, during rapid ventricular filling
  3. Fourth heart sound, during atrial contraction
  4. First heart sound, at the start of ventricular systole Correct answer.

Explanation

The first heart sound (S1) is generated by closure of the mitral and tricuspid valves as ventricular pressure exceeds atrial pressure at the onset of systole. The second sound arises from semilunar valve closure at the end of systole.

Question 23Veterinary Physiology and Biochemistry

During strenuous exercise in a horse, oxygen delivery to muscle becomes limiting, so pyruvate is converted to lactate. The enzyme catalysing this reaction is which of the following?

  1. Lactate dehydrogenase Correct answer.
  2. Pyruvate carboxylase
  3. Phosphofructokinase-1
  4. Pyruvate kinase

Explanation

Lactate dehydrogenase reduces pyruvate to lactate while oxidising NADH to NAD+, allowing glycolysis to continue under anaerobic conditions by regenerating the NAD+ needed at the glyceraldehyde-3-phosphate dehydrogenase step. Pyruvate carboxylase and pyruvate kinase act at other points in pyruvate metabolism.

Question 24Veterinary Physiology and Biochemistry

In the fasting state, which hormone increases hepatic gluconeogenesis while simultaneously promoting lipolysis in adipose tissue?

  1. Calcitonin
  2. Glucagon Correct answer.
  3. Aldosterone
  4. Insulin

Explanation

Glucagon acts on hepatocytes to stimulate glycogenolysis and gluconeogenesis and on adipose tissue to promote lipolysis, mobilising energy substrates during fasting. Insulin has the opposite anabolic effect, while calcitonin and aldosterone regulate calcium and sodium balance respectively.

Question 25Veterinary Physiology and Biochemistry

The primary driving force for glomerular filtration in the mammalian nephron is which of the following?

  1. Glomerular capillary hydrostatic pressure exceeding the opposing oncotic and capsular pressures Correct answer.
  2. Oncotic pressure of plasma exceeding hydrostatic pressure in the glomerulus
  3. Active sodium secretion by mesangial cells into Bowman's space
  4. Contraction of the proximal tubular epithelium

Explanation

Filtration is driven by the net filtration pressure, which is glomerular capillary hydrostatic pressure minus the sum of plasma oncotic pressure and capsular hydrostatic pressure. Because the net value is positive along most of the capillary, fluid is filtered into Bowman's space.

Question 26Veterinary Physiology and Biochemistry

Which feature distinguishes the respiratory pigment of equine red cells from that of a lowland species adapted to hypoxia?

  1. A left-shifted oxygen dissociation curve indicating higher oxygen affinity Correct answer.
  2. A complete lack of the Bohr effect
  3. An absence of cooperative binding and a hyperbolic curve
  4. A right-shifted oxygen dissociation curve indicating lower oxygen affinity

Explanation

Species adapted to low oxygen tension, such as high-altitude camelids, show a left-shifted dissociation curve reflecting higher haemoglobin oxygen affinity, which improves loading at low partial pressures. A right shift would reduce loading and is not the adaptive pattern.

Question 27Veterinary Physiology and Biochemistry

In a sheep, insulin stimulates glucose uptake into muscle and adipose tissue by which mechanism?

  1. Inhibition of the sodium-potassium ATPase
  2. Translocation of GLUT4-containing vesicles to the plasma membrane Correct answer.
  3. Activation of adenylyl cyclase and cyclic AMP production
  4. Direct phosphorylation of the insulin receptor by glucose

Explanation

Insulin binding activates the receptor tyrosine kinase and downstream signalling that drives translocation of GLUT4 vesicles to the plasma membrane in muscle and adipose tissue. This increases facilitated glucose uptake without directly phosphorylating the receptor with glucose.

Question 28Veterinary Physiology and Biochemistry

Which of the following is the rate-limiting enzyme of cholesterol biosynthesis in the liver?

  1. HMG-CoA synthase
  2. Lipoprotein lipase
  3. HMG-CoA reductase Correct answer.
  4. Acetyl-CoA carboxylase

Explanation

HMG-CoA reductase converts HMG-CoA to mevalonate, the committed and rate-limiting step of cholesterol synthesis, and it is the target of statin drugs. HMG-CoA synthase is upstream and not rate-limiting, while acetyl-CoA carboxylase and lipoprotein lipase act in fatty acid metabolism.

Question 29Veterinary Physiology and Biochemistry

A newborn calf fails to pass meconium and shows abdominal distension. In the context of gastrointestinal physiology, which mechanism best explains the importance of colostrum for intestinal function?

  1. Colostrum provides immunoglobulins absorbed by pinocytosis and stimulates intestinal motility and maturation Correct answer.
  2. Colostrum supplies pancreatic enzymes needed for protein digestion
  3. Colostrum delivers bile salts required for fat emulsification
  4. Colostrum provides mature enterocytes that permanently replace fetal epithelium

Explanation

Colostrum supplies maternal immunoglobulins that the neonatal gut absorbs by pinocytosis during the brief period of macromolecular permeability, and it also stimulates gut motility and mucosal maturation. This is why timely colostrum intake supports both immunity and the passage of meconium.

Question 30Veterinary Physiology and Biochemistry

In the context of acid-base balance in a ruminant with severe diarrhoea, which change is expected in the blood?

  1. Increased bicarbonate with an increased partial pressure of carbon dioxide
  2. Decreased bicarbonate with a compensatory decrease in the partial pressure of carbon dioxide Correct answer.
  3. Decreased bicarbonate with an increased partial pressure of carbon dioxide
  4. Increased bicarbonate with a normal partial pressure of carbon dioxide

Explanation

Severe diarrhoea causes loss of bicarbonate-rich fluid, producing metabolic acidosis with a primary fall in plasma bicarbonate. Respiratory compensation increases ventilation and lowers the partial pressure of carbon dioxide.

Question 31Veterinary Physiology and Biochemistry

Which enzyme of the urea cycle is located in the mitochondrial matrix and catalyses the formation of citrulline from ornithine and carbamoyl phosphate?

  1. Arginase
  2. Carbamoyl phosphate synthetase I
  3. Ornithine transcarbamoylase Correct answer.
  4. Argininosuccinate synthetase

Explanation

Ornithine transcarbamoylase, located in the mitochondrial matrix, transfers the carbamoyl group from carbamoyl phosphate to ornithine to form citrulline. Argininosuccinate synthetase and arginase act later in the cycle in the cytosol.

Question 32Veterinary Physiology and Biochemistry

In the ovarian cycle of the mare, which event is associated with the preovulatory surge of luteinising hormone?

  1. Formation of the corpus luteum before ovulation
  2. Regression of follicles before the follicular wave
  3. Onset of luteolysis of the corpus luteum
  4. Resumption of meiosis in the oocyte and ovulation Correct answer.

Explanation

The preovulatory LH surge triggers resumption of meiosis in the primary oocyte and rupture of the mature follicle, releasing the oocyte. Corpus luteum formation follows ovulation, and luteolysis occurs later if pregnancy does not ensue.

Question 33Veterinary Microbiology and Immunology

In the context of veterinary immunology, which immunoglobulin is the principal antibody secreted onto mucosal surfaces of the respiratory and intestinal tracts in most domestic mammals?

  1. IgA Correct answer.
  2. IgE
  3. IgG
  4. IgM

Explanation

Secretory IgA is produced by plasma cells in the lamina propria and transported across epithelium via the polymeric immunoglobulin receptor, making it the dominant mucosal antibody. IgG predominates in serum and interstitial fluid, IgM is the primary response antibody in blood, and IgE mediates type I hypersensitivity.

Question 34Veterinary Microbiology and Immunology

A calf develops severe watery diarrhoea in the first week of life and a faecal sample shows acid-fast coccobacilli. Which organism is the most likely cause?

  1. Salmonella Dublin
  2. Escherichia coli K99
  3. Cryptosporidium parvum
  4. Mycobacterium avium subsp. paratuberculosis Correct answer.

Explanation

Mycobacterium avium subsp. paratuberculosis is an acid-fast coccobacillus that causes Johne's disease, though classic Johne's presents later; however, the acid-fast staining property is the defining discriminator among these options. Cryptosporidium is a protozoan detected by modified Ziehl-Neelsen but appears as spherical oocysts, not coccobacilli. E. coli and Salmonella are Gram-negative and not acid-fast.

Question 35Veterinary Microbiology and Immunology

Which type of hypersensitivity reaction underlies the intradermal tuberculin test used in cattle?

  1. Type IV delayed hypersensitivity Correct answer.
  2. Type III immune complex hypersensitivity
  3. Type II cytotoxic hypersensitivity
  4. Type I immediate hypersensitivity

Explanation

The tuberculin test relies on a cell-mediated response in which sensitised T lymphocytes release cytokines and recruit macrophages, producing a delayed palpable swelling 48 to 72 hours after injection. This is the hallmark of Type IV hypersensitivity. Types I, II and III are antibody-mediated and would not produce this delayed reading.

Question 36Veterinary Microbiology and Immunology

Which of the following best describes the mechanism by which the agar gel immunodiffusion test detects antibodies?

  1. Antibody-antigen complexes precipitate as visible lines where concentrations are optimal in the gel Correct answer.
  2. Antigen-coated red cells agglutinate in the presence of specific antibody
  3. Fluorescent-labelled antibody binds antigen fixed to a slide
  4. Antibody capture causes a colour change in an enzyme-linked substrate

Explanation

In agar gel immunodiffusion, antigen and antibody diffuse toward each other through a gel and form a visible precipitate line at the zone of equivalence. The other options describe fluorescent antibody tests, haemagglutination and ELISA respectively, none of which depend on precipitin line formation.

Question 37Veterinary Microbiology and Immunology

A dog is suspected of having canine parvovirus infection. Which laboratory finding most strongly supports an active infection rather than prior vaccination?

  1. Detection of viral DNA by PCR in faeces from an unvaccinated pup with haemorrhagic diarrhoea Correct answer.
  2. A fourfold rise in antibody titre between acute and convalescent sera
  3. Isolation of the virus from a throat swab in a recovered adult dog
  4. A high serum antibody titre by haemagglutination inhibition

Explanation

Detection of viral DNA in faeces of a clinically affected, unvaccinated pup confirms active shedding and disease. Antibody titres can reflect vaccination or past exposure, and virus isolation from a recovered dog is inconsistent with acute disease. PCR on faeces is the standard confirmatory test.

Question 38Veterinary Microbiology and Immunology

Which of the following is the principal function of the bursa of Fabricius in birds?

  1. Site of T lymphocyte maturation
  2. Organ of respiratory gas exchange
  3. Primary site of B lymphocyte maturation Correct answer.
  4. Storage site for calcium and phosphorus

Explanation

The bursa of Fabricius is a primary lymphoid organ in birds where B lymphocytes mature and acquire their repertoire before migrating to peripheral lymphoid tissues. T cells mature in the thymus, and the other options describe respiratory and skeletal functions unrelated to lymphoid development.

Question 39Veterinary Microbiology and Immunology

A sheep flock shows sudden deaths with necropsy findings of a swollen, dark spleen and serosal haemorrhages, and a Gram-positive rod is isolated. Which organism is most consistent with these findings?

  1. Bacillus anthracis Correct answer.
  2. Clostridium tetani
  3. Listeria monocytogenes
  4. Pasteurella multocida

Explanation

Bacillus anthracis is a large Gram-positive rod that causes peracute death with splenomegaly and haemorrhage in ruminants; the organism forms characteristic chains and spores. Clostridium tetani causes tetanus rather than septicaemia, Listeria causes encephalitis or abortion, and Pasteurella is a Gram-negative coccobacillus.

Question 40Veterinary Microbiology and Immunology

Which statement about the complement system in veterinary species is correct?

  1. Complement activation always results in cell lysis and never promotes inflammation
  2. The alternative pathway requires antibody bound to antigen for activation
  3. The classical pathway is activated by direct binding of C1q to microbial surfaces without antibody
  4. The membrane attack complex is formed by C5b, C6, C7, C8 and multiple C9 molecules Correct answer.

Explanation

The terminal complement pathway assembles C5b with C6, C7, C8 and multiple C9 units to form the membrane attack complex that perforates membranes. The classical pathway requires antibody, the alternative pathway is antibody-independent, and complement fragments such as C3a and C5a are potent anaphylatoxins.

Question 41Veterinary Microbiology and Immunology

A pig herd experiences an outbreak of disease characterised by abortion and stillbirth, and a Gram-negative coccobacillus is isolated from foetal tissues. Which organism is the most likely agent?

  1. Erysipelothrix rhusiopathiae
  2. Brucella suis Correct answer.
  3. Streptococcus suis
  4. Actinobacillus pleuropneumoniae

Explanation

Brucella suis is a Gram-negative coccobacillus that causes abortion and infertility in swine and is isolated from foetal tissues. Erysipelothrix and Streptococcus suis are Gram-positive, and Actinobacillus pleuropneumoniae causes pleuropneumonia rather than reproductive loss.

Question 42Veterinary Microbiology and Immunology

Which of the following statements about the major histocompatibility complex class I molecule is correct?

  1. It presents exogenous peptides to CD4+ T helper cells
  2. It is expressed only on the surface of B lymphocytes
  3. It presents endogenous peptides to CD8+ cytotoxic T cells Correct answer.
  4. It is encoded exclusively by genes on the X chromosome

Explanation

MHC class I molecules present peptides derived from intracellular proteins to CD8+ cytotoxic T lymphocytes, allowing recognition of virally infected or transformed cells. MHC class II presents exogenous peptides to CD4+ cells, and class I is expressed on nearly all nucleated cells.

Question 43Veterinary Microbiology and Immunology

A laboratory performs a Rose Bengal plate test on cattle sera and obtains agglutination. Which interpretation is most appropriate?

  1. It is a screening test for Brucella antibodies that requires confirmation by a more specific test Correct answer.
  2. It confirms active infection with Brucella abortus and requires immediate culling without further testing
  3. It measures Brucella antigen directly in serum and is diagnostic on its own
  4. It detects cell-mediated immunity to Brucella and replaces the tuberculin test

Explanation

The Rose Bengal plate test is a rapid screening agglutination test for Brucella antibodies and, because of possible cross-reactions, positive results must be confirmed by tests such as complement fixation or ELISA. It detects antibodies, not antigen, and does not assess cell-mediated immunity.

Question 44Veterinary Microbiology and Immunology

Which feature distinguishes a virus from a bacterium in terms of replication?

  1. Viruses contain both DNA and RNA genomes simultaneously
  2. Viruses possess ribosomes for independent protein synthesis
  3. Viruses require host cell machinery for replication and cannot replicate independently Correct answer.
  4. Viruses replicate by binary fission within host cells

Explanation

Viruses are obligate intracellular parasites that lack their own metabolic and translational machinery and must use host cell ribosomes and enzymes to replicate. They reproduce by assembly of components rather than binary fission, and no known virus carries both DNA and RNA as its genome.

Question 45Veterinary Microbiology and Immunology

In a serological survey, a test has high sensitivity but low specificity. What is the most likely consequence when applied to a low-prevalence population?

  1. Many true positives will be missed because of false negatives
  2. The prevalence estimate will be unaffected by specificity
  3. A high proportion of positive results will be false positives Correct answer.
  4. The test will have no predictive value at all

Explanation

Low specificity means many uninfected animals test positive, so in a low-prevalence population the positive predictive value falls and a large fraction of positives are false positives. Sensitivity affects the detection of true positives, while prevalence directly influences predictive values.

Question 46Veterinary Microbiology and Immunology

Which of the following best explains why inactivated vaccines generally require adjuvants and multiple doses?

  1. They contain live attenuated organisms that replicate and overwhelm the host
  2. They induce only cell-mediated immunity without antibody production
  3. They do not replicate and often stimulate a weaker immune response than live vaccines Correct answer.
  4. They consist only of polysaccharide antigens that cannot be processed

Explanation

Inactivated vaccines contain killed organisms or subunits that cannot replicate, so the antigen load is limited and the immune stimulus is weaker, necessitating adjuvants and booster doses. Live attenuated vaccines replicate and typically induce stronger, longer-lasting immunity with fewer doses.

Question 47Veterinary Microbiology and Immunology

A cat presents with fever and lymphadenopathy, and fine-needle aspirates of a lymph node reveal small bacteria that stain weakly with Gram stain and are positive with silver stain. Which organism is most likely?

  1. Pasteurella multocida
  2. Bartonella henselae Correct answer.
  3. Streptococcus canis
  4. Chlamydia felis

Explanation

Bartonella henselae is a fastidious Gram-negative organism that stains poorly with Gram stain but is visualised with silver stains such as Warthin-Starry, and it causes fever and lymphadenopathy in cats. The other organisms are either readily Gram-stained or have different tropism and staining characteristics.

Question 48Veterinary Microbiology and Immunology

Which statement correctly describes the role of cytokines in the immune response?

  1. Chemokines are large structural proteins that form the membrane attack complex
  2. Interleukin-4 drives differentiation of naive T cells toward a Th1 phenotype
  3. Interleukin-1 and tumour necrosis factor alpha are key mediators of the acute phase and fever response Correct answer.
  4. Interferon gamma is produced mainly by B lymphocytes to promote antibody class switching

Explanation

Interleukin-1 and TNF-alpha are pro-inflammatory cytokines released mainly by macrophages that induce fever, acute phase protein synthesis and endothelial activation. Interferon gamma is produced by T and NK cells, IL-4 promotes Th2 differentiation, and chemokines are small chemoattractant proteins unrelated to the membrane attack complex.

Question 49Veterinary Pathology

In a sheep necropsy, the lungs are heavy, rubbery and fail to collapse, with interlobular septa distended by clear fluid and prominent lymphatic beads. Which pathological process best explains these findings?

  1. Interstitial pulmonary emphysema with alveolar rupture into septa
  2. Chronic interstitial pneumonia with diffuse fibrosis
  3. Pulmonary alveolar microlithiasis with intra-alveolar mineral deposits
  4. Pulmonary oedema with interlobular lymphatics distended by transudate Correct answer.

Explanation

Heavy, rubbery, non-collapsing lungs with widened, fluid-filled interlobular septa and visible lymphatic beading are the classic gross picture of pulmonary oedema, in which transudate floods alveoli and perivascular/perilobular lymphatics. The clear septal fluid is oedema rather than fibrin or fibrosis.

Question 50Veterinary Pathology

Which morphological cell change is the earliest light-microscopic hallmark of reversible acute cell injury?

  1. Nuclear karyolysis with loss of basophilia
  2. Coagulative necrosis of the affected tissue
  3. Apoptotic body formation with chromatin condensation
  4. Cellular swelling with cytoplasmic blebs Correct answer.

Explanation

Acute reversible injury first impairs the sodium-potassium ATPase, causing water influx and hydropic (vacuolar) swelling with cytoplasmic blebbing. Nuclear dissolution and coagulative necrosis reflect irreversible injury, and apoptotic bodies indicate programmed cell death rather than simple reversible swelling.