National Practising Veterinarian Qualification Examination (全国执业兽医资格考试) · China · Examination committee under the Ministry of Agriculture and Rural Affairs (MARA)
Original practice questions written to the published syllabus · not past papersThe diseases of commercial and backyard poultry: viral, bacterial, parasitic, nutritional and toxic.
In the exams: ICAR AICE-JRF Medicine and Pathology units; China comprehensive paper poultry 20; SAVC poultry 15
How our questions for National Practising Veterinarian Qualification Examination spread across the units of Avian Pathology. Difficulty: 16 easy, 25 medium, 12 hard.
| Infectious bursal disease | 5 | |
| Mycotoxicosis | 5 | |
| Newcastle disease | 4 | |
| Avian influenza | 4 | |
| Infectious bronchitis | 4 | |
| Infectious laryngotracheitis | 4 | |
| Marek's disease | 4 | |
| Hydropericardium syndrome | 4 | |
| Mycoplasmosis | 4 | |
| Pullorum disease and fowl typhoid | 4 | |
| Coccidiosis | 4 | |
| Necrotic enteritis | 4 | |
| Avian leucosis | 3 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Which host species is primarily affected by infectious laryngotracheitis?
C. Chickens
ILT is mainly a disease of chickens; pheasants and peafowl can also be infected. Waterfowl and pigeons are not significant hosts.
Further reading: Swayne (ed.), Diseases of Poultry, 14th ed.; Pattison et al., Poultry Diseases, 6th ed.
Broilers aged 4 weeks show sudden depression, vent pecking and whitish watery diarrhoea. Deaths rise sharply, peak on day 3 and return to normal by day 7. Post-mortem shows an enlarged, oedematous bursa with yellow gelatinous transudate and haemorrhages in the thigh and breast muscles. What is the diagnosis?
D. Infectious bursal disease
Age, spiking mortality curve, oedematous bursa and muscle haemorrhages are classic IBD. ND lacks the bursal oedema; E. tenella causes bloody caecal lesions; chicken infectious anaemia occurs at 2-4 weeks with pale marrow and thymic and bursal atrophy but not an oedematous bursa.
Further reading: Swayne (ed.), Diseases of Poultry, 14th ed.; Pattison et al., Poultry Diseases, 6th ed.
A 14-week-old pullet lies with one leg stretched forward and the other backward. At post-mortem the left sciatic nerve is grey, swollen to about three times the size of the right and has lost its cross-striations. What is the most likely diagnosis?
D. Marek's disease
The 'splits' posture with unilateral nerve enlargement and loss of cross-striations is classical Marek's disease. Lymphoid leukosis does not involve peripheral nerves; riboflavin deficiency causes curled toes in young chicks and usually bilateral nerve swelling; ND causes nervous signs without nerve enlargement.
Further reading: Swayne (ed.), Diseases of Poultry, 14th ed.; Pattison et al., Poultry Diseases, 6th ed.
Chicks aged 3 weeks from a young breeder flock are pale with a haematocrit of 18%, thymic atrophy, pale yellow bone marrow and gangrenous dermatitis. Which virus, often a forerunner of adenoviral disease, is most likely involved?
B. Chicken anaemia virus
Aplastic anaemia (haematocrit well below about 27%), thymic atrophy and pale marrow at 2-4 weeks are chicken infectious anaemia, caused by a gyrovirus transmitted vertically from breeders infected in lay. It predisposes to inclusion body hepatitis and HPS; FAdV-4 itself does not cause aplastic anaemia.
Further reading: Swayne (ed.), Diseases of Poultry, 14th ed.; Pattison et al., Poultry Diseases, 6th ed.
A breeder flock recently vaccinated with an inactivated oil-emulsion vaccine shows 30% positive reactions on the serum plate agglutination test for Mycoplasma gallisepticum, but no clinical signs. What should be done next?
B. Confirm reactors by HI or ELISA and PCR before any decision on the flock
The rapid plate test is sensitive but gives false positives, notably after oil-emulsion vaccines, so positives are confirmed by HI or ELISA and by PCR for the organism. Slaughtering on a screening test is premature, treating first confuses later testing, and vaccinated flocks can still be infected.
Further reading: WOAH Terrestrial Manual, avian mycoplasmosis and fowl typhoid/pullorum chapters; Swayne (ed.), Diseases of Poultry, 14th ed.
Which is the most reliable way for a broiler integrator to prevent Mycoplasma gallisepticum in its flocks?
A. Source chicks from breeder flocks monitored and certified MG-free, and keep single-age biosecure farms
MG is transmitted vertically, so freedom starts with MG-free breeders, then biosecurity prevents horizontal entry. Continuous antibiotics do not eliminate infection and drive resistance; broilers are not normally vaccinated against MG; the ND vaccination route does not prevent MG.
Further reading: Swayne (ed.), Diseases of Poultry, 14th ed.; Pattison et al., Poultry Diseases, 6th ed.
Which Eimeria species of the chicken causes haemorrhagic lesions confined to the caeca?
D. Eimeria tenella
E. tenella develops in the caeca, causing bloody caecal contents and later caecal cores. E. acervulina affects the duodenum, E. maxima the mid-intestine and E. brunetti the lower intestine and rectum.
Further reading: Swayne (ed.), Diseases of Poultry, 14th ed.; Taylor, Coop and Wall, Veterinary Parasitology, 4th ed.
Necrotic enteritis of broilers is caused by:
A. Clostridium perfringens
Necrotic enteritis is caused by NetB-producing C. perfringens. C. colinum causes ulcerative enteritis (quail disease), C. botulinum causes botulism (limberneck) and C. septicum is associated with gangrenous dermatitis.
Further reading: Swayne (ed.), Diseases of Poultry, 14th ed.; Rood et al. (2018) Anaerobe 53: 5-10
A broiler company changes from maize-based to wheat- and barley-based diets and at the same time removes in-feed antibiotic growth promoters. Which disease is most likely to increase?
B. Necrotic enteritis
Non-starch polysaccharides in wheat and barley increase gut viscosity and nutrient supply for C. perfringens, and removing growth promoters removes suppression of clostridia, both predisposing to necrotic enteritis. The viral diseases listed are not affected by these dietary changes.
Further reading: Swayne (ed.), Diseases of Poultry, 14th ed.; Rood et al. (2018) Anaerobe 53: 5-10
Broilers have yellow crusty necrotic lesions at the commissures of the beak, on the tongue and in the crop, with poor feathering. Which mycotoxin is most likely?
D. T-2 toxin
T-2 toxin and related trichothecenes are caustic and cause oral necrosis. Aflatoxin is hepatotoxic, ochratoxin nephrotoxic, and poultry are relatively tolerant of fumonisins.
Further reading: Swayne (ed.), Diseases of Poultry, 14th ed., mycotoxicoses chapter; Pattison et al., Poultry Diseases, 6th ed.
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