AVMA ABVS-recognised specialty boards · USA · AVMA American Board of Veterinary Specialties; each college runs its own exams
Original practice questions written to the published syllabus · not past papersHow disease is measured, studied and controlled in populations, from incidence and prevalence to surveillance and outbreak investigation, plus the major zoonoses and One Health.
In the exams: Nepal NLEV Epidemiology & Public Health 6; SAVC epidemiology 15 and zoonoses 25; EGEL Plus epidemiology 15; ICAR AICE-JRF core group 06
How our questions for AVMA ABVS-recognised specialty boards spread across the units of Veterinary Epidemiology & Zoonoses. Difficulty: 0 easy, 10 medium, 18 hard.
| Epidemiological study designs | 5 | |
| Evaluation of diagnostic tests: sensitivity and specificity | 5 | |
| Surveillance | 3 | |
| Risk analysis | 3 | |
| Sampling for disease surveys | 2 | |
| Outbreak investigation | 2 | |
| Zoonoses: rabies, brucellosis, tuberculosis and anthrax | 2 | |
| Zoonoses: leptospirosis, glanders, KFD, avian influenza and Japanese encephalitis | 2 | |
| One Health | 2 | |
| Transboundary animal diseases and WOAH | 2 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
In a study of mastitis, cows kept on straw yards had more mastitis, but these cows were also older on average, and age independently increases mastitis risk. Age here is best described as a:
A. Confounder
A confounder is associated with the exposure, is an independent cause of the outcome and is not on the causal pathway. Age meets all three. It can be controlled by stratification, matching or multivariable analysis. An effect modifier changes the size of the effect across strata, which is a different concept.
Further reading: Thrusfield M et al., Veterinary Epidemiology, 4th ed.
A test with sensitivity 95% and specificity 98% is used to screen a population in which true prevalence is 1%. What is the positive predictive value?
C. About 32%
PPV = P x Se/[P x Se + (1 - P)(1 - Sp)] = 0.0095/(0.0095 + 0.0198) = 0.324. At low prevalence false positives outnumber true positives, even with a good test. About 3% is the apparent prevalence (0.0095 + 0.0198 = 0.029), not PPV. 95% is the PPV the same test would reach at about 30% prevalence.
Further reading: Thrusfield M et al., Veterinary Epidemiology, 4th ed.
A serological survey finds apparent prevalence of 12% using a test with sensitivity 90% and specificity 95%. What is the estimated true prevalence (Rogan-Gladen)?
B. About 8.2%
True prevalence = (AP + Sp - 1)/(Se + Sp - 1) = (0.12 + 0.95 - 1)/(0.90 + 0.95 - 1) = 0.07/0.85 = 0.082. 13.3% is AP/Se, which ignores false positives; 7% forgets the denominator.
Further reading: Thrusfield M et al., Veterinary Epidemiology, 4th ed.
Under the WTO SPS Agreement, if a country wants an import measure stricter than the relevant WOAH standard, it must:
D. Justify it with a scientific risk assessment
The SPS Agreement allows a higher level of protection than international standards only when it is based on scientific justification or a risk assessment. WOAH is the recognised standard-setting body for animal health.
Further reading: WOAH Terrestrial Animal Health Code
According to the WOAH Manual criteria, an avian influenza isolate is classified as highly pathogenic if it:
D. Has an intravenous pathogenicity index above 1.2 in six-week-old chickens
HPAI is defined by an IVPI above 1.2 in six-week-old chickens, or at least 75% mortality in four- to eight-week-old chickens inoculated intravenously, or, for H5 and H7 viruses, a haemagglutinin cleavage site with multiple basic amino acids similar to known HPAI viruses. The N subtype does not define pathogenicity.
Further reading: WOAH Manual of Diagnostic Tests and Vaccines for Terrestrial Animals
Which event does NOT by itself require an immediate notification to WOAH?
D. A continuing, stable level of a listed disease already reported as present
Immediate notification covers first occurrences, recurrences after declared eradication, new strains, sudden unexpected changes in distribution, incidence or severity, and emerging diseases of significance. A stable endemic situation is reported in six-monthly reports.
Further reading: WOAH Terrestrial Animal Health Code
Ten here, 28 in the app. The Laisha app has every practice question we have written to AVMA ABVS-recognised specialty boards in this subject, marked as you go, with timed papers, a jump-to-unanswered list and a certificate when you pass at 70 per cent.
Free for ten days, then one subscription of US$10 a month. We would rather say so here than have you find it later.
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