ENARE multiprofessional residency: Veterinary Medicine · Brazil · EBSERH / FGV
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 ENARE multiprofessional residency spread across the units of Veterinary Epidemiology & Zoonoses. Difficulty: 21 easy, 49 medium, 13 hard.
| Epidemiological study designs | 10 | |
| Evaluation of diagnostic tests: sensitivity and specificity | 10 | |
| Measures of disease frequency: incidence, prevalence, morbidity, mortality and case fatality | 8 | |
| Zoonoses: rabies, brucellosis, tuberculosis and anthrax | 8 | |
| Zoonoses: leptospirosis, glanders, KFD, avian influenza and Japanese encephalitis | 8 | |
| Sampling for disease surveys | 7 | |
| Risk analysis | 6 | |
| Transboundary animal diseases and WOAH | 6 | |
| Terms of disease occurrence: sporadic, enzootic, epizootic, panzootic and exotic | 5 | |
| Surveillance | 5 | |
| Outbreak investigation | 5 | |
| One Health | 5 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
During an outbreak of respiratory disease, 40 calves become ill and 6 of them die. What is the case fatality rate?
D. 15%
Case fatality = deaths / cases = 6/40 = 15%. It measures severity. Dividing deaths by the whole herd gives mortality, not case fatality; 17.6% divides by the 34 survivors (6/34).
Further reading: Thrusfield M et al., Veterinary Epidemiology, 4th ed.
A case-control study of salmonellosis in herds gives: cases exposed 40, cases unexposed 60, controls exposed 20, controls unexposed 80. What is the odds ratio?
A. 2.67
OR = ad/bc = (40 x 80)/(20 x 60) = 3200/1200 = 2.67. 2.00 is 40/20, a ratio of exposed counts. 1.56 comes from treating the table as if risks could be computed, which a case-control design does not allow. 0.38 is the inverse.
Further reading: Thrusfield M et al., Veterinary Epidemiology, 4th ed.
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 national system relies on farmers and private veterinarians to report suspect cases of disease to the veterinary authority. This is:
A. Passive surveillance
Passive surveillance depends on reports initiated by others. It is continuous and cheap but misses mild or unrecognised disease. Active surveillance is initiated by the authority through planned sampling.
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.
In a feed-associated outbreak, 80 broilers received a particular batch of feed and 20 became ill. What is the attack rate among birds that received it?
C. 25%
Attack rate = ill / exposed = 20/80 = 25%. The value is compared with the attack rate in birds not fed that batch to implicate or exonerate it. 4% inverts the ratio (80/20 = 4).
Further reading: Thrusfield M et al., Veterinary Epidemiology, 4th ed.
In Kyasanur Forest disease areas, what is the classic early warning of increased virus activity?
D. Deaths of langurs and bonnet macaques in the forest
Monkeys are highly susceptible and die of the infection, amplifying virus for ticks. The disease was discovered after monkey deaths, and monkey death reports trigger investigation and tick control.
Further reading: Thrusfield M et al., Veterinary Epidemiology, 4th ed.
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
Planned testing of a random sample of herds by the veterinary authority to measure brucellosis prevalence is an example of:
C. Active surveillance
The authority initiates and designs the data collection, so it is active surveillance.
Further reading: Thrusfield M et al., Veterinary Epidemiology, 4th ed.
Ten here, 83 in the app. The Laisha app has every practice question we have written to ENARE multiprofessional residency 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.
An AI operating system for agriculture: free guides, manuals and tools written for every country.