DVM Zoonotic Diseases and Public Health 5 — Questions and Answers
Question 1: Which of the following best describes the epidemiological concept of 'spillback' in the context of zoonotic diseases?
- When a wildlife pathogen spills into domestic livestock populations
- When a human-adapted pathogen is transmitted back to a wild animal reservoir (Correct answer)
- When a zoonotic disease re-emerges after a period of suppression
- When vector populations rebound after insecticide application ceases
Correct answer: When a human-adapted pathogen is transmitted back to a wild animal reservoir
Spillback describes reverse transmission where a pathogen that originated in animals (or adapted in humans) is transmitted back into a wildlife or domestic animal reservoir.
Question 2: Leptospirosis transmission to veterinary staff most commonly occurs through which route?
- Ingestion of leptospires from contaminated food
- Contact of mucous membranes or abraded skin with urine of infected animals (Correct answer)
- Respiratory inhalation of Leptospira aerosols in enclosed spaces
- Arthropod vector (tick or flea) biting an infected animal then a human
Correct answer: Contact of mucous membranes or abraded skin with urine of infected animals
Leptospires penetrate through mucous membranes or skin abrasions upon contact with urine or urine-contaminated fluids, making urogenital procedures and urine handling highest risk.
Question 3: Monkey B virus (Macacine herpesvirus 1) is an occupational hazard for which group, and what is the case fatality rate in untreated human infections?
- Zoo visitors; approximately 5% fatality rate
- Macaque handlers and laboratory workers; approximately 70-80% fatality rate (Correct answer)
- Veterinary surgeons performing macaque procedures; approximately 30% fatality rate
- Primate sanctuary volunteers; approximately 15% fatality rate
Correct answer: Macaque handlers and laboratory workers; approximately 70-80% fatality rate
B virus causes encephalomyelitis in humans with a 70-80% fatality rate if untreated; macaque handlers and laboratory workers are at primary risk through bites, scratches, or mucosal splash.
Question 4: A veterinarian performing a necropsy on a cow that died acutely without premonitory signs in an anthrax-endemic region should FIRST:
- Open the carcass immediately to collect diagnostic samples
- Examine a blood smear from a peripheral vessel BEFORE opening the carcass (Correct answer)
- Submit the entire carcass to a diagnostic laboratory for full necropsy
- Administer antibiotics to all farm personnel before beginning the necropsy
Correct answer: Examine a blood smear from a peripheral vessel BEFORE opening the carcass
In suspected anthrax, opening the carcass is contraindicated as it exposes spores to oxygen and promotes sporulation; a peripheral blood smear should be examined first to confirm Bacillus anthracis.
Question 5: Which zoonotic pathogen is the most common cause of bacterial foodborne illness in the United States, with poultry being the primary reservoir?
- Salmonella enterica
- Campylobacter jejuni (Correct answer)
- Listeria monocytogenes
- Shiga toxin-producing Escherichia coli (STEC)
Correct answer: Campylobacter jejuni
Campylobacter jejuni is the most frequently identified bacterial cause of foodborne diarrheal illness in the US, with poultry serving as the primary reservoir and undercooked chicken as the primary vehicle.
Question 6: In rabies serosurveillance, what titer of virus-neutralizing antibodies (VNA) is considered acceptable evidence of response to rabies vaccination in dogs under the USDA standard?
- ≥0.1 IU/mL by RFFIT or FAVN
- ≥0.5 IU/mL by RFFIT or FAVN (Correct answer)
- ≥1.0 IU/mL by RFFIT or FAVN
- ≥2.0 IU/mL by RFFIT or FAVN
Correct answer: ≥0.5 IU/mL by RFFIT or FAVN
The WHO and USDA recognize ≥0.5 IU/mL as the minimum acceptable titer by RFFIT or FAVN for demonstrating adequate rabies vaccine response in animals and for international travel requirements.
Question 7: West Nile virus (WNV) surveillance in veterinary public health most commonly uses which sentinel species to detect amplification in a geographic area?
- Wild corvids (crows, ravens) as dead-bird surveillance indicators (Correct answer)
- Domestic pigs as amplifying hosts with regular serosurveillance
- White-tailed deer as primary reservoir with blood sampling
- Horses as the primary maintenance host with mosquito pool testing
Correct answer: Wild corvids (crows, ravens) as dead-bird surveillance indicators
American crows are highly susceptible to WNV and die rapidly after infection; dead crow surveillance is a cost-effective early warning system for WNV amplification in an area.
DVM Zoonotic Diseases and Public Health 5
Which of the following best describes the epidemiological concept of 'spillback' in the context of zoonotic diseases?