DVM Preventive Medicine and Zoonoses 2 — Questions and Answers
Question 1: Which zoonotic pathogen is primarily transmitted to humans through contact with infected animal urine, particularly from rodents and livestock?
- Brucella abortus
- Leptospira interrogans (Correct answer)
- Coxiella burnetii
- Francisella tularensis
Correct answer: Leptospira interrogans
Leptospira interrogans is shed in animal urine and can penetrate human skin or mucous membranes, causing leptospirosis.
Question 2: A beef cattle herd is experiencing reproductive losses. Serology confirms Bovine Viral Diarrhea Virus (BVDV). What is the most important control strategy?
- Antibiotic treatment of all animals
- Identify and remove persistently infected (PI) animals (Correct answer)
- Immediate herd depopulation
- Isolation of pregnant cows only
Correct answer: Identify and remove persistently infected (PI) animals
Persistently infected (PI) animals are the primary reservoir of BVDV and shed large amounts of virus continuously, so their identification and removal is essential for control.
Question 3: Which of the following best describes the concept of 'herd immunity threshold' in veterinary preventive medicine?
- The minimum number of animals that must be vaccinated to prevent any disease outbreak
- The proportion of immune individuals needed to prevent epidemic spread in a population (Correct answer)
- The percentage of animals that develop natural immunity after exposure
- The level of maternal antibodies required to protect neonates
Correct answer: The proportion of immune individuals needed to prevent epidemic spread in a population
The herd immunity threshold is the proportion of immune individuals in a population above which disease cannot sustain epidemic spread, calculated as 1 - 1/R0.
Question 4: A veterinarian is asked to advise on controlling Salmonella in a commercial poultry flock. Which intervention is MOST effective at the population level?
- Routine prophylactic antibiotic use in feed
- Competitive exclusion products combined with vaccination (Correct answer)
- Increased stocking density to promote natural immunity
- Vitamin supplementation only
Correct answer: Competitive exclusion products combined with vaccination
Competitive exclusion products introduce beneficial microflora that outcompete Salmonella, and when combined with vaccination, provide the most effective population-level control.
Question 5: Which arthropod vector is responsible for transmitting both Lyme disease (Borrelia burgdorferi) and Anaplasma phagocytophilum in the northeastern United States?
- Dermacentor variabilis
- Ixodes scapularis (Correct answer)
- Amblyomma americanum
- Rhipicephalus sanguineus
Correct answer: Ixodes scapularis
Ixodes scapularis (black-legged tick) is the primary vector for both Borrelia burgdorferi and Anaplasma phagocytophilum in the northeastern and upper midwestern US.
Question 6: In a swine operation, what does the 'all-in/all-out' (AIAO) management system primarily prevent?
- Introduction of new genetic material
- Horizontal transmission of pathogens between age groups (Correct answer)
- Vertical transmission of pathogens from sows to piglets
- Nutritional deficiencies in growing pigs
Correct answer: Horizontal transmission of pathogens between age groups
AIAO management prevents older, immune animals from continuously re-exposing naive younger animals to pathogens, breaking the cycle of horizontal transmission.
Question 7: A dog presents with a wound from an unknown animal. The owner asks about rabies post-exposure prophylaxis (PEP) for themselves. Which statement is correct regarding the dog?
- The dog should be euthanized immediately for brain testing
- If currently vaccinated, the dog should be boostered and observed for 10 days (Correct answer)
- The dog's vaccination status is irrelevant to human PEP decisions
- The dog should receive PEP treatment identical to humans
Correct answer: If currently vaccinated, the dog should be boostered and observed for 10 days
A currently vaccinated dog that bites a human should receive a booster and be observed for 10 days; if it remains healthy, the human exposure is considered non-infectious.
DVM Preventive Medicine and Zoonoses 2
Which zoonotic pathogen is primarily transmitted to humans through contact with infected animal urine, particularly from rodents and livestock?