DVM Preventive Medicine and Zoonoses 3 — Questions and Answers
Question 1: Q fever is caused by which organism, and what is its primary transmission route to humans in veterinary settings?
- Coxiella burnetii via inhalation of contaminated aerosols during parturition (Correct answer)
- Chlamydia psittaci via direct contact with infected birds
- Rickettsia rickettsii via tick bites
- Bartonella henselae via cat scratches
Correct answer: Coxiella burnetii via inhalation of contaminated aerosols during parturition
Coxiella burnetii causes Q fever and is highly infectious via inhalation of aerosols from birth products, placenta, and amniotic fluid of infected sheep, goats, and cattle.
Question 2: Which epidemiological measure describes the probability that an animal without disease will develop disease during a specific time period?
- Prevalence
- Cumulative incidence (risk) (Correct answer)
- Incidence rate
- Odds ratio
Correct answer: Cumulative incidence (risk)
Cumulative incidence (risk) is the proportion of disease-free animals that develop disease during a defined time period, expressed as a probability.
Question 3: A dairy herd vaccination program for bovine respiratory disease (BRD) should ideally target animals at what time point for maximum efficacy?
- At the time of clinical signs in the first affected animal
- 2-4 weeks before anticipated stress events or high-risk periods (Correct answer)
- Immediately at weaning with no prior preparation
- Only after confirmed pathogen identification via PCR
Correct answer: 2-4 weeks before anticipated stress events or high-risk periods
Vaccinating 2-4 weeks before stress events allows adequate time for protective immune responses to develop before animals face high-risk periods.
Question 4: Which of the following is a DIRECT zoonotic transmission route for Cryptosporidium parvum?
- Mosquito bite
- Fecal-oral contact with infected calf feces (Correct answer)
- Inhalation of spores
- Consumption of raw meat
Correct answer: Fecal-oral contact with infected calf feces
Cryptosporidium parvum oocysts in calf feces are immediately infectious upon passage and can be transmitted to humans via direct fecal-oral contact or contaminated water.
Question 5: In the context of biosecurity, what does 'biocontainment' specifically refer to?
- Preventing new pathogens from entering a facility
- Preventing pathogens already present within a facility from spreading outward (Correct answer)
- Reducing the concentration of pathogens in the environment
- Eliminating all potential disease vectors from a property
Correct answer: Preventing pathogens already present within a facility from spreading outward
Biocontainment refers to measures that prevent pathogens already present within a facility from spreading to other animals, farms, or regions.
Question 6: Which serological test format produces the fewest false positives in a population with low disease prevalence?
- A test with high sensitivity regardless of specificity
- A test with high specificity (>99%) applied to a low-prevalence population (Correct answer)
- Any ELISA regardless of sensitivity/specificity values
- A test selected based on ease of performance rather than accuracy
Correct answer: A test with high specificity (>99%) applied to a low-prevalence population
In low-prevalence populations, positive predictive value is strongly dependent on specificity; a highly specific test minimizes false positives that would otherwise overwhelm true positives.
Question 7: A veterinarian identifies a reportable foreign animal disease suspicion on a farm. What is the FIRST action they should take?
- Begin immediate treatment of all affected animals
- Contact the state veterinarian or USDA APHIS immediately and quarantine the premises (Correct answer)
- Send samples to any commercial laboratory for rapid diagnosis
- Notify the local media to alert surrounding farms
Correct answer: Contact the state veterinarian or USDA APHIS immediately and quarantine the premises
Foreign animal disease suspicions require immediate notification of the state veterinarian or USDA APHIS and implementation of a farm quarantine to prevent potential spread.
DVM Preventive Medicine and Zoonoses 3
Q fever is caused by which organism, and what is its primary transmission route to humans in veterinary settings?