Public Health and Zoonoses – BCSE Study Guide

Overview and Clinical Importance

Public health and zoonoses represent a critical intersection where veterinary medicine directly impacts human health. Veterinarians serve as frontline defenders against zoonotic diseases, play essential roles in food safety programs, and increasingly contribute to the One Health approach that recognizes the interconnection of human, animal, and environmental health.

The BCSE tests candidates on their understanding of major zoonotic diseases, rabies prevention protocols, food safety principles including HACCP, and the One Health framework. These topics are increasingly relevant as approximately 60% of all known infectious diseases in humans originate from animals, and 75% of emerging infectious diseases are zoonotic in origin.

Section 1: Major Zoonotic Diseases

Zoonotic diseases are infectious diseases that can be transmitted between animals and humans. Understanding these diseases is fundamental to veterinary public health practice and essential for BCSE success.

Classification of Zoonotic Diseases

Zoonotic diseases can be classified by causative agent (bacterial, viral, parasitic, fungal, prion) or by transmission route (direct contact, indirect contact, vector-borne, foodborne, waterborne).

[Include Image: Figure 1. Zoonotic Disease Transmission Routes Diagram - showing direct, indirect, vector-borne, and foodborne pathways]

Major Bacterial Zoonoses

MEMORY AID - Leptospirosis Mnemonic - LEPTO

L = Leptospira spirochete, E = Environmental contamination (water/soil), P = Produces renal and hepatic disease, T = Transmitted via urine contact, O = Occupational risk (farmers, veterinarians, sewer workers)

Major Viral Zoonoses

MEMORY AID - Rabies Reservoir Animals in US - SCARF-B

S = Skunks (Midwest/California), C = Coyotes (Texas), A = Raccoons (Eastern US), R = Raccoons repeated for emphasis, F = Foxes (Alaska, Arizona), B = Bats (EVERYWHERE in US - only reservoir found in all 48 contiguous states)

Major Parasitic Zoonoses

MEMORY AID - Toxoplasma Life Cycle - CAT MEAT

CAT = Cats shed oocysts (definitive host), M = Meat (tissue cysts in undercooked meat), E = Environment (oocysts sporulate in soil), A = Acquired by ingestion, T = Tachyzoites spread to tissues

Vector-Borne Zoonoses

MEMORY AID - Tick-Borne Disease Vectors - IDLE

I = Ixodes transmits Lyme, Anaplasmosis, Babesiosis, D = Dermacentor transmits RMSF, Tularemia, L = Lone Star tick transmits Ehrlichiosis, STARI, E = Each tick has specific disease associations - know your vectors!

Section 2: Rabies Prevention and Management

Rabies remains one of the most important zoonotic diseases worldwide, causing approximately 59,000 human deaths annually, primarily in Asia and Africa. In the United States, rabies is well-controlled through vaccination programs, but veterinarians must understand prevention protocols, post-exposure management, and surveillance requirements.

[Include Image: Figure 2. Rabies Virus Electron Micrograph - bullet-shaped Lyssavirus particles]

Rabies Virus Biology

Rabies virus is a negative-sense, single-stranded RNA virus belonging to the family Rhabdoviridae, genus Lyssavirus. The virus has a distinctive bullet-shaped morphology and encodes five structural proteins.

Key characteristics:

The virus is highly neurotropic, traveling via peripheral nerves to the central nervous system. The incubation period is highly variable, typically 3-8 weeks but can range from days to over a year, depending on the bite location and viral load. Once clinical signs appear, rabies is nearly 100% fatal in unvaccinated individuals.

Negri bodies are intracytoplasmic inclusions found in neurons (especially hippocampal pyramidal cells and cerebellar Purkinje cells) that are pathognomonic for rabies but are only present in approximately 70-80% of cases.

Rabies Vaccination in Animals

The AVMA Model Rabies Control Document and the Compendium of Animal Rabies Prevention and Control provide guidelines for rabies vaccination in domestic animals.

Post-Exposure Management

Management of animals exposed to rabies depends on their vaccination status and the circumstances of exposure.

Dogs, Cats, and Ferrets That Bite Humans

Regardless of vaccination status, healthy dogs, cats, or ferrets that bite a person should be confined and observed for 10 days. This observation period is based on studies showing that if the animal is shedding rabies virus in saliva at the time of the bite, it will develop clinical signs within 10 days.

Key points for the 10-day observation:

Animals should be observed by or under the supervision of a veterinarian. Rabies vaccination should NOT be administered during the observation period (to avoid confusing vaccine reactions with rabies signs). Any illness should be reported immediately. If clinical signs develop, the animal should be euthanized and the brain submitted for testing.

Domestic Animals Exposed to Rabies

MEMORY AID - Rabies Observation Periods - 10-45-120

10 days = Observation for biting dogs/cats/ferrets (regardless of vaccination status), 45 days = Observation for VACCINATED animals exposed to rabies, 120 days (4 months) = Quarantine for UNVACCINATED animals exposed to rabies (if immediate vaccination given, otherwise 6 months)

Pre-Exposure Prophylaxis for Veterinary Personnel

Veterinary professionals are classified in Risk Category 3 by the CDC Advisory Committee on Immunization Practices (ACIP). Current recommendations (updated May 2022) include:

Primary series: 2 doses of rabies vaccine (Day 0 and Day 7) administered intramuscularly in the deltoid area.

Titer check: A one-time rabies antibody titer check between 1-3 years after the primary series, with a booster if titer is less than 0.5 IU/mL.

Serial titer testing every 2 years is NO LONGER recommended for Risk Category 3 personnel. The rationale is that veterinary professionals are likely to recognize exposures and seek appropriate post-exposure treatment.

[Include Image: Figure 3. Rabies Pre-Exposure and Post-Exposure Protocol Flowchart]

Section 3: Food Safety and HACCP

Veterinarians play critical roles in food safety through meat inspection, herd health programs, and ensuring food animals are fit for human consumption. The Hazard Analysis and Critical Control Point (HACCP) system is the internationally recognized framework for food safety management.

Veterinary Role in Food Safety

The Food Safety and Inspection Service (FSIS) of the USDA employs veterinarians (Public Health Veterinarians or PHVs) to oversee meat, poultry, and egg product inspection in approximately 6,800 establishments across the United States.

Veterinary responsibilities include:

Antemortem inspection: Evaluating live animals for signs of disease, injury, or conditions that would render them unfit for human food. Animals are classified as passed, suspect, or condemned.

Postmortem inspection: Examining carcasses and viscera for pathological conditions that indicate disease or render product unsafe or unwholesome.

HACCP plan verification: Ensuring establishments implement and follow their HACCP plans correctly.

Disposition decisions: Making final determinations on carcasses and parts regarding fitness for human consumption.

The Seven Principles of HACCP

HACCP is a systematic, science-based approach to food safety that identifies, evaluates, and controls hazards that are significant for food safety. It was developed in the 1960s for NASA's space program and has since become the foundation of modern food safety programs worldwide.

[Include Image: Figure 4. HACCP System Flow Diagram showing the seven principles in sequence]

MEMORY AID - HACCP 7 Principles - HA-CCP MCVR

H = Hazard analysis (Principle 1), A = (identify) CCPs (Principle 2), C = Critical limits (Principle 3), C = (monitor) CCPs (Principle 4), P = Problem correction/corrective actions (Principle 5), M = Make sure it works/verification (Principle 6), C = Complete records (Principle 7), V = Verification, R = Records. Alternative: 'HACCPs Make CVs Right'

Types of Hazards in Food Safety

Prerequisite Programs

HACCP does not operate in isolation. Prerequisite programs including Good Manufacturing Practices (GMP), Good Hygiene Practices (GHP), and Sanitation Standard Operating Procedures (SSOPs) must be in place before implementing HACCP.

SSOPs are written procedures describing daily sanitation activities. Federal regulations require meat and poultry establishments to maintain SSOPs addressing:

Pre-operational sanitation: Cleaning and sanitizing procedures performed before operations begin each day.

Operational sanitation: Practices during production to prevent contamination.

SSOP requirements include daily monitoring, corrective actions when standards are not met, and record-keeping.

MEMORY AID - Prerequisite Programs - GMP GHP SSOP

G = Good Manufacturing Practices (facility, equipment, personnel), M = Maintenance of clean facilities, P = Personnel hygiene and training, G = Good Hygiene Practices (universal standards), H = Hygienic design and construction, P = Pest control, S = Sanitation Standard Operating Procedures, S = Specific to each establishment, O = Operational and pre-operational, P = Prevents contamination before HACCP

Section 4: The One Health Concept

One Health is a collaborative, multisectoral, and transdisciplinary approach that recognizes the interconnection between people, animals, plants, and their shared environment. It is increasingly recognized as essential for addressing complex health challenges at the human-animal-environment interface.

[Include Image: Figure 5. One Health Venn Diagram showing intersection of Human Health, Animal Health, and Environmental Health]

Definition and Historical Context

The One Health High-Level Expert Panel (OHHLEP), established by FAO, UNEP, WHO, and WOAH (formerly OIE), defines One Health as:

'One Health is an integrated, unifying approach that aims to sustainably balance and optimize the health of people, animals and ecosystems. It recognizes that the health of humans, domestic and wild animals, plants, and the wider environment (including ecosystems) are closely linked and interdependent.'

The concept builds on historical precedents including Rudolf Virchow's 19th-century observations on zoonoses and Calvin Schwabe's 'One Medicine' concept from the 1960s. The modern One Health movement gained momentum in the early 2000s following outbreaks of SARS, avian influenza, and other emerging zoonotic diseases.

Key One Health Issues

One Health Framework in the United States

In January 2024, the United States established the U.S. One Health Coordination Unit (U.S. OHCU) with shared leadership between CDC, USDA, and the Department of the Interior. In January 2025, the U.S. OHCU released the National One Health Framework to Address Zoonotic Diseases and Advance Public Health Preparedness (NOHF-Zoonoses).

Key federal partners include:

CDC (Centers for Disease Control and Prevention): Human disease surveillance, epidemiology, laboratory diagnostics, public health response.

USDA (United States Department of Agriculture): Animal health through APHIS-VS, food safety through FSIS, agricultural research.

DOI (Department of the Interior): Wildlife health through USGS National Wildlife Health Center, ecosystem management.

FDA (Food and Drug Administration): Drug and feed safety, Center for Veterinary Medicine.

The U.S. OHCU includes 24 federal agencies working to prevent, detect, and respond to zoonotic disease threats and other One Health issues.

Veterinarian's Role in One Health

Veterinarians are uniquely positioned to contribute to One Health initiatives because of their training in comparative medicine, epidemiology, public health, and their daily interactions with animals and their environments.

MEMORY AID - One Health Partners - CAVE

C = CDC (human health), A = Agriculture (USDA - animal health, food safety), V = Veterinarians (comparative medicine, surveillance), E = Environment (DOI, EPA - wildlife, ecosystems). Remember: One Health requires partners from all sectors working in a CAVE of collaboration!

U.S. Priority Zoonotic Diseases

In 2017, the CDC, DOI, and USDA convened a One Health Zoonotic Disease Prioritization (OHZDP) workshop to identify zoonotic diseases of greatest national concern. The eight priority diseases identified were:

MEMORY AID - US Priority Zoonoses - BLISWRAP

B = Brucellosis, L = Lyme disease, I = Influenza (zoonotic), S = Salmonellosis, W = West Nile virus, R = Rabies, A = (coronaviruses - SARS, MERS), P = Plague

Zoonotic Diseases

Approximately 60% of human infectious diseases are zoonotic; 75% of emerging diseases are zoonotic in origin.

Know the major bacterial (brucellosis, leptospirosis, anthrax, Q fever), viral (rabies, influenza, West Nile), and parasitic (toxoplasmosis, cryptosporidiosis) zoonoses.

Understand transmission routes: direct contact, indirect contact, vector-borne, foodborne, and waterborne.

Recognize reportable diseases and veterinary reporting obligations.

Rabies

Rabies is nearly 100% fatal once clinical signs appear; Negri bodies are pathognomonic but only present in 70-80% of cases.

Remember observation periods: 10 days for biting animals, 45 days for vaccinated exposed animals, 4-6 months for unvaccinated exposed animals.

An animal is 'currently vaccinated' only if at least 28 days post-primary vaccination and within the labeled duration of immunity.

Pre-exposure prophylaxis for veterinary personnel: 2-dose primary series; one-time titer check at 1-3 years.

HACCP

Seven principles: Hazard Analysis, CCPs, Critical Limits, Monitoring, Corrective Actions, Verification, Record-keeping.

Hazards are biological, chemical, or physical.

Critical limits are measurable criteria; monitoring describes how to measure; corrective actions describe responses to deviations.

Prerequisite programs (GMPs, SSOPs) must be in place before HACCP can be effective.

One Health

One Health recognizes the interconnection of human, animal, and environmental health.

Key issues: zoonoses, antimicrobial resistance, food safety, vector-borne diseases, climate change.

U.S. OHCU includes CDC, USDA, and DOI with 24 federal agency partners.

Veterinarians contribute through surveillance, outbreak investigation, antimicrobial stewardship, food safety, and public education.