Zoonotic diseases remain a major and ongoing challenge to global public health. Accounting for more than half of all known infectious diseases, zoonoses exert profound impacts on human health, animal welfare, and socioeconomic stability worldwide. Their significance continues to grow as global travel, climate change, and ecological disruption increase the frequency and scale of outbreaks.
Increased human-animal contact also plays an important role in zoonotic disease incidence. The avian influenza (H5N1) outbreaks, leptospirosis, and rabies underscore their potential to cause widespread morbidity, mortality, and economic loss.
Related CE for veterinarians: Avian Influenza and Highly Pathogenic Avian Influenza
Veterinarians play a significant role within the One Health framework, serving as the first line of defense against zoonotic threats through early detection, surveillance, and prevention. Their role extends beyond animal care to safeguard public health and maintain ecosystem balance.
This article aims to update licensed veterinarians on emerging zoonotic diseases, highlight best practices for prevention and control, and reinforce the scope of professional responsibilities essential to addressing an increasingly complex epidemiological landscape.
The scope and impact of zoonoses
Zoonotic diseases account for a substantial portion of the human infectious disease burden. Experts estimate that roughly 60% of human pathogens are zoonotic in origin, and up to 75% of emerging infectious diseases fall into that category (Bidaisee and Macpherson).
The global impact is multifaceted, encompassing economic losses from livestock morbidity and mortality, trade restrictions, and substantial healthcare expenditures. The public health impact is measured in global morbidity and mortality rates, strain on healthcare systems, and diminished human productivity.
These diseases also severely affect animal welfare in both companion animal practice (e.g., leptospirosis, toxoplasmosis) and livestock practice (e.g., highly pathogenic avian influenza, brucellosis). For example, outbreaks traced to animal reservoirs can trigger broad social consequences, including trade restrictions, livestock culling, and public fear. (Deiana, et al.)
Therefore, a profound understanding of zoonotic transmission and control is essential across all sectors of veterinary medicine. Understanding this broad scope sets the stage for appreciating why every veterinary professional must be alert to zoonoses, not just as animal-health issues but as public-health imperatives.
Common and emerging zoonotic diseases
Zoonotic diseases are caused by a wide array of infectious agents, from bacteria and viruses to parasites and fungi. Each present distinct challenges for both animal and human health. For veterinarians, understanding how these diseases spread and their clinical impact is vital for early detection, effective prevention, and successful control measures.
Bacterial zoonoses
| Disease | Mode of Transmission | Prevention |
| Leptospirosis | Through contact with urine or contaminated water from infected animals, particularly rodents, livestock, and dogs. | Veterinarians play a vital role in vaccination, rodent control, and client education on environmental hygiene. |
| Salmonellosis | From contaminated food or animal products. Can spread from asymptomatic carriers such as reptiles or poultry. | Strict biosecurity and hygiene measures in clinics and farms. |
| Brucellosis | Direct contact with infected reproductive materials or ingestion of unpasteurized animal products. | Early detection and reporting are key to preventing occupational infection. |
Viral zoonoses
| Disease | Mode of Transmission | Prevention |
| Rabies | Through the saliva of an infected animal, most commonly by a bite, but also through scratches, open wounds, or contact with mucous membranes. | Mass vaccination of dogs and wildlife management are cornerstones of control. |
| Avian influenza (H5N1) | Primarily through direct or close contact with infected birds or their contaminated environments. | Avoid contact with sick or dead birds and their droppings, and do not visit live bird markets or poultry farms. |
| Nipah virus | Primarily through contact with infected animals (like fruit bats and pigs) or contaminated food (like raw date palm sap), but also through person-to-person contact. | Good hygiene, including frequent hand washing, and by avoiding close contact with infected individuals, who should wear masks if they develop symptoms. |
| Hantavirus | Transmitted by rodent excreta. | Avoiding contact with bats and sick pigs, and preventing the contamination of food and drinks like raw date palm sap |
Parasitic zoonoses
| Disease | Mode of Transmission | Prevention |
| Toxocariasis | Via ingestion of embryonated eggs of Toxocara canis from contaminated soil | Routine deworming and hygiene education prevent human infection. |
| Echinococcosis (Echinococcus granulosus) | Ingestion of parasite eggs shed by dogs can cause cystic lesions in human organs. | Deworming dogs and proper offal disposal |
Fungal zoonoses
| Disease | Mode of Transmission | Prevention |
| Dermatophytosis (Ringworm) | Direct contact or contaminated fomites | Isolation of infected animals and thorough environmental disinfection. |
Emerging threats
| Disease | Mode of Transmission | Prevention |
| SARS-CoV-2 | Transmission primarily occurs via respiratory droplets. | Veterinarians must employ PPE during animal examinations and sample collection. |
| Monkeypox virus | Through close contact with infected animals or contaminated materials | Veterinary staff working with exotic pets or wildlife should maintain strict biosafety measures. |
| West Nile virus | Through the bite of an infected mosquito | Protection from mosquito bites by using insect repellent, wearing protective clothing, and avoiding mosquitoes during peak activity times like dawn and dusk. |
Occupational risks for veterinarians
Veterinarians experience unique occupational hazards due to their routine, close contact with animals, biological materials, and potentially infectious agents. Whether in clinics, shelters, or out in the field, they can be exposed to zoonotic hazards through direct animal handling, contaminated equipment, or contact with infectious aerosols and bodily fluids.
Pathogens like Leptospira, Brucella, and Salmonella can be transmitted via mucous membranes or contact with open wounds when handling infected animals or tissues. Furthermore, aerosolized agents, such as Coxiella burnetii (Q fever) or Chlamydia psittaci (psittacosis), pose significant inhalation risks, especially during obstetric procedures or handling certain bird species.
Procedures like necropsy and laboratory work inherently increase exposure to contaminated tissues, fluids, and instruments, strongly emphasizing the critical need for strict biosafety measures and rigorous personal protective equipment (PPE) protocols in all veterinary settings.
Best practices: Biosecurity and occupational risk reduction
Minimizing occupational risk requires strict adherence to established protocols. The diligent use of personal protective equipment (PPE)—including appropriate gloves, respiratory masks (such as N95s for aerosol risks), face shields, and protective clothing—is essential for creating effective physical barriers against zoonotic agents.
Equally critical for breaking the chain of transmission are meticulous procedures for hand hygiene, proper biomedical waste disposal, and thorough disinfection practices for equipment and surfaces. Veterinarians can protect themselves and their staff from infection by creating a strong, proactive safety culture in their workplaces. This also helps to build public trust in the profession’s strong commitment to One Health principles.
Diagnosis, reporting, and control measures
Timely and accurate identification of zoonotic infections is essential for preventing widespread transmission and mitigating public health threats. Diagnostic vigilance demands that veterinarians identify atypical or ambiguous clinical manifestations, as these may suggest a zoonotic disease.
Symptoms may include unexplained fever, neurological problems, or reproductive failures. A comprehensive history of animal exposure, travel, vaccination, and interaction with wildlife or vectors helps case identification.
Importance of diagnostic testing and collaboration
Laboratory confirmation through reliable and standardized diagnostic testing is absolutely essential for the accurate case management of zoonotic diseases in both animals and humans. This important step provides definitive identification of the causative pathogen so that appropriate treatment and prevention protocols can be implemented.
Effective disease control relies upon collaboration with accredited diagnostic laboratories and local public health agencies. This partnership guarantees timely identification of emerging or atypical cases, significantly enhances surveillance data accuracy. It supports coordinated response strategies across the human and animal health sectors. Veterinarians are responsible for ensuring samples are properly collected and submitted, thereby contributing high-quality data to the broader One Health system.
Legal and ethical obligations
Veterinarians are legally and ethically required to notify the relevant regulatory authorities of any notifiable zoonotic diseases. Public health interventions, including outbreak containment, vector control, and contact tracing, are made possible by prompt reporting.
Effective zoonosis prevention relies on stringent infection control measures. Essential strategies include isolation or quarantine of suspected cases, thorough disinfection of facilities and equipment, vector control, and consistent compliance with animal vaccination protocols. This is particularly vital for high-risk diseases such as rabies and leptospirosis.
The comprehensive understanding of zoonotic diseases is not merely an academic exercise. It is a foundational element of modern veterinary practice and a public health imperative. The increasing frequency of outbreaks and the interconnectedness of human and animal health underscore the veterinarian’s indispensable role as the primary watchdog within the One Health framework.
References
- Bidaisee, S., & L Macpherson, C. N. (2014). Zoonoses and One Health: A Review of the Literature. Journal of Parasitology Research, 2014, 874345. https://doi.org/10.1155/2014/874345
- Deiana, G., Arghittu, A., Dettori, M., & Castiglia, P. (2023). One World, One Health: Zoonotic Diseases, Parasitic Diseases, and Infectious Diseases. Healthcare, 12(9), 922. https://doi.org/10.3390/healthcare12090922
