Zoonosis

Zoonosis (from the Greek zoon — animal and nosos — disease) is a broad group of infectious diseases whose pathogens naturally circulate among vertebrate animals but can be transmitted to humans under certain circumstances.

Etiology and pathophysiology

Zoonotic pathogens (viruses, bacteria, helminths, protozoa, prions) are evolutionarily adapted to living within their natural reservoirs (wild or domestic animals), often carrying the infection asymptomatically.

The mechanisms of zoonosis transmission are extremely diverse. Infection can occur through the following routes:

• alimentary — consumption of contaminated meat (e.g., in trichinosis);
• contact — bite from an infected animal (for instance, in rabies);
• vector-borne — through bites of blood-sucking arthropods (ticks or mosquitoes);
• airborne — inhalation of dust particles containing discharges from infected animals.

Clinical significance

Zoonoses comprise more than 60% of all known infectious diseases in humans.

From clinical and epidemiological perspectives, their main feature is that for most such pathogens, humans represent a biological “dead end.” Once in the human body, the pathogen cannot be transmitted further (from person to person). For example, a patient with toxocariasis or tick-borne encephalitis is not contagious to others.

Eradicating zoonoses completely is impossible, as this would require eliminating all natural reservoirs. Therefore, the main prevention methods in medicine and veterinary practice include:

• thermal processing of meat;
• strict veterinary and sanitary controls;
• adhering to personal hygiene rules and infection prevention measures;
• control of vectors (disinsection);
• planned vaccination of domestic and farm animals and humans.