Epizootic

Epizootic process and zoonotic infections

Epizootic outbreaks are accompanied by the continuous circulation of pathogens among domestic or wild animal populations. A wide variety of pathogens are involved in such chains, including viruses, bacteria, parasitic protozoa, and helminths.

A striking example of a viral pathology is foot-and-mouth disease. This highly contagious disease exhibits a pronounced tendency toward sudden activation and introduction even into regions where outbreaks have not occurred for many decades. Among bacterial threats, anthrax is of exceptional importance: herbivores serve as its reservoir, and pathogen spores survive in the environment for decades, forming persistent soil foci.

Vectors and reservoirs in natural foci

The maintenance of the epizootic process among wild mammals and birds is frequently ensured by arthropods. Ixodid ticks, particularly Ixodes persulcatus (taiga tick), occupy a special place here.

Ticks function not merely as mechanical or specific vectors, but also as a long-term reservoir of infections due to two mechanisms:

• Transphasic transmission: the pathogen persists as the tick transitions from one developmental stage to another (larva — nymph — adult).
• Transovarial transmission: the infectious agent penetrates the egg clutch, ensuring the infection of the next generation of vectors.

Due to this, disease agents of Lyme disease (Borrelia), tick-borne encephalitis, and tularemia continuously circulate in natural biotopes.

Occupational risk and transmission routes to humans

Human infection during epizootics is most often caused by occupational activities or staying in an affected region. The main risk group includes agricultural workers, tannery employees, secondary raw material processing plant workers, and medical personnel.

Infection occurs through direct care of sick livestock, slaughter, skinning, carcass butchering, as well as vector-borne transmission via blood-feeding vectors. Upon the initial detection of dangerous infections (including foot-and-mouth disease) within the healthcare system, the submission of an emergency notification is mandatory.

Complex of antiepizootic and sanitary measures

The eradication of foci requires coordinated veterinary-sanitary and medical actions in three directions:

1. Working with the source: identification, isolation, and deworming or treatment of livestock; monitoring the population of wild rodents (deratization in leptospirosis); safe disposal of dead animals by burning or burial in cattle burial grounds at a depth of at least 2 meters using bleaching powder.
2. Interruption of transmission routes: disinsection in natural foci; disinfection of wastewater and water bodies from manure; technological processing of hides with acid (pickling at a temperature of 20–40 °C).
3. Protection of susceptible individuals: use of personal protective equipment (coveralls, gloves, boots); vaccination of risk groups (against anthrax with STI vaccine, leptospirosis); antibiotic chemoprophylaxis for contacts.

Class and exam questions

What else to study on this topic

• Clinical presentation and leading syndromes of foot-and-mouth disease in humans (intoxication syndrome and exanthema)
• Clinical forms of anthrax: cutaneous, pulmonary, and intestinal
• Medical significance of arachnids: toxic lesions from spider bites (arachnidisms) and parasitization by Demodex folliculorum mites
• Dispensary observation of contact persons and convalescents in infectious disease clinics
• Regimens for emergency medical prophylaxis of leptospirosis in humans with broad-spectrum antibiotics

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.