Zoonoses and Antimicrobial Resistance

Subject – Environment

Context – Antimicrobial Awareness Week 2021: Zoonoses as a driver for antimicrobial resistance

Concept –

In recent years, the use, abuse and misuse of antimicrobials in both, the human and livestock sector, has resulted in large-scale antimicrobial resistance (AMR) among various pathogens and more so, in bacterial pathogens.
AMR occurs naturally over time, usually through genetic changes which is a part of natural evolution. The resistant organisms are found in people, animals, foods, plants and the environment which can spread between and within the sectors.
AMR, particularly antibacterial resistance (ABR) is frequently reported at the interface of human, animal and environment indicating the role of industry, farming, and veterinary practices in ABR in addition to human health practices.

Zoonosis

A zoonosis is an infectious disease that has jumped from a non-human animal to humans.
Zoonotic pathogens may be bacterial, viral or parasitic, or may involve unconventional agents and can spread to humans through direct contact or through food, water or the environment.
Zoonoses comprise a large percentage of all newly identified infectious diseases as well as many existing ones.
- Researchers estimate 3/4ths of new, emerging diseases are zoonotic, with the vast majority coming from wildlife.
- Some diseases, such as HIV, begin as a zoonosis but later mutate into human-only strains.
- Other zoonoses can cause recurring disease outbreaks, such as Ebola virus disease and salmonellosis. Still others, such as the novel coronavirus that causes COVID-19, have the potential to cause global pandemics.
Antimicrobial resistance is a complicating factor in the control and prevention of zoonoses. The use of antibiotics in animals raised for food is widespread and increases the potential for drug-resistant strains of zoonotic pathogens capable of spreading quickly in animal and human populations.
World Zoonoses Day is celebrated on July 6th each year and commemorates the work of Louis Pasteur, who developed the first vaccine.
59,000 people die each year from rabies, a leading zoonotic disease.

Classification of Zoonoses

According to the etiological agents

Bacterial zoonoses :- e.g. anthrax, brucellosis, plague, leptospirosis, salmonellosis, lyme disease
Viral zoonoses :- e.g. rabies, arbovirus infections, KFD, yellow fever, influenza, CCHF
Rickettsial zoonoses :- e.g. murine typhus, tick typhus, scrub typhus, Q-fever
Protozoal zoonoses :- e.g. toxoplasmosis, trypanosomiasis, leishmaniasis
Helminthic zoonoses :- e.g. echinococcosis (hydatid disease), taeniasis, schistosomiasis, dracunculiasis
Fungal zoonoses :- e.g. deep mycosis – histoplasmosis, cryptococcosis, superficial dermatophytes
Ectoparasites :- e.g. scabies, myiasis

According to the mode of transmission

Direct zoonoses – These are transmitted from an infected vertebrate host to a susceptible host (man) by direct contact, by contact with a fomite or by a mechanical vector. The agent itself undergoes little or no propagative or developmental changes during transmission, e.g. rabies, anthrax, brucellosis, leptospirosis, toxoplasmosis.
Cyclo zoonoses – These require more than one vertebrate host species, but no invertebrate host for the completion of the life cycle of the agent, e.g. echinococcosis, taeniasis
Meta zoonoses – These are transmitted biologically by invertebrate vectors, in which the agent multiplies and/or develops and there is always an extrinsic incubation (prepatent) period before transmission to another vertebrate host e.g., plague, arbovirus infections, schistosomiasis, leishmaniasis.
Sapro zoonoses – These require a vertebrate host and a non-animal developmental site like soil, plant material, pigeon dropping etc. for the development of the infectious agent e.g. aspergillosis, coccidioidomycosis, cryptococosis, histoplasmosis, zygomycosis.

According to the reservoir host

Anthropo zoonoses – Infections transmitted to man from lower vertebrate animals e.g. rabies, leptospirosis, plague, arboviral infections, brucellosis and Q-fever.
Zooanthroponoses – Infections transmitted from man to lower vertebrate animals e.g. streptococci, staphylococci, diphtheria, enterobacteriaceae, human tuberculosis in cattle and parrots.
Amphixenoses – Infections maintained in both man and lower vertebrate animals and transmitted in either direction e.g. salmonellosis, staphylococcosis.

To know about Antibiotic Resistance, please refer August 2021 DPN.