Zoonosis
According to WHO, a zoonosis is a disease or an infection that is naturally transmissible from vertebrate animals to humans. There are over 200 types of known zoonoses.
Zoonoses can be classified on the basis of etiological agents, transmission cycles or reservoir hosts.
Classification of zoonoses on the basis of etiological agents (causal agent):
1. Bacterial zoonoses (For eg- Brucellosis)
2. Viral zoonoses (For eg- Rabies)
3. Rickettsial and Chlamydial zoonoses (For eg- Q fever)
4. Mycotic zoonoses (For eg- Dermatophytoses)
5. Parasitic zoonoses (For eg- Toxoplasmosis)
Classification of zoonoses on the basis of transmission cycles
1. Direct zoonoses
In direct zoonoses, the disease is directly transmitted from animals to humans through media such as air, or through bites and saliva, contact of mucus membrane with an affected animal, or indirectly through food or mechanical vectors, etc
For eg- Rabies, Scabies
2. Cyclozoonoses
These diseases require more than one vertebrate host (but no invertebrate) for the completion of a lifecycle.
Cyclozoonoses can be of two types:
1. Obligatory cyclozoonoses
In these diseases, the presence of a man is compulsory for the completion of a lifecycle. In this case, man is known as the compulsory/ obligatory host.
For eg- Taeniasis (caused by Taenia solium or Taenia saginata)
2. Non-obligatory cyclozoonoses
In these diseases, the presence of a man is compulsory for the completion of a lifecycle. In this case, man is known as the compulsory/ obligatory host.
For eg- Taeniasis (caused by Taenia solium or Taenia saginata)
3. Metazoonoses
These diseases need both a vertebrate and an invertebrate host for the completion of its lifecycle.
For eg- Plague
4. Saprozoonoses
These zoonoses require a non-animal site to serve either as a true reservoir of infection or as a site for an essential phase of development.
For eg- Animal erysipelas
Classification of zoonoses on the basis of reservoir host
Here is a diagram that will help you understand the classification of zoonoses based on the reservoir hosts easily.
1. Anthropozoonoses
These diseases are transmitted from animal to man in unusual circumstances. Man here is usually cul-de-sac.
For eg- Leptospirosis
2. Zooanthroponoses
These diseases can be transmitted from man to other animals.
For eg- Tuberculosis (human form)
3. Amphixenoses
These diseases can spread from man to animal and animal to man.
For eg- Salmonellosis
