ZOONOSES

Definition: Diseases and infections which are naturally transmitted between vertebrate animals and man. (Ref: W.H.O., 1951, Expert Committee on Zoonoses, WHO tech rep. Ser No 40).

Types:

1. Anthropozoonoses: Diseases in animals that can be transmitted to man (eg. rabies).
2. Zooanthroponoses: Diseases in humans that can be transmitted to animals (eg. tuberculosis in cats, monkeys).
3. Amphixenoses: Diseases affecting humans and animals that can be occasionally transmitted from one to another (eg. staphyloccocal infection).
4. Euzoonoses: Diseases in which humans are an obligatory host of the agent (eg. Taenia solium or T. saginata)

 

Examples:

Some Major Bacterial Etiologic Agents of New Zoonoses

• E. coli O157:H7
• Borrelia burgdorferi (Lyme disease)
• Helicobacter pylori and other spp.
• Ehrlichia chaffeensis (HME)
• Bartonella henselae (Cat scratch Disease)
• Rickettsia felis (Murine typhus like)
• E. Equi/A. phagocytophila (HGE)

Some Major Viral Etiologic Agents of New Zoonoses

• Guanarito virus (Venezuelan hemor. fever)
• Sin nombre virus (Hantavirus Pulm.Syndr.)
• Sabia virus (Brazilian hemorrhagic fever)
• Hendra virus (Equine morbillivirus)
• Australian bat Lyssavirus (Rhabdovirus)
• Menangle virus (paramyxovirus)
• Influenza virus H5N1 (Hong Kong)
• Nipah virus (Paramyxovirus)
• Influenza virus H9N2 (Hong Kong)
• SARS (Coronavirus)

 

Types on the basis of Epidemiological cycle/Modes of transmission:

1. Orthozoonoses: Disease transmission cycle can be completed with only one vertebrate reservoir (eg. rabies).
2. Cyclozoonoses: Diseases whose maintenance cycle requires more than one vertebrate species, but no invertebrate host (eg., hydatid disease, taeniasis).
3. Pherozoonoses (or Metazoonoses): Diseases whose maintenance cycle requires both vertebrates and invertebrates to complete their transmission cycle (eg. arboviruses).
4. Saprozoonoses: Diseases that depend upon inanimate reservoirs or development sites, as well as upon vertebrate hosts (eg. listeriosis)

Depending on Clinical manifestations:

1. Phanerozoonoses: Zoonoses for which symptoms are observed in animals and humans. They may be Iso-symptomatic (Symptoms are the same in humans and animals eg. Rabies, tuberculosis) or Aniso-symptomatic (Symptoms are different in humans and animals eg. Q fever, anthrax)
2. Cryptozoonoses: Zoonoses for which there is only infection without symptoms in animals and/or humans. eg.
   1. Infection in animals/disease in humans: ornithosis
   2. Infection in humans/disease in animals: Ebola

 

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