Thursday, 3 September 2015

Zoonosis

ZOONOSES

Definition: Diseases and infections which are naturally transmitted between vertebrate animals and man.

Types:

Anthropozoonoses: Diseases in animals that can be transmitted to man (eg. rabies).

Zooanthroponoses: Diseases in humans that can be transmitted to animals (eg. tuberculosis in cats, monkeys).

Amphixenoses: Diseases affecting humans and animals that can be occasionally transmitted from one to another (eg. staphyloccocal infection).

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:

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

Depending on Clinical manifestations:

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)
Cryptozoonoses: Zoonoses for which there is only infection without symptoms in animals and/or humans. eg.Infection in animals/disease in humans: ornithosisInfection in humans/disease in animals: Ebola

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