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Natural reservoir or nidus, refers to the long-term host of the pathogen of an infectious disease. It is often the case that hosts do not get the disease carried by the pathogen or it is carried as a subclinical infection and so asymptomatic and non-lethal. Once discovered, natural reservoirs elucidate the complete life cycle of infectious diseases, providing effective prevention and control. Examples of natural reservoirs are:

• Field mice, for hantaviruses and Lassa fever
• Marmots, black rats, prairie dogs, chipmunks and squirrels for bubonic plague
• Armadillos and opossums for Chagas disease and several species of New World Leishmania
• Ticks for babesiosis and Rocky Mountain spotted fever
• Ground squirrels, porcupines, and chipmunks for Colorado tick fever
• Mosquitoes for filariasis and malaria
• Snails for schistosomiasis and swimmer's itch
• Pigs for cestode worm infections
• Raccoons, skunks, foxes and bats for rabies
• Shellfish for cholera
• Fowl (ducks and geese) for avian influenza
• Bats, the reservoir for Nipah, Hendra, Rabies and SARS
• Dogs and wild canids for Leishmania infantum, the cause of infantile visceral leishmaniasis
• Cats, for Bartonella (aka Cat scratch disease)
• Gerbils for Leishmania major, the causative agent of cutaneous leishmaniasis in the Old World
• Rock hyrax for Leishmania aethiopica and, probably, certain strains of Leishmania tropica, the causative agents of cutaneous leishmaniasis in the Old World

Some diseases have no non-human reservoir: poliomyelitis and smallpox are prominent examples.

The natural reservoir of some diseases remain unknown. This is the case of the Ebola disease, which is caused by a virus.

[edit] See also

• Zoonosis
• Subclinical infection