Merck Manual

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Professional Version

Zoonotic Diseases


Anna Rovid Spickler

, DVM, PhD, Center for Food Security & Public Health, College of Veterinary Medicine, Iowa State University

Reviewed/Revised Feb 2023 | Modified Jun 2023
Topic Resources

The tables in this topic list zoonotic bacterial Global Zoonotic Diseases: Bacterial and Rickettsial Diseases Global Zoonotic Diseases: Bacterial and Rickettsial Diseases , viral and prion Global Zoonotic Diseases: Viral Diseases and Prion Disease Global Zoonotic Diseases: Viral Diseases and Prion Disease , fungal Global Zoonotic Diseases: Fungal Diseases Global Zoonotic Diseases: Fungal Diseases , and parasitic diseases Zoonotic Diseases: Parasitic Diseases Zoonotic Diseases: Parasitic Diseases . Many proven zoonoses, including some diseases that are rare in humans, organisms that are maintained primarily in humans, some primate diseases, and diseases due to fish and reptile toxins have been omitted. The tables are intended to give a general clinical picture of each disease; current medical texts or review articles should be consulted for a more complete description. Clinical signs are listed; asymptomatic infections can also be assumed to occur in most cases. Many pathogens can cause more severe disease or unusual signs in immunocompromised patients The Spectrum of Illness and the Role of Comorbidities in Zoonosis The spectrum of zoonotic illness varies from skin eruptions or mild, self-limiting infections (easily misdiagnosed as influenza in humans) to serious, life-threatening disease. Some zoonoses... read more .

An indication of the mortality rate among healthy humans has been provided for many infections. However, there is almost always a chance of death whenever lesions can become generalized, vital organs may be affected, secondary infections occur, or the patient is immunocompromised or has other comorbidities. The mortality rate is often influenced by the availability of medical care, and it is generally lower when advanced medical support is available. The risk of death from some bacterial diseases with high mortality rates can be nearly eliminated with prompt antimicrobial treatment.

Information on the geographic range of an organism should be taken as a rough guide. The precise ranges of many pathogens have not been completely determined. Organisms may also expand their range or be eradicated from areas where they were once abundant. A geographic distribution described as worldwide means organisms are widespread and found on all major continents, although they may absent from some areas (eg, polar regions or some islands). In some cases, organisms indicated as being present on a continent may nevertheless have a limited distribution.

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