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Marcia B Goldberg, MD
Section Editor
Stephen B Calderwood, MD
Deputy Editor
Elinor L Baron, MD, DTMH


Capnocytophaga canimorsus is a bacterial cause of fulminant sepsis among individuals who have been bitten by a dog; patients at greatest risk include immunocompromised individuals, particularly those with asplenia, functional asplenia, cirrhosis, or history of heavy alcohol use. C. canimorsus and other Capnocytophaga species also cause a variety of other infections, including in immunocompetent hosts.

Issues related to Capnocytophaga infection will be reviewed here. Issues related to initial management of animal and human bites and to soft tissue infections due to dog and cat bites are discussed separately. (See "Clinical manifestations and initial management of animal and human bites" and "Soft tissue infections due to dog and cat bites".)


Capnocytophaga species cause rare but severe infection in humans. The incidence of infection due to C. canimorsus in the general population is low. National surveillance for Capnocytophaga species is not performed in the United States; a national survey in the Netherlands noted 0.67 cases per million per year [1]. The prevalence among immunocompromised hosts is likely substantially higher than that of the general population. The case fatality rate in case series is 28 to 31 percent [2-4]; mortality is high even among patients who are immunocompetent.

C. canimorsus is the most common cause of severe Capnocytophaga infection in humans. Risk factors for C. canimorsus infection include a history of a dog bite and immunocompromise, particularly asplenia, functional asplenia, cirrhosis, or history of heavy alcohol use. Most (72 to 74 percent) of these infections occur in men, with a peak among individuals 50 to 70 years old [1,2,5]. Approximately half (43 to 56 percent) of patients report a history of a dog bite; others report scratches from dogs or occasionally cats or exposure to dogs without bites or scratches [1-4,6].


Capnocytophaga is a genus in the family Flavobacteriaceae. Capnocytophaga species are slow growing, capnophilic ("carbon loving"), facultative anaerobes. They are long, thin, and generally fusiform gram-negative rods (picture 1), which may become pleomorphic with prolonged growth.

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Literature review current through: Nov 2017. | This topic last updated: Sep 29, 2016.
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