Dog and Cat Bite Wounds and the Role of Capnocytophaga canimorsus

30-word-abstract
Dog and cat bites have zoonotic infection risks. Sepsis with the bacteria Capnocytophaga canimorsus may be a significant complication. Bite wound infection, antibiotic treatment and prevention will be discussed.

Introduction
An estimated 1,5 million dogs and 2,9 million cats lived in the Netherlands in 2010. These account for an estimated 150,000 dog and cat bites per year, of which approximately 40,000 require medical attention. Substantially more dog bites (94%) occur than cat bites (6%). Three-quarters of the wounds are located in the arm or the hand. Provoked bites, such as disturbing animals while they are eating, are responsible for 67% of the cases. Most bites (64%) involve a pet that belongs to the household of the victim and 90% occur on the pet owner’s property. Peak incidence of animal bites occurs among children aged 5-9 years because they easily misunderstand body language and the behavioral warnings of an animal. In this group, wounds are mainly located in the face.

Bite wounds and infection
Dogs have strong jaws and bites cause typically crushing-type wound and lacerations or tearing of the skin because of their relatively dull teeth. They do not penetrate deeply enough to get bacteria into bones, tendons, or joints. The sharp pointed teeth of cats usually cause puncture wounds and lacerations that can reach into joints and bones and introduce bacteria deep into the tissue. Puncture wounds are very difficult to clean, so a lot of bacteria may be left in the wound.
Infections caused by cat bites generally develop faster than those of dogs. A major concern in all bite wounds is subsequent infection. Especially bites of the hand have a high risk for infection because of the relatively poor blood supply.

Cultures from dog and cat bite wound infections resulted in pathogenic Pasteurella (50% P. canis resp. 75% P. multocida), Streptococcus sp. (46%) and Staphylococcus sp. (23% resp. 35%). Anaerobic pathogens found were Fusobacterium and Bacteroides sp. Sepsis is a potential complication of bite wounds, particularly C. canimorsus sepsis in immunocompromised individuals. Capnocytophaga spp. are facultative anaerobic Gram-negative rods belonging to the genus Flavobacteriaceae. They are subdivided in two groups: the DF-1 group, normal mouth flora of humans like C. ochracea, C. gingivalis, C. haemolytica, C. sputigena and C. granulose, and the DF-2 group with C. canimorsus en C. cynodegmi commensals in the oral flora of dogs and cats but also causing bite wound infections in humans. Van Dam et al. described retrospectively an investigation of 32 patients in the Netherlands during 3 years. Under- reporting is possible because of bacterial overgrowth by other oral flora. DNA-based methods demonstrated that approximately 30% of the dogs and cats in the Nether- lands are carriers of C. canimorsus. Improving diagnostic methods for this bacterium is important because of the complications from a C. canimorsus wound infection such as acute kidney function loss and sepsis. Mortality levels are estimated up to 30%. C. cynodegmi is less virulent. Worldwide only 5 human cases are described.  [...]