ANIMAL FACTORS RELATING TO DOG AND CAT BITE INCIDENTS IN HUMANS continued
than dog bites due to their deep penetrating nature. Common species identified from cat bites include: Pasteurella spp. (particularly P. multocida ), Streptococcus spp., Staphylococcus spp. (S. epidermidis, S. warneri), Moraxella spp., Neisseria spp., Corynebacterium spp., and mixed anaerobes. 8 Bartonella henselae, the causative agent of cat-scratch disease, may be found in the oral cavity of cats and be transmitted by biting.
• Although not frequently isolated from bite wounds (perhaps due to fastidious culture requirements) Capnocytophaga canimorsus is an important zoonotic pathogen that can cause severe and potentially fatal septicaemia in patients without a functional spleen. The bacterium is a normal inhabitant of the canine and feline oral cavity, with carriage rates of up to 74% in dogs and 57% in cats. 10
HUMAN FACTORS RELATING TO DOG AND CAT BITE INCIDENTS IN HUMANS
• Reported human risk factors for dog and cat bites: 5,11,12 - Humans bitten by dogs are more likely to be male and living in a household with dogs. Overall, two-thirds of dog bite victims are bitten by their own dog, or a dog known to them. Young children are reported to be a greatest risk of dog bites, and the highest rate of serious injury from dog bites is in children under 5 years of age. It is reported that approximately half of all bite wounds in children involve the face and scalp. - Humans bitten by cats are more likely to be female, with two-thirds aged between 20 and 35.
• Dog and cat bites are a frequently reported occupational injury for veterinarians and veterinary nurses, and those working in other pet related occupations (e.g. grooming facilities, shelters, kennels). In one Australian study, 48% of veterinarians reported dog bites resulting in skin penetration and 67% reported a cat bite or scratch with skin penetration in the previous 12 months. 13 Male veterinarians were more likely to have experienced a dog or cat bite injury. 13 • A study from the United Kingdom reported an occupational risk for dog bites for individuals involved in delivery services. 14
CLINICAL DISEASE AND MANAGEMENT
onset of severe, localised pain compared with other bacterial infections (e.g. due to Staphylococcus aureus ). 8 Presence of Pasteurella spp. on culture of human wounds should prompt further investigation into a history of an animal bite that may not have been elucidated on initial clinical history. In contrast to dog and cat bite wounds, Pasteurella spp. are not typically associated with human bite wounds. The bacterium Eikenella corrodens is commonly associated with infected human bite wounds, and its presence in an infected bite wound may indicate a human rather than animal source. • Capnocytophaga canimorsus bacteraemia is a rare but significant sequela to dog, and to a lesser extent, cat bites. Risk factors for severe systemic disease include individuals without a functional spleen and those with a history of alcoholism, although cases have been reported in patients without identifiable risk factors. 10 Capnocytophaga cases present with septic shock, meningitis, peripheral gangrene, endocarditis or eye infections. A case fatality rate of 26% has been reported. 10 • Psychological trauma, including fear, anxiety and post- traumatic stress disorder are potential sequelae of animal bite incidents, and should be managed appropriately.
• It is estimated that 10–20% of bite wounds become infected, with infection more common following a cat bite than a dog bite. 12 In addition to physical injury present at the site, clinical signs relating to infection may include cellulitis, abscess formation, or enlarged local lymph nodes. • Particular risks for post-bite infection include: - Patient characteristics: immunosuppression (AIDS, cirrhosis, asplenism, cancer, neutropenia, diabetes, and treatment with corticosteroids or immunosuppressants). 12 - Wound characteristics: puncture wounds; tissue devitalisation from crush wounds; bone, joint or tendon involvement; location on the extremities; or delayed treatment. - Species characteristics: cat bite wounds have a higher risk of infection than dog bites. Cat bite injuries are often less overt (potentially resulting in delayed diagnosis) but can be more penetrating, resulting in septic arthritis and osteomyelitis. • Infection with Pasteurella spp. is common following an animal bite, and is typically associated with a shorter latency period (time from bite to onset of signs of infection) and an abrupt
CONTENTS
39 Companion Animal Zoonoses Guidelines
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