Health

Fatal Uncommon Bacterial Zoonoses

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Anthrax

Dogs are not very susceptible to anthrax and usually develop a subclinical or chronic form of anthrax, with moderate fever, pharyngeal and lingual oedema, and enlarged lymph nodes (McGee et al., 1994). Direct infection of humans from dogs could potentially occur through a bite.

 Chlamydiosis

Chlamydophila psittaci, the agent of psittacosis/ornithosis in humans, is an obligate intracellular parasite that is capable of infecting a wide range of domestic and wild mammals and birds (Arizmendi et al., 1992). In humans, C. psittaci infection is seen most often in exotic pet bird owners and poultry industry workers. Reports of natural and experimentally induced chlamydiosis in dogs are rare. C. psittaci has been isolated in England from the faeces of a dog that had ingested the carcasses of birds known to be infected with the same agent (Fraser and Norval, 1969). Chlamydial conjunctivitis has been described in dogs (Krauss et al., 1988). Additionally, experimental inoculations of dogs with the chlamydial agent of ovine polyarthritis support the notion that dogs are capable of supporting chlamydial infections (Maierhofer and Storz, 1969). Seroprevalence of canine chlamydiosis has not been examined in the United States. However, serosurveys have been conducted in Germany (Werth et al., 1987) where 20% of the dogs tested had C. psittaci antibodies, and in Japan (Fukushi et al., 1985), where 9% of sampled dogs were seropositive. The probable role of dogs in the transmission of C. psittaci to human was suggested in a recent outbreak in Germany (Sprague et al., 2009). C. psittaci infection was reported in four bitches with recurrent kerato-conjunctivitis, severe respiratory distress, and reduced litter size (up to 50% stillborn or non-viable puppies) in a small dog-breeding facility in Germany (Sprague et al., 2009). Cell culture and immunofluorescence examination of conjunctival, nasal, and pharyngeal swabs revealed chlamydial inclusions. PCR and sequencing of ompA amplification products confirmed the presence of C. psittaci genotype C. The zoonotic potential of the pathogen was illustrated by evidence of disease in two children who lived on the premises with the infected dogs. There was circumstantial evidence to suggest infection of dogs and humans may have followed the introduction of two canaries and a parrot into the household.

Corynebacterium ulcerans

Possible transmission of toxigenic Corynebacterium ulcerans from two dogs was suspected in a case of fatal diphtheria-like disease in an elderly woman in the United Kingdom (Hogg et al., 2009). The woman had stayed on a 106-cow dairy farm shortly before becoming ill. Samples were collected on the farm (bulk tank milk and filter; milk samples from eight cows; and pharyngeal swabs from four dogs, two cats, and two guinea pigs). Toxigenic C. ulcerans was isolated from two of the farm dogs and the patient, and the two dogs had indistinguishable ribotype pattern.

Conclusions

Transmission of bacterial zoonoses from dogs to humans is rather uncommon. Transmission from dogs to humans occurs mainly through bites and by faecal shedding. Special attention should be given to young children who are more likely to be bitten by dogs or be in close contact with the pet and its environment. Respecting basic rules of hygiene, regular vaccination of dogs, removal of ectoparasites, and regular use of insecticides are important preventive measures that a dog owner should follow to prevent acquiring bacterial zoonoses from their pet.

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