A seroepidemiological study of canine zoonoses among persons occupationally exposed to dogs

Whitney Sue Krueger

doi:10.17077/etd.2lbnpu4f

Zoonotic diseases continue to emerge and threaten both human and animal health. Overcrowded shelters and breeding kennels create the perfect environment for amplified infectious disease transmission among dogs and present a critical opportunity for zoonotic pathogens to emerge and threaten people who work in close contact with dogs. The objectives of this study were to determine if people with occupational contact with dogs were more likely to have antibodies against Brucella canis, canine influenza virus (CIV), and canine respiratory coronavirus (CRCoV) compared to persons with no dog exposure. A seroepidemiological cohort study was completed, for which 306 canine-exposed and 101 non-canine exposed study subjects enrolled in the study by providing a serum sample and completing a self-administered questionnaire. Evidence of previous exposure was determined by detecting human antibodies against B. canis, CIV and CRCoV. Potential risk factors for seropositivity were examined. Results suggest the overall seroprevalence for B. canis antibodies among humans was 3.2%, with 13 subjects testing positive for antibodies against B. canis by the rapid slide agglutination test. Several canine-exposed occupations/hobbies not considered in previous studies, including jobs in small breeding kennels and dog show handlers, may be at increased risk for exposure to zoonotic B. canis. Occupational risk factors included exposure to a known B. canis positive dog (adjusted OR=7.6; 95% CI, 1..01-48.7) and not wearing personal protective equipment (PPE) when caring for a whelping dog (adjusted OR=6.0; 95% CI, 1.02-65.0). In addition, survey results indicated 35% of breeders were not performing B. canis /italic> testing in their kennels. Even with indication of antibody cross-reactivity, serological results indicated that the canine-exposed population had higher odds for CIV seropositivity, although the odds were not statistically significant. True human infections with CIV may be occurring at a low level of incidence, for which this sample size was not large enough to detect a significant difference between the exposure groups. An inverse association between elevated antibodies against CIV with the occupational exposures of examining dogs and wearing PPE when working with dogs are counter-intuitive, but nonetheless it suggests contact with dogs is playing some role in the evidence of antibody production against CIV. To determine the seroprevalence of antibodies against CRCoV, a competitive enzyme-linked immunosorbent assay (ELISA) was developed to detect human antibodies against CRCoV but control for cross-reacting antibodies against the human coronavirus OC43. All study subjects were negative for antibodies against CRCoV by this competitive ELISA. Overall, these results suggest that exposure to B. canis and CIV is occurring among this study population. Owners and handlers should first ensure the health and safety of the dogs for which there care. To prevent the zoonotic spread of these pathogens to humans, persons in high-risk occupational settings need to be educated of their potential risks, such that they can take proper precautions, including wearing gloves when exposed to a whelping dog and always washing their hands after caring for a sick dog. Lastly, in order to more accurately identify the cross-species spread of these diseases and associated risk factors, prospective studies employing more sensitive serological assays need to be developed. While serological studies have a number of limitations, they are still a valid first tool for identifying emerging zoonotic diseases.

A seroepidemiological study of canine zoonoses among persons occupationally exposed to dogs

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