Abstracts: Leptospirosis in North Queensland

Background: Leptospirosis is a zoonotic disease with a worldwide distribution, caused by pathogenic serovars in the genus Leptospira. Feral pigs are known carriers of Leptospira species and pig hunting using dogs is a common recreational activity in Queensland, Australia.

Methodology and principal findings: This study aimed to determine the seroprevalence of Leptospira spp. serovars in pig-hunting dogs above the Tropic of Capricorn in Queensland and by establishing the geographic distribution, serovars and incidence of human cases of leptospirosis in Queensland, identify potential overlap between human and canine exposure. We also explored the knowledge and risk-taking behaviours of pig-hunting dog owners towards zoonotic diseases. Ninety-eight pig-hunting dogs deemed healthy by physical examination and owned by 41 people from Queensland had serum submitted for Microscopic Agglutination Testing (MAT) to determine antibody titres against Leptospira serovars, while 40/41 dog owners completed a survey on their knowledge of diseases relating to pig hunting. Human leptospirosis cases (n = 330) notified to Queensland Health between 2015-2018 were analysed. Approximately one quarter (23/87; 26 per cent) of unvaccinated pig-hunting dogs were seropositive to Leptospira spp. Although harder to interpret, 8/11 (73 per cent) vaccinated dogs were seropositive to Leptospira spp. Pig hunters may be more likely to contract leptospirosis compared with the general Queensland population, based on responses from surveyed hunters. The highest concentration of human leptospirosis was in the wet tropics region of Far North Queensland. There was little overlap between the serovars dogs were exposed to and those infecting humans. The dominant serovar identified in unvaccinated dogs was Australis (13/23; 57 per cent), with serovar Arborea (36/330; 10.9 per cent) responsible for the highest number of human leptospirosis cases. Topaz was the second most common serovar in both humans and dogs and was previously unrecorded in Australian dogs. Most hunters surveyed used hand washing as a zoonotic disease risk reduction technique.

Conclusions: Leptospirosis is an emerging disease of growing significance. The infection requires a ‘one health’ approach to understand its epidemiology. With shifting climatic patterns influencing human-animal-environment interactions, ongoing monitoring of diseases like leptospirosis is critical to helping prevent infection of individuals and disease outbreaks.

Bronwyn Orr 1Mark E Westman 1 2Richard Malik 3 4Auriol Purdie 1Scott B Craig 5Jacqueline M Norris 1 6

PLoS Negl Trop Dis. 2022 Jan 18;16(1):e0010100.doi: 10.1371/journal.pntd.0010100. 

1Sydney School of Veterinary Science, The University of Sydney, Sydney, Australia.

2Elizabeth Macarthur Agricultural Institute (EMAI), Woodbridge Road, Menangle, Australia.

3Centre for Veterinary Education, The University of Sydney, Sydney, Australia.

4School of Veterinary and Animal Science, Charles Sturt University, Wagga Wagga, Australia.

5WHO Leptospirosis Laboratory, Public and Environmental Health, Department of Health, Coopers Plains, Australia.

6The Sydney Institute for Infectious Diseases, The University of Sydney, Sydney, Australia.

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