Leptospirosis is an emerging infectious disease of pig-hunting dogs and humans in North Queensland

Abstract

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%) of unvaccinated pig-hunting dogs were seropositive to Leptospira spp. Although harder to interpret, 8/11 (73%) 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%), with serovar Arborea (36/330; 10.9%) 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.

Seroprevalence of Coxiella burnetii in pig‐hunting dogs from north Queensland, Australia

“…Pig‐hunting dogs in Qld have been shown to be at high risk for canine heartworm disease 48 and Leptospira spp. exposure, 49 and their exposure rate to C . burnetii suggests another increased infectious disease risk.…”

Detection of Brucella spp. during a serosurvey of pig‐hunting and regional pet dogs in eastern Australia

“…exposure. 40,41 Pig hunters should be aware of the risks posed by pig-hunting to their dogs and take appropriate preventative measures to protect both themselves and their dogs.…”

“…Veterinarians who treat pig‐hunting dogs in Qld and NSW should be aware of the zoonotic risks presented by these dogs, as they have also been previously found to have high rates of Coxiella burnetii and Leptospira spp. exposure 40, 41 . Pig hunters should be aware of the risks posed by pig‐hunting to their dogs and take appropriate preventative measures to protect both themselves and their dogs.…”

Ocular leptospirosis: lack of awareness among ophthalmologists and challenges in diagnosis

“…Pigs and pig-hunting dogs were seropositive for Leptospira spp. Pig hunters are more at risk compared with the general Queensland population [30 ▪ ], An outbreak of leptospirosis in cattle workers was reported in the wet season, in Australia, 2021 [31] Japan reported the death of nine dogs within a month because of canine leptospirosis.…”