Guernier, Vanina, Richard, Vaea, Nhan, Tuxuan, Rouault, Eline, Tessier, Anita, and Musso, Didier (2017) Leptospira diversity in animals and humans in Tahiti, French Polynesia. PLoS Neglected Tropical Diseases, 11 (6). e0005676. pp. 1-16.

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Abstract

Background: Leptospirosis is a highly endemic bacterial zoonosis in French Polynesia (FP). Nevertheless, data on the epidemiology of leptospirosis in FP are scarce. We conducted molecular studies on Leptospira isolated from humans and the potential main animal reservoirs in order to identify the most likely sources for human infection.

Methodology/Principal findings: Wild rats (n = 113), farm pigs (n = 181) and domestic dogs (n = 4) were screened for Leptospira infection in Tahiti, the most populated island in FP. Positive samples were genotyped and compared to Leptospira isolated from human cases throughout FP (n = 51), using secY, 16S and LipL32 sequencing, and MLST analysis. Leptospira DNA was detected in 20.4% of rats and 26.5% of pigs. We identified two Leptospira species and three sequence types (STs) in animals and humans: Leptospira interrogans ST140 in pigs only and L. interrogans ST17 and Leptospira borgpetersenii ST149 in humans and rats. Overall, L. interrogans was the dominant species and grouped into four clades: one clade including a human case only, two clades including human cases and dogs, and one clade including human cases and rats. All except one pig sample showed a unique L. interrogans (secY) genotype distinct from those isolated from humans, rats and dogs. Moreover, LipL32 sequencing allowed the detection of an additional Leptospira genotype in pigs, clearly distinct from the previous ones.

Conclusions/Significance: Our data confirm rats as a major potential source for human leptospirosis in FP. By contrast to what was expected, farm pigs did not seem to be a major reservoir for the Leptospira genotypes identified in human patients. Thus, further investigations will be required to determine their significance in leptospirosis transmission in FP.

Author summary: Leptospirosis, a zoonosis caused by Leptospira spp. bacteria, is an important but neglected disease in the Pacific region. The bacteria can lead to human infections, either through direct contact with infected animals or through water and soil contaminated with urine. Although animals play a key role in the transmission of the disease, the relative importance of animal reservoirs for human leptospirosis infections in the Pacific have not been investigated. In French Polynesia, the animal species acting as sources for human infection are unknown. In our study, we isolated leptospires from rats, farm pigs and pet dogs from Tahiti, the most populated island of French Polynesia, and compared them to those isolated from human leptospirosis cases. The types of leptospires identified in human leptospirosis cases were also detected in rats and dogs, whereas leptospires found in pigs were genetically different. These results indicate that rats are a major potential source for human leptospirosis in Tahiti. Further investigations will be required to clarify the relative contribution of dogs and pigs to human leptospirosis in French Polynesia, to properly design or adapt interventions to reduce the burden of human leptospirosis.

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