The prevalence of Leptospira among invasive small mammals on Puerto Rican cattle farms

Authors: BENAVIDEZ, KATHRYN - Texas State University; GUERRA, TRINA - Texas State University; TORRES, MADISON - Texas State University; RODRIGUEZ, DAVID - Texas State University; VEECH, JOSEPH - Texas State University; HAHN, DITTMAR - Texas State University; Miller, Robert; SOLTERO, FRED - Animal And Plant Health Inspection Service (APHIS); PEREZ RAMIREZ, ALEJANDRO - Puerto Rico Department Of Agriculture; Perez De Leon, Adalberto - Beto; CASTRO-ARELLANO, IVAN - Texas State University

Submitted to: PLOS Neglected Tropical Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2019
Publication Date: 5/20/2019
Citation: Benavidez, K.M., Guerra, T., Torres, M., Rodriguez, D., Veech, J., Hahn, D., Miller, R., Soltero, F., Perez Ramirez, A., Perez De Leon, A.A., Castro-Arellano, I. 2019. The prevalence of Leptospira among invasive small mammals on Puerto Rican cattle farms. PLOS Neglected Tropical Diseases. 13(5):e0007236. https://doi.org/10.1371/journal.pntd.0007236.
DOI: https://doi.org/10.1371/journal.pntd.0007236

Interpretive Summary: Leptospirosis is an emerging infectious disease caused by bacteria of the genus Leptospira, and it is considered to be the most widespread worldwide among the type of diseases that can be transmitted from animals to humans. Efforts to prevent the dissemination of Leptospira requires an understanding of the animals that can harbor and disperse the bacteria in nature. In an example of the importance of disease ecology studies, our project on integrated tick management research in Puerto Rico to mitigate the burden of bovine babesiosis required the sampling of animals other than livestock to assess their involvement as hosts of the cattle fever tick disease vector. This effort enabled us to apply molecular methods to analyze kidney samples from 124 House mice, 94 Black rats, 5 Norway rats, and 89 small Indian mongooses collected at five cattle farms under study. The kidneys of mice, Black and Norway rats, and mongooses were found to be infected with Leptospira. The bacterial species identified were L. borgpetersenii and L. interrogans. A significant association between the presence of infected mice, rats, or mongooses and human activity was observed in two farms. In these farms, infected mice, rats, or mongooses tended to be found closer to human dwellings, milking barns, and ponds than their uninfected counterparts. These results suggest that additional research on the ecology of leptospirosis in rural areas of Puerto Rico is needed to enhance disease prevention among human and livestock populations.

Technical Abstract: Leptospirosis, an emerging infectious disease caused by bacteria of the genus Leptospira, is thought to be the most widespread zoonotic disease in the world. A first step in preventing the spread of Leptospira is delineating the animal reservoirs that maintain and disperse the bacteria. Quantitative PCR (qPCR) methods targeting the LipL32 gene were used to analyze kidney samples from 124 House mice (Mus musculus), 94 Black rats (Rattus rattus), 5 Norway rats (R. norvegicus), and 89 small Indian mongooses (Herpestes auropunctatus) from five cattle farms in Puerto Rico. Renal carriage of Leptospira was found in 38% of the sampled individuals, with 59% of the sampled mice, 34% of Black rats, 20% of Norway rats, and 13% of the mongooses. A heterogeneous distribution of prevalence was also found among sites, with the highest prevalence of Leptospira-positive samples at 52% and the lowest at 30%. Comparative sequence analysis of the LipL32 gene from positive samples revealed the presence of two species of Leptospira, L. borgpetersenii and L. interrogans in mice, detected in similar percentages in samples from four farms, while samples from the fifth farm almost exclusively harbored L. interrogans. In rats, both Leptospira species were found, while mongooses only harbored L. interrogans. Numbers tested for both animals, however, were too small (n=7 each) to relate prevalence of Leptospira species to location. Significant associations of Leptospira prevalence with anthropogenic landscape features were observed at farms in Naguabo and Sabana Grande, where infected individuals were closer to human dwellings, milking barns, and ponds than were uninfected individuals. These results show that rural areas of Puerto Rico are in need of management and longitudinal surveillance of Leptospira in order to prevent continued infection of focal susceptible species (i.e. humans and cattle).