Molecular epidemiology of Leptospira species among Agropastoral communities living in Katavi-Rukwa ecosystem, Tanzania

Abstract

Leptospirosis is an emerging zoonotic infectious disease which affects humans and animals worldwide as it causes febrile illness in humans. The disease has been reported in a number of human-livestock-wildlife interfaces of Northern and Eastern Tanzania. Very little is known of many zoonotic disease conditions in the research naive areas of Western and Southern Tanzania. This study aimed at detecting the prevalence of Leptospira species among agro-pastoralists at the human-animal interface areas of Katavi-Rukwa ecosystem. Microscopic agglutination test (MAT) was used to detect antibody against six Leptospira antigens including local serogroups Icterohaemorrhagiae, Ballum, Grippotyphosa, Sejroe and reference serogroups Hebdomadis and Lora. Samples with MAT titers ≥ 1:160 were scored as positive while MAT titers between 1:20 and 1:80 were scored as exposed to Leptospira and absence of agglutination titers was scored as negative. Of the 267 samples tested 80 (30%) were positive, 57 (21.3%) were negative and 130 (4 8.6%) were exposed to leptospiral infection. Infection rate in adults was higher 51 (63.75%) compared to children 29 (36.25%), P<0.05. Circulating serogroups were; Hardjo (15.7%); Icterohaemorrhagiae (8.98%), Grippotyphosa (4.87%), Hebdomadis (3.37%), Australis (1.49%) and Ballum (1.12%). Samples that were positive or scored as exposed by MAT were further tested using polymerase chain reaction (PCR) targeting 16S ribosomal gene. Pathogenic Leptospira was detected in 33 (15.5%) out of 212 while no saprophytic Leptospira species was detected. Sequencing alignment based on 16S ribosomal gene suggested Leptospira interrogans, kirshinei and uncultured Leptospira clone species as circulating species among agro-pastoralists of Katavi-Rukwa ecosystem. These findings suggest that in the Katavi leptospirosis in man is likely acquired from environment, probably by indirect contact with contaminated water or soil. This study also revealed that serological diagnosis of leptospirosis should be considered in the diagnosis on non- malarial febrile illness in agro-pastoralists living in Katavi-Rukwa ecosystem, Tanzania.