Abstract:
Background: Leptospirosis is a neglected zoonotic disease of worldwide public health importance. The disease
affects humans, domestic animals and wildlife. However, leptospirosis is challenging in its diagnosis in humans.
Culture technique, which is time consuming, is not recommended for clinical diagnosis. For these reasons,
serological and molecular techniques remain the test of choice. The major objective of this study was to explore
the genetic characteristic of Leptospira species which are prevalent among agro-pastoralists living in Katavi–Rukwa
Ecosystem, Tanzania.
Methods: A cross-sectional epidemiological study was carried out in the Katavi-Region South-west, Tanzania
between August, 2013 and November, 2014. A total of 267 participants were randomly recruited for the study.
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
Australis. Samples with MAT titers ≥ 1:160 were scored as positive, samples with MAT titers ranging from 1:20 to
1:80 were scored as exposed to Leptospira, and absence of agglutination titers was scored as negative. All MAT
positive samples, including the low titre samples were subjected to PCR using the respective 16S rRNA primers
for the pathogenic and non-pathogenic species.
Results: Out of 267 samples tested, 80 (29.9 %) were positive with MAT. The major circulating leptospiral serogroups
were Sejroe (15.7 %,), Icterohaemorrhagiae (8.9 %), Grippotyphosa (4.8 %), Hebdomadis (3.37 %), Australis (1.49 %) and
Ballum (1.19 %). By using PCR, 33 (15.7 %) out of 210 samples were pathogenic Leptospira while no saprophytic
Leptospira spp. was detected. Partial 16S rRNA gene sequences of Leptospira species which were obtained from
this study were submitted to GenBank and acquired accession numbers KP313246 and KP313247. Phylogenetic
analysis of the nucleotide sequences revealed that species obtained from Katavi-Rukwa ecosystem clustered in
the same group with several published pathogenic Leptospira specifically Leptospira interrogans and Leptospira kirschneri.
To the best of the authors’ knowledge , this is the first study from Tanzania to confirm pathogenic Leptospira in human
subjects using genomic typing technique.
Conclusion: These findings provide ultimate evidence of pathogenic Leptospira species circulating among agro-pastoralists
living in Katavi-Rukwa Ecosystem suggesting that active disease surveillance should be undertaken in order to
achieve greater protection of the agro-pastoral communities in Tanzania.
