Exploration towards seroprevalence and genetic diversity of Trypanosoma evansi in cattle of North Eastern state Mizoram

Abstract

Trypanosomosis, commonly known as surra is a chronic disease of cattle caused by the newlineflagellated hemoprotozoan parasite, Trypanosoma evansi. It is the most prevalent and pathogenic newlinetrypanosome throughout the tropical and subtropical areas of the world owing to its ability of newlinemechanical transmission by hematophagous tabanid flies as well as its ability to infect a wide newlinerange of domestic and wild animals. The chronic form of the disease in cattle result in severe newlineweakness, abortion, infertility, reduced milk yield, weight loss and reduced drought capabilities newlinethat can later lead to neuropathy and immune suppression coupled with anemia and eventually newlinedeath of the animal. India possesses second largest cattle population in the world having 193.46 newlinemillion and disease like surra tend to result in significant economic losses newlineMizoram is a North-Eastern state of India with a very less arable land and limited cattle newlinepopulation with which it cannot meet its own food requirements. Haemoprotozoan disease, surra newlinein subclinical form poses a challenge in terms of diagnosis and management to animal health newlinepractitioners and policy makers as well, eventually leading to financial loss to the livestock newlineholders. A systematic cross-sectional study was designed to assess the prevalence and climatic newlinerisk factors associated with Trypanosoma evansi infection among cattle, using a total of 480 newlineserum samples from eight districts of Mizoram during 2017-2019. Climatic risk factors like newlinediurnal temperature range, annual rainfall and relative humidity etc., which influence vector newlinepopulation were extracted and was correlated with T.evansi sero-prevalence. The apparent and newlinetrue sero-prevalence detected by card agglutination test for T.evansi (CATT/T.evansi) was newline37.08% (CI at 95%:32.88 - 41.49) and 37.1% (CI at 95%:32.9 - 41.51) whereas by recombinant newlineVSG based indirect ELISA was 41.88% (CI at 95%:37.5-46.3) and 40.31% (CI at 95%:35.44- newline45.32) respectively. Further, 16.66% of the samples tested positive giving a specific 400 bp newlineamplification with RoTat 1.2 VSG based diagnostic PCR. Phylogenetic tree was constructed by newlinetaking into account of the sequence of partial VSG gene of Mizoram samples and other available newlineGenbank sequences. The analysis revealed that all the Indian isolates clustered into a separate newlineclade indicating the evolutionary uniqueness among the isolates and evidently each species sub newlineclustered into different clades. Climate parameters which influence vector population were newlineextracted from their respective database and were correlated with seroprevalence data. Linear newlinediscriminant analysis revealed that air temperature, relative humidity, diurnal temperature range, newline newline2 newline newlineleaf area index and soil moisture as significant risk factors discriminating seropositive and newlineseronegative data sets classified by indirect-ELISA. The phylogenetic analysis and genetic newlinedistance calculation revealed that there is a minimal difference among the T.evansi isolates from newlinedifferent hosts. The analysis also revealed the genetic closeness of isolates of the present study newlinewith other isolates published from different parts of the country based on the four marker genes. newlineThis study is a first report of prevalence of surra in cattle of Mizoram and the situation seeks newlinedeployment of intervention strategies in order to assess the endemicity of the disease and thereby newlinepreventing the economic losses. newline