12S rRNA based phylogeny and genetic diversity of Haemaphysalis spinigera, the primary vector for Kyasanur forest disease in India

Kyasanur Forest Disease (KFD), also known as Monkey Fever, is an important tick-borne viral infection in India. It is mainly transmitted by the hard tick vector, Haemaphysalis spinigera. This re-emerging viral disease in humans has a mortality rate of 2-10% and was first reported in the Shimoga district of Karnataka in 1957. In recent years, KFD has been reported from various parts of the country, indicating possible geographical expansion and wider distribution of the tick vector. Assessing the distinct populations of H. spinigera and their local adaptations is important. However, the genetic structure of this vector population remains undocumented due to the lack of well-characterized genetic markers. Although the distribution of H. spinigera has been described, information on its genetic diversity and population structure is still limited. In this study, we characterized and validated a mitochondrial marker, 12S rRNA for assessing the genetic diversity of H. spinigera in Eastern and Western Ghats of India. Analysis of ninety individual ticks revealed a genetically diverse population comprising three haplotypes, which formed three distinct clades. These clades included haplotypes from nine geographical populations. Understanding the genetic structure of tick vectors is crucial for studying the transmission dynamics of tick-borne diseases. Our findings suggest that 12S rRNA is a suitable genetic marker for studying intraspecific variation in H. spinigera. To the best of our knowledge, this is the first to report the population structure of H. spinigera, highlighting its genetic diversity in the Western and Eastern Ghats of India.