Hard ticks (Ixodidae) play a critical role in transmitting various tick-borne diseases (TBDs), posing significant global threats to human and animal health. Climatic factors influence the abundance, diversity, and vectorial capacity of tick vectors. It is imperative to have a comprehensive understanding of hard ticks, pathogens, eco-epidemiology, and the impact of climatic changes on the transmission dynamics of TBDs. The distribution and life cycle patterns of hard ticks are influenced by diverse ecological factors that, in turn, can be impacted by changes in climate, leading to the expansion of the tick vector’s range and geographical distribution. Vector competence, a pivotal aspect of vectorial capacity, involves the tick’s ability to acquire, maintain, and transmit pathogens. Hard ticks, by efficiently feeding on diverse hosts and manipulating their immunity through their saliva, emerge as competent vectors for various pathogens, such as viruses, parasites and bacteria. This ability significantly influences the success of pathogen transmission. Further exploration of genetic diversity, population structure, and hybrid tick vectors is crucial, as they play a substantial role in influencing vector competence and complicating the dynamics of TBDs. This comprehensive review deals with important TBDs in India and delves into a profound understanding of hard ticks as vectors, their biology, and the factors influencing their vector competence. Given that TBDs continue to pose a substantial threat to global health, the review emphasizes the urgency of investigating tick control strategies and advancing vaccine development. Special attention is given to the pivotal role of population genetics in comprehending the genetic diversity of tick populations and providing essential insights into their adaptability to environmental changes.

Hard tick exoskeletons, composed primarily of chitin, pose a significant challenge for researchers attempting to extract genetic material. This study presents a simple modified, alternative method for extracting DNA from ethanol-preserved hard ticks. The extracted DNA was further used for PCR amplification of phylogenetic markers for population genetics studies. The study also improvises the DNA extraction methods from commercial kits. We have used four DNA extraction methods: Modified Simple Alkaline Lysis, and other commercial kit-based methods (Kit X, Kit Y & Kit Z). The modified method for DNA extraction yielded comparable results in terms of concentration, and purity from all the life stages (adult, nymph, and larvae). The extracted DNA from each method was quantified and subjected to PCR amplification of molecular markers, ITS-1 and ITS-2. The nucleotide sequences from both markers were characterized for the first time and used for phylogenetic analysis of Amblyomma integrum, which is a potential vector for Kyasanur Forest Disease Virus (KFDV), causing monkey fever disease in India. These results demonstrate a cost-effective approach for isolating genomic DNA suitable for PCR amplification and subsequent nucleotide sequencing. Importantly, this simple method offers an option for population genetics study in resource-limited settings, facilitating field research with minimal equipment requirements. Additionally, the study showed tick homogenization can significantly improve DNA yield from commercial kits.

The long Pentraxin 3 (PTX3), a soluble pattern recognition molecule, plays a critical role in inflammation, tissue repair and wound healing. Here, we show that PTX3 regulates disease pathogenesis in cutaneous leishmaniasis (CL). PTX3 expression is increased in active skin lesions in patients and mice during CL, with higher levels being expressed in individuals with severe disease. PTX3 deficient (PTX3 ^-/- ) mice were highly resistant to L. major infection and the enhanced resistance was associated with increased IL-17 response. Neutralization of IL-17A abolished this enhanced resistance while treatment with recombinant PTX3 resulted in reduced IL-17A response and increased susceptibility to L. major infection. Naïve CD4 ⁺ T cells from PTX3 ^-/- mice displayed increased differentiation into Th17 cells, which was reversed in the presence of recombinant PTX3. The enhanced Th17 response observed in PTX3 ^-/- cells was associated with increased Leishmania specific IL-6 production from dendritic cells along with enhanced expression of Th17-specific transcription factors including RORγt, AhR and STAT3. Addition of recombinant PTX3 significantly inhibited the expression of Th17-specific transcription factors and dramatically reduced the frequency of Th17 cells in Th17-polarizing cultures of PTX3 ^-/- CD4 ⁺ T cells. Collectively, our results show that PTX3 contributes to the pathogenesis of CL by suppressing Th17 differentiation and IL-17A production. Author Summary: Cutaneous leishmaniasis (CL) is caused by several species of Leishmania . Currently, there is no approved vaccine against human CL because of the poor understanding of the mechanisms that regulate disease pathogenesis and correlates of protective immunity. Because the long pentraxin 3 (PTX3, a soluble pattern recognition molecule that forms an integral part of the host innate immunity), regulates inflammation and tissue repair, which are critical physiological events associated with resolution of skin lesions during CL, we investigated its role in disease pathogenesis. Here, we show that PTX3 levels were elevated in skin-lesions in patients and mice during CL. Using a loss of function approach, we showed that PTX3 contributes to pathogenesis, and this was associated with increased IL-17A responses. Neutralization and recombinant cytokine treatment studies showed that the increased resistance of PTX3 deficient mice to L. major is due to enhanced Th17 response in these mice. We further show that PTX3 negatively regulates IL-6 production by dendritic cells and the expression of IL-17A-specific transcription factors (including RORγT, STAT3, IRF4, BATF and AhR) in CD4 ⁺ T cells. Collectively, these findings show that PTX3 is a negative regulator of Th17 response and protective immunity during L. major infection.

Hard ticks are important vectors for several human and zoonotic pathogens, transmitting diseases such as Crimean–Congo hemorrhagic fever, Lyme disease, Kyasanur forest disease, Powassan virus disease, Tick-borne encephalitis, Rickettsiosis, and Anaplasmosis. Morphological identification of ticks relies on taxonomic keys but is often challenging due to damaged, engorged, or immature specimens and requires expertise. Molecular taxonomy can be a supplement to species identification and usually requires nucleotide sequencing of the genetic markers. PCR-RFLP is an important tool for tick identification and can be supplemented to the classical taxonomy. The current study focused on the morphological identification of important hard tick vectors from India, their phylogenetic positioning, and developing a PCR-RFLP based diagnostic tool for easy identification of hard tick vectors. The primer sets were designed to amplify the ITS-2 region from important tick vectors causing human and zoonotic diseases in India. These ticks were morphologically identified with taxonomical keys, and the extracted genomic DNA were used for ITS-2 based PCR amplification. The nucleotide sequences from each vector were used for their phylogenetic positioning. We obtained variable sizes of ITS-2 amplicons from each species and utilized the sequence for RFLP assays design. We have successfully shown PCR-RFLP based assays with two different restriction enzymes (Hae III & Rsa I) with specific restriction sites on the amplified regions. The PCR-RFLP tool showed different DNA fragment patterns on the agarose gel, specific for each hard tick vector. This study presents the phylogenetic positioning of Indian tick vectors and demonstrates the development and applicability of a molecular tool for their identification.