Haemophysalis Longicornis Capacity to Acquire and Transmit Babesia Microti

About This Grant

Project Summary/Abstract Babesiosis is caused by the intraerythrocytic Apicomplexan parasite Babesia microti (Bm) and is an emerging vector-borne infection transmitted by the Ixodes scapularis (Is) tick in the U.S. that carries significant morbidity and mortality in elderly and immunocompromised hosts. Babesiosis incidence continues to rise, correlating with climate change and seasonal expansion of tick activity in endemic regions like Long Island, NY. While antibiotic treatment is often effective, a subset of patients can present with severe parasitemia, progressive anemia and 1.6% will die of refractory infection. While babesiosis is well-known to be transmitted by Is ticks, it is hypothesized that the emerging and highly invasive Haemaphysalis longicornis (Hl; longhorned tick) in Long Island, NY may act as a competing vector. The invasion of Hl raises public health concerns as it can co-feed on shared vertebrate hosts (e.g., white-tailed deer), exchange tickborne pathogens with other tick species including Is, and reach very high population densities that can contribute to the increasing number of TBDs. However, the capacity for Hl to acquire and transmit Bm to humans remains unclear. This R21 proposal seeks to fill this gap by testing the central hypothesis that Hl is a competent vector for Bm uptake and transmission. In Aim 1, the study team employs a customized artificial membrane tick-feeding system to study Hl acquisition and transmission of Bm. The investigators will infect laboratory-reared Hl ticks with Bm and measure transstadial and transovarial transmission efficiencies, determine parasitic burdens in organ tissues (salivary glands, mid-gut, and ovary), and monitor tick survival. The investigators will also measure capacity for Hl to transmit Bm to a sterile blood reservoir within the AFS. As a control tick species, they will also infect laboratory-reared Is ticks that are known Bm reservoirs. The study team will corroborate findings by using field molecular epidemiology approaches to collect Hl and Is ticks at various geographical locations in Long Island throughout the year and to perform PCR analysis to determine the prevalence of Babesia spp. The study team already has a large library of >3000 ticks that they can immediately begin analyzing with continued active surveillance during the proposal. In Aim 2, the study team employs comparative genomics approaches to identify common Bm gene architecture in blood derived from field ticks and human acute babesiosis cases recruited at their medical center. In this Aim, they also propose parasite culture methods both in vivo and in vitro using human O+ blood to generate laboratory stocks of these circulating strains. The proposal has high potential to identify a competing vector for Bm transmission in an endemic region that will inform strategies for vector control and prevention. The results are expected to be of high impact to the fields of Tickborne diseases and Vector-borne infection biology and will provide important preliminary data to apply for multi-PI R01 applications in 2025/2026 to study tick ecology and vector-borne pathogen transmission, focusing on the polymicrobial nature of tickborne infections.