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The Asian longhorned tick (Haemaphysalis longicornis) was first reported in the United States in 2017 and has since been detected in at least 17 states. This tick infests cattle and can produce large populations quickly due to its parthenogenetic nature, leading to significant livestock mortalities and economic losses. While H. longicornishas not been detected in Texas, species distribution models have identified southern Texas as a possible hospitable region for this tick. Southern Texas is currently home to the southern cattle tick (Rhipicephalus microplus), which can transmit the causative agent of cattle fever (Babesia bovis). With the potential for H. longicornisand B. bovisto overlap in southern Texas and their potential to negatively impact the national and global livestock industry, it is imperative to identify the role H. longicornismay play in the cattle fever disease system. A controlled acquisition and transmission experiment tested whether H. longicornisis a vector for B. bovis, with the R. microplus-B. bovissystem used as a positive control. Transstadial (nymphs to adults) and transovarial (adults to larvae) transmission and subsequent transstadial maintenance (nymphs and adults) routes were tested in this study. Acquisition-fed, splenectomized animals were used to increase the probability of tick infection. Acquisition nymphs were macerated whole and acquisition adults were dissected to remove midguts and ovaries at five time points (4, 6, 8, 10, and 12 days post-repletion), with 40 ticks processed per time point and life stage. The greatest percentage of nymphs with detectable B. bovisDNA occurred six days post-repletion (20.0%). For adults, the percentage of positive midguts and ovaries increased as days post-repletion progressed, with day 12 having the highest percentage of positive samples (67.5% and 60.0%, respectively). When egg batches were tested in triplicate, all H. longicornisegg batches were negative for B. bovis, while all R. microplusegg batches were positive for B. bovis. During the transmission phase, the subsequent life stages for transstadial (adults) and transovarial transmission/transstadial maintenance (larvae, nymphs, and adults) were fed on naïve, splenectomized calves. All life stages of H. longicornisticks tested during transmission were negative for B. bovis. Furthermore, the transmission fed animals were also negative for B. bovisand did not show signs of bovine babesiosis during the 45-day post tick transmission period. Given the lack of successful transstadial or transovarial transmission, it is unlikely that H. longicornisis a vector for B. bovis. |
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