Vector competence of the African argasid tick Ornithodoros moubata for the Q fever agent Coxiella burnetii

Molecular detection of Coxiella burnetii in ticks infesting wild and domestic animals in the Eastern region of Punjab, Pakistan

Tick-borne pathogens are significant for human, veterinary, and wildlife health. Coxiella burnetii is an example that is widely distributed across various hosts and can cross species boundaries. In Pakistan, there is a scarcity of data regarding C. burnetii at the intersection of wildlife and livestock. Ticks were collected from ruminants and wildlife from the districts of Kasur, Pakpattan, and Okara in Pakistan. Five tick species totaling 571 ticks were collected, with the following distribution: 56.4% Hyalomma anatolicum, 22.4% Rhipicephalus microplus, 10.5% Hyalomma marginatum, 7.9% Rhipicephalus sanguineus, and 2.8% Rhipicephalus turanicus. Fifty tick pools were screened for C. burnetii to amplify a segment of the IS1111 using real-time PCR assays. Ticks collected from sheep and goats had a greater rate of positivity for C. burnetii (40% and 38%, respectively) compared to Indian long-eared hedgehogs with a prevalence of 2%. Coxiella burnetii was prominent in Rhipicephalus microplus (92.3%) and Hyalomma anatolicum (88.9%), followed by Rhipicephalus turanicus (66.6%), Rhipicephalus sanguineus (33.3%), and Hyalomma marginatum (25.0%). Ticks from Pakpattan district displayed the highest prevalence of C. burnetii (88.9%), whereas the lowest was observed in ticks from Kasur district (77.3%). There was no significant association between tick gender and C. burnetii infection. Female host animals were more likely to harbor ticks containing C. burnetii, with a prevalence rate of 81.8%. The research underscores the urgent need for comprehensive studies on C. burnetii in Pakistan, especially at the interface of wildlife and livestock. The high prevalence rates observed in certain tick species and geographic regions emphasize the importance of targeted public health interventions. Future research should focus on elucidating the transmission dynamics and implementing effective control measures to mitigate the impact of these pathogens on human, veterinary, and wildlife health in the region.

Reassessment of the genetic basis of natural rifampin resistance in the genus Rickettsia

Rickettsia, a genus of obligate intracellular bacteria, includes species that cause significant human diseases. This study challenges previous claims that the Leucine-973 residue in the RNA polymerase beta subunit is the primary determinant of rifampin resistance in Rickettsia. We investigated a previously untested Rickettsia species, R. lusitaniae, from the Transitional group and found it susceptible to rifampin, despite possessing the Leu-973 residue. Interestingly, we observed the conservation of this residue in several rifampin-susceptible species across most Rickettsia phylogenetic groups. Comparative genomics revealed potential alternative resistance mechanisms, including additional amino acid variants that could hinder rifampin binding and genes that could facilitate rifampin detoxification through efflux pumps. Importantly, the evolutionary history of Rickettsia genomes indicates that the emergence of natural rifampin resistance is phylogenetically constrained within the genus, originating from ancient genetic features shared among a unique set of closely related Rickettsia species. Phylogenetic patterns appear to be the most reliable predictors of natural rifampin resistance, which is confined to a distinct monophyletic subclade known as Massiliae. The distinctive features of the RNA polymerase beta subunit in certain untested Rickettsia species suggest that R. raoultii, R. amblyommatis, R. gravesii, and R. kotlanii may also be naturally rifampin-resistant species.

Impact of endosymbionts on tick physiology and fitness

Ticks transmit pathogens and harbour non-pathogenic, vertically transmitted intracellular bacteria termed endosymbionts. Almost all ticks studied to date contain 1 or more of Coxiella, Francisella, Rickettsia or Candidatus Midichloria mitochondrii endosymbionts, indicative of their importance to tick physiology. Genomic and experimental data suggest that endosymbionts promote tick development and reproductive success. Here, we review the limited information currently available on the potential roles endosymbionts play in enhancing tick metabolism and fitness. Future studies that expand on these findings are needed to better understand endosymbionts’ contributions to tick biology. This knowledge could potentially be applied to design novel strategies that target endosymbiont function to control the spread of ticks and pathogens they vector.

First Data on Ornithodoros moubata Aquaporins: Structural, Phylogenetic and Immunogenic Characterisation as Vaccine Targets

Ornithodoros moubata transmits African swine fever and human relapsing fever in Africa. The elimination of O. moubata populations from anthropic environments is expected to improve the prevention and control of these diseases. Tick vaccines have emerged as a sustainable method for tick control, and tick aquaporins (AQPs) are promising targets for tick vaccines due to their vital functions, immunogenicity and ease of access by neutralising host antibodies. This study aimed at the systematic identification of the AQPs expressed by O. moubata (OmAQPs) and their characterisation as vaccine targets. Therefore, AQP coding sequences were recovered from available transcriptomic datasets, followed by PCR amplification, cloning, sequence verification and the analysis of the AQP protein structure and epitope exposure. Seven OmAQPs were identified and characterised: six were aquaglyceroporins, and one was a water-specific aquaporin. All of these were expressed in the salivary glands and midgut and only three in the coxal glands. Epitope exposure analysis identified three extracellular domains in each AQP, which concentrate overlapping B and T cell epitopes, making them interesting vaccine targets. Based on these domain sequences, a set of ten antigenic peptides was designed, which showed adequate properties to be produced and tested in pilot vaccine trials.

Early Transcriptional Changes in the Midgut of Ornithodoros moubata after Feeding and Infection with Borrelia duttonii

Studies on tick-pathogen-host interactions are helping to identify candidates for vaccines against ticks and tick-borne diseases and to discover potent bioactive tick molecules. The tick midgut is the main tissue involved in blood feeding and, moreover, the first organ to have contact with pathogens ingested through the blood meal. As little is known about the molecular biology of feeding and tick defence mechanisms against microorganisms, but important for understanding vector-pathogen interactions, we explored the early transcriptional changes in the midgut of Ornithodoros moubata after feeding and in response to challenge with the relapsing-fever spirochete Borrelia duttonii using the Ion S5XL platform. Besides transcripts with metabolic function and immune-related transcripts we discovered numerous putative and uncharacterized protein sequences. Overall, our analyses support previous studies and provides a valuable reference database for further functional proteomic analysis of midgut proteins of O. moubata.