@article {96451, title = {A Comparative Study of Body Lice and Bed Bugs Reveals Factors Potentially Involved in Differential Vector Competence for the Relapsing Fever Spirochete Borrelia recurrentis}, journal = {Infection and Immunity}, volume = {90}, year = {2022}, month = {May-19-2022}, pages = {13 pp}, abstract = {

Borrelia recurrentis is the causative agent of louse-borne relapsing fever and the only Borrelia species transmitted by an insect rather than a tick vector. While bed bugs (Cimex lectularius L.) are not established vectors of any human pathogens, a recent study reported that they may be competent vectors of B. recurrentis. However, many aspects of infection and transmission remain unclear in this possible secondary vector. Here, we carried out several quantitative laboratory studies to gain a better understanding of the host suitability of bed bugs relative to the established body louse vector as well as the factors that may affect the ability of bed bugs to transmit the pathogen. We fed bed bugs B. recurrentis and estimated the level and duration of infection in the hemolymph using live imaging. We performed quantitative PCR (qPCR) to examine whole-body spirochete levels and the occurrence of vertical transmission to progeny. We also developed an assay to compare the amounts of force required to release infectious hemolymph from recently engorged bed bugs and body lice. Finally, we analyzed humoral antibacterial activity in the hemolymph, hemolymph pH, and hemocyte activity in both insect species. Our results confirm that within 24\ h of ingestion, B. recurrentis can penetrate the midgut epithelium of bed bugs and enter the hemolymph, overcoming a major host barrier, as in body lice. Once in the hemolymph, spirochetes remain visible for at least 4 days. Moreover, we show that bed bugs are more physically susceptible to crushing than body lice, suggesting that crushing is a feasible route for the natural dissemination of B. recurrentis from the hemolymph of bed bugs, as for body lice. Nonetheless, our data also indicate that bed bugs are suboptimal hosts for B. recurrentis, as the bacterium does not appear to proliferate to high levels or stably colonize the hemolymph and exhibits pleomorphism in this environment. In particular, our data suggest that hemolymph pH and unique cellular immune responses, rather than humoral effectors, may be involved in limiting spirochete survival in bed bugs. Notably, we document the formation of extracellular DNA traps by bed bug hemocytes for the first time. For these reasons, while bed bugs may be capable of limited transmission given their ecology, vector competence is probably minimal relative to body lice. Additional mechanistic studies of human pathogen infection of bed bugs may provide much-needed insight into the biological factors that restrict their ability to act as vectors and may reveal novel mechanisms of immunity.

}, keywords = {Arthropod Vectors, Bed bug, Borrelia, Borrelia recurrentis, Cimex, competence, Hemolymph, host, lice, transmission, vector, vector-borne disease}, issn = {0019-9567, 1098-5522}, doi = {10.1128/iai.00683-21}, url = {https://journals.asm.org/doi/10.1128/iai.00683-21}, author = {Rashaun Potts and Jamie L. Scholl and Lee A. Baugh and Jose E. Pietri} } @article {96370, title = {Examination of vertical transmission of Bartonella quintana in body lice following multiple infectious blood meals}, journal = {Pathogens and Disease}, volume = {80}, year = {2022}, month = {Jan-01-2022}, pages = {5 pp}, abstract = {

Bartonella quintana is a re-emerging louse-borne pathogen. Horizontal transmission from the body louse vector (Pediculus humanus humanus) to a human host occurs through contact with infectious louse feces containing a high concentration of the bacteria. However, questions have remained about whether vertical transmission from infected vectors to their progeny, which could significantly influence the dynamics of transmission to humans, occurs in body lice. To address this subject, we performed a series of controlled laboratory experiments that examined the presence of B. quintana on the surface of and within eggs produced by female body lice that were provisioned multiple infectious blood meals to recapitulate the natural pathogen acquisition process. Our results demonstrate that B. quintana DNA can be detected from the surface of eggs by qPCR due to vertical transfer of infectious feces to the egg sheath during or after oviposition. However, viable B. quintana could not be cultured from the hemolymph of adult female lice or from within eggs that were surface sterilized, indicating a lack of true transovarial transmission. Based on this evidence, vertical transfer of B. quintana from infected adult lice to their eggs probably has a limited impact on the dynamics of transmission to humans.

}, keywords = {bartonella quintana, lice, louse, transmission, vector, vertical}, issn = {2049-632X}, doi = {10.1093/femspd/ftac028}, url = {https://academic.oup.com/femspd/article/80/1/ftac028/6634238}, author = {Lauren Kress and Rashaun Potts and Jose E. Pietri} } @article {95442, title = {Microbiome Differences between Human Head and Body Lice Ecotypes Revealed by 16S rRNA Gene Amplicon Sequencing}, journal = {Journal of Parasitology}, volume = {106}, year = {2020}, month = {Jan-020}, pages = {14-24}, abstract = {

Human head lice and body lice (Pediculus humanus) are neglected ectoparasites. Head lice continue to be prevalent in children worldwide, and insecticide resistance in these insects has complicated their treatment. Meanwhile, body lice, which are most common in the developing world, are resurging among marginalized populations in developed nations. Today, the microbiome is being increasingly recognized as a key mediator of insect physiology. However, the microbial communities that inhabit human lice have remained unknown beyond only a few species of bacteria. Knowledge of the microbiomes of head and body lice could improve our understanding of the observed physiological differences between the 2 ecotypes and potentially inform the development of novel interventions against lice infestations and louse-borne infectious diseases. Toward these goals, here we performed 16S rRNA gene amplicon sequencing to characterize the microbiomes of both head and body lice and identify patterns of interest among these communities. Our data reveal that head and body lice harbor limited but distinct communities of bacteria that include known intracellular endosymbionts (\“Candidatus Riesia pediculicola\”), extracellular bacteria that may be horizontally acquired from the host environment, and a number of taxa of known or potential public health significance. Notably, in body lice, the relative abundance of vertically transmitted endosymbionts is lower than in head lice, which is a significant driver of greater alpha diversity. Further, several differentially abundant non-endosymbiont taxa and differences in beta diversity were observed between head lice and body lice. These findings support the hypothesis that microbiome differences could contribute to the divergence between human louse ecotypes and underscore the need for future studies to better comprehend the acquisition and physiological roles of human lice microbiomes

}, keywords = {16S rRNA, Amplicon, bacteria, body louse, Gene, Head louse, Microbiome, Pathogen, sequencing}, issn = {0022-3395}, doi = {10.1645/19-132}, url = {https://bioone.org/journals/journal-of-parasitology/volume-106/issue-1/19-132/Microbiome-Differences-between-Human-Head-and-Body-Lice-Ecotypes-Revealed/10.1645/19-132.short}, author = {Diing D. M. Agany and Rashaun Potts and Jose L. Gonzalez-Hernandez and Etienne Z. Gnimpieba and Jose E. Pietri} }