A Comparative Study of Body Lice and Bed Bugs Reveals Factors Potentially Involved in Differential Vector Competence for the Relapsing Fever Spirochete Borrelia recurrentis

Cimicids of Medical and Veterinary Importance

Members of the Cimicidae family are significant pests for mammals and birds, and they have attracted medical and veterinary interest. A number of recent studies have investigated bed bugs, due to their dramatic resurgence all over the world. Indeed, bed bugs are of significant public health and socioeconomic importance since they lead to financial burdens and dermatological complications and may have mental and psychological consequences. It is important to note that certain cimicids with a preference for specific hosts (birds and bats) use humans as an alternative host, and some cimicids have been reported to willingly feed on human blood. In addition, members of the Cimicidae family can lead to economic burdens and certain species are the vectors for pathogens responsible for diseases. Therefore, in this review, we aim to provide an update on the species within the Cimicidae family that have varying medical and veterinary impacts, including their distribution and their associated microorganisms. Various microbes have been documented in bed bugs and certain important pathogens have been experimentally documented to be passively transmitted by bed bugs, although no conclusive evidence has yet associated them with epidemiological outbreaks. Additionally, among the studied cimicids (bat bugs, chicken bugs, and swallow bugs), only the American swallow bug has been considered to be a vector of several arboviruses, although there is no proven evidence of transmission to humans or animals. Further studies are needed to elucidate the reason that certain species in the Cimicidae family cannot be biologically involved in transmission to humans or animals. Additional investigations are also required to better understand the roles of Cimicidae family members in the transmission of human pathogens in the field.

Detection of Arthropod-Borne Bacteria and Assessment of MALDI-TOF MS for the Identification of Field-Collected Immature Bed Bugs from Mauritania

Human infestations by bed bugs have upsurged globally in recent decades, including in African countries, where recent reports pointed out an increase in infestation. Sympatric dwelling has been described for two species of bed bug parasitizing humans: Cimex hemipterus (the tropical bed bug) and C. lectularius. Identification of these two species is based on morphological characteristics, and gene sequencing, and may also rely on Matrix-Assisted Laser Desorption Ionization Time-Of-Flight Mass Spectrometry (MALDI-TOF MS). The present work aimed to assess whether MALDI-TOF MS was applicable for species level identification of immature stages of Cimex. Arthropods were collected in domestic settings in Nouakchott, Mauritania. Identification used morphological keys and MALDI-TOF MS identification was assessed for immature stages. Quantitative PCR and sequencing assays were used to detect arthropod-associated bacteria in each specimen. A total of 92 arthropods were collected, all morphologically identified as C. hemipterus (32 males, 14 females and 45 immature stages). A total of 35/45 specimens produced good quality MALDI-TOF MS spectra. Analysis allowed species level identification of all immature C. hemipterus after their spectra were entered into our in-house MALDI-TOF MS arthropod spectra database. Molecular screening allowed detection of Wolbachia DNA in each specimen. These results suggested that MALDI-TOF MS is a reliable tool for species level identification of Cimex specimens, including immature specimens. Future studies should assess this approach on larger panels of immature specimens for different Cimex species and focus on the precise staging of their different immature developmental stages.

Examination of vertical transmission of Bartonella quintana in body lice following multiple infectious blood meals

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.