Comparison of the proliferation and excretion of Bartonella quintana between body and head lice following oral challenge

Abstract

Human body and head lice are highly related hematophagous ectoparasites but only the body louse has been shown to transmit Bartonella quintana, the causative agent of trench fever. The mechanisms by which body lice became a vector for B. quintana, however, are poorly understood. Following the oral challenge, green fluorescence protein-expressing B. quintana proliferated over 9 days post-challenge with the number of bacteria being significantly higher in whole body versus head lice. The numbers of B. quintana detected in feces from infected lice, however, were approximately the same in both lice. Nevertheless, the viability of B. quintana, was significantly higher in body louse feces. Comparison of immune responses in alimentary tract tissues revealed that basal transcription levels of peptidoglycan recognition protein and defensins were lower in body lice and the transcription of defensin 1 was up-regulated by oral challenge with wild-type B. quintana in head but not in body lice. In addition, the level of cytotoxic reactive oxygen species generated by epithelial cells was significantly lower in body lice. Although speculative at this time, the reduced immune response is consistent with the higher vector competence seen in body versus head lice in terms of B. quintana infection.

Where Are We With Human Lice? A Review of the Current State of Knowledge

“…For example, in body lice, the B. quintana proliferation rate in the gut was significantly higher (2.0-12.1-fold) over time when compared with head lice until 12 days post-challenge. The viability index of B. quintana in the feces over the entire 11 days post-challenge was 6.4-10.6-fold higher in body lice compared to head lice (Kim et al, 2017). The reduction of the immune response in body lice may be partly the consequence for their increased competence as a vector, compared to head lice (Kim et al, 2011(Kim et al, , 2012(Kim et al, , 2017Previte et al, 2014), which develop a more effective immune response to restrict bacterial replication.…”

“…Recently, several studies have performed comparative analyses in the immune responses following the bacterial challenge using in vitro-rearing system and have shown that body lice relative to head lice show a significant reduction in immune responses, particularly at the onset of the immune challenge (Kim et al, 2011(Kim et al, , 2012(Kim et al, , 2017Previte et al, 2014). In one study in particular, Kim et al (2017) demonstrated that, as in the case of body lice, head lice can withstand a persistent charge of B. quintana infection for several days following the acquisition in a bloodmeal and spread in their feces viable bacteria. However, the rates of proliferation in the gut and numbers of viable B. quintana in the feces were significantly lower in head lice compared to body lice (Kim et al, 2017).…”

“…In one study in particular, Kim et al (2017) demonstrated that, as in the case of body lice, head lice can withstand a persistent charge of B. quintana infection for several days following the acquisition in a bloodmeal and spread in their feces viable bacteria. However, the rates of proliferation in the gut and numbers of viable B. quintana in the feces were significantly lower in head lice compared to body lice (Kim et al, 2017). For example, in body lice, the B. quintana proliferation rate in the gut was significantly higher (2.0-12.1-fold) over time when compared with head lice until 12 days post-challenge.…”

“…Indeed, following B. quintana oral challenge, the transcriptional analysis of the immune response of the alimentary tract of body lice, revealed a reduction in the level of transcription of the main immune genes, including peptidoglycan recognition protein, defensins, and defensin 1, when compared to head lice. How this transcription repression occurs in body lice remains currently unknown (Kim et al, 2012(Kim et al, , 2017. Kim et al (2017) suggested that this regulation may be a consequence of regulatory changes in the epigenetic pathways and in the post-transcriptional miRNA-mediated factors (Kim et al, 2017).…”

“…How this transcription repression occurs in body lice remains currently unknown (Kim et al, 2012(Kim et al, , 2017. Kim et al (2017) suggested that this regulation may be a consequence of regulatory changes in the epigenetic pathways and in the post-transcriptional miRNA-mediated factors (Kim et al, 2017). The level of reactive oxygen species, which is thought to be one of the key mediators of antimicrobial innate immunity defense in the insect gut (Molina-Cruz et al, 2008), was also reduced in body lice compared to head lice (Kim et al, 2017).…”