“Though head lice have been found in nature to carry the DNA of Bartonella quintana, Borrelia recurrentis, Acinetobacter baumannii and Yersinia pestis [5, 8, 9, 10, 11, 12, 13], and experimental infections have shown that these lice can also act as a vector of louse-borne diseases [14, 15], their epidemiological significance is still debated.”
Source: Nadia Amanzougaghene, Kosta Y. Mumcuoglu, Florence Fenollar, Shir Alfi, Gonca Yesilyurt, Didier Raoult, Oleg Mediannikov. PLoS ONE 11.
See full article: “High Ancient Genetic Diversity of Human Lice, Pediculus humanus, from Israel Reveals New Insights into the Origin of Clade B Lice.”