Molecular screening for Rickettsia, Anaplasma, and Coxiella in head lice (Pediculus humanus capitis) collected from primary school girls in Fars Province, Iran (2024)

Lice are obligate ectoparasites divided into two main families: Pediculidae and Phthiridae. Body lice are known vectors of bacterial pathogens like Rickettsia, which cause diseases such as epidemic typhus and trench fever. Although head lice are genetically similar to body lice, they have long been considered a nuisance rather than a medical threat. This is particularly concerning for primary school girls, a vulnerable group with high infestation rates. This study aimed to detect deoxyribonucleic acid (DNA) from Coxiella, Rickettsia, and Anaplasma in head lice collected from female elementary school students in Fars, Iran, in 2024. Head lice were collected from the scalp of school-aged girls and pooled for molecular analysis, with each pool containing 10 lice. DNA was extracted, and specific primers were designed for the detection of each pathogen using polymerase chain reaction (PCR) assays. Coxiella DNA was detected in pooled head lice samples collected from six of the seven surveyed cities, including Marvdasht, Kazerun, Sepidan, Shiraz, Firouzabad, and Kavar. Anaplasma DNA was detected only in pooled samples from Firouzabad. Rickettsia DNA was not detected in any of the examined samples. The absence of Rickettsia DNA in all surveyed locations may reflect a low prevalence or absence of detectable Rickettsia DNA in the sampled head lice populations. It should be noted that the PCR assay used in this study detects Coxiella spp. at the genus level and does not distinguish Coxiella burnetii from Coxiella-like endosymbionts (CLEs) commonly found in arthropods. Therefore, the detection of Coxiella DNA should be interpreted as molecular evidence of bacterial genetic material rather than confirmation of pathogenicity or public health risk.