Detection of bacterial pathogens including potential new species in human head lice from Mali

Abstract

In poor African countries, where no medical and biological facilities are available, the identification of potential emerging pathogens of concern at an early stage is challenging. Head lice, Pediculus humanus capitis, have a short life, feed only on human blood and do not transmit pathogens to their progeny. They are, therefore, a perfect tool for the xenodiagnosis of current or recent human infection. This study assessed the occurrence of bacterial pathogens from head lice collected in two rural villages from Mali, where a high frequency of head lice infestation had previously been reported, using molecular methods. Results show that all 600 head lice, collected from 117 individuals, belonged to clade E, specific to West Africa. Bartonella quintana, the causative agent of trench fever, was identified in three of the 600 (0.5%) head lice studied. Our study also shows, for the first time, the presence of the DNA of two pathogenic bacteria, namely Coxiella burnetii (5.1%) and Rickettsia aeschlimannii (0.6%), detected in human head lice, as well as the DNA of potential new species from the Anaplasma and Ehrlichia genera of unknown pathogenicity. The finding of several Malian head lice infected with B. quintana, C. burnetii, R. aeschlimannii, Anaplasma and Ehrlichia is alarming and highlights the need for active survey programs to define the public health consequences of the detection of these emerging bacterial pathogens in human head lice.

Fig 1. Phylogenetic tree showing the relationship between haplotypes identified in this study with other Pediculus humanus haplotypes.

The cytb sequences were aligned using CLUSTALW, and phylogenetic inferences were conducted in MEGA 6 using the maximum likelihood method based on the Kimura 2-parameter for nucleotide sequences. The GenBank accession numbers are indicated at the end. Statistical support for the internal branches of the trees was evaluated by bootstrapping with 1,000 iterations. The codon positions included were 1st+2nd+3rd+Noncoding. There was a total of 270 positions in the final dataset. The scale bar represents a 1% nucleotide sequence divergence.

Fig 2. Phylogenetic position of identified genotypes of C. burnetii, the agent of Q fever.

The concerned sequences (COX2, 5 and 18) were aligned using CLUSTALW, and phylogenetic inferences was conducted in MEGA 6 using the maximum likelihood method, with the complete deletion option, based on the Kimura 2-parameter for nucleotide sequences. There was a total of 1,247 positions in the final dataset.

Fig 3. Phylogenetic tree highlighting the position of Rickettsia spp. identified in the present study compared to other Rickettsia bacteria available on GenBank.

The gltA sequences were aligned using CLUSTALW, and phylogenetic inferences were conducted in MEGA 6 using the maximum likelihood method, with the complete deletion option, based on the Kimura 3-parameter for nucleotide sequences. The GenBank accession numbers are indicated at the end. Statistical support for the internal branches of the trees was evaluated by bootstrapping with 1,000 iterations. The codon positions included were 1st+2nd+3rd+Noncoding. There was a total of 1,161 positions in the final dataset. The scale bar represents a 2% nucleotide sequence divergence.

Fig 4. Phylogenetic tree highlighting the position of Ehrlichia spp. identified in the present study compared to other Ehrlichia bacteria available on GenBank.

The groEl sequences were aligned using CLUSTALW, and phylogenetic inferences was conducted in MEGA 6 using the maximum likelihood method based on the Kimura 3-parameter model for nucleotide sequences. The GenBank accession numbers are indicated at the end. Statistical support for the internal branches of the trees was evaluated by bootstrapping with 1,000 iterations. The codon positions included were 1st+2nd+3rd+Noncoding. There was a total of 570 positions in the final dataset. The scale bar represents a 5% nucleotide sequence divergence.

Fig 5. Phylogenetic tree highlighting the position of Anaplasma spp. identified in the present study compared to other Ehrlichia bacteria available on GenBank.

The rpoB sequences were aligned using CLUSTALW, and phylogenetic inferences were conducted in MEGA 6 using the maximum likelihood method based on the Kimura 3-parameter for nucleotide sequences. The GenBank accession numbers are indicated at the end. Statistical support for internal branches of the trees was evaluated by bootstrapping with 1,000 iterations. The codon positions included were 1st+2nd+3rd+Noncoding. There was a total of 429 positions in the final dataset. The scale bar represents a 10% nucleotide sequence divergence.