Sequencing of body louse genome will lead to new insect disease
14 July 2010
A global research team led by scientists from the J. Craig
Venter Institute (JCVI) have sequenced and analysed the body louse
Comparative studies of the body louse genome with other sequenced
species revealed features that will enhance our understanding of the
relationships between disease-vector insects, the pathogens they
transmit, and the affected human hosts.
The human body louse, Pediculus humanus humanus, is a
human parasite and is responsible for the transmission of bacteria
that cause epidemic typhus, relapsing fever and trench fever. The
team at the JCVI focused on the DNA sequencing, genome assembly and
identification of genes.
Ewen Kirkness, PhD of JCVI, directed the sequencing and
gene-finding efforts in the project. Detailed analysis of the genome
was conducted by a large international group of 71 scientists,
coordinated by Barry Pittendrigh, University of Illinois, and
Professor Evgeny Zdobnov, University of Geneva Medical School.
In addition to the targeted louse genome, the project
unexpectedly yielded the complete genome sequence of a bacterial
species, Riesia, that lives in close association with lice,
and which is essential for survival of the insects. This study
revealed that, despite having the smallest known insect genome (108
Mb) and a parasitic lifestyle, the body louse has retained a
remarkably complete repertoire of 10,773 protein-coding genes.
The compactness of the louse genome helped to predict the encoded
genes accurately. The researchers believe that the genome will be a
valuable reference for evolutionary studies of insect species,
especially in the areas related to insect growth and development.
The body louse usually lives in clothing, with infestations
associated with unwashed clothes for prolonged time. Infestations of
body lice and the closely related head lice can cause a range of
problems in humans from mild irritations to serious disease. The
body louse can carry harmful bacteria, such as Rickettsia
prowazekii that causes epidemic typhus, and is classified as a
category B bioterrorism agent.
Body and head lice are also becoming increasingly resistant
to traditional pesticides so the sequencing of the body louse genome
will help in the important search for new control methods
facilitated by detailed molecular studies. Having the complete
genome of the bacteria, Riesia, that lives within lice and
provide the lice with essential nutrients such as vitamin B5,
provides additional potential targets for lice eradication.
According to lead author Dr. Kirkness, "With the genome sequences
of the human host, the body louse parasite, and the Riesia
endosymbiont now in hand, researchers have the opportunity to gain
greater insights into the co-evolution of a host-parasite-symbiont
trio with the potential outcome being eradication of the body