As an obligatory parasite of humans, the body louse ( Pediculus humanus humanus ) is an important vector for human diseases, including epidemic typhus, relapsing fever, and trench fever. Here, we present genome sequences of the body louse and its primary bacterial endosymbiont Candidatus Riesia pediculicola. The body louse has the smallest known insect genome, spanning 108 Mb. Despite its status as an obligate parasite, it retains a remarkably complete basal insect repertoire of 10,773 protein-coding genes and 57 microRNAs. Representing hemimetabolous insects, the genome of the body louse thus provides a reference for studies of holometabolous insects. Compared with other insect genomes, the body louse genome contains significantly fewer genes associated with environmental sensing and response, including odorant and gustatory receptors and detoxifying enzymes. The unique architecture of the 18 minicircular mitochondrial chromosomes of the body louse may be linked to the loss of the gene encoding the mitochondrial single-stranded DNA binding protein. The genome of the obligatory louse endosymbiont Candidatus Riesia pediculicola encodes less than 600 genes on a short, linear chromosome and a circular plasmid. The plasmid harbors a unique arrangement of genes required for the synthesis of pantothenate, an essential vitamin deficient in the louse diet. The human body louse, its primary endosymbiont, and the bacterial pathogens that it vectors all possess genomes reduced in size compared with their free-living close relatives. Thus, the body louse genome project offers unique information and tools to use in advancing understanding of coevolution among vectors, symbionts, and pathogens.

Ticks transmit more pathogens to humans and animals than any other arthropod. We describe the 2.1 Gbp nuclear genome of the tick, Ixodes scapularis (Say), which vectors pathogens that cause Lyme disease, human granulocytic anaplasmosis, babesiosis and other diseases. The large genome reflects accumulation of repetitive DNA, new lineages of retro-transposons, and gene architecture patterns resembling ancient metazoans rather than pancrustaceans. Annotation of scaffolds representing ∼57% of the genome, reveals 20,486 protein-coding genes and expansions of gene families associated with tick–host interactions. We report insights from genome analyses into parasitic processes unique to ticks, including host ‘questing’, prolonged feeding, cuticle synthesis, blood meal concentration, novel methods of haemoglobin digestion, haem detoxification, vitellogenesis and prolonged off-host survival. We identify proteins associated with the agent of human granulocytic anaplasmosis, an emerging disease, and the encephalitis-causing Langat virus, and a population structure correlated to life-history traits and transmission of the Lyme disease agent.

This work is intended as a consensus list of valid tick names, following recent revisionary studies, wherein we recognize 896 species of ticks in 3 families. The Nuttalliellidae is monotypic, containing the single entity Nuttalliella namaqua. The Argasidae consists of 193 species, but there is widespread disagreement concerning the genera in this family, and fully 133 argasids will have to be further studied before any consensus can be reached on the issue of genus-level classification. The Ixodidae comprises 702 species in 14 genera: Amblyomma (130 species, of which 17 were formerly included in Aponomma, a genus that is still considered valid by some authors), Anomalohimalaya (3), Bothriocroton (7, all previously included in Aponomma), Cosmiomma (1), Cornupalpatum (1), Compluriscutula (1), Dermacentor (34, including the single member of the former genus Anocentor, which is still considered valid by some authors), Haemaphysalis (166), Hyalomma (27), Ixodes (243), Margaropus (3), Nosomma (2), Rhipicentor (2) and Rhipicephalus (82, including 5 species from the former genus Boophilus, which is still considered valid by some authors). We regard six names as invalid: Amblyomma laticaudae Warburton, 1933 is a synonym of Amblyomma nitidum Hirst & Hirst, 1910; Bothriocroton decorosum (Koch, 1867) is a synonym of B. undatum (Fabricius, 1775); Haemaphysalis vietnamensis Hoogstraal & Wilson, 1966 is a synonym of H. colasbelcouri (Santos Dias, 1958); Haemaphysalis xinjiangensis Teng, 1980 is a synonym of H. danieli Č erný & Hoogstraal, 1977; Hyalomma erythraeum Tonelli-Rondelli, 1932 is a synonym of H. impeltatum Schulze and Schlottke, 1930 and Rhipicephalus hoogstraali Kolonin, 2009 was not described according to the rules of the International Code of Zoological Nomenclature.

In recent years there has been much progress in our understanding of the phylogeny and evolution of ticks, in particular the hard ticks (Ixodidae). Indeed, a consensus about the phylogeny of the hard ticks has emerged which is quite different to the working hypothesis of 10 years ago. So that the classification reflects our knowledge of ticks, several changes to the nomenclature of ticks are imminent or have been made. One subfamily, the Hyalomminae, should be sunk, while another, the Bothriocrotoninae, has been created (Klompen, Dobson & Barker, 2002). Bothriocrotoninae, and its sole genusBothriocroton, have been created to house an early-diverging (‘basal’) lineage of endemic Australian ticks that used to be in the genusAponomma. The remaining species of the genusAponommahave been moved to the genusAmblyomma. Thus, the nameAponommais no longer a valid genus name. The genusRhipicephalusis paraphyletic with respect to the genusBoophilus. Thus, the genusBoophilushas become a subgenus of the genusRhipicephalus(Murrell & Barker, 2003). Knowledge of the phylogenetic relationships of ticks has also provided new insights into the evolution of ornateness and of their life cycles, and has allowed the historical zoogeography of ticks to be studied. Finally, we present a list of the 899 valid genus and species names of ticks as of February 2004.

Ticks of Australia. The species that infest domestic animals and humans