  Wolbachia are common endosymbionts of terrestrial arthropods, and are also
found in nematodes: the animal-parasitic filaria, and the plant-parasite
Radopholus similis. Lateral transfer of Wolbachia DNA to the host genome is
common. We generated a draft genome sequence for the strongyloidean nematode
parasite Dictyocaulus viviparus, the cattle lungworm. In the assembly, we
identified nearly 1 Mb of sequence with similarity to Wolbachia. The fragments
were unlikely to derive from a live Wolbachia infection: most were short, and
the genes were disabled through inactivating mutations. Many fragments were
co-assembled with definitively nematode-derived sequence. We found limited
evidence of expression of the Wolbachia-derived genes. The D. viviparus
Wolbachia genes were most similar to filarial strains, and strains from the
host-promiscuous clade F. We conclude that D. viviparus was infected by
Wolbachia in the past. Genome sequence based surveys are a powerful tool for
revealing the genome archaeology of infection and symbiosis.
