Genomic insights into the Ixodes scapularis tick vector of Lyme disease

Abstract

Ticks transmit more pathogens to humans and animals than any other arthropod. Wedescribe the 2.1 Gbp nuclear genome of the tick, Ixodes scapularis (Say), which vectorspathogens that cause Lyme disease, human granulocytic anaplasmosis, babesiosis and otherdiseases. The large genome reflects accumulation of repetitive DNA, new lineages of retrotransposons,and gene architecture patterns resembling ancient metazoans rather thanpancrustaceans. Annotation of scaffolds representing B57% of the genome, reveals 20,486protein-coding genes and expansions of gene families associated with tick?host interactions.We report insights from genome analyses into parasitic processes unique to ticks, includinghost ?questing?, prolonged feeding, cuticle synthesis, blood meal concentration, novel methodsof haemoglobin digestion, haem detoxification, vitellogenesis and prolonged off-hostsurvival. We identify proteins associated with the agent of human granulocytic anaplasmosis,an emerging disease, and the encephalitis-causing Langat virus, and a population structurecorrelated to life-history traits and transmission of the Lyme disease agent.