g. O. jakutensis ( Plenge-Bönig et al., 1995)] or worm nest [e.g. W. bancrofti ( Norões et al., 1997)], apparently preventing the accumulation of leukocytes on the worms’ surface. In these species, there is no evidence that Wolbachia is involved in immune evasion, and its role may ‘simply’ be metabolic provisioning, although clearly there are filarial

taxa that thrive without it. Secondly, the Onchocerca spp. with degenerated musculature in the female and a sessile lifestyle in fibrous nodules (O. ochengi, O. volvulus and Onchocerca gibsoni) may depend on a Wolbachia-mediated “immunological blockade”, comprising a local neutrophilia that interferes with eosinophil infiltration and degranulation ( Nfon selleckchem et al., 2006). The only known Wolbachia-negative Onchocerca spp., O. flexuosa, may utilise a third strategy as the females are sessile in fibrous nodules, yet do not invoke a neutrophilic response ( Brattig PLX3397 mw et al., 2001). Evidence from partial genome sequencing has demonstrated that this species once harboured Wolbachia ( McNulty et al., 2010). One mechanism by which

it may have compensated for loss of the endosymbiont is to have accelerated its development to sexual maturity, as it appears to have a much shorter lifespan than the Wolbachia-positive nodular species ( Plenge-Bönig et al., 1995). Females of Onchocerca spp. that do not form nodules and which have retained a well-developed somatic musculature

[e.g. O. gutturosa ( Franz et al., 1987)] are probably not as active as L. loa, but nevertheless, may retain the ability to dislodge host effector cells by sloughing and thus express a variation of the first strategy. Chodnik (1957) suggested that O. armillata is a motile species due to the many vacant tunnels within histological sections. This is in accordance with the histological observations and the experience of manual extraction of adult worms from the aorta wall in our study. Furthermore, the musculature of adult O. armillata female worms is prominent secondly ( Franz et al., 1987), and the immunological reaction described in the current study (i.e., dominated by macrophages and giant cells, with small numbers of granulocytes more distant) is similar to that reported for O. gutturosa, although it may be less intense ( Wildenburg et al., 1997). The vascular injury noted here and also by Chodnik (1957) provides further support for a nomadic lifestyle for O. armillata. However, definite evidence to support this hypothesis has not been obtained, as it would be extremely difficult to visualise adult worms in vivo in the deep anatomical location of the aorta. The high prevalence (90.7%) of O.