Prevalence of acanthocephalans in birds of prey from the Middle East and report of two clinical cases.

Sir, Acanthocephalan (“spiny-headed”) worms are enteroparasites of birds characterised by a retractile proboscis armed with rows of thorns (Lacina & Bird, 2000). They penetrate the intestinal mucosa with the proboscis causing inflammation and nodules (Heidenreich, 1997). An arthropod (insect or mollusk) becomes the first intermediate host ingesting acanthocephalan eggs that contain the larvae (acanthor). Small vertebrates, such as the common and pigmy shrews (Sorex araneus and S. minutus) act as paratenic hosts that cumulate encysted larval stages in their bodies, eventually passing the infestation to the definitive host, the bird of prey, when ingested (Cooper, 2005). Several species, including Centrorhynchus globocaudatus in the peregrine falcon (Heidenreich, 1997), have been described in birds of prey. However, little is known about the pathogenicity of thorny-headed worms (Cooper, 2005) and their prevalence in raptors from the Middle East. Microscopic examination of 3,988 fresh fecal samples from captive falcons from Kuwait (n = 1,706) and Dubai (n = 2,282) was performed between 2003 and 2006. Only two cases (0.05 %) of infestation due to acanthocephalans were recorded, one in Kuwait and one in Dubai, both in saker falcons (Falco cherrug) showing compatible clinical signs (Table I) and high number of acanthocephalan eggs (Fig. 1), 52-60 × 20-30 μm in size, easily distinguishable due to their dark pigmentation. Eggs contain a small larva complete with hooked proboscis. Although Acanthocephala are generally considered to have the lowest prevalence amongst the endoparasites of birds of prey (Cooper, 2005), as confirmed in the present report (0.05 %) from the Middle East, 15 % of Falconiformes investigated in Spain were found infested with acanthocephalans (Illescas et al., 1993). In Catalonia alone, 6.7 % of raptors (one Buteo buteo, two Circaetus gallicus and five Falco tinnunculus) harboured acanthocephalans (Ferrer et al., 2004). But in Galicia (northwest Spain), only one bird out of 285 was infested (Sanmartin et al., 2004). In raptors from Poland