The role of chewing lice (Phthiraptera: Philopteridae) as intermediate hosts in the transmission of Hymenolepis microps (Cestoda: Cyclophyllidea) from the willow ptarmigan Lagopus lagopus (Aves: Tetraonidae)

The cestode Hymenolepis microps is an intestinal parasite of tetraonid birds, in- cluding the willow ptarmigan (Lagopus lagopus). This parasite is able to maintain a high prevalence and intensity throughout the year, even in a subarctic environ- ment in bird populations with relatively low host densities, indicating effective transmission routes. Willow ptarmigan consume mainly vegetal material and ac- tive consumption of invertebrates is confined to the first two or three weeks of life. Ptarmigan are infected by different species of ectoparasites, of which two species of feather lice, Lagopoecus affinis and Goniodes lagopi, are the most abun- dant. In this study, we explored the hypothesis that feather lice may be suitable intermediate hosts for H. microps. We applied histological techniques and light microscopy to investigate lice for the presence of larval cestode stages (cysticer- coids). We found 12 cysticercoid-like structures inside chewing lice collected on L. lagopus hosts harbouring H. microps. In addition, a polymerase chain reaction (PCR) screening of Ischnocera lice DNA, targeting the 18S rRNA gene of the ces- tode, showed positive results for two different short fragments of the 18S rRNA gene of H. microps which were sequenced from lice collected on birds. Both inde- pendent lines of evidence support the hypothesis that Ischnocera lice might be suitable intermediate hosts in the life cycle of H. microps in L. lagopus.