Life Cycle of Didilia Ooglypta (Nematoda: Tetradonematidae), a Parasite of Phlebotomine Sandflies of Afghanistan

Abstract

Didilia ooglypta is a parasitic nematode of Phlebotomus papatasi and P. sergenti (Diptera: Psychodidae) in Afghanistan. The vulva of the nematode is located at the front tip of the body close to the mouth. The only free-living stage is the egg and all other stages live in the body cavity of the host. First instar sandfly larvae become infected by ingesting nematode eggs; 2nd, 3rd and 4th instars are not susceptible. The infective juvenile worms hatch in the mid-gut of the sandfly larva and migrate through the gut wall into the haemocoel where they complete their development. After mating, female nematodes begin to develop quickly while the males shrink and die. Female nematodes are fully mature after 37 days of infection by the time the adult flies emerge from pupae, at which stage they bore a hole through the cuticle of the abdomen of the imago to expose the vulva and lay eggs. The eggs survive for two and a half years in humid larval frass, but almost all die within two weeks in water. The development of infected larvae is retarded and, compared to uninfected larvae, significantly fewer survive to the imago stage. Infection causes an inversion in the normal pattern of emergence of sandflies with more females than males emerging in the first three days. P. duboscqi, a sandfly closely related to P. papatasi, is susceptible to infection, but sandflies of the subgenus Larroussius do not fully support the development of the parasite.