The potential role of blowflies in the transmission of taeniid tapeworm eggs

Abstract

In laboratory studies with 3 spp. of Calliphora more than half were shown to ingest eggs of Taenia hydatigena from the surface of dog feces with a maximum of > 5000 eggs in 1 fly. Most eggs were voided within 48 h and between 38-48% of these eggs had lost their embryophores. In field studies carried out in the South Island of New Zealand, traps baited with dog feces captured the following blowfly species in decreasing order of abundance; Hybopygia rarja, C. quandrimaculata, C. hotona and C. stygia. Peak numbers were trapped in Jan., Feb and March. Almost 25% of wild flies, caught after feeding for up to 3 min of dog feces naturally contaminated with taeniid eggs, had eggs in their intestine. When administered to lambs all 4 spp. of fly transferred infection. Lambs grazed in winter on plots near kennels that had housed dogs with patent infections of T. hydatigena acquired higher worm burdens than those grazed further away. The burdens were greater downwind of the prevailing wind. After removal of the dogs, blowflies caught in the vicinity contained taeniid eggs but the contents of pitfall traps did not. Blowflies, and to a much lesser dgree the insects and dust caught on sticky traps during the presence of the dogs, transferred infection when administered to naive lambs.