Harmful parasites of the wild northern boreal mammals are still surprisingly poorly studied. In 2003-2006, a peritonitis outbreak caused by the filarioid nematode, Setaria tundra, emerged in Finland's reindeer population. In order to gain knowledge about the basic biology, epidemiology, and transmission dynamics of this parasite, samples for S. tundra were collected from reindeer and other cervids during the follow-up period 2004-2006. Using morphology and molecular biology methods, we describe here S. tundra's first larval stage, microfilaria (smf), for the first time scientifically. The prevalence and densities of smf were higher in reindeer calves than in adults, overall prevalence being 42%. The overall smf prevalences for moose, wild forest reindeer and roe deer were 1.4-1.8%, 23%, and 39%, respectively. The focus of microfilaremia moved north and settled down in the south simultaneously with the peritonitis outbreak. The peak microfilaremia occurred in the first summer after the infection, and smf disappeared from the blood after 2 years. Captive reindeer were smf positive over the year. The prepatent period of S. tundra was estimated to be about 4 months, and the life span at least 14 months. This parasite likely has an important impact on boreal ecosystems.

Background: Recent studies have revealed expansion by an array of Filarioid nematodes' into the northern boreal region of Finland. The vector-borne nematode, Setaria tundra, caused a serious disease outbreak in the Finnish reindeer population in 2003-05. The main aim of this study was to understand the outbreak dynamics and the rapid expansion of S. tundra in the sub arctic. We describe the vectors of S. tundra, and its development in vectors, for the first time. Finally we discuss the results in the context of the host-parasite ecology of S. tundra in Finland

No abstract

No abstract

No abstract