SRA

Dictyocaulus viviparus, the bovine lungworm, is the cause of parasitic bronchitis in cattle (husk, verminous pneumonia, dictyocaulosis) with a world wide distribution in temperate areas. The predominant hosts are cattle, but it can also be found in small ruminants (sheep, goats) and deer. Infection occurs on pasture as infective larvae develop from L1 that are shed with the feces to free-living infective L3 that are ingested by cattle while grazing. Free-living larvae do not feed; survival on pasture is therefore limited to a few months depending on temperature and humidity. The parasite is able to interrupt development inside the host. Infective larvae that have been exposed to low temperatures on pasture before infection subsequently develop only to preadult larval stages that survive winter conditions as hypobiotic larvae in the lung and resume development in spring. These animals contaminate pastures the following spring and represent the major source of infection for other susceptible cattle.