Fog fever: Provocation tests with Dictyocaulus viviparus

There have been many suggestions that fog fever of cattle is the result of a hypersensitivity to Dictyocaulus viviparus. However, when 7 adult cattle that had recovered from fog fever were challenged orally with 30 000 third-stage larvae of D. viviparus, the acute respiratory signs did not recur. Pulmonary lesions comparable to those of reinfection husk and unlike those of fog fever were found at post mortem examination of the 7 animals, one month after challenge. It is concluded that there is no evidence that fog fever occurs as the result of a hypersensitivity reaction in sensitized cattle to oral reinfection with d. viviparus larvae.