[Lungworm disease in dairy cattle: symptoms, diagnosis, and pathogenesis on the basis of four case reports].

Clinical lungworm disease appears to occur frequently in Dutch dairy herds. Because the clinical diagnosis is difficult to make in adult cattle, the clinical diagnosis, laboratory diagnosis, differential diagnosis, therapy, and prevention are discussed in this article. In addition, four cases of lungworm disease in adult cattle are presented. The main clinical complaints were coughing, decreased milk production, and weight loss. Several lactating cows died in one herd. The disease history of four herds revealed that introduction of susceptible cows or heifers to herds with cows with subclinical patent lungworm infections had resulted in a pasture infection, leading to clinical problems in both the newly introduced and 'resident' cows of the herd. Further history analysis of the fourth herd revealed that re-introduction of lungworm infection by newly purchased cows in a lungworm free herd resulted in clinical lungworm problems in adult and young animals. The fourth case led to the conclusion that lungworm infection must have been re-introduced by cows purchased from another farm.