Dictyocauliasis in a dairy herd

An outbreak of clinical dictyocauliasis in a dairy herd comprising twenty-s ix cows and five heifers is described. The index was a purchased animal whi ch began coughing several days after introduction to the herd in March. A f ew weeks later several other co,ls started to cough, and by July the clinic al signs became more severe: milk production decreased and affected animals lost weight. Clinical examination revealed moderate to severe bronchopneum onia. Fecal ecamination revealed Dictyocaulus viviparus larvae in eight ani mals resulting in a diagnosis of verminous pneumonia. Factors which could h ave favoured the development and survival of D. viviparus and were therefor e assumed to contribute to rite occurence of the disease included pasture m anagement, as the cattle grazed one of two pastures of only one and two hec tares for 78 days from April to July, rainy weather and mild temperatures.