Ascaris suum infection in calves. I. Clinical signs.

Clinical signs consistent with those of atypical interstitial pneumonia (AIP) were induced in calves sensitized with infective Ascaris suum eggs at seven to 20 weeks of age and challenged at three-week intervals one or more times. These signs usually appeared on the sixth or seventh day postinfection and reached maximum severity between the tenth and 13th days following infection. Prominent signs were: dyspnea, often with expiratory grunt, coughing, mouth breathing and emphysema as well as increased respiration and heart rates. In general, the intensity of signs was dependent upon dose size, although a single small dose resulted in acute signs and death in one calf. Intermittent coughing and vesicular sounds were induced in calves given A. suum eggs continually over prolonged periods. No respiratory abnormalities resulted from challenge with Toxocara canis after sensitization with A. suum. Antihistamine therapy did not alter the clinical signs in A. suum infected calves.