Abstract
Bronchial asthma such as is seen in humans was successfully produced in male mongrel dogs sensitive to Ascaris suum worms. Seventy to eighty percent of all dogs showed a positive skin reaction to Ascaris antigen. In dogs with high skin reactivity, an inhalation of Ascaris antigen produced increases in airway resistance and respiratory rate. Ascaris extract given intravenously caused systemic anaphylactic shock in the form of prolonged hypotension and dyspnea. Toxocara canis showed the same responses as seen with Ascaris, and a cross reaction between these antigens was suggested. Hypersecretion of respiratory tract fluids was also observed with inhalation of Ascaris. On the other hand, Ascaris extract had no effect in guinea pigs and rats, either in vivo or in vitro. The pulmonary and systemic responses produced by Ascaris extract are, therefore, considered to be the result of antigen-antibody reactions, and not pharmacological effects of Ascaris extract. The increase in airway resistance produced by the antigen in dogs was significantly inhibited by disodium cromoglycate, atropine or hexamethonium, and reduced by chlorpheniramine, suggesting that mast cells and cholinergic pathways are both significantly involved in the responses. The Ascaris-induced bronchial asthma resembled the asthma which occurs in humans, both symptomatically and pathophysiologically, and we propose that the model may be feasible for studies of asthma related to allergies.
