IMPAIRED PULMONARY GAS-EXCHANGE IN EWES NATURALLY INFECTED BY SMALL LUNGWORMS

Respiratory rate and blood gases were studied in 2 groups of ewes: the ewes in group 1 (9 ewes) acted as uninfected controls and those in gr oup 2 (6 ewes) were infected with small lungworms (Muellerius, Cystoca ulus, Protostrongylus and <1% Neostrongylus). The respiratory rate was higher in infected (49 +/- 19 breath min(-1) than in uninfected ewes (20 +/- 3 breath min(-1)); it was strongly reduced after treatment (49 vs 22) in infected ewes. The partial carbon dioxide arterial tension (PCO2), total CO2 and HCO3- were higher (respectively 77 vs 39 mmHg, 3 8 vs 23 mmol l(-1) and 35 vs 23 mmol(-1)) in infected compared with un infected ewes, whereas arterial pH (7.2 vs 7.4) and partial oxygen ten sion PO2 were lower (41 vs 81 mmHg) in infected ewes. Group 2 was trea ted with fenbendazole (at 15 mg kg(-1) bodyweight) to eliminate small lungworms, and the respiratory rate and blood gases were measured 3 we eks after treatment. The values after treatment were similar to those in uninfected ewes. It is concluded that heavy infections by small lun gworms in ewes impairs gas exchange, but that gas exchange improves ra pidly after treatment. Copyright (C) 1996 Australian Society for Paras itology. Published by Elsevier Science Ltd.