Nose-rings and transmission of helminth parasites in outdoor pigs

Five growing pigs experimentally infected with low doses of Oesophagostomum dentatum, Ascaris suum, and Trichuris suis were turned out with 5 helminth -naive pigs on each of 3 pastures in June 1996 (Group I). On one pasture al l pigs received nose-rings. After slaughter of Group 1 in October, pasture infectivity was monitored using helminth-naive, unringed tracer pigs. In 19 97, helminth-naive young pigs were turned out on the contaminated pastures in May (Group 2) and again in August (Group 3). Again all pigs on one pastu re received nose-rings. All pigs and pastures were followed parasitological ly and reduction in grass cover was monitored. Based on the acquisition of infection by the naive pigs in Group I, the estimated minimal embryonation times for eggs deposited on pasture were 23-25 days for O, dentatum, 5-6 we eks for A. suum acid 9-10 weeks fur T. suis. Results from tracer pigs and g rass/soil samples indicated that pasture infectivity was light both years. Free-living stages of O. dentatum did not survive the winter. The nose-ring s reduced rooting considerably, resulting in three-fold more grass cover on the nose-ring pasture compared to the control pastures by the end of the e xperiment. Nevertheless, the nose-rings did not significantly influence par asite transmission.