Observations on Echinostoma revolutum and Echinostoma trivolvis in single and concurrent infections in domestic chicks.

Studies were done to determine specific differences between adults of Echinostoma revolutum and Echinostoma trivolvis grown singly and concurrently in domestic chicks. Worm recovery at 10-21 days post-infection (p.i.) of E. revolutum and E. trivolvis in singly infected chicks was 21 and 17%, respectively; in concurrent infections, worm recovery for E. revolutum and E. trivolvis was 21 and 16%, respectively. The body area of E. trivolvis was 1.5-2.0 times greater than that of E. revolutum at 10-21 days p.i. Most body organ measurements of the suckers and gonads at 10, 14 and 21 days p.i. were significantly greater in E. trivolvis compared with those of E. revolutum. The mean dry weight/worm at 14 days p.i. was 2.5 mg for E. trivolvis and 1.0 mg for E. revolutum. In single infections, E. revolutum was found only in the rectum and E. trivolvis mainly in the lower ileum, and in concurrent infections worms of both species were found in the rectum. Contrary to a previous report that stated that the body size of adult worms is not a reliable taxonomic indicator between E. revolutum and E. trivolvis, the findings reported here show that body area and organ size can be used to distinguish these closely related species.