TIME-COURSE OF COPROANTIGEN EXCRETION IN ECHINOCOCCUS-MULTILOCULARIS INFECTIONS IN FOXES AND AN ALTERNATIVE DEFINITIVE HOST, GOLDEN-HAMSTERS

Coproantigen excretion during experimental infections of Echinococcus multilocularis in foxes and an alternative definitive host, golden ham sters, was evaluated by a sandwich ELISA using a monoclonal antibody. A sigmoidal increase of antigen excretion from the developing parasite s was observed in in vitro incubation of the parasites collected on di fferent days during the first 21 days post-infection (DPI). In hamster s, the ELISA O.D. value of faeces became positive at 4 DPI. Thereafter , the O.D. value increased in semi-sigmoidal fashion in the first 42 D PI, probably reflecting the development of the parasites. In foxes, th e O.D. value became positive at 6 DPI. However, contrary to that in ha msters, after the initial steep rise, the O.D. value suddenly decrease d to 1/2 the level during 15-17 DPI, indicating that a large number of worms might have been expelled. The parasite eggs were detected by th e sugar centrifugal-flotation technique (Ito, Yagi & Ishige, 1989) fro m 29 to 84 DPI but not thereafter to 125 DPI, although mature parasite s were detected at 125 DPI. In contrast, positive O.D. values were obt ained almost constantly until 125 DPI, indicating that the coproantige n detection assay was more sensitive than the egg detection assay. The detection limit of the coproantigen detection assay was roughly estim ated to be around 100 worms. These observations, along with the fact t hat the assay was designed to detect a heat-resistant coproantigen in heat-sterilized fecal samples, indicate that the coproantigen detectio n assay is a safe and useful method, not only for diagnosis in the def initive host of E. multilocularis, but also for monitoring parasite de velopment and change in parasite burden during an experimental infecti on. Copyright (C) 1996 Australian Society for Parasitology. Published by Elsevier Science Ltd.