9715

• UCREFRP Catalog Number: 9715
• Author: Ward, D.
• Title: Removal and quantification of Asian tapeworm from endangered cyprinid fishes using Praziquantel.
• USFW Year: 2005.
• USFW - Doc Type: Arizona Game and Fish Department.
• Copyright Material: NO

because the parasite is killed within the host more quickly but the speed of evacuation from the

host appears to be related to normal digestion rates. Peterson and Barfoot (2003) found that 90

percent of prey items were evacuated from northern pikeminnow within 27 hours of ingestion at

180C. Evacuation of Asian tapeworms from the digestive tract of the host, following treatment

with Praziquantel, appears to be similar to normal digestion and evacuation rates of other

cyprinids at similar temperatures (Specziar 2002, Stone 2004). Even with high doses of

praziquantel fish still have to be held for at least 24-h in order to accurately quantify tapeworm

loads for monitoring

Typically co-evolved parasites do not greatly impact host populations but only kill

otherwise compromised or weakened individuals. Parasites that are not co-evolved, can act as .

regulatory agents in animal populations (May 1983). High tapeworm infestation may be one of

the factors contributing to the continued decline of native Colorado River fishes. Reduced

growth, as a result of high Asian tapeworm infestation, may also increase predation risk and

decrease survival of endangered cyprinid fishes. The interaction of slow growth and increased

early-life mortality is already considered an important cause of Colorado pikeminnow declines

in the upper Colorado River basin (Kaeding and Osmundson 1988).

Exhaustive exercise in combination with starvation leads to mortality in small rainbow trout

(Simpkins et al. 2004). The combination of tapeworm infestation, limited food and exhaustive

swimming may also lead to direct mortality of small humpback chub that exit the little Colorado

River and are forced to swim in the swift mainstem Colorado River.

Low numbers of Asian tapeworm have been found in cyprinid fishes inhabiting the

mainstem Colorado River (Brouder and Hoffnagle 1997). The perennially cold water in the

Colorado River mainstem is believed to prohibit Asian tapeworm from completing its life cycle,

although adult worms have been shown to overwinter at water temps as low as SOC in fathead