Determination of Life Cycle Stages of Body Cavity Fluke Cyclocoelids (Cyclocoelidae) in Terrestrial Snails and Experimental Exposure of Domestic Chickens (Gallus gallus)
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Zoos and other bird-holding facilities world-wide recently have reported serious health problems and frequently deaths of captive birds in exhibits associated with infections by introduced species of cyclocoel (Digenea) parasites. These adult flukes apparently have been introduced into these facilities by the importation of infected exotic birds. The larval stages of digenean species generally develop within either aquatic or terrestrial snails. A few of the life cycles of cyclocoelids that utilize aquatic snails as the molluscan host have been documented; however, very little is known about the life cycle of the species introduced into bird-holding facilities where the larval stages are produced in terrestrial snails. A more complete understanding of these terrestrial-based life cycles is essential for the effective prevention and treatment of infected birds. Ultimately, our objective is the development of practical control strategies for these parasites in zoos. In this study, 16 of 53 terrestrial snails (30%) of the genus Subulina from Lincoln Park Zoo, Chicago, Illinois were found to be infected with cyclocoelid parasites of the genus Szidatitrema. Larval stages (redial generations, cercariae, metacercariae, and young adults) of the parasite taken from these snails were described and illustrated. Metacercariae were suspended in a saline solution administered to 15 one-day old chickens. Five control chickens were given saline solution. Fecal samples were taken weekly from experimental and control chickens to determine if eggs were present through sedimentation and floatation procedures. Blood samples were obtained from chickens every other week starting in the second week post-exposure. A total of eight chickens were necropsied starting on Day 67. Experimental infections were not successful; there were no differences between levels of eosinophils or fibrinogen in experimental chicks compared to control chicks, and helminth eggs were not found in any fecal floatation. No adult flukes were found during necropsy. Further studies should include attempts to experimentally infect additional bird hosts including monk parakeets from the Schubot breeding colony at Texas A&M University, testing of different exposure methods, and determination of any potential secondary intermediate hosts or paratenic hosts. Once experimental bird hosts have been successfully infected in a laboratory setting, vaccines, drug trials, and potential detection methods for this fluke should be considered.
Arenaz, Cristina M (2015). Determination of Life Cycle Stages of Body Cavity Fluke Cyclocoelids (Cyclocoelidae) in Terrestrial Snails and Experimental Exposure of Domestic Chickens (Gallus gallus). Master's thesis, Texas A & M University. Available electronically from