[Biology of cestodes of domestic ducks and wild water birds]

Life cycles of 16 cestode species of the families Hymenolepididae and Diploposthidae were studied in 52 ponds of the State Fishery in Bohemia and Moravia. The parasites were recovered from domestic ducks kept on the ponds and from wild birds, mostly of the genera Anas and Aythya, occurring in these water biotopes. Cestode larvae were found in 9 species of Copepoda (9669 out of 1 600 200 examined specimens, i. e. 0.6%) and 3 species of Ostracoda (500 out of 272 300 examined specimens, i. e. 0.18%). Five species of water snails serving as reservoir hosts harboured cysticercoids of 5 cestode species (680 out of 10 212 examined specimens, i. e. 6%). The studies of cestode life cycle under natural conditions were supplemented with 680 successful experiments with intermediate hosts and 179 successful experiments with definitive hosts. The development of larvae was related to the temperature and lasted approximately 13-20 days at 18-25 degrees C. The highest intensity of infection occurred incrustaceans under experimental conditions, a lower intensity was found in crustaceans from duck farms and the lowest in crustaceans from other parts of ponds (e. g., in the case of Fimbriaria fasciolaris in Copepoda, 37, 22 and 10 cysticercoids). The intermediate hosts infected with cestode larvae can live for 3-6 weeks (Copepoda) and 4-7 weeks (Ostracoda) and after invagination of cysticercoids for 20-25 days, on the average. The cysticercoids survive their hosts for 14-18 h at 4-6 degrees C, for 10-11 h at 12-14 degrees C, for 6-7 h at 18-20 degrees C and for 3-4 h at 24-26 degrees C. If they are swallowed by water snails at that time (dead crustaceans are a component of their food), they survive in their digestive tract even for two years (the longest period demonstrated experimentally) and after this time they are able to develop into an adult cestode in the definitive host. The infectivity of cysticercoids increases with their age. It is the lowest immediately after invagination (10-15%), during the stay of cysticercoids in crustaceans it gradually increases (30-60% on days 10-20 after invagination) and it is the highest in cysticercoids from snails (45-55% after 20-50 days in snails, 60-80% after 50-100 days in snails and 70-90% after more than 100 days in snails).