Biology of Spirometra Species in Peninsular Malaysia

This study was initiated to elucidate the life-cycle of the Spirometra sp. from Malaysian frog, Rana cancrivora Gravernhorst, in order to determine the identity of the Spirometra sp. It is the first time that the life cycle of the Malaysian Spirometra species was elucidated. The study reveals that 14.2% of R. cancrivora are infected with spargana (with a range of 1-8 spargana per frog) in the study site. The spargana from R. cancrivora, the second intermediate host of the Malaysian Spirometra sp. in nature, were fed to three local cats, Felis sp. (two spargana per cat) where they matured to adult worms. Eggs were obtained from the faeces of the infected cats on the 12-14th days post-infections in two cats and 60 days post-infection in the third cat. The eggs were hatched in tap water (left overnight) to obtain the coracidia which were then fed successfully to the local species of copepods collected from the same field location as the infected wild frogs. Preliminary investigation also shows that 5.4% of the same species of copepods in the wild, are infected with procercoids. The copepods infected with procercoids were next fed to 15 golden hamster mice which served as a substitute intermediate host in the laboratory. In these 15 hamster mice the procercoids developed into spargana (plerocercoids) in the thigh muscles. Six spargana were recovered from the 15 hamster mice, with a recovery rate of 1.11% for 10 days post infection and 0.22% for 14 days post infection. The spargana from the hamster mice were then fed to two cats (2 spargana per cat and 3 spargana per cat) and eggs were recovered after 10 -13 days post infection and 2 adult worms recovered after sacrifice the cat infected with two spargana. The life-cycle of the Malaysian Spirometra resembles that of S. erinacei and S. mansonoides. Based on the morphology and measurements of the eggs, coracidia, procercoid, spargana and adult worms, the Malaysian Spirometra species is similar to S. erinacei. However, preliminary molecular biology investigations based on DNA extracted from adult worms recovered from the laboratory infected cats, the Malaysian Spirometra species are found to be 90% similar to S. erinacei. This study is not conclusive, therefore a more detailed morphological, molecular and protein analysis should be done to compare the Malaysian Spirometra species with the other known Spirometra species. However, this study has achieved an important milestone by elucidating the life cycle of the Malaysian Spirometra species for the first time in a laboratory model. Thus opening the way for a more basic and applied research approach in establishing the importance of the parasite as a potential public health problem in the current globalized environment.