Cercarial emergence pattern of Schistosoma haematobium from Libreville, Gabon.

Although schistosomiasis has been a public health issue in Gabon for nearly a century, little is known about its current transmission dynamics. We analyzed the chronobiology of 137 cercarial emission profiles of Schistosoma haematobium from Libreville, the capital of Gabon, located in an open area for schistosomiasis. We found that 88% of the cercariae were shed between 11 a. m. and 3 p. m. and that the average pattern was of circadian type, with the average peak at 1 p. m., and representing 27% of the total number of cercariae of the day. The rhythms of emergence may be associated with environmental pressures on the parasite, especially those related to their definitive hosts.