Schistosoma mansoni infection in Biomphalaria glabrata: Alterations in heart rate and thermal tolerance in the host

Abstract

It has been demonstrated that there is a reduction of heart rate (beats/min) in nonparasitized Biomphalaria glabrata as a function of increased shell diameter. When the heart rates of noninfected B. glabrata and those of specimens infected with larval Schistosoma mansoni are compared over a period of 8 weeks post-infection, it has been determined that there is a significant increase from the 4th week on in the latter. The influence of ambient temperatures on the heart rates of infected and noninfected B. glabrata has also been studied. It has been ascertained that, with the exception of 33°C, the heart rates of infected snails are consistently greater than those of control snails within the 23–33°C range. Infected snails demonstrate a lowered higher thermal tolerance limit than uninfected ones, with 40% dying within 5 days when maintained at 33°C. Furthermore, there is a rapid decline in their heart rates prior to death. When maintained at 28°C for 10 weeks, 75% mortality has been recorded among snails each infected with 10 miracidia, while the mortality rate during the same period among identically maintained, uninfected snails is only 40%.