What genes underlie variation in cercarial release time and number?

Overview

After a single schistosome miracidia penetrates a snail, sporocysts grow and divide, and 1000s of single sex clonal miracidia are released. There is genetic variation among schistosomes in the size of the sporocysts, the numbers of cercariae larvae released, and virulence to the snail host.

There is also variation in shedding time – some parasites shed cercariae in the day, while others shed cercariae during the night. We aim to understand the genetic basis of these adaptive parasite traits.

Our work on cercarial shedding time is a collaboration with with Helene Mone and Gabriel Mouahid.

Schistosoma mansoni in Oman form two
populations: one populations shed’s larval
cercaraie from snails in the night and tends
to infect rodents; a second population sheds
cercaraie in the day and tends to infect people.

Helene Mone and Gabriel Mouahid,
our collaborators on work on
schistosome chronobiology

Sign warning swimmers of
schistosomiasis risk in Oman

Representative Papers

Le Clec’h, Winka, Frédéric D Chevalier, Marina McDew-White, Vinay Menon, Grace-Ann Arya, and Timothy J C Anderson. 2021. “Genetic Architecture of Transmission Stage Production and Virulence in Schistosome Parasites”. Virulence 12 (1): 1508-26. https://doi.org/10.1080/21505594.2021.1932183.

Publisher's Version

Both theory and experimental data from pathogens suggest that the production of transmission stages should be strongly associated with virulence, but the genetic bases of parasite transmission/virulence traits are poorly understood. The blood fluke Schistosoma mansoni shows extensive variation in numbers of cercariae larvae shed and in their virulence to infected snail hosts, consistent with expected trade-offs between parasite transmission and virulence. We crossed schistosomes from two populations that differ 8-fold in cercarial shedding and in their virulence to Biomphalaria glabrata snail hosts, and determined four-week cercarial shedding profiles in F0 parents, F1 parents and 376 F2 progeny from two independent crosses in inbred snails. Sequencing and linkage analysis revealed that cercarial production is polygenic and controlled by five QTLs (i.e. Quantitative Trait Loci). These QTLs act additively, explaining 28.56% of the phenotypic variation. These results demonstrate that the genetic architecture of key traits relevant to schistosome ecology can be dissected using classical linkage mapping approaches.