Eco-Evolutionary Dynamics symposium edition:7 location:Leuven date:5-7 February 2013
Schistosomiasis is a major, poverty-related disease affecting more than 200 million people in developing countries, 85% of them in sub-Saharan Africa. It has a complex epidemiology with a large variation in infection intensity, immune responses to infection, and schistosome-related pathology. Besides host-related factors, there are numerous parasite and environmental factors involved, which have so far been largely overlooked in epidemiology and control-oriented research.
To untangle the importance of these factors, knowledge about the influence of parasite genetics on host’s disease patterns is fundamental. We conducted a large epidemiological study in northern Senegal. We genotyped 1692 S. mansoni larvae collected from 45 human hosts with nine microsatellite loci and linked this with host data such as age, gender, infection intensity, liver and bladder morbidity. We found a positive relationship between schistosome infection intensity (measured as eggs per gram feces, epg), and the frequency of a certain parasite allele. We corrected for age, sex, and co-infection with S. haematobium. This trend is found with linear regression and redundancy analysis. Two other alleles in this locus were negatively correlated with epg. If we divide infection intensity by worm burden (measured by parasite antigen levels in the blood serum of patients) , we have a measure of parasite fecundity. This parameter appeared also positively correlated with the specific allele. This microsatellite locus is located in the untranslated region (UTR) of a protein kinase gene. Inhibiting this gene in adult schistosomes resulted in declined egg production by 30%, and reduced muscle contraction.
The possible link with parasite fecundity might explain the correlation between the respective microsatellite allele with infection intensity in humans. The next step is to sequence the complete UTR region and the coding sequence to search for functional SNPs.