IL4 and Nematoda infectious disease: The specific objectives of our study were: (1) to identify promoter SNPs in the IL4 gene of the red-fronted lemur, (2) to associate both the respective IL4 SNP genotypes and a measure of individual heterozygosity with intensities of nematode infections, (3) to identify a possible functional role of the IL4 alleles in selective processes by exploring long-term fitness consequences between males of different genotype constitutions.