A detailed molecular analysis in LF chickens revealed the presence of a tandem duplication of 176,324 bp of the partially duplicated prolactin receptor (dPRLR) and sperm flagellar 2 genes (dSPEF2) which could be a candidate gene for the LF phenotype (Elferink et al., 2008; Bu et al., 2013). Here, PRLR is linked to Lassa fever.