A Comprehensive Genetic Analysis of Candidate Genes Regulating Response to Trypanosoma congolense Infection in Mice

About one-third of cattle in sub-Saharan Africa are at risk of contracting “Nagana”—a disease caused by Trypanosoma parasites similar to those that cause human “Sleeping Sickness.” Laboratory mice can also be infected by trypanosomes, and different mouse breeds show varying levels of susceptibility to infection, similar to what is seen between different breeds of cattle. Survival time after infection is controlled by the underlying genetics of the mouse breed, and previous studies have localised three genomic regions that regulate this trait. These three “Quantitative Trait Loci” (QTL), which have been called Tir1, Tir2 and Tir3 (for Trypanosoma Infection Response 1–3) are well defined, but nevertheless still contain over one thousand genes, any number of which may be influencing survival. This study has aimed to identify the specific differences associated with genes that are controlling mouse survival after T. congolense infection. We have applied a series of analyses to existing datasets, and combined them with novel sequencing, and other genetic data to create short lists of genes that share polymorphisms across susceptible mouse breeds, including two promising “candidate genes”: Pram1 at Tir1 and Cd244 at Tir3. These genes can now be tested to confirm their effect on response to trypanosome infection

Characterization of a composite with enhanced attraction to savannah tsetse flies from constituents or analogues of tsetse refractory waterbuck (Kobus defassa) body odor.

Savannah tsetse flies avoid flying toward tsetse fly-refractory waterbuck (Kobus defassa) mediated by a repellent blend of volatile compounds in their body odor comprised of δ-octalactone, geranyl acetone, phenols (guaiacol and carvacrol), and homologues of carboxylic acids (C5-C10) and 2-alkanones (C8-C13). However, although the blends of carboxylic acids and that of 2-alkanones contributed incrementally to the repellency of the waterbuck odor to savannah tsetse flies, some waterbuck constituents (particularly, nonanoic acid and 2-nonanone) showed significant attractive properties. In another study, increasing the ring size of δ-octalactone from six to seven membered ring changed the activity of the resulting molecule (ε-nonalactone) on the savannah tsetse flies from repellency to attraction. In the present study, we first compared the effect of blending ε-nonalactone, nonanoic acid and 2-nonanone in 1:1 binary and 1:1:1 ternary combination on responses of Glossina pallidipes and Glossina morsitans morsitans tsetse flies in a two-choice wind tunnel. The compounds showed clear synergistic effects in the blends, with the ternary blend demonstrating higher attraction than the binary blends and individual compounds. Our follow up laboratory comparisons of tsetse fly responses to ternary combinations with different relative proportions of the three components showed that the blend in 1:3:2 proportion was most attractive relative to fermented cow urine (FCU) to both tsetse species. In our field experiments at Shimba Hills game reserve in Kenya, where G. pallidipes are dominant, the pattern of tsetse catches we obtained with different proportions of the three compounds were similar to those we observed in the laboratory. Interestingly, the three-component blend in 1:3:2 proportion when released at optimized rate of 13.71mg/h was 235% more attractive to G. pallidipes than a combination of POCA (3-n-Propylphenol, 1-Octen-3-ol, 4-Cresol, and Acetone) and fermented cattle urine (FCU). This constitutes a novel finding with potential for downstream deployment in bait technologies for more effective control of G. pallidipes, G. m. morsitans, and perhaps other savannah tsetse fly species, in 'pull' and 'pull-push' tactics