Social status and helminth infections in female forest guenons (Cercopithecus mitis).

OBJECTIVE: When resource competition within primate social groups is effective, high-ranking individuals generally gain fitness benefits. Contrary to expectations, female Cercopithecus mitis form linear dominance hierarchies without evidence for rank-related variation in fitness-relevant measures, raising questions about the evolution of guenon social structure. Here, we test whether social status predicts gastrointestinal helminth infections, known to influence health and morbidity in other mammalian hosts. In addition, we assess whether infections contribute to stress responses as indicated by fecal glucocorticoid (fGC) levels. METHODS: We quantified infections and hormone levels in 382 fecal samples from 11 adult female Sykes' monkeys (C. m. albogularis) over four months in one wild study group at Gede Ruins, Kenya. Using a generalized estimating equations technique, we modeled the odds of infection, relative infection intensity, and fGC variation. RESULTS: High-ranking females were less likely infected with Trichuris and Trichostrongylus, had lower fecal egg counts for both taxa, and overall lower helminth richness than low-ranking females. An inverse relationship between rank and Trichuris egg counts existed also in a study population of blue monkeys (C. m. stuhlmanni), where we collected comparable data over a shorter period. Regardless of rank, lactating females were more likely than non-lactating females to be infected with Trichuris, and had higher fecal egg counts for both Trichuris and Oesophagostomum. Lastly, we report evidence that Trichuris infections exacerbated energetic stress and that food supplementation by tourists increased infection levels. CONCLUSION: Our findings suggest that high-rank may provide long-term health and energetic benefits for female C. mitis, with potential fitness implications.

The effect of vaccinating S. mansoni-infected BALB/c mice either before or after treatment.

In Schistosoma mansoni endemic areas, there are people with ongoing S. mansoni infection, others have been infected and treated while others have never been infected. What would happen if these different groups of people were vaccinated against S. mansoni? BALB / c mice were divided into five groups: Infected-Treated-Vaccinated; Infected-Vaccinated-Treated; Vaccinated-Treated Control; Challenge Control and Untreated Challenge Control. Vaccination (500 20krad irradiated S. mansoni cercariae), Treatment (praziquantel), Infection and Challenge (150 S. mansoni cercariae) were carried out at specified times. Proliferation assay, Enzyme linked immunosorbent assay, gross pathology, histopathology and perfusion were performed. High protection levels were obtained in mice treated after vaccination: Vaccinated-Treated control, 96.5 %; Infected-Vaccinated-Treated, 68.9 %; and Infected-Treated-Vaccinated, 41 %. A good correlation was obtained between proliferative responses and protective levels, implying cellular involvement in protection. Although all protected animals had high IgG levels, there was no strong correlation between the two. Specificity rather than amounts of IgG, seem more important in protection. Praziquantel seemed to boost protective immunity when administered after vaccination. Granuloma development and modulation in the two test groups was similar. It seems better to vaccinate infected patients before treatment, the ideal situation being vaccinating people who have not encountered S. mansoni.

Influence of age of mice on the susceptibility to murine schistosomiasis infection.

Intensity of human schistosomiasis infection increases with age, a peak being attained at early puberty. Hormones could be involved in the age-related changes in susceptibility to schistosomiasis. Male BALB / c mice were infected with Schistosoma mansoni either before or after puberty and worm numbers, cellular immune responses, hormonal levels and pathology analysed. Pre-puberty infected mice had a significantly higher number of adult worms (p < 0.05), more severe granulomas, higher mortality rate and higher proliferative responses as compared to post-puberty infected mice. Levels of the hormones were lower in the pre-puberty infected mice as compared to the post-puberty group early in the infection. Plasma levels of testosterone and luteinizing hormones decreased significantly (p < 0.05) in infected mice when compared to controls. Susceptibility to S. mansoni in male BALB / c mice seems to be influenced by levels of testosterone and luteinizing hormone at infection. Albeit, an infection with S. mansoni seems to lower the hormonal levels.