Plasmodium spp

Charpentier, M. J. E., Boundenga, L., Beaulieu, M., Dibakou, S. E., Arnathau, C., Sidobre, C., Willaume, E., Mercier-Delarue, S., Simon, F., Rougeron, V. & Prugnolle, F., 2019, A longitudinal molecular study of the ecology of malaria infections in freeranging mandrills, International Journal for Parasitology: Parasites and Wildlife 10, pp. 241-251 : 245-246

3.1. Determinants of plasmodium spp . infections

3.1.1. Intrinsic host characteristics and seasonality

We found that individual sex significantly ( P. gonderi ) or marginally ( P. mandrilli ) influenced occurrences ( Table 1): the probability of infection was higher in males ( P. mandrilli and P. gonderi resp.: 40.5% and 44.1%, N = 111) than in females (32.7% and 37.9%, N = 104). In addition, the quadratic form of individual age significantly impacted the probability of both infections ( Table 1). The age distribution of infected individuals ( P. mandrilli ) followed the age distribution of all sampled individuals, irrespective of their infection status. By contrast, the highest probability of infection for P. gonderi was around 13 yrs of age ( Fig. 2 ). Neither female's reproductive status nor the ecological season of sampling had significant effects on occurrences, while parasitaemia were not impacted by any of the studied ecological or individual determinants ( Table 1).

3.1.2. Co-infection patterns

The probability of being infected by one Plasmodium species was slightly higher when already infected by the other species (36.7% of individuals non-infected by P. mandrilli were infected by P. gonderi while 48.7% of individuals infected by P. mandrilli were also infected by P. gonderi ). The correlation between occurrences was, however, not significant, although close to be (Spearman's rank correlation: N = 214, rs = 0.12, P = 0.09). Parasitaemia appeared non-significantly correlated (N = 214, rs = 0.09, P = 0.21; without outliers: N = 206, rs = 0.07, P = 0.34).

In males aged ≥6 yrs, occurrences were not influenced by retroviral infections ( Table 2). By contrast, P. gonderi parasitaemia was related to SIV infection: males in primo-infection were more heavily parasitized than any other males ( Fig. 3 ) and this effect was not due to confounding effect of the identity of the studied males ( Table 2).

F and P values of full linear models are presented with significant P-values in bold. GLMM were used for occurrences while either non-parametric analyses of variance ( P. mandrilli ) or GLM ( P. gonderi ) were used to study parasitaemia.

gonderi ) on skin temperatures, in collared adult mandrills.

F and P values of full multivariate analyses of variance are presented with significant P-values of interest in bold. “ids”: individuals.

Figures

Fig. 2. Kernel density estimates for the distribution of ages across all studied individuals (dashed green line) and those infected by P. mandrilli (solid blue line) and P. gonderi (dashed red line). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 3. P. gonderi parasitaemia across male mandrills with different SIV statuses. SIV-: SIV-negative males; SIV+: SIV-positive males; PI: males in primo-infection. Means and standard errors of the mean calculated from raw values are represented. P-values were obtained using differences of least squares means across the three categories (LMM).