Eco-epidemiology of gastrointestinal parasitic infections in captive chimpanzees in Gabon

Abstract

This study investigates the influence of abiotic variables (precipitation, soil surface temperature, and soil water content) and intrinsic factors (sex, age class, and social status) on the occurrence of gastrointestinal parasitic infections in two populations of chimpanzees (Pan troglodytes) in Gabon: one in captivity at the Primatology Center of CIRMF (n = 41) and the other in semi-captivity at Lékédi Park (n = 46). A total of 87 fecal samples were analyzed using flotation and sedimentation techniques. Fourteen gastrointestinal parasite taxa were identified, including two novel findings in chimpanzees: Fasciola hepatica and Toxocara sp. The overall prevalence was 85.4 % at the Primatology Center and 95.7 % at Lékédi Park. Binary logistic regression models revealed significant associations between intrinsic traits and parasite occurrence in captive individuals. Juveniles were at higher risk of Balantioides coli infection compared to adults (OR = 7.24; 90 % CI: 2.15-24.3; p = 0.047), while subordinate individuals were less likely to be infected than dominants (OR = 0.08; 90 % CI: 0.02-0.165; p = 0.007). Males were significantly more likely to be infected with strongylid nematodes (Strongylida fam. gen.) than females (OR = 6.58; 90 % CI: 1.90-22.7; p = 0.023). No significant associations were found between intrinsic factors and parasite occurrence in semi-captive individuals. Precipitation was significantly associated with increased infection risks in semi-captive chimpanzees, particularly for Balantioides coli, Entamoeba sp., Mammomonogamus sp., Strongyloides sp., and Trichuris sp. Conversely, in captive chimpanzees, precipitation was negatively associated with Entamoeba sp. and Strongylida fam. gen. Soil surface temperature was inversely correlated with the presence of Balantioides coli, Entamoeba sp., and Mammomonogamus sp. in the semi-captive group. No significant associations were detected between soil water content and parasite occurrence. A Spearman rank correlation analysis revealed a strong positive, though non-significant, relationship between parasite prevalence in soil samples and in captive chimpanzees (ρ = 0.82; p = 0.089).

Keywords: Abiotic variables; Chimpanzees; Conservation; Gabon; Gastrointestinal parasites.

Graphical abstract

Fig. 1

Localization of study site. (A): Map of Gabon with the Haut-Ogooué province highlighted. (B): Detailed view of the Haut-Ogooué province. (C): Aerial view of the Primatology Center of CIRMF. (D): Aerial view of Lékédi Park.

Fig. 2

Diversity of intestinal parasites identified in chimpanzees. Legend:Hymenolepis sp. (A); Spirurida fam. gen. (B); Trichuris sp. (C); Strongyloides sp. (D); Enterobius sp. (E); Ascaris sp. (F); Balantioides coli. (G); Mamomonogamus sp. (H); Strongylida fam. gen. (I, J, K); Fasciola hepatica. (L, M, N); Toxocara sp. (O); Troglodytella sp. (P); Entamoeba sp. (Q, R) Endolimax nana (S).

Fig. 3

Distribution diagram of intestinal parasites among chimpanzees from Parc de la Lékédi, the Primate Center, and the soil.

Fig. 4

Forest plots showing the effects of intrinsic factors on gastrointestinal parasite occurrence in captive and semi-captive chimpanzees. Forest plots showing the effect of intrinsic factors (sex, age class, social status) on the occurrence of gastrointestinal parasites in captive (A) and semi-captive (B) chimpanzees. Each point represents an odds ratio (OR) with its 90 % confidence interval (CI). Odds ratios greater than 1 indicate an increased likelihood of infection associated with the predictor, whereas odds ratios less than 1 indicate a reduced likelihood. Red points correspond to statistically significant associations (p < 0.05), and black points correspond to non-significant associations.

Fig. 5

Relationship between soil infestation and chimpanzees' infestation.