Seasonal Effects on Great Ape Health: A Case Study of Wild Chimpanzees and Western Gorillas

<div><p>Among factors affecting animal health, environmental influences may directly or indirectly impact host nutritional condition, fecundity, and their degree of parasitism. Our closest relatives, the great apes, are all endangered and particularly sensitive to infectious diseases. Both chimpanzees and western gorillas experience large seasonal variations in fruit availability but only western gorillas accordingly show large changes in their degree of frugivory. The aim of this study is to investigate and compare factors affecting health (through records of clinical signs, urine, and faecal samples) of habituated wild ape populations: a community (N = 46 individuals) of chimpanzees (<em>Pan troglodytes</em>) in Kanyawara, Kibale National Park (Uganda), and a western gorilla (<em>G. gorilla</em>) group (N = 13) in Bai Hokou in the Dzanga-Ndoki National Park (Central African Republic). Ape health monitoring was carried out in the wet and dry seasons (chimpanzees: July–December 2006; gorillas: April–July 2008 and December 2008–February 2009). Compared to chimpanzees, western gorillas were shown to have marginally greater parasite diversity, higher prevalence and intensity of both parasite and urine infections, and lower occurrence of diarrhea and wounds. Parasite infections (prevalence and load), but not abnormal urine parameters, were significantly higher during the dry season of the study period for western gorillas, who thus appeared more affected by the large temporal changes in the environment in comparison to chimpanzees. Infant gorillas were the most susceptible among all the age/sex classes (of both apes) having much more intense infections and urine blood concentrations, again during the dry season. Long term studies are needed to confirm the influence of seasonal factors on health and parasitism of these great apes. However, this study suggest climate change and forest fragmentation leading to potentially larger seasonal fluctuations of the environment may affect patterns of ape parasitism and further exacerbate health impacts on great ape populations that live in highly seasonal habitats.</p> </div

Comparative summary of average concentration and statistics for selected urine variables for chimpanzees and western gorillas.

<p>In parenthesis the range of maximum and minimum values recorded. Columns named “Anova” show ANOVA's results of the three different factors tested: species, season and age/sex class. See text for details on statistical method.</p

Seasonal subdivision of the study period and biological sample sizes.

<p>In parenthesis: minimum and maximum values.</p

Summary of general body conditions and clinical signs.

<p>Percentage of days with at least one individual with each symptom for chimpanzees (N = 132 days) and gorillas (N = 188 days). <i>Wounds</i> consisted of bites or cuts caused by falls from trees, intra and inter (only for gorillas, but caused by vegetation) group aggressive interactions. <i>Skin lesions</i> consisted in itchy white spots (sometimes with little crusts) on body and face of all group members, possibly produced by either a fungus or ringworms. <i>Worms in faeces</i>, in chimpanzees two <i>Bertiella</i> sp segments associated with whole leaves of <i>Aneilema aecquinoctiale</i>. <i>Diarrhoea</i>, in gorillas 2 cases caused by stress related during inter-group interactions, one severe case from a 2 year-old infant lasting two days, mild diarrhoea during dry season (N = 9). Asterisks indicate a different sample size for chimpanzees: *N = 127, ** N = 125.</p

Summary of coproscopy (a–b) and macroscopic results (c) for both chimpanzees and western gorillas.

*<p>Feces either from a adult female or male, or a subadult of the Makumba group</p><p>Given the uncertainty of juvenile and infant sex in gorillas, only the average value for all individuals per each of these two classes is provided for western gorillas. Strongyl large eggs: (50×90 µ) on average, more round and fringes than the small strongyl eggs (40×80 µ) and <i>Strongyloides fullebornii</i>.</p

Averages per time period of strongyle load (a) in chimpanzees and (b) in western gorillas.

<p>The grey area distinguishes the months of dry season in comparison to months of wet season.</p

Average strongyle load across populations and age/sex classes.

<p>Vertical bars denote 0.95 confidence intervals.</p

Restriction enzyme digestion of DNA sequences amplified with Civ18S1500F and Nem5.8R.

<p>By digestion with <i>Alu</i> I, two bands were formed for type I in area from 200 to 500 bp, while only one band was formed for types II and III. By digestion using <i>Hinc</i> II, two bands of about 300 and 500 bp were formed for type I, while only one band similar to original band was visible for types II and III.</p

Comparison of ITS-2 sequences of hookworms from apes and humans from Dzanga Sangha Protected Areas.

<p>Host and accession number in DNA database are given in parentheses. Dots indicate homologous nucleotides with <i>N. americanus</i> (<i>N. a.</i>) from Guatemala (AF217891); dash indicates absence of nucleotide. Major indels are shaded.</p

Comparison of ITS-1 sequences of hookworms from apes and humans from Dzanga Sangha Protected Areas.

<p>Host and accession number in DNA database are given in parentheses. Dots indicate homologous nucleotides with <i>N. americanus</i> (<i>N. a.</i>) from Guatemala (AF217891); dash indicates absence of nucleotide. Major indels are shaded.</p