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This study is the first investigation on the endoparasite status of free
living eastern lowland gorillas. Reported are actual infection extensities of
parasites of gorilla groups in the Kahuzi-Biega National Park in Zaire.
Behaviour patterns influencing the epidemiology of parasites and the impact of
endoparasites on the clinical health of the gorillas are also investigated.
The results permit an assessment of the likely development of the parasite
status of gorilla populations in a situation where their habitats are
continuously decreasing and where proximity to human settlements increases.
This knowledge is necessary in order to establish measures for the
conservation of the endangered species well in advance of threatening
Faecal samples of 64 habituated gorillas of the Kahuzi-Biega National Park
were regularly investigated for over six months. Also, faecal samples of the
park personnel and their families were investigated twice.
The prevalence of helminths ranged between those of mountain- and western
lowland gorillas and showed a similar range of species. The eggs or larvae of
five nematodes and one cestode and two flagellates were identified in the
gorilla faeces. Most of the gorillas also excreted physiological
entodiniomorphs, which serve digestive functions.
Infection extensities increased with increasing age of the gorillas; this
pattern differed between different parasite species.
No signs of galactogenically transmitted helminths could be detected nor could
an influence of spatial ranging and the feeding behaviour of mothers on the
parasite status of their sucklings be established.
Lactating gorilla females excreted three of six of the parasite species and
all female gorillas two of the six species more frequently than male gorillas.
Differences between sexes and an effect of the female reproduction status were
apparent for the heteroxenous Anoplocephala gorillae and for "larvae" the
transmission way of the latter remains unknown.
Also, differences in extensities between climatic seasons as well as between
seasons of different food plants of the gorillas were marked for Anoplocephala
A negative correlation was established between the lengths of daily travels
between two consecutive nest sites and prevalences of parasites for four
investigated gorilla groups.
Gorilla groups whose ranging areas did overlap considerably excreted helminth
development stages more frequently than groups with a lower overlap. Higher
excretion rates also were observed for the two groups which were more
frequently visited by tourists when compared with groups with fewer contacts
As far as the identification of the helminth species was possible none of them
was shared between gorillas and man. Transmission potential from man to
gorillas of the shared potentially pathogenic protozoa Giardia lamblia though
could not be ruled out. All parasites identified in the stool samples of
people have been transmitted to gorillas or other non-human primates in
Three protozoa species identified in the gorillas and Enteromonas hominis for
free living gorillas are described for the first time.
Parasite infections in wildlife can result in reduced vitality and
reproduction success on the population level, even though no sign of disease
can be detected in individual animals. Behavioural traits that may reduce the
risk of infection with parasites for gorillas could be avoidance of old
nestsites for more than 54 days, the characteristics of nest building and the
predominant defecation behaviour, the covering of different dayjourney lengths
according to climate and vegetation seasons and the feeding on Guanea
The proportion of changes in the faeces structure was more elevated when
faeces contained eggs of Anoplocephala gorillae and "small" eggs. However, no
single case of general illness was detected in the population during the
entire period of investigation. This result points out that a balanced
relationship between the limited range of parasite species at medium infection
prevalence rates and the gorilla hosts still likely exists.
The results can be transferred, with some restrictions, to the endoparasite
situation of the eastern lowland gorillas in the Congo basin and to the highly
endangered mountain gorillas which live in similar biotopes.
This investigation should assist to design measures for the protection and
conservation of this so far under-investigated gorilla subspecies whose
survival is particularly threatened by the ongoing civil war in the area.
600 Technik, Medizin, angewandte Wissenschaften::630 Landwirtschaft::630 Landwirtschaft und verwandte Bereiche
Der Einfluß von individuellen, gruppenspezifischen und ökologischen Faktoren
auf den Endoparasitenstatus von wildlebenden östlichen Flachlandgorillas
(Gorilla gorilla graueri) im Kahuzi-Biega Nationalpark von Zaire. Ein
Univ.-Prof. Dr. Karl-Hans Zessin
PD Dr. R. Schuster
Individual, group specific and ecological influence factors on the status of
endoparasites of wild eastern lowland gorillas. A multidisciplinary approach.