Malaria of the orang-utan ( Pongo Pygmaeus ) in Borneo

Abstract

The primary objective of this project was to study the life cycle and ecology of Plasmodium pitheci, a malaria parasite of the orang-utan. The field work was based on the orang-utan rehabilitation centre in the Sepilok Forest Reserve of eastern Sabah. Two visits were made to Sepilok, the first in February and March, 1972, and the second (by W.P.) in January 1974. On the first visit two species of "surrogate host" were taken to Sabah, i.e. chimpanzees and Aotus monkeys for experimental work. The arboreal habitat of the orang-utan in the dipterocarp forests of eastern Sabah is described. In the Sepilok Forest Reserve dwell gibbons and leaf-monkeys, in addition to a small population of semi-domesticated and wild, free-ranging orang-utans of various ages. Although numerous species of anopheline mosquitoes have been collected in eastern Sabah, longitudinal studies are not available. Anopheles balabacensis was caught both attracted to orang-utans and to man at Sepilok. This species which is the main vector of human malaria in the north of Borneo, is suspected also of transmitting orang-utan malaria in this part of Sabah. Repeated blood examinations have been made on a number of orang-utans in the centre since 1966 and a high prevalence of infection was recorded with Plasmodium pitheci. In 1966 10 out of 19 animals had demonstrable parasitaemia. Detailed case histories are presented to show the course of parasitaemia in several orang-utans. Infections of P. pitheci were found to run a very chronic course. During the 1972 expedition a second, previously undescribed malaria parasite of the orang-utan was discovered, and was named P. silvaticum. The new parasite was successfully transmitted both by blood inoculation and, later, by sporozoite inoculation, into splenectomized chimpanzees. Although both species of malaria parasite may cause transitory signs of illness, orang-utans in general appear to be little discomforted by the infection. The animals do however suffer from other infectious diseases such as amoebic and balantidial dysentery, and melioidosis is a serious natural hazard which may have accounted for several deaths of wild orang-utans. An unidentified, intraerythrocytic structure that appeared in the blood of one chimpanzee, which had been inoculated with blood from an orang-utan, may have contributed to its death. Detailed descriptions and illustrations of P. pitheci and P. silvaticum are given. All stages of the life cycle of P. silvaticum are known (the tissue stages having been described in the liver of a "surrogate host", the chimpanzee) but only the blood and sporogonic stages of P. pitheci have been seen. This species was not infective to a chimpanzee, although there is an earlier report of a transient infection in this host by other workers. In the blood both parasites showed a tertian periodicity. From the appearance of the tissue schizonts on the seventh day it was estimated that the complete pre-erythrocytic cycle of P. silvaticum in the chimpanzee would occupy 8 days. P...

The evolution of primate malaria parasites based on the gene encoding cytochromebfrom the linear mitochondrial genome

“…This hypothesis was made based on the relative abundance of primate malaria parasites in Southeast Asia in comparison to Africa (19,45). We propose an African origin for the primate malaria parasites.…”

“…As far as the origin of primate malaria parasites is concerned, the commonly held opinion is that the primate malaria parasites originated in Southeast Asia, with the only exception being P. falciparum (45,46). This hypothesis was made based on the relative abundance of primate malaria parasites in Southeast Asia in comparison to Africa (19,45).…”

“…The anopheline vectors incriminated in monkey malaria transmission are in the Leucosphyrus group (20). This group has a broad host range that also includes humans and orangutans (45,47), suggesting that they may be responsible in malaria parasite host switches. The other aspect of the Asian primate malaria parasite radiation is the availability of several species of vertebrate host.…”

Prevalence and Etiology of Linear Enamel Hypoplasia in Monkeys and Apes from Asia and Africa

“…This explanation for the high prevalence of rLEH in great apes may be unsatisfactory because simian malaria is usually benign in its natural hosts [37]. For example, in an extensive report on malaria among orangutans of Sandakan, Peters et al [38] state that there is 'little evidence' that much morbidity in orangutans was caused by malaria (p. 450).…”

“…Hookworm infections are reported in feral populations of all apes (orangutans [38]; chimpanzees [44]; gorillas [45]). Of 18 chimpanzees imported from the Bukavu region of the Republic of Congo and examined after 4 months, 16 had hookworm identified as N. americanus [46].…”