Invasive amebiasis in naturally infected New World and Old World monkeys with and without clinical disease
Beaver, P.C.; Blanchard, J.L.; Seibold, H.R.
American Journal of Tropical Medicine and Hygiene 39(4): 343-352
1988
ISSN/ISBN: 0002-9637 PMID: 2903689 Document Number: 310564
Histopathological preparations of caecum and colon from monkeys naturally infected with invasive Entamoeba histolytica were examined to determine the distribution of amoebae in the tissues and the types of lesions, if any, associated with them. Infections were studied in 3 New World species (10 Callicebus moloch, 1 C. torquatus, and 2 Aotus trivirgatus) and 3 Old World species (8 Macaca mulatta, 6 Erythrocebus patas, and 1 Cercopithecus aethiops). Amoebiasis was recorded as the principal or a contributing cause of death for all 13 New World monkeys and in 6 of the 15 Old World monkeys; amoebiasis was detected in the rest of the monkeys only after tissues were re-examined specifically for amoebae. Amoebae causing no apparent damage were found in the lamina propriae, mainly at the muscularis mucosae. Most frequent were colonies or aggregates of amoebae in the crypts between the epithelium and basement membrane, causing either no evident necrosis or changes ranging from necrosis and disarrangement of adjacent cells to complete destruction of the epithelium and reduction of the cells to pyknotic bodies. A lesion interpreted as possibly characteristic of carrier-state invasive amoebiasis was destruction of the epithelium in patches of mucosal crypts, not leading to ulceration. Uncommon but present in both New and Old World monkeys were typical areas of surface erosion and classical flask-shaped ulcers. The observations showed that in some Old World monkeys amoebiasis can be invasive without causing clinical disease. The authors studied histologically sections of caecum and colon obtained at necropsy from 13 New World monkeys (3 species) and 15 Old World monkeys (3 species) naturally infected with Entamoeba histolytica. Whereas amoebiasis was the principal or a contributing cause of death in all the New World monkeys, over half the Old World monkeys appeared to be healthy carriers of invasive amoebiasis. "A lesion interpreted as possibly characteristic of carrier-state invasive amebiasis was destruction of the epithelium in patches of mucosal crypts, not leading to ulceration." The observations support the view that Old World monkeys are more resistant than New World monkeys to development of clinical disease after E. histolytica infection. The former also appeared more resistant to infection, in that routine examination of tissue from 1265 primates of 32 species had revealed amoebic infection in 6.4% New World monkeys compared with only 2.2% of Old World monkeys.Carolyn A. Brown.