Onchocerciasis in Guatemala a clinical and parasitological study with comparisons between the disease there and in East Africa

Abstract

A clinical and parasitological study has been carried out in Guatemala by observers who had carried out a similar study, using similar methods, at Amani, Tanzania. Some quite large differences were encountered in the frequency of various clinical, including ophthalmological, features in the two series. These differences included a greater frequency of iritis and keratitis, particularly severe sclerosing keratitis, but not of fundal lesions, in Guatemala and a lower frequency of skin lesions especially those of the legs. Mal morado, erisipela de la costa and leonine facies were encountered exclusively in Guatemala and occurred among the more heavily infected subjects. Differences were also encountered in the density and distribution of microfilariae in the body of Guatemalan and African subjects. Microfilarial densities in the legs were low in Guatemala and those in the upper part of the body proportionally higher, but even the heaviest loads in Guatemala were rather lighter than those encountered in East Africa, and differences were not sufficient to account for the differing frequency of clinical features. Differences in density and distribution of microfilariae do not wholly explain the different incidence and severity of these clinical and ophthalmic findings. In particular, similar parasite densities are associated with more keratitis and iritis in Guatemala than East Africa. This could result from the two strains of parasite being fundamentally different or from differing responses to similar parasite loads by Guatemalans compared with East Africans. In the Guatemalan series iritis and keratitis were associated with significantly higher parasite loads than in those free from ocular lesions. In endemic regions of Guatemala more people in early age groups were found to be infected than in East Africa. Density of microfilarial load was found in Guatemala as in East Africa not to increase significantly after the age of 20, suggesting the development of immunity or a change in habits with increasing age leading to limitation of the number of infective bites sustained.