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HIV infection and parasitic diseases in tropical areas |
Cahiers d'études et de recherches francophones / Santé . Volume 1, Number 3, 189-201, Août-Septembre 1991, Synthèse
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 Résumé
Article gratuit
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Author(s) : Francisco Veas, Jean-Loup Rey |
Summary : The epidemiology of HIV infection in Africa shows several specific features. In addition to the fact that transmission is almost exclusively between heterosexuals, the efficiency of contamination appears to be higher than in northern countries. One of the peculiar characteristics of HIV infection in tropical countries, particularly in Africa, is its association with multiple microbial infections (parasites, fungi, bacteria and viruses). Such associations can be of three main types: a reciprocally favourable influence due to the induction of an overall non-specific immunodeficiency, a specific intracellular interaction (in case of co-infection of the same cell), and cell-to-cell interactions mediated by various cytokines and possibly compounded by iatrogenic factors.
The first candidate parasitic disease is malaria, but neither transversal nor retrospective studies conducted in 1986 showed any link with HIV sero-positivity. Nevertheless, longitudinal studies are called for, since numerous clinicians stress the larger number of severe cases in adults living in endemic areas. Unfortunately, it will be difficult to distinguish between the effect of HIV infection and the influence of chloroquine resistance which is following the same spatial and chronological expansion as the viral disease. A possible relationship between HIV infection and chloroquine resistance should be investigated. The second most frequent parasitosis is schistosomiasis\; no data concerning a possible epidemiological relationship with HIV are available, but several laboratory studies have shown that elements of the viral genome can be carried by Schistosoma. Epidemiological investigations are urgently required before the preferential zones of expansion coalesce (rural areas for Schistosoma, urban areas for HIV). With regard to the other blood parasites, the data are homogenous for Leishmania, but controversial for Trypanosoma. In the Mediterranean countries and in South America, Leishmaniasis is increasingly seen as an opportunistic infection in HIV-infected subjects, with an aggravation of both pathologies. Co-infection in vitro leads to reciprocal facilitation and severe immunologic disorders. Our knowledge of African trypanosomiases is still fragmentary. Transversal studies have shown no link between HIV seropositivity and the presence of Trypanosoma spp. in the blood, but the role of the virus in the bacterial disease has not been studied and anomalies exist in the results of serological tests. Our understanding of the relationship between HIV infection and intestinal and genital protozoal diseases is progressing rapidly. Several laboratory studies have shown that these organisms can favour viral replication and carry elements of the viral genome. Such a phenomenon could help to explain the high efficiency of HIV transmission between heterosexuals in Africa. The consequences of these relationships are reviewed. On the one hand, HIV could favour the development of the parasitoses by facilitating infection, accelerating the development of the disease, aggravating the clinical course and reducing the efficacy of the drugs commonly used. On the other hand, parasitoses could favour the development of HIV disease by facilitating both contamination and clinical expression. It is, however, possible that in some circumstances the opposite may occur. In conclusion, a knowledge of these interactions is necessary to understand the pathogenicity and epidemiology of HIV with a view to developing programmes aimed at limiting both AIDS and parasitic diseases. |
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