Elsevier

Acta Tropica

Volume 86, Issues 2–3, May 2003, Pages 315-333
Acta Tropica

Review article
Could control of soil-transmitted helminthic infection influence the HIV/AIDS pandemic

https://doi.org/10.1016/S0001-706X(03)00063-9Get rights and content

Abstract

In May 2001, the World Health Assembly (WHA) estimated that two billion people were infected by soil-transmitted helminths (S-THs) and schistosomiasis, worldwide. The WHA urged member states to recognise that there can be synergy between public health control programmes for S-THs, schistosomiasis and other diseases. This is particularly relevant to the new dimension created by the HIV/AIDS epidemics in the same impoverished communities and countries where helminthiasis is hyperendemic. Immunological adaptation between humans and parasitic helminths has developed during evolution. Review of 109 research papers, 76% (83/109) of which, were published between 1995 and February 2002, revealed increasing evidence that this relationship may have created an opportunity for more rapid infection by the human immunodeficiency virus (HIV), as well as quicker progression to AIDS. Moreover, the efficacy of some vaccines against HIV is likely to be impaired by chronic helminthiasis. For this, there is strong, indirect evidence. There is an urgent need for parasitologists, epidemiologists, immunologists and virologists to undertake comprehensive, transdisciplinary research. On the other hand, there is no current evidence that immunosuppression by HIV facilitates helminthic infection. The situation in regard to strongyloidiasis, however, is not yet clear.

Introduction

Helminthiasis has been present throughout the evolution of humans, whereas HIV/AIDS is a new disease. Research on the potential for interaction between them is at an early stage. Endemicity of both diseases is enhanced by overcrowding and poverty (Markus and Fincham, 2000a). This reality exists in many countries and coincidentally increases the probability of interaction. It follows that, since the human immunodeficiency virus (HIV) causes immunosuppression, it is possible that soil-transmitted helminths (S-THs), which, are also called geohelminths, might be amongst opportunists that take advantage of hosts which, are compromised in this way. However, a more serious possibility is that of a reversed relationship. Is HIV the opportunist taking advantage of immunological host–parasite relationships that have stabilised as a result of evolution (Maizels et al., 1993, Maizels et al., 1999, Finkelman and Urban, 2001, Pritchard and Brown, 2001, Viney, 2002) and long before HIV/AIDS became a disease? This review summarises evidence for the possibility of opportunistic infection in both directions.

The gravity of the HIV/AIDS situation is illustrated by the fact that in South Africa, it has been estimated that the disease will kill between five and seven million adults between 15 and 40 years of age, by 2010 (Dorrington et al., 2001). In addition, large numbers of children are dying or being orphaned. The total population of South Africa is currently about 43 million people. In December 2001, UNAIDS estimated that 40 million individuals globally were living with HIV/AIDS and that 20 million had died of AIDS-related diseases (UNAIDS, 2001).

Section snippets

Literature review

The focus in this review is on infection of humans by those S-THs that are of public health importance in developing countries. They are Ascaris lumbricoides, the hookworms Necator americanus and Ancylostoma duodenale, Trichuris trichiura, and Strongyloides stercoralis. S. stercoralis is included because infection is related to conditions of poverty, overcrowding and lack of hygiene and sanitation (Roberts and Janovy, 2000). In such situations, the prevalence can exceed 50% (Mahmoud, 1996).

Discussion

The information summarised in Table 1, Table 2, Table 3, Table 4, Table 5, Table 6, Table 7, Table 8, Table 9, Table 10, Table 11, Table 12 indicates that the chronic immune response to helminthiasis could be adversely influencing the epidemics of HIV/AIDS and TB. Therefore, it is imperative to test the hypothesis that prevention and/or treatment of helminthic infections may improve the situation (Barouch and Letvin, 2001). Research should seek to define changes in the immune profile and plasma

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