Helminth infections: the great neglected tropical diseases

Alternatively activated macrophages (AAMPhi) are found in abundance during chronic Th2 inflammatory responses to metazoan parasites. Important roles for these macrophages are being defined, particularly in the context of Th2-mediated pathology and fibrosis. However, a full understanding of the requirements for alternative activation, particularly at the innate level, is lacking. We present evidence that alternative activation by the Th2 cytokines IL-4 and IL-13 is an innate and rapid response to tissue injury that takes place even in the absence of an infectious agent. This early response does not require CD4+ Th2 cells because it occurred in RAG-deficient mice. However, class II-restricted CD4+ T cell help is essential to maintain AAMPhi in response to infection, because AAMPhi were absent in RAG-deficient and MHC class II-deficient, but not B cell-deficient mice after chronic exposure to the nematode parasite, Brugia malayi. The absence of AAMPhi was associated with increased neutrophilia and reduced eosinophilia, suggesting that AAMPhi are involved in the clearance of neutrophils as well as the recruitment of eosinophils. Consistent with this hypothesis, AAMPhi show enhanced phagocytosis of apoptotic neutrophils, but not latex beads. Our data demonstrate that alternative activation by type 2 cytokines is an innate response to injury that can occur in the absence of an adaptive response. However, analogous to classical activation by microbial pathogens, Th2 cells are required for maintenance and full activation during the ongoing response to metazoan parasites.

The objective of the present study was to estimate the prevalence of soil-transmitted helminthiasis and evaluate the sanitary conditions and the role of a mass treatment campaign for control of these infections in Santa Isabel do Rio Negro. A cross-sectional survey was carried out in 2002, to obtain data related to the sanitary conditions of the population and fecal samples for parasitological examination in 308 individuals, followed by a mass treatment with albendazole or mebendazole with coverage of 83% of the city population in 2003. A new survey was carried out in 2004, involving 214 individuals, for comparison of the prevalences of intestinal parasitosis before and after the mass treatment. The prevalences of ascariasis, trichuriasis and hookworm infection were 48%; 27% and 21% respectively in 2002. There was a significant decrease for the frequency of infections by Ascaris lumbricoides (p < 0.05; OR / 95% CI = 0.44 / 0.30 - 0.65), Trichuris trichiura (p < 0.05; OR / 95% CI = 0.37 / 0.22 - 0.62), hookworm (p < 0.05; OR / 95% CI = 0.03 / 0.01 - 0.15) and helminth poliparasitism (p < 0.05; OR / 95% CI = 0.16 / 0.08 - 0.32). It was also noticed a decrease of prevalence of infection by Entamoeba histolytica / dispar (p < 0.05; OR / 95% CI = 0.30 / 0.19 - 0.49) and non-pathogenic amoebas. It was inferred that a mass treatment can contribute to the control of soil-transmitted helminthiasis as a practicable short-dated measure. However, governmental plans for public health, education and urban infrastructure are essential for the sustained reduction of prevalences of those infections.