Paradoxical associations between soil-transmitted helminths and Plasmodium falciparum infection

Abstract

Evidence on the comorbidity between soil-transmitted helminth infections and malaria is scarce and divergent. This study explored the interactions between soil-transmitted helminth infections and uncomplicated falciparum malaria in an endemic area of Colombia. A paired case-control study matched by sex, age and location in Tierralta, Cordoba, was done between January and September 2010. The incident cases were 68 patients with falciparum malaria and 178 asymptomatic controls. A questionnaire was used to gather information on sociodemographic variables. Additionally physical examinations were carried out, stool samples were analysed for intestinal parasites and blood samples for Ig E concentrations. We found associations between infection with hookworm (OR: 4.21; 95% CI: 1.68-11.31) and Ascaris lumbricoides (OR 0.43; 95% CI: 0.18-1.04) and the occurrence of falciparum malaria. The effects of soil-transmitted helminths on the occurrence of malaria were found to be paradoxical. While hookworm is a risk factor, A. lumbricoides has a protective effect. The findings suggest that, in addition to the comorbidity, the presence of common determinants of soil-transmitted helminth infections and malaria could also exist. While the biological mechanisms involved are not clear, public health policies aimed at the control of their common social and environmental determinants are suggested.

Helminth infection, fecundity, and age of first pregnancy in women

“…Helminths, such as hookworm ( Ancylostoma duodenale or Necator americanus ) and giant roundworm ( Ascaris lumbricoides ) infect upwards of 500–800 million people a piece (5), and are associated with such immunological changes: host helper T cell populations generally shift away from Th1 and towards Th2 responses (6, 7), and the suppressive activity of regulatory T cells increases, modulating both Th1 and Th2 responses (8, 9). These shifts can increase or decrease susceptibility to other pathogens, such as malaria (10), giardia (11), and tuberculosis (12), and are associated with reductions in many diseases with inflammatory or auto-immune etiology (13). They also resemble the shifts that occur during pregnancy, suggesting that helminth infections might result in immunological states that favor conception or pregnancy.…”

“…While A. lumbricoides is associated with a polarized Th2 response (6), the response to hookworm has been reported as a mixed Th1/Th2 response (26, 27). Hookworm and A. lumbricoides also have contradictory effects on other diseases, such as malaria (10). Thus the A. lumbricoides response may be more favorable to conception and implantation, as it more closely resembles the immunological state in pregnancy, and less closely resembles pro-inflammatory states that suppress fecundity.…”

Malaria and soil-transmitted intestinal helminth co-infection and its effect on anemia: a meta-analysis

“…Of the 30 studies, 12 assessed all three species of STH (A. lumbricoides, T. trichiura and hookworm) [8][9][10]26,28,32,[37][38][39][40][41]44 one assessed two species (A. lumbricoides and hookworm) 48 and two assessed two species (A. lumbricoides and T. trichiura).…”

Multimorbilidad: bases conceptuales, modelos epidemiológicos y retos de su medición

“…En este ensayo se hace énfasis en los adultos mayores, pues constituyen el grupo con mayor prevalencia de multimorbilidad (4), y porque la condición poco se ha estudiado en otras poblaciones como la infantil, cuyo estudio se ha centrado en condiciones derivadas de una sola enfermedad índice, como la obesidad infantil (15), o en la concurrencia de infecciones prevalentes en la infancia, como la 'poliparasitosis' (16), y su asociación con la anemia y la desnutrición (16) o, incluso, su relación paradójica con otros parásitos como el de la malaria (17). Solo algunos trabajos más recientes han abordado la multimorbilidad en la infancia desde múltiples dimensiones, al incorporar en estos perfiles los aspectos psicosociales, como se ha hecho, por ejemplo, en el estudio de los trastornos mentales de la infancia (18).…”