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[NEW YORK] A team of ecologists has shed light on why anti-hookworm treatment may result in a worsening of malaria in patients simultaneously infected with the different parasites responsible for these two infestations.

Sarah Budischak, post-doctoral fellow, and others at the Princeton University, examined data from an earlier Indonesian study of 4,000 patients carrying both malaria and hookworm parasites. They concluded that the two pathogens compete for a common food source — red blood cells in the host’s internal ecosystem. 

Although deworming may provide net health benefits to human populations, the Princeton study, published last month (February) in the journal Ecology Letters, suggests that it has the potential to exacerbate the severity of some malaria infections.  

“Our study suggested that hookworms could reduce the intensity of malaria caused by the Plasmodium vivax parasite two- to three-fold”

Sarah Budischak, Princeton University

“We focused on individuals who had both infections (malaria and hookworms) and paired this with experimental data where individuals were dewormed and asked if that affected the intensity of malaria infections,” explains Budischak, lead author of the report. “Our study suggested that hookworms could reduce the intensity of malaria caused by the Plasmodium vivax parasite two- to three-fold.” 

However, while bloodsucking hookworms outcompete P. vivax, another species of the malaria parasite, P. falciparum, outcompetes hookworms, especially in individuals given anti-hookworm treatment. The difference in response to deworming, according to Budischak, is a function of P. falciparum being a more voracious eater of red blood cells than P. vivax. Jessie Abbate, post-doctoral researcher at the Institut de Recherche pour le Developpement (IRD), Montpellier, France, believes that the research is valuable because it shows that hookworms and the Plasmodium species do interact within humans, notably through "bottom-up" resource (red blood cell) competition.

Many of the earlier studies, she stresses, “lumped together all ‘intestinal worms’ or all ‘malaria parasites,’ missing the very specific interactions that each species — with its nuanced nutritional needs and immune signals — brings into the pathogen community.”

Abbate believes that the findings may directly impact disease control decisions such as large-scale de-worming campaigns in co-endemic regions, especially in the developing world. “Treatment options could be modified with this new understanding, but not immediately,” she says.  

Budischak recommends that “in areas where malaria, particularly P. vivax is common and where resources permit, individuals should be tested and treated for malaria before given routine deworming medications. Otherwise, the deworming may exacerbate the malaria infection”.

“Since removing hookworms could lead to more severe malaria infections, it may also be helpful to increase malaria prevention efforts following routine deworming programs,” she adds.
This piece was produced by SciDev.Net’s Asia & Pacific desk.

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