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PLOS BLOGS Speaking of Medicine

Highlighting notable helminth research and a PLOS Science Weds AMA preview for #WormWeek

Update 8/17/16: read the PLOS Science Weds discussion on this topic

To many people, worms are considered harmless creatures, if not a little yucky. But don’t be fooled by their small and innocuous size, some worms are parasitic, and are the cause of substantial disability for billions of people worldwide.

Helminths, the technical name for parasitic worms, can cause a specific type of infection that leads to diseases primarily impacting poor individuals living in lower- and middle-income countries (LMICs). Some of these diseases you may have heard of, with hookworm, dracunculiasis (guinea worm), onchoceriasis (river blindness), and schistosomiasis being among the most well-known.

In an effort to raise awareness about the far-reaching impacts of worms (including non-parasitic worms), NPR Goats and Soda has published a series of articles as part of NPR #WormWeek, including a profile on Dr. Peter Hotez, the editor-in-chief of PLOS Neglected Tropical Diseases (NTDS).

To maintain the momentum Worm Week has generated around helminths, this week’s PLOS Science Wednesday “Ask Me Anything” session will be on a recent PLOS NTDs article assessing the effectiveness of global schistosomiasis control efforts. Ask authors Susanne Sokolow and Michael Hsieh your worm questions on Wednesday August 17 at 1pm EST on redditscience. A direct link to the AMA will be tweeted from @PLOS the morning of the AMA.

In a Q&A with Social Media Associate Sara Kassabian, Hotez shares what he feels is some of the most important research that has helped advance efforts to control and eliminate helminth infections and answered some questions about global health priorities. This Q&A has been lightly edited for clarity.

What are the top five most important studies about helminths published in NTDs? And why are they important?

  1. The Case for Mass Treatment of Intestinal Helminths in Endemic Areas. In this 2015 opinion piece, Hicks et. al are “really talking about why treatment is so important in terms of the impact on improving education,” Hotez says.
  2. Helminth Elimination in the Pursuit of Sustainable Development Goals: A “Worm Index” for Human Development. In this editorial, which received a fair bit of press attention, Hotez and Herricks write about the “inverse association between worms and human development indices.”
  3. Blood Drain: Soil-Transmitted Helminths and Anemia in Pregnant Women. The associations between helminth infection and blood loss during pregnancy are examined in this viewpoint.
  4. Sustaining Progress towards NTD Elimination: An Opportunity to Leverage Lymphatic Filariasis Elimination Programs to Interrupt Transmission of Soil-Transmitted Helminths. In this paper, Walson and colleagues share the evidence that supports combining therapies for helminth elimination.
  5. Impact of Helminth Infection during Pregnancy on Cognitive and Motor Functions of One-Year-Old Children. The results of this study by Mireku et al. show that helminth infection during pregnancy is associated with impaired cognitive and motor function in infants.
  6. Potential Cost-Effectiveness of Schistosomiasis Treatment for Reducing HIV Transmission in Africa – The Case of Zimbabwean Women. Schistosomiasis infection is associated with increased risk of HIV/AIDS infection. In this study, Mbah and colleagues show mass praziquantel administration is a cost-effective way to reduce the burden of schistosomiasis and HIV infections in sub-Saharan Africa.
  7. Opisthorchiasis: An Overlooked Danger. Opisthorchiasis, a worm-borne disease contracted by ingesting raw fish, can lead to cholangiocarcinoma, a bile-duct cancer. The TOPIC Consortium wrote a policy piece for PLOS NTDs to advance a platform for this disease.

Do you foresee a future where the global health community truly begins to prioritize elimination efforts around helminths?

11 year old boy with ascites and portal hypertension due to schistosomiasis. Photo by NTDs Study Group, Univ of the Philippines Manila. Dr Vicente Y. Belizario, Jr. via Flickr.
11 year old boy with ascites and portal hypertension due to schistosomiasis. Photo by NTDs Study Group, Univ of the Philippines Manila; Dr Vicente Y. Belizario, Jr. via Flickr.

I think one of the big issues is that they often are not considered killer diseases. Worms cause enormous morbidity and disability but they also cause deaths. For example, a lot of the renal failure and liver disease that is caused by schistosomiasis is not attributed to schistosomiasis. Some estimates indicate that 280,000 people die annually from schistosomiasis, mostly renal and hepatic failure, but those deaths are placed in the non-communicable disease category. Similarly, a large percentage of anemia deaths (180,000 annually) are not appropriately attributed to hookworm. Appropriately attributing deaths and disease burden is important.

Also, there is a lack of understanding as to the reasons why worms actually promote poverty and educational deficits, because they also shave IQ points off of kids. Worms represent the leading factors that trap people in poverty and prevent kids from learning, while preventing otherwise productive individuals from going to work. Many also don’t really understand the comorbidities between worms and cancer, and worms and AIDS. For example opisthorchiasis and clonorchiasis represent leading causes of bile duct cancer, while schistosomiasis may be one Africa’s most important cofactor in their AIDS epidemic due to female genital schistosomiasis (FGS). There was practically no mention of FGS in the recent international AIDS conference in South Africa.

What about R&D?

I’m also concerned about the lack of investment in R&D for helminth . For AIDS and malaria, it’s understood that we’re going to invest in multiple modalities such as vaccines, diagnostics, and drugs. But for worm diseases, we only get a one shot on goal. We can only do deworming vs vaccines, but not both – we need to get around that. If you look at the global R&D dollars spent on worms, it’s a tiny fraction of big three diseases – AIDS, TB, and malaria, not to mention non-communicable diseases.

To learn more, read the review by Hotez et al. synthesizing the evidence for which control strategies and new technologies we will need to eliminate NTDs.

Don’t forget to join us on PLOS Science Wednesday!

Come prepared with your #WormWeek questions on this Wednesday’s PLOS NTDs Science Wednesday AMA on schistosomiasis. Prepare by reading the featured article in advance of the chat on Wed August 17, live at 1pm ET.

Featured Image: A photo of the NTD Control Programme Office in Freetown. Photo credit: Romina Rodríguez Pose via Flickr.

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