by Peter Hotez and Remko van Leeuwen
New published information reveals that intestinal worm infections rank among the most common afflictions of people living in extreme poverty. The numbers are quite astonishing. More than 800 million people are currently believed to harbor Ascaris roundworms in their gastrointestinal tract, while around 450 million people are infected with either hookworms or Trichuris whipworms. Frequently a single individual, especially a child, is simultaneously infected with two or three of these types of intestinal worms at the same time, so that the term "unholy trinity" has been used to describe them.
The new numbers suggest that almost every person living in a developing country is infected with worms, a consequence of the fact that the infective egg or larval stages of these parasites are practically ubiquitous in the soil.
Each type of worm brings its own little shop of horrors, with severe health consequences for growing children and, in the case of hookworms, also for pregnant women.
Ascaris roundworms can obstruct the intestinal tract and cause an acute surgical crisis for a young child. Moreover, after swallowing Ascaris eggs, the hatched larvae migrate into the lungs to cause asthma. As a result, Ascaris is a major cause of asthma in poor countries.
Trichuris whipworms cause colitis and may represent the world's most common cause of inflammatory bowel disease.
Hookworms cause intestinal blood loss, so that they are a leading cause of anemia in the developing world. Long-standing anemia in children produces cognitive and intellectual deficits that reduce their future economic potential, while hookworm anemia in pregnancy increases the risk of death for the mother and survival of her newborn baby.
Recently, the Global Burden of Disease Study that evaluated almost all disease conditions for the year 2010 determined that the intestinal worms cause as much or more global disability than better known childhood conditions such as autism, ADHD, or cleft-lip and palate. Hookworms accounted for more than two-thirds of that disability.
Today, the World Health Organization (WHO) together with other international agencies is leading global efforts at 'deworming,' i.e., mass drug administration of a single pill of either albendazole or mebendazole These medicines are being donated free-of-charge by GSK and J&J, respectively. In parallel, clean water and sanitation are also important stalwarts into worm control.
Global deworming is funded by USAID and UKAID, as well as some major non-governmental organizations, such as Deworm the World, the END Fund, and the Partnership for Child Development. The Global Network for Neglected Tropical Diseases is providing key advocacy both in the US and Europe, as well as in some highly endemic countries including India, where the Bollywood star Abhishek Bachchan has become an important celebrity ambassador for worm diseases.
There is a lot of work to do. While annual deworming can improve the health and well-being of children, the WHO estimates more than 850 million children today require this treatment, making it one of the world's largest global public health programs. So far less than 40 percent of the world's children who could benefit from deworming actually receive the medicines. Therefore global deworming needs to continue to scale-up and expand.
Additional information indicates that deworming works well for Ascaris roundworm infection but not for hookworm or Trichuris whipworm infection. Moreover in areas of high transmission children can become quickly reinfected with worms. Therefore we also need research into better drugs and vaccines, especially for hookworm, which is responsible for most of the disability. With EU support and in collaboration with a consortium of European/US/African organizations known as HOOKVAC, we are developing the first human hookworm vaccine now in clinical trials in Brazil and soon to enter clinical testing in Gabon. We are also pursuing the possibility of a vaccine that could target all of the intestinal worms.
A world free of worms would be one in which children achieve their full physical, intellectual, and economic potential. It would ensure a generation of mothers can deliver healthy children in developing countries. Through expanded deworming and R&D into improved drugs and vaccines, that dream could become a reality.
Peter Hotez is President of the Sabin Vaccine Institute, Texas Children's Hospital Endowed Chair in Tropical Pediatrics, and Dean of the National School of Tropical Medicine at Baylor College of Medicine.
Remko van Leeuwen is the Project Director of the EU-supported HOOKVAC Consortium.