Soil-Transmitted Helminths (Intestinal Worms)
“Helminth” is a technical word for a type of worm. There are three species of soil-transmitted helminths (STH) that are important in terms of public health: roundworms (Ascaris lumbricoides), whipworms (Trichuris trichuria) or hookworms (Ancylostoma duodenale and Necator americanus). STH are also known simply as a common intestinal worm.
Globally, up to 1.2 billion people, of which, a third are children, are infected or at-risk of being infected with STH. The populations most at risk of infection are those living in the poorest areas of tropical and sub-tropical countries of the world, where the humidity, warm soil, and inadequate sanitation support the lifecycle of the helminth and thus, facilitate transmission.
STH infections are spread through eating food that has been contaminated by eggs in an infected person’s feces or by larvae, through penetration of the skin, particularly the feet, if shoes are not worn.
There are three critical health interventions that need to be implemented to achieve comprehensive and sustainable STH control:
- Deworming with broad-spectrum anthelminthic drugs, such as mebendazole, at appropriate intervals for a prescribed length of time to kill and prevent transmission of the worms
- Health education to promote personal and environmental hygiene to reduce the risk of re-infection in treated individuals and to prevent new infections
- Improved sanitation such as access to clean water for hand washing and safe and sanitary latrines to keep infected human excreta from the areas where people live, work and play
Mebendazole is one of a class of medicines known as anthelminthics that are used to treat numerous worm infections (roundworm, hookworm, pinworm, whipworm and threadworm). Mebendazole prevents the worm from absorbing glucose (sugar), causing it to lose energy and eventually die. The drug has been proven safe and effective and is on the WHO list of Essential Medicines. Side effects may include stomach pain or upset; diarrhea; nausea; dizziness; hair loss; headache, fever; skin rash or itching; sore throat and fever; or unusual tiredness and weakness.
Mebendazole is approved for the mass treatment of STH infections in adults and children who are at least 12 months old.
About Children Without Worms
The vision of Children Without Worms is to free all the world’s children of intestinal worms so they can grow, play, learn and enrich their communities. Our mission is fourfold:
- To reduce and control the global burden of childhood STH infections through equitable access to mebendazole
- To be a catalyst for development of effective strategies to treat, control and prevent STH infections in order to enhance health and education
- To assist communities to achieve sustainable control of STH infections
- To mobilize multisectoral coalitions of partners at global, national and local levels for STH control
The objective of Children Without Worms is to promote comprehensive and sustainable STH control strategies by:
- Reducing the heavy worm burden and its associated morbidities, enhancing education and promoting child development
- Establishing a policy that combines mass treatment with the promotion of health behavior change
- Promoting effective partnerships for STH control
The program envisions an ultimate shift in emphasis from regular mass deworming to provision of hygiene education and increased sanitation to reduce transmission and eliminate the need for perpetual treatment.
Children Without Worms leverages the donation of mebendazole from Johnson & Johnson to promote comprehensive and sustainable control of STH that entails:
- Regular mass deworming of at-risk groups
- Hygiene education
- Environmental sanitation
Children Without Worms leverages the donation by:
- donating mebendazole to national STH control programs that combine treatment (i.e., regular mass deworming) with prevention (i.e., hygiene education and environmental sanitation);
- advocating and fundraising for resources to promote hygiene education and access to water and improved sanitation facilities; and 3) partnering with organizations already working in hygiene education and sanitation to ensure that donated mebendazole is distributed in a context that maximizes positive impact.
This disease impacts children hardest because it occurs at a critical period during their physical and intellectual development. Infection can cause anemia, malnutrition, increased susceptibility to other serious infections, and stunted growth. If children are not treated, the disease may lead to impaired cognitive development, reduced school attendance and performance, and ultimately, decreased productivity as adults. In severe cases, the disease can lead to death.
Children Without Worms, together with the Mebendazole Advisory Committee, partner UN agencies, and the governments of countries receiving donated mebendazole, is implementing a monitoring and evaluation plan to assess the progress and impact of the donation. This evaluation will include all aspects of the three-prong approach (i.e., regular mass deworming, hygiene education, and environmental sanitation). Lessons learned from monitoring and evaluation activities will ensure continuous improvement of the program.
Comprehensive and sustainable STH control can only be assured by promoting interventions in health and hygiene education and improved sanitation. The program leverages the donation of mebendazole to galvanize partnerships with governments, nongovernmental organizations, international development agencies, foundations and other corporations with expertise in those areas to complement the delivery of the drug.
Children Without Worms partners with governments of STH-endemic countries, nongovernmental organizations, the World Health Organization (WHO), the World Food Program (WFP) and the United Nations Children’s Fund (UNICEF). Children Without Worms also works to promote partnerships at the national and international levels to control STH infections.
The program is one of several based at The Task Force for Child Survival and Development, which is a nonprofit organization working since 1984 to improve health and human development around the world. It has a legacy of creating successful partnerships that address international and domestic health problems. The Task Force works with leaders and organizations to advance public health by creating coalitions, reaching consensus, and leveraging scarce resources. It has expertise in the areas of infectious diseases, informatics, child health and development, and injury control.
Mebendazole Advisory Committee
The Mebendazole Advisory Committee serves as an independent, authoritative body to advise Children Without Worms on strategic, technical and operational issues.
In February 2006, the Children Without Worms sent out a request for nominations to UN agencies and international NGOs working in STH control. While all the nominees were highly qualified, the initial six Mebendazole Advisory Committee members were selected to ensure that their areas of expertise were complementary and their geographical experiences diverse enough to mirror the global outlook of the initiative. The program has since increased the total number of members to eight to bring in additional expertise in hygiene education and water and sanitation.
Country Selection
In 2007, the Mebendazole Advisory Committee (MAC) approved donations of mebendazole to Bangladesh, Cameroon, Uganda and Zambia. This year, they approved donations of mebendazole to four additional countries: Cambodia, Cape Verde, Laos, and Nicaragua.
- High prevalence of STH infections
- National ownership and commitment
- Safe and effective mass distribution strategies
- Capacity to increase the scope of or accelerate STH control program as a result of the donation
- Effective strategies for sustainability of STH control program
- Multi-sectoral partnerships for STH deworming and transmission control activities
One of the program objectives is to have maximum impact on children most severely affected by the burden of STH infections. Therefore, the Mebendazole Advisory Committee makes recommendations based largely on epidemiological data demonstrating the size and needs of the target population. In addition to need, there must also be evidence that the country program has the capacity to distribute the drug safely and effectively.
Children Without Worms has selected eight countries to validate and refine program strategies. The lessons learned will provide insight to how best to move the program forward. Plans for expanding the program to other countries will be developed after the results of the current donation recipients are received and analyzed. Until that time, Children Without Worms will not be accepting applications for donated mebendazole.
Johnson & Johnson Commitment
The total commitment from J&J is up to 50 million doses per year. Approximately 30 million doses were donated to strategic recipients in 2007. The program will use lessons learned from the first year of operation to systematically grow to capacity and achieve maximum impact.
Currently, the mebendazole tablets that are available for donation are non-chewable, but it is anticipated that chewable tablets will be available for donation by the end of 2008.
The program will closely monitor and evaluate the success of the recipient countries’ deworming campaigns to determine how best to continue to have an impact on the lives of children burdened by intestinal worms.
HIV/AIDS, TB & MALARIA
Currently, the evidence is not definitive on the effect of deworming in individuals infected with both STH and malaria parasites. Some studies suggest that, in relation to malaria, helminth infection has a protective effect. When infected with helminths, the body generates a defensive response to protect itself, and in doing so, the body suppresses the effects of malaria parasites that cause severe illness. Therefore, in protecting itself against helminths, the body also protects itself against severe malaria.
However, other studies have shown that the presence of STH infections favor the development of malaria. The body normally triggers a different type of defensive response against a malaria infection than it would against STH infections. In generating a defensive response against STH infections, the body is not able to adequately produce the type of defensive response it would generate against malaria. This relationship also appears to be impacted by factors such as the age of the individual infected, the helminth species, and level of infection. Because of the conflicting results of the studies, there remains a need for more research to be carried out on this issue. Children Without Worms will stay abreast of new research findings in this field and will adjust its treatment strategies, if needed, in response to new evidence.
The body generates a different type of defensive response against STH infections than it would against tuberculosis infections. In generating a defensive response against STH infections, the body is not able to adequately produce the type of specialized defensive response it should against the tuberculosis bacterium, which is responsible for tuberculosis symptoms. Experiments carried out in animals support this hypothesis.
Additionally, studies focusing on the effectiveness of the Bacille Calmette-Guerin (BCG) vaccine against the tuberculosis bacterium have demonstrated that the vaccine is less effective in helminth-infected individuals. The BCG vaccine is usually given to individuals at high risk of tuberculosis infection to help the body generate a defensive response when it next encounters the tuberculosis bacterium. Given the fact that helminth infection prevents this response, there is a need for integrating anthelmintic therapy into tuberculosis control efforts for more effective results.
The relationship between helminths and the HIV virus in individuals suffering from both infections is unclear. Some studies suggest that helminth infections do not affect the level of infection with the HIV virus while others imply the exact opposite. Currently, it is speculated that deworming either favors or prevents the depletion of CD4+ T-cells, a type of cell involved in the body’s defensive response, which is depleted by HIV. Evidently, more research needs to be carried out because of the vast implications of mass deworming, in light of widespread co-endemicity of STH and HIV in developing countries.
ALLERGIES & VACCINE EFFICACY
Much of the available literature cites a protective effect of helminths in relation to allergic diseases. It has been noted that individuals with STH infections are less sensitive to substances that commonly cause allergies. Yet the literature on this relationship has been disputed. Some studies suggest that helminth infections are associated with an increased incidence of allergic diseases. Children Without Worms will stay abreast of new research findings in this field and will adjust its treatment strategies, if needed, in response to new evidence.
5. Could helminth infection be the cause for low efficacy of vaccine trials in the developing world?
Most vaccines, whether bacterial or viral, attempt to generate a defensive response in the body. Once the body generates a defensive response against the vaccine, a weakened form of bacteria and virus, it will be able to replicate this response when it next encounters that particular bacteria or virus.
However, STH infections hamper the body’s ability to respond effectively to the vaccine. For example, the Bacille Calmette-Guerin (BCG) vaccine, used to counteract the tuberculosis bacterium, has been demonstrated to be less effective in helminth-infected individuals. Furthermore, it is also speculated that intestinal helminths modify the inner surface of the intestine, which prevents the proper uptake of orally-administered vaccines. Thus, STH infections seemingly decrease the efficacy of vaccines in general, regardless of how they are administered. Hence, the underlying effect of helminths on the efficacy of vaccines needs to be taken into account when administered in developing countries, where STH infections are often highly prevalent.
NUTRITIONAL SUPPLEMENTATION
In the 2007 Lancet article in question , Andrew Hall advocates broadening the scope of existing anti-helminth programs. While Hall recognizes the improvements mass deworming brings about in nutrition and educational development, he argues that deworming alone is insufficient. Hall argues that given the fact that anemia and stunting are the results of iron loss and malnutrition, mass deworming will certainly decrease morbidity but only nutritional supplementation will allow school-aged children to gain weight and reverse anemia trends. Similarly, he argues, deworming may lessen the number of days missed from school and increase opportunities for cognitive and educational development, but cognitive and educational development will be more fully optimized with remedial teaching.
The mission of Children Without Worms is to promote sustainable STH control programs via a three-pronged approach: i) mass deworming using mebendazole; ii) hygiene education to improve health behaviors that facilitate transmission; and iii) sanitation improvement. While incorporating a nutrition supplementation component to this approach would be beneficial, it is not currently feasible for Children Without Worms to adopt this uniformly in all the programs it supports. However, through close collaboration with partners like the World Food Program, which routinely provides mass deworming with feeding and micronutrient supplementation in impoverished schools in 34 countries around the world, Children Without Worms is able to contribute somewhat to the holistic approach advocated by Hall.
MONITORING DRUG EFFICACY
The control programs against illnesses like HIV/AIDS, tuberculosis and malaria have integrated schemes for monitoring pathogen resistance and drug efficacy. What measures is CHILDREN WITHOUT WORMS taking to address the issue of potential resistance to mebendazole?
The issue of drug resistance has certainly been brought to the fore given recent publications documenting cases of reduced drug efficacy and/or drug resistance in various human helminths of public health importance. Studies carried out in Mali, Tanzania, and Vietnam demonstrated low efficacy of single-dose mebendazole among school-age children with hookworm infections. These reported cases are isolated and emerge against a backdrop of highly successful large-scale deworming initiatives around the world. Furthermore, these observations may be the result of misuse of available drug, poor drug quality, inappropriate parasite detection techniques, or flawed study methodology. An additional complication with single-dose mebendazole is the variable efficacy rates against hookworm even when there is no concern about resistance.
Nevertheless, the well-documented drug resistance developed by helminth parasites in animal hosts raises the need for a concerted monitoring component to large-scale deworming initiatives. Children Without Worms takes this issue seriously and is therefore, taking steps to address this need, in collaboration with the World Bank, WHO, and other interested parties. In fact, recommendations of the second meeting of the Mebendazole Advisory Committee in March 2007 the following:
a) WHO develop standard protocols for using available indicators to detect reduced efficacy for national managers of STH control programs.
b) Country programs should implement appropriate strategies to reduce drug selection pressure and delay or reverse the possible occurrence of drug resistance such as:
- Targeting treatment at high-risk groups
- Ensuring that the interval between treatments is longer than the parasite generation time
- Using combination of drugs with different modes of action
- Ensuring quality of drugs in use
- Implementation of protocols to monitor drug efficacy in vivo and in vitro
- Development of new anthelmintic drugs
In November 2007, the World Bank and WHO convened a meeting of technical experts from the fields of human and veterinary helminthology, and helminth control programs, including those for STH infections as well as control programs for HIV/AIDS, TB and malaria, to discuss these issues in depth and devise strategies to monitor drug efficacy. The expected outcome of this collaborative effort is the development of standardized techniques for evaluating drug efficacy as well as a manual to serve as a guideline for these monitoring schemes. With these in place, drug efficacy can be constantly evaluated and measures taken at the first signs of drug resistance. Children Without Worms will stay abreast of new research findings in this field and will adjust its treatment strategies, if needed, in response to new evidence.