INTERVENTIONS - PREVENTIVE CHEMOTHERAPY

The World Health Organization (WHO) recommends preventive chemotherapy (PC) (i.e. population-level treatment with safe, effective drugs) as the primary intervention to control morbidity from and transmission of soil-transmitted helminthiasis (STH). Mass drug administration of effective drugs to targeted populations at-risk  has shown to effectively reduce STH prevalence and intensity of infection in targeted communities. Repeated PC with safe, affordable drugs at a recommended frequency  helps lower STH prevalence and intensity of infection levels below those associated with morbidity.

PREVENTIVE CHEMOTHERAPY

The World Health Organization defines preventive chemotherapy for STH as the large-scale delivery of anthelminthic drugs, either alone or in combination, as a public health tool for preventing morbidity due to infection. WHO also notes that PC can reduce transmission. Preventive chemotherapy is the key intervention for STH. Different at-risk populations receive PC via different population-suitable platforms. Existing platforms for the at-risk populations including the following:

Effective PC campaigns target large portions of the population, reducing the lifespan of helminths in the host, the number of infected individuals, and the duration that they can excrete eggs into the soil. Therefore, effective PC campaigns also decrease the amount of infectious eggs (and the larvae resulting from eggs) in the soil, reducing the likelihood of continued transmission.

Preschool-age Children PC Platforms
Co-administration with vitamin A supplementation
Immunization programs such as during polio vaccinations. 
Maternal, child health days including for antenatal check-ups
School-age Children PC Platforms
Schools
Women of Reproductive Age PC Platforms
Maternal, child health days including for antenatal check-ups
Community-based distribution via lymphatic filariasis elimination programs

 

MASS DRUG ADMINISTRATION

Mass Drug Administration (MDA) refers to the administration of drugs to targeted populations irrespective of infection status. Albendazole and mebendazole are the most common deworming medications. These medications have excellent safety profiles, are inexpensive, and are easily administered by non-medical personnel. 

Certified preventive chemotherapy (PC) medication, donated by Johnson & Johnson and GlaxoSmithKline, are available free-of-charge to national Ministries of Health through the World Health Organization. See more information about these donations here.

Albendazole
Cost: 400 mg single dose <$0.02 per tablet
Major ManufacturerGlaxoSmithKline
Donation target (annual): 400 million tablets donated each year 
Mebendazole
Cost: 500 mg single dose <$0.02 per tablet
Major Manufacturer: Johnson & Johnson
Brand name: Vermox®
Donation target (annual): 200 million tablets donated since each year

 

AT-RISK POPULATIONS 

STH may seriously damage the health of children of 1 - 14 years old and women of childbearing age. Preventive chemotherapy (PC) coverage of these populations is critical to minimize morbidity associated with STH infections.

Children
Children harbor the highest worm burdens for Ascaris and whipworm and are the main source of environmental contamination. Approximately 269 million preschool-age children (aged 1 to 4 years) and 571 million school-age children (aged 5 to 14 years) require PC for STH. Generally, Ascaris and whipworm infections have the greatest impact on children, as STH infection occurs concurrently with physical and intellectual development. Infection can cause anemia, malnutrition, and stunted growth. 
Woman of Childbearing Age
Women of childbearing age are particularly vulnerable to hookworm and the anemia caused by the parasite. Hookworm infection is strongly associated with iron-deficiency anemia during pregnancy. Approximately 250 million women of childbearing age are at risk of morbidity due to STH. PC during pregnancy (with iron supplementation) has been associated with reduced maternal anemia, increased weight of the newborn, and reduced infant mortality. [12]

 

TREATMENT FREQUENCY

According to the World Health Organization, the treatment frequency for populations at-risk of STH is determined by a baseline prevalence estimate among school-age children. Experts continue to debate the appropriateness of relying on prevalence estimates of school children when trying to understand hookworm infection levels (since that parasite primarily infects adults). Repeated treatments help reduce and maintain levels of infection below those associated with morbidity. 

Low Risk Areas
Baseline STH Prevalence: <20% 
Treatment: Case-by-case treatment is recommended
Moderate Risk Areas
Baseline STH Prevalence: ≥20% and ≤50% 
Treatment: Once a year treatment is recommended
High Risk Areas
Baseline STH Prevalence: >50% 
Treatment: Twice a year treatment is recommended

 

FIND OUT MORE! 

WHO STH Progress Report and Strategic Plan 2012
http://apps.who.int/iris/bitstream/10665/44804/1/9789241503129_eng.pdf 

WHO: Pharmacopoeial standards
http://apps.who.int/medicinedocs/documents/s22209en/s22209en.pdf

World Health Assembly Resolutions and Decisions
http://www.who.int/neglected_diseases/mediacentre/WHA_54.19_Eng.pdf


 

12. Ndibazza, J. et al. Effects of Deworming during Pregnancy on Maternal and Perinatal Outcomes in Entebbe, Uganda: A Randomized Controlled Trial. Clinical infectious Diseases. 50.4 (2010): 531–540. PMC.