Helminth Prevention and Control
There are over 340 species of helminths; most are rare in humans but may infect animals that can serve as a resevoir for infection. Click here for more information on common helminths affecting humans and the diseases they cause. The four main species of helminths that infect people are Ascaris lumbricoides (roundworm); Trichuris triciura (whipworm); and Necator americanus and Ancylostoma duodenale (hookworm) (WHO, 2013). These four helminths also are commonly associated with malnutrition, including anemia, and disease in children (Hall et al, 2008). These worms are often called “soil-transmitted helminths” which refers to their mode of transmission. Although they are not intestinal helminths, schistosomes (commonly called blood flukes and bilharzia) also are prevalent and cause anemia in some geographic locations close to bodies of water.
Morbidity from helminth infections, including anemia, is determined by the intensity of the infection (number of worms in the gut) and the duration of the infection (Hall, 2008; Crompton et al, 1993). Moderate to heavy infections with hookworm are strongly associated with anemia (Hall, 2008; Roche et al, 1966).
The Most Vulnerable Groups
- Preschool children are at-risk of nutritional deficiencies caused by helminth infections .Helminths cause vitamin A malabsorption (Mahalanabis, 1976). In fact, deworming improves iron status in children and has improved growth in some studies.
- Pregnant women are at risk of nutritional deficiencies caused by helminth infections. Several large-scale studies have demonstrated that deworming and iron supplementation reduced anemia among pregnant women and have led to postive birth outcomes (Brooker, 2008; Smith, 2010).
School-aged children are mentioned here because school deworming programs have been an initiative globally. This group is particularly at risk of helminth infections because they are active and may be more inclined to play in the dirt and water. If a child is infected with helminths, their growth can be impaired, learning capacities diminished, and they are more susceptible to other infections. Making school-age children a target for deworming programs also may have may benefits for the entire population by reducing transmission in untreated students and other groups. For example, one study in Kenya found that when school-age children were dewormed in one school, untreated children in that school and in neighboring schools also benefited (Miguel et al, 2002).