A scourge on the poor
HEALTH
Hookworm infection, affected by climatic and socio-ecomomic factors, has serious consequenceces
By GELINDE NAREKINE
HOOKWORM is a parasite that affects people living in underprivileged poor areas of the world, where there is limited access to sanitation.
The prevalence of hookworm infection is affected by climatic and socio-economic factors affecting vulnerable societies. It thus, represents a significant burden for public health in tropical and subtropical countries.
Basically, there are two ways in which people become infected. Since hookworms live in soil contaminated with fecal matter, people get infected when walking barefoot on the soil. The worm’s larvae burrow their way through the foot and into the body.
People also get infected when they defecate outside in the soil or use their stool as fertilizer. Hookworm eggs can contaminate food or water sources and that can be taken in through eating and drinking. In this way, the worm makes an easy and direct entry into the host.
Globally, the economic and health burden of human hookworm infection surpasses published estimates for other diseases. The total economic burden is highest in the Western Pacific region, with transitioning countries such Brazil and China, still face considerable hookworm burden.
Interventions such as a vaccine or community-wide treatment to reduce the disease burden of hookworm among all age groups could have substantial impacts on this burden.
Despite the availability of effective treatment and control programmes, the burden of hookworm infection still remains high. It has been estimated that more than half a billion people are currently affected, whilst about 5 billion people are at risk of acquiring infection worldwide. This makes hookworm infection one of the most common, and yet, generally neglected diseases impacting humans the world over.
Serious impacts on pregnant women and children
While most infected people may not experience any symptoms at all, the disease can cause serious damage if left untreated over a period of time. Hookworm infection rarely results in death. However, its long-term impact can result in a series of serious public health consequences, especially for pregnant women and children.
Hookworm can reside for many years in the small intestine of their human hosts, where they feed on blood, resulting in internal blood loss, iron deficiency anaemia, and malnutrition in individuals who harbour moderate to high numbers of adult worms. These can cause subtle chronic health problems such as lethargy, impaired physical and cognitive development, and adverse pregnancy outcomes.
The disease state associated with hookworm infection is varied and ranges from being mild with transient clinical signs and symptoms to severe clinical disease, as well chronic and insidious effects on the growth, learning and productivity of individuals.
The precise form of morbidity and it severity depends on the intensity of hookworm burden. In public health terms, the overall impact of hookworm infection will ultimately depend on the underlying health status of certain populations, making them particularly vulnerable.
Public health consequences
There are a number serious public health consequences of hookworm infection, and include hookworm-induced protein loss, hookworm anaemia, maternal-fetal consequences, school performance, and productivity in adults.
Research has shown that with heavy worm burdens hookworm-induced protein loss is substantial and may result in hypoproteinemia leading to edema. In addition, hookworm-associated protein loss results in weight loss among vulnerable populations. Intestinal blood loss is the major clinical manifestation of human hookworm infection which results in iron deficiency and anaemia.
Because of their underlying iron and nutritional status, women of child-bearing age, pregnant women, and children are frequently the ones most susceptible to developing hookworm anaemia. Among school-age children and adults in resource-poor countries where host iron stores are often depleted, there is a well-established intensity-related association between hookworm infection and blood loss.
Furthermore, hookworm anaemia during pregnancy has been linked to adverse maternal-fetal consequences, including prematurity, low birth weight, and impaired lactation. Furthermore, neonatal infection resulting from vertical transmission of hookworm leads to severe disease associated with profound anaemia. In tropical countries, with the combination malaria and hookworm infections, the effect can be markedly profound.
In addition to clinical effects, severe and chronic infection with hookworm during children’s development also has life-long consequences for their cognitive performance and ultimately their educational achievements. Studies done in developing countries show very strong association between iron deficiency anaemia and children’s physical growth and their cognitive or intellectual development.
School children at risk
School children are particularly at risk from infection with hookworms (and other parasitic worms). Epidemiological evidence worldwide shows that school-age children are not only more likely to be infected, they are also likely to be more heavily infected than other age groups. Since the worm-burden is associated with the severity of morbidity, these children are likely to suffer most at an age when they are both growing and learning.
In Papua New Guinea, hookworm infection is most likely a neglected public health problem affecting the vast majority of people. Our exposure and susceptibility to hookworm infection is mainly related to environmental conditions, our behaviour and life style, our demography, and general socio-economic status.
It is one of the leading causes of iron deficiency anemia and malnutrition, severely affecting pregnant women and children. It increases the risk of in death and poor neonatal outcomes, including low birth weight and increased deaths in infants. In children, substantial impacts on physical and intellectual development may occur thereon.
The problem of hookworm infection can be managed through health protection measures. By way of effective communication between healthcare implementers, health authorities and decision makers, to overcome health-related issues for the community participation. Control measures in a community is not feasible, if only substantial improvements in socio-economic conditions, sanitation, education, and footwear availability and mass treatment strategies may lessen prevalence of hookworm infection.
Into the 21st century, research has repeatedly shown the association between hookworm infection and lower scores on tests of mental performance and educational achievements in school-age children. Effects of hookworm on mental functioning and educational achievements may be of equivalent importance for the individual as well as for national economic and social development.
Source of information
- Hastaning Shakti and colleagues 1999, Evidence for association between hookworm infection and cognitive function in Indonesian school children, Tropical Medicine & International Health, viewed 25 May 2022, http://www.
- Simon Brooker and colleagues 2008, Human Hookworm Infection in the 21st Century, Advance Parasitology, viewed 10 March 2022, https://www.ncbi.nlm.nih.gov
- Gelinde Narekine is a technical officer at the School of Medicine and Health Sciences, University of Papua New Guinea.