Growing up, you must have been warned off going out barefoot. Aside from the many dangers in doing that – like stepping on broken bottles and other sharp objects -you are at the risk of getting infected with worms, which can cause the disease known as helminthiasis.
Soil-transmitted helminthiasis is a form of helminth infection caused by roundworms. These worms can be transmitted via soil that has been contaminated with fecal matter containing their eggs. This is why it is known as soil-transmitted helminthiasis.
The most notable species in this group of worms are the roundworms (Ascaris lumbricoides), hookworms (Necator americanus and Ancylostoma duodenale) and the whipworm (Trichuris trichiura). The species are usually grouped together due to their similar diagnostic procedures and response to the same medications.
The parasitic worm Strongyloides stercoralis is a gut helminth with specific characteristics. The parasitic requires a different approach to diagnosis, compared to other soil-transmitted helminthiases, making it challenging to identify.
Furthermore, Strongyloides stercoralis does not react to mebendazole and albendazole and is therefore not treated by large-scale preventive measures that target other helminthiases.
These infections are the most common globally, and they affect the poorest and most deprived settlements majorly. It has been estimated that approximately 2 billion people are infected; this means that a third of the global population is living with soil-transmitted helminthiasis.
The most significant number of cases occurring in the low-income rural areas of sub-Saharan Africa, Southeast Asia, Latin America, and China.
Poor sanitation is said to be the primary cause of these infections. Unhygienic practices such as open defecation, walking barefoot on contaminated soil, and not washing hands can put one at risk of being infected.
Mode of Transmission
These worms are transmitted by eggs that have been passed along with the feces of infected people. Adult worms reside in the intestinal parasites, where they produce thousands of eggs each day.
In areas with poor sanitation, contamination with these eggs can occur in the following methods:
- Eggs that are attached to fruits and vegetables are ingested when they are not properly washed, peeled, or cooked.
- Eggs are ingested by children who play on soil that has been contaminated and then put their infected hands in their mouths without washing them.
- Eggs are ingested from contaminated sources of water.
Additionally, the hookworm eggs hatch, and they release larvae that mature and penetrate the skin. People, children especially, become infected when they walk barefoot and play on contaminated, contaminated soil.
Human-to-human infection and infection via fresh feces do not occur as eggs in feces need approximately three weeks to mature in the soil before they can infect the host.
Only S. stercoralis can reproduce inside a human host. A. lumbricoides and T. trichiura do not reproduce in the human host.
These diseases have been associated with poverty, poor sanitation, and lack of clean, potable water. The control of these diseases is dependent on the provision of safe water and improved sanitary measures.
Although these diseases are prevalent in rural areas, urban areas are not exempt from them. The social and environmental conditions in urban slums provide a conducive environment for the spread of these diseases.
Diseases caused by Soil-transmitted Helminths
Ascariasis
This is the most common disease caused by soil-transmitted helminths, and it affects approximately one billion people. The roundworm, A. lumbricoides, causes ascariasis, and the condition is typically mild and shows little to no symptoms.
However, heavy cases have severe effects. They can cause intestinal blockage and impair growth in children. Children who are already suffering from malnutrition are the most infected, with the most prevalent group being between 3-8 years old.
Annual death caused by Ascariasis is estimated to be about 20,000. Children are at the most risk of getting infected due to the frequent exposure to contaminated environments.
Hookworm Disease
Necator americanus and Ancylostoma duodenale are the parasites responsible for causing hookworm diseases. Symptoms from mild infections include abdominal pain and diarrhea.
More severe infections can pose a serious health challenge for newborns, children, malnourished adults, and pregnant women. Hookworm infections have been linked to anemia and protein deficiency in developing nations.
Hookworm is very common in adults, especially women. It has been estimated that about 44 million pregnant women are infected with the parasite. The effects of the diseases on both mother and child include low birth weight, increased risk of mortality, and impaired production of milk.
Trichuriasis
This is caused by the whipworm (Trichuris trichiura). It is the third most common soil-transmitted helminthiasis, and it has been estimated to affect nearly 800 million people, with most of them being children. Acute symptoms from heavy infections include diarrhea and anemia.
While chronic symptoms of trichuriasis include growth retardation and impaired mental development. Despite being a tropical disease that affects developing nations, trichuriasis is quite common in the United States.
Nutritional Effects of Soil-transmitted Helminthiases
These diseases have severe effects on the nutrition of people they infect. The effects include:
- Hookworms cause long-term intestinal blood loss that can result in anemia.
- Some soil-transmitted helminths cause loss of appetite, which can result in the reduction of nutritional intake and physical fitness. T. trichiura, in particular, can cause diarrhea and dysentery.
- The worms can cause malabsorption of nutrients. Additionally, roundworms may compete for vitamin A in the intestine.
- The worms feed on the host tissues, including blood, which leads to a loss of protein and iron.
People with light infections usually do not suffer from the disease. Heavier infections can cause symptoms including diarrhea and abdominal pain, malnutrition, a general feeling of illness and weakness, and impaired growth and physical development.
Heavy infections can cause blockage of the intestines that should be treated surgically.
S. stercoralis may cause dermatological and gastro-intestinal effects and is also known to be associated with long-term malnutrition in children.
