Soil-transmitted helminthiases

14 February 2020

Soil-transmitted helminth (STH) infections are among the most common infections worldwide and affect the poorest and most deprived communities.

They are transmitted by eggs present in human faeces which in turn contaminate soil in areas where sanitation is poor.

The main species that infect people are the roundworm (Ascaris lumbricoides), the whipworm (Trichuris trichiura) and the hookworms (Necator americanus and Ancylostoma duodenale).

Intestinal worms produce a wide range of symptoms including intestinal manifestations (diarrhoea, abdominal pain), general malaise and weakness. Hookworms cause chronic intestinal blood loss that result in anaemia.

Teseum
These are intestinal worms (A. lumbricoides) found in a child in Hiiraan, Somalia. A child in the area has from 20 to 100 worms in his belly.

Soil-transmitted helminths are a group of three species of parasitic worms that colonize the intestine of humans

The main species that infect people are the roundworm (Ascaris lumbricoides), the whipworm (Trichuris trichiura) and the hookworms (Necator americanus and Ancylostoma duodenale).

T. Nazareth
Child with swollen belly, sign of infection with worms

Soil-transmitted helminths cause significant morbidity and growth retardation in children and women

B. Bernalund
Student of L.E.A Chukuku defecating within school premises.

The transmission of these parasites is due to environmental contamination with human faeces

WSCC
Fatou Sall striking a pose in front of a twin pit VIP latrine.

Improvement in sanitation to a level that impedes environmental contamination will stop STH transmission

UNICEF Ethiopia/Meklit Mersha
Bethlehem Woldu, 15, 10th grade at Gurumu Koysha primary and secondary school stands to facilitate IEC (information education communication) about iron deficiency and deworming.

Behavioural changes should accompany sanitation improvements

C. Kehr
VIP latrine under construction.

Improving sanitation to a high standard is a slow process that needs substantial resources

CJ Clarke/CIFF
A teacher administers deworming medication at a school deworming day in Hyderabad.

STH can be controlled by the periodic distribution of anthelminthic

While countries in which STH are endemic are improving sanitation, the morbidity caused by STH can be controlled by the periodic distribution of anthelminthic (preventive chemotherapy) medicines to groups at risk.

Heracles Project / Adriano Casulli

Anthelminthics against STH (albendazole or mebendazole) are extremely low cost

Anthelminthics against STH (albendazole or mebendazole) are extremely low cost (less than US$ 0.02 per dose), easy to administer (one tablet per individual) and very safe (the medicines are poorly absorbed and remain in the intestine, killing the worms); also, the medicines can be distributed at very low cost using existing infrastructure and non-medical personnel (i.e. by teachers in schools). (Photo of containers of albendazole, mebendazole and tablets)

WHO
Soil-transmitted helminths prevalence before and after preventive chemotherapy in Zimbabwe. (2010-2017)

preventive chemotherapy has eliminated morbidity from STH and reduced prevalence

In several countries where STH are endemic, this intervention has eliminated morbidity from STH and reduced prevalence. (I would put a photo of 2 maps showing STH prevalence before and after PC see attached pp presentations)

GPE/Stephan Bachenheimer
School-aged girls, attending school in Sierra Leone. They are part of the eligible population, treated for schistosomiasis and soil-transmitted helminthiases.

Once morbidity is eliminated, the intervention cannot be interrupted

However, once morbidity is eliminated, the intervention cannot be interrupted: if environmental contamination with human faeces is still present, re-infection will take place.