**1.1 Background information and disease burden**

Soil-transmissible helminths (STHs) refer to the intestinal worms infecting humans that are transmissible through faecal contaminated soil. Infections caused by STHs are widely endemic and constitute one of the major public health problems, particularly in African, South American, and Asian LMICs [1]. The geographical distribution of parasites causing these infections is known to be influenced by prevailing environmental and climatic conditions. For example, poor environmental sanitation and hygiene conditions in tropical and sub-tropical regions are major determinants of STHs. The WHO estimates that about 2.5 billion people globally, currently have no

access to improved sanitation whilst close to 1.1 billion others practice open defecation [2]. Furthermore, the inequalities in socio-economic status of human populations at risk, particularly regarding access to clean water and sanitation, housing, and the access to anti-helminthic treatment, impact the observed epidemiological distribution of STH infections [3]. The transmission is by human exposures to the infective stages, either by direct skin penetration or through ingestion, which can lead to serious illness, though infections remain asymptomatic in the majority of cases with lightintensity infections. Laboratory diagnosis is the gold standard in confirming STH infections, since clinical symptoms present as non-specific gastrointestinal diseases and among persons with high intensity of infection.

The current global disease burden suggests that nearly two (2) billion people are infected, with over 80% of the disease burden found in tropical and sub-tropical regions of LMICs [4]. An estimated 870million children live in areas of high prevalence in Africa, South Asia, and South America. The diseases are attributed to the four most prevalent STHs namely, *Ascaris lumbricoides*, *Trichuris trichiura*, or the hookworms (*Ancylostoma doudenale*/*Necator americanus*), infecting approximately 807–1121 million, 604–795 million, and 576–740 million people, respectively. *Strongyloides stercoralis*, which is the least prevalent and most neglected STH species, is responsible for an estimated 30–100 million infections globally. With the specific emphasis of the disease burden in LMICs, previous studies have found that unlike in Ghana (2.1%), *Ascaris lumbricoides* have the widest distribution reported in Nigeria (25.4%), Cameroon (30.8%), Equatorial Guinea (38.8%), and Congo (32.2%). In South America, infections with *Ascaris lumbricoides* is less widely dispersed in Ecuador (35.8%), Colombia (26.0%), and Venezuela (28.4%) compared with Asian LMICs like in the Philippines (33.6%), Afghanistan (36.0%), Malaysia (41.7%), and Bangladesh (38.4%). The hookworm infections with *Ancylostoma doudenales*/*Necator americanus*, remain common throughout African LMICs like Ghana (52.9%), in addition to the Asian LMICs, Malaysia (21.0%), Bangladesh (22.3%), Nepal (30.7%), and Papua New Guinea (60.6%). The prevalence of *Trichuris trichiura* infections in Asian LMICs like Malaysia (49.9%), and the Philippines (45.5%), as well as in the South American LMIC, Venezuela (28.4%) is more than that reported in the African LMIC Ghana, (0.8%).

It is worth considering that in addition to the single infections caused, multiplespecies infections in a single individual are also common, and taken together, can cause considerable global health impacts and decrease economic productivity in vulnerable populations of many LMICs [2, 5]. The epidemiological patterns of the disease burden require consolidated efforts by governments, communities, and healthcare institutions to adopt context-specific public health interventions that would see a reduction in the rates of STH infections, if not to eliminate or completely eradicate them. Even though these infections have been reported among specific risk groups like adult food vendors [6] and sanitation workers [7] in African LMICs, the greatest burden is confirmed in children of school-going age, affecting their cognitive development and physical growth [8]. For example, an estimated 270 million preschool children and over 568 million school-going children currently have infections that require anti-helminthic treatment and prevention interventions.

The available literature on transmission conditions of STHs, diagnostic techniques used to identify the species variety, risk factors to infections, and suggested public health interventions to reduce the risk of infection in exposed populations are inadequately published and are mostly presented in journal articles. This chapter, therefore, sought to conduct a narrative description of these aspects, plus present a case

study of STH infections in an occupational risk-group in an African LMIC, to provide context-based recommendations on how STHs can be prevented and controlled in vulnerable populations living in such settings.
