**3.1 Transmission conditions and risk factors to STH infections in LMICs**

Studies in Ghana and other LMICs have shown that residents in rural and periurban communities have higher risks for STH infections than in urban communities because of the higher proportions of poverty, poor environmental hygiene, inadequate sanitation, open defecation, and inadequate waste management systems [9, 10]. These factors perpetuate the continued existence of STHs in such settings. The infective stages of STHs persist for longer periods in human or animal faecal polluted environments and can survive a wide range of physical and chemical conditions, thereby, posing the highest disease risks to community members, particularly in preschool children or those of school-going age, compared with other biological agents like bacteria and viruses [11, 12]. The adequate warmth and moisture in many tropical and sub-tropical LMICs also favour the survival of STH eggs and increase the risk of transmission to people living in endemic areas [13]. Researchers have also reported the persistence of STH eggs in salty beaches in Brazil [14], and Portugal [15], due to faecal contamination of the beach soil.

According to the WHO [16] although the human threadworm (*Strongyloides stercoralis*) is an important member of the STHs, it is the least prevalent. The most important STH species that infect people are the human roundworm (*Ascaris lumbricoides*), the human whipworm (*Trichuris trichiura*) and the two hookworm species (*Necator americanus* and *Ancylostoma duodenale*). These groups of STHs do not require intermediate hosts in their life cycle. Rather, the adult helminths lay eggs that hatch into larvae, grow, and then develop into adult worms inside the gastrointestinal tract of humans. The major mode of transmission is through direct faecal-oral ingestion of the eggs/ova (for *Ascaris lumbricoides*, *Trichuris trichiura*, and the hookworm, *Ancylostoma doudenale*) [17]. The *Necator americanus* is rather transmitted through direct penetration of the larvae through exposed parts of the body [18]. Government agencies and other stakeholders in the health sector of affected LMICs need to ensure the implementation of Public health intervention measures that target the blocking of the transmission chains, such as improved water, sanitation and hygiene (WASH) uptake, prevent the establishment of disease, and to improve the quality of lives, particularly of children and other occupational risk groups.
