What is one primary characteristic of soil-transmitted helminths?

Soil-transmitted helminths (STHs) are primarily characterized by their ability to thrive in unhygienic conditions. These parasitic worms, which include species such as Ascaris lumbricoides, Trichuris trichiura, and hookworms, are commonly found in areas with poor sanitation and hygiene practices. The life cycle of these worms often involves the contamination of soil with human feces, which can then serve as a source of infection when ingested through contaminated food, water, or soil.

The presence of these helminths is closely linked to environmental factors, particularly those associated with inadequate sanitation. A lack of access to clean water, proper sewage disposal, and basic hygiene creates an environment conducive to the survival and proliferation of these parasites. Hence, the strong association of soil-transmitted helminths with poor hygienic conditions highlights the importance of sanitation and public health measures in managing and controlling these infections effectively.

The other options do not correctly describe characteristics of soil-transmitted helminths, reflecting misconceptions about their habitat, affected population, or life cycle. For instance, these worms are not exclusive to urban areas or to adults; they can infect individuals of all ages, often particularly affecting children in endemic regions. Additionally