Infection with STH and schistosomiasis is associated with inadequate sanitation and hygiene, while LF is transmitted by mosquitoes.
How do they spread?
Infection with roundworm and whipworm occurs by eating food or drink contaminated with worm eggs from faeces. For hookworm, infection usually occurs when infective larvae in soil contaminated with faeces enter the skin (commonly though the feet, legs or buttocks).
Infection with STH is associated with poverty, inadequate sanitation and hygiene, and certain behaviours such as defecating in the open.
Watch the video to learn more about STH transmission.
People become infected with schistosomes when they come into contact with fresh water that harbours parasites. Freshwater snails act as intermediate hosts for schistosomes before releasing them into the water.
Spread of schistosomiasis is linked to contamination of freshwater sources from infected people urinating in water bodies and defaecating in the open. As with STH, the underlying factors are poverty, lack of access to clean water and sanitation, and poor hygiene.
Watch the video to learn more about schistosomiasis transmission.
People become infected with LF when mosquitoes carrying infective-stage larvae bite them. The larvae enter the skin and migrate to the lymphatic system, where they develop into adult worms over a period of 6-12 months. Once they reach adulthood, male and female worms form nests that can produce millions of microfilaria (larva-stage worms) over the course of several years. The microfilaria circulate in peripheral blood, from where it can be picked up by biting mosquitoes to continue the transmission cycle.
The distribution of LF is strongly related to environmental factors that influence the distribution of mosquito species and is particularly prevalent in areas with hot and humid climates.
Watch the video to learn more about LF transmission.