- Reproduction: Most species are hermaphroditic (possessing both male and female reproductive organs), with the notable exception of Schistosoma (blood flukes), which have separate sexes.
- Life Cycle: They typically have complex life cycles involving at least two hosts: a mollusk (usually a freshwater snail) as the intermediate host and a vertebrate (including humans) as the definitive host.
Trematodes are often classified by the primary organ system they infect in humans.
| Type | Examples | Primary Habitat | Transmission |
|---|---|---|---|
| Blood Flukes | Schistosoma species | Blood vessels (vasculature) | Skin penetration in water |
| Liver Flukes | Fasciola hepatica, Clonorchis sinensis | Bile ducts and liver | Ingesting raw fish or watercress |
| Lung Flukes | Paragonimus westermani | Lung parenchyma | Ingesting raw crabs or crayfish |
| Intestinal Flukes | Fasciolopsis buski | Small intestine | Ingesting contaminated water plants |
Foodborne trematode infections and schistosomiasis are significant public health issues, particularly in tropical and subtropical regions. The World Health Organization (WHO) estimates that these infections cause millions of life years lost to disability and death annually. Treatments like praziquantel are highly effective against most trematode infection.
