<Li> Schistosomiasis / bilharziasis (Schistosoma infection) </Li> <Ul> <Li> Moniliformis infection </Li> </Ul> <P> Helminths are transmitted to the final host in several ways . The most common infection is through ingestion of contaminated vegetables, drinking water, and raw or undercooked meat . Contaminated food may contain eggs of nematodes such as Ascaris, Enterobius, and Trichuris; cestodes such as Taenia, Hymenolepis, and Echinococcus; and treamtodes such as Fasciola . Raw or undercooked meats are the major sources of Taenia (pork, beef and venison), Trichinella (pork and bear), Diphyllobothrium (fish), Clonorchis (fish), and Paragonimus (crustaceans). Schistosomes and nematodes such as hookworms (Ancylostoma and Necator) and Strongyloides can penetrate the skin directly . Finally, Wuchereria, Onchocerca, and Dracunculus are transmitted by mosquitoes and flies . In the developing world, the use of contaminated water is a major risk factor for infection . Infection can also take place through the practice of geophagy, which is not uncommon in parts of sub-Saharan Africa . Soil is eaten, for example, by children or pregnant women to counteract a real or perceived deficiency of minerals in their diet . </P> <P> Specific helminths can be identified through microscopic examination of their eggs (ova) found in faecal samples . The number of eggs is measured in units of eggs per gram . However, it does not quantify mixed infections, and in practice, is inaccurate for quantifying the eggs of schistosomes and soil - transmitted helmiths . Sophisticated tests such as serological assays, antigen tests, and molecular diagnosis are also available; however, they are time - consuming, expensive and not always reliable . </P>

Which are the most frequent cause of helminth infections in the united states