Crustaceans, nematodes, trematodes, and polychaete annelids also serve as parasites. Internal parasites of badgers include trematodes, nematodes and several species of tapeworm. Blood parasites include louse flies, leeches, nematodes, cestodes, armadillo ticks, mites, and trematodes. Mayfly nymphs may serve as hosts for parasites such as nematodes and trematodes. Schistosomiasis (bilharzia) is a parasitic disease caused by the parasitic flatworm trematodes. The cobia is frequently parasitized by nematodes, trematodes, cestodes, copepods, and acanthocephalans. Microphallus is a genus of parasitic trematodes (flukes) in the family Microphallidae. Paragonimus is a genus of flukes (trematodes). Schistosoma is a genus of trematodes, commonly known as blood flukes. Nearly all trematodes are parasites of mollusks and vertebrates. The trematodes or flukes include 18,000 to 24,000 species, divided into two subclasses. The killdeer is parasitized by acanthocephalans, cestodes, nematodes, and trematodes. Endoparasites include nematodes, cestodes, and trematodes. Limpkins in Florida were examined for parasites, which included trematodes, nematodes, and biting lice. Schistosoma mekongi is a species of trematodes, also known as flukes.