Lyperosomum intermedium is a parasitic trematode belonging to the subclass Digenea that infects the marsh rice rat. The species was first described in 1972 by Denton and Kinsella, who wrote that it was closest to Lyperosomum sinuosum, known from birds and raccoons in the United States and Brazil. Three years later, Denton and Kissinger placed the two, together with a number of other species, in a new subgenus of Lyperosomum, Sinuosoides. Species of Lyperosomum mainly infect birds; L. intermedium is one of the few species to infect a mammal.
Notocotylus fosteri is a parasitic fluke that infects the marsh rice rat in Florida.
Maritrema heardi is a parasitic fluke that infects the marsh rice rat in a salt marsh at Cedar Key, Florida. It was first listed as Maritrema sp. II in 1988, then described as the only species of a new genus, Floridatrema heardi, in 1994, and eventually reassigned in 2003 to Maritrema as Maritrema heardi. Its intermediate host is the fiddler crab Uca pigilator and it lives in the intestine of the marsh rice rat, its definitive host. Together with two other species of Maritrema, it is very common in affected marsh rice rats; it infects 19% of studied rats at Cedar Key. According to Tkach and colleagues, M. heardi is probably primarily a parasite of birds that has secondarily infected the marsh rice rat. Floridatrema was distinguished from Maritrema on the basis of its possession of loops of the uterus that extend forward to the place where the intestine is forked or even to the pharynx. Genetically, M. heardi may be closest to the morphologically similar M. neomi, which infects Neomys water shrews in the Carpathians.
Ascocotyle angrense is a fluke in the genus Ascocotyle that mainly infects birds. It has previously been confused with A. diminuta, which infects fish-eating birds and raccoons. It has also been recorded from the marsh rice rat in a saltwater marsh at Cedar Key, Florida, where it occurred in 25% of animals.
Catatropis johnstoni is a fluke from the United States. It was first described in 1956 by Martin, who had found cercariae released by the snail Cerithidea californica in southwestern California. When the cercaria were fed into chickens, they developed into mature worms; Martin speculated that the natural host was a waterbird. In 1970, a study of helminths of the marsh rice rat in a saltmarsh at Cedar Key, Florida, found flukes similar to C. johnstoni. The fluke was present in 30% of 110 examined rice rats, with the number of worms per rat varying from 1 to 500. Some Cerithidea scalariformis snails from this marsh also released cercariae similar to C. johnstoni from California. When introduced into chickens, marsh rice rats, Mongolian gerbils, golden hamsters, and house mice, these cercariae developed into infectious flukes. Bush and Kinsella, who reported on the result in 1972, regarded the Florida and California flukes as the same species, as there were only minor size differences between them. Because no marsh-inhabiting rodent occurs in both California and Florida, they agreed with Martin that the normal host of C. johnstoni was most likely a bird, perhaps a rail or shorebird. Nevertheless, the rate of infection in the rice rat is too high for it to be just an accidental host; perhaps C. johnstoni is restricted to saltmarshes but not host-specific.
Echinochasmus schwartzi is a fluke that infects dogs, muskrats, and marsh rice rats. It uses Fundulus fish as its intermediate host. Adults are similar to Echinochasmus microcaudatus, but differ in features of the oral sucker.
Fibricola lucida is a fluke that infects Virginia opossums, American minks, and marsh rice rats in North America. In a study in Florida, F. lucida was the only fluke of the marsh rice rat that occurred in both the freshwater marsh at Paynes Prairie and the saltwater marsh at Cedar Key. At the former locality, it infected 11% of rice rats and the number of worms per infected rat ranged from 1 to 65, averaging 17. At Cedar Key, 67% of rice rats were infected and the number of worms per infected rat ranged from 1 to 1975, averaging 143.
Gynaecotyla adunca is a fluke that normally infects birds. It has also been found in 15% of a sample of the marsh rice rat from a salt marsh at Cedar Key, Florida. It uses fiddler crabs such as Uca rapax as its intermediate host.
Maritrema prosthometra is a parasitic fluke from North America. It was first described in 1969 from the intestine of the clapper rail in eastern North America. Later, it was also found in the small intestine of 5% of a sample of marsh rice rats collected in a salt marsh at Cedar Key, Florida, where it used the fiddler crab Uca pigilator as an intermediate host.
Maritrema is a genus of trematodes (flukes) in the family Microphallidae, although some have suggested its placement in the separate family Maritrematidae. It was first described by Nikoll in 1907 from birds in Britain. Species of the genus usually infect birds, but several have switched hosts and are found in mammals, such as the marsh rice rat. Several species use the fiddler crab Uca pigilator as an intermediate host.
Microphallus basodactylophallus is a species of digenean parasite in the genus Microphallus. It was first described in 1969, as Carneophallus basodactylophallus, from southern Louisiana, where the raccoon is the definitive host, the first intermediate host is the snail Lyrodes parvula, and the second intermediate host is the crab Callinectes sapidus. It was later moved to the genus Microphallus. In 1988, John Kinsella recorded it from the marsh rice rat in a saltmarsh at Cedar Key, Florida. There, it was one of the most prevalent parasites in the marsh rice rat and used C. sapidus as an intermediate host.
Odhneria odhneri is a digenean parasite in the genus Odhneria of family Microphallidae. It infects several species of shorebirds, including the willet, as well as the marsh rice rat.
Probolocoryphe glandulosa is a digenean parasite in the genus Probolocoryphe of family Microphallidae. Recorded hosts include the clapper rail, ruddy turnstone, raccoon, little blue heron, Wilson's plover, black-bellied plover, and marsh rice rat.
Urotrema scabridum is a fluke in the genus Urotrema of family Urotrematidae. Recorded hosts include:
Capillaria gastrica is a parasitic nematode in the genus Capillaria. Among the known host species are the marsh rice rat and deermouse.
Litomosoides scotti is a parasitic nematode in the genus Litomosoides. First described in 1973, it infects the marsh rice rat and is known from a saltwater marsh at Cedar Key, Florida.
Parastrongylus schmidti is a species of parasitic nematode in the genus Parastrongylus. It was first described as Angiostrongylus schmidti in 1971 from the marsh rice rat in Florida, but later assigned to Parastrongylus.
Pterygodermatites ondatrae is a species of parasitic nematode in the genus Pterygodermatites. It has been recorded in the hispid cotton rat in Florida and Texas. In Florida, it has also been recorded on the marsh rice rat, together with an unnamed species of the same genus, the female of which cannot be distinguished from that of P. ondatrae.
Syphacia oryzomyos is a nematode that infects the marsh rice rat in Florida. A similar species of Syphacia has been recorded from the rice rats Oligoryzomys fulvescens and Handleyomys melanotis in San Luis Potosí, but because only females were found, this worm could not be identified to species.
