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 pugilator 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.
Hassalstrongylus forresteri is a nematode worm of the genus Hassalstrongylus that infects the marsh rice rat in the United States. It was first described as Hassalstrongylus musculi by Marie-Claude Durette-Desset in 1972, but she later recognized it as a different species, H. forresteri. The females cannot be distinguished from those of the other species in the marsh rice rat, H. musculi and H. lichtenfelsi.
Hassalstrongylus musculi is a nematode worm of the genus Hassalstrongylus that infects the marsh rice rat and house mouse in the United States and Oryzomys couesi, Oligoryzomys fulvescens, and Handleyomys melanotis in San Luis Potosí, Mexico. It was first described as Longistriata musculi by Dikmans in 1935, but transferred to Hassalstrongylus in 1971 and 1972 by Marie-Claude Durette-Desset. She later renamed the material she had used to describe H. musculi in 1972 as H. forresteri. The females cannot be distinguished from those of the other species in the marsh rice rat, H. forresteri and H. lichtenfelsi.
Hassalstrongylus lichtenfelsi is a nematode worm of the genus Hassalstrongylus that infects the marsh rice rat in Florida. The females cannot be distinguished from those of the other species in the marsh rice rat, H. forresteri and H. musculi.
Taenia rileyi is a tapeworm of the genus Taenia from the United States. Adults infect bobcats and feral domestic cats, but larvae have been found in rodents such as the cotton mouse, the marsh rice rat in Florida, and the hispid cotton rat in Florida and Georgia. These rodents may serve as intermediate hosts.
Taenia mustelae is a tapeworm of the genus Taenia from the United States. Adults infect carnivorans such as weasels, skunks, and martens, but larvae have been found in rodents such as the Florida mouse and the marsh rice rat in Florida and the hispid cotton rat in Florida and Georgia. These rodents may serve as intermediate hosts.
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.
Microphallus basodactylophallus is a species of digenean parasite in the family Microphallidae. 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.
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.
Mastophorus muris is a parasitic nematode in the genus Mastophorus. It infects animals such as the marsh rice rat, hispid cotton rat, and singing vole.
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.
Physaloptera hispida is a parasitic nematode in the genus Physaloptera. It has been found on the marsh rice rat, hispid cotton rat, Florida mouse, cotton mouse, and oldfield mouse in Florida.
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.
Trichostrongylus affinis is a species of parasitic nematode in the genus Trichostrongylus. It primarily infects cottontails (Sylvilagus), but has also been found in the hispid cotton rat and the marsh rice rat.
Trichostrongylus sigmodontis is a species of parasitic nematode in the genus Trichostrongylus. It primarily infects the hispid cotton rat, but has also been found in the marsh rice rat.
