# List of parasites of the marsh rice rat

A variety of parasites have been recorded from the marsh rice rat (Oryzomys palustris), a semiaquatic rodent found in the eastern and southern United States, north to New Jersey and Kansas and south to Florida and Texas, and in Tamaulipas, far northeastern Mexico. Some of these parasites are endoparasites, internal parasites, while others are ectoparasites, external parasites.
Parasitologist John Kinsella compared the endoparasites of marsh rice rats in a saltwater marsh at Cedar Key and a freshwater marsh at Paynes Prairie, both in Florida, in a 1988 study. He found a total of 45 species, a number unequaled in rodents. This may be related to the diverse habitats the rice rat uses and to its omnivorous diet; it eats a variety of animals which may serve as intermediate hosts of various parasites. The endoparasites in the saltwater marsh were dominated by trematodes (flukes), and those of the freshwater marsh by nematodes (roundworms). Endoparasites were found in the gastric mucosa (which lines the stomach), the cavity of the stomach, the small intestine, the cecum, the large intestine, the pancreatic duct, the bile ducts, the mucus of the liver, the pulmonary arteries, the abdominal cavity, and the pleural cavity. While the marsh rice rat harbors a number of host-specific species, such as the nematode Aonchotheca forresteri, other parasite species, such as the lone star tick (pictured), are shared with other mammals. Compared to the hispid cotton rat (Sigmodon hispidus), Florida marsh rice rats usually harbor fewer individual ectoparasites of each species. Borrelia, the bacterium that causes Lyme disease, has been identified in some ticks that infect the marsh rice rat and it has been identified as a possible natural reservoir for Borrelia.

## Key

| Name | The scientific name of the parasite species. A note is given where a species has been recorded on the marsh rice rat under different scientific names. Unnamed species are indicated with "sp." and parasites that could not be identified to species level are indicated with "unidentified". |
| Geographic occurrence | U.S. states where the parasite has been recorded on the marsh rice rat (no parasite records are available from the Mexican distribution of the marsh rice rat). This information is unavailable for some parasites. |
| Prevalence | Prevalence of infection with the parasite in a studied marsh rice rat population. The prevalence is given either as a percentage (e.g., 10%) or as a fraction (e.g., 5/50, meaning that 5 out of 50 examined animals were infected with the parasite), together with the site of study. Prevalence figures are unavailable for some parasites. |
| Present on other species? | "Yes" indicates that the parasite has also been recorded on other host species, "no" that it is (as far as known) specific to the marsh rice rat. For some unnamed species, the sources do not indicate whether or not the species is specific to the marsh rice rat. |

## Ectoparasites
### Acari

The Acari include the mites and ticks. Many are parasites of other animals. One study in South Carolina failed to find ticks on marsh rice rats living in marshes, which are an unsuitable habitat for the parasites.
| Name | Geographic occurrence | Prevalence | Present on other species? |
| Amblyomma americanum | Georgia | – | Yes |
| Amblyomma maculatum | South Carolina | – | Yes |
| Androlaelaps casalis | – | – | Yes |
| Androlaelaps fahrenholzi | Florida; Georgia | 50% (Everglades, Florida); 60% (Hillsborough Co., Florida); 3/29 (southwestern Georgia) | Yes |
| Dermacentor variabilis | Florida; Georgia; Missouri; South Carolina; Tennessee | 47% (Everglades); 65% (Hillsborough Co.); 12/29 (southwestern Georgia); 21% (Chester Co., South Carolina) | Yes, but marsh rice rat is among most important hosts |
| Euschoengastia peromysci | Georgia | – | Yes |
| Euschoengastia setosa | Georgia | – | No |
| Euschoengastia sp. | Georgia | – | No |
| Eutrombicula batatas | Florida | – | No |
| Eutrombicula splendens | Florida; Georgia | 95% (Hillsborough Co.); 1/29 (southwestern Georgia) | Yes |
| Gigantolaelaps mattogrossensis | Florida; Georgia; Texas | 35% (Everglades); 14/29 (southwestern Georgia) | Yes, but in the United States occurs mainly in rice rats |
| Haemogamasus, unidentified species | Georgia | – | – |
| Ixodes affinis | Georgia | – | Yes |
| Ixodes brunneus | Georgia | – | Yes |
| Ixodes cookei | Virginia | – | Yes |
| Ixodes minor | South Carolina | – | Yes |
| Ixodes scapularis | Georgia; North Carolina; South Carolina; Virginia | 30% (Outer Banks, North Carolina) | Yes |
| Ixodes texanus | Georgia | – | Yes |
| Ixodes, unidentified species | Florida | – | – |
| Laelaps manguinhosi | Florida; South Carolina; Texas | – | None north of Mexico |
| Laelaps sp. | Florida; Georgia | 50% (Everglades); 10% (Hillsborough Co.); 4/29 (southwestern Georgia) | Yes, but occurs mainly in rice rats |
| Listrophoridae, unidentified species | Florida; Georgia | – | – |
| Listrophorus, unidentified species | Georgia | 8/29 (southwestern Georgia) | – |
| Ornithonyssus bacoti | Florida; Georgia | 20% (Everglades); 50% (Hillsborough Co.); 11/29 (southwestern Georgia) | Yes |
| Ornithonyssus sp. | Georgia | 1/29 (southwestern Georgia) | Yes |
| Oryzomysia oryzomys | Georgia | – | No |
| Prolistrophorus bakeri | – | – | Yes |
| Prolistrophorus grassii | Georgia | – | Yes |
| Radfordia palustris | Florida; Georgia; South Carolina | – | No |

### Anoplura

Sucking lice (Anoplura) are a diverse group infecting placental mammals. Species found on marsh rice rats include three of the common genus Hoplopleura and Polyplax spinulosa, which more usually infects black and brown rats.
| Name | Geographic occurrence | Prevalence | Present in other species? |
| Hoplopleura hirsuta | Georgia | 1/29 (southwestern Georgia) | Yes; usually occurs in cotton rats |
| Hoplopleura oryzomydis | Delaware; Florida; Georgia; Louisiana; South Carolina; Tennessee; Texas | 18% (Everglades); 35% (Hillsborough Co.); 1/21 (Shelby County, Tennessee) | Yes |
| Polyplax spinulosa | Georgia; Tennessee | 2/29 (southwestern Georgia) | Yes; normally infects Rattus |

### Siphonaptera

Fleas (Siphonaptera) are common parasites of vertebrates, mainly mammals. Several species of fleas have been found on the marsh rice rat.
| Name | Geographic occurrence | Prevalence | Present in other species? |
| Ctenocephalides felis | Georgia | – | Yes |
| Ctenophthalmus pseudagyrtes | Missouri; Tennessee | 2/21 (Shelby Co., Tennessee) | Yes |
| Epitedia wenmanni | Missouri | – | Yes |
| Polygenis gwyni | Florida; Georgia; Mississippi; South Carolina | 4/29 (southwestern Georgia); 33% (Marion Co., Mississippi) | Yes; mainly found on the hispid cotton rat |
| Stenoponia americana | South Carolina; Tennessee | 1/39 (Shelby Co.) | Yes |

## Endoparasites

Unless otherwise specified, all information in this section is from Kinsella (1988, table 1).

### Nematoda

Nematodes are among the largest animal phyla and include at least 12,000 known species that are parasites of vertebrates. In Kinsella's 1988 study in Florida, species diversity was higher in the saltwater marsh (Cedar Key) than the freshwater marsh (Paynes Prairie), but nematodes at Paynes Prairie occurred more commonly and made up the bulk of the parasites found in rice rats there.
| Name | Geographic occurrence | Prevalence | Present in other species? |
| Aonchotheca forresteri | Florida | 46% (Paynes Prairie, Florida); 1% (Cedar Key, Florida) | No |
| Capillaria gastrica | Florida | 4% (Paynes Prairie, Florida); 6% (Cedar Key, Florida) | Yes |
| Capillaria hepatica | Florida | 8% (Paynes Prairie, Florida); 6% (Cedar Key, Florida) | Yes |
| Hassalstrongylus forresteri | Florida | 92% (Paynes Prairie, Florida); 9% (Cedar Key, Florida) | No |
| Hassalstrongylus lichtenfelsi | Florida | 92% (Paynes Prairie, Florida); 9% (Cedar Key, Florida) | No |
| Hassalstrongylus musculi | Florida | 92% (Paynes Prairie, Florida); 9% (Cedar Key, Florida) | Yes |
| Litomosoides scotti | Florida | 57% (Cedar Key, Florida) | No |
| Mastophorus muris | Georgia; Florida | 36% (Paynes Prairie, Florida); 1% (Cedar Key, Florida) | Yes |
| Monodontus sp. | Florida | 1% (Cedar Key, Florida) | – |
| Parastrongylus schmidti | Florida | 7% (Paynes Prairie, Florida); 3% (Cedar Key, Florida) | Not in the wild, but is able to infect other rodents in experiments |
| Pterygodermatites ondatrae | Florida | 20% (Paynes Prairie, Florida); 5% (Cedar Key, Florida) | Yes |
| Pterygodermatites sp. | Florida | 20% (Paynes Prairie, Florida); 5% (Cedar Key, Florida) | – |
| Physaloptera hispida | Florida | 35% (Paynes Prairie, Florida) | Yes |
| Physaloptera sp. | Florida | 4% (Cedar Key, Florida) | – |
| Skrjabinoclava kinsellai | Florida | 28% (Cedar Key, Florida) | No |
| Spiruridae, unidentified larvae | Florida | 5% (Cedar Key, Florida) | – |
| Strongyloides sp. | Florida | 30% (Paynes Prairie, Florida) | – |
| Syphacia oryzomyos | Florida | 42% (Paynes Prairie, Florida) | No |
| Trichostrongylus affinis | Florida | 14% (Paynes Prairie, Florida); 6% (Cedar Key, Florida) | Yes |
| Trichostrongylus sigmodontis | Florida | 8% (Paynes Prairie, Florida); 3% (Cedar Key, Florida) | Yes |

### Cestoda

Four tapeworms are known from the marsh rice rat, all in Florida, but three of those are usually found in other species and only rarely in the rice rat.
| Name | Geographic occurrence | Prevalence | Present in other species? |
| Hymenolepis diminuta | Florida | 19% (Paynes Prairie, Florida); 1% (Cedar Key, Florida) | Yes |
| Taenia rileyi | Florida | 1% (Cedar Key, Florida) | Yes; usually infects bobcats |
| Taenia mustelae | Florida | 0.5% (Paynes Prairie, Florida) | Yes; usually infects skunks and mustelids |
| Cladotaenia circi | Florida | 0.5% (Paynes Prairie, Florida); 1% (Cedar Key, Florida) | Yes; usually infects hawks |

### Digenea

Flukes (Trematoda) from the subclass Digenea are common parasites of small mammals with complex life cycles. In his 1988 study, Kinsella found an unprecedented 21 species of trematodes in Florida marsh rice rats. The intermediate hosts of these trematodes include a variety of invertebrates, fish, and amphibians, which are eaten by the marsh rice rat. Trematodes were generally more common at the Cedar Key saltwater marsh than at the freshwater marsh in Paynes Prairie.
| Name | Geographic occurrence | Prevalence | Present in other species? |
| Acanthotrema cursitans | Florida | 52% (Cedar Key, Florida) | Yes |
| Ascocotyle angrense | Florida | 25% (Cedar Key, Florida) | Yes; occurs mainly in birds |
| Ascocotyle pindoramensis | Florida | 9% (Cedar Key, Florida) | Yes; occurs mainly in birds |
| Brachylaima virginianum | Florida | 15% (Paynes Prairie, Florida) | Yes; occurs mainly in the Virginia opossum |
| Catatropis johnstoni | Florida | 30% (Cedar Key, Florida) | No other natural definitive host known, but occurs outside the range of the marsh rice rat and the normal host may be a bird |
| Echinochasmus schwartzi | Florida | 19% (Cedar Key, Florida) | Yes |
| Fibricola lucida | Florida | 67% (Paynes Prairie, Florida); 11% (Cedar Key, Florida) | Yes |
| Gymnophalloides heardi | Florida | 26% (Cedar Key, Florida) | No |
| Gynaecotyla adunca | Florida | 15% (Cedar Key, Florida) | Yes; normally infects birds |
| Levinseniella deblocki | Florida | 49% (Cedar Key, Florida) | Yes |
| Lyperosomum intermedium | Florida | 45% (Cedar Key, Florida) | No |
| Maritrema heardi | Florida | 19% (Cedar Key, Florida) | No |
| Maritrema prosthometra | Florida | 5% (Cedar Key, Florida) | Yes |
| Maritrema sp. I | Florida | 69% (Cedar Key, Florida) | Yes |
| Microphallus basodactylophallus | Florida | 94% (Cedar Key, Florida) | Yes |
| Microphallus nicolli | Florida | 9% (Cedar Key, Florida) | Yes |
| Microphallus sp. | Florida | 10% (Cedar Key, Florida) | Yes |
| Notocotylus fosteri | Florida | 3/4 (Cedar Key, Florida) | No |
| Odhneria odhneri | Florida | 6% (Cedar Key, Florida) | Yes |
| Probolocoryphe glandulosa | Florida | 56% (Cedar Key, Florida) | Yes |
| Urotrema scabridum | Florida | 23% (Cedar Key, Florida) | Yes |
| Zonorchis komareki | Florida | 1% (Cedar Key, Florida) | Yes |

### Pentastomida

Pentastomida is an enigmatic group of parasites that may be related to maxillopod crustaceans. One species, Porocephalus crotali, is known from the marsh rice rat. It infects various mammals in the southeastern United States, which serve as intermediate hosts; snakes which eat those mammals are the definitive hosts.
| Name | Geographic occurrence | Prevalence | Present in other species? |
| Porocephalus crotali | Florida; South Carolina | 12/105 (Levy County, Florida); 3/17 (Bear Island, South Carolina) | Yes |

### Apicomplexa

Apicomplexa is a major group of unicellular eukaryotes that encompasses several important parasites, including the malaria parasite Plasmodium. Three species are known from the marsh rice rat, all of which belong to the Eimerina clade. Two are in the genus Eimeria, members of which cause the economically significant disease coccidiosis in poultry. The third is a member of Isospora, which includes species that are pathogenic in humans and pigs.
| Name | Geographic occurrence | Prevalence | Present in other species? |
| Eimeria kinsellai | Florida | – | No |
| Eimeria palustris | Alabama | 7/19 (Tuskegee National Forest, Alabama) | No |
| Isospora hammondi | Alabama | 3/19 (Tuskegee National Forest, Alabama) | No |

## Footnotes

* ↑ Previously reported as Haemolaelaps glasgowi, but that name is a synonym of Androlaelaps fahrenholzi.
* ↑ The Gigantolaelaps mite from the marsh rice rat was first described as Gigantolaelaps cricetidarum, a separate species, but later considered identical with G. mattogrossensis; some still consider the two to be different species.
* ↑ Laelaps oryzomydis is a synonym.
* ↑ Previously known as Bdellonyssus bacoti, but since reassigned to Ornithonyssus.
* ↑ Originally assigned to Bdellonyssus (spelled Bdelonyssus), but that name is a synonym of Ornithonyssus.
* ↑ Previously reported as Chilodiscoides oryzomys, but now assigned to Oryzomysia.
* ↑ Previously known as Listrophorus bakeri, but since assigned to the genus Prolistrophorus.
* ↑ Previously known as Listrophorus bakeri, but since assigned to the genus Prolistrophorus.
* ↑ Listed as Hoplopleura quadridentata by Worth (1950), but later described as a separate species, Hoplopleura oryzomydis.
* ↑ Originally placed in the genus Capillaria, but later reassigned to Aonchotheca.
* ↑ Because females of these three species cannot be distinguished, data were combined.
* ↑ Originally named Angiostrongylus schmidti by Kinsella (1971), but moved to Parastrongylus by Ubelaker (1986).
* ↑ Females of these two species cannot be distinguished, so data were combined.
* ↑ Listed as Skrjabinoclava thapari by Kinsella (1988), but later described as a separate species.
* ↑ Listed as Stictodora cursitans by Kinsella (1988), but moved to Acantothrema in 2003.
* ↑ Listed as Ascocotyle mollienisicola by Kinsella (1988), but that name is a synonym of A. pindoramensis.
* ↑ Spelled Brachylaeme by Kinsella (1988).
* ↑ Reported as Parvatrema sp. by Kinsella (1988), but later described as Gymnophalloides heardi.
* ↑ Reported as Levinseniella sp. by Kinsella (1988), and described as L. deblocki in 1995.
* ↑ Reported as Maritrema sp. II by Kinsella (1988), then described as the only member of its own genus, Floridatrema heardi, and later again assigned to the genus Maritrema.
* ↑ This species was called prosthrometra by Kinsella (1988); the correct spelling is prosthometra.