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.^[1] Some of these parasites are endoparasites, internal parasites, while others are ectoparasites, external parasites.^[2]

The lone star tick is one of the parasites that the marsh rice rat shares with other mammals.

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.^[3] 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).^[3] 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.^[4] While the marsh rice rat harbors a number of host-specific species,^[5] such as the nematode Aonchotheca forresteri, other parasite species, such as the lone star tick (pictured), are shared with other mammals.^[6] Compared to the hispid cotton rat (Sigmodon hispidus), Florida marsh rice rats usually harbor fewer individual ectoparasites of each species.^[7] 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.^[8]

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.^[9] One study in South Carolina failed to find ticks on marsh rice rats living in marshes, which are an unsuitable habitat for the parasites.^[10]

Name	Geographic occurrence	Prevalence	Present on other species?
Amblyomma americanum	Georgia[11]	–	Yes[11]
Amblyomma maculatum	South Carolina[12]	–	Yes[12]
Androlaelaps casalis[13]	–	–	Yes[13]
Androlaelaps fahrenholzi[Note 1]	Florida;[14] Georgia[15]	50% (Everglades, Florida); 60% (Hillsborough Co., Florida);[14] 3/29 (southwestern Georgia)[16]	Yes[17]
Dermacentor variabilis	Florida;[18] Georgia;[16] Missouri;[19] South Carolina;[20] Tennessee[21]	47% (Everglades); 65% (Hillsborough Co.);[18] 12/29 (southwestern Georgia);[16] 21% (Chester Co., South Carolina)[12]	Yes,[11] but marsh rice rat is among most important hosts[19]
Euschoengastia peromysci	Georgia[22]	–	Yes[22]
Euschoengastia setosa	Georgia[22]	–	No[22]
Euschoengastia sp.	Georgia[23]	–	No[23]
Eutrombicula batatas	Florida[24]	–	No[24]
Eutrombicula splendens	Florida;[24] Georgia[16]	95% (Hillsborough Co.);[24] 1/29 (southwestern Georgia)[16]	Yes[24]
Gigantolaelaps mattogrossensis[Note 2]	Florida;[24] Georgia;[16] Texas[25]	35% (Everglades);[24] 14/29 (southwestern Georgia)[16]	Yes, but in the United States occurs mainly in rice rats[16]
Haemogamasus, unidentified species	Georgia[11]	–	–
Ixodes affinis	Georgia[11]	–	Yes[11]
Ixodes brunneus	Georgia[23]	–	Yes[23]
Ixodes cookei	Virginia[26]	–	Yes[26]
Ixodes minor	South Carolina[12]	–	Yes[12]
Ixodes scapularis	Georgia;[11] North Carolina;[27] South Carolina;[28] Virginia[29]	30% (Outer Banks, North Carolina)[27]	Yes[11]
Ixodes texanus	Georgia[11]	–	Yes[11]
Ixodes, unidentified species	Florida[30]	–	–
Laelaps manguinhosi[Note 3]	Florida; South Carolina; Texas[31]	–	None north of Mexico[31]
Laelaps sp.	Florida;[24] Georgia[16]	50% (Everglades); 10% (Hillsborough Co.);[24] 4/29 (southwestern Georgia)[16]	Yes, but occurs mainly in rice rats[24]
Listrophoridae, unidentified species	Florida;[18] Georgia[11]	–	–
Listrophorus, unidentified species	Georgia[16]	8/29 (southwestern Georgia)[16]	–
Ornithonyssus bacoti[Note 4]	Florida;[14] Georgia[16]	20% (Everglades); 50% (Hillsborough Co.);[14] 11/29 (southwestern Georgia)[16]	Yes[14]
Ornithonyssus sp.[Note 5]	Georgia[16]	1/29 (southwestern Georgia)[16]	Yes[16]
Oryzomysia oryzomys[Note 6]	Georgia[34]	–	No[34]
Prolistrophorus bakeri[Note 7]	–	–	Yes[36]
Prolistrophorus grassii[Note 8]	Georgia[34]	–	Yes[36]
Radfordia palustris[37]	Florida; Georgia; South Carolina[37]	–	No[37]

Anoplura

Sucking lice (Anoplura) are a diverse group infecting placental mammals.^[38] Species found on marsh rice rats include three of the common genus Hoplopleura^[39] and Polyplax spinulosa, which more usually infects black and brown rats.^[40]

Name	Geographic occurrence	Prevalence	Present in other species?
Hoplopleura hirsuta	Georgia[16]	1/29 (southwestern Georgia)[16]	Yes; usually occurs in cotton rats[41]
Hoplopleura oryzomydis[Note 9]	Delaware; Florida;[42] Georgia;[22] Louisiana;[43] South Carolina;[42] Tennessee; Texas[43]	18% (Everglades); 35% (Hillsborough Co.);[30] 1/21 (Shelby County, Tennessee)[43]	Yes[44]
Polyplax spinulosa	Georgia;[16] Tennessee[40]	2/29 (southwestern Georgia)[16]	Yes; normally infects Rattus[40]

Siphonaptera

Fleas (Siphonaptera) are common parasites of vertebrates, mainly mammals.^[45] Several species of fleas have been found on the marsh rice rat.^[46]

Name	Geographic occurrence	Prevalence	Present in other species?
Ctenocephalides felis	Georgia[22]	–	Yes[22]
Ctenophthalmus pseudagyrtes	Missouri;[47] Tennessee[48]	2/21 (Shelby Co., Tennessee)[48]	Yes[47]
Epitedia wenmanni	Missouri[47]	–	Yes[47]
Polygenis gwyni	Florida;[49] Georgia;[16] Mississippi;[50] South Carolina[51]	4/29 (southwestern Georgia);[16] 33% (Marion Co., Mississippi)[50]	Yes; mainly found on the hispid cotton rat[51]
Stenoponia americana	South Carolina;[52] Tennessee[53]	1/39 (Shelby Co.)[53]	Yes[53]

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.^[54] 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^[55] and made up the bulk of the parasites found in rice rats there.^[3]

Name	Geographic occurrence	Prevalence	Present in other species?
Aonchotheca forresteri[Note 10]	Florida	46% (Paynes Prairie, Florida); 1% (Cedar Key, Florida)	No[58]
Capillaria gastrica	Florida	4% (Paynes Prairie, Florida); 6% (Cedar Key, Florida)	Yes[59]
Capillaria hepatica	Florida	8% (Paynes Prairie, Florida); 6% (Cedar Key, Florida)	Yes[60]
Hassalstrongylus forresteri	Florida	92% (Paynes Prairie, Florida); 9% (Cedar Key, Florida)[Note 11]	No[61]
Hassalstrongylus lichtenfelsi	Florida		No[61]
Hassalstrongylus musculi	Florida		Yes[61]
Litomosoides scotti	Florida	57% (Cedar Key, Florida)	No[62]
Mastophorus muris	Georgia;[63] Florida[64]	36% (Paynes Prairie, Florida); 1% (Cedar Key, Florida)	Yes[63]
Monodontus sp.	Florida	1% (Cedar Key, Florida)	–
Parastrongylus schmidti[Note 12]	Florida	7% (Paynes Prairie, Florida); 3% (Cedar Key, Florida)	Not in the wild, but is able to infect other rodents in experiments[67]
Pterygodermatites ondatrae	Florida	20% (Paynes Prairie, Florida); 5% (Cedar Key, Florida)[Note 13]	Yes[64]
Pterygodermatites sp.	Florida		–
Physaloptera hispida	Florida	35% (Paynes Prairie, Florida)	Yes[64]
Physaloptera sp.	Florida	4% (Cedar Key, Florida)	–
Skrjabinoclava kinsellai[Note 14]	Florida	28% (Cedar Key, Florida)	No[68]
Spiruridae, unidentified larvae	Florida	5% (Cedar Key, Florida)	–
Strongyloides sp.	Florida	30% (Paynes Prairie, Florida)	–
Syphacia oryzomyos	Florida	42% (Paynes Prairie, Florida)	No[69]
Trichostrongylus affinis	Florida	14% (Paynes Prairie, Florida); 6% (Cedar Key, Florida)	Yes[64]
Trichostrongylus sigmodontis	Florida	8% (Paynes Prairie, Florida); 3% (Cedar Key, Florida)	Yes[64]

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.^[55]

Name	Geographic occurrence	Prevalence	Present in other species?
Hymenolepis diminuta	Florida	19% (Paynes Prairie, Florida); 1% (Cedar Key, Florida)	Yes[55]
Taenia rileyi	Florida	1% (Cedar Key, Florida)	Yes; usually infects bobcats[55]
Taenia mustelae	Florida	0.5% (Paynes Prairie, Florida)	Yes; usually infects skunks and mustelids[55]
Cladotaenia circi	Florida	0.5% (Paynes Prairie, Florida); 1% (Cedar Key, Florida)	Yes; usually infects hawks[55]

Digenea

Flukes (Trematoda) from the subclass Digenea are common parasites of small mammals with complex life cycles.^[70] 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.^[3] Trematodes were generally more common at the Cedar Key saltwater marsh than at the freshwater marsh in Paynes Prairie.^[55]

Name	Geographic occurrence	Prevalence	Present in other species?
Acanthotrema cursitans[Note 15]	Florida	52% (Cedar Key, Florida)	Yes[72]
Ascocotyle angrense	Florida	25% (Cedar Key, Florida)	Yes; occurs mainly in birds[73]
Ascocotyle pindoramensis[Note 16]	Florida	9% (Cedar Key, Florida)	Yes; occurs mainly in birds[75]
Brachylaima virginianum[Note 17]	Florida	15% (Paynes Prairie, Florida)	Yes; occurs mainly in the Virginia opossum[76]
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[77]
Echinochasmus schwartzi	Florida	19% (Cedar Key, Florida)	Yes[78]
Fibricola lucida	Florida	67% (Paynes Prairie, Florida); 11% (Cedar Key, Florida)	Yes[79]
Gymnophalloides heardi[Note 18]	Florida[80]	26% (Cedar Key, Florida)	No[80]
Gynaecotyla adunca	Florida	15% (Cedar Key, Florida)	Yes; normally infects birds[81]
Levinseniella deblocki[Note 19]	Florida[82]	49% (Cedar Key, Florida)	Yes[82]
Lyperosomum intermedium	Florida	45% (Cedar Key, Florida)	No[83]
Maritrema heardi[Note 20]	Florida[84]	19% (Cedar Key, Florida)	No[86]
Maritrema prosthometra[Note 21]	Florida	5% (Cedar Key, Florida)	Yes[87]
Maritrema sp. I	Florida	69% (Cedar Key, Florida)	Yes[55]
Microphallus basodactylophallus	Florida	94% (Cedar Key, Florida)	Yes[88]
Microphallus nicolli	Florida	9% (Cedar Key, Florida)	Yes[89]
Microphallus sp.	Florida	10% (Cedar Key, Florida)	Yes[55]
Notocotylus fosteri	Florida[90]	3/4 (Cedar Key, Florida)[90]	No[90]
Odhneria odhneri	Florida	6% (Cedar Key, Florida)	Yes[91]
Probolocoryphe glandulosa	Florida	56% (Cedar Key, Florida)	Yes[88]
Urotrema scabridum	Florida	23% (Cedar Key, Florida)	Yes[92]
Zonorchis komareki	Florida	1% (Cedar Key, Florida)	Yes[93]

Pentastomida

Pentastomida is an enigmatic group of parasites that may be related to maxillopod crustaceans.^[94] One species, Porocephalus crotali, is known from the marsh rice rat.^[95] It infects various mammals in the southeastern United States, which serve as intermediate hosts; snakes which eat those mammals are the definitive hosts.^[96]

Name	Geographic occurrence	Prevalence	Present in other species?
Porocephalus crotali	Florida;[97] South Carolina[98]	12/105 (Levy County, Florida);[97] 3/17 (Bear Island, South Carolina)[98]	Yes[97]

Apicomplexa

Apicomplexa is a major group of unicellular eukaryotes that encompasses several important parasites, including the malaria parasite Plasmodium.^[99] Three species are known from the marsh rice rat,^[95] all of which belong to the Eimerina clade.^[100] Two are in the genus Eimeria, members of which cause the economically significant disease coccidiosis in poultry.^[101] The third is a member of Isospora, which includes species that are pathogenic in humans and pigs.^[102]

Name	Geographic occurrence	Prevalence	Present in other species?
Eimeria kinsellai	Florida[103]	–	No[103]
Eimeria palustris	Alabama[104]	7/19 (Tuskegee National Forest, Alabama)[105]	No[105]
Isospora hammondi	Alabama[104]	3/19 (Tuskegee National Forest, Alabama)[106]	No[106]

Footnotes

1. Previously reported as Haemolaelaps glasgowi,^[14] but that name is a synonym of Androlaelaps fahrenholzi.^[13]
2. 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.^[25]
3. Laelaps oryzomydis is a synonym.^[31]
4. Previously known as Bdellonyssus bacoti,^[14] but since reassigned to Ornithonyssus.^[32]
5. Originally assigned to Bdellonyssus (spelled Bdelonyssus),^[16] but that name is a synonym of Ornithonyssus.^[33]
6. Previously reported as Chilodiscoides oryzomys,^[34] but now assigned to Oryzomysia.^[35]
7. Previously known as Listrophorus bakeri,^[34] but since assigned to the genus Prolistrophorus.^[36]
8. Previously known as Listrophorus bakeri,^[34] but since assigned to the genus Prolistrophorus.^[36]
9. Listed as Hoplopleura quadridentata by Worth (1950),^[30] but later described as a separate species, Hoplopleura oryzomydis.^[42]
10. Originally placed in the genus Capillaria,^[56] but later reassigned to Aonchotheca.^[57]
11. Because females of these three species cannot be distinguished, data were combined.
12. Originally named Angiostrongylus schmidti by Kinsella (1971),^[65] but moved to Parastrongylus by Ubelaker (1986).^[66]
13. Females of these two species cannot be distinguished, so data were combined.
14. Listed as Skrjabinoclava thapari by Kinsella (1988),^[4] but later described as a separate species.^[68]
15. Listed as Stictodora cursitans by Kinsella (1988),^[4] but moved to Acantothrema in 2003.^[71]
16. Listed as Ascocotyle mollienisicola by Kinsella (1988), but that name is a synonym of A. pindoramensis.^[74]
17. Spelled Brachylaeme by Kinsella (1988).
18. Reported as Parvatrema sp. by Kinsella (1988), but later described as Gymnophalloides heardi.^[80]
19. Reported as Levinseniella sp. by Kinsella (1988), and described as L. deblocki in 1995.^[82]
20. Reported as Maritrema sp. II by Kinsella (1988),^[4] then described as the only member of its own genus, Floridatrema heardi,^[84] and later again assigned to the genus Maritrema.^[85]
21. This species was called prosthrometra by Kinsella (1988);^[4] the correct spelling is prosthometra.^[87]