Definition
Any parasite that lives in and derives nutrition from its host.
Clinical Signs
May exhibit any, or all of the following signs. However, signs may not be apparent in an otherwise healthy rat.
Diarrhea, blood tinged stool.
Distended abdomen.
Weight loss.
Listlessness.
Pruritus (itching) in and around the rectum.
Rectal prolapse.
Etiology
Endoparasites, Helminths (worms) and Protozoa (one-celled or grouped cells), discussed here, are living organisms that enter a host by being ingested through direct transmission as cysts (larval stage of parasite), via an intermediate (exp. by ingestion of fleas, cockroaches, or grain beetles), or by indirect methods through skin penetration by blood parasites (see Ecto-Parsites). Endo-Parasites derive their nutrition by feeding off the host’s blood.
There are many species of endoparasites, but not all of these parasites infest or produce pathological symptoms in the domestic pet rat. The actual number of parasites present in the rat will greatly affect whether pathological symptoms are seen, as well as if the rat is already immunologically impaired, ill, or malnourished.
Some species of parasites are termed species specific. This means that they can complete their life cycle in only one species of host. Should they enter the wrong species they are unable to complete their life cycle and die, all generally without the host requiring treatment. Some species of endoparasites are host specific meaning that they have adapted themselves to a group of hosts.
Though there are but a very limited number of endoparasites that are host specific to both rats and man, the best prevention is to maintain a clean environment for your rat, prevent your rat’s exposure to other animals’ excrement, treat any external parasites promptly, and always wash your hands before and after caring for your rat and his environment.
Because there are many different species of endoparasites, some with complex life cycles that take place in different organs of the body, no one drug can effectively treat all parasites. It is for this reason that the veterinarian requires stool examinations, and in some cases blood work, to treat appropriately.
Listed here are the those endoparasites of most interest to the domestic rat owner, for being either the most commonly seen, but not significant in producing pathological symptoms, or those which do produce pathological symptoms in rats. Also mentioned are those of zoonotic concern to man, although, if adequate preventive care is maintained, are not commonly seen in domestic pet rats. Diagnostics, care and treatment are listed below that.
- Protozoa (one celled or grouped celled organisms)
- Spironucleus muris (flagellate), whose life cycle is direct, and transmitted via ingestion of cysts excreted in feces. It niches in the spaces of the small intestine. May not exhibit disease in an otherwise healthy adult rat, however, those with heavy infestation or who are
immunocompromised are noted to have inflammation of the intestines, with diarrhea resulting. 1
- Giardia muris (flagellate), life cycle also direct, and transmitted via ingestion of cysts in feces. Niches in the small intestine. Symptoms are usually subclinical, but may see weight loss and abdominal enlargement. Changes noted in the small intestine are minimal. Hosts include mice, rats, humans, hamsters, and several other species.
1
- Tritrichomonas muris (flagellate), transmission by ingestion of cysts in feces, and inhabits the large intestine. It is considered commensal (living in harmony) and not pathogenic. It does not infect humans.
- Entamoeba muris (genus ameba), transmission by ingestion of cysts in feces, and found in the large intestine. It is considered commensal, and nonpathogenic.
- Helminths
- Nematodes (roundworms, this includes pinworms)
- Syphacia muris (Oxyurid known as rat pinworm), most common parasite seen in rats. The life cycle is direct and requires only a short time, 11-15 days for completion of the cycle. They are migratory moving after ingestion to the large intestine and then to the perianal area to deposit eggs. These eggs are then disseminated into the surroundings, surviving weeks, where they can be reingested or ingested by another rat. Age, sex, and immune status are factors. Weanling rats, particularly males, may be most affected. These numbers diminish with the age of the rat. This parasite is not considered pathogenic unless there is heavy infestation or in the immunocompromized, and then symptoms may include: constipation, fecal impaction, and rectal prolapse. Humans have their own species of pinworm, and are considered a wrong host for the rat pinworm because its life cycle can not be completed.
- Aspicularis tetraptera (Oxyurid known as mouse pinworm), this parasite affects rats only rarely and is considered nonpathogenic, niches in the large intestine with the exception of the cecum.
- Trichosomoides crassicauda (bladder threadworm), found in wall of bladder. It can migrate to the lungs. Transmission is through eggs in the urine and can be passed from doe to offspring. Causes irritation to bladder, with resulting dysuria.
- Nippostrongylus muris, transmission by ingestion of eggs in feces, and found in the small intestine. It can produce pnuemonia and pulmonary hemmorhaging on migration of larvae through the lungs.
- Cestodes (tapeworms)
- Hymenolepis nana (Dwarf Tapeworm) transmission direct by ingestion of cysts, or by indirect transmission. Niches in the small intestine. These cyst can be found on fomites such as in cages, water bottles, litter, or carried on hands or spread through the air.
- Hymenolepis diminuta (tapeworm) requires an intermediate host such as flea, cockroach, or grain beetle for transmission. It is found in the anterior ileum (part of intestine) of the rat.
- Taenia taeniaeformis (tapeworm) known to be transmitted through cat feces, or feed contaminated with the parasite. Rats can also be an intermediary by harboring it in the liver, and Taenia seralis in the connective tissue. Keep pet rats from cats’ litter boxes when free ranging. Food, in particular meat, if given, should be cooked well, and store dry food in tightly closed containers.
These species of cestodes listed here can infect humans but the potential is low if care is taken to keep other domestic pets treated, and prevent pet rats having
exposure to them and their waste, also prevent exposure to wild rats, and insects known to spread the infection.
- Acanthocephala (entazoa)
- Moniliformis moniliformis (thorny-headed worm), found in small intestine of rodents, and may cause enteritis.
Handwashing, insect control, proper care and early treatment for any household animal, is the key to prevention for many endo-parasites!
Figures
- Fig. 1: Endo-Parasite slides and descriptions courtesy of
University of Missouri Research Animal Diagnostic Laboratory
Diagnostics
Obtain history.
Fecal wet mount or flotation as appropriate.
Scotch tape test for presence of pin worms.
Urine specimen for presence of thread worm.
Esinophil (EOS) count. In some endo-parasite presence may see increase in this count.
Treatment
Dosages for the following listed drugs can be obtained by reviewing the Rat Medication Guide
Nematodes (pinworms, roundworms)
Treat with one of the following drugs; fenbendazole, piperazine, or ivermectin.
Bladder Threadworm, Thorny-headed worm
Treat with one of the following drugs: fenbendazole, ivermectin.
Protozoa (exp. giardia, spironucleus muris)
Treat with metronidazole/Flagyl. *Note, should not be used in gravid females due to fetal deformities.*
Cestodes, (tapeworms)
Treat with one of the following drugs; praziquantel, niclosamide, or thiabendazole.
Nursing Care
Treat as prescribed until stool sample clear or as instructed by veterinarian.
Treat other indoor/outdoor pets as appropriate.
Treat any additional illnesses if rat’s health is already compromised.
Repeat cage and article disinfecting at least once a week.
Remove and discard articles made of wood.
Provide additional nutritional supplement to replace that absorbed by the parasite such as: soy baby formula, Ensure, Boost, or NutriCal paste (for dogs and cats found in pet store).
Replace any fluid lost through diarrhea by offering and encouraging fluids, such as water, Jello water , or electrolyte replacement drinks such as Pedialyte or Gatorade (which can be found in local grocery stores). Please note that Pedialyte is only good refrigerated for 24 hours after opened, but can be frozen as ice cubes and thawed as needed.
If necessary offer fluids by syringe every 2 hours. If dehydration is more severe, give warmed SQ fluids of Lactated Ringer’s solution per veterinarian assessment.
Outcomes
Free of parasite infestation.
Free of dermatitis.
No respiratory involvement, or infection controlled.
Weight within normal limits.
Prevention
Maintain rat’s overall general health.
Use of prepackaged processed litter, and the freezing of litter prior to using may be of help.
*Please note*
CareFRESH poly bags have been connected with mite infestations in the past and it is best to freeze before use.
CareFRESH big bags have a row of holes in the top of the bag which has allowed entrance into packs while stored in some pet stores and feed/tack stores. We haven’t heard of any other product with the same problem — yet.
Refrain from using outdated mixed feeds or rat blocks. Freeze or refrigerate feeds or rat blocks prior to use.
Be sure sipper water bottles are frequently washed and disinfected and filled with fresh clean water at all times.
Provide a clean cage environment.
Monitor humidity levels of the environment as cestodes favor very high humidity.
Quarantine all new rats for a minimum of three weeks and treat for infestation or infections if present prior to introducing to existing colony.
Prevent contact with excrement from other indoor/outdoor pets. Have other pets treated if fleas or ticks are present.
Treat any ecto-parasites promptly.
Posted on June 17, 2003, 13:20,
Last updated on August 4, 2008, 11:24
| Digestive
