American Fancy Rat & Mouse Association

This article is from the Sep./Oct. 1991 AFRMA Rat & Mouse Tales news-magazine.


Internal and External Parasites of Rats and Mice; Pyometra in Rats

Internal and External Parasites of Rats and Mice

By Carmen Jane Booth
Domestic rats and mice are hosts to far fewer parasites than their wild counterparts, because husbandry practices interrupt complex life cycles. It is imperative that feed, bedding, and water remain uncontaminated with urine and feces from wild rats, mice, birds, insects, and domestic cats in order to prevent cross contamination and infection since some parasites require multiple hosts (different species) to complete their life cycle. In addition, some parasites are nonpathogenic (do not cause disease) in some hosts, but are highly pathogenic in others. Only the more common parasites will be discussed here since treatment is often the same and some are difficult to diagnose.

Internal: Endoparasites

For the parasites that shed eggs in the feces, a fecal flotation and microscopic exam can be done to demonstrate the presence of infection. For Syphacia species, the scotch tape test can be done—take a piece of tape and press it a few times in the perianal region and look under a microscope for the presence of eggs. Many of these parasites can be diagnosed post mortem (after death) but become impossible to find if many hours have passed since the animal died.

Protozoa - single cell organisms
coccidia Eimeria species Rat/Mouse infect intestinal tract   diagnosis - presence of oocysts in fecal flotation test or in the intestinal lining
Cryptosporidium muri Rat/Mouse infect stomach   diagnosis - presence of oocysts in fecal flotation test or in the intestinal lining
*Toxoplasma gondii Rat/Mouse, Cats intestinal   diagnosis - presence of oocysts in fecal flotation test or in the intestinal lining
Flagellate Spironucleus (Hexamita) muris Rat/Mouse live in duodenum can cause diarrhea, weight loss and sudden death diagnosis by microscopic exam of duodenal contents
Hepatozoon muris Rat live in the liver    
Oxyurids - pinworms Syphacia muris Rat cecum and colon eggs found on the hair around the anus (perianal) scotch tape test
Syphacia obvelata Mouse same same same
Aspicularis tetraptera Rat/Mouse cecum and colon eggs passed in the feces fecal float
Misc: Heterakis spumosa Rat/Mouse cecum and colon eggs passed in the feces; this is a non-pathogenic organism  
Cestodes - tapeworms
  *Hymenolepis nana Rat/Mouse small intestine   fecal exam
  Hymenolepis diminuta Rat/Mouse anterior ilium can be transmitted by fleas, cockroach, or beetles  
  Taenia taeniaformis (Cysticercus fasiolaris) Rat/Mouse, Cats intestine, liver   fecal exam or liver histology

*Potential Zoonosis, i.e. can infect humans

External: Ectoparasites - Diagnosis - skin scrapings, scotch tape test, histology

All of these lice and mites spend their entire life cycle on the host except for O. bactoi. The common signs include: itching (pruritus), hair loss (alopecia), blood loss (anemia), skin irritation (dermatitis), unthriftiness, restlessness, and rough hair coat. In order to get rid of these beasts, the life cycle must be disrupted for those that spend their life on the host, and the environment treated for those that can live off the host. A new treatment not listed in the tables is Ivermectin 400 micrograms/kilograms subcutaneously two treatments two weeks apart. This is not a federally approved use for Ivermectin, but can be done by your veterinarian. The ivermectin needs to be diluted in sterile saline to meet the dose requirement.

I personally had my rat Poly treated with Ivermectin for her pruritus and rough hair coat. I had done numerous skin scrapings and scotch tape tests to try and find evidence of parasites and was unsuccessful. My dermatology professor advised me to treat her and see if she improved. Poly is no longer scratching and her coat looks great.

Polyplax serrataMousebase of hair shaft
Polyplax spinulosaRatbase of hair shaft
Myobia musculiniMousebase of hair shaft
Myocoptes musculinusMousemiddle third hair shaft
Radfordia affinisMousefur, hair follicle
Ornithonyssus bactoi
(Tropical Rat Mite)
Ratonly on host during feeding, find in the environment
Radfordia ensiferaRatfur, hair follicle
Notoedres muris
(Ear Mange Mite)
Ratburrows in skin

Included are 2 tables with treatment protocols from a 1984 text.

Table 1 - RATS
Selected Treatment Regimens for Common Parasites a,b

OxyuridsPiperazine citrate3–10 gm/liter drinking water for 7 days, repeat 7 days
Piperazine adipate0.5 gm/liter drinking water for 3 days
Pyruvinium pamoate3 mg/liter drinking water or 1.2 mg/kg feed for 4 weeks
Dichlorvos0.5 mg/gm feed for 1 day
TrichosomoidesMethyridine100 mg/g sc, single dose
CestodeNiclosamide100 mg/kg po, single dose
EctoparasitesRotenone0.5–1.0% dust
Silica dustWith or without pyrethrin
Dichlorvos strip24 hr/week on cage top for several weeks
Dichlorvos pellets2–6 gm of pellets in bedding for 5 days, change bedding and cage, repeat at 12 days, change and repeat at 1 month
Diazinon0.25% dip
Malathion3–5% dust, up to 0.5% spray or up to 2% dip, repeat at 12 days
Ronnelup to 0.5% dip
Carbaryl1% spray

a Information kindly supplied by Dr. J. W. Streett, Yale university.
b A number of these compounds have adverse effects on the experimental usefulness of treated rats and therefore should be used with discretion and full knowledge of the investigator.

Table 2 - Mice
Reported Treatment for Ectoparasitism of Laboratory Mice a

Chemical or generic nameTrade or common nameMethod of administration Parasite treated and efficacy
Di-(p-chlorophenyl)menthyl carbinol and tetraethylthiuram monosulfide DMC or Dimite (2 gm/liter) and Tetmosol (67 mg/liter of 25% solution) Two dippings 1 hr apart by immersion and swimming, 30 sec; repeated 1–3 weeks later Myobia, Myocoptes, Psorergates, Polyplax; eradicated
Di-(p-chlorphenyl)methyl carbinol DMC (Dimite), 2 gm/liter Single dipping Myocoptes; eradicated
Tetraethylthiuram monosulfide Tetmosol (67 gm/liter) of 25% solution Single dip with swimming Myobia; “usually sufficient”
Tetmosol, 2.5% Two dippings with immersion at 14-day intervals Myobia; not effective
2-(p-tert-butylphenoxy)isopropyl-2-choroethyl sulfite plus Nacconal Aramite-15W, 2% plus wetting agent, 0.1% Single dip by immersion and swimming, 17 sec Myobia, Myocoptes, Psorergates, Polyplax, Trichoecius, Radifordia; eradicated
Benzene hexachloride BHC, 0.625% Two dippings with immersion at 14-day intervals Myobia; not effective
Benzene hexachloride BHC Dusting Mycoptes; “cures condition”; Myobia; ineffective
0-1-Dimethyl-5-(dicarbethoxyethyl) dithiophosphate Malathion, 2.5% Two dippings with immersion at 14-day intervals Myobia; not effective
Malathion, 1% and 4% Five dippings at 3-day intervals Myobia; not effective
Malathion, 2% Single dipping Myocoptes; eradicated
Malathion, 2% Single dip by immersion and swimming, 17 sec Myobia, Myocoptes; effective
Malathion. 0.125% (Malastan E-CSO, emulsifiable) Single dip by immersion of rats Polyplax; eradicated
Pyrethrins 5% with 2.5% bucarpolate Pyractone, 1% Five dippings at 3-day intervals Myobia; eradicated
Pyrethrins 5% with 25% bucarpolate Super Pyractone M.429, diluted to give 0.06% pyrethrin, 0.3% bucarpolate Two dippings with immersion at 14-day intervals Myobia; effective
SG-67 Dri-Die (0.5 gm per mouse) Applied individually as a dust Myobia; not effective
Silica sorptive dust Dri-Die 67 Applied individually Polyplax
Silica dust with pyrethrin Dri-One Applied individually Polyplax
Formel 5-brommethyl-1,2,3,4,7,7-hexachlorobicyclo-(2,2, 1) hepten-(2) Alugan; 0.6% solution Two dippings at 11-day intervals Myobia; eradicated
Sulfur 325 mesh dusting sulfur One pinch dusted onto animal Myobia, Myocoptes; 95–98% effective
Chlordane, 2 gm 5% dust Sprinkled over contact bedding Polyplax; eradicated
Lindane, 10 gm 1% dust Sprinkled over contact bedding; several applications Myobia, Myocoptes; 90–98% effective
Kelthane, 5% wettable powder Used as dust, 0.5 gm per mouse Myobia; effective
Gamma HCH Jacutin spray (20% in oil) Individually with small brush; twice at 12-day intervals Myobia; effective
Dibutyl phthalate   Applied topically to affected areas Psorergates; effective
Dichlorvos (DDVP) Vapona (18% in resin strip) 1 x 2.5-in. resin strip on cage top, under filter cap Myocoptes; effective
  2 x 2.5-in. resin strip on cage top, under filter Myobia; effective
Atgard (anthelmintic) pellets 2 gm sprinkled in bedding; on day 8 cage changed, 2 gm added (14-day exposure) Myobia; effective
Vaporal (4.65% DDVP, 5% ronnel) liquid dip 2 ml per cage on contact litter Myobia; effective

a From Weisbroth (1982).

(Anyone suspecting their animal(s) of having a medical problem should seek the care of their local veterinarian.)

Pyometra in Rats

From Donna Galins, Brea, CA
I had a rat named Cynder. She was about l½ years old. I never bred her and she shared a cage with another rat, also l½ years old and never bred. The other rat’s name was Blossom.

Back in January of 1991, I found blood in the cage. I was not able to find out which rat, if either, was bleeding or injured. Also at that time, Blossom’s mammary gland (first left) was swelling and looked white. I took her to the vet thinking that maybe she was the one that was bleeding. The doctor took a sample of the liquid from the mammary gland. We didn’t know what to think. The vet drew all of the fluid out and she seemed to be all right.

When I went to place her back in the cage and found more blood, it was then that I knew it must be from Cynder. I picked her up and discovered blood on her rear end. After discussing the situation with the vet, he didn’t know what the problem could be. The bleeding continued off and on for a few months. However, she was eating, eyes very alert, active, gaining weight, and generally doing well. During this time, Blossom’s mammary continued filling with white liquid and getting bigger. We kept draining the gland, finally discovering that the fluid was milk. For an unknown reason she was producing milk, with all the other glands showing the same thing.

She then began to drag Cynder around the cage, attempting to “mother” her. I didn’t know what to do for her. We kept draining her glands, trying to make her more comfortable. Finally, I talked with Karen and she suggested that I give her some babies to nurse. I did this, but all she did was drag them around the cage, never nursing them. Her mammary glands continued to swell.

Cynder was bleeding worse during this time. Her body started to feel mushy, but was still alert, eyes clear, and eating. I had decided it was time to put them to sleep—it was a very sad thing to do. We did a necropsy on Cynder and we found that she had a very bad infection called pyometra (an infection of the uterus). There was a large mass and another one growing.

I was glad I made the decision to put Blossom and Cynder to sleep. I will always remember them with a happy heart and will miss them. *

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July 7, 2014