This article describes various procedures for screening rats and mice to detect endo- or ectoparasitism. Several diagnostic assays will be demonstrated, both those suitable for use on live animals and those used after euthanasia of the animal. Photographs to aid in identification of rat and mouse parasites will be included.
Internal and external parasites remain a significant concern in laboratory rodent facilities, and many research facilities harbor some parasitized animals. Before embarking on an examination of animals for parasites, two things should be considered. One: what use will be made of the information collected, and two: which test is the most appropriate. Knowing that animals are parasitized may be something that the facility accepts, but there is often a need to treat animals and then to determine the efficacy of treatment. Parasites may be detected in animals through various techniques, including samples taken from live or euthanized animals. Historically, the tests with the greatest diagnostic sensitivity required euthanasia of the animal, although PCR has allowed high-sensitivity testing for several types of parasite. This article demonstrates procedures for the detection of endo- and ectoparasites in mice and rats. The same procedures are applicable to other rodents, although the species of parasites found will differ.
1. Endoparasite examination (Table 1)
1. Perianal tape test (also see section 5; these are usually performed at the same time)
2. Fecal flotation
3. Fecal concentration and centrifugation
4. Direct examination of intestines for helminths and protozoa
2. Ectoparasite examination (Table 3)
5. Fur pluck examination for ectoparasites (tape test)
6. Skin scrape
7. Direct examination of pelage
3. Representative Results:
See attached files identifying the following parasites: (Note: these procedures will detect any egg, helminth, or cyst present in the feces or on the skin and fur; only a few of these are listed below)
Endoparasites:
Syphacia muris (egg, worm) | Chilomastix bettencourti |
Syphacia obvelata (egg, worm) | Hexamastix muris |
Aspiculuris tetraptera (egg, worm) | Retortamonas sp. |
Rodentolepis nana (egg, worm) | Giardia spp. |
Tritrichomonas muris | Spironucleus muris |
Entamoeba muris |
Ectoparasites:
Myocoptes musculinis | Radfordia affinis |
Myocoptes musculinis | Radforida ensifera |
Myobia musculi |
Tape test | Fecal flotation | FCC | Direct exam1 | PCR | |
Protozoa | — | + | ++ | +++ | +++/NA2 |
Metazoa | |||||
Pinworm | +/-3 | +/-4 | +4 | +++ | +++ |
Tapeworm5 | — | + | ++ | +++ | NA |
Other roundworms5 | — | + | +++ | +++ | NA |
1. This method requires euthanasia of the animal.
2. There are not PCR detection methods currently available for every protozoan.
3. This method is most appropriate to detect Syphacia spp.
4. This method will be more likely to detect Aspiculuris, and less likely to detect Syphacia.
5. Tapeworms and roundworms other than pinworms are very rare in modern laboratory mice and rats.
Table 1. Class of endoparasite and appropriate detection method. Some methods will require euthanasia of the animal. NA indicates method is not currently available for these parasites.+ indicates suitability of the method for detection of the parasite in question, and – indicates that the method is not recommended for that parasite.
Solution | Specific gravity | Ingredients per 1L H2O |
Sodium chloride | 1.20 | 311 g sodium chloride |
Sodium nitrate | 1.20 | 338 g sodium nitrate |
Sodium nitrate | 1.30 | 616 g sodium nitrate |
Sugar | 1.20 | 1170 g sucrose1 |
Sheather’s sugar | 1.27-1.30 | 1563 g sucrose1 |
Zinc sulfate | 1.18 | 493 g zinc sulfate |
1. These solutions require refrigeration or the addition of 9 ml phenol as a preservative.
Table 2. Fecal flotation solutions (from Smith et al.)
Fur pluck (tape test) | Skin scrape1 | Direct exam1 | PCR | |
Lice | — | — | ++ | NA |
Mites | + | + | +++ | +++/NA3 |
Fleas4 | — | — | + | NA |
Ticks4 | — | — | ++ | NA |
1. This method requires anesthesia if it is to be performed on a live animal.
2. This method requires euthanasia of the animal.
3. There are not PCR detection methods currently available for every species of mite.
4. Fleas and ticks are extremely rare in modern laboratory animal facilities.
Table 3. Class of ectoparasite and appropriate detection method. Some methods will require euthanasia of the animal, and other methods will require anesthesia to perform them in live animals. NA indicates method is not currently available for these parasites. NA indicates method is not currently available for these parasites.+ indicates suitability of the method for detection of the parasite in question, and – indicates that the method is not recommended for that parasite.
When working in a laboratory, safety should always be a concern. Remember to wear appropriate protective equipment when working with animals and to clean your workstation with disinfectant before and after. These methods are primarily designed to find any parasites of laboratory rodents in the locations examined, i.e., they can detect exotic or exceedingly rare parasites as well as the more common pinworms and fur mites. Although they are equally applicable to other species, wild rodents may have additional parasites in locations such as liver, subcutis and brain, not evaluated by the above methods.
The authors have nothing to disclose.
Reagent name | Company | Catalog number | Comments |
Cutting board | Thermo Electron Corp | Cat #36114 | |
Small scissors | ROBOZ | RS-5910, G204 | 23mm blades, 3.5” length, straight |
Medium scissors | ROBOZ | RS-6808, G207 | 5” |
Forceps-Curved | ROBOZ | RS-8254 (M1/21004) | 4.5”, serrated, slight curve |
Forceps-Microdissecting | ROBOZ | RS-5238 | Hudson-(EWALD) |
Forceps-Tissue Forceps | ROBOZ | RS-8160 | Rat tooth |
Metal probe | VWR | Cat#25778-000 | |
Hemostats | Vantage | V97-48 | |
Applicator sticks | Puritan | 6in Applicators, Ref#807 | |
Dissecting microscope | Olympus | SZ51, Schott, ACE1 | |
Petri dish | VWR | 100mm, Cat#3401PDNL | |
Cover slips | VWR | Micro cover glass, Cat#48366-067 | |
Slides | VWR | VistaVision microscope slides Cat#16004-368 | |
Inoculating loop | VWR | Cat#50815-040 | |
Light microscope | Olympus | Model#BX41TF | |
Laboratory oven | Quincy Lab Inc. | Model 10 Lab Oven | |
Centrifuge | Beckman Coulter | Allegra X-12R | |
Vortexer | VWR | Mini-Vortexer | |
Test tube | Kimble-Chase | 15 ml disposable centrifuge tube, Cat#73790-15 | |
Cover slips | VWR | Plastic microscope cover slips, 22mm, Cat#48376-049 | |
White caps | VWR | Cat#60869-089 | |
Iodine | Rowley biochemical institute | Cat#SO-364 | |
Zinc sulfate | Sigma Aldrich | Cat#1000917519, Z4750-500G | |
Sucrose | Mallinckrodt Chemicals | Cat#8360-06 | |
Phenol | EMD | Cat#PX0510-1 | |
Cellophane tape | Staples | Invisible tape, Cat#504712 | |
Mineral oil | Mallickrodt | Cat#6358 |