Pinworms (Mice & Rats)

Prevalence
  • Prevalence of 1.47% in Australasia amongst mice submitted for health monitoring to our laboratory, assessed by wet prep and faecal flotation methods
  • Dependent on - environmental load, gender (males tend to have a higher load), age (young animals tend to have a higher load), strain, and immune status
 
Significance
  • Significance limited to - decreased weight gain, behavioral changes, and altered immune responses
  • Nude mice (and other immunodeficient mice) have an increased susceptibility to develop heavy infestations and rarely mucosal invasion in the colon
  • Interference with research:
    • Syphacia spp. and A. tetraptera - may increase host humoral response to nonparasitic antigenic stimuli
    • S. obvelata - may be associated with termination of the tolerance state and induction of eosinophilic autoimmune oophoritis
    • Syphacia spp. - has accelerated hepatic monooxygenase system development
    • S. muris - have impaired transport of water, sodium, and chloride in rat intestines
Disease
  • Parasitic oxyurids – usually non- or mildly pathogenic in animals with normal immune systems
  • Syphacia spp. larvae and adults are primarily colonized in the caecum and anterior colon. Females lay adhesive-coated eggs on the perianal skin - infective 5-20 hours after release.
  • A. tetraptera larvae hatch in the caecum and then primarily colonize the crypts of Lieberkühn of the proximal colon. Eggs are deposited in the distal colon, excreted in the faeces, and become infective 5-8 days later.
  • Non-specific clinical signs – poor condition, rough coats, reduced growth rate, rectal prolapse, mucoid enteritis, intestinal impaction, constipation, intussusceptions, granulomas, and diarrhea
Transmission
  • Ingestion of embryonated eggs through contaminated water, food and bedding.
Diagnosis
  • Preferred – combination of perianal sticky tape test, motility slide of the caecal and duodenal contents, and wet preparation slide of the large and small intestinal content
  • Faecal float of the GIT content
  • Anal swab technique
  • PCR of faecal material
The life cycle of the parasite, timing of cage changes, and treatment of cages must be considered when interpreting results.
Strains
  • Mice: Syphacia obvelata and Aspiculuris tetraptera
  • Rats: Syphacia muris
 
These species specificities are predilections, not obligate associations. S. obvelata and A. tetraptera has been reported in rats. S. muris have been reported in mice.
Duration
  • S. obvelata and S.muris - direct life cycle, 12-15d from the time of ingestion of embryonated eggs to the migration of female worms to the perianal region where eggs are deposited
  • tetraptera - direct life cycle, 23-25d from the time of ingestion of embryonated eggs to the production of eggs by the female worms in the descending colon​
Durability
  • Eggs are persistent environmental contaminants which are very resistant to destruction
  • Remain infective in the environment for weeks
  • Rigorous sanitation methods are often required to rid animals of eggs
Screening
  • Screening of any introduced mice
  • Filter top/IVC cages for use in quarantine situations
  • Regular parasite examinations with treatment of infested animals
Prevention and Control
  • Barrier maintenance (control of animal and personnel entry) aids in preventing reintroduction
  • Disinfectants will not destroy pinworm ova, so they must be either physically removed (washing) or inactivated through heat sterilization (cages)
  • Regular removal of faecal material should be sufficient to remove embryonated ova and prevent re-infestation
  • Feed containing fenbendazole at 150ppm for three 7-day periods over 5 weeks or Avermectins (mainly represented by ivermectin) at an oral dose of 2.0mg/kg daily - effective against S. obvelata and S.muris (Fenbendazole efficacious against Aspiculuris)
  • Rederivation via hysterectomy and Caesarian section or embryo transfer
Reading
  • Dean H. Percy & Stephen W. Barthold, Pathology of Laboratory Rodents and Rabbits (Third Edition), 2007
  • Infectious Diseases of Mice and Rats National Research Council, 1991
  • Implications of infectious agents on results of animal experiments. Laboratory Animals, 1999, 33 Suppl 1: S39-87
  • Prevalence of viral, bacterial and parasitological diseases in rats and mice used in research environments in Australasia over a 5-y period. Laboratory Animals, 2011, 40 (11): 341-348
  • University of Missouri, Research Animal Diagnostic Laboratory website: http://www.radil.missouri.edu
  • Kathleen R. Pritchett & Nancy A. Johnston, A Review of Treatments for the Eradication of Pinworm Infections from Laboratory Rodent Colonies. American Association for Laboratory Animal Science, 2002, 41 (2)