Procedures for Campus-Wide Fur Mite Treatment

Unit for Laboratory Animal Medicine
Feb 1, 2013 12:00 am

This document provides an overview of the procedures necessary for the coordinated fur mite treatment of all of the mouse and rat colonies at the University of Michigan Ann Arbor campus. This document also describes procedures needed for quarantine of those animals not included in the treatment course and the process used for establishing the effectiveness of the treatment.

  • Responsibility

    1. Principal Investigator (PI)
      1. Must notify the faculty veterinarian in advance to discuss alternative treatment options, including quarantine, if they elect not to treat their colony with ivermectin (chow or water).
    2. Faculty Veterinarian
      1. Consult with PIs on an individual basis to determine best course of action (alternative therapy or quarantine) if colony treatment with ivermectin (chow or water) is declined.
      2. Enter alternative actions in the Special Circumstances Database.
      3. Notify the area husbandry supervisor and RHST when a PI is granted permission to avoid treatment and utilize quarantine procedures.
      4. Provide recommendations for additional action in the event of a contamination or treatment failure.
    3. Veterinary Resident
      1. Notify the TST supervisor to coordinate and schedule the diagnostic testing of both quarantine and alternative treatment colonies.
    4. Veterinary Technician
      1. Perform fur plucks on all dermatitis cases and submit them to ADL for assessment.
    5. Husbandry Technicians & Supervisors
      1. Administer the treatments using ivermectin or Mite Arrest.
      2. Husbandry supervisors are responsible for notifying the IVAC manager of the location and any room/building movement of post-treatment, egg-positive cages. They will also label the cage cards of egg-positive animals with a red Post-It tab denoting the date of sampling and the result.
      3. Husbandry supervisors will monitor the movement of animals through biocontainment and will adjust their treatment modality, if needed, to maintain continuous therapy.
      4. Notify faculty veterinarians of any transfers that occur involving animals on alternative treatment protocols.
    6. Technical Services Team (TST)
      1. Administer treatments of mice in those labs that are permitted to use topical moxidectin as an alternative therapy.
      2. Perform PCR sampling of special quarantine colonies at beginning and end of quarantine period and submit to ADL.
      3. Perform follow-up fur plucks on breeding colony and those colonies receiving alternative therapies and submit to ADL.
    7. IVAC-ADL
      1. Post results of diagnostic testing (PCR and fur plucks) on C-Tools for dissemination to faculty and staff.
      2. The IVAC manager will maintain the Special Circumstances Database including the location of any egg-positive cases.
    8. RHST
      1. Collect ceca from sentinels for colonies receiving moxidectin or MiteArrest treatments and those in quarantine in situ.
  • Glossary Definitions

    Intra-quarantine Study Termination (IQST)

    Special exemption from campus-wide fur mite treatment; animals undergo non-treatment quarantine during campus-wide fur mite treatment. The room they are housed in is depopulated and cleaned by June 1, 2012.

    Import Quarantine (IQ)

    Standard ten-week quarantine procedures.

    Quarantine In situ (QIS)

    Special exemption from campus-wide fur mite treatment; animals remain housed in their fixed locations through campus-wide fur mite treatment and are subjected to specific testing requirements to prevent re-infestation of campus. Details are provided below. 

    Table 1: Fur Mite Species Differences

       Fur Mite Species   

       Life Cycle   


       Species Infected   

       Myocoptes musculinus   

       14 days   

       3rd and 4th legs heavily chitinized;   
       Eggs occupy ½ of abdomen   


       Myobia musculi   

       21-23 days   

       Single claw on 2nd digit   

       Mice and Rat   

       Radfordia affinis   

       Similar M. musculi   

       Two claws on 2nd digit (unequal length)   

       Mice and Rat   

       Radfordia ensifera   

       Similar M. musculi   

       Two claws on 2nd digit (equal length)   


    Table 2: Treatment Summary

       Treatment Drug   



       Cage Labeling   

       Ivermectin Chow   

       12ppm ad lib   

       Continuously for 8 weeks   


       Ivermectin Water   

       12ppm ad lib   
       0.28cc / 8oz of water   
       1.2cc / L of water   

       Continuously for 8 weeks   

       Yellow acetate with green label   
       indicating ivermectin water   

       Moxidectin (topical)   

       Mouse - 3Dl   
       Rat - 10Dl   

       Application on days 1 and 10   

       Yellow acetate with green label   
       for recording 2 treatment dates   


       Cotton balls per animal:   
       Mouse - 2   
       Rat - 5   

       8 weeks with weekly change   

       Yellow acetate with green label   
       for recording 8 placement dates   

  • Procedures

    1. Transfers

    1. If animals actively receiving alternative therapies (moxidectin or MiteArrest) are transferred between PIs or rooms, the husbandry supervisors will notify the area faculty veterinarians so that continuity of treatment can be ensured.
    2. Treatments of animals moving into and out of biocontainment will be handled by the area husbandry supervisors.
    3. Husbandry supervisors will notify the faculty veterinarian anytime animals are transferred between labs receiving moxidectin or MiteArrest. Any changes will be communicated to the IVAC manager for inclusion in the Special Circumstances Database.
    4. Transfers between labs that involve a change between ivermectin chow and ivermectin water will be facilitated by the husbandry supervisor.

    2. Treatment Options

    1. Ivermectin: compounded chow (Standard therapy)
      1. The rodent chow is a specially compounded version of one of the following diets - 5LOD or 50083 (ULAM areas) or 5001 or 5008 (LS&A areas) that contains 12 ppm ivermectin and blue dye for identification purposes.
      2. Ivermectin chow is the default method for campus-wide treatment of animals without special dietary requirements. Alternative therapies, other than special diets, are permitted only after review and at the discretion of the faculty veterinarian for the area.
      3. Compounded chow is provided in each room in place of regular food and must be kept in a closed container and protected from light to prevent deterioration.
      4. Ivermectin chow should be fed exclusively for 8 consecutive weeks. This excludes only those labs or cages that have made prior arrangements with the area veterinary faculty member.
      5. During the 8 week treatment course all other cage changing and food handling procedures will be followed normally.
      6. At the end of the treatment period all ivermectin chow will be removed and replaced with standard maintenance rodent chow.
    2. Ivermectin: administration in drinking water (Default standard therapy for animals of special diets)
      1. Ivermectin may be administered in the water when an alteration in the diet could have adverse impact on the study. This will be the default treatment for those animals on special diets that have not coordinated with a faculty veterinarian to use one of the alternative medications.
      2. 1.2 ml of ivermectin injectable solution (1%) is added to 1 liter of drinking water to produce a 12ppm solution. When water bottles are used add 0.28 cc of ivermectin for each 8oz of water (0.56 cc for 16oz bottles). NOTE: This is an increase from previous doses used at ULAM to treat fur mites.
      3. Ivermectin water may be administered in bottles or in a carboy for whole rack administration. When placed on top of rack mounted blowers, carboys should be placed into plastic bags so that water does not leak onto the blower.
      4. Water bottles will be changed at least once weekly in all mouse cages.
    3. Topical Moxidectin (Alternative therapy)
      1. Moxidectin treatment will be performed by the Technical Services Team.
      2. 3 Dl of topical moxidectin (0.5% Cydectin) is applied to the skin on the dorsum of each mouse between the scapulae. A dose of 10 Dl will be used in rats.
      3. This will be repeated once, 10 days following the first treatment.
    4. MiteArrest (Alternative therapy)
      1. MiteArrest is an insecticidal called permethrin delivered as a dried solution in cotton balls that are directly placed into the cage by the husbandry staff.
      2. 2 cotton balls per mouse (5 cotton balls per rat) are placed in each cage to start the treatment.
      3. The old cotton balls are replaced once per week by fresh cotton balls.
      4. Treatment period is 8 weeks total.
      5. It is normal and acceptable for the mice to use these cotton balls as nesting material - the contact time between bedding and mouse fur is necessary for elimination of the mites.

    3. Quarantine in situ Procedures

    1. After consultation with a faculty veterinarian, PIs may have the option of avoiding treatment of their colony by consenting to testing and a period of quarantine in their current room (in situ).
      1. During quarantine in situ, animals are not permitted to utilize shared use areas.
      2. RHST will be notified of any animals utilizing these quarantine procedures so that they can collect sentinel ceca.
    2. Upon initiation of quarantine in situ, animals will be PCR-tested for fur mites.
      1. If all samples are negative, animals will continue with a 10 week quarantine procedure. Animals will be fed standard rodent diet and will not be able to utilize shared use areas during this time.
      2. If any sample is positive, all animals will begin 8 week ivermectin treatment or alternative therapy for fur mites after consultation with the faculty veterinarian.
        1. These animals are no longer considered to be in quarantine in situ and are handled according to standard treatment and follow-up procedures.
    3. If the initial PCR samples for fur mites were negative, a second set of PCR samples will be obtained and submitted for fur mite detection before release from quarantine. These samples will be taken between weeks 8 and 10 of quarantine. Animals will not be released prior to results.
      1. If the second set of PCR samples are negative, animals will be considered free of fur mites and may be released from quarantine in situ.
      2. If the second set of PCR samples are positive, all animals will begin 8 weeks of ivermectin treatment or alternative therapy for fur mites after consultation with the faculty veterinarian.
        1. These animals are no longer considered to be in quarantine in situ and are handled according to standard treatment and follow-up procedures.
    4. See Appendix A for a flow chart version of the process outlined above.

    4. Retesting of Treated Colonies

    In lieu of retesting of the entire campus, treatment efficacy will be established by selective testing of the breeding colony and those cases that were granted special circumstances.

    1. Timeline
      1. Eight weeks after the treatment is finished, the initial fur pluck will be performed.
        1. If adults are found, the faculty veterinarian will be consulted to discuss additional options such as colony rederivation or ivermectin treatment if an alternative therapy was used initially.
        2. If eggs are found, the colony should be retested by fur pluck in 6 months. Egg positive cages will be tagged by the area husbandry supervisor with a red Post-It tab that includes the date of testing. Repeat the process (b) and (c) based on the results.
        3. If neither adults nor eggs are found, the colony is considered 'fur mite free'.
      2. All animals receiving alternative therapy (Moxidectin or MiteArrest) will be retested for fur mites at 9 months post-treatment.
    2. Fur Pluck
      1. Follow-up fur plucks are most accurate when conducted 8 weeks post- treatment.
      2. It is best to test mice 4-8 weeks of age or adult female mice during post- treatment assessment. Every mouse in the cage must be tested.
      3. Historically, 20% of the colony was plucked to test the efficacy of the treatment. However, this percentage may be altered at the discretion of the faculty veterinarian.
    3. PCR Testing
      1. If re-testing for fur mites is conducted via PCR, cage swabs are ideal. Ten cages can be swabbed for one pooled PCR test.
      2. It is best to test cages at 16 weeks post-treatment.
      3. All cages or a percentage of cages in a colony will be tested at the discretion of the faculty veterinarian.
  • Additional Resources

    1. Policy for Surveillance of Rat and Mice Ectoparasites (external link / should be migrated into A to Z)
    2. Fur Mite Outbreak and Treatment Procedures for Rats and Mice (external link / should be migrated into A to Z)
  • Appendix A: Quarantine in situ Flow Chart

Species: Mice Rats

Questions or concerns about the content of this document should be directed to the Unit for Laboratory Animal Medicine (ULAM) at (734) 764-0277 or