Procedures for Sheep Research Facility Parasite Management

Unit for Laboratory Animal Medicine
Dec 1, 2012 12:00 am

To describe the methods of management and screening for internal parasites in University of Michigan sheep housed at the Sheep Research Facility (SRF).

  • Responsibility

    1. Sheep Research Facility Manager: Responsible for scheduling and conducting prophylactic anthelmintic administration, collection of parasite screening fecal samples, and daily monitoring for signs of animal parasitism.
    2. ULAM Veterinary Staff: Responsible for submission of fecal samples to the Animal Diagnostic Laboratory (ADL), filing of ADL results, and prescription of dewormer based on FAMACHA system in clinical cases.
  • Glossary Definitions


    A pharmaceutical used to destroy and eliminate intestinal parasites.

    Anthelmintic Resistance

    A term used to describe an intestinal parasite which is not 90% cleared following treatment with a specific anthelmintic.


    A visual system using the color of the conjunctiva of sheep to assess the need for deworming, via the severity of anemia, to aid in prevention of anthelmintic resistance.

    McMaster Test

    A diagnostic method to provide quantification of intestinal parasite eggs in feces, reported as eggs per gram (EPG).

  • Procedures

    1. Selection of Anthelmintics

    1. The following table summarizes the anthelmintic coverage provided by the different classes of anthelmintic drugs: 
         Life Stage   
         Haemonchus contortus   
         +/- (most)   
         Ostertagia circumcincta   
         +/- (some)   
         Trichostrongylus spp.   
         Lung Worms   
         Nasal Bots   
       Table adopted from University of Georgia and Ft. Valley College Cooperative Extenstion
       a Do not administer albendazole to pregnant ewes within the first 45 days of gestation.
       b Levamiso can be toxic if given at greater than 25% of the recommended dose. Contact a veterinarian if clinical signs, such as foaming at the mouth and tremors are observed.
    2. Three classes of anthelmintics, represented by albendazole, ivermectin, and levamisol will be utilized. One anthelmintic will be preferred for deworming and rotated annually. Additionally, based on spectrum variation between annual anthelmintics, as described above, different anthelmintics will be used for the winter and spring/fall dewormings. The following chart outlines the anthelmintic regimen:
         Winter Deworming   
         Spring / Fall   
         Ivermectin / Levamisol   
    3. Moxidectin, or combination anthelmintic treatment, will be used to treat resistant populations of parasites and its use will be reserved for treatment of sheep with resistant parasites.

    2. Prophylactic Anthelmintics

    1. New arrivals
      1. All new arrivals will be dewormed with the preferred anthelmintic upon intake into the Sheep Research Facility and quarantined for 7-10 days. Any signs of parasitism must be reported to the veterinary resident for clinical assessment prior to release from quarantine.
    2. Breeding/Lambing/Weaning
      1. Breeding ewes and rams will be dewormed 2 weeks prior to breeding.
      2. Pregnant ewes will be dewormed 2 weeks prior to lambing season. If lambing season is greater than one month, late lambing ewes may receive a second deworming prior to lambing.
      3. Lambs will be dewormed at the time of weaning.
    3. Pasture animals (adults only)
      1. All pasture animals will be dewormed once in the winter months (November-April) and once between April and November, as outlined in the table above. This deworming is in addition to the breeding related dewormings previously described.
    4. Dry lot animals
      1. All dry lot animals will be dewormed once in the late fall/early winter with the annual preferred anthelmintic.
    5. If feasible, keep sheep off feed for 24 hours prior to oral anthelmintic treatment to prolong the presence of the anthelmintic in the digestive tract. Water should be provided ad libitum.

    3. Fecal Examinations

    1. Monthly examinations will be performed on feces randomly collected from 10% of the herd population in all locations (pasture & dry lot). These samples can be pooled together, based on location, to form 3-5 representative samples.
      1. If sample collection corresponds with a scheduled prophylactic deworming, the fecal samples must be collected prior to the deworming.
    2. Fecal samples will be submitted to the Animal Diagnostic Laboratory by the ULAM veterinary staff.
      1. The ULAM veterinary staff is responsible for filing electronic copies of fecal examination results from the Animal Diagnostic Laboratory (ADL) on the ULAM Bluestorage Drive:
        W:\ULAM_General-Veterinary\Sheep Farms\Sheep Research Farm\Parasites\Fecal Results
    3. The McMaster test will be utilized by the ADL for quantification of parasite burden.
      1. Nematodes >1000 EPG will be used to indicate additional clinical assessment is needed.
        1. Clinical assessment of the individual animal and/or herd will utilize the FAMACHA system to assess the severity of anemia. Housing environment and additional clinical signs of parasitism, such as poor growth, poor wool quality, ill-thrift, diarrhea, inappetance, or edema ('bottle jaw') will be used to determine when anthelmintic treatment is necessary.
          1. FAMACHA system - The FAMACHA scoring card is used to assess the color of the conjunctiva, and therefore potential anemia, of the sheep. A FAMACHA score of 3 or above indicates the need for anthelmintic treatment.
      2. If treatment is prescribed, a follow-up McMaster test will be completed 10-14 days post-anthelmintic treatment. Less than a 90% reduction in parasite load following anthelmintic treatment will be deemed as resistance.
        1. Moxidectin, or combination anthelmintic treatment, will be administered to animals in need of deworming with resistant parasites.

    4. Coccidiosis

    1. Coccidiosis will be diagnosed in sheep having >2000 coccidia per gram of feces with the presence of diarrhea.
    2. Options for coccidiosis treatment include sulfonamide, sulfaquinoxaline, or amprolium for a period of five days.
    3. A coccidiostat, such as monensin, lasalocid, or decoquinate, can be used regularly to reduce coccidia contamination of the environment.
      1. For pregnant ewes, the coccidiostat must be added to the diet at least 21 days prior to lambing to benefit the lambs.

    5. Recommended Anthelmintic Doses

    Always refer to the product label prior to administration of the anthelmintic

    1. Albendazole (Valbazen)
      1. Drench; 7.5 mg per 1 kg of body weight
        NOTE: Do not administer Albendazole to pregnant ewes within the first the first 45 days of gestation as the drug is known to be a teratogen during this stage of gestation.
    2. Moxidectin (Cydectin) (5mg/ml)
      1. Dosage: 5 ml per 110 lbs (1 ml per 22 lbs) body wt orally
    3. Ivermectin (Ivomec)
      1. 3ml/26 lbs when given by drench
      2. 1cc/110# (200ug/kg) when administered by SQ injection
    4. Levamisol (Tramisol)
      1. Drench; mix 544.5 g bottle in 3 liters of drinking water and administer as single drench at 1 ml (0.365 g)/50 lb body weight.
    5. Sulfonamide/Sulfadimethoxine (Albon)
      1. Day 1- drench; 25 mg/lb (55mg/kg)
      2. Days 2 to 5- drench; 12.5 mg/lb (27 mg/kg)
    6. Sulfaquinoxaline
      1. 20% solution; Mix in drinking water to final concentration of 0.015%
    7. Amprolium (Corid)
      1. 1.25% crumble, 9.6% solution, or 20% soluble powder; 50mg/kg
    8. Monensin (Rumensin)
      1. Feed additive; 1 mg/kg
    9. Lasalocid
      1. Feed additive; 1 mg/kg for 6 weeks
    10. Decoquinate
      1. Feed additive; .5 mg/kg for 28 days
  • References

    1. Maryland's Small Ruminant Page
      2. Medicine Cabinet for Sheep and Goat Producers
      3. Coccidiosis in lambs - Michigan State University
    2. University of Nebraska-Lincoln
      2. Cooperative Extension
    3. Government of Alberta
      1. (Dr. Des Hennessy, CSIRO Animal Production Center)
Species: Sheep

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