Eliminating Chronic Disease Using a Farmbased Approach: Caseous Lymphadenitis (CL)

SARE Farmer Grant Final Report 2014

By Anne Lichtenwalner DVM Ph.D., University of Maine Cooperative Extension, and Animal and Veterinary Sciences

CL: What is it?

  1. “Cheesy gland”: Chronic bacterial infection Corynebacterium pseudotuberculosis
    • Stays in the immune system
    • May cause skin or internal abscesses
  2. Can be spread from animal to animal:
    • Must have skin penetration
  3. graphic of the location of lymph nodes on a goat
    The location of lymph nodes on a goat.

    Persistent in the environment

  4. Use antibody response to test for the presence of bacteria in unvaccinated animals
  5. Vaccines are available; not highly effective

Corynebacterium pseudotuberculosis: lymph nodes

  1. External: Firm, dry abscesses- slow to develop
  2. Internal: Weight loss, coughing

CL: Internal abscesses (goat at necropsy)

Chest wall lifted away from lungs to show inflammation due to CL abscess.
Chest wall lifted away from lungs to show inflammation due to CL abscess.
Lung tissue with CL internal abscess (opened) showing dry exudate.
Lung tissue with CL internal abscess (opened) showing dry exudate.

CL: How contagious is it?

Transmissibility

  • Direct inoculation of bacteria into new host
    • Cut or ulcer, contact with exudate
    • Bites from flies that have contacted exudate
    • Rubbing on a tree, etc. that has exudate on it
  • Inhalation of infected secretions
    • Sheep with bronchial lymph node abscesses: coughing
  • Milk?
    • If mammary lymph infections present
    • See more recent info (below)

Treatment

  • Vaccines or antitoxins:
    • Don’t prevent or cure, but may decrease abscesses
  • Immune clearance ineffective
    • Toxins overcome normal immune defenses
  • “Hides out” inside cells
    • Uptaken by macrophages; survives and is spread to lymph nodes
  • Antibiotics
    • In vitro, many are effective
    • In vivo, nothing works: food animal limitations re antibiotics
  • Rifampin with tetracycline was useful in early infection

Sources:
Judson et al, 1991. Veterinary Microbiology 27(2): 145-150.
Senturk and Temizel, 2006. Veterinary Record 159(7): 216-217

CL: How long does it last on my farm?

Non-spore former, but environmentally stable

  • C. pseudotuberculosis wasn’t killed by 4 months in soil samples containing exudate from CL abscesses, and after 11 months in sterilized soil samples (40º F, 72º F, 98 º F and ambient conditions).
  • C. pseudotuberculosis was killed after 3 hours in chlorinated tap water but could survive up to 70 hours in distilled water.
  • Disinfectants: many are effective against CL after a thorough cleaning of surfaces. However: rough surfaces such as wood may be impossible to disinfect.

a hand holding up a petri dishCL: Can I detect or prevent it?

Detection

  • Exposed animals: PLD antibodies
    • Test-based on detecting antibodies
    • “Seropositives” carry the bacteria

Prevention

  • Vaccines not 100% effective
    • Boosters, accurate records needed
    • Vaccine will NOT cure, only help prevent abscesses
    • Using vaccine creates “seropositives”
  • Testing and culling seropositives: best method
    • But will this work for all farms?

Trial Methods

SARE Grant: CL in Sheep

  • Visit farm: use farm vet if possible
  • Test sheep: 0 and at least 60 days
  • Initial SHI tests were done by Washington State University
  • Report results (farm ID confidential)
  • Consultation
    • Biosecurity
    • Tailor methods to farm type
    • Survey
  • SHI test method developed at UMaine lab in Orono
    • Supports local industry
    • Create easier access to vigilance methods
    • Validate CL-free status for producers

Farm types tested

  • Breeds: Many
  • Products: Fiber, meat, milk
  • Biosecurity: Varied greatly

CL status

  • 8 of 17 had positive animals at first test (47%)
    • 22% of 705 sheep tested at least once were CL+
  • 8 of 9 negative farms stayed negative (1 didn’t retest). Closed herd and good biosecurity essential
  • Inability to run test locally interfered with outcome
  • At follow-up, most of the positive farms had culled or isolated positive animals

Biosecurity: example (Farm 2)

  • Breeding for fiber and meat: Animals may travel off farm: limited or no quarantine
  • Tested “home” animals: all neg.
  • Tested “returned” animals: 1 pos.
  • Retested “home” animals: new positive

Followup: culled all positives, implemented quarantine procedures for returning animals

Trial Results

Farmer compliance

  • All farmers directly contacted said they would cull
    • Follow-through really varied. “Favorites” or great producers were unlikely to be culled.
  • Most were unwilling to replace wooden feeders or other areas where CL transmission likely.
  • Most thought their biosecurity was excellent
  • All were highly concerned and involved in the success of their flocks
  • Some of the 17 farms had camelids; none had goats

Farmers resented “buying” chronic disease

  • “Do unto others” was a strong motive

Conclusions

  • Prevalence higher than expected
  • Does being CL-free add to value?
    • “Caveat emptor”: Selling CL free breeding stock=value
  • Other species affected: goats, camelids
    • Be careful of guard animals: need testing, too
  • Farm type dictates whether vaccination ok
    • Reluctance to cull is common
    • Vaccination takes away possibility of testing
    • No strategy works longterm without culling
  • Biosecurity and determination dictate whether disease-free status is achievable

Outcomes

  • Awareness of CL increased
    • Added value of CL-free status
  • Biosecurity templates in development
    • Google Earth model may help communications about farm layout and biosecurity
  • SHI method now in Orono on a research basis
    • Project continuing studying goat dairies in 2014-5
    • Sheep testing available in 2015 if serum samples can be collected/shipped to UMAHL (no charge for testing)
  • Decision Tree: Start by knowing your status
    • Assess the cost of CL-free status for your farm
    • May not work for everyone

Outcomes: Recommendations

  • Know the CL status of your flock: retest as needed
  • Maintain closed flock/herd with high biosecurity
    • Notify visitors about biosecurity
    • Inform shearers about biosecurity
    • New or returning animals:
      • Don’t immediately mix with “home” flock
        • “nose to nose H quaranIne”
      • CL test immediately at entry and prior to release from quarantine (2 mo. later)
        • If positive, cull or sequester positives

» Retest exposed animals at 2 months: cull if +
» Keep quarantined until all negative for CL at 2 consecutive tests 2 months apart

Outcomes: Decision Tree

Decision Tree: New animal to CL- flock: genetics needed? Is source flock CL+? Yes: Don’t buy or Quarantine and test at entry and 2 mo. No: Quarantine and test at entry and 2 mo.

Outcomes: Decision Tree

Decision Tree: CL+ at end of quarantine? Yes: Slaughter or Sequester No shared spaces, feed, water, equipment; AI only (if a ram). No: Add to group Keep CL- via good biosecurity.

Impacts

  • Stopped CL on several farms
    • Estimated 20% improvement in fiber yields
    • Potentially reduced carcass condemnation
  • Outreach to SR vets
    • Free testing may enhance communications
    • Help establish VCPR with farmers
  • Farmer-to-farmer:
    • Added value of CL-free stock
    • Building biosecurity awareness
  • Students
    • projects and experience

Recent Undergrad Student Theses on SR

  • Edith Kershner: Case study of sheep farms with or without CL.
  • Abigail Royer: Detecting CL using complete blood counts.
  • Amy Fish: Evaluating macrophage responses to CL.
  • Rachel Chase: Evaluating neutrophil responses to CL.
  • Cassandra Karcs: CL prevention in small ruminants.
  • Hallie Lipinski: CL and its connection to milk.
  • Anna Desmarais: Selenium and footrot prevalence.
  • Alden West: Composting effects on coccidia.
  • Alexandra Settele: Anthelmintic resistance in H. contortus
  • Amanda Chaney: Identification of internal parasites of sheep and goats
  • Caitlin Minutolo: Effect of age on susceptibility to ovine footrot.
  • Nicole Maher: CL webinar for producers
  • Casey Athanas: Pedigree analysis to help eradicate footrot.
  • Katrina Glaude: Should sheep with footrot be culled?
  • Kayla Porcelli: Biosecurity survey for footrot positive farms
  • Marie Smith: Pasture management to control parasites in small ruminants.

References

  • Sheep and Goat, Wool and Mohair: 1982. Research reports, Texas A and M University.
    • Augustine JL and Renshaw HW. Longevity of C. pseudotuberculosis in six Texas soils. P 102
    • Augustine JL, Richards AB, Renshaw HW. Persistence of C. pseudotuberculosis in water from various sources. P 104.
  • Assis RA, Lobato FCF, Martins NE, et al. Clostridial myonecrosis in sheep after caseous lymphadenitis vaccination. The Veterinary Record 2004;154:380-380.
  • Paton MW, Walker SB, Rose IR, et al. Prevalence of caseous lymphadenitis and usage of caseous lymphadenitis vaccines in sheep flocks. Australian Veterinary Journal 2003;81:91-95.
  • Fontaine MC, Baird G, Connor KM, et al. Vaccination confers significant protection of sheep against infection with a virulent United Kingdom strain of Corynebacterium pseudotuberculosis. Vaccine 2006;24:5986-5996.
  • Baird GJ, Malone FE. Control of caseous lymphadenitis in six sheep flocks using clinical examination and regular ELISA testing. The Veterinary Record 2010;166:358- 362.
  • Washburn KE, Bissett WT, Fajt VR, et al. Comparison of three treatment regimens for sheep and goats with caseous lymphadenitis. Journal Of The American Veterinary Medical Association 2009;234:1162-1166.

Acknowledgements

  • Collaborating Farmers of Maine
  • Collaborating Veterinarians:
    • Drs. Becky Myers Law and colleagues
    • Dr. Tammy Doughty
    • Dr. Don McLean
    • Dr. Beth McEvoy
  • NE SARE: Carol Delaney
  • Extension colleagues: Richard Brzozowski and Donna Coffin
  • Technical/lab assistance:
    • Edith Kershner, Anne Ryan, Hallie Lipinski, Abbie Royer
    • Ann Bryant
  • University of Maine Cooperative Extension
  • University of Maine School of Food and Agriculture