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LYME DISEASE: Current Trends in Diagnosing and Treating Horses LYME DISEASE: Current Trends in Diagnosing and Treating Horses Mark T. Reilly, DVM, Dipl.

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Presentation on theme: "LYME DISEASE: Current Trends in Diagnosing and Treating Horses LYME DISEASE: Current Trends in Diagnosing and Treating Horses Mark T. Reilly, DVM, Dipl."— Presentation transcript:

1 LYME DISEASE: Current Trends in Diagnosing and Treating Horses LYME DISEASE: Current Trends in Diagnosing and Treating Horses Mark T. Reilly, DVM, Dipl. ABVP (Equine) Equine Affaire 12 Nov 2009 South Shore Equine Clinic & Diagnostic Center www.southshoreequineclinic.com781-585-2611


3 LYME DISEASE 1975 – 51 residents from Old Lyme, Lyme and East Haddam, CT 1982 – Willy Burdorfer, PhD discovered slender, spirally undulating bacteria from blacklegged tick (Ixodes dammini -> scapularis)

4 LYME DISEASE Erythema Migrans

5 LYME DISEASE 1983 – spirochete named Borrelia burdorferi Borrelia burdorferi 1984 – First case of canine Lyme arthritis reported

6 LYME DISEASE The CDC reported that Lyme disease accounted for 81% of all reports of arthropod- transmitted diseases in the US between 1986 – 1991.


8 LYME DISEASE 2000 – “Might not be the most prevalent equine disease you face with your horses, but it does exist, and can seriously impact a horse’s health. Although documented cases of Lyme disease in horses are relatively rare, there are indications that the disease is on the increase.”

9 LYME DISEASE 2003 – “50% of horses in the Northeast US are positive for exposure.” - Successful treatment of Lyme infected horses (Oxytetracyline) - rDNA canine vaccine success in ponies

10 LYME DISEASE 2004 – “Up to 50% of adult horses in the northeast may be infected.”

11 LYME DISEASE 2005 – “Lyme disease is a problem more commonly thought to occur in our canine and human friends. However, it does occur (in horses) and can have a wide range of signs and symptoms.”

12 LYME DISEASE 2006 – “As many as 20% of adult horses in certain areas of the US are infected with Borrelia burdorferi. Many horses in endemic areas are, or have been, infected, which is evidenced by the fact that 75% of horses in the Northeast and Mid-Atlantic states already have antibodies against the organism.”

13 LYME DISEASE Human cases parallel animal cases 1982 – 523 cases 1988 – 4,507 cases 1989 – 8,552 cases 1994 – 13,043 cases 2003 – 1,503 cases in MA 2004 – 1,532 cases in MA 2005 – 23,300 cases (2,336 cases in MA)

14 LYME DISEASE 23,300 human cases in 2005 23,300 human cases in 2005 = 7.9 per 100,000 nationally =31.6 per 100,000 in the ten states where infection is most common = 50% increase in MA (18% nationally)

15 LYME DISEASE US Department of Health and Human Services has included Lyme disease among its prevention priorities. Goal of reducing the overall incidence by more than 40% in endemic areas by 2010.


17 Horses are more likely to have a higher prevalence than humans because ticks stay on longer.

18 The chances of your horse in the northeast being infected with Lyme disease may be 25 times greater than horses in other parts of the country. Found in 44 states, Canada, Europe, Asia, Africa, Japan, Australia

19 LYME DISEASE Ixodes scapularis (“deer tick”)

20 LYME DISEASE LIFE CYCLE LARVALNYMPHADULT Each feeding stage requires one vertebrate blood meal for its development

21 LYME DISEASE LARVAE –Size of a grain of sand –6-legged –May & August –Need high humidity –Rarely infected –Need host for blood meal (*Small mammals*) (*Small mammals*) –Feed for 3-5 days –Leaf litter for metamorphosis

22 LYME DISEASE NYMPH –Size of a poppy seed –8-legged –May-August –Need host for blood meal –Easily undetected –2 nd chance to become infected –Leaf litter for metamorphasis

23 LYME DISEASE ADULT –Fall –> Spring when >40 degrees –Feed on large mammals –Female drops off and lays eggs (3,000) –** 48 hours**


25 TRANSMISSION of DISEASE Via Salivation or Regurgitation of tick to host Minimum of 24 -48 hours of tick attachment Nymph >>> Adult stages (50% adults infected) (50% adults infected)


27 LIFE STAGES 1. Larvae 2. Nymph 3. Adult male 4. Adult female

28 LYME DISEASE VAGUE & VARIABLE SIGNS: VAGUE & VARIABLE SIGNS:Stiffness/lameness Muscle tenderness Hyperaesthesia (sensitivity) Swollen/sore joints Behavioral changes –Lethargic, “grumpy”

29 LYME DISEASE SIGNS MAY MIMIC OTHER DISEASES Aches, fatigue – viral infection Joint pain – arthritis Weakness – neuro diseases (EPM) Muscle soreness – tying up

30 LYME DISEASE A DIFFICULT DIAGNOSIS Most common complaint: “OFF” Often no history of tick infestation OR may take a few weeks to develop clinical signs after tick bite May be episodic OR chronic Forelimbs, Hindlimbs, Pelvis

31 LYME DISEASE DIAGNOSIS Submission of infected tick Blood Tests –IFA antibody –ELISA (Kela) –Western Blot –C6 antibody ELISA


33 ANTIBODY TESTS IFA –patient’s serum placed on antigen- coated slide and then add anti-body conjugate –Titer – must be interpreted –Whole-cell method

34 LYME DISEASE ANTIBODY TESTS ELISA (Kela units) –IgG level reported –Chronic infection – 380 –Whole-cell method

35 LYME DISEASE ANTIBODY TESTS WESTERN BLOT –Need all 4 Bands = specific markers –4 day test –$$$ –Whole cell method –Inconclusive results

36 LYME DISEASE ANTIBODY TESTS C 6 ANTIBODY TEST –3 weeks post-infection –100% consistent with Western Blot –C 6 Peptide is highly specific & ONLY present during LIVE infection –Declines rapidly and significantly after successful therapy –Highly sensitive & specific

37 LYME DISEASE ANTIBODY TESTS C 6 ANTIBODY (SNAP TEST) –164 samples tested (6 had been vaccinated) WB: 106 positive SNAP: 109 positive (1 negative and 2 had 1:64 low titer on IFA) -100% sensitive (able to find) -95% specific (truly infected)

38 LYME DISEASE ANTIBODY TESTS C 6 ANTIBODY TEST –Variable region on the spirochete




42 ANTIBIOTICS Study done at Cornell - Doxycycline orally – 25-50% effective - Naxcel IM – 25 % effective - Oxytetracycline IV – 100% effective

43 LYME DISEASE OXYTETRACYLCINE IV daily for 3 weeks Superior to oral Doxy and IM Naxcel Retest at 60 post treatment C 6 Antibody tests dropped by at least 50%; if not completely

44 LYME DISEASE Other Antibiotics: (Doxy & Naxcel) Rise in titers and clinical signs when treatment is stopped in 75% of each group Appear to inhibit reproduction, not eradication of B.burdoferi Doxy has anti-inflammatory effects = false sense of improvement

45 LYME DISEASE OXYTETRACYLCINE Treatment at SSEC: IV once daily x 5-10 days Then switch to oral Oxytetracycline Powder & Probiotic Retest at 60 days post treatment

46 LYME DISEASE OXYTETRACYLCINE Treatment at SSEC: 896 Tested (4 years) 223 Positive =25% infected 202 Treated 94 Retested 73 Negative (so far) (78% success rate)

47 LYME DISEASE TESTED HORSES at SSEC: In last 15 months 335 Tested 100 Positive Lyme = 30% Prevalence of Lyme disease 14 Positive Anaplasma 22 Both Lyme & Anaplasma = 10% Prevalence of Anaplasmosis

48 LYME DISESASE See improvement in behavior Attitude & Lameness improves

49 LYME DISEASE PREVENTION rOSP canine vaccine 3 doses (day 1, 20, 80) Horse’s plasma has antibodies inhibits spirochete within the tick

50 LYME DISEASE PREVENTION rOSP canine vaccine Problems: frequency to vaccinate? no safety studies questionable value once infected

51 LYME DISEASE PREVENTIONDogs bring ticks in from woods roll in leaves & go into tick habitats 50% more likely to get disease act as sentinels for disease

52 LYME DISEASE PREVENTIONHORSES Examine on daily basis (24 hours) Neck, base of mane, ears, under tail fine tweezers as close to skin as possible and pull straight up Avoid tick infested areas Repellents with permethrins (sweat)

53 LYME DISEASE White footed mouse “the problem”

54 LYME DISEASE PREVENTION (“ the mouse”) - Clean up brush piles - Mow fields - Stack wood in dry areas - Restrict Tick migration - Bait boxes for wild rodents with acaracides (Field mice)

55 LYME DISEASE White-tailed Deer “the spreader”

56 LYME DISEASE PREVENTION -Do not feed deer -Do not feed deer - Plant deer resistant plants

57 LYME DISEASE White – footed mouse

58 LYME DISEASE PREVENTION??? - Vaccination of white-footed mice with canine vaccine - Prevented the tick from the spreading the disease to the next host - Measured a reduction in prevalence of disease in nymphs

59 LYME DISEASE MYTHS No evidence of transmission directly from animal to human Cannot get from urine of infected animal Cannot get from eating a tick or portion of mouse (in baled hay)

60 LYME DISEASE KEY POINTS 1. > 24 hour feeding 2. *** Clean up brush and debris *** 3. Control ticks on dog and cats 4. Use permethrin sprays 5. Good diagnostic test available 6. Treatable – very successfully 7. Re-infection always possible!

61 LYME DISEASE Thank you for your attention

62 LYME DISEASE Questions? Comments? Mark T. Reilly, DVM, Dipl ABVP (Equine)

63 REMINDER Upcoming client education seminars January - March January - March South Shore Equine Clinic & Diagnostic Center

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