Saratoga Equine Veterinary Service, P.C.

Bill Barnes, DVM MS

www.saratogaequine.com

Lyme Disease (Borrelia burgdorferi)

What we Know and Don’t Know

• Significant increase in the # of clinical cases (epidemic ?)

• Cause • Clinical signs• Diagnosis• Treatment• Prevention

Questions??

• How many species of ticks are in our area?• How can you tell if it is a deer tick?• Should we assume all ticks are deer ticks?• Do all deer tick bites lead to transmission

of Lyme Disease?

Cause of Lyme Disease Transmission

• Deer Ticks Transmit ion

• Spirochete Borrelia

burgdorferi

Sesame SeedReddish hind bodyWith black dorsal markings

Greater than 24 hrs. to infect

The storm is brewing…• Borrelia spp. was identified as the

cause of severe arthritis in children in Olde Lyme CT 1977 – disease was given the name “Lyme Disease”

• Deer tick identified as “vector” in 1982 (W. Burgdorfer)

• Considered “zoometric”; humans thought to be an “incidental” host.

• Thought to be restricted to a limited geographic area of the US.

Life Cycle of the Deer TickLife cycle of blacklegged ticksBlacklegged ticks live for two years and have three feeding stages: larvae, nymph, and adult. Tick eggs are laid in the spring and hatch as larvae in the summer. Larvae feed on mice, birds, and other small animals in the summer and early fall. When a young tick feeds on an infected animal, the tick takes bacteria into its body along with the blood meal, and it remains infected for the rest of its life. After this initial feeding, the larvae become inactive as they grow into nymphs. The following spring, nymphs seek blood meals in order to fuel their growth into adults. When the tick feeds again, it can transmit the bacterium to its new host. Usually the new host is another small rodent, but sometimes the new host is a human. Most cases of human illness occur in the late spring and summer when the tiny nymphs are most active and human outdoor activity is greatest. Adult ticks feed on large animals, and sometimes on humans. In the spring, adult female ticks lay their eggs on the ground, completing the life cycle. Although adult ticks often feed on deer, these animals do not become infected. Deer are nevertheless important in transporting ticks and maintaining tick populations.

Lyme Statistics (cdc.gov)

New York State 2008Incidence

29.5/100,000

50% of adult horses in N.E. are infected or have been infected1.Magarelli et al AVMA

Symptoms (ilads.org) The # of people we know infected?

• Fatigue• Low grade fevers, ‘hot flashes’ or chills• Night sweats• Sore throat• Swollen glands• Stiff neck• Migrating arthralgias, stiffness and, less commonly, frank arthritis• Myalgia• Chest pain and palpitations• Abdominal pain, nausea• Diarrhea• Sleep disturbance• Poor concentration and memory loss

• Irritability and mood swings• Depression• Back pain• Blurred vision and eye pain• Jaw pain• Testicular/pelvic pain• Tinnitus• Vertigo• Cranial nerve disturbance (facial

numbness, pain, tingling, palsy oroptic neuritis)

• Headaches• ‘Lightheadedness’• Dizziness

Lyme Disease Symptoms cdc.gov Acute disease vs. chronic

• First sign in 70-80% of infections is erythematic migrans (bulls-eye) rash, accompanied by fatigue, chills, fever, headache, swollen lymph nodes, muscle and joint pain

• If not treated, additional symptoms may occur such as muscle weakness, Bell’s palsy (facial paralysis), heart palpitations, migrating joint pain which usually resolve without treatment.

Clinical Signs of Lyme Disease

• Polyarthritis• Hyperathesia• Shifting Lameness• Nabulus• ADR

Diagnosis of Lyme Disease A Chronic Disease

• Screening, ELISA Snap Test• Western Blot• Antibody levels• Bacterial culture?

Serological Diagnosis of Equine Borreliosis: Evaluation of an In-Clinic Enzyme-Linked

Immunosorbent Assay (SNAP 4Dx)

• 100% specificity • 95% sensitivityCompared to a Lyme Western Blot testWhat does this mean?Doesn’t quantify antibody levels?Treat or not to treat? That is the question.

IDEXX Lab. 164 horses University of Conn. Study, 2008

How the Snap Test works

Western Blot Test

#

Time

Ticks carrying Borreliosis=redHorses with positive titers=yellowHorse antibody levels following treatment=orange

Many horse whose blood tests positive for exposure to the Borrelia burgdorferi bacteria do not have lyme disease. Compatible clinical signs must also be present for a diagnosis to be definitive

Here is the rub. Treatment in absence of a definitive diagnosis.Human vs horse. A/B levels low, treat or not to treat in presence of clinical signs. Clinical signs so difficult.

Lyme Elisa/ Western Blot Laboratory Test

0-128130-370>380

So what’s wrong with those criteria?

• My opinion: Case definition of infection should be made based on a lower antibody level in a chronic disease situation that we have in horses. Especially with the slightest clinical sign or history of previous infection

• Get aggressive! Why? The disease is devastating.

• Existing blood tests do not reliably indicate infection (reliability 65%) in humans.– Numerous reports in the scientific literature of culture-positive

but serology-negative cases of Lyme disease; largely ignored

Treatment of Lyme Disease

• IV Antibiotics– Oxytetracycline (10-15 mg/kg) Q 5-7 days

• Oral Antibiotics– Doxycycline (10-15 mg/kg) PO, BID, Q 30

daysCorrect Antibiotic?Alternatives?

Life After Treatment

• Monitor signs of stiffness, heat or swelling in/around joints or lameness

• Unexplained lameness• Recheck titer in 2 months• Reoccurrence of clinical signs are high• Question if disease isever totally eliminated

Prevention

• Monitor your horses often• Keep pastures mowed• Apply Frontline Spray, Fipronil• Vaccine?

Eliminate Rodents