Lecture 30: Infections of Musculoskeletal System 1

what pathogen causes lyme disease?

borrelia burgdorferi

characteristics of borrelia burgdorferi

• 0.2-0.5 um wide and 2-30 um long

• gram negative

• obligate pathogens in a variety of vertebrate hosts

true or false: borrelia are longer and wider than other spirochetes.

true

what reveals the spirals and motility of borrelia burgdorferi?

dark field examination

spirochetes of borrelia burgdorferi are transmitted and maintained by

ticks

what is the most prevalent vector-borne disease in the Northern hemisphere?

lyme disease

lifecycle of ixodes scapularis

1. adult females drop off host to lay eggs

2. eggs hatch into larvae

3. larvae attach to and feed on first host (rodent)

4. larvae turn into nymphs after leaving first host

   1. infected nymphs feed on humans

5. nymphs attach to and feed on second host (rodent)

6. nymphs turn into adults after leaving second host

   1. infected adults feed on dogs

7. adults attach to their host for feeding

early localized stage of lyme disease in humans

• 3-30 days post tick bite

• red, expanding rash: erythema migrans

• fatigue, chills, fever, headache, muscle and joint aches, and swollen lymph nodes

early disseminated stage of lyme disease in humans

• days to weeks post-tick bite

• facial or bell’s palsy

• severe headaches and neck stiffness

• pain and swelling in the large joints

• shooting pains that may interfere with sleep

late disseminated stage of lyme disease in humans

• months to years post tick bite

• arthritis with severe joint pain and swelling

• up to 5% of untreated patients may develop chronic neurological complaints months to years after infection

lyme disease in dogs

• 70-90% of all dogs in endemic areas are seropositive

• clinical signs are observed in <10% of exposed dogs

• clinical illness is seen 2-5 months after tick exposure

• clinical syndrome → polyarthritis and glomerulopathy

lyme arthritis clinical signs

• fever

• shifting leg lameness

• articular swelling

• polyarthritis

• lymphadenomegaly

• anorexia

• general malaise

lymph nephritis clinical signs

• sudden onset of anorexia, vomiting, lethargy, and weight loss

• uremia, hyperphosphatemia, and severe protein-losing nephropathy

• lodging of immune complexes in kidneys

• labs, golden retrievers, and bernese mountain dogs

lyme disease in horses

• 50% of all horses in endemic areas are seropositive

• clinical signs are observed in <10% of exposed horses

clinical signs of lyme disease in horses

• chronic weight loss, sporadic lameness, shifting leg lameness, low-grade fever, muscle tenderness, poor performance, swollen joints

• changes in behavior and skin sensitivity, both with rapid onset

• neurological signs → depression, dysphagia, head tilt and encephalitis were reported in chronic cases

clinical lab findings for lyme disease

• no specific hematologic or biochemical changes are pathognomonic of borreliosis

• if a dog in a lyme endemic area has leukopenia or thrombocytopenia → caused by co-infection

• synovial fluids of lyme arthritic dogs have increased cell counts

serological testing of lyme

• seropositivity = exposure

• whole-cell ELISA

• C6 peptide based assays

• multiplex assay

whole-cell ELISA

• antibody measurements using whole spirochetes

• cross-reactivity with leptospira-positive sera

whole cell-immunoblotting

helps identify sera that produce false-positive results in whole-spirochete assays

C6-peptide based assays

• detect antibodies against C6-peptide

• can differentiate between vaccinated and naturally infected dogs

• does not react with sera from healthy dogs or infected with other diseases

C6-peptide based commercial assays

• SNAP 4Dx plus test

• lyme quant C6 test

treatment and control of lyme disease

• acute cases responds to beta-lactams and tetracyclines

• chronic cases require longer therapy

• tick control

• vaccines, bacterins, and subunit vaccines available

• important tick-borne disease for humans

prevention of lyme by tick control in dogs

• collars

• topical powders, shampoos

• daily combing and tick removal

prevention of lyme by tick control in the environment

targeting mice population

prevention of lyme disease by vaccines

• recombinant, subunit vaccine

• killed, whole-cell, bivalent bacterin