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(Lyme arthritis, Bannworth's syndrome, tick-borne meningopolyneuritis, erythema chronicum migrans [ECM], Steere's disease)
Spirochete, Borrelia burgdorferi
RESERVOIR AND INCIDENCE
First implicated in 1982 as agent in a 1975 epidemic of juvenile inflammatory arthropathy in Old Lyme, Connecticut. Cases have been reported from 46 states and the annual number of Lyme disease cases has increased 18 fold from 497 to 8803. It is now the most common tick transmitted disease in the USA. Also seen in Europe, England, Soviet Union, China, Japan, Southeast Asia, South Africa, Australia, and Canada.
Transmitted mostly by Ixodes dammini and other ixodid ticks (three host tick with a two to three year life cycle). Ixodes dammini has a broad range of hosts; adults prefer white tailed deer but will also parasitize dogs, horses, and humans. Larvae feed primarily on rodents, especially mice. Nymphs feed on all hosts and appears to be primarily responsible for transmission of the disease to people. Birds are an important reservoir and means of dispersal. Also found in Dermacentor, Rhipicephalus and Amblyomma and other ticks and biting insects, including mosquitoes, fleas, and biting flies. Because of lack of any proof to the contrary it is generally believed at this time that any potential increased risk to human beings from infected animals is attributable to animals bringing ticks into areas of human habitation rather than any pet transmission. Dogs appear to be at greater risk than humans.
DISEASE IN ANIMALS:
Serologic evidence has been reported in the dog, cat, horse, and ruminants. However, correlation with disease is lacking except in the dog. The dog exhibits the same symptoms as noted below for humans. Expanding skin lesions have been noted in mice and rabbits.
DISEASE IN MAN:
Multisystemic disease which may have chronic sequelae; an annular rash known as erythema chronicum migrans (ECM) develops in 60-80% of patients in the area of the tick bite and is considered pathognomonic. Also flu like symptoms, which resolve in about three weeks. 8-10% of people develop cardiac involvement several weeks later. Manifestations include atrioventricular block, cardiomyopathy, heart failure, myocarditis, and pancarditis. 15% develop neurologic disorders such as facial nerve palsies which usually resolve. Other manifestations include meningitis, cranial neuritis, radiculoneuritis, neuropathy, and encephalopathy. 60% develop the most common sequelae, arthritis. Disease may remain latent with symptoms developing 4 years after seroconversion.
Most common test is detecting antibody titers by IFA or ELISA (on blood, CSF or synovial fluid). Culture is definitive but is difficult and requires special media such as Barbour-Stoener-Kelly media. Histologically with Dieterle Silver Stain or immunoperoxidase stains, but is often unrewarding.
A positive serology is no grounds for treatment when no clinical signs are present. Borrelia burgdorferi is sensitive to tetracycline and moderately sensitive to penicillin, amoxicillin, ceftriaxone, and imipenem are also highly active.
Tick control care when removing ticks or when handling potentially infective materials a vaccine against Lyme Disease tested in hamsters has been found effective. More research is needed but in the future vaccination may be beneficial for those at constant risk of exposure.