LYME DISEASE

LYME Disease is a tick-borne spirochetal disease that is becoming important for a number of reasons. By not thinking of this possible diagnosis, one may easily overlook it in many areas: for instance, arthritic, neurological, cardiac, dermatology, autoimmune and some others. A firm diagnosis renders it susceptible to treatment by antibiotics. Left untreated, like the famous spirochete of syphilis or the Brucellosis epidemic in Ireland in the 1960's and 1970's, chronic ill health may ensue.

The main reason we in Ireland have to be aware of it is the explosion in travel of the general population, particularly to areas where Lyme disease is endemic. In the USA, Lyme disease is now the most common vector borne disease, reported in 45 states and endemic in more than 15. The highest rates occur in three distinct foci: Northeast U.S.A. from Maine to Maryland, Midwest in Wisconsin and Minnesota and in the West in Northern California and Oregon. Two of these areas are the most heavily visited by Irish people in the Boston, Chicago, New York triangle.

In Europe the highest incidence is in Middle Europe, particularly Germany, Austria and Switzerland - increasingly visited by Irish tourists. Pure native incidence of Lyme disease is low, mostly got in forestry workers or frequenters, but there are a number of cases described, including diaphragmatic neurological paralysis in a 39 year-old male after a camping holiday in Galway.

Lyme disease is caused by B.burgdorferi in U.S.A; and B.afzelii and B.garinii in Europe, all pathogenic species of Borrelia, a spirochetes-like organism. The complete genome of B.burgdorferi has now been sequenced. Ticks transmit the disease using deer and mice and dogs as vectors to humans. Most recently, birds have been positively implicated. In the worst areas of the USA, eg Lyme Connecticut or the Chicago area, the local incidence of the disease is 10 or more per 100 persons. American physicians are very familiar with its presentation and treat early, usually with Doxycycline 100mg BD for 3 to 4 weeks.

Clinical manifestations consist of a localised, slowly expanding skin lesion - Erythema migrans - which occurs at the site of the tick bite. This is an unusual sign for Irish GPs but almost pathgnomic of the disease. The original tick bite may be totally painless, particularly in a larval tick. The rash, usually in the midriff/upper leg area, is present usually 7 to 10 days after initial infection and is very distinctive being described typically as "doughnut" shaped and reaching a size of approximately 5cms. It is often accompanied by a flu-like syndrome and regional lymphadenopathy. As many as 80% of cases in the USA present this way. Once you have seen Erythema migrans you will never forget it. Remember "doughnut". If you see and feel that, in all probability it'sLyme disease.

Within weeks other signs may show-up. Fifteen per cent of cases get neurological involvement. Most common is facial palsy, but others such as myelitis, lymphocytic meningitis, cerebellar ataxia and, in children, optic neuritis which may lead to blindness . About 5% of cases will have acute cardiac involvement, mostly A/V block and, in chronic cases, cardiomyopathy. Months (2 - 6) after onset, 60% of cases develop intermittent joint pain and swelling, mostly large joints - especially the knee. In about 10% of this group the arthritis persists for several years, even after antibiotic therapy. Other symptoms and signs in the dermatological and immune category may co-exist; along with fatigue and mood disorder.

The diagnosis of Lyme disease can be very difficult. It has never been isolated from CSF. Serology in the form of ELISA testing and Western blotting techniques are poor guides, with false negatives of up to 30% and false positives of 10%. Considerable evidence suggests that in all disseminated Lyme infections, seeding of the CNS occurs early, possibly within hours after the bite! Yet spinal tap antibodies to Bb are only positive in 18-20% of cases. Laboratory tests, therefore, have certain limitations and diagnosis is initially clinical and may be supported with a high degree of probability by lab tests.

In the USA now, in endemic areas, mothers check their children every night for ticks, especially in mid-body or hairline areas. The infection is possible all year round, whereas years ago it was mainly April to July. If a tick is found it is covered in olive oil and it ejects itself as it cannot breathe. If you pull it hard and crush it you may, in fact, promote infection. Physicians are very familiar with it and usually see the skin manifestation - Erthyma migrans - in a primary care setting. They immediately start antibiotics, Doxycycline or Amoxycillin for 3-4 weeks and frequently do not do blood tests as these often confuse matters. Early treatment is very important.

Treatment of Lyme disease depends on many factors and is controversial in the sense that many practitioners who treat chronic Lyme disease believe the smaller doses of antibiotics are not really effective. These doctors would advocate Doxycycline, but only in a dosage high enough (300 - 600 mg daily). They would use probenecid with Amoxycillin. Cephalosporins are also used, but must be of third generation, e.g. Claforan or Rocephin being the main ones. The latter are used usually if there is CNS involvement and are best given IV for a minimum of six weeks. Claforan is the drug of choice, as Rocephin has 95% biliary excretion which may cause 'sludging' problems. Accompanying treatment recommendations are: -

* Daily yoghurt or acidophilus preparation;
* Multivitamins and B complex;
* Healthy lifestyle with avoidance of alcohol, excess stress and caffeine.

There is a growing awareness that Lyme disease is getting more prevalent and because of this we need to have a heightened index of suspicion for it as differential diagnosis.

References
1. Lyme Disease, Alten Steers M.D. New England Medical Journal
2. Faul et al. European Respiratory Journal 1998
3. Shapiro et al. Yale University 2000
4. Halperin et al, Cornell University, dept of Neurology
5. Jos. Burrascano M.D. New York "Current Therapy"

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