Cesare Furlanello, Stefano
Merler*, Claudio Chemini*.
*ITC-IRST, Trento, *Centro di Ecologia Alpina, Viote Mt. Bondone, Trento, Italy
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Lyme disease is a tick-borne infection caused by the
spirochete Borrelia burgdoferi. The first indicator of the disease is generally the
erythema migrans rash, usually appearing about two weeks after the bite of an infected
tick; several weeks after serious arthritic and then neurological disorders may occur.
Although less common, cardiac complications (Lyme carditis) may develop and are reported
in up to 8% of patients1,2. The pathology has to be seriously
considered because Lyme disease is now the most common vector-borne illness in North
America, with more than 16 000 cases in 19963, and it
is becoming common also in Europe, where the tick Ixodes ricinus has been acknowledged as
the main vector of the disease. Known endemic areas for B. burgdoferi are Southern Sweden,
with 69/100 000 cases per inhabitants4, Slovenia with
137/100 000 in 19945, but also Lithuania, areas in
Germany and Austria, and in general in Central-Eastern Europe6
including in the picture the tick I. persulcatus and the spirochetes B. afzelii and B.
garinii.
In endemic areas for Lyme disease, prevalence of Borrelia may be high. In a recent
review, Ostfeld7 reports rates of infection of 25-35%
of nymphs and 50-70% of adult ticks. In far eastern Russia, infection rate in adult I.
persulcatus ticks was near 27%8. Preliminary data in
Trentino (Italian Alps) showed a prevalence between 15 and 40% of B. burgdoferi in I.
ricinus9,10. In some regions of Slovenia, more than 40%
of adult I. ricinus ticks were found infected5.
Although these data do not take into account tick population seasonal dynamics, which
depend on abiotic climatic factors and on the abundance of reservoir-competent hosts (eg
field mice of the genus apodemus) from which the ticks feed, in endemic areas it may be
assumed that the risk of exposure to Lyme disease can be assessed through models of the
risk of tick bites.
Risk models are thus of particular importance for i) prevention by avoidance of
tick-bites; ii) systematic skin control for tick check after possible exposure to risk7; and iii) correct diagnosis of Lyme disease, either in
the early phase by prompt recognition of the erythema migrans rashes11
or in case of the reumathological, neurological and cardiac complicances that may develop
when Lyme disease is left untreated. In particular, borreliosis should be suspected in all
patients with unexplained cardiac symptoms (and especially in atrioventricular block of
unknown origin in young patients) who have been exposed in regions invaded by the
epidemic.
Since the first published clinical studies1,
idiopathic (often complete) atrioventricular block is indeed a primary manifestation of
Lyme carditis2,12, and has been reported also in very
young patients13. Other cardiac manifestations are
myopericarditis, and rhythm disturbances ventricular extrasistoles and intermittent
tachyarrhythmias14. Starting from findings of heart
block, a case of fascicular tachycardia associated to borreliosis has been reported15. The overall prognosis of Lyme carditis is good, but
usually temporary cardiac pacing may be required and late dilated cardiomyopathy may occur2,16. Chronic heart muscle disease has shown to be
associate to Lyme disease through ELISA test17;
moreover spirochaetes have been revelead by subendocardial18
or endomyocardial biopsy17.
However, a high grade of suspicion is required to make a diagnosis without appropriate
information on possible exposure of risk19. In this
paper, we present results in risk assessment based on a computational environment for
predictive classification models from georeferenced data. The system is the result of a
joint research initiative in computational methods for biological risk assessment in
ecology by the Institute for Scientific and Technological Research (IRST) and the Centre
of Alpine Ecology (CEA).
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