Original scientific paper
Global Warming, Climate Change and the Effect on Ticks and Tick borne Pathogens
Ljiljana Mišić-Majerus
; OB Dr.T.Bardek, Koprivnica
Ksenija Zaninović
; Državni hidrometeorološki zavod, Zagreb
Vesna Cmrk-Kadija
; Agrometeorološka postaja, Koprivnica
Oktavija Đaković-Rode
orcid.org/0000-0001-8023-4314
; Klinika za infektivne bolesti Dr.Fran Mihaljević, Zagreb
Abstract
In the last several decades we have been facing a progressive global warming caused by an excessive concentration of greenhouse gases in the atmosphere as a result of human activities. Global warming also causes a wide spectrum of consequences on the human health, including changes in the spread of tick borne pathogens. Temperature changes in time and space, precipitation and humidity have with great certainty a significant impact on biology and ecology of ticks-vectors, tick hosts and possible transmission of disease pathogens. Basic goal of this paper was to examine and determine whether temperature changes have an impact on seasonal and regional distribution of tick-borne encephalitis (TBE), clinical characteristics of disease in the area of Koprivnica-Križevci County. We retrospectively collected and analyzed demographic, epidemiologic and clinical characteristics of patients treated for TBE at the Infectious Disease Department of the General Hospital »Dr.Tomislav Bardek« in Koprivnica from 1979 to 2007. Depending on the year of hospitalization, for comparative purposes, the patients were divided into three groups: the first group consisted of patients hospitalized from 1979 to 1988, the second group from 1989 to 1998 and the third group from 1999 to 2007. Air temperature was measured at the Meteorological Station Koprivnica, a member of the Croatian Meteorological and Hydrological Service network. The diagnosis of TBE was based on the presence of pleocytosis in the cerebrospinal fluid (>5×106 cells/liter) and the presence of specific serum IgM, or seroconversion of IgG antibodies, that presented two basic criteria for patient enrolment in the study. Enzyme-linked immunosorbent assay (ELISA) was used for detection of serum antibodies, and up to its introduction, complement-binding reaction test. Exclusion criteria were patients with recently acquired BBSL co-infection. During the conducted research, recent TBE viral infection was detected in 654 patient, aged 2 to 83 years. Males predominated. In the first decade researched, a total of 304 patients fell ill, in the second 260 and in the third 90. The disease (except in January) was present throughout the year, with the highest incidence recorded in June and July. The first observed decade recorded the highest incidence, while in the last decade the incidence decreased for more than three times. In the first decade the maximum incidence of TBE was in the summer and minimum in the winter months. In the second decade we have noticed that the maximum incidence shifted towards spring months. Autumn months record a slight increase in the incidence rates, and in the winter months the incidence has more than doubled. The most prominent characteristic of the third observed period is a significant increase in the incidence rates in autumn and winter months. In the analyzed period, air temperature increased on the average for 0,5 °C/10 years. Higher air temperatures are recorded in all months, except in September and December. The highest increase was observed in February and November, although the remaining months also record increases. The increase of TBE incidence in the spring months and October, recorded in the last two observed periods, can be related to increased temperatures in those months. By analyzing the distribution of our patients according to place of living we noticed a decreased incidence in the area of Križevci, and increased in the plain areas of our County. Clinical symptoms/signs of disease remained the same. Clinical forms of disease have changed – aseptic meningitis predominated in the first decade and in the last two decades meningoencephalitis and meningoencephalomyelitis. The results of our long-term research have shown significant changes that occurred in seasonal and locational distribution of patients with TBE, as well as clinical forms of disease. The effect of observed changes, primarily increased air temperature especially during autumn and winter period, regardless whether being caused by human activities, are an important, but probably only one in a series of known and unknown factors responsible for this newly occurring changes in the TBE incidence in the Koprivnica-Križevci County.
Keywords
climate change; ticks; tick-borne pathogens
Hrčak ID:
30493
URI
Publication date:
3.6.2008.
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