engleski

Leptospirosis and climate change

Background. Leptospirosis is a bacterial zoonosis caused by pathogenic members of genus Leptospira. Wild and domestic animals can be infected but rodents are the main reservoirs and the most important source of infection for humans. Leptospires excreted with urine of infected animals can survive in the environment for several months if certain conditions of temperature and humidity are met. Aim of this study was to correlate climate changes with population density of small rodents and incidence of leptospirosis in humans in Croatia. Material and Methods. We compared archive data on incidence of human cases with rodent population density and average monthly precipitations and air temperatures in a period from 2009 to 2014. Small rodent population density was assessed using constant trapping sites. Data on the average monthly precipitation amounts and air temperatures were obtained from Meteorological and Hydrological institute of Croatia. Results. Results revealed annual and seasonal variations of leptospirosis cases that were mainly influenced by weather conditions. During 2010 and especially 2014 higher average precipitation was correlated with significant increase in leptospirosis incidence (IR of 2.15 and 3.23 respectively). Strong and multifactorial link of climate conditions and rodent population was also noted. Discussion. Climate extremes in 2014 were followed by increased rodent population density, high percentage of infected rodents and finally extremely high incidence of human leptospirosis. In January and February 2014 we had average temperature above 4.5°C compared to usual temperatures about or below the freezing point. Mild winter led to reduced winter mortality of rodents. Abundant rainfall and warm spring flushed vegetation growth resulted in high reproduction and increase in number of small mammals. Conditions for Leptospira survival in the environment were also favourable. All of these factors created high environmental burden and consequently extremely high leptospirosis incidence in humans. In conclusion, due to the climate change and global warming a further increase in leptospirosis incidence in humans can be expected.

leptospirosis, climate change, Croatia

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