Forest Ecosystems And Zoonoses

The turn of the century is characterized by occurring of many emerging and re-emerging zoonoses. Various factors that have contributed to the re-emergence of this infection include disturbances in natural ecosystems, increase in international transport of animals and humans and an improvement in diagnostic facilities resulting in better detection of these infections. Forests are complex natural ecosystems and home to a wealth of different organisms. They are among the greatest natural treasures from the perspective of its overall function that impacts the natural environment and the living conditions within. Mouse-like rodents that are known natural reservoir for numerous zoonoses (leptospirosis, tick-borne meningoencephalitis, lyme borreliosis, haemorrhagic fever with renal syndrome, etc.) form an important part of forest faunal community. The widespread geographic distributions of rodents harboring pathogens indicate considerable disease-causing potential essentially worldwide. The following species of mouse-like rodents are most common in the continental European forests: striped field mouse (Apodemus agrarius Pall.), yellow-necked mouse (A. flavicollis Melch.), wood mouse (A. sylvaticus L.), bank vole (Clethrionomys glareolus Schreib.), common vole (Microtus arvalis Pall.), field vole (M. agrestis L.), water vole (Arvicola terrestris L.) and the European pine vole (M. subterraneus de Sel.). The spread of certain zoonoses is dependent on the abundance of rodent populations, their distribution, mobility, feeding intensity, habitat conditions and reproduction potential, as well as the abundance and distribution of wild and domesticated animals susceptible to infectious disease. A large number of factors influence the population sizes of mouse-like rodents, and these can be classified into four basic groups: abundance and physiological state of the population, meteorological conditions, habitat and food sources, and natural enemies and diseases. The population abundance of each species changes in the course of a year or several years. Years with mild winters, dry springs and summers are favorable for increases in abundance of these species, which in turn can contribute to the spread of individual zoonoses in forests. The objectives of interdisciplinary studies currently ongoing in Croatia are to define the distribution and genetic diversity of individual causative agents of certain zoonoses such as leptospirosis, lyme borreliosis and hemorrhagic fever with renal syndrome. In the same time, the level of infection among mouse-like rodents as the main reservoirs of these zoonoses in forest ecosystems is investigating on molecular level. Establishing the natural fruit-bearing cycle for woody plants is successfully used in assessing the possible growth in population numbers. Regular controls of rodent populations and their infectiousness is significant in planning epidemiological and sanitary measures in preventing outbreaks of epidemics and individual cases of illness among animal and human populations (forest workers, excursionists, mountaineers, soldiers, tourists, etc.).