Climate changes and rickettsioses

Cilj ovoga rada je prikazati suvremena saznanja i spoznaje o utjecaju klimatskih promjena na prirodu rikecija i rikecioza. Izolacija i identifikacija »novih« patogenih rikecija ostvarena je primjenom suvremenih dijagnostičkih testova. Danas je poznato dvadesetak patogenih rikecija, od kojih je njih 13 prepoznato tek proteklih dvadesetak godina. U tom razdoblju zabilježene su nove rikecijske bolesti, raširenost pojedinih rikecioza izvan poznatih endemičnih područja i ponovno epidemijsko javljanje već poznatih rikecioza. Udio utjecaja klimatskih promjena u epidemiologiji i kliničkom spektru rikecioza djelomično je razjašnjen i procjenjen, kao i udio čimbenika koji pripadaju rikecijskim domaćinima, vektorima ili samim rikecijama. Novija istraživanja potvrdila su značenje klimatskih utjecaja, osobito na brojčanost i raširenost R. sanguineusa, vektora R. conorii, uzročnika mediteranske pjegave groznice. Osim prepoznavanja novih rikecija i rikecioza bilježe se i nova saznanja o rikecijskim vektorima, širokom spektru kliničkih simptoma i znakova bolesti i javljanju bolesti, osobito mediteranske pjegave groznice, tijekom cijele godine, a ne samo sezonski (proljeće, ljeto). Pojavljivanje rikecioza, osobito rikecijskih pjegavih vrućica, u različitim područjima svijeta, a izvan prijašnjih endemskih područja, sve češća pojava rikecioza u izvansezonsko doba, širok spektar kliničkih simptoma i znakova bolesti, kao i pojava »novih« patogenih rikecija, upućuju na daljnje proučavanje klimatskih i drugih utjecaja na prirodu rikecija i rikecioza.The rickettsiae are ancient microorganisms that survived as intracellular bacteria in arthropods (ticks, mite) for thousands of years. There are several reasons why rickettsial diseases present an important health care problem. Their significance has been unjustly underestimated, especially after a decrease in the epidemologic occurrence of classic typhus. According to the World Health Organisation, typhus today occurs in smaller or larger epidemics in many endemic areas throughout the world and presents a constant threat for human health and life. There is an increasing number of records on new rickettsioses occurring or new areas of their distribution. In the last fifteen years, there has been a significant increase in the incidence of rickettsioses in endemic areas, a wide clinical spectrum of disease has been recorded, severe types and lethal outcomes of disease described, molecular investigations have introduced changes in rickettsiae taxonomy, a significant number of »new« pathogens has been discovered, new knowledge about rickettsiae and rickettsial diseases has been acquired. Thus, rickettsioses today account for diseases caused by rickettsiae from three separate genuses. Rickettsiae from the rickettsia genus cause rickettsioses from the spotted fever and typhoid group, rickettsia from the orientia tsutsugamush genus is the cause of scrub typhus, and rickettsiae from the ehrlichiae genus cause human ehrlichioses, Ehrlichia chaffeensis is the cause of human monocyte ehrlichiosis and Anaplasma phagocytophilum is the pathogen of human granulocyte anaplasmosis (known also as human granulocytic ehrlichiosis). For years, rickettsial diseases have not been considered important in travel medicine, and only rare clinical descriptions were mentioned, such as travelers′ disease. However, in the last ten years, in accordance with an increase and spread of ecotourism and tourists traveling to uninhabited areas, we record an increase in the incidence of spotted fever and other rickettsial diseases in travelers (tourists) that resided in endemic areas, especially in the countries of southern Europe, Africa and Asia. Intensified international travel and tourism have made geographical limitation of rickettsial diseases to endemic areas with moderate and tropical climate only fictive. Namely, residing in these areas creates a possibility for »importing« the disease, which presents a great difficulty for physicians, especially those without experience with rickettsioses, in clinical recognition of the disease. It is very dangerous to consider rickettsioses and rickettsial spotted fevers as self-healing diseases, as it was the case until recently. Mediterranean spotted fever, geographically most widespread rickettsiosis, can endanger human life, based on the manifestation of severe clinical forms of disease (acute renal failure, various neurological manifestations, peripheral gangrene). These severe clinical forms, with mortality rate ranging from 1,4 to 5,6 %, are more frequent among patients with Rocky Mountain spotted fever. Severe clinical forms of Mediterranean spotted fever, and one lethal outcome, have been recorded in our patients as well. Today, 20 pathogenic rickettsiae are known, 13 of which have been recognized in the last twenty years. It is still unclear whether recognizing newly discovered pathogenic rickettsiae is the result of improved diagnostics or changes in factors that belong to rickettsial hosts, vectors or rickettsiae themselves. Namely, some among these 20 pathogenic rickettsiae have been considered nonpathogenic or have not been registered yet. The role of abiotic factors is also unclear, especially geographic distribution and seasonal occurrence. Therefore, the opinion that certain rickettsioses are widespread only in a particular continent or that certain vectors are specific for certain rickettsiae, has changed, and more and more information supports the idea that various types of ticks and fleas are vectors of one or more rickettsiae. The question remains whether the affinity of certain ticks towards their host is changing, especially if such a change is the consequence of climate changes (rainfall, floods, droughts, global warming). The occurrence of rickettsioses, especially rickettsial spotted fevers, in various areas of the world, outside previous endemic regions, and the manifestation of newly discovered pathogenic rickettsiae demand further investigations of the impact of climate on the nature of rickettsiae and rickettsioses