Studies On Population Ecology Of Ixodes Persulcatus And Its Infection With The Tick-borne Pathogens

The ixodid tick Ixodes persulcatus is widely distributed in the whole world, across the Eurasian Continent, from the Baltic Sea to the Pacific Ocean, including not only the territory of the former Soviet Union(mainly Russia), but also some spots in Poland and certain parts in Northern China, Mongolia and Korea, as well as part of Hokkaido Island and several smaller nearby islands in Japan. By the 1990 s, I. persulcatus distributed in Heilongjiang Province, Jilin Province, Liaoning Province, Gansu Province, Shanxi Province, Xinjiang Uygur Autonomous Region and Tibet Autonomous Region in China. For a variety of reasons, such as global warming, urban expansion, land use, increasing outdoor human behavior and so forth, the tick species distribution area is expanding and tick-borne pathogens are increasing. In recent years, research has shown that I. persulcatus has been found in Hebei Province, Inner Mongolia Autonomous Region,Ningxia Autonomous Region,Tianjin, Beijing, and even in Henan Province, which indicates that I. persulcatus population distribution has a tendency to expand. Ticks are blood-feeding obligate parasites that have attracted increasing scientific attention primarily because of their role as vectors of numerous pathogens. It has been testified that the spectrum of such pathogens includes protista, bacteria, rickettsia, helminthes and virus. Among the major tick-borne diseases transmitted by I. persulcatus transmitting pathogens, there are borreliosis, ehrlichiosis, babesiosis, rickettsiosis and tick-borne encephalitis, which are considered to be considerably dangerous to human beings and domestic animals in China. Various forms of tick borne diseases are concurring in widespread areas where I. persulcatus distribute.In this study, we investigated the distribution, population dynamics change, seasonal succession and the host parasitism of I. persulcatus in Erguna National Nature Reserve of the Inner Mongolia border areas between China and Russia. The study showed that the ixodid ticks multiplied mainly in the shrubs and meadows in the forest zone of the reserve. Adults of I. persulcatus began to look for hosts and feed on blood in early April, which showed a peak in late May and stopped in August. The active stage of larvae was similar to that of nymphs, both beginning in May, disappearing in September, and showing peaks several times in the duration of June, July and August. Adults of I. persulcatus mainly attacked the neck and the body of goats, and the attacked signs were also found on the ear, face and the base of horns of goats. There was no evidence that rodents were attacked by the adults. On the other hand, larvae and nymphs primarily attacked the neck and face of rodents. After September, no parasitisms of adults for overwintering were found in goats, nor were adults captured by dragging under field conditions.Moreover, according to experiments, I. persulcatus’ s biological characteristics in various growth stages were also investigated under laboratory conditions. We researched the activity of larvae, nymphs and adults’ blood feeding in rabbits and their living status under controllable laboratory conditions during the non- parasitic stage, observing and recording the parameters of their life cycle in different growth stages. The results of this study suggested that for larvae, the early stage of blood feeding, the blood feeding stage and the ecdysis stage added up to 25.6 days; for nymphs, the early stage of blood feeding, the blood feeding stage and the ecdysis stage added up to 29.3 days; for female I. persulcatus, the early stage of blood feeding, the blood feeding stage, the early stage of spawning and the spawning stage added up to 36.6 days, with the hatching period lasting for 31.7 days. Therefore, the average life cycle was 123.2 days(within a range of 93 to 149 days). Furthermore, there was a significant correlation between the engorged body weight of females and their egg laying mass(r = 0.716, p < 0.001). The female reproductive efficiency index(REI) was 4.35, with an average hatchability of 88.5%.224 ticks of I. persulcatus collected in the Inner Mongolia border areas between China and Russia were studied by means of the PCR molecular detection to explore the infection with the tick-borne pathogens. The result showed that these ticks of I.persulcatus carried Lyme disease spirochaete, Babesiasis, and Spotted fever group rickettsiae, and the infection rates were 4.02%, 4.91% and 0.89% respectively, which showed that Erguna National Nature Reserve is the natural infectious focus of the above-mentionded three tick-borne pathogeneses. Meanwhile, no Ehrlichia chaffeensis and Anaplasma phagocytophilum were detected, nor was the evidence found that several species of pathogens were coninfected.