| Ticks, which could carry a variety of pathogens and cause hosts’natural foci diseases, are ectoparasites lived by sucking blood from hosts. Ixodes persulcatus, Haemaphysalis longicornis and Rhipicephalus haemaphysaloides are pieces widely distributed in China, and also vectors of many diseases. Human babesiosis is a newly discovered infectious diseases transmitted by ticks, and its main pathogens is Babesia microti. In this research, in order to explore possible routes of transmission of B.micrtoti in China, we study the effect of temperature on the infection of B.microti in larvae of I.persulcatus, H.longicornis and R.haemaphysaloides. At the same time, we study the growth and development of I.persulcatus and H.longicornis infected with B. microti, explore effect of temperature on the development of infected ticks, to provide scientific bases for the prevention and control of human babesiosis and ticks.Firstly, we used I.persulcatus, bisexual H.longicornis, parthenogenetic H.longicornis and R.haemaphysaloides larvae to bite BALB/c mice which were injected with B.microti. After engorging, the ticks were kept incubators at 20 ℃,25 ℃ and 30 ℃ respectively, and the humidity in the incubators is 95% ± 5%, and the photoperiod is 12:12 h. During incubation, the ticks were tested the positive rate of Babesia microti with nested PCR at certain interval.We found that I.persulcatus, bisexual H.longicornis and R.haemaphysaloides could trans-stadially transmit B.microti from larval ticks to nymphal. While this result was not detected in parthenogenetic H.longicornis. The trans-stadial transmission of B.microti from nymphs to adults and transovarian transmission were not detected in both kinds of H.longicornis.The positive rate of larval ticks of I.persulcatus and R.haemaphysaloides after engorging were both 100%. As time went, the positive rate decreased slowly. The positive rate of larval ticks of bisexual and parthenogenetic H.longicornis were 91.7% and 80% respectively, and the positive rate of parthenogenetic dropped faster than bisexual, and the difference had statistically significant (P <0.05).Secondly, we observed the developmental duration of engorged larvae of l.persulcatus, bisexual H.longicornis, parthenogenetic H.longicornis and R.haemaphysaloides at different temperatures under laboratory conditions.We found the fitting curve of developmental duration and temperature of engorged l.persulcatus larvae infected with B.microti was y= 0.0258x2-1.961x+53.9. The developmental duration shortened with the temperature raised in the range of 20 ℃-30 ℃. The developmental zero temperature of larval ticks was-1.93 ℃, and the average developmental duration was (19.56 ± 2.31) days, and the average effective accumulated temperature was (578.67 ± 37.72) degree day (DD).The fitting curve of developmental duration and temperature of engorged bisexual H.longicornis larvae infected with B.microti was y= 0.0932x2-5.25x+82.44. At 28.17℃, the shortest developmental duration was 8.51 days. The developmental zero temperature of larval ticks was 14.89℃, and the average developmental duration was (10.84 ± 2.67) days, and the average effective accumulated temperature (102.41 ± 24.69) DD.The fitting curve of developmental duration and temperature of engorged parthenogenetic H.longicornis larvae infected with B.microti was y= 0.0856x2-4.974x+82.16. At 29.05℃, the shortest developmental duration was 9.90 days. The developmental zero temperature of larval ticks was 14.95℃, and the average developmental duration was (12.69 ± 3.57) days, and the average effective accumulated temperature (116.89 ± 32.43) DD.The blood-sucking time of larval R.haemaphysaloides ticks were shorter than that of the I.persulcatus and H.longicornis, while the developmental durations of larval and nymphal R.haemaphysaloides ticks were longer than that of H.longicornis, and shorter than that of I.persulcatus.We could conclude, from the above results, I.persulcatus, bisexual H.longicornis and R.haemaphysaloides could trans-stadially transmit B.microti from larval ticks to nymphal. The susceptibility of R.haemaphysaloides to infection with B.micoti was highest. The developmental durations of different tick species infected with B.microti differed at different temperatures. In appropriate temperature range, the temperature could accelerate the developmental speed of ticks, and shorten the developmental duration. |
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