The Infectivity Of Nosema Ceranae To Two Honeybee Species And The Variation After Continuously Reared In Apis Mellifera Ligustica

Honey bee nosemosis is an important world widely distributed disease of adult bee, including Apis mellifera ligustica and A. cerana cerana in China. For a long time people didn’t think Nosema apis was the only microsporidium species until a new species named Nosema ceranae in A. c. cerana was found in 1996 by Fries. It became imminent to re-classify the microsporidia in China. So we classified the microsporidia species in A. m. ligustica from some parts of China and in A. c. cerana of Fuzhou. Due to the cross-infection of microsporidium to A. m. ligustica and A. c. cerana, we explored the infectivity of N. cerana from A. m. ligustica to the worker honey bee of A. m. ligustica and A. c. cerana at different ages. Furthermore, the changes of spore morphology and surface proteins of N. ceranae from A. c. cerana were studied after continuously infected to A. m. lingustica. The results are as the followings:1. We tested honey bee worker of A. m. ligustica and A. c. cerana from our school apiaries and samples taken from twelve provinces over the country, The result showed, only was N. ceranae found, and so far, no N. apis was found in all samples.2. In order to compare the infectivity of N. ceranae from A. m. ligustica to A. c. cerana and A. m. ligustica, a serial diluted concentration of N. ceranae spores from A.m. ligustica were inoculated individually to newly hatched workers, 3- and 6-day-old adult workers of both species which were then raised in thermostat under darkness, 30℃±0.5℃,65%～80%RH for 8 days.The result showed, （1） To both species, the higher doses were inoculated, the higher infection rate were achieved. （2） The IC₅₀ was 5.12×10² spores/bee to newly hatched worker of A.m. ligustica, while that to A. c. cerana was 29.3×10² spores/bee, which was 5.7 times less than the former; IC₅₀ was 1.30×10²spores/bee to 3-day-old Italian honey bee; IC₅₀ was 3.47×10²spores/bee to 6-day-old Italian honey bee, while that to A. c. cerana was 45.13×10²spores/bee,which was 13.1 times less than the former; It meant that the same day-old Italian honey bee workers were more easily infected than A. c. cerana by N. ceranae. It was implied that N. ceranae from A.m. ligustica has been more adaptive to its new host, A.m. ligustica, than to A. c. cerana. The sequence of the infectivity to different aged worker honeybee of A.m. ligustica was the 3-day-old infection rates> 6-day-old infection rates> 0-day-old infection.3. In order to explore the host impact on N. ceranae （Nc） spore, N. ceranae from A. c. cerana were continuously infected to A. m. linustica for 18 times, and the new spore strain was designated as Nca18. Comparisons on the morphology and spore surface protein were conducted. The results showed that the mature spore of Nca18 was significant shorter and wider （P<0.05） than its original strain Nc. It showed that Nc and Nca18 surface proteins were generally the same on SDS-PAGE gels, with only two major proteins of 31 kD, 28 kD and one minor protein of 34 kD. The quantity of Nca18 spore surface protein was lesser than that of Nc.