对家蚕微粒子病感染规律的研究

STUDIES ON PEBRINE INFECTION IN SILKWORM Bombyx mori

本文研究了家蚕微粒子病的食下传染、胚种传染、蚕座传染的规律性。指出对丝茧育来说感染越早危害越大，对种茧育来说感染越晚危害越大；食下感染的次数具有累积效应，但以起蚕期和将眠期（5龄为将熟前）影响最大；在蚁蚕就有感染蚕存在的情况下，丝茧育有二个蚕座传染周期，种茧育有三个蚕座传染周期；淘汰措施无论对丝茧育还是种茧育均是有效的，但其有效性随着基数毒率的增大而降低，只有当丝茧育的基数毒率在3％以下，种茧育的基数毒率在1％以下时淘汰措施才能取得95％以上的有效性，而且淘汰得越早越彻底效果越好；微粒子病对次代蚕的遗传毒率是一个变量，母蛾的带毒程度是影响其变化的主要因素；有毒母蛾产下卵通过催青后，遗传毒率在蚁蚕期已基本达到最大值，蚁蚕经高温高湿处理后遗传毒率的增幅不大而主要是孢子密度的增加；同一有毒母蛾产下卵用不同方式保护后，越年种蚁蚕毒率显著大于即时浸酸种蚁蚕毒率，说明微孢子在蚕卵的休眠期仍在增殖中；胚种传染带毒蚕的死亡时期大部分在3龄以前，影响发病死亡早晚的主要因素是母蛾的带毒程度。

Oral infection,transovarian transmission and bed transmission (transmission amongindividuals in a rearing bed) of Nosema bombycis (N. b) in the silkworm were studied. Inthe case of oral infection,it is more harmful to cocoon production by infection in younglarval stage,but to egg production by that is in grown larval stage. Although oral infection had an accumulation effect,the larvae just after exuviation and before moulting (before maturing in the fifth instar) were more susceptible. In the case of bed transmission,there would be two infection stages to the silkworms for cocoon production and three tothose for egg production,if few infected larvae were mixed into the newly hatched ones.Removing the infected larvae from the population in the early stage of infection was effective to prevent the disease from further spread and to lower the morbidity. The effectcould be achieved up to 95 percent when the original infection rate was less than 3 percent to the silkworms for cocoon production and one percent to those for egg production. As the original infection rate increased,the effect decreased. In the case of transovarian transmission, the percentage of the transovarially transmitted eggs dependedmainly on the infection extent of the female moths and reached the maximum level byhatching, while the incubation conditions of higher temperature and higher humiditycould increase the number of spores in the infected larvae. The eggs from the same mothshowed different infection rate under different protection conditions. The overwinteredeggs suffered from obviously higher infection rate than those subjected to immediateacid-treatment, revealing that N. b was still under multiplication in the dormant eggs.The transovarially transmitted larvae generally died before the third instar, but variedmainly with the infection extent of female moths.