Biochemical changes and diagnosis of microsporidial disease (pebrine) of silkworm, Bombyx mori L. (Leipdoptera: Bombycidae)

摘要

Microbial diseases of silkworm, Bombyx mori L., are an economic threat to the silk industry. Every sericulturist has experienced the loss of his crops either due to a protozoan disease or other microbial diseases. Among the diseases, the worst is pebrine, a microsporidian disease caused by the protozoan Nosema bombycis, followed by bacterial or viral diseases. This article reviews the molecular basis of the protozoan attack to the silkworms and its physiological impact on the larval development. The frequent occurrence of the disease relates to environmental factors and hygiene. The pharmacodiagnostics of this disease has only been recently developed and reviewed herein. The ubiquitous pebrine disease caused by N. bombycis is prevalent in various silk producing larvae indicating its virulency and subsequent economic impact. The only method adopted for the identification of pebrine disease has been the examination of the mother moth. However, recently several diagnostic techniques were suggested for the accurate detection of N. bombycis of silkworm larvae by using bitoechnological methods. Agglutination test by using N_5McAb - sensitized latex particles, production of monoclonal antibodies (ELISA test), and hybridization of two DNA probes from N. bombycis with the genomic DNA from N. costelytrae, C. zealandica (grass-grub) and Bombyx mori, proved best for the early diagnosis of the pathogen, N. bombycis in silkworm larvae as well as in silk mother moths. Western blot analysis results showed the presence of a Nosema infection-specific 17 KD polypeptide in pebrinized eggs and larvae. Hence, this 17 KD polypeptide could be a epidemiological significance and used as a virulent marker for the identification of microsporidian infection. However, recently some practical sericulturists suggested that feeding Victory - 1 or V_1 and M_5 varieties of mulberry leaves reduced the disease incidence.