• International Journal of Industrial Entomology and Biomaterials
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• v.11 no.1
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• pp.63-69
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• 2005

While observing silkworm larval samples received from field, microsporidian spores formed within the haemocytes of silkworm haemolymph were observed. The spores of microsporidian sp. were purified and characterized for morphological characters viz., size, shape as well as serological affinity with different Nosema spp. (M$_{11}$ and M$_{12}$). The infectivity of the isolated spores to silkworm was also studied. The microsporidian sp. was found to be highly pathogenic to silkworm, B. mori. The isolated microsporidian sp. was designated as NIK-5hm, which formed ovocylindrical spore in the haemocytes of silkworm and differed in spore size (length, 4.55 $\mu$m & width, 2.10 $\mu$m) and shape from Nosema bombycis (NIK-ls), NIK-2r (Nosema sp. Mysore [3.6 & 2.8 $\mu$m]), NIK-3h (Nosema sp. M$_{11}$ [3.8 & 1.8 $\mu$m]), NIK-4m (Nosema sp. M$_{12}$ [5.0 & 2.1 $\mu$m]) and Lb$_{ms}$ (Nosema sp. in Lamerine breed of silkworm [4.36 & 2.14]). In immonological test (Latex agglutination test), the isolated microsporidian spores did not react with antibody sensitized latex particles of N. bombycis, M$_{11}$, M$_{12}$ and Lb$_{ms}$ and thus are different type of microsporidian sp., parasitic to silkworm, Bombyx mori L.

• International Journal of Industrial Entomology and Biomaterials
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• v.18 no.2
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• pp.83-89
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• 2009

Multiplication and spore production of three microsporidia(Nosema bombycis, Nosema sp. 1 and Nosema sp. 2) in selected tissues of pupa and adult of silkworm, Bombyx mori L. were studied in two seasons (SI, SII) with distinct temperature (SI: $20.1{\pm}0.8^{\circ}C$ and SII: $25.1{\pm}0.7^{\circ}C$) regimes. Multiplication of the microsporidia followed a logistic pattern with a lag phase, an exponential phase and a stationary phase. In SII, spore production was significantly (P<0.01) higher in various tissues. Highest spore production was observed 30 days post inoculation (p.i.) in SI and in SII, it was $21{\sim}23$ days p.i. Spore production was significantly (P<0.01) higher in the gut tissues than other tissues. Nosema sp. 2 registered significantly (P<0.01) higher spore production in both the seasons compared to Nosema bombycis and Nosema sp. 1. Results indicate that the multiplication and spore production of microsporidia are tissue specific and extremely sensitive to the temperature at which the host is reared. Through this study, the precise day that the spore numbers of the microsporidia are maximized can be predicted in both pupa and adult in case the infection is initiated in the first instar.

• International Journal of Industrial Entomology and Biomaterials
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• v.11 no.2
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• pp.107-111
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• 2005

Impact of microsporidian infection and season on reproductive potential of Bombyx mori L. was investigated in the laboratory. Microsporidian infection significantly (P<0.01) reduced fecundity and hatching and increased sterility and mortality of eggs. Among the microsporidia, Nosema sp. 2 infected silkworm produced eggs with least fecundity and hatching percent as well as highest dead and sterile eggs followed by Nosema sp. 1 and N. bombycis. Microsporidia, in general, significantly reduced fecundity and hatching percent of eggs and increased number of dead and sterile eggs in all the three seasons except N. bombycis in July - August (S3) and Nosema sp. 2 in January February (S1). Since, seed production is the anchor sheet of mulberry sericulture, coefficient of egg lying is considered as an important aspect and the industry quite often facing shortage of disease free layings. The present study indicates that B. mori is more susceptible to microsporidia during S2 followed by S3 and S1 and Nosema sp2. is most virulent followed by Nosema spl. and N. bombycis.

• International Journal of Industrial Entomology and Biomaterials
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• v.19 no.2
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• pp.221-228
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• 2009

Nosema sp. infection in the Indian tasar silkworm, Antheraea mylitta exerts a complex of influences on its host. The instar duration was extended significantly (P<0.001) except in $1^{st}$ instar. The infected larvae took about 48 days to reach the spinning stage against 40 days in the uninfected ones. The final weight attained by the larva at the end of each instar of development declined significantly following infection, as did weight gain and relative growth rate (RGR). The growth recorded/ day declined in infected larvae compared to uninfected ones from 8.2% during $1^{st}$ instar to 43.3% during $5^{th}$ instar. Food ingestion and digestion increased with advancement of the instar significantly irrespective of the status of the larvae but the relative consumption rate (RCR) declined. These parameters significantly declined in infected larvae (except food digested during $2^{nd}$ instar). The decline was more during $3^{rd}$ instar. In contrast, the approximate digestibility (AD %) was significantly higher in infected larvae than uninfected ones leaving the $1^{st}$ instar larvae unaffected. The efficiency of conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD) did not change in a patterned way following the microsporidia (Nosema sp.) infection. The values of ECI significantly changed during $2^{nd}$, $3^{rd}$ and $5^{th}$ instars; while the change in ECD during $2^{nd}$, $4^{th}$ and $5^{th}$ were significant. During the entire larval life all the parameters tends to decline significantly following microsporidia infection but AD registered a significant increase. Nosema sp. spore concentration has increased 270.7 times during larval development in the course of experimentation.

• International Journal of Industrial Entomology and Biomaterials
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• v.26 no.1
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• pp.1-12
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• 2013

The commercial rearing of polyphagous Indian tasar silkworm, Antheraea mylitta Drury being practiced on naturally grown primary food plants like Terminalia arjuna, (Arjun) Terminalia tomentosa (Asan), and Shorea robusta (Sal) available in the tropical forests of central India, at times, is seriously affected by the disease- Pebrine, caused by Nosema sp., a microsporidian pathogen. The present investigation on comparative larval, silk gland weight and also cocoon parameters in Pebrine-free and Pebrine-infected ecorace of tasar silkworm Antheraea mylitta Drury (Daba TV), illustrates the tasar silkworm larvae infected with pebrine disease causing heavy losses to the economy of the silk industry.

• International Journal of Industrial Entomology and Biomaterials
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• v.12 no.2
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• pp.87-93
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• 2006

Multiplication and spore production of three microsporidia viz., Nosema bombycis, Nosema sp. 1 and Nosema sp. 2 in fifth instar larval tissues of silkworm, Bombyx mori L. in two seasons with distinct temperature regimes were studied. Nosema sp. 2 produced significantly (P < 0.01) higher number of spores in various tissues. Among the tissues, spore production was highest in silk gland, followed by fat body and gut. Spore production was significantly (P < 0.01) higher in season-II (Average temperature $29.4{\pm}1.1^{\circ}C$). Maximum spore production was observed 25 days post inoculation (p. i.) in season-I (Average temperature $18.9{\pm}1.1^{\circ}C$), whereas in season-II, it was 14 days p. i. In season-I, spore production was low up to 21 days p. i., then increased sharply. In season-II, there was a steady increase in spore production. The results indicate that the microsporidian multiplication is tissue specific and extremely sensitive to temperature at which the host is reared. It also reveals that, silk gland, fat body and gut are the most appropriate tissues for microscopic identification of microsporidia in the larval stage.

• International Journal of Industrial Entomology and Biomaterials
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• v.27 no.2
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• pp.219-227
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• 2013

The purpose of this study was to quickly and effectively identify the Nosema disease of bumblebees in Gangwon Province in Korea. Bumblebees are crucial pollinators of various crops, and microsporidia are the critical pathogens of these hosts. When bumblebees are infected with Nosema bombi, their abdomens can become distended. Paralyzed and infected workers often become sluggish and die early. We have identified the morphology of the microsporidium by light and electron microscopy, and found it to have fairly small oval spores, as has been described previously in many other articles. For the specific and sensitive diagnosis of the microsporidian parasite N. bombi in bumblebees, we have developed an improved method of the polymerase chain reaction (PCR) for expeditious diagnosis. Two pairs of primers were tested on N. bombi and the related microsporidia Nosema apis and Nosema sp., both of which infect Bombus ignitus and Bombus hypocrita sapporoensis. Furthermore, we have verified and analyzed the 16SrRNA sequence data of N. bombi in bumblebees by using the Basic Local Alignment Search Tool (BLAST) server at the National Center for Biotechnology Information.

• Proceedings of the Korean Society of Sericultural Science Conference
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• 2005.04a
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• pp.20-21
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• 2005

• Journal of Sericultural and Entomological Science
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• v.27 no.1
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• pp.1-11
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• 1985

In order to clarify the taxanomic position of a new microsporidia K79 which was isolated from the silkworm larvae, Bombyx mori L. in Korea in 1979, the following several experiments such as estimation of pathogenicity in different instar, histopathological examination under light and electronic microscope and examination of fine structure of the sporse were carried out and their result obtained are as follows. In the test of pathogenicity by oral inoculation, the new microsporidia K79 was lower than Nosema bombycis and the susceptibility of the new microsporidia to silkworm was getting lower as the silkworm larvae grew. The lesion of Silkworms' tissue which was infected with the new microsporidia K79 was found in the epithelial cells of trachea, fat body and silk gland cells. The developmental process of the new microsporidia K79 in vivo could be divided into the following five stages: sporoplasm, schizont, sporont, sporoblast, and spore. The process was just the same as the of N. bombycis, but its development was slower than that of N. bombycis. Several differences in the fine structure of the spore under electron microscope, which could be important keys for the classification of microsporidia, were obtained. Anchoring disk and polaroplast lamella of the new microsporidian spore were disclosed to be different from those of N. bombycis. An average number of polar filament coils of the new microporidian spore was 16 at an angle of 75$^{\circ}$. On the basis of various keys for the classification of microsporidia, the results obtained from various experiments proved that the newly isolated microsporidia should be classified into the Genus, "Nosema", nut is further classification for species should be conducted in the future. Therefore, it may be reasonable that the new microsporidia is temperally classified as Nosema sp. K79 considering the fact that it was discovered in Korea in 1979.a in 1979.

• Journal of Microbiology
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• v.40 no.3
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• pp.199-204
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• 2002

A microsporidium, from cabbage white bntteflies, Pieris rapae, collected in Korea, was purified and characterized according to its gene structure, spore morphology and pathogenicity. From the observation of the isolate by SEM and TEM, the endospores, exospores and nuclei, about 12 polar filament coils of the polar tube and posterior vacuoles were all identified. The nucleotide sequence was determined for a portion of genomic DNA which spans the V4 variable region of the small subunit rRNA gene. Comparison with the GenBank database for 15 other microsporidia species suggests that this isolate is most closely related to Nosema species. The pathogenicity against cabbage white butterflies was quantified by inoculating variable doses of spores to the second instar larvae. Peroral inoculation at a dosage of 10$\^$8/ spores/ml resulted in the death of all larvae prior to adult eclosion, but at lower spore dosages of 10$\^$4/-10$\^$5/ spores/ml, many adults successfully emerged. The median lethal dose (LD$\_$50/) was deter-mined to be 4.6$\times$10$\^$6/ spores/ml and the isolate also transmitted transovarially to the progeny eggs at a frequency of 92%.