• International Journal of Industrial Entomology and Biomaterials
• /
• v.33 no.2
• /
• pp.121-131
• /
• 2016

Ten microsporidian isolates from Samia cynthia ricini, and Antheraea assamensis in India along with a Nosema reference strain (NIK-1s_mys) from B. mori India were characterised morphologically and molecular based tools. The test isolates observed elongated oval in shape while reference strain was oval and ranging from 3.80 to 4.90 m in length and 2.60 to 3.05 m in width. The ribosomal DNA region 'IGS' of test isolates assessed by PCR amplification, followed by cloning and sequencing. IGS sequence and phylogenetic analysis of test microsporidian isolates showed very close relationship with three Nosema references species: N. philosamia, N. antheraea isolated from Philosamia cynthia ricini and Antheraea perny in China respectively and N. disstriae from Malacosma disstriae in Canada. The clustering pattern of dendogram reveals all test isolates appear distinct from Nosema std. (NIK-1s_mys) India used as reference strain in the study. The result suggests IGS indeed a suitable and highly applicable molecular tool for identifying and characterise the microsporidian isolates in similar population.

• Journal of Sericultural and Entomological Science
• /
• v.39 no.2
• /
• pp.146-153
• /
• 1997

The microsporidian infection with Nosema bombycis, reconfirmed its high virulence and transovarial tranmissibility, however, the characteristic symptom of the spots like pepper grains on the diseased larval skin was no more recognized by present varieties of the silkworm. Transovarial transmission rate detected from moth was above 90% in dead eggs or dead larvae in the rearing by mulberry leaves, 80% in the newly hatched larvae starved to death. Transovarially transmitted N. bombycis was easily observed from dead eggs and larvae, and were suggested an individual inspection of a few of dead eggs for detection of the pathogenic spores. The progeny population provided indicative factors on the sampling of predictive and corrective inspection. The higher concentration of N. bombycis spores included in the hindabdormal part of infected moth, applicative on the simple method of indivisual moth inspection. For the predictive inspection of growned 5th-instar larvae, N. bombycis infection was detectable without microscopic observation by the unique symptom of turbid milky-white spots on the silk gland. Inspection of the meconia artificially discharged from silkworm moth, was also succesful of microscopic observation before crossing, without killing or homogenize the moths. The results provided a basis of rational methods for the inspection of N. bombycis infection of the silkworm.

• Journal of Sericultural and Entomological Science
• /
• v.39 no.2
• /
• pp.154-160
• /
• 1997

Present experiment designed for the review of theoretical basis for the inspection system of infected insects by Nosema bombycis. A microporidian N. bombycis, known as the high virulence, produced at the average of 7$\times$108 spores per female moth of the silkworm, Bombyx mori, enabled transovarial tranmission. Detectability of N. bombycis spores in the mass inspection was varied by dillution level, the higher limit of dillution with healthy moths was 1:140 for 100% detection, 1:160 for 99.5%, 1:200 for 99.0%. For an efficient inspection under the microscopic observation (600$\times$), the lower limit of spore concentration was determined as 1, 000, 000 spores/ml, 60-80 moths could be applicable for a maximum sample unit of a lot. Following the present inspection unit conditioned 35 to 40 moths for a lot. N. bombycis spores were easily detectable from the preparation of crude homogenate with 2% KOH, even the step of contrifuge was omitted. The results suggested a new basis of rational mass inspection system of silkworm female moths to save the facilities, labor, and time.

• International Journal of Industrial Entomology and Biomaterials
• /
• v.17 no.1
• /
• pp.157-163
• /
• 2008

Infection of pathogenic microsporidia, Nosema bombycis and Nosema mylitta (Chakrabarti and Manna, 2006) decreased egg production, fecundity, hatching % and increased sterile eggs in heavily infected mulberry silkmoth, Bombyx mori L. On an average a disease free moth laid upto 442.67 eggs with high hatching % (99.53) and less sterile eggs ($0.47{\sim}2.00%$). While an infected moth laid less number of eggs ($7.00{\sim}412.00$) with low hatching % ($32.437{\sim}98.643$) and high sterile eggs ($2.143{\sim}129.571$). Fecundity of disease free laying was highest (468.714) during season-1 then gradually decreased during season- 2 (414.000) to season- 3 (404.285). But fecundity of an infected laying was highest during season-2 and hatched eggs were lowest during season-2. Higher inoculums concentration of N. mylitta infected to 5th stage larva of mulberry silkworm drastically decreased the fecundity in season - 3 and lower inoculums concentration of N. bombycis decreased the fecundity in season-1 and 3. Season-3 was most effective season to decrease the fecundity and increase sterile eggs when both temperature and humidity were fluctuated from the optimum level.

• Journal of Apiculture
• /
• v.34 no.2
• /
• pp.137-140
• /
• 2019

Although honeybees (Apis mellifera) are crucial for maintenance of the ecosystem, population of honeybee has been steadily decreasing due to diseases including nosemosis. Nosemosis is a disease caused by Nosema ceranae and is now considered as a major threat to honeybees. N. ceranae is a microsporidian that stays in form of spore even before the infection, which makes it harder to control than other pathogens. People are now aware of this parasite, however, cure and preventive candidates for nosemosis are hardly found until today. In this study, in vitro experiment of Lespedeza cuneata treatment to prevent nosemosis were done using Trichoplusia ni cell line, BTI-TN5B1-4. Normal T. ni cells exhibited round shape without abnormal size. On the other hand, when N. ceranae were treated, cells deteriorated and some cells abnormally enlarged due to N. ceranae infection. Interestingly, treatment of T. ni cells with L. cuneate extract protected abnormal cell shape induced by N. ceranae infection to normal shape. Some N. ceranae spores were observed outside of the cells. Effective concentration range for N. ceranae control were experimented. Lowest concentration which can control nosemosis were 50 ㎍/mL. When the concentration of L. cuneata extract was exceeded 200 ㎍/mL, cytotoxicity started to show up.

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

• Korean journal of applied entomology
• /
• v.57 no.2
• /
• pp.87-95
• /
• 2018

Nosema spp. (NS) causes severe problems to honey bee colonies including the death of the highly infected ones. Searching for effective materials to control this parasite is very important. The objectives of this study were to identify the calendar for the prevalence of NS and other bee diseases, and to test the efficacy of three materials: diluted honey mixed with lemon juice (M1), chamomile extract mixed with sugar syrup (M2) and sutrivet mixed with sugar syrup (M3) against Nosema. To realize these objectives, diseases of brood and adult honey bees were surveyed over one year. Also, the efficacy of M1, M2 and M3 against Nosema was evaluated under field and laboratory conditions. The results showed that few diseases for immature and mature stages of honey bees were recorded. NS was detected during winter and spring in link with low temperature and high relative humidity. Under field conditions, M2 reduced the infection by 36.66% while M3 by 23.33% and finally M1 by 13.33%. In the laboratory, the highest efficacy was to M2 followed by M1 and finally M3. The three materials impacted the percentage of survived bees significantly higher than infected bees without any treatments over the experimental period. The study suggests the potential role of chamomile as a natural material to control NS.

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

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

• International Journal of Industrial Entomology and Biomaterials
• /
• v.23 no.1
• /
• pp.107-113
• /
• 2011

Infection effect of $Nosema$ $bombyics$ on the midgut of silkworm $Bombyx$ $mori$ and subsequent appearance of spores and the performance of larvae was studied. Autopsy of larvae showed white pustules on the surface of midgut at 5 days of post infection (pi). At later stage, important organs like midgut, silk gland and gonads reduced in size and all these organs showed white pustules. Light microscope observation of pustules revealed enormous spores. Spore multiplication was at a faster rate in young larvae. Infection of the adult larvae resulted in pebrinized pupa and moths. Larval weight, cocoon weight and cocoon shell ratio reduced as the post infection period increased. Transverse sections of midgut showed $N.$ $bombycis$ infection limited to a few columnar cells at 3-5 days of pi. At 7 days pi, cell volume increased, cells were swollen and elongated. Heavily infected cells looked like sacks filled with parasite and the apical region of certain cells were bulging into the gut lumen. Later at 8-9 days of pi, spores or its developing stages leaked into the lumen either freely or enclosed within the globules of host cytoplasm. Besides columnar cells, development of $N.$ $bombycis$ was observed in the regenerative cells and rarely in goblet cells. Development of $N.$ $bombycis$ was also observed in both longitudinal and circular muscles at the late pi period. The histopathological changes, deformities and spore production time in the host were all influenced by the spore dosage and age of the host.