Title : A review on bombyx mori: Microbial, viral and parasitoid diseases, detection and control
Abstract:
The mulberry silkworm, Bombyx mori, is the most dominant and economically important domestic silkmoth in sericulture farming. It produces the best quality of silk fibers owing to its desirable traits of a much larger progeny size, short life span, and low maintenance cost. However, Bombyx mori is being infected with several diseases throughout the year, especially during rainy and winter seasons that cause severe crop losses to farmers. Diseases in mulberry silkworms are caused by fungi, microsporidians, bacteria, viruses, and parasitoids. Muscardine is caused by fungal pathogens.which include Beauveria bassiana, Metarrhizium anisopliae, Aspergillus flavus, A. tamarii, and Nomuraea rileyi. The highly fatal pebrine is caused by Microsporidium sp., Nosema bombycis, Pleistophora sp., Thelophania sp., and Vairomorpha sp. Bacterial infections are caused by Streptococcus faecalis, S. faecium, Serratia marcescens, Staphylococcus, and Bacillus thuringiensis. Viral pathogens causing flacherie and grasserie are the B. mori nucleopolyhedrovirus (BmNPV), B. mori densovirus (BmDNV), B. mori infectious flacherie (BmIFV), and B. mori cytoplasmic polyhedrosis virus (BmCPV). There are also a few parasitoids Exorista bombycis and dermestid beetle that lay eggs on silkworm larvae and cocoons, respectively. Contaminated rearing houses is the most common route of fungal conidia on the silkworm body causing white or green muscardine. Whereas microsporidia infect the silkworms with the lethal pebrine through transovarian transmission, consumption of contaminated mulberry leaves, contaminated rearing houses and appliances. B. mori gets infected with flacherie and grasserie viruses upon feeding on contaminated mulberry leaves, fecal matter and body fluids that come in contact with skin injuries or wounds. Several efficient approaches are being conducted for disease monitoring, early diagnosis and control of these silkworm diseases. Microscopic examinations and histopathology are the usual methods being employed for initial diagnosis of silkworm diseases. However, it may not be practical for viruses. A more reliable and accurate method to detect viral and microsporidian diseases is the use of antigen-antibody serological testing. This includes enzyme-linked immunosorbent assay (ELISA), immunoblotting, precipitin, fluorescent antibody and the commonly used dipstick assays. Meanwhile, Digital gene expression (DEGs) profiling or transcriptome analysis is a molecular approach to screen activated genes silkworm for its early response to Beauveria bassiana. Since there is no effective strategy for treating muscardine, infected silkworms must be disposed or burned immediately. Chemotherapy by feeding fungicides to the infected 2nd instar silkworms are proven effective in containing muscardine and microsporidiasis. B. mori infected with Bacillus thuringensis can be treated with botanicals such as Ocimum basilicum, Morus alba, and Nigella sativa to reduce larval mortality rate and an additional advantage of increased weight of the larva, cocoon weight and cocoon shell. Nevertheless, since there is no single approach to effectively eradicate this deadly B. mori diseases, immediate isolation of the infected and diseased larva should be done, continuous disinfection of the rearing facilities, control of mulberry pests, and proper sanitation should be observed throughout silkworm rearing. It is imperative to observe strict management practices in sericulture farming since preventive measure is the only key for a disease-free B. mori silkworm larva.
Audience Take Away Notes:
- The academe, farmers, agriculturists and researchers will be updated on the complete incidence and diagnostic tools of the various lethal Bombyx mori diseases
- Sericulture farmers may adapt the efficient management practices being done by every country in their respective rearing facilities
- In the academe, both the faculty and students can explore the molecular mechanisms involving gene expressions in Bombyx mori in their response to various fungal, microbial, viral, and parasitoid pathogens
- This will serve as a baseline information to improve the detection, diagnosis, and treatment of Bombyx mori infections
- This can serve as a guide to determine the ideal parental moth strains that are resistant to the majority of Bombyx mori diseases
