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Sublethal dose of phoxim and Bombyx mori nucleopolyhedrovirus interact to elevate silkworm mortality
ZhiYa Gu1, FanChi Li1, JingSheng Hu1
1School of Basic Medicine and Biological Sciences, Soochow University, Suzhou, Jiangsu, China.
Background:
Silkworm (Bombyx mori) is an economically important insect. It is relatively less resistant to certain chemicals and environment exposures such as pesticides and pathogens. After pesticide exposures, the silkworms are more susceptible to microbial infections. The mechanism underlying the susceptibility might be related to immune response and oxidative stress.
Results:
A sublethal dose of phoxim combined with Bombyx mori nucleopolyhedrovirus (BmNPV) elevated the silkworm mortality at 96 h. We found a higher content of H2 O2 and increased levels of genes related to oxidative stress and immune response after treatment with a sublethal dose of phoxim for 24 h or 48 h. However, such response decreased with longer pesticide treatment. Mortality increased by 44% when B. mori was exposed to combined treatment with BmNPV and phoxim rather than BmNPV alone. The level of examined immune-related and oxidative-stress-related genes significantly decreased in the combined treatment group compared with the BmNPV group. Our results indicated that, with long-term exposure to pesticides such as OPs, even at sublethal dose, the oxidative stress response and immune responses in silkworm were inhibited, which may lead to further immune impairment and accumulation of oxidative stress, resulting in susceptibility to the virus and harm to the silkworm.
Conclusion:
Our study provided insights for understanding the susceptibility to pathogen after pesticide exposures, which may promote the development of better pesticide controls to avoid significant economic losses. © 2016 Society of Chemical Industry.
Insights
Pesticide exposure, even at low doses, can suppress silkworm (Bombyx mori) immune and oxidative stress responses. This impairment increases susceptibility to viral infections like Bombyx mori nucleopolyhedrovirus (BmNPV), leading to higher mortality and economic losses.
Area of Science:
- Entomology
- Toxicology
- Immunology
Background:
- Silkworms (Bombyx mori) are economically vital but vulnerable to pesticides and pathogens.
- Pesticide exposure can increase susceptibility to microbial infections.
- Mechanisms may involve immune response and oxidative stress.
Purpose of the Study:
- Investigate the impact of sublethal phoxim exposure on silkworm immunity and oxidative stress.
- Determine the combined effects of phoxim and Bombyx mori nucleopolyhedrovirus (BmNPV) on silkworm mortality and immune function.
Main Methods:
- Treatment of silkworms with sublethal phoxim doses for 24-48 hours.
- Exposure to a combination of phoxim and BmNPV.
- Measurement of hydrogen peroxide (H2O2) content.
- Gene expression analysis for oxidative stress and immune response markers.
Main Results:
- Sublethal phoxim exposure increased oxidative stress and immune gene expression initially, but decreased with longer exposure.
- Combined phoxim and BmNPV treatment significantly increased silkworm mortality (44%) compared to BmNPV alone.
- Key immune and oxidative stress genes were downregulated in the combined treatment group.
Conclusions:
- Long-term, sublethal pesticide exposure inhibits silkworm oxidative and immune responses.
- This inhibition leads to immune impairment and increased susceptibility to viral pathogens like BmNPV.
- Findings aid in developing better pesticide strategies to prevent economic losses in sericulture.
