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Alternative Routes for the Horizontal Transmission of a Nucleopolyhedrovirus
1Ecology and Biocontrol Group, NERC Institute of Virology and Environmental Microbiology, Oxford, OX1 3SR, United Kingdom
Abstract:
Two alternative routes for nucleopolyhedrovirus transmission were investigated using Mamestra brassicae larvae: cannibalism of infected larvae and the release of virus prior to the death of the diseased host. The low frequency of cannibalism observed suggests that this is not a relevant transmission route in this species. However, larvae were shown to transfer viable virus to the environment before death through either defecation or regurgitation. Over 40% mortality was observed in larvae reared in diet containers where infected hosts had previously fed. Virus transfer to cabbages also occurred before death of the infected host, as revealed by plant bioassay. Virus was not detected in the feces or regurgitate of diseased larvae until the late stages of infection.
Insights
Cannibalism is an unlikely transmission route for Mamestra brassicae nucleopolyhedrovirus. Infected larvae shed viable virus before death via feces or regurgitation, leading to significant mortality in healthy larvae.
Area of Science:
- Entomology
- Virology
- Insect Pathology
Background:
- Nucleopolyhedroviruses (NPVs) are significant pathogens of insects, impacting agriculture.
- Understanding NPV transmission routes is crucial for developing effective biocontrol strategies.
Purpose of the Study:
- To investigate two alternative transmission routes for Mamestra brassicae nucleopolyhedrovirus (MbNPV).
- To determine the relevance of larval cannibalism versus pre-mortem virus shedding for MbNPV transmission.
Main Methods:
- Mamestra brassicae larvae were experimentally infected with MbNPV.
- Cannibalism frequency was observed.
- Virus shedding via defecation and regurgitation was assessed.
- Larval exposure to contaminated diet and plant surfaces was evaluated through bioassays.
Main Results:
- Low frequency of cannibalism observed, suggesting it's not a primary transmission route for MbNPV.
- Infected larvae shed viable MbNPV in feces and regurgitate before death.
- Significant mortality (>40%) occurred in larvae exposed to contaminated diet.
- Virus transfer to plant surfaces (cabbages) was confirmed before host death.
Conclusions:
- Pre-mortem shedding of viable nucleopolyhedrovirus by infected larvae is a significant transmission route.
- This shedding contaminates the environment, leading to infection of healthy individuals.
- Cannibalism plays a minor role in MbNPV transmission in Mamestra brassicae.