Related Experiment Video
Updated: Jun 15, 2026
Maintaining Aedes aegypti Mosquitoes Infected with Wolbachia
Published on: August 14, 2017
Asymmetric biparental and inefficient horizontal transmission of paralysis-causing sigmavirus in Queensland fruit fly
Sanjay Kumar Pradhan1,2,3,4, Jennifer L Morrow5, Geraldine Tilden5
1Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia. spradhan314@uky.edu.
Abstract:
Insects are associated with diverse RNA viruses, including vertically transmitted viruses that form persistent infections without apparent symptoms. One of the first documented vertically transmitted viruses is a sigmavirus (Rhabdoviridae) affecting fitness of Drosophila. Sigmaviruses and related rhabdoviruses have also been detected in pest fruit flies and other arthropods. However, their prevalence, transmission, tissue localisation and fitness effects remain poorly known, despite their potentially common infections in diverse hosts. We investigated Sigmavirus tryoni (BtSV) prevalence, load, transmission across multiple generations and host effects in Queensland fruit fly (Bactrocera tryoni), Australia's most significant horticultural pest, which carries BtSV at low prevalence (13.7%) across field populations. We detected BtSV in 6 of 12 laboratory populations (at a prevalence of 12.5% to 80.4%) where it was transmitted biparentally within embryos. Although incomplete, maternal transmission was more reliable and resulted in higher BtSV load than paternal transmission. Paternally transmitted BtSV was almost entirely lost after two generations. BtSV became detectable in most uninfected individuals cohabiting with infected flies, but this resulted in a low load that was subsequently transmitted to only few offspring. BtSV occurred across developmental stages, digestive and reproductive tissues, albeit its viral load was lower in reproductive tissues when received paternally than maternally, and lower in testes than ovaries. Furthermore, BtSV-infected individuals suffered paralysis and mortality when exposed to high CO2 concentrations at low temperature, a Rhabdoviridae effect previously reported for Drosophila species, a muscid fly and mosquitoes. Our study suggests that sigmavirus transmission dynamics and fitness effects may apply broadly to arthropod hosts and affect their management.
Insights
Sigmavirus tryoni (BtSV) infects the Queensland fruit fly, with maternal transmission being more effective than paternal. Infected flies exhibit paralysis and mortality under specific environmental conditions, impacting pest management strategies.
Area of Science:
- Arthropod-borne viruses
- Insect pathology
- Viral transmission dynamics
Background:
- Sigmaviruses (Rhabdoviridae) are RNA viruses known to infect insects, including Drosophila, with potential implications for host fitness.
- Vertical transmission and its effects on host populations are poorly understood for many insect-associated viruses.
- The Queensland fruit fly (Bactrocera tryoni) is a significant horticultural pest where sigmavirus prevalence and impact require further investigation.
Purpose of the Study:
- To investigate the prevalence, transmission dynamics (across generations), tissue localization, and fitness effects of Sigmavirus tryoni (BtSV) in the Queensland fruit fly (Bactrocera tryoni).
- To understand the mechanisms of viral transmission, including maternal and paternal routes, and their efficiency.
- To assess the impact of BtSV infection on fruit fly survival and behavior under specific environmental stressors.
Main Methods:
- Field sampling and laboratory-rearing of Bactrocera tryoni to determine BtSV prevalence.
- Multi-generational experiments to track viral transmission and load.
- Quantitative analysis of viral distribution in various host tissues (digestive, reproductive).
- Controlled exposure experiments to assess fitness effects (paralysis, mortality) under high CO2 and low temperature.
Main Results:
- BtSV was detected in field populations (13.7%) and varied significantly in laboratory populations (12.5%–80.4%).
- Biparental transmission occurred within embryos, with maternal transmission being more reliable and resulting in higher viral loads than paternal transmission.
- Paternally transmitted BtSV was largely lost by the second generation; horizontal transmission was inefficient.
- BtSV was present in various tissues, with higher loads in reproductive tissues via maternal transmission and in ovaries compared to testes.
- Infected flies experienced paralysis and mortality when exposed to high CO2 concentrations at low temperatures.
Conclusions:
- Sigmavirus transmission dynamics and fitness effects observed in fruit flies may be broadly applicable to other arthropod hosts.
- BtSV infection can impact fruit fly survival under specific environmental conditions, suggesting potential avenues for pest management.
- Understanding the complex transmission routes and host-virus interactions is crucial for managing sigmavirus in insect populations.
