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Pathology of an iridescent virus in immature Culex pipiens L. (Diptera, Culicidae)
Evangelina Muttis1, María Victoria Micieli1, Juan José García1
1Centro de Estudios Parasitológicos y Vectores (CEPAVE) (CONICET, CCT-La Plata, UNLP), Boulevard 120 S/N, PC 1900, La Plata, Buenos Aires, Argentina.
Abstract:
Iridovirus in Culex pipiens was reported for the first time in 2012. Later studies of horizontal transmission were performed, in which an interaction with the parasite Strelkovimermis spiculatus acting as viral vector was recognized. In the present study, we observed aspects of the pathology produced by an invertebrate iridescent virus in laboratory infected immature Cx. pipiens as well as in infected immature Cx. pipiens in the field. In the laboratory infected larvae, the infection and mortality were asynchronous. Signs of infection in larvae exposed to the virus were observed between the second and the fourth days post-exposure in 99% of the cases, while the highest daily record of visible infected larvae (52%) was observed on the third day post exposure. Moreover, 79% of confirmed virus infected larvae died in the first 10 days after exposure. The Median Lethal Time was eight days. Several tissues were found to be infected and the common sites of replication were the fat body, epidermis and epithelial derivatives, such as the imaginal discs and the tracheal epithelium. Moreover, infection in the salivary glands, gastric ceca and posterior gut have not been previously documented on other mosquito iridescent viruses.
Insights
Invertebrate iridescent virus caused asynchronous infection and mortality in Culex pipiens larvae. The virus replicated in new tissues, including salivary glands and gastric ceca, impacting mosquito populations.
Area of Science:
- Veterinary Entomology
- Invertebrate Pathology
Background:
- Iridovirus infections in Culex pipiens mosquitoes were first documented in 2012.
- Subsequent research identified horizontal transmission, involving the parasite Strelkovimermis spiculatus as a viral vector.
Purpose of the Study:
- To investigate the pathology of invertebrate iridescent virus (IIV) in laboratory-infected and field-collected immature Culex pipiens (Cx. pipiens).
- To identify novel sites of viral replication within Cx. pipiens.
Main Methods:
- Laboratory infection of immature Cx. pipiens larvae with IIV.
- Field collection of infected immature Cx. pipiens.
- Observation of infection signs, mortality rates, and median lethal time (LT50).
- Histopathological examination to determine viral replication sites.
Main Results:
- Laboratory infections and mortality were asynchronous, with signs appearing 2-4 days post-exposure and peak infection on day 3.
- 79% of infected larvae died within 10 days, with an LT50 of 8 days.
- Viral replication occurred in the fat body, epidermis, imaginal discs, and tracheal epithelium.
- Novel sites of infection, including salivary glands, gastric ceca, and posterior gut, were identified.
Conclusions:
- Invertebrate iridescent virus infection in Cx. pipiens exhibits asynchronous progression and significant larval mortality.
- The virus infects a broader range of tissues than previously documented for mosquito iridescent viruses, with implications for vector control.
