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Effect of blood source on vector competence of Culex pipiens biotypes for Usutu virus
Sandra R Abbo1, Tessa M Visser2, Constantianus J M Koenraadt2
1Laboratory of Virology, Wageningen University & Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands.
Background:
Infectious blood meal experiments have been frequently performed with different virus-vector combinations to assess the transmission potential of arthropod-borne (arbo)viruses. A wide variety of host blood sources have been used to deliver arboviruses to their arthropod vectors in laboratory studies. The type of blood used during vector competence experiments does not always reflect the blood from the viremic vertebrate hosts in the field, but little is known about the effect of blood source on the experimental outcome of vector competence studies. Here we investigated the effect of avian versus human blood on the infection and transmission rates of the zoonotic Usutu virus (USUV) in its primary mosquito vector Culex pipiens.
Methods:
Cx. pipiens biotypes (pipiens and molestus) were orally infected with USUV through infectious blood meals containing either chicken or human whole blood. The USUV infection and transmission rates were determined by checking mosquito bodies and saliva for USUV presence after 14 days of incubation at 28 °C. In addition, viral titers were determined for USUV-positive mosquito bodies and saliva.
Results:
Human and chicken blood lead to similar USUV transmission rates for Cx. pipiens biotype pipiens (18% and 15%, respectively), while human blood moderately but not significantly increased the transmission rate (30%) compared to chicken blood (17%) for biotype molestus. USUV infection rates with human blood were consistently higher in both Cx. pipiens biotypes compared to chicken blood. In virus-positive mosquitoes, USUV body and saliva titers did not differ between mosquitoes taking either human or chicken blood. Importantly, biotype molestus had much lower USUV saliva titers compared to biotype pipiens, regardless of which blood was offered.
Conclusions:
Infection of mosquitoes with human blood led to higher USUV infection rates as compared to chicken blood. However, the blood source had no effect on the vector competence for USUV. Interestingly, biotype molestus is less likely to transmit USUV compared to biotype pipiens due to very low virus titers in the saliva.
Insights
The blood source did not impact Usutu virus (USUV) transmission by Culex pipiens mosquitoes. However, human blood meals increased USUV infection rates, and one mosquito biotype showed lower transmission potential.
Area of Science:
- Medical Entomology
- Virology
- Infectious Diseases
Background:
- Arthropod-borne viruses (arboviruses) transmission potential is assessed using infectious blood meal experiments.
- Laboratory studies often use varied blood sources, which may not reflect natural conditions, impacting vector competence findings.
- The effect of blood source on experimental outcomes for vector competence studies remains underexplored.
Purpose of the Study:
- To investigate the influence of avian (chicken) versus human blood on Usutu virus (USUV) infection and transmission rates.
- To evaluate these effects in the primary mosquito vector, Culex pipiens, specifically its biotypes pipiens and molestus.
Main Methods:
- Culex pipiens biotypes were orally infected with USUV using blood meals containing either chicken or human whole blood.
- Mosquito bodies and saliva were tested for USUV 14 days post-incubation at 28°C to determine infection and transmission rates.
- Viral titers in USUV-positive mosquito bodies and saliva were quantified.
Main Results:
- USUV infection rates were higher in both Cx. pipiens biotypes when fed human blood compared to chicken blood.
- Transmission rates were similar for Cx. pipiens biotype pipiens with human or chicken blood.
- Biotype molestus showed a non-significantly increased transmission rate with human blood but had significantly lower USUV saliva titers than biotype pipiens.
Conclusions:
- While human blood meals led to higher USUV infection rates, the blood source did not ultimately affect vector competence.
- Culex pipiens biotype molestus demonstrated a reduced capacity to transmit USUV, primarily due to lower viral titers in its saliva.
- These findings highlight the importance of considering blood source in arbovirus vector competence studies.
