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Persistence and Retention of Porcine Reproductive and Respiratory Syndrome Virus in Stable Flies (Diptera: Muscidae)
K Rochon1, R B Baker2, G W Almond3
1University of Manitoba, 214 Entomology Bldg., Winnipeg, Manitoba, Canada, R3T 2N2. kateryn.rochon@umanitoba.ca.
Abstract:
We investigated the acquisition of porcine reproductive and respiratory syndrome (PRRS) virus by the stable fly (Diptera: Muscidae; Stomoxys calcitrans (L.)) through a bloodmeal, and virus persistence in the digestive organs of the fly using virus isolation and quantitative reverse-transcription PCR (qRT-PCR). Stable flies were fed blood containing live virus, modified live vaccine virus, chemically inactivated virus, or no virus. Stable flies acquired PRRSV from the bloodmeal and the amount of virus in the flies declined with time, indicating virus did not replicate in fly digestive tissues. Virus RNA was recovered from the flies fed live virus up to 24 h postfeeding using virus isolation techniques and 96 h using qRT-PCR. We further examined the fate of PRRSV in the hemolymph of the flies following intrathoracic injection to bypass the midgut barrier. PRRSV was detected in intrathoracically inoculated adult stable flies for 10 d using qRT-PCR. In contrast to what we observed in the digestive tract, detectable virus quantities in the intrathoracically inoculated stable flies followed an exponential decay curve. The amount of virus decreased fourfold in the first 3 d and remained stable thereafter, up to 10 d.
Insights
Stable flies can acquire porcine reproductive and respiratory syndrome virus (PRRSV) through a bloodmeal, but the virus does not replicate in their digestive system. PRRSV RNA persists in flies for up to 96 hours after feeding.
Area of Science:
- Veterinary Entomology
- Virology
- Insect Vector Biology
Background:
- Porcine reproductive and respiratory syndrome virus (PRRSV) is a significant pathogen in swine production.
- Stable flies (Stomoxys calcitrans) are known vectors of various pathogens.
- The potential role of stable flies as mechanical vectors for PRRSV requires investigation.
Purpose of the Study:
- To determine if stable flies can acquire PRRSV via a bloodmeal.
- To assess PRRSV persistence and replication in the digestive organs of stable flies.
- To evaluate PRRSV fate in stable fly hemolymph after bypassing the digestive tract.
Main Methods:
- Stable flies were fed blood containing live, modified live vaccine, or inactivated PRRSV.
- Virus isolation and quantitative reverse-transcription PCR (qRT-PCR) were used to detect and quantify PRRSV.
- PRRSV was also introduced into fly hemolymph via intrathoracic injection to bypass the midgut.
Main Results:
- Stable flies acquired PRRSV from infected bloodmeals.
- PRRSV did not replicate in the digestive tissues; viral RNA was detected up to 96 hours postfeeding (qRT-PCR).
- PRRSV was detected in hemolymph for up to 10 days after intrathoracic inoculation, exhibiting exponential decay.
Conclusions:
- Stable flies can acquire and retain PRRSV RNA after feeding on infected blood.
- The virus does not replicate within the stable fly's digestive system.
- PRRSV can persist in stable fly hemolymph for an extended period, suggesting potential for mechanical transmission.
