Retention of ingested porcine reproductive and respiratory syndrome virus in houseflies.
OBJECTIVE
To evaluate retention of porcine reproductive and respiratory syndrome virus (PRRSV) in houseflies for various time frames and temperatures.


METHODS
Fifteen 2-week-old pigs, two 10-week-old pigs, and laboratory-cultivated houseflies.


METHODS
In an initial experiment, houseflies were exposed to PRRSV; housed at 15 degrees, 20 degrees, 25 degrees, and 30 degrees C; and tested at various time points. In a second experiment to determine dynamics of virus retention, houseflies were exposed to PRRSV and housed under controlled field conditions for 48 hours. Changes in the percentage of PRRSV-positive flies and virus load per fly were assessed over time, and detection of infective virus at 48 hours after exposure was measured. Finally, in a third experiment, virus loads were measured in houseflies allowed to feed on blood, oropharyngeal washings, and nasal washings obtained from experimentally infected pigs.


RESULTS
In experiment 1, PRRSV retention in houseflies was proportional to temperature. In the second experiment, the percentage of PRRSV-positive houseflies and virus load per fly decreased over time; however, infective PRRSV was found in houseflies 48 hours after exposure. In experiment 3, PRRSV was detected in houseflies allowed to feed on all 3 porcine body fluids.


CONCLUSIONS
For the conditions of this study, houseflies did not support PRRSV replication. Therefore, retention of PRRSV in houseflies appears to be a function of initial virus load after ingestion and environmental temperature. These factors may impact the risk of insect-borne spread of PRRSV among farms.
Schurrer
Jennifer A
JA
Swine Disease Eradication Center, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108, USA.
Dee
Scott A
SA
Moon
Roger D
RD
Murtaugh
Michael P
MP
Finnegan
Colleen P
CP
Deen
John
J
Kleiboeker
Steven B
SB
Pijoan
Carlos B J
CB
D000818:Animals; D001826:Body Fluids / Q000821:virology; D017931:DNA Primers; D006793:Houseflies / Q000821:virology*; D019318:Porcine Reproductive and Respiratory Syndrome / Q000635:transmission*; D019316:Porcine respiratory and reproductive syndrome virus / Q000235:genetics*; D012044:Regression Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013552:Swine; D013553:Swine Diseases / Q000635:transmission* / Q000821:virology*; D013696:Temperature; D013997:Time Factors; D019562:Viral Load
D017931:DNA Primers