As if you needed one more thing to think about in terms of preventing or controlling porcine reproductive and respiratory syndrome in your herd, here’s one more. University of Minnesota research has shown that some insects help spread PRRS.

Insects can carry the virus up to 3.7 km. away from the source, notes Paul Yeske, DVM, St. Peter, Minn. Wind or vehicles can carry exposed flies or mosquitoes even further.

Yeske has divided insect control into two areas: controlling new insects from entering the herd, and controlling the insect population inside the barn. Since these are two different populations, you need to consider the control strategies separately.

1. Keeping insects out. This should be done at all production stages, and must be done in seedstock multiplication sites, says Yeske.

  • Use screens on both power-ventilated and naturally ventilated buildings. Power-ventilated facilities are affected the least by screening. Some ventilation experts contend that you need three to four times more air inlets once you add a screen. However, Yeske says in the retrofit units that he’s been involved with, his measurements have not shown a significant reduction in airflow with the same number of inlets.
  • You must keep the screen clean, monitoring it daily. You can clean it with a broom, leaf blower or water hose.
  • Screening on the interior surface of inlets, especially cool cells, has less problem with debris. However, it can pose a cleanliness challenge because materials can get trapped in inaccessible spaces.
  • Naturally ventilated facilities have had problems with airflow restrictions. Yeske says, about the only option is to increase air circulation and use misters on hot days. Some people have suggested putting the screens on a curtain-type device so they can be opened when temperatures rise to improve airflow. While there is some risk involved, it may be a reasonable alternative, he says.
  • Aluminum screening material is preferred, especially on the building exteriors. Grasshoppers can eat plastic screening material in just a few days. All ventilation entrances should be screened, including cool-cell openings, soffit openings to the attic, ridge-ventilation openings and curtain openings.
  • Spraying also can reduce insect populations around building sites. Spraying is required at least once a week to be effective. Private contractors are available to spray sites.

2. Controlling insects inside. This can be equally challenging. In addition to common-sense measures such as keeping facilities clean, spraying on a regular basis is recommended, or use a fogger with a pyrethrene-type compound. You can use small, timed sprayers in areas where insects are found.

  • Pheromone bait traps can be placed strategically through the facilities where you observe problems.
  • Natural predators also can assist with insect control, notes Yeske. Wasps are grown and available for purchase that eat fly larvae and can be put into the manure pit for fly control. Raybon in the feed can also help to control fly problems.

One way to determine virus presence and the amount of PRRS viral pressure in the area is to trap and test insects. Work with your herd veterinarian to tackle the testing portion of this task.