PRRSv outbreak control in a naive herd

Clinical signs
	Abortion storm – particularly North American strains
	Rolling inappetance in gestation sows
	Early farrowing/late abortions – 112 days gestation
	Sudden deterioration in health of piglets in farrowing house
Treatment
General	Acetylsalicylic acid (aspirin) 20mg/kg in the water supply
	Vaccinate whole adult population with a commercial live vaccine
	Feed back programme – need to vaccinate with the current (new) farm strain. Materials that might be useful:
		Faeces from aborted sows
		Poor piglets less than 10 days of age – kill and macerate include stillborn and mummified piglets
		Tonsilar scrape from aborted sows
		Previously frozen serum (if available) to make an autogenous vaccine if used previously. Note this may be a new strain.
	Note: This may increase chance of further abortions. However, these susceptible sows would have aborted when they became infected anyway. By the combination of a reduced infective dose and treatments the abortions should be reduced
	10 days after initial vaccination/feedback etc revaccinate whole herd with a dead PRRSv vaccine. This reduces the shedding time of PRRSv from infected animals
Additional considerations
Breeding Gestation	Increase the number of sows bred
	Increase number of doses of semen – from 2 to 3 or increase semen concentration in semen dose
	Stop culling of sows wherever possible
	Raise dry sow temperature to 21C
	Avoid large temperature change: temperature drops at night or peaks during day
	Increase feed intake by 0.25 to 0.5 kg a day for next four weeks
	Individual sows may require individual antimicrobial treatments and flunixin (2.2mg/kg) or equivalent
Farrowing	Raise farrowing house temperature to 22C
	Provide more straw, shavings or paper if possible
	Provide extra heat for surviving piglets
Farm	Ensure pig flow is correct – vital to stop over and understocking
	Enhance cleaning to reduce pathogen load around the farm
Intermediate Control
	Feed-back, tonsilar swab vaccination to all new gilts on entrance to the farm
	Administer dead vaccine 10 days after entrance
	Biosecurity review all practices and enhance loop holes
	Note AI source, live genetic source, locality as primary sources

Investigation
Initial	Bleed sows and look for PRRSv RNA by PCR
	Bleed sows for antibodies but this may take 21 days post-infection
	Sequence recovered PRRSv to help determine source – compare with previous strains on the farm if previously positive
	Bleed any gilts in isolation by PCR and antibody levels
	Examine AI for PRRSv by PCR
Long term measures
	Assuming that the biosecurity breach is controllable
	Reassess situation, introduce gilts and close farm for 6 months to restore PRRSv negative status - link
	There is only one control measure for PRRSv – negative status but must be more than 1.5 km from another pig farm and have excellent biosecurity
	Adopt on-farm AI only or frozen semen for new genetics

Major clinical signs of a PRRSv break in a naïve herd

Rolling inappetance in sows and gilts	Abortion storms
Early farrowing with late mummified piglets	Weak piglets in the farrowing house – increase in diarrhoea with E. coli and Rotavirus