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Table 3 Time for herds to obtain official PRRS free SPF status

From: Control and eradication of porcine reproductive and respiratory syndrome virus type 2 using a modified-live type 2 vaccine in combination with a load, close, homogenise model: an area elimination study

Herd PRRS free SPF status achieved Notes
F1B1 January 2015 July 2013: weaned ELISA and PCR positive piglets at study commencement
September 2013: weaned PCR negative but ELISA positive piglets
July 2014: three-week old piglets remained ELISA positive until July 2014
F1B2 January 2015 July 2013: weaned ELISA and PCR positive piglets at study commencement
September 2013: weaned PCR negative but ELISA positive piglets
November 2013: sentinels were about to be introduced, but two age groups tested PCR positive (5-week old and 7-week old piglets in nursery rooms). Sequencing revealed 99.17% homology to PRRS type 2 MLV
The nursery was depopulated to prevent PRRS spreading to the sows:
 Oldest pigs (26–32 kg) were exported out of the area
 Younger pigs (14–26 kg) were moved to isolation rooms in F1Q, vaccinated, then eventually slaughtered
 Piglets considered to be PCR negative were moved to F1WF2. (these were the only extra facilities available)
The nursery was cleaned and disinfected before repopulation
November 2014: two samples were close to the ELISA assay cut-off (SP > 0.4)
March 2015: one sample was ELISA positive, but simultaneously PCR negative. This was assumed to be false positive
F1WF1 Finishers depopulated in February 2015 October 2013: partially depopulated
October 2013–February 2014: ≤20% of samples tested from piglets were ELISA positive until age 6–7 weeks. All samples were PCR negative 100% of pigs older than 7 weeks were ELISA and PCR negative
February 2014: samples from 17-week old piglets were ELISA positive, but PCR negative
March 2014: 16- and 18-week pigs were found to be PCR and ELISA positive
April 2014: finisher rooms partially depopulated again. The site then remained PCR and ELISA negative until October 2014
October 2014: samples from 17- to 18-week old piglets were ELISA and PCR positive (possibly from F1WF2)
December 2014: samples from 11-week old piglets were ELISA negative, PCR positive. Samples from 13- to 15-week old piglets were both ELISA and PCR positive
January 2015: Total depopulation
F1WF2 January 2015 November 2013: received a batch of PCR positive pigs from F1B2 (although these were considered PRRS negative when moved). Lack of compliance with Golden Rule 8 meant the finisher rooms were continuously PCR positive until October 2014
October 2014: finisher barn depopulated, but infection probably spread to nearby F1WF1. Gradual repopulation from nursery. Herd then remained PCR and ELISA negative for the remainder of the study
F1F1 April 2015 October 2013: received depopulated (30 kg) pigs from F1WF1. Samples tested ELISA and PCR positive until March 2015, until the whole herd was depopulated
March 2015: repopulated
F1F2 January 2014 November 2013: received PRRS type 2 MLV vaccinated pigs from F1WF1 until October 2013. Partial depopulation. Received pigs from F1WF1 since November 2013 on an AIAO basis.
F1Q January 2015 July 2013. Mass vaccination of all gilts and sows (two times, 4 weeks apart, according to same schedule as in F1B1 and F1B2). Gilts remained in quarantine for 12 weeks. These gilts had been transferred to breeding herds by December 2013
November 2013: received pigs 14–26 kg from F1B2. These pigs were placed in an isolated room, vaccinated with PRRS type 2 MLV, then later slaughtered to prevent PRRSV from spreading to the rest of the site
January 2014: PRRS negative gilts bred elsewhere were introduced to gilt quarantine
April 2014: acclimatised (external) gilts were moved to breeding herds
F2B1 July 2014 July 2013: weaned PCR negative piglets at study commencement
F2B2 July 2014 July 2013: weaned PCR negative piglets at study commencement. Nursery rooms containing oldest two age groups were depopulated
F2F1 August 2015 (but no PRRS positive pigs since October 2013) July 2013: received PCR positive piglets from F2B2 at study commencement. From Weeks 0–10, all finisher pigs were vaccinated after introduction. Partially depopulated, and then only received PRRS negative animals
October 2013: samples tested PCR negative, and remained negative for the remainder of the study
F2F2 November 2013 July 2013: received PCR positive piglets from F2B2 at study commencement From Weeks 0–10, all finisher pigs were vaccinated after introduction. Partially depopulated, then received only PRRS negative animals
November 2013: samples tested PCR negative, and remained negative for the remainder of the study
F2F3 November 2013 July 2013: received PCR positive piglets from F2B2 at study commencement. From Weeks 0–10, all finisher pigs were vaccinated after introduction. Partially depopulated, then received only PRRS negative animals
November 2013: samples tested PCR negative, and remained negative for the remainder of the study
  1. Study commenced in July 2013. Positive-unstable defined as ELISA positive for PRRS antibody, and PCR positive for PRRSV RNA (actively shedding); positive-stable defined as ELISA positive for PRRS antibody in serum but PCR negative (not shedding)
  2. F1B1 Flow 1 Breeding Herd 1, F1B2 Flow 1 Breeding Herd 2, F1F1 Flow 1 Finisher Herd 1, F1F2 Flow 1 Finisher Herd 2, F1Q Flow 1 Quarantine, F1WF1 Flow 1 Wean-Finish 1, F1WF2 Flow 1 Wean-Finish 2, F2B1 Flow 2 Breeding Herd 1, F2B2 Flow 2 Breeding Herd 2, F2F1 Flow 2 Finisher Herd 1, F2F2 Flow 2 Finisher Herd 2, F2F3 Flow 2 Finisher Herd 3, PRRS porcine reproductive and respiratory syndrome