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Timing Crucial for Circovirus Vaccination

by 5m Editor
7 November 2008, at 12:00am

The timing of vaccination against porcine circovirus (PCV) and the thoroughness of the vaccination programme are essential to ensure a reduction in death loss in the herd improved weight gain, writes ThePigSite Senior Editor, Chris Harris.

These were some of the results of a trial conducted by veterinarian Pat Graham DVM from the Ghrist Veterinary Clinic in the US, which he discussed earlier this year during the World Pork Expo.

Dr Graham said that initial studies on pig farms had shown that without vaccination, health problems such as Mycoplasma hyopneumoniae, ileitis and circovirus had started to creep in - even with measures to separate animals with farrowing crates and by keeping nursery and finished barns apart.

The trial looked at 8 x 600-head nursery houses and 9 x 1200-head finisher houses.

Without vaccination, the disease situation on the farms grew progressively worse with signs of respiratory and enteric diseases so that culls increased and the mortalities in the herd increased.

With diseases such as PRRS, Mycoplasma hyopneumoniae, Streptococcus A suis, ileitis and PCV2 being found increasing in the herds, Dr Graham said that without vaccination the diseases had to work their way through the herds and that euthanasia levels rose, particularly as PCV2 was non-treatable at the time. Antibiotic treatment is ineffective and vaccines had yet to be developed.

However, he said that the disease was found in the finisher pigs and the nursery pigs were not affected.

The weaning age was increased from 16 to 20 days, but the finisher herd performance crashed with increased mortalities three to four weeks into finishing. The pigs showed signs of scours, wasting and skin lesions, and euthanasia was the only solution.

However, the first vaccination programme was started in 2006, and although the rate of death loss remained much the same, the pigs that were not affected with disease did well and showed weight gain.

As the pigs started to show signs of disease at three to four weeks into finishing, the vaccination programme was started before this time and then repeated two and a half weeks later.

Dr Graham said that when the pigs were vaccinated late against circovirus, there was still a high death rate at three, four and five weeks into finishing. He added that because the nursery pigs were unaffected, it became clear that the virus was circulating in the building and they did not manage to reduce mortalities until all the finisher pigs on the site were vaccinated.

He added that once the circovirus had been eliminated from the pigs, vaccination against PRRS was stopped and although the animals did contract PRRS and flu symptoms, these went away with antibiotics.

Vaccination Increased Daily Weight Gain

With the circovirus vaccine, the average daily weight gain rose from 1.85 lbs to 2.05 lbs, feed conversion improved and more pigs survived.

With just medication, mortality was about 17 per cent but with vaccination, this was reduced to just two per cent.

"The circovirus vaccine has improved finishing and given healthier pigs," he said.

"The circovirus vaccine is very beneficial to use, but you have to have every pig vaccinated and vaccinated at an appropriate age," said Dr Graham, who added that even without the virus in the herd, mortality was higher in those groups of pigs that had not been vaccinated compared to those that had been vaccinated.

Dr Brad Thacker, DVM, MBA, Ph.D., from Intervet/Schering-Plough Animal Health said that it was not good enough for pig producers to say that just because they do not have a circovirus problem, they had no need to vaccinate.

He said that it is a devastating disease and trials have shown that the performance of the pigs increases with vaccination.

He said that licensing studies have shown that the optimum time to vaccinate is between three and four weeks of age, and that vaccinating at eight weeks starts to become a challenge.

Several studies in Canada had shown that with vaccination an overall 77 per cent reduction in mortality had been achieved and he said that although a single dose vaccination had proved fairly good, a double dose had given a much better response.

The tests they had carried out had shown that with vaccination at between three to five weeks, mortality had reduced from 18 per cent to seven per cent.

He said that the pigs, vaccinated at 23 days and then 44 days had shown a 5.2 per cent weight difference to those pigs that had not been vaccinated.

The timing of the vaccination was critical, he said, because the pigs lose their maternal antibodies at about 12 weeks, so they had to be vaccinated by nine to 12 weeks at the latest.

Field Test Confirms Results

Mortality and Cull Light Pig Data

Other analysis of Intervet/Schering-Plough's Circumvent PCV vaccine took place on a 1700-sow farrow-to-finish operation in the Midwest of America.

The field test took a subset of pigs for periodic blood sampling, with at least one pig in a latter being sampled. Samples were collected at 3, 6, 9, 12, 15 and 21 weeks of age and tested for PCV2 antibodies by ELISA.

The study data showed that vaccination with Circumvent PCV reduced mortality rate and the vaccinated group outperformed the control group during the grower and finisher stages.

Growth Data

Intervet/Schering Plough added that the data showed that the control pigs lost their maternal antibodies at 12 weeks of age and started sero-converting at between 12 and 15 weeks. It also showed that exposure to PCV2 occurred after the pigs had entered the finishing facility. The levels of maternal antibodies at vaccination did not influence the efficacy of the vaccine.

Results of Sero-testing by PCV2 ELISA

Further Reading

- Find out more information on Post-Weaning Multisystemic Wasting Syndrome (PMWS) by clicking here.


November 2008