Abstract
This study aimed to determine the porcine circovirus type 2 (PCV2) serological and virological dynamics in piglets vaccinated at different ages in a PCV2 subclinical infection (PCV2-SI) scenario. Six hundred and forty-four 2 week-old healthy piglets were selected and distributed into four treatment groups: vaccination at 3, 6 or 10 weeks of age (3W-VAC, 6W-VAC and 10W-VAC groups, respectively) and unvaccinated pigs (NON-VAC group). Blood (n = 112 pigs) and oral fluid (OF) (n = 40 pens) samples were taken throughout the study to assess PCV2 load, humoral immunity and viral genotyping. Percentage of PCV2-DNA positive sera mainly raised by 10 weeks of age, being maximum at 14 weeks of age, and then started to decrease at 18 and 25 weeks of age. Specifically, PCV2 vaccination at 3 or 6 weeks of age yielded similar results, since they produced an earlier seroconversion and reduced, at different sampling points, the proportion of viremic animals in comparison to the unvaccinated group. In contrast, PCV2 vaccination at 10 weeks of age only achieved such reduction at 25 weeks of age; in this case, vaccination coincided with the increase of the percentage of viremic pigs in the population. Both serological techniques used in sera and OF offered similar results with a high and statistically significant correlation. In contrast, a higher percentage of PCV2 DNA positivity was detected in OF in comparison with sera. In conclusion, under the present study conditions, the optimal time for PCV2 piglet vaccination was at either 3 or 6 weeks of age.
Highlights
Porcine circovirus type 2 (PCV2) is one of the most prevalent viruses that cause great economic losses to the worldwide pig industry [1]
Quantification of PCV2 DNA Serum samples While very few pigs were qPCR positive at 3 and 6 weeks of age, the percentage of PCV2-DNA positive pig sera raised at 10 weeks of age, was maximum at 14 weeks of age and started to decrease by 18 and 25 weeks of age
Several studies have shown that PCV2 piglet vaccination at weaning age (3–4 weeks of age) is effective regardless of the Porcine circovirus diseases (PCVDs) farm status (PCV2-SD or PCV2 subclinical infection (PCV2-SI)) and the brand of commercial vaccine used [3]
Summary
Porcine circovirus type 2 (PCV2) is one of the most prevalent viruses that cause great economic losses to the worldwide pig industry [1]. This virus has an ubiquitous nature in the pig population and is the causative agent of a number of clinical and subclinical conditions named Porcine circovirus diseases (PCVDs) [2]. Efficacy of PCV2 commercial vaccines has been widely demonstrated under field conditions. The most common age of piglet vaccination against PCV2 is at 3–4 weeks of age (around weaning). Under no vaccinated sow scenario, little information is available whether the 3–4 week vaccination-age offers the best
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