Efficacy Studies of a Trivalent Vaccine Containing PCV-2a, PCV-2b Genotypes and Mycoplasma hyopneumoniae When Administered at 3 Days of Age and 3 Weeks Later against Porcine Circovirus 2 (PCV-2) Infection

Abstract

Four studies under preclinical and clinical conditions were performed to evaluate the efficacy of a new trivalent vaccine against Porcine circovirus 2 (PCV-2) infection. The product contained inactivated PCV-1/PCV-2a (cPCV-2a) and PCV-1/PCV-2b (cPCV-2b) chimeras, plus M. hyopneumoniae inactivated cell-free antigens, which was administered to piglets in a two-dose regime at 3 days of age and 3 weeks later. The overall results of preclinical and clinical studies show a significant reduction in PCV-2 viraemia and faecal excretion, and lower histopathological lymphoid lesions and PCV-2 immunohistochemistry scores in vaccinated pigs when compared to non-vaccinated ones. Furthermore, in field trial A, a statistically significant reduction in the incidence of PCV-2-subclinical infection, an increase in body weight from 16 weeks of age to slaughterhouse and an average daily weight gain over the whole period (from 3 days of age to slaughterhouse) was detected in the vaccinated group when compared to the non-vaccinated one. Circulation of PCV-2a in field trial A, and PCV-2b plus PCV-2d in field trial B was confirmed by virus sequencing. In conclusion, a double immunization with a cPCV-2a/cPCV-2b/M. hyopneumoniae vaccine was efficacious against PCV-2 infection by reducing the number of histopathological lymphoid lesions and PCV-2 detection in tissues, serum, and faeces, as well as reducing losses in productive parameters.

Pathological features of the lungs and liver of piglets under conditions of constant vaccination of livestock against circovirus infection

“…Circovirus diseases are widespread in pigs farming in almost all countries of the world, and Russia is no exception. Meanwhile vaccination is the main way of preventing viral infection [12,15].…”

“…According to [15], PCV2 in animals affects lymphoid tissue. In the lungs the lymphoid tissue is associated with the bronchi, ensuring the flow of immune reactions.…”

“…The main method of preventing pigs' circovirus diseases is vaccination. Among the prophylactic agents, PCV2 vaccines are the ones of the best-selling vaccines in pig farming [12,15], as their use reduces mortality, decreases the culling rate of young animals, occurrence of concomitant diseases, and also increases the growth rate of the animals. After vaccination, virus-neutralizing antibodies appear in the body of pigs, and factors of humoral and cellular immunity are activated, thus determining the level of "immunological "protection" [14].…”

Efficacy Studies against PCV-2 of a New Trivalent Vaccine including PCV-2a and PCV-2b Genotypes and Mycoplasma hyopneumoniae When Administered at 3 Weeks of Age

“…Interestingly, some studies showed a closer genetic and antigenic relation between PCV-2b and PCV-2d sequences compared to PCV-2a and PCV-2d sequences [20,23]. Hence, a bivalent vaccine containing PCV-2a and PCV-2b genotypes may be a relevant option to face against the several PCV-2 genotypes that are circulating under field conditions [25,26]. In addition to PCV-2, Mycoplasma hyopneumoniae (M. hyopneumoniae) is also an important pathogen that usually circulates in pigs during the postweaning period.…”

“…Different PCV-2 vaccination regimens are already studied and commercialised. In fact, this chimeric vaccine has already shown efficacy in pre-clinical and clinical trials applied in a split-dose immunisation regime at three days of age and three weeks later [26]. This latter regime is especially interesting in those farms where PCV-2 infection is detected at early stages of life (lactating or early nursery periods) or when herd immunity is poor.…”