Effect of a commercial paratyphus vaccine on the development of pigeon circovirus infection in young pigeons (Columba livia domestica).

Infection with pigeon circovirus (PiCV) has been associated with young pigeon disease syndrome (YPDS), which is considered to be a multifactorial disease. The factors that determine whether birds succumb to clinical disease are not known. To evaluate the potential effect of vaccination with a commercial paratyphus vaccine on the progression of PiCV infection in young pigeons, forty 6-week-old pigeons naturally infected with PiCV were randomly assigned to two equal groups. The pigeons of one group were vaccinated at 6 and 9 weeks of age, and pigeons of the second group were unvaccinated controls. Cloacal swab and blood samples collected from all the birds were tested for PiCV by polymerase chain reaction (PCR) analysis. Three weeks after the second vaccination, all pigeons were euthanatized, and tissues were collected for PiCV PCR analysis and histopathologic evaluation. No significant difference in the number of PCR-positive cloacal swab and blood samples was found between the vaccinated and control pigeons. Positive PCR results in tissue samples also were not significantly different between the groups, with 18 positive samples in vaccinated birds (90%) and 16 in control birds (80%). Characteristic botryoid inclusions were detected in more vaccinated than control pigeons, but this difference was not significant. In this study, vaccination with a commercial paratyphus vaccine was not a risk factor for development of young pigeon disease syndrome.