Studies on the duration of immunity induced in cattle after natural FMD infection and post vaccination with bivalent oil vaccine

Abstract

Aim: To detect the proper time for vaccination of infected calves after the onset of clinical signs and revaccination for previously vaccinated animals with bivalent FMD montanide ISA206 inactivated vaccine. Materials and Methods: Twenty calves naturally infected with foot and mouth disease (FMD) showing clinical signs represented by lesions on the tongue, buccal mucosa and feet. Samples were collected from these calves including tongue epithelial and oropharyngeal fluid (OP). The causative virus was isolated from such samples through inoculation of baby mice and typed by indirect Sandwich ELISA and was confirmed in 2 tongue epithelia samples using PCR. Results: The serum antibody titers were determined using SNT and ELISA in the sera of the 20 infected calves revealing that the infected farms should be vaccinated with inactivated bivalent FMD vaccine for (type O and A) Adjuvanted with montanide ISA206 after 32 weeks from the appearance of clinical signs. In addition the FMD immune status was monitored in 2 farms in EL-Fayoum and El-Sharkia Governorates where 50 calves in each farm were vaccinated with the bivalent FMD inactivated vaccine adjuvaned with montanide ISA206 and serum samples were collected monthly from these animals to determine their immune status using SNT and ELISA. The obtained results showed that vaccinated calves with the bivalent FMD montanide ISA206 inactivated vaccine should be revaccinated after 36 weeks post vaccination. Conclusions: naturally infected calves should be vaccinated on the 32 weeks post infection while vaccinated calves should be revaccinated on the 36 weeks post vaccination