Hematological characterization and immunogenicity of intraocular administrated peste des petits ruminants vaccine in goats

Peste des petits ruminants (PPR) is a highly contagious and transboundary viral disease affecting small ruminants mainly in Africa, Asia, and Middle East. To control the disease spread, a live attenuated PPR vaccine containing Nigeria/75/1 strain has been administrated either through transdermal (subcutaneous) or mucosal (intranasal) routes in the susceptible animals. However, similar to intranasal, intraocular route of vaccine administration is also considered effective and safe in providing the mucosal and systematic immunity in the vaccinated animals. In the current study, the immunogenic efficiency and hematological changes associated with new in-house developed inactivated vaccine using Nigeria/75/1 strain were compared following administration through intraocular and subcutaneous routes. The goats were divided into five groups in which four groups were vaccinated through intraocular, intramuscular, intranasal, and subcutaneous routes while one group was kept as unvaccinated control. The vaccinated goats were administrated with single vaccine dose and monitored for 56 days where clinical signs, serum neutralizing antibodies through ELISA and hematological changes in goats were determined at 14-day interval. PPR-specific antibodies reached to peak at 14- and 28-day post vaccination in intraocular vaccinated goats similar to the intranasal immune response. At day 56 following vaccination, intraocular route of PPR vaccine administration provides similar immune response to the subcutaneous and intramuscular routes. Hematological analysis revealed the intraocular vaccinated goats have no significant difference in their erythrocytic values, i.e., RBCs, hemoglobin, and hematocrit, though within the normal ranges following comparison with unvaccinated and vaccinated groups. However, intraocular vaccinated animals showed significant difference (P < 0.05) but within normal range in leukocytic indices, i.e., WBCs, lymphocytes, and neutrophils when compared with subcutaneous vaccinated animals. Moreover, lower neutrophil to lymphocyte ratio (NLR) in vaccinated animals through intraocular route suggests the ability to stimulate the cellular immune response following vaccination. The intraocular route of vaccine administration has been found effective and safe in providing the immunity similar to the other mucosal and subcutaneous administration of vaccines.