Tracing the antibody mediated acquired immunity by Foot and Mouth disease and Rift Valley Fever combined vaccine in pregnant ewes and their lambs

Research (Published online: 07-11-2014)

4. Tracing the antibody mediated acquired immunity by Foot and Mouth disease and Rift Valley Fever combined vaccine in pregnant ewes and their lambs - Wael Mossad Gamal, Eman Mahmoud Mohamed Soliman and Mona Ali El-Manzalawy

Veterinary World, 7(10): 922-928

   doi: 10.14202/vetworld.2014.922-928

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Abstract

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Aim: The aim of this study was to provide adequate protection to ewes and their lambs against Foot and Mouth disease (FMD) and Rift Valley Fever (RVF).

Materials and Methods: A combined inactivated oil vaccine was prepared successfully. Such vaccine was found to be free from foreign contaminants, safe and potent as determined by quality control tests such as challenge protection percentage for FMD and mice ED50 for RVF. Vaccination of pregnant ewes with the prepared combined vaccine and determination of the antibody level via serum neutralization test (SNT) and Enzyme Linked immune sorbent assay (ELISA) in the vaccinated pregnant ewes and their lambs.

Results: Vaccination of pregnant ewes revealed that these ewes exhibited high levels of specific antibodies against the included vaccine antigens (Foot and Mouth disease virus type A Iran O5, O PanAsia and SAT2/EGY/2012 and RVFV-ZH501). FMD antibodies recorded their peaks by the 10th week while those of RVF recorded their peaks by the 12th week post vaccination then all antibodies began to decrease gradually to reach their lowest protective titers for FMD by the 32nd week post vaccination and those for RVF by the 34th week post vaccination. Potency test of the prepared combined vaccine expressed as protection percentage of vaccinated sheep against target virulent FMD virus serotypes reflected a protection percentage of 80% against type O and SAT2 and 100% against A while for RVF, the mice ED50 was found to be 0.009 indicating the potency of the prepared vaccine. The antibody titer in serum and colostrum of vaccinated pregnant ewes at day of parturition (10-12 week post vaccination) recorded a high titer against FMD serotype (O), serotype (A), serotype (SAT2) and against RVF. It was noticed that the colostrum antibody titers were slightly higher than those in the sera of vaccinated ewes at time of parturition. The newly born lambs from vaccinated ewes, exhibited good levels of maternal immunity against the included antigens through suckling their mother colostrum by the 24 hrs. post parturition. The newly born lambs recorded their highest level by 1 week of birth and lasted within a protective level up to 11-12 week of birth.

Conclusion: Using of FMD/RVF combined vaccine provided a sufficient immune status for pregnant ewes as well as for their lambs. Vaccination of newly born lambs should be carried out by the 4th month of birth.

Keywords: FMD, RVF, combined vaccine, pregnant ewes, new born lambs, SNT, ELISA.