RESUMO
The use of effective vaccines is among the most important strategies for the prevention and progressive control of transboundary infectious animal diseases. However, the use of vaccine is often impeded by the cost, a lack of cold chains and other factors. In resource-limited countries in Africa, one approach to improve coverage and reduce cost is to vaccinate against multiple diseases using combined vaccines. Therefore, the objective of this study was to evaluate a combined vaccine for the prevention and control of Lumpy Skin Disease (LSD), Contagious Bovine Pleuropneumonia (CBPP) and Rift Valley fever (RVF). The LSD and CBPP were formulated as a combined vaccine, and the RVF was formulated separately as live attenuated vaccines. These consisted of a Mycoplasma MmmSC T1/44 strain that was propagated in Hayflick-modified medium, RVF virus vaccine, C13T strain prepared in African green monkey cells (Vero), and the LSDV Neethling vaccine strain prepared in primary testis cells. The vaccines were tested for safety via the subcutaneous route in both young calves and pregnant heifers with no side effect, abortion or teratogenicity. The vaccination of calves induced seroconversions for all three vaccines starting from day 7 post-vaccination (PV), with rates of 50% for LSD, 70% for CBPP and 100% for RVF, or rates similar to those obtained with monovalent vaccines. The challenge of cattle vaccinated with the LSD/CBPP and the RVF vaccine afforded full protection against virulent strains of LSDV and RVFV. A satisfactory level of protection against a CBPP challenge was observed, with 50% of protection at 6 months and 81% at 13 months PV. A mass vaccination trial was performed in four regions of Burkina Faso that confirmed safety and specific antibody responses induced by the vaccines. The multivalent LSD/CBPP+RVF vaccine provides a novel and beneficial approach to the control of the three diseases through one intervention and, therefore, reduces the cost and improves vaccination coverage.
RESUMO
Newcastle disease (ND) is a big concern throughout the world because of the devastating losses that can occur with commercial and backyard poultry. The major problem in many countries is the loss of the vaccine's effectiveness due to inadequate use or storage conditions, particularly in hot climates. In the present study, stability of the five, most-used NDV vaccine strains (I-2, LaSota, B1, Clone 30 [C30], and VG-GA) was tested comparatively at different storage temperatures (4 and 37 C for the freeze-dried form and 4, 24, 37, and 45 C for the freeze-dried vaccine reconstituted in diluents). The vaccine stability was evaluated by the cumulative infectious titer drop and the theoretical shelf life at particular temperatures. Results showed that I-2 and LaSota are the most stable vaccine strains compared to B1, C30, and VG-GA; they registered the lowest titer drops and the longest shelf life whether at cool, high, or room temperatures and for both freeze-dried and reconstituted vaccines.
