ABSTRACT
A Variable Number Tandem Repeat (VNTR) analysis was conducted on thirteen (13) M. mycoides mycoides Small Colony isolates from Nigeria using Tandem Repeat (TR) 34 which is a predicted lipoprotein located within the hypothetical protein MAG6170. The analysis revealed diversity within the M. mycoides mycoides Small Colony isolates with five different VNTR types indicated. Some correlation was determined between the VNTR types and their geographical origin. VNTR analysis may represent a useful, rapid first-line test for use in molecular epidemiological analysis of M. mycoides mycoides Small Colony for possible outbreak tracing and disease control.
Subject(s)
Genetic Variation , Minisatellite Repeats , Mycoplasma mycoides/genetics , Animals , Mycoplasma mycoides/isolation & purification , NigeriaABSTRACT
Contagious bovine pleuropneumonia (CBPP), caused by Mycoplasma mycoides subsp. mycoides SC (MmmSC), is one of the most significant cattle disease in Africa. The control measures, which led to eradication from numerous countries are not feasible in Africa where the only prophylaxis relies on vaccination. However, the attenuated vaccines, used up to now in Africa, are of low efficiency. The development of an improved vaccine is, therefore, a necessity. The purpose of this study was to compare some immunological parameters in MmmSC-infected cattle (endobronchial versus natural in-contact infection) and assess the response in correlation with the clinical outcome (death versus recovery). Characterization of the immune parameters elicited in recovered animals, known to be refractory to new infection, will be an important step towards development of new vaccines against CBPP. A significant outcome of this study was the demonstration that all MmmSC-infected cattle developed a MmmSC-specific cell-mediated immune response. A kinetic analysis of the MmmSC responsiveness showed that the main difference between endobronchially- and in-contact infected animals was the delay before the onset of the MmmSC-specific immune response. The first MmmSC-responding PBMC sample was selected from each animal for cell phenotyping. The phenotypic analysis of this early MmmSC-induced response revealed the predominant contribution of the CD4 T-cells in all animals whereas IFNgamma was only constantly produced in recovered animals. Evolution of this early MmmSC-specific immune response was then followed by a kinetic analysis of the MmmSC-induced CD4 T-cell response and IFNgamma released. The results demonstrated that in recovered animals, the MmmSC-specific CD4 Th1-like T-cell response was maintained until slaughtering whereas in animals with acute disease, progression of CBPP was associated with a decreased ability of the PBMC to produce IFNgamma. The results led to the identification of immune parameters, which correlate with protection against CBPP and to a relevant strategy for the development of improved vaccines against this disease.
Subject(s)
CD4-Positive T-Lymphocytes/immunology , Cattle Diseases/immunology , Interferon-gamma/biosynthesis , Mycoplasma mycoides/immunology , Pleuropneumonia, Contagious/immunology , Animals , Bacterial Vaccines/pharmacology , Cattle , Cattle Diseases/prevention & control , Immunophenotyping , In Vitro Techniques , Kinetics , Lymphocyte Activation , Mycoplasma mycoides/pathogenicity , Pleuropneumonia, Contagious/prevention & controlABSTRACT
Contagious bovine pleuropneumonia is a major threat for cattle in Africa. Since 1956 the T1/44 strain has been used as a vaccine, and later on, T1sr, a streptomycin-resistant variant that gives fewer post-vaccinal reactions had been developed. These vaccines are known not to be very efficient but they normally should provide protection for about eight months. However, recent emergency vaccinations, performed in various countries in the southern part of the continent apparently met with failure, casting doubts on the identity as well as the protection afforded by the T1sr strain. A vaccine trial has been designed to reassess the real protection afforded by these vaccines in face of recently isolated pathogenic strains. Great care has been taken to test the original vaccinal strains at a dose corresponding to the minimum requirement by international standards. The test was performed in Cameroon, Kenya, and Namibia as to take into account the genetic diversity that exists among the pathogenic strains. In those conditions, the protection rate at three months varied from 33 to 67%, whatever the strain used, T1/44 or T1sr. These results call for additional research for vaccine development and careful planning of strategies in the fight against CBPP.
Subject(s)
Bacterial Vaccines , Pleuropneumonia, Contagious/prevention & control , Vaccination/veterinary , Africa , Animals , Cameroon , Cattle , Kenya , Lung/pathology , Pleuropneumonia, Contagious/pathology , Pleuropneumonia, Contagious/transmissionABSTRACT
Four herds of zebus from northern Cameroon totalling 136 animals were vaccinated subcutaneously with the following doses of Brucella abortus strain 19: 5 x 10(9) colony-forming units (CFU), 10(9) CFU, 5 x 10(8) CFU and 10(7) CFU. Twenty-eight days after vaccination, the following seroconversion rates were observed respectively: 97.4, 96.2 84.2 and 73.3%. Of the 52 animals which could be tested subsequently including 39 over one year old on the vaccination day, only one showed antibodies 6 months after vaccination. The cost price of the strain 19 vaccine produced at the Boklé National Veterinary Laboratory was estimated to be 65 F CFA at the 10(9) CFU dose and 1,740 F CFA at the 5 x 10(10) CFU dose usually recommended. The use of the Buck 19 strain in the medical prophylaxis of bovine brucellosis in northern Cameroon is discussed.
