ABSTRACT
Newcastle disease (ND) is an OIE listed disease caused by virulent avian paramyxovirus type 1 (APMV-1) strains, which affect many species of birds and may cause severe economic losses in the poultry sector. The disease has been officially and unofficially reported in many African countries and still remains the main poultry disease in commercial and rural chickens of Africa. Unfortunately, virological and epidemiological information concerning ND strains circulating in the Western and Central regions of Africa is extremely scarce. In the present study, sequence analysis, pathotyping and detailed genetic characterization of virulent ND strains detected in rural poultry in West and Central Africa revealed the circulation of a new genetic lineage, distinguishable from the lineages described in the Eastern and Southern parts of the continent. Several mismatches were observed in the segment of the matrix gene targeted by the primers and probe designed for the molecular detection of APMV-1, which were responsible for the false negative results in the diagnostic test conducted. Furthermore, deduced amino acid sequences of the two major antigens eliciting a protective immune response (F and HN glycoprotein) revealed protein similarities <90% if compared to some common vaccine strains. Distinct mutations located in the neutralizing epitopes were revealed, indicating the need for detailed assessment of the efficacy of the current vaccines and vaccination practices in Africa. The present investigation provides important information on the epidemiology, diagnosis and control of NDV in Africa and highlights the importance of supporting surveillance in developing countries for transboundary animal diseases.
Subject(s)
Newcastle Disease , Newcastle disease virus/genetics , Poultry Diseases , Viral Envelope Proteins/genetics , Africa, Central , Africa, Western , Amino Acid Sequence , Animals , Base Sequence , Chickens , Developing Countries , Genetic Variation , HN Protein/chemistry , HN Protein/genetics , Molecular Sequence Data , Newcastle Disease/diagnosis , Newcastle Disease/prevention & control , Newcastle Disease/virology , Newcastle disease virus/classification , Newcastle disease virus/immunology , Newcastle disease virus/pathogenicity , Phylogeny , Poultry Diseases/diagnosis , Poultry Diseases/prevention & control , Poultry Diseases/virology , Sequence Alignment , Viral Envelope Proteins/chemistry , Viral Fusion Proteins/chemistry , Viral Fusion Proteins/genetics , Viral Matrix Proteins/chemistry , Viral Matrix Proteins/geneticsABSTRACT
One of the objectives of the Pan African Programme for the Control of Epizootics (PACE) was to set up epidemiological surveillance networks in African countries. A survey based on a written questionnaire was conducted to review the technical and institutional organisation of epidemiological surveillance networks in nine French-speaking countries, including five in West Africa (Senegal, Burkina Faso, Côte d'lvoire, Togo and Guinea) and four in Central Africa (Cameroon, Central African Republic, Democratic Republic of Congo and Chad). The survey results showed that there are more similarities than differences among epidemiological surveillance networks. In general, they were found to be technically and institutionally well established. However, the two weaknesses of the majority of networks are the inadequate diagnostic capacity of laboratories and the insufficient operationality of steering committees. Epidemiological surveillance should exclusively be the domain of Veterinary Services and it is crucial for ensuring that any change in the health status of an animal population is detected rapidly. However, the networks' continuing survival after external financing ceases is generally not guaranteed because, in many cases, governments fail to fund them adequately.
