Characterization Of Avipoxviruses From Chickens And Domestic Pigeons In Tanzania

ABSTRACT

Avipoxviruses (APVs) are double stranded DNA viruses belonging to the family Poxviridae, sub-family Chordopoxvirinae and genus Avipoxvirus. APVs cause pox in birds; in chickens the disease is known as fowl pox, caused by Fowlpox virus (FWPV). In the recent years the incidence and prevalence of fowl pox in chickens has increased in Tanzania, characterized by high mortalities of chicks and growers. The main research question among researchers has been “are there variant strains of FWPV or other APVs circulating in domestic birds that pose a threat to chickens in Tanzania?’’ The general objective of this study was to investigate the characteristics of APVs from chickens and domestic pigeons in Tanzania, focusing on development of appropriate fowl pox vaccine. The specific objectives were to determine genetic characteristics of APV isolates from chickens and domestic pigeons in Tanzania, to investigate integration of Reticuloendotheliosis virus (REV) genes in the Tanzanian FWPV field isolates and the imported commercial FWPV vaccines currently used in the country, and to evaluate virulence characteristics of Tanzanian strains of FWPV and pigeonpox virus (PGPV) in chickens. Samples of cutaneous nodular lesions were collected from chickens (n = 154) and pigeons (n = 17) suspected to have pox, followed by virus isolation. Genetic characterization involved DNA extraction; polymerase chain reaction (PCR) amplification of FWPV and PGPV P4b gene, REV envelope (env) gene and REV 5' long terminal repeat (LTR); gel electrophoresis of PCR products; purification of PCR products; sequencing of purified PCR products and analysis of the sequence data using standard procedures. Biological characteristics, particularly virulence characteristics of Tanzanian strain(s) of FWPV and PGPV in chickens, were investigated by inoculating 10-day old embryonated