RESUMO
In 1989, 220 Holstein Friesian cattle (212 heifers and eight bulls) were imported from Minnesota, USA, to form a closed dairy herd in Arab El-Aoumar, Assiut, Upper Egypt. In November 1996, some abnormal signs such as loss of weight, decreased milk yield, external lymphadenopathy and decreased appetite were observed on this farm. Serological screening by enzyme-linked immunosorbent assay revealed a seroprevalence of antibodies directed against bovine leukaemia virus (BLV) of 37.7% in cattle under 2 years old and of 72.8% in animals more than 2 years old. Diagnosis was confirmed by the detection of BLV proviral DNA using polymerase chain reaction with primers amplifying a fragment of the env gene. Out of 21 tested leucocyte fractions from individual animals, 15 were positive showing a BLV-specific amplicon of 444 base pairs. Analysis of the amplicons for restriction fragment length polymorphisms and DNA sequencing results allowed the isolates to be typed. Since this was the first recorded case of enzootic bovine leukosis in Upper Egypt, strict quarantine measures were adopted and all serologically positive animals in the herd were culled.
Assuntos
Surtos de Doenças/veterinária , Leucose Enzoótica Bovina/epidemiologia , Vírus da Leucemia Bovina/genética , Animais , Anticorpos Antivirais/sangue , Sequência de Bases , Bovinos , DNA Viral/sangue , Egito/epidemiologia , Leucose Enzoótica Bovina/patologia , Leucose Enzoótica Bovina/prevenção & controle , Ensaio de Imunoadsorção Enzimática/veterinária , Feminino , Vírus da Leucemia Bovina/imunologia , Masculino , Dados de Sequência Molecular , Reação em Cadeia da Polimerase/veterinária , Polimorfismo de Fragmento de Restrição , Quarentena/veterinária , Estudos SoroepidemiológicosRESUMO
Pasteurella multocida infection in embryonated chicken eggs was studied by chorio-allantoic membrane inoculation. Strain differences were demonstrated in terms of lesion severity and time to death, especially during the first 24 h post-inoculation. A strain of low virulence gave a clear dose response but more virulent strains did not. Comparable results were obtained by infecting 6-week-old chickens. The main lesions in inoculated embryos appeared as severe vascular involvement of the entire embryo and feather tracts, thickening of the chorio-allantoic membrane, and enlargement and congestion of the yolk sac. The bacteria were demonstrated by transmission electron microscopy, either extracellularly or multiplying intracellularly in hepatocytes, heart tissue, and in the hyperplastic layer of the chorio-allantoic membrane, with resulting damage to the cellular organelles, and severe tissue changes.
