Three-week-old specific-pathogen-free chickens were vaccinated with either a commercial modified live virus fowl pox vaccine or five "variant" poxvirus field isolates. Immunity engendered by the commercial modified vaccine or field isolates was challenged with either the variant isolates or commercial modified vaccine virus. The commercial modified vaccine did not adequately protect vaccinates against challenge with the variant isolates. The percentages of vaccinated chickens protected following challenge with each of the variant isolates were 70%, 20%, 30%, 20%, and 25%. However, when the isolates were applied as vaccines, 100% of the vaccinates were protected against challenge from the modified vaccine virus. Furthermore, the variant poxvirus isolates offered excellent protection from challenge with homologous variant isolates. The modified live virus vaccine was expected to offer significant protection against challenge from the variant pox isolates, but in this experiment it did not. The variant isolates tested may be good vaccine candidates to prevent the vaccine breaks currently encountered in previously pox-vaccinated flocks.
1977, 1979 and 1983. It was observed that the lag period, from 1977 to 1983, when MD incidence remained low reflected the effect of the widespread application of MD vaccines in the advanced poultry producing countries which supplied the bulk of the Nigerian poultry. The importance of diagnostic surveillance of MD is discussed.
Dual infection with fowl pox (FP) and infectious laryngotracheitis (ILT) was diagnosed as the cause of acute mortality in a flock of three age groups of Hy-Line leghorn layers. The affected chickens had not been previously vaccinated against either FP or ILT. The diagnosis was confirmed by virus isolation, histopathology, and the use of specific pox and ILT genomic DNA probes in a dot-blot hybridization assay. FP and ILT vaccinations were recommended to control mortality. The use of FP- and ILT-specific DNA dot-blot hybridization may be used as a routine diagnostic tool to differentiate between the two diseases, especially in atypical cases of either infection or to confirm the existence of the two diseases as a mixed infection in a flock of chickens.
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