Characterization of Israeli avian metapneumovirus strains in turkeys and chickens.

Although the disease associated with the avian metapneumovirus (aMPV) has been described in Israel for more than 20 years and one Israeli isolate was characterized as subtype A, this is the first study investigating the strains circulating in Israel (period 2002 to 2004). Viral RNA was detected by reverse transcription-polymerase chain reaction in 44% of the examined flocks, and one-half of the virus isolation attempts were successful. Characterization showed that 34 non-vaccinated turkey flocks had aMPV subtype B, three had aMPV subtype A and three remained undetermined. Sequence analysis of part of the attachment protein G gene (1161 base pairs) showed a relative homogeneity within the Israeli subtype B group, although they were different from the European and vaccine strains. Seven out of 10 vaccinated flocks were reverse transcription-polymerase chain reaction-positive for aMPV, and sequence analysis of 239 base pairs of the G gene revealed that field strains and not vaccine strains were recovered from these flocks. Overall, the virological examination confirmed the high prevalence of aMPV in Israel and revealed a co-circulation of two subtypes, A and 13, with aMPV subtype B being the dominant subtype.