الفهرس 
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Abstract
Twenty random field isolates 0±’ 1ewcast1e disease
virus (NDV), recovered during 1977—to 1980 from six avian
species, were examined along wit.h four currently used
vaccine strains by various tests for in vitro and in vivo
strain m.arkers. The results achieved showed that:
le The isolates differed considerably in their ability
to agglutinate various avian and mnmalian eyt1irocytes,
and were distinguishable from the vaccine strains by their
inability to agglutinate cow erythrocytes.
2. The haemagglutination—elution patterns varied with
the virus strain and type of erythrocytes. With chicken
RBC, 18 so1ates as well as the vaccine straine Bl, F and
Komarov were rapid eluter, whereas 2 isolates and the LaSota
vaccine strain were intermediate. with chicken nb’o ±J3C,
all intrediate eluter became slow eluter and two rapid
eluter became 1ow and intezmediate eluter.
3. ..1l isolates, except three from chickens, were thernio— staWe at 56 0 for longer than 60 minutes. he three isolates from chickens, like the vaccine stains, were thermolabi].e.
Virus infectivity was lost simultanously with the haanglu—
tinin, or more frequently some time ea’].ier. 4