Unsatisfactory Sensitivity and Specificity of Indirect Immunofluorescence Tests for the Presence or Absence of Antibodies to Chicken Anaemia Agent (CAA) in Sera of SPF and Broiler Breeder Chickens*

Abstract

A total of 639 flock serum samples, consisting of 10 up to 24 individual chicken sera each, from specific pathogen-free (SPF) flocks and from field flocks were examined by indirect fluorescent antibody (FA) tests for the presence or absence of antibodies to chicken anaemia agent (CAA). Comparisons between results of FA tests and serum neutralization (SN) tests included 284 flock samples where individual sera from a flock were pooled to perform SN tests.The SN test for detection of anti-CAA antibody proved to be about 20 % more sensitive than the indirect FA test. Results of SN tests were considered to be always specific, partly confirmed by CAA challenge of day-old chicks from serologically tested flocks. However, the evaluation of results revealed that the indirect FA test was not sufficiently specific. The major problem with SPF flock samples was false positive results (24/43 = 55.8%) of FA tests, and false negative results (7/32 = 21.9 YO) with field flock samples. The causes of non-specific immunofluorescent reactions resembling CAA-specific fluorescence could not yet be elucidated.

A micro‐scale serum neutralisation test for the detection and titration of antibodies to chicken anaemia agent ‐ prevalence of antibodies in Danish chickens

“…In 1-day-old chickens produced by seropositive parents, the titres were 4.9 to 5.8 (logio) per ml, which is the same level as in the parent stock. Bülow (1988) reported occasionally toxic effect of chicken sera diluted 1:20, but such effect was not observed in any of the sera tested in the present study. The overall percentages of positive flocks of Danish chickens and individual sera from these indicate a considerable high incidence of CAA infection at all levels and in all categories of commercial Danish chicken population investigated.…”

“…The UFA was developed by Yuasa et al (1985) and Bülow et al (1985). Bülow (1988) reported insufficient sensitivity and specificity of the UFA compared with NT. However McNulty et al (1989) obtained similar results with the two methods.…”

Chicken anaemia virus antibody ELISA: Problems with non‐specific reactions

“…The need for an accurate, sensitive serological test for CAV antibodies has been identified and problems which attend the IFA and SN tests noted (von Bülow, 1988;McNulty, 1991). The IFA test suffers from non-specific reactions and some lack of sensitivity.…”

Pathogenicity of chicken anaemia virus (isolate 10343) for young and older chickens

“…According to Bülow (1988) this test is not sensitive enough to assure absolutely the absence or presence of antibodies to CAV. It is therefore possible that the disease shown by this group could have been masked by non-detected antibodies.…”