Prevalence of antibodies against chicken anaemia virus (CAV) in broiler breeders in Southern Brazil

Abstract

Chicks infected during the first two weeks of life with chicken anaemia virus (CAV) manifest clinical disease that can be avoided if the breeder hens transfer enough antibodies to their progeny. The objective of the present work was to establish the prevalence and titer of anti-CAV antibodies in some Brazilian broiler hen breeder flocks and verify in which phase of life the birds were infected. A total of 1,709 serum samples from 12 broiler hen flocks vaccinated against CAV and 64 unvaccinated flocks were analyzed for CAV antibodies with an enzyme-linked immunosorbent assay (ELISA). All non-vaccinated breeder flocks were found to be infected with CAV, with 89% of the hens tested presenting antibodies, 52% of these with titers considered high enough to protect their progeny against CAV infection. Likewise, all vaccinated hens had antibody titer to CAV capable of conferring protection to their progeny. Thus, vaccination of hens seems capable of conferring protection to chicks against clinically apparent CAV-associated disease.

Comparison of CAV antibody titers in a vaccinated and naturally infected broiler breeder flocks

“…In this study, we could not find any anti-CAV negative-antibody breeder flocks, so we did the trial of efficacy of live Nobilis CAV P4 vaccine in positive-antibody breeder flocks. Besides of comparison of mean titer (AMT) and CV% s in vaccinated and naturally infected groups and their progenies, we followed up the number of titers above 5000 with this kind of Elisa kit based on studies by Canal et al (2004) who showed that the relationship of VN Elisa titer and reported that Elisa titer above 5000 in breeder by Elisa kit (Synbiotic Corporation, USA) can protect progeny against CIA in their life. They showed that in Brazil, in vaccinated breeder flocks 99% of hens had antibody titer > 5000 and 1% had titer 4000-5000, in contrast with unvaccinated breeder flocks that 52% had titer > 5000 and 47% had titer < 5000.…”

“…They showed that in Brazil, in vaccinated breeder flocks 99% of hens had antibody titer > 5000 and 1% had titer 4000-5000, in contrast with unvaccinated breeder flocks that 52% had titer > 5000 and 47% had titer < 5000. Different studies show that vaccination can induce higher, more durable and more homogenous titer compared natural challenge in breeder flock which consequently results in safer immunity in progeny (Canal et al, 2004;Roussan, 2006). Progeny of vaccinated hens have sufficient levels of maternally-derived antibody to CAV for up to 3 to 4 weeks of age and after challenge haematocrit levels and weights of thymus in vaccinates remained within normal ranges whereas chicks from CAV non-vaccinated hens developed anemia and thymus atrophy following challenge (Otaki et al, 1992 andPages-Mante et al, 1997).…”

“…According to the kit's instruction, the serum samples with the S/P ratio equal or less than 0.349 were considered zero titer and S/P ratio equal or greater than 0.350 (titer equal or greater than 1472) were considered positive serum. Also, the titers above 5000 was compared between two flocks because it considered being protective against CIAV in their progenies based on previous studies (Canal et al, 2004;Roussan, 2006).…”

“…This field trial study was carried out to evaluate the efficacy of live CIAV vaccine in induction of immunity against the disease in broiler breeder flock compared with naturally infected flock and following up the titer transferred to their progenies. Also, we calculated and compared the numbers of sera with titer above 5000 in Elisa kit (Synbiotic Corporation, USA) in test and control groups based on the hypothesis of Canal et al who reported the relationship of VN titer and ELISA titer using the Synbiotic Elisa kit and found that Elisa titer above 5000 in breeders can protect their progenies against CIA in their first 4 week-old of age (Canal et al, 2004;Roussan, 2006).…”

Occurrence of chicken anemia virus in backyard chickens of the metropolitan region of Belo Horizonte, Minas Gerais

“…Epidemiological studies carried out in Brazil indicated 92% (Brentano et al, 2000), 100% (Canal et al, 2004) or 97.2% (Gomes et al, 2005) CAV-specific antibody prevalence in broiler breeders after 17 weeks of age. As to free-range or backyard chickens, there is little information.…”