Epidemiology and molecular characterization of chicken anaemia virus from commercial and native chickens in Taiwan

Abstract

Chicken infectious anaemia (CIA) is a disease with a highly economic impact in the poultry industry. The infected chickens are characterized by aplastic anaemia and extreme immunosuppression, followed by the increased susceptibility to secondary infectious pathogens and suboptimal immune responses for vaccination. Commercially available CIA vaccines are routinely used in the breeders in Taiwan to protect their progeny with maternal-derived antibodies. However, CIA cases still occur in the field and little is known about the genetic characteristics of Taiwanese chicken anaemia viruses (CAVs). In this study, CAV DNA was detected in 72 of 137 flocks collected during 2010-2015. Among the PCR-positive samples, the coding regions of 51 CAVs were sequenced. Phylogenetic analysis of the VP1 gene revealed that, although most of Taiwanese CAVs belonged to genotypes II and III, some isolates were clustered into a novel genotype (genotype IV). Moreover, a Taiwanese isolate in this novel genotype IV appeared to be derived from a recombination event between genotypes II and III viruses. Five Taiwanese CAV isolates were highly similar to the vaccine strains, 26P4 or Del-Ros. Taken together, these results indicate that the sequences of CAVs in Taiwan are variable, and inter-genotypic recombination had occurred between viruses of different genotypes. Moreover, vaccine-like strains might induce clinical signs of CIA in chickens. Our findings could be useful for understanding the evolution of CAVs and development of a better control strategy for CIA.

Genetic Heterogeneity among Chicken Infectious Anemia Viruses Detected in Italian Fowl

“…In order to verify the division into these genogroups, a phylogenetic analysis including the 11 complete VP1 sequences obtained and the reference sequences available on GenBank was performed and confirmed the Italian strains classification with bootstrap values > 70 (Figure 3). CIAV strains are classified into genogroups I, II, IIIa and IIIb [18] and IV [19], and the Italian strains analyzed in the present study belonged to genogroups II (n.10 strains), IIIa (n.11 strains) or IIIb (n.4 strains). Noticeably, the CIAV/IT/CK/1153-1/19 strain clustered with the vaccine strain 26P4, and strains CIAV/IT/CK/1155/19, CIAV/IT/CK/1180/19 and CIAV/IT/CK/1195/19 with the Del-Ros vaccine strain, both in genogroup IIIb.…”

“…The patterns of amino acid substitutions in specific amino acid sites, located at positions 22, 75, 97, 125, 139, 144, 157, 287, 290, 370, 394 and 413 of the VP1 protein, are reported in Table 4. These amino acids showed variability among CIAV isolates [19,21,35,41], and changes in some of them are associated with viral attenuation [11][12][13][42][43][44]. The full genome sequencing allowed us to analyze VP2 and VP3 genetic variability among the detected strains, and in comparison with other strain sequences retrieved from GenBank.…”

“…Thus, for the genetic characterization of CIAV strains, the VP1 gene is primarily used [17]. Phylogenetically, based on the nucleotide sequence of the VP1 gene, four distinct genogroups/genotypes (I, II, III and IV) have been identified [18,19] and reported worldwide. Moreover, in the VP1 protein, there are vaccine genetic markers that allow the differentiation of the same from field strains [20].…”

Persistent Infection with Chicken Anemia Virus in 3-Week-Old Chickens Induced by Inoculation of the Virus by the Natural Route

“…Maternal immunity usually disappears by approximately 3 weeks of age. A high prevalence of CIA was detected in older chickens of layer and broiler breeds in Taiwan [7]. The detected cases were naturally occurring horizontal infections with CAV, which most likely occurred by exposure to CAV in the environment.…”

Oral Inoculation of Specific-Pathogen-Free Chickens with Chicken Anemia Virus Induces Dose-Dependent Viremia and Transient Anemia

“…McNulty et al [5] demonstrated that the minimum dose of CAV that caused anemia in a high proportion of 1-day-old inoculated chickens was above 10 3 .3 50% tissue culture infectious dose (TCID 50 ). In Taiwan, most field CAV cases were detected in older chickens with transient poor performance [6]. Dren et al [7] examined the pathogenesis of CAV infection in 6-week-old chickens with different inoculation doses.…”