Phylogenetic analysis and genetic characterization of chicken anemia virus isolates from Cambodia

Invasion of Chicken Anemia Virus in Specific-Pathogen-Free Chicken Flocks and Its Successful Elimination from the Colony

A specific-pathogen-free (SPF) chicken colony was maintained with successive groups a month apart in age. The absence of specific pathogens, including chicken anemia virus (CAV), was confirmed through periodic serological tests for each group. However, some groups became CAV seropositive. The procedures of removing seropositive and the adjacent seronegative chickens followed with chemically disinfecting the housing did not halt CAV outbreaks. The full genome sequence of the CAV strain that appeared was closely related to low-virulence isolates in China. The outbreaks of CAV decreased with an increase in the seropositive chicken population, indicating that the progeny is protected from CAV infection by maternal anti-CAV antibodies. The persistence of CAV in erythroid and lymphoid tissues or reproductive tissues from CAV seropositive chickens was examined in chickens of various ages using polymerase chain reaction (PCR). Since a low persistence of CAV was observed in the colony, we isolated eggs from CAV seropositive hens through artificial insemination using semen collected from roosters and confirmed as CAV-free by PCR. Fertilized eggs were transferred to a new SPF facility and used for generating CAV-free progeny. To date, chickens reared in the new facility have been CAV-free for longer than two years. Redirection of eggs from seropositive hens was an effective means of eliminating CAV from chickens.

Genomic Sequence and Pathogenicity of the Chicken Anemia Virus Isolated From Chicken in Yunnan Province, China

Chicken anemia virus (CAV), which has been reported in many countries, causes severe anemia and immunosuppression in chickens. In this study, a CAV strain YN04 belonging to genotype A was first identified from infected chickens in Yunnan province, China. Moreover, the animal infection experiments further confirmed that the strain YN04 is a highly pathogenic strain, which can cause 86.67% mortality in chickens in the infection group. The mean death time of infected chickens was 13.1 days post infection (dpi). CAV infection induced severe anemia with significant decrease in packed cell volume (PCV), and serious atrophy and lesion of thymus and bursa with high viral load at 14 dpi. Besides, CAV infection caused a sharp decrease in chicken body weight and immune organ indices including the ratio of thymus or bursa to body weight at 21 dpi, which displayed the potential immunosuppression state at this stage. These findings enrich the epidemiological data on CAV and may provide information for preventing its further spread in Yunnan province, China.

Whole genome analysis and molecular characterization of chicken infectious anemia virus from an outbreak in a layer flock reveals circulation of genogroup IIIb in South India

The complete genome (2298 nucleotides) of the economically important and immunosuppressive, chicken infectious anemia virus (CAV), from a disease outbreak in a layer flock is discussed. This is the first report of a complete genome sequence of CAV from India. The phylogenetic analyses grouped this isolate with CAV genogroup IIIb based on both complete genome and capsid protein (VP1) sequences. The analyses further revealed the presence of CAV genogroups II, IIIa and IIIb in India. The VP1 sequence identity ranged between 84.4 to 99.3% with that of the Indian isolates and carried a unique substitution at position 447 (serine instead of threonine). Two novel amino acid substitutions were observed at position 52 of VP1 (serine instead of proline) and at position 26 of VP2 (asparagine instead of serine). Sequence analyses of VP1, VP2 and VP3 suggested that the isolate could be attenuated. Comparison with CAV variants, isolated from mammalian species, showed similarities in the numbers of certain transcription factor binding sites in the non-coding regions. Recombination analysis detected no recombination events in this isolate. Further investigations are needed to understand the implications of the unique features of this isolate on viral virulence.

Detection and molecular characterization of chicken infectious anaemia virus in young chicks in Punjab region of north-western India

Chicken infectious anaemia (CIA) is an important viral disease of chicken causing significant immunosuppression and severe anaemia worldwide. Occurrence of severe disease and mortality is noticed in young chicks (2-3 weeks). Vertical mode of transmission increases chance of infection and persistence of virus among the infected flocks. The current study was conducted in Punjab state for confirmation and genetic characterization of CAV among chicken flocks of various poultry farms. DNA was extracted from the tissue samples and subjected to polymerase chain reaction (PCR) of VP1 gene and whole genome. PCR products were further sequenced for confirmation of chicken infectious anaemia virus (CIAV) genome in the clinical samples. PCR amplification of DNA from the tissue samples yielded expected product size of 1350 bases of VP1 gene and 2.3 kb of whole genome. Out of 16 commercial poultry farms, 11 were confirmed with presence of CIAV, and out of 65 birds, 39 were found positive (60%) for CIAV genes. Among the various organs, the presence of viral gene was detected at highest level in thymus when compared with other organs. It is concluded that chicken infectious anaemia virus detected from Punjab state is closely related to other Indian isolates and neighbouring countries which necessitates need of more intensive studies with a greater number of samples for implementing effective control measures.

Chicken infectious anaemia virus infections in chickens in northern Vietnam: epidemiological features and genetic characterization of the causative agent

Since the first report of chicken infectious anaemia virus (CIAV) in Vietnam in 2013, there have not been many studies focused on the detection of CIAV or the molecular characteristics of the virus. This study attempted to investigate the presence of CIAV in northern Vietnam by molecular-based methods. Regarding the spatial distribution of CIAV, the PCR-based results showed that CIAV was detected in 47 out of 64 farms (73.4%) and in all 10 investigated provinces. Of the 119 samples assayed by PCR, 74 (62.2%) tested positive for CIAV DNA. By arranging the samples into different categories, it was found that CIAV was detected at high rates (above 50%) based on all 4 evaluated criteria as follows: production type of chicken, housing system, flock size and age group. Different housing systems were significantly associated with the detection rates of CIAV (P = 0.003). By genetic analyses, all of the Vietnamese CIAVs were found to (i) lack substitutions related to attenuation substitutions, (ii) group separately from vaccine-like CIAVs and (iii) belong to genogroups G2 and G3 of CIAV. Because of the wide distribution of CIAV and because the virus was confirmed not to be vaccine-like viruses, it is suggested that further studies be conducted on the clinical form of chicken infectious anaemia, as well as the immunosuppressive effect of CIAV on chickens in Vietnam.RESEARCH HIGHLIGHTS Wide distribution of chicken infectious anaemia virus (CIAV) in northern Vietnam.Vietnamese CIAVs belong to genogroups G2 and G3 of CIAV.

Development of a loop-mediated isothermal amplification assay for the detection of chicken anemia virus

Chicken anemia virus (CAV) infection has been reported in various poultry industries worldwide. Since CAV infection is becoming increasingly prevalent, especially in local chickens of China, rapid CAV detection has become essential. The conventional diagnostic methods are time consuming and need special expertise. Therefore, in this study, we developed a specific and sensitive loop-mediated isothermal amplification (LAMP) assay for CAV detection by using multiple sequence alignment of VP2. This assay was performed at 61°C for 1 h, and there was no non-specific reaction to common avian disease viruses. The detection limit was 65 copies of viral DNA; thus, this assay showed similar sensitivity to quantitative polymerase chain reaction (qPCR) but it was more sensitive than conventional PCR. Moreover, this assay was performed using clinical samples. The LAMP assay results were 83.6% correlated to the PCR results of the clinical samples, indicating that this method is an effective tool for the rapid detection of CAV.

Full genome sequences of chicken anemia virus demonstrate mutations associated with pathogenicity in two different field isolates in Egypt

Chicken anemia virus (CAV) is an important pathogen associated with immunosuppression in chicken. In this study, out of samples collected from 115 commercial poultry farms, 12 samples were CAV positive by PCR. Partial sequence and phylogenetic analysis of VP1 gene revealed that the detected viruses were clustered to genotype I (n = 3) and genotype II (n = 9). Motifs of both low (E144) and high pathogenic strains (T89, I125, Q141) were found in the three viruses of genotype I. Whereas genotype II viruses demonstrated the characteristic motifs of highly pathogenic strains (I75, T89, I125, Q141, and Q144). Three isolates representative of both genotypes (CAV/CA1, CAV/GZ1 and CAV/SK4) were selected for full genome sequencing and results revealed that the VP2 gene had two substitutions at V153 and E 175, while VP3 gene had only one substitution at C118. To evaluate virus pathogenicity, two isolates from each genotype (CAV/SK4 of genotype I and CAV/CA1 of genotype II) were intramuscularly inoculated in two groups of one-day-old specific pathogen free chicks. Eighteen days post inoculation, PCR detected CAV in 75 and 90% of chicks in group I and II; respectively. Mortalities in inoculated chicks were 5 and 20% and packed cell volume values were 0.21 and 0.19; respectively. CAV/CA1 and CAV/SK4 isolates showed pathogenic evidences at the level of genetic (Q141 and 394Q) with variable degree of virulence. In conclusion, the study reports the circulation of at least two genotypes of CAV among chicken population with mutation associated with pathogenicity.