Chicken anaemia agent in South Africa

Novel Gyroviruses, including Chicken Anaemia Virus, in Clinical and Chicken Samples from South Africa

Introduction. Chicken anaemia virus, CAV, was until recently the only member of the Gyrovirus genus. 6 novel gyroviruses, AGV2, HGyV1, and GyV3-6, have since been discovered in human and chicken samples. Methods. PCR amplification of the VP2 gene was used to detect AGV2/HGyV1, GyV3, and CAV in a range of clinical samples including stool, respiratory, CSF, and HIV-positive plasma. Screening of fresh local chicken meat was also performed. Results. AGV2/HGyV1 or GyV3 was detected in stools from healthy children (17/49, 34.7%) and patients with diarrhoea (22/149, 14.8%). 1.2% (3/246) nasopharyngeal respiratory samples were positive. No AGV2/HGyV1 or GyV3 was detected in nasal swabs from wheezing patients, in CSF from patients with meningitis, and in HIVpositive plasma. CAV was found in 51% (25/49) of stools from healthy children and 16% (24/149) in diarrhoea samples. Screening of 28 chicken samples showed a higher prevalence of gyrovirus (20/28, 71%) compared to CAV (1/28, 3.6%). Phylogenetic analysis of the CAV VP1 gene showed South African sequences clustering with Brazilian isolates from genotypes D2 and A2. Conclusion. Novel gyroviruses, including CAV, are present in the South African population with diarrhoea and respiratory illness as well as in healthy children. Their presence suggests an origin from chicken meat consumption.

Epidemiology of chicken anemia virus in Central African Republic and Cameroon

Background

Although chicken anemia virus (CAV) has been detected on all continents, little is known about this virus in sub-Saharan Africa. This study aimed to detect and characterize CAV for the first time in Central African Republic and in Cameroon.

Results

An overall flock seroprevalence of 36.7% was found in Central African Republic during the 2008–2010 period. Virus prevalences were 34.2% (2008), 14.3% (2009) and 10.4% (2010) in Central African Republic and 39% (2007) and 34.9% (2009) in Cameroon. CAV DNA was found in cloacal swabs of 76.9% of seropositive chickens, suggesting that these animals excreted the virus despite antibodies. On the basis of VP1 sequences, most of the strains in Central African Republic and Cameroon belonged to 9 distinct phylogenetic clusters at the nucleotide level and were not intermixed with strains from other continent. Several cases of mixed infections in flocks and individual chickens were identified.

Conclusions

Our results suggest multiple introductions of CAV in each country that later spread and diverged locally. Mixed genotype infections together with the observation of CAV DNA in cloacal samples despite antibodies suggest a suboptimal protection by antibodies or virus persistence.

Isolation and Preliminary Characterization of Chicken Anemia Virus from Chickens in Nigeria

Chicken anemia virus (CAV) was isolated for the first time from the Nigerian chicken population. The virus was recovered from necropsied birds from broiler and pullet flocks that suffered disease outbreaks tentatively diagnosed as infectious bursal disease. A sensitive polymerase chain reaction (PCR) assay detected CAV DNA in tissues of necropsied birds. Restriction endonuclease analysis performed with the 733-bp PCR product and the Cfo I enzyme indicated at least two different CAVs were circulating among the Nigerian chicken population. Four isolates were obtained from pooled liver and thymus tissues using the MDCC-MSB1 cell line. These isolates were found to be antigenically closely related to the Cuxhaven-1 (Cux-1) reference strain of CAV when reacted with four monoclonal antibodies prepared against the Cux-1 virus. One of the isolates (isolate A) induced thymus atrophy, bone marrow aplasia, and low hematocrit values when inoculated into 1-day-old specific-pathogen-free chickens. These findings not only demonstrate that CAV is present in Nigeria, but they also likely represent the first cell culture isolation of the virus in Africa.

Molecular epidemiology of chicken anemia virus in Nigeria

Between February 2002 and May 2004, chicken anemia virus (CAV) was detected by PCR in organ samples from 14 flocks of poultry farms in Lagos, Ogun and Oyo States in Southwestern Nigeria. The farms reported low (<5%) to high mortalities (up to 100%) with various lesions at necropsy. The complete VP1 gene of 30 of these positive strains was sequenced. Strains that diverged by up to 4.4% on a nucleotide level differed only by up to 2.5% at the amino acid level (7 aa) as a result of clustered silent mutations. No amino acid substitutions specific for Nigerian strains were observed. Some birds had a CAV mixed infection. Genetic clustering of the VP1 gene did not correlate with differences in flock mortality but the co-infection of CAV with IBDV may be particularly lethal. This first molecular epidemiological study of CAV in Africa shows that the Nigerian strains cluster with viruses from very diverse geographic origins and were almost as diverse (4.4%) as all other strains combined (5.8%).

Serologic evidence of chicken infectious anemia in commercial chicken flocks in southwest Nigeria

Sera samples from seven poultry farms in southwest Nigeria consisting of 7 broiler, 10 pullet, 1 layer, 1 cockerel, and 1 broiler breeder flocks were tested for the presence of chicken infectious anemia virus (CIAV) antibodies using a commercial enzyme-linked immunosorbent assay kit. Eleven of the 20 flocks (55%) and six out of seven (86%) farms were positive for CIAV antibodies. The seroprevalence largely depended on the age of the flocks. Seroprevalence was higher within the older pullet and layer flocks (83%-100%) than in the younger broiler flocks (0%-83%). In essence, all flocks older than 6 to 8 wk became infected. This is the first report of serologic evidence of CIAV in Subsaharan Africa. Since Southwest Nigeria is the main port of entry of imported chicken and the hub of major poultry breeders, the disease can probably be found throughout the country and beyond. Further studies are necessary to assess economic losses due to CIAV and the cost benefit of countermeasures.

Prevalence of antibody to chicken anaemia virus (CAV) in Swedish chicken breeding flocks correlated to outbreaks of blue wing disease (BWD) in their progeny

A serological survey for antibody to Chicken Anaemia Virus (CAV) was performed on broiler breeders as well as layer breeding birds in Sweden at the end of their rearing period. Grandparents (GP) of both types leaving quarantine were in 21 out of 26 cases free from antibody to CAV, but often became infected soon thereafter. A total of 10 outbreaks of blue wing disease (BWD) in 3 series were recorded in the broiler and layer parent generation, all of which were progeny of 3 late seroconverting GP-flocks. All but one of 22 layer parent flocks had been infected and had seroconverted during the rearing period. Subsequently BWD was not recorded from commercial layers. Broiler parent flocks were more protected from CAV infection during rearing. Eighteen out of 94 broiler parent flocks had not developed antibody to CAV before coming into lay. Outbreaks of BWD were reported in progeny flocks from all these broiler breeders, with the exception of those that had been vaccinated. Good hygienic routines along with isolation of the birds delayed the seroconversion to CAV in broiler breeders and vaccination of these breeders protected their progeny from outbreaks of BWD. Broiler flocks in houses where BWD had occurred recently had always antibodies to CAV at slaughter. It was possible to eradicate the infection from the house and prevent the infection between flocks by proper cleaning and disinfection of the broiler houses.