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.     

A primary epidemic of inclusion body hepatitis in broilers

Inclusion body hepatitis (IBH) was diagnosed in 15 broiler flocks supplied by one breeder in the South Island of New Zealand. The affected flocks suffered mortality up to 30%. Malaise and slightly increased mortality were noticed by growers from about day 12 post-hatch; mortality peaked in the fourth week, and, in most flocks, declined to normally accepted levels from day 33 on. Gross signs seen at necropsy usually included bone-marrow aplasia, atrophy of the bursa of Fabricius and the thymus, and swollen hemorrhagic livers with focal necrosis. Jaundice was seen in many surviving birds. In some flocks, there was also proventricular hemorrhage, mild tracheitis, and airsacculitis. Downgrading and condemnation rates were increased in all flocks. Eosinophilic intranuclear inclusion bodies were seen in hepatocytes of some affected birds. An adenovirus was isolated from a number of cases investigated. The disease in broilers was preceded by production drops associated with feed refusal and increased mortality in the breeder stock.     

Relationship of Campylobacter isolated from poultry and from darkling beetles in New Zealand

Campylobacter, a foodborne pathogen closely associated with poultry, is considered to be an important agent of human gastroenteritis in New Zealand. The pathways involved in the contamination of poultry flocks remain unclear; however, many vectors, such as insects, rodents, and wild birds, have been implicated. Infestation of poultry houses by insects, particularly darkling beetles (Alphitobius diaperinus), is difficult to control. Furthermore, darkling beetles are known vectors for a variety of pathogens that include Salmonella, infectious bursal disease virus, Aspergillus, Escherichia coli, and Marek's disease virus. In this investigation, the relationship between darkling beetles and Campylobacter contamination of poultry flocks was investigated. A New Zealand breeder flock and four of its progeny broiler flocks were included in the study. Samples of beetles and of intestinal excreta of the birds were cultured for the presence of Campylobacter spp. A subset of the recovered isolates was subsequently genotyped using flaA short variable region (SVR) DNA sequence analysis. A large number of Campylobacter subtypes were isolated, indicating that Campylobacter colonization of poultry is likely to arise from a number of different reservoirs. However, a set of genetically distinct isolates were found to be common to the broiler flocks and to the beetles. This research provides data that indicates that Alphitobius diaperinus may serve as a source of Campylobacter contamination of poultry. A more thorough understanding of the relationship between beetle infestation and the Campylobacter status of poultry flocks should enable progress in further development of biosecurity control measures.     

Isolation and identification of chicken infectious anemia virus in Brazil.

Seven chicken infectious anemia virus (CIAV) isolates were obtained from seven broiler flocks with poor performance in two states of Brazil. All isolates induced thymus atrophy, bone-marrow aplasia, and low hematocrit values when inoculated into 1-day-old susceptible chicks. The CIAV isolates were resistant to treatment with chloroform and were able to pass through 50-nm-pore-size filters. CIAV-specific antigens could be demonstrated in tissues of experimentally infected chicks using a monoclonal antibody specific for CIAV. These characteristics of the virus and the virus-induced lesions demonstrate that CIAV is present in Brazil and that the virus is associated with production problems.     

Characterisation of avian adenoviruses associated with inclusion body hepatitis

Eleven avian adenoviruses were isolated in monolayer cultures of specific pathogen free chicken kidney cells which were inoculated with suspensions of liver, intestine or bursa obtained from 15 broiler flocks experiencing outbreaks of inclusion body hepatitis (10 isolates) and from five unaffected flocks (one isolate). Of the 11 isolates obtained, nine were identified by virus neutralisation tests as serotype 8, one as serotype 1 and one as serotype 12. Adeno-associated viruses were only observed in combination with adenoviral particles of the serotype 12 isolate which was derived from a relatively mild outbreak of inclusion body hepatitis. Only the serotype 1 isolate, obtained from the unaffected broiler flock, consistently caused the death of embryos with marked pathological changes. All of the isolates produced basophilic intranuclear inclusion bodies surrounded by clear halos in chicken kidney cell cultures. DNA preparations, obtained from six strains of serotype 8 avian adenovirus (two New Zealand isolates, three Australian isolates and the reference strain HVI) after digestion with the restriction enzymes EcoRI and BamHI, gave electrophoretic patterns showing the New Zealand isolates to be similar to one another and to strain HVI, but quite distinct from the Australian isolates.     

Observations on Alcaligenes faecalis infection in turkeys

Experiments were initiated to study the pathogenicity of 5 Alcaligenes faecalis isolates in specific-pathogen-free poults. The isolates were recovered from commercial flocks suffering from a respiratory disease. There were no differences between cultural or biochemical characteristics of the isolates, but differences in antibiotic sensitivity were detected. All 5 isolates were capable of initiating a respiratory disease in poults similar to that seen in the early stages of turkey coryza. The infection, clinical signs, and lesions were limited to the upper part of the respiratory tract, but there were substantial differences in the severity of disease initiated by different isolates. There were also differences in the persistence of infection in the host. Secondary infections in the tracheas and sinuses were higher in poults infected with A. faecalis. The disease observed in the experimentally infected birds was milder than in 4 naturally infected flocks that also had complicating Escherichia coli infections. There was no evidence of infection with infectious bursal disease virus in 4 naturally occurring outbreaks in Ohio. It is proposed that the term turkey coryza be used to describe the disease initiated by A. faecalis.     

鸡腺胃型传染性支气管炎的病理变化

对１９９５年以来在江苏一些县市养鸡场和养鸡专业户蛋鸡群发生的鸡腺胃型传染性支气管炎的自然病例和人工感染病例进行了系统的病理学观察。自然病例和人工感染病例的病理变化基本相同。其主要眼观病理变化为腺胃显著肿大,小肠充血、出血和炎症;主要组织学变化为腺胃粘膜充血、出血、炎性水肿和浅层坏死,小肠粘膜急性炎症变化,肝、心、肾等实质细胞变性以至局灶性坏死,脾、胸腺及法氏囊的淋巴组织萎缩。     

The prevalence and genetic diversity of Campylobacter spp. in domestic 'backyard' poultry in Canterbury, New Zealand

Campylobacteriosis is the most commonly notified illness in New Zealand. Whilst the importance of commercial poultry in campylobacteriosis is well established, little is known about the possible role of chickens kept at home as a direct animal/faecal contact or consumption exposure pathway. The aim of this study was to determine the prevalence and genetic diversity of Campylobacter spp. in domestic backyard chicken flocks in the Canterbury region of New Zealand. Poultry faecal samples were collected from 35 domestic 'backyard' poultry flocks from urban and rural properties around the Canterbury Region of New Zealand. A total of 291 samples were collected and tested for the presence of thermotolerant Campylobacter spp. and positive isolates were analysed using pulsed-field gel electrophoresis (PFGE) using both SmaI and KpnI enzymes. There was a high prevalence of Campylobacter spp. with 86% of flocks testing positive. Campylobacter jejuni alone, Campylobacter coli alone and both C. jejuni and C. coli were detected in 20 (57%), 2 (6%) and 8 (23%) of the flocks respectively. SmaI/KpnI PFGE analysis identified 50 different genotypes across the 35 flocks. Genotype diversity richness was highest on the lifestyle block and farm properties with 43 different genotypes isolated, whilst urban properties displayed the least richness with 12 genotypes isolated. Rural flocks tended to have more different genotypes in a given flock than urban flocks. Comparison of the genotypes with the PulseNet Aotearoa Campylobacter database showed that 28 of the genotypes had previously been isolated from human cases of campylobacteriosis. Many of these were also indistinguishable from Campylobacter spp. previously isolated from retail chicken. Therefore, contact with backyard poultry or their faecal material is a potential additional infection pathway outside of exposure to the established pathways associated with the consumption of Campylobacter-contaminated commercial meat or foods cross-contaminated from contaminated poultry.     

Epidemiological and microbiological study of an outbreak of infectious keratoconjunctivitis in sheep

After several thousand sheep had been imported from Australia and New Zealand to Croatia during 1995, many native sheep that had been in contact with the imported animals acquired a severe ocular disease closely resembling infectious keratoconjunctivitis. In affected flocks glucose-fermenting mycoplasma were isolated from 48 per cent of conjunctival swabs and Branhamella ovis from 58 per cent. Twelve of 42 culturally and biochemically identical isolates were identified as Mycoplasma conjunctivae by polymerase chain reaction. From the conjunctivae of two animals M conjunctivae and M arginini were isolated in mixed culture. For many reasons most farmers removed the imported animals from their flocks and only sporadic cases of the disease were recognised in 1996. At the end of 1997, six flocks which were clinically free of the disease but had been affected during 1995, and five flocks with no history of the severe ocular disease were examined clinically and microbiologically, and were found to be free of M conjunctivae infection. At the time, B ovis was cultured almost exclusively from sheep originating from flocks which had been affected during 1995 and/or 1996. It was usually isolated in pure culture or as the predominant bacterial species, and was often accompanied by mild conjunctivitis. There were no microbiologically confirmed new cases of infectious keratoconjunctivitis during 1998 and 1999.     

A serological and virological survey for evidence of infection with Newcastle disease virus in Australian chicken farms

OBJECTIVE: To determine the prevalence and distribution of antibodies to Newcastle disease virus on Australian chicken farms and to determine the pathotype and relationships of the Newcastle disease viruses present on those farms. DESIGN: A cross-sectional survey of 753 commercial chicken farms. PROCEDURE: The survey comprised a detailed questionnaire and collection of venous blood samples. The titre of antibodies to Newcastle disease virus was determined by haemagglutination inhibition. Virus isolation was conducted from cloacal and tracheal swabs taken from chickens in serologically positive flocks. Virus isolates were pathotyped on the basis of the deduced Fusion protein cleavage site determined by nucleotide sequencing of a 265 bp region of the genome in the region of the cleavage site. RESULTS: Antibody evidence of Newcastle disease virus infection was found on 300 of the 753 surveyed farms throughout all 11 geographic regions of the survey. The highest prevalence occurred in the Sydney basin, New South Wales and Victoria east regions. Antibody titres were also highest in the regions where serologically positive flocks were most prevalent. The 259 virus isolates revealed nine different RNA sequences. Of the nine virus groups isolated, the most common group W was identical in sequence to the V4 vaccine strain. Five of the other groups had novel RNA sequences in the region of the F protein cleavage site. CONCLUSIONS: Antibodies to Newcastle disease virus are highly prevalent in the Australian chicken flock but all identified strains were avirulent in nature.     

Descriptive summary of an outbreak of porcine post-weaning multisystemic wasting syndrome (PMWS ) in New Zealand

CASE HISTORY: Investigations were conducted to determine the cause of an acute, multi-farm outbreak of porcine respiratory disease that included diarrhoea and subsequent loss of body condition in affected pigs. A definition for post-weaning multisystemic wasting syndrome (PMWS) including both clinical and pathological features, previously developed for the pig industry in New Zealand, was applied to the current outbreak. In addition to self-reporting by owners of affected farms, local veterinarians, disease and epidemiology consultants, and animal health officials from the Ministry of Agriculture and Forestry (MAF) were involved in conducting farm visits and submission of diagnostic specimens. CLINICAL FINDINGS AND DIAGNOSIS: Pathogens known to be endemic in the pig industry in New Zealand as well as likely exotic diseases were excluded as causative agents of the outbreak. Clinical signs including dyspnoea, diarrhoea, and rapid loss of body condition were consistent with the New Zealand case definition for PMWS. Interstitial pneumonia, pulmonary oedema, generalised lymph-node enlargement, and presence of porcine circovirus type 2 (PCV2) inclusion bodies were consistently identified in affected pigs. Classical swine fever virus (CSFv), Porcine reproductive and respiratory syndrome virus (PRRSv), and Influenza virus were ruled out, using molecular and traditional virological techniques. Spread of the disease between farms was hypothesised to be facilitated by locally migrating flocks of black-backed seagulls. The original source of the disease incursion was not identified. DIAGNOSIS: Based on the consistent presence of circovirus-associated lesions in lymphoid tissues in combination with generalised enlargement of lymph nodes, histiocytic interstitial pneumonia, clinical wasting, and poor response to antibiotic therapy, a diagnosis of PMWS was made. CLINICAL RELEVANCE: PMWS should be considered in the differential diagnoses of sudden onset of respiratory dyspnoea, diarrhoea, and rapid loss of body condition in young pigs in New Zealand pig herds.     

Chicken anemia virus in broilers: dynamics of the infection in two commercial broiler flocks

Chicken anemia virus (CAV) can cause a disease syndrome characterized by severe anemia, bone marrow atrophy, and severe immunosuppression in young chicks. Maternal antibodies prevent these clinical signs but do not prevent infection, transmission of the virus, or immunosuppression. The clinical disease is rare today because of the widespread practice of vaccinating breeders, but the subclinical form of the disease is ubiquitous. The dynamics of CAV infection, CAV antibody responses, relative lymphoid organ weights, and associated lesions were studied in two broiler flocks from a commercial producer. Both groups had detectable CAV antibodies at hatch, which waned over the first 3 wk of life. Both groups had detectable CAV DNA in both thymi and bursae over the same period. At 35 days of age, virus was detectable by polymerase chain reaction in 16 of 20 chickens, and 7 of 20 had detectable antibodies. By 42 days of age, virus was detectable in 18 of 20 chickens, and 18 of 20 had antibodies to CAV. We observed a decrease in relative thymic weights beginning at 35 days of age, coincidental withthe detection of CAV in the thymus. Bursal sizes began to decrease at 28 days of age, coincidental with a rise in antibody titers to infectious bursal disease virus. In this study, we demonstrated that under typical field conditions CAV infections in broilers have unique dynamics unlike those reported in egg laying strains of chickens managed under specific-pathogen-free conditions.     

Application of modelling to determine the absence of foot-and-mouth disease in the face of a suspected incursion

AIM: To use disease modelling to inform a response team about the number of animals per herd/flock to be examined, and the start date and duration of clinical surveillance required to be confident that foot-and-mouth disease (FMD) was not present on an island in New Zealand with a population of approximately 1,600 cattle, 10,000 sheep and a small number of pigs, goats and alpacas. METHODS: Because the probability of detecting clinical disease in (the) primary case(s) in larger herds and flocks was extremely low, deterministic and stochastic mathematical SLIR (susceptible, latent, infectious, recovered) models for the transmission of infection were constructed to estimate the date when clinical lesions in herds and flocks would be detected with 95% confidence. Surveillance targeted the first wave of infections following a suspect index case. RESULTS: If 70 cattle in herds of about 400 cattle were examined it was estimated it would take approximately 13 (90% stochastic range 9-19) days from first exposure before it would be possible to achieve 95% confidence for detecting clinical signs for a low-virulence virus, and 9 (7-14) days for a high-virulence virus. The duration of sufficiently accurate clinical detection was 17 (15-19) days and 13 (12-14) days for low- and high-virulence viruses, respectively. A sample of 70 sheep from flocks of >1,000 would be required to achieve clinical detection at about the same time but with a shorter period of detection than for cattle. The duration of effective detection could be increased by examining a larger sample in most sheep flocks, however the small size of many cattle herds in the study population limited the confidence of detecting group-level disease in cattle, therefore necessitating repeated herd inspections. The model suggested that group-level detection was not feasible if it was based on elevated body temperature alone because of short durations of fever in infected animals. CONCLUSION AND CLINICAL RELEVANCE: Simulation modelling is a useful and powerful tool for informing ongoing surveillance activities in the face of an exotic disease incursion. Results of modelling suggested to start clinical inspection activities at 4 days and to continue regular inspection twice a week for about 35 days after the date of first exposure, to satisfy the required 95% confidence threshold of clinical detection of FMD in cattle herds and sheep flocks.     

Pathogenicity of a low-virulence duck virus enteritis isolate with apparent immunosuppressive ability

Duck enteritis virus (DEV) was isolated from commercial 2-to-6-wk-old white Pekin ducks experiencing 25%-30% mortality and high morbidity. Secondary infections with Pasteurella multocida, Riemerella anatipestifer, and Escherichia coli were frequently seen in affected ducks. The isolated virus was identical to the prototype DEV by virus neutralization test but differed from the classic DEV by causing lymphoid organ atrophy and inconsistent hemorrhagic lesions in the intestinal annular bands. Attempts to reproduce the disease in white Pekin ducks were unsuccessful until the virulence of the virus was increased by three passages in Muscovy ducklings. Significant thymic atrophy (P < or = 0.001) was detected during the first 10 days postinfection (DPI), but thymus size returned to normal by 17-24 DPI. However, bursal atrophy increased significantly (P < or = 0.001) from 4 DPI until the end of the experiment (39 DPI). Reduction in body weight was significant (P < or = 0.05) between 4 and 6 DPI. There was massive depletion of thymic and bursal lymphocytes with lymphoid necrosis in the thymus, bursa, spleen, and Harderian gland. Eosinophilic intranuclear inclusions were observed in thymus, bursa, spleen, esophagus, cloaca, liver, conjunctiva, and Harderian gland. Occasional intracytoplasmic inclusions were also found scattered in the epithelial cells of conjunctiva, esophagus, bursa of Fabricius, and cloaca. Virus was recovered from experimentally infected ducks from thymus, bursa, spleen, liver, kidneys, trigeminal ganglion, and cloaca during the first 10 days of infection. These findings suggest that a low-virulent DEV can cause a massive lymphoid atrophy and can sustain immunosuppression as noted by the secondary bacterial infection.     

Occurrence and significance of infectious bronchitis virus variant strains in egg and broiler production in the Netherlands

Despite vaccination against Infectious bronchitis virus (IBV) with the Massachusetts type vaccine viruses H120 and H52 in the Netherlands, an increasing number of properly vaccinated flocks have suffered from the disease since 1978. In the years 1978-1982, the virus was isolated from 162 IBV suspected flocks. Cross-virus-neutralization tests showed that the majority (67 per cent) of these isolates belonged to serotypes other than the Massachusetts type, the Connecticut-, Florida-, Iowa 97-, Iowa 609- and JMK serotype. The majority of these Dutch isolates could be divided into 4 serogroups, called D207, D212, D3128 and D3896. Only a few isolates were not related to these serotypes. A survey of 328 flocks for antibody against these serotypes demonstrated that antibody against one or more of these novel serotypes were present in most of the flocks. Experiments demonstrated that vaccination with the H120 vaccine virus was not able to protect chickens against the adverse effects of a challenge with the novel serotypes.     

Genetic typing and prevalence of Border disease virus (BDV) in small ruminant flocks in Spain

Between 2001 and 2002, samples from 1,413 animals in 21 Spanish small ruminant flocks, most of them with animals showing clinical signs compatible with Border disease (BD), were screened for the presence of Pestivirus antigen and antibodies by an indirect peroxidase monolayer assay (IPMA) and the virus neutralization test (VNT), respectively. Although all flocks harboured seropositive animals, virus could only be isolated from animals in five of the flocks. Between 4 and 11 months later all animals older than 6 months in three of the flocks were resampled. At this time, 51-83% of them had neutralizing antibodies. The prevalence of persistently infected (PI) animals within two of the flocks was 0.3 and 0.6%, respectively. The third flock presumably had eliminated all the PI animals. Fourteen virus isolates were obtained. The 5' untranslated region (5'UTR) was amplified by RT-PCR and directly sequenced. Phylogenetic analyses classified them as a group of Border disease viruses (BDV), separated from BDV-1, but showing a relatively low bootstrap value. Three of the 14 isolates were in the same subgroup as a set of formerly characterised Spanish isolates from the Basque Country, which were allocated to subgroup BDV-C. In addition, they were in the group with an isolate from chamois, which is currently allocated in group BDV-4. Because of its close relation to the chamois isolate, these isolates were tentatively reallocated in a subgroup BDV-4a. The remaining isolates generated a new subgroup, related but not in the same cluster as the chamois isolate, and was therefore tentatively assigned to a new subgroup BDV-4b. Our results show that classification and nomenclature of BDV needs to be harmonised.     

Molecular and phenotypic characterization of infectious bursal disease virus isolates

Two infectious bursal disease viruses (IBDVs 1174 and V1) were isolated from IBDV-vaccinated broiler flocks in California and Georgia. These flocks had a history of subclinical immunosuppression. These isolates are commonly used in IBDV progeny challenge studies at Auburn, AL, as well as vaccine manufacturer's vaccine efficacy studies, because they come from populated poultry-producing states, and are requested by poultry veterinarians from those states. Nested polymerase chain reaction (PCR) generated viral genome products for sequencing. A 491-bp segment from the VP2 gene, covering the hypervariable region, from each isolate was analyzed and compared with previously sequenced isolates. Sequence analysis showed that they were more closely related to the Delaware (Del) E antigenic variant than they are to the Animal Health Plant Inspection Service (APHIS) standard, both at the nucleotide level (96%, 97%) and at the amino acid level (94%, 97%). Both isolates had the glutamine to lysine shift in amino acid 249 which has been reported to be critical in binding the virus neutralizing Mab B69. Phenotypic studies showed that both isolates produced rapid atrophy of the bursae and weight loss, without the edematous bursal phase, in 2-wk-old commercial broilers having antibody against IBDV. A progeny challenge study showed both isolates produced more atrophy of the bursae (less percentage of protection) than the Del E isolate. Molecular and phenotypic data of these important IBDV isolates help in the improved detection and control of this continually changing and important viral pathogen of chickens.