A survey of disease in five commercial flocks of meat breeder chickens.

Causes of sickness and death in approximately 30,000 chickens in 5 meat breeder flocks were investigated between May 1979 and April 1980. Approximately 23% of disease was due to neoplasms; 81% of these were Marek's disease despite vaccination against this infection. Other frequent diagnoses included cellulitis (15%), respiratory disease (14%), lesions of the reproductive tract (11%) and tenosynovitis/arthritis (9%). Antibodies to Mycoplasma gallisepticium, avian adenovirus, infectious bursal disease virus and reticuloendotheliosis virus were present in all flocks. Antibody to Newcastle disease virus (NDV) was found in 2 flocks but titres were not considered protective against a virulent NDV challenge. Antibody to egg drop syndrome 1976 virus was found in 2 flocks comprised of the same breed of bird.

Experimental infection of chickens with an Australian strain of reticuloendotheliosis virus 3. persistent infection and transmission by the adult hen.

Vertical transmission of reticuloendotheliosis virus (REV) infection was demonstrated in embryonated eggs from an adult hen with persistent REV viraemia but no serum antibody. Pooling of infected embryos from this hen with those from antibody-positive hens appeared to inhibit the infectivity of congenitally-transmitted REV. REV was detected in vaginal swabs from this hen on 11 occasions over a period of 26 weeks of adult life and infectious REV was shed from the eye, mouth and in the droppings. Direct contact between the hen and other adult hens and roosters resulted in the transmission of REV infection, with or without genital contact. These newly-established REV infections were not persistent. Transmission did not occur between the infected hen and others separated by a wire mesh barrier.

A transmissible chicken tumour associated with reticuloendotheliosis virus infection.

Histiocytic lymphosarcomas of the intestine, liver, spleen and sciatic nerve were found at necropsy in a 36-week-old laying hen that was culled from a flock of 1800 birds because of emaciation. Type C particles were observed in ultrathin sections of liver and spleen. The serum of the hen contained reticuloendotheliosis virus (REV) antigen, and antibody against REV, but lacked antibodies reactive with Marek's disease virus or subgroups A and B of Rous sarcoma virus. The tumour was transmitted to chickens using a suspension of the initial tumours. These experimental tumours were then transmitted to further chickens, using cultured spleen cells, viable spleen cells that had been stored frozen, and disrupted spleen cells. The tumours, which developed after incubation periods as short as 2 weeks, were histologically similar to those in the original hen. A few chickens also developed feather abnormalities. The chickens with experimentally transmitted tumours developed antibody against REV and REV antigen was demonstrated in cultured cells from these chickens. The chickens failed to develop antibody against Rous sarcoma virus and only 1 of 29 developed antibody against Marek's disease virus.

Experimental infection of chickens with an Australian strain of reticuloendotheliosis virus. 2. Serological responses and pathogenesis.

Fifteen SPF chickens were inoculated with an Australian strain of reticuloendotheliosis virus (REV) at 1 day of age and five uninoculated chickens were readily infected by horizontal spread from this group. Antibody detectable by the immunofluorescent antibody (IFA) test developed 3 to 6 weeks after infection, and usually persisted for 20-35 weeks, with maximum titres (40-1280) at 8 to 13 weeks. Agar gel precipitin (AGP) reactions developed more slowly and were variable in duration, the highest proportion of positive reactions being detectable 8 to 13 weeks after infection and persisting for 8 to 30 weeks. Infectious REV was readily detected in the plasma and serum of inoculated chickens 6 weeks after infection and a non-infectious REV antigenaemia usually persisted for at least a further 7 weeks, in the presence or absence of antibody. Development of a detectable REV viraemia was strongly associated with poor body development and premature mortality among the inoculated chickens. In two inoculated chickens which failed to develop detectable serological reactions, a REV viraemia occurred which persisted throughout life. At autopsy, REV was re-isolated from the kidneys of most of the inoculated chickens and from the reproductive and intestinal systems of two birds 22 and 56 weeks after infection.

Infection studies on a reticuloendotheliosis virus contaminant of a commercial Marek's disease vaccine.

Reticuloendotheliosis virus (REV) was isolated in cell cultures from commercial Marek's disease (herpesvirus of turkeys) vaccine and re-isolated from the organs of vaccinated chickens. Runting and feathering abnormalities were produced when 1-day-old specific pathogen free chickens were inoculated with REV. Histopathological lesions in infected chickens were hypoplasia of the thymus, bursa and spleen, and inflammation of the proventriculus, kidneys and liver. Serological responses to REV were detected by the indirect immunoflorescence test in chickens directly inoculated with contaminated vaccine, and spread of REV infection to in-contact chickens was demonstrated by histopathological and serological investigations.

Experimental infection of chickens with an australian strain of reticuloendotheliosis virus. I. Clinical, pathological and haematological effects.

A wide range of clinical, pathological and haematological effects were found over a 40-week period in chickens inoculated at 1-day-old with a low-passage, cell-culture preparation of an Australian strain of reticuloendotheliosis virus. Feathering defects and statistically significant depression of body weights occurred in chickens up to 8 weeks of age. Other findings in birds that died or were culled during the 40-week experimental period included mild anaemia, leucopenia, heterophilia, hypoplasia of immune system organs, inflammation in visceral and nervous system organs, and bacterial or fungal infections. These results suggested that ill-thrift and death in some chickens infected with reticuloendotheliosis virus may be due to secondary infections with microorganisms subsequent to damage of immune system organs by that virus. Lymphoreticular-cell tumours of the liver, kidney or spleen were found in two birds aged 22 and 24 weeks. These results establish reticuloendotheliosis virus as a possible cause of tumours in adult fowls. Horizontal transmission of virus was demonstrated but the only abnormalities detected in the in-contact chickens were feathering defects.

Observations on Salmonella infections of birds.

During the period 1961 to 1976, 29 species of Salmonella other than Salmonella pullorum were isolated from 180 accessions of birds examined at the Animal Research Institute, Yeerongpilly. These birds were submitted to the laboratory from flocks with disease or production problems. S. typhimurium was the most frequently isolated serotype being obtained from 63% of accessions. Outbreaks of systemic salmonellosis occurred most frequently in young birds and although pathological changes were most commonly observed in visceral organs they were also seen in eyes, joints and the brain. Diseases other than salmonellosis were identified in many accessions of birds with systemic or enteric salmonella infections.

The isolation and characterisation of a Newcastle disease virus from an exotic parrot.

A newcastle disease virus was isolated from a salmon-crested cockatoo (Cacatua moluccensis) illegally introduced into Australia, Viral-characterisation and chicken-transmission studies indicated that the isolate, G5320/1, was a lentogenic pathotype. It caused a severe respiratory disease in chickens exposed oronasally at 1-day old and in chickens housed at 1 day of age with chickens infected with Newcastle disease virus. No harmful effects were detected in 5-week old chickens inoculated intravenously or oranasally with the virus.

Comparative study of experimental inclusion body hepatitis of chickens caused by two serotypes of avian adenovirus.

Twenty 1-day-old specific-pathogen-free chickens each were given an intraabdominal inoculation of either a type-8 avian adenovirus, [AMG 5 (2a], or a type-5 avian adenovirus, inclusion body hepatitis virus (IBHV). The diseases produced were similar. High (60-100%) mortality and statistically significant depression of body weights occurred in both infections. There were necrotizing hepatitis and pancreatitis, lymphoid depletion in the spleen, bursa of Fabricius and thymus, hydropericardium, nephritis and enteritis. Intranuclear inclusions occurred in affected organs. Fluorescent-antibody staining, the Feulgen reaction for deoxyribonucleic acid and electron microscopic studies, as well as studies from the literature, indicated that basophilic inclusions consisted of assembled adenovirions.

Serologic and pathogenicity studies of avian adenovirus isolated from chickens with inclusion body hepatitis.

A virus initially thought to be inclusion body hepatitis virus (IBHV), Tipton strain, was classified as an avian adenovirus (AAV) and shown to be antigenically related to 2 serotypes of AAV, 764 and YR36. The virus was antigenically unrelated to AAV serotype TR-22, which included IBHV, Tipton strain. Inoculating specific-pathogen-free chickens with the virus produced hepatitis with basophilic and eosinophilic staining intranuclear inclusion bodies.

Virus-neutralizing antibody titers against 8 avian adenovirus serotypes in breeder hens in Georgia by a microneutralization procedure.

Serums from 16 chicken-breeder flocks in Georgia were tested for virus-neutralizing antibody to 8 serotypes of avian adenovirus. Titers to all 8 serotypes were demonstrated in 8 of the flocks, titers to 7 in 6, and titers to fewer than 7 in the other 2 flocks. Although titers were high overall to some serotypes (types 2 and 8) and low to others (types 1, 4, and 5), with statistically significant differences between many titers, the data were difficult to interpret because of possible heterotypic responses of chickens infected with avian adeno-viruses. Used for titrations of serum antibody was a microneutralization procedure that is inexpensive. It proved also to provide reproducibility since titers from replicate tests differed by less than 3 twofold dilutions. In addition, there was a strong linear relation between titers obtained with the microneutralization procedure and a conventional plaque-assay titration procedure. The microneutralization procedure was less sensitive than the conventional procedure by a factor of about 5.5, but that was considered a disadvantage only with low-titered serums.

Serotyping avian adenoviruses by a microneutralization procedure.

A microneutralization procedure, using chicken kidney cell monolayers as an indicator system, was developed and applied to the serotyping of isolates characterized as avian adenoviruses. The method was determined to be reproducible, since coefficients of variation were low for 12 replicate titrations of homologous reagents of 9 prototype avian adenoviruses. Prototype reagents were specific according to results of reciprocal end point-neutralization tests and comparison of antigenic relatedness, using results obtained by previous researchers. Forty-two avian adenovirus isolates were classified into 6 serotypes by one-side end point-neutralization tests against antiserums made to 9 prototype avian adenoviruses. An additional 20 isolates were antigenically related to prototype viruses, but they could not be specifically types with the typing criteria. Different serotypes were isolated from birds having similar clinical diagnostic signs and lesions of disease.

Involvement of a type-8 avian adenovirus in the etiology of inclusion body hepatitis.

Type-8 avian adenoviruses were isolated from chickens in a commerical flock suffering an outbreak of inclusion body hepatitis. Serum-neutralizing titer to this type, but not to 7 other types of avian adenovirus, was more than 4 times as high in convalescing chickens as in chickens from the flock bled 2 weeks previously, during the disease outbreak. A disease similar to that in the commercial flock and to inclusion body hepatitis as described in the literature was produced by intra-abdominal inoculation of a type-8 isolant, AMG 5 (2a), into 1-day-old specific-pathogen-free chicks. Pathologic features of the disease included necrotizing hepatitis, pancreatitis, and severe lymphoid depletion of the bursa of Fabricius, thymus, and spleen. It was concluded that type-8 avian adenoviruses were involved in the etiology of the naturally occurring outbreak of inclusion body hepatitis.

Effect of maternal antibody on experimental infections of chickens with a type-8 avian adenovirus.

Mortality was 60% when chickens without detectable maternal antibody to avian adenoviruses were inoculated intra-abdominally with 10(6) plaque-forming units of AMG 5(2a), a type-8 avian adenovirus. Other results were macroscopic and microscopic lesions in a wide range of organs, statistically significant depression of body weights, AMG 5(2a) virus in the liver and feces, and high virus-neutralizing antibody titers to AMG 5(2a). The disease produced was similar to that described in a previous report of AMG 5(2a) infection of chickens, and similar to inclusion body hepatitis as described in the literature. In contrast, similar inoculation of chickens with maternal antibody to type-8 avian adenovirus resulted in no mortality, lesions in the liver only, no depression of body weight, AMG 5(2a) virus in the feces only, and relatively low virus-neutralizing antibody titers. During this study a hemorrhagic-aplastic anemia syndrome occurred in both AMG 5(2a)-inoculated and control chickens in one trial. Pathologic, virologic, and serologic findings indicated that the spontaneously occurring disease was not caused by an avian adenovirus.

Application of a microtiter cell-culture method to characterization of avian adenoviruses.

A microtiter cell-culture method was developed and used to titrate virus isolates for characterization. Virus dilutions and chicken kidney cell suspensions were dispensed into the wells of disposable microculture plates, with infectivity endpoints being determined microscopically on the fifth or sixth day, or by reading crystal-violet-stained monolayers on day 6. With this method, 37 candidate avian adenoviruses isolated from diagnostic accessions were characterized as avian adenoviruses (AAV). The criteria used for characterization were production of round-cell cytopathic effect, resistance to chloroform treatment, inhibition by 5-bromodeoxyuridine, and the presence of an antigen showing identity with a known AAV by precipitation in agar gel. Statistical anlaysis of eight replicate titrations of three AAV indicated that the titration method was highly reproducible. Use of the microculture method for titrations gave substantial savings in indicator cells, media, incubator space, culture dishes, and time.

Causes of disease in two commercial flocks of laying hens.

Laboratory examination of all birds that were culled or died during an eight-month period in two commerical laying flocks was performed to reveal the causes of disease and their prevalence. The average weekly total of diseased birds was greater in one flock (60-69) than the other (27-37). This resulted mainly from a high incidence in the former flock of leucoses and sarcomas, although losses due to fatty liver syndrome, prolapse and cannibalism and cage layer fatigue were also marginally greater in this flock than the second. Haemangiomas occurred more frequently in the flock with the higher disease level. A total of 273 hens of the 2,000 examined from this flock had single or multiple haemangiomas. Special features of the major causes of disease were outlined and discussed. A conclusion made from this study was that histopathological examination is necessary for accurate diagnosis of avian tumours.