C.R. Wilks

Development of an enzyme-linked immunosorbent assay to detect and quantify adenovirus in chicken tissues.

An indirect enzyme-linked immunosorbent assay (ELISA) was developed to detect and quantify avian adenovirus (AAV) in various chicken tissues, including blood. A positive ELISA absorbance value was obtained with suspensions of infected liver tissue that contained less than 100 mean tissue-culture infective doses per gram. A positive correlation was observed between the absorbance values and titer of infectious virus in infected liver tissue. A group-specific antigen common to the 12 serotypes of AAV tested was demonstrated by this ELISA. Because of the high sensitivity and broad-spectrum reactivity, this ELISA could be useful for the study of AAV pathogenesis, for laboratory diagnosis of inclusion body hepatitis irrespective of the serotype of AAV involved, and for screening commercial and specific-pathogen-free flocks for the presence of AAV.

Reproduction of inclusion body hepatitis in conventionally raised chickens inoculated with a New Zealand isolate of avian adenovirus

Conventionally raised chickens were inoculated with a local isolate of serotype 8 of avian adenovirus by an oral or intraperitoneal route, or were exposed to the infection by contact. Fatal hepatitis, resembling inclusion body hepatitis, occurred in 30% and 45% of the birds inoculated by the oral and intraperitoneal routes respectively, and severe growth depression was recorded in survivors and in birds in contact. Birds which had maternally derived virus neutralising antibody titres of 64 or greater at the time of viral exposure did not succumb to fatal infection, but their growth rates were significantly depressed.

Detection of astrovirus in the faeces of cats with diarrhoea

Examination by electron microscopy of faeces from two separate cases of young cats with diarrhoea revealed the presence of 28 nm viral particles morphologically consistent with an astrovirus. No visible cytopathic effect was observed when the virus was inoculated into a feline kidney cell culture.

Virus and virus-like particles observed in the intestinal contents of the possum,Trichosurus vulpecula

SummaryIntestinal contents derived from the Australian brush-tailed possum,Trichosurus vulpecula, were examined by negative stain electron microscopy for the presence of viruses. Out of 100 samples, 23 contained at least one type of vertebrate virus or virus-like particle. Adenovirus was identified in six samples, herpesvirus in two samples, coronavirus in four samples, and coronavirus-like particles in 14 samples. To date no viruses of the brush-tailed possum have been isolated in tissue culture but these results indicate that this species is probably host to several viral species.

Antibodies to bovine viral diarrhoea virus in beef cattle

Abstract Infection of cattle with bovine viral diarrhoea virus (BVD virus) is common throughout the world(1) and the prevalence of neutralising antibodies to the virus reported from surveys ranges from about 40% to 90%(2)(3)(4). The first isolation of BVD virus in New Zealand was reported in 1967(5) and, since that time, evidence of widespread infection in dairy cattle has been presented(6). Whilst the diseases associated with BVD viral infection have been well recognised in dairy herds, there has been a belief that infection of beef herds is less common. Based on this belief has been the fear that the growth of the dairy beef industry could lead to the introduction of BVD virus into an essentially naive beef population with disastrous results such as those reported by MacNeil and van der Oord(7). We decided therefore to sample beef cattle submitted to abattoirs throughout New Zealand for serological evidence of prior exposure to BVD virus.

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.

A comparison of the polymerase chain reaction with standard laboratory methods for the detection of EHV-1 and EHV-4 in archival tissue samples.

A detection system incorporating the polymerase chain reaction was compared with the use of histopathology and virus isolation to determine the presence of equid herpesvirus type 1 or equid herpesvirus type 4 in equine tissues submitted to a diagnostic laboratory. When the polymerase chain reaction was performed, these tissues had been stored for up to 3 years. Thirty-eight tissues representing 14 cases had been stored embedded in paraffin wax. Analysis of these tissues using the PCR gave predictive values of 1.0 and 0.91 for a positive and negative result respectively, and sensitivity and specificity values of 75% and 100% respectively. Fifty-three tissues representing 28 cases had been stored immersed in 10% formalin. Analysis of these tissues gave predictive values of 0.44 and 0.42 for a positive and negative result respectively, and sensitivity and specificity values of 28% and 57% respectively. The poor results obtained with this group of tissues was attributed to contamination of the samples during wax embedding. Viral DNA could not be amplified from older tissues. These results indicate that under appropriate conditions the polymerase chain reaction is reliable when applied to tissues collected for routine diagnosis. However, it is less reliable when samples for analysis are handled collectively. Also, storage of tissues in wax blocks for 14 or more years inhibits later amplification of viral DNA from these tissues. The implications of these results to the application of the polymerase chain reaction to routine laboratory diagnosis are discussed.

Vertical transmission of avian adenovirus associated with inclusion body hepatitis.

Using an indirect enzyme-linked immunsorbent assay, avian adenoviral antigens were detected in the yolk and albumen of eggs derived from broiler breeder chickens which were known to be infected with a strain of virus capable of causing inclusion body hepatitis. Viral antigens were detected in egg yolk (16/60) more frequently than in the albumen (5/60). Direct detection of viral antigens in eggs strongly supports the hypothesis that transovarian transmission of inclusion body hepatitis virus occurs if infection is present in breeder flocks.

Observations on BVD virus infection in New Zealand beef herds

Abstract Extract Bovine viral diarrhoea (BVD) virus has a worldwide distribution and investigations in various parts of the world have shown that 60%–80% of cattle have neutralising antibodies to the virus(1)(2). Bovine viral diarrhoea virus infection is also common in New Zealand dairy herds(3), and its epidemiology on dairy farms is well understood. It had been considered that the traditional beef cattle population was essentially free from this infection and there was a concern that the rapidly expanding dairy-beef industry may introduce infection into an essentially naive beef cattle population. However, a recent study has shown that BVD virus infection is widespread in beef herds throughout New Zealand(4). To explore the issue further, we have examined the prevalence of BVD virus antibody- positive animals in selected dairy-beef operations and traditional cow-calf herds, and how BVD-virus infection, if present, is maintained within these cattle populations.

Epidemiology of typical and atypical rotavirus infections in New Zealand pigs.

Polyacrylamide gel electrophoresis (PAGE) and enzyme-linked immunosorbent assay (ELISA) were employed to investigate the epidemiology of typical and atypical rotavirus infections in five piggeries. Of 152 faecal samples examined, 46 (30 per cent) were positive by ELISA for group A rotavirus. Rotaviruses with electrophoretic patterns resembling groups A, B and C were detected. At least two and up to five different rotavirus electrophoretypes (typical and/or atypical) were detected in each of the five piggeries. Out of 152 faecal samples examined, 28 (18 per cent) contained rotaviruses with group A electrophoretypes, 9 (6 per cent) with group C but only 1 with Group B. Six samples contained both group A and group C rotaviruses. No common electrophoretypes of group A or C rotaviruses were detected in these five piggeries. The PAGE technique was also used to analyze group A rotavirus isolated sequentially from another piggery over a three year period. A single electrophoretype was found during the first two years, but in the third year a different electrophoretype was detected.