The isolation of rotavirus from calves,foals, dogs and cats in New Zealand.

The incidence of rotaviruses in calves, foals, dogs and cats in the Dunedin urban and rural areas was investigated using electron microscopy and enzyme-linked immunosorbent assays. Of the 283 faecal specimens examined, 26% were positive for rotavirus.

Comparison of the genetic electropherotypes was made by separating the viral dsRNA segments using polyacrylamide gel electrophoresis. It is possible that rotavirus infection is a zoonotic disease.     

The efficacy of colostrum from cows vaccinated with rotavirus in protecting calves to experimentally induced rotavirus infection

Calves which were continuously fed colostrum from vaccinated cows for the first ten days of life, were fully refractory to experimental infection with strain 81/36 F of bovine rotavirus. By contrast, the response to virus exposure of calves which were treated with normal colostrum was identical to that of the control calves, in that they underwent severe diarrhea and a significant slowing of the growth rate. The antibody titer in the milk of vaccinated cows tends to decline rapidly so that it no longer provides any protective effect. Two alternatives were considered feasible in improving prophylaxis for rotavirus infections: (a) the continuous feeding of calves with 1st day colostrum as part of the ration throughout the period of greatest risk (first week of life), or (b) enhancing the efficacy of the vaccine in pregnant cows to the point where antibody concentration in the milk would remain at a protective level.     

Longitudinal survey of rotavirus infection in calves

A longitudinal survey of rotavirus infection in heifer calves was carried out on a closed Friesian dairy herd over two successive calving seasons. Rotavirus was detected by electron microscopy in the faeces of 45 of 57 (79 per cent) calves examined. On average the virus was first detected at 6.1 days of age. Clinically the disease associated with rotavirus infection was of mild to moderate severity. Only one infected calf required intravenous fluid therapy. Diarrhoea or excretion of abnormal faeces was associated with rotavirus infection in 58 per cent of infected calves, while in the remaining 42 per cent infection was subclinical. The cycle of rotavirus infection was broken by thorough cleansing and disinfection of the calf house.     

Characterisation of rotavirus isolates from sub-clinically infected calves by genome profile analysis

Rotaviruses isolated from 43 sub-clinically infected calves from a single farm were analysed by genome profile analysis. The isolates showed genomic variation and eight different profiles were observed, including one which was atypical for Group A rotaviruses. The 3' terminal labelling method for the analysis of genome profiles used in this study required only 1 ng of viral RNA, an increase of 1000-fold in sensitivity over ethidium bromide staining for detecting all rotavirus genome segments. However, dual infections involving two rotaviruses with distinct profiles could not be detected if the concentrations of the viruses differed by greater than 10-fold.     

A study of cytopathic rotavirus strains isolated from calves with acute enteritis

Nine cytopathic bovine rotavirus strains were isolated in MA-104 cell cultures from fecal specimens of dairy calves suffering from diarrhea. Isolation of the virus was accomplished from three outbreaks which occurred on dairy farms located in Central and Southern Italy. Fecal suspensions were treated with a high concentration (1000 micrograms/ml) of trypsin, and inoculated into MA-104 cell cultures grown out in Eagle's minimum essential medium (MEM) containing 5 micrograms/ml of the enzyme. Cytopathic effects (CPE), characterized by intracytoplasmic inclusion bodies of different sizes and shapes, were observed on the 1st passage with five of the strains and on the 2nd (2 strains) or the 3rd (2 strains) passage for the others. The presence of trypsin and the use of MA-104 cells appeared to be essential for the occurrence of CPE, inasmuch as no CPE was detected when trypsin was omitted in the MA-104 cell system. Replication failed to occur when primary bovine embryo kidney cell cultures with or without trypsin were used. Electron microscopy revealed the presence of particles with a typical rotavirus morphology. In MA-104 cells, the titre of virus reached its maximum 48 hr after inoculation. Small, clear-cut plaques were produced by the isolates in MA-104 cells under the overlay of MEM containing carboxymethyl cellulose, trypsin and DEAE-dextran. The nine rotavirus strains were antigenically related, whereas the relationship to either the Nebraska or the Compton rotaviruses was quite weak.     

Diarrhoea in dairy calves reduced by feeding colostrum from cows vaccinated with rotavirus

Forty-two dairy calves remained with their dams for two days after birth, and then were removed to a calf rearing shed. Calves were allocated to three groups for the next 14 days, and received twice daily either whole milk, whole milk with a 10 per cent supplement of pooled normal bovine colostrum or whole milk with 10 per cent supplement of colostrum from cows vaccinated with rotavirus. A natural outbreak of diarrhoea occurred, affecting 28 of the 42 calves. Feeding immune colostrum delayed the onset of diarrhoea, and reduced its incidence, duration and severity. Live weight gains were consequently improved. The group fed normal colostrum had diarrhoea intermediate in severity between that of control calves and those fed immune colostrum. The aetiology of the diarrhoea was complex, with calves excreting rotavirus, enteropathogenic Escherichia coli and cryptosporidia.     

The isolation of leptospira serotypes copenhageni and ballum from healthy calves

Abstract

Extract

Bovine Leptospirosis was first recognized in New Zealand in 1950 (Anon., 1951 Anon. N.Z. Department of Agriculture Annual Report 1950–51 1951 28 28  [Google Scholar]). Since then the infection has become widespread, particularly during wet spring and summer months (Anon., 1973 Anon. N.Z. Ministry of Agriculture and Fisheries , Research Division Annual Report 1972–73 1973 (in press)  [Google Scholar]). In calves, infection with serotype pomona frequently gives rise to haemoglobinuria and general malaise, while symptoms such as loss of condition and pendulous abdomens which appear suddenly and are followed by sudden death have been associated with copenhageni infections (Dodd and Brackenridge, 1960 Dodd, D. C. and Brackenridge, D. T. 1960. Leptospira icterohaemorrhagiae AB infection in calves. N.Z. vet. J., 8: 71–76. [Taylor &; Francis Online] , [Google Scholar]).     

The isolation of a virus resembling a polyomavirus from normal calves

Viruses with characteristics of polyomaviruses were isolated from the kidneys of 18 out of 64 clinically normal calves 1-2 weeks old. All the viruses were serologically related.     

Latex test for rapid rotavirus diagnosis in calves

A latex agglutination test (LA) was compared with direct electron microscopy (EM) for detection of rotavirus infection in calves. A total of 375 samples from 62 calves were collected. Samples were taken when the calves were 1, 3, 5, 7, 10 and 20 days old and some scours samples were collected as well. Altogether 45/375 (12%) specimens were positive in LA and 10/375 (2.7%) were positive in EM. Samples positive in EM were also positive in LA. Out of the 62 calves studied 26/62 (42%) were positive in LA and 8/62 (13%) in EM. We found the LA very easy to perform, to be more sensitive than the EM method and probably a rather specific method for detection of rotavirus infection.     

Pathology of natural rotavirus infection in clinically normal calves

During a longitudinal study of the epidemiology of rotavirus infection in a calf rearing unit, excretion of virus in faeces was detected by enzyme-linked immunosorbent assay in 40 of 48 (83 per cent) unweaned calves aged between three days and five weeks. Fifty per cent of the infected calves had no clinical signs of disease. Enterocytes containing rotavirus antigen and intestinal lesions were found in all of 12 clinically normal calves selected for necropsy between days 1 and 4 of virus excretion. Stunting and fusion of villi, exfoliation, disarrangement and vacuolation of enterocytes and the presence of cuboidal enterocytes were observed in infected calves but not in rotavirus-free control calves. Lesions predominated in the upper small intestine, where rotavirus was most abundant, especially on the first two days of virus excretion. The numbers of enterocytes infected with rotavirus diminished before the lesions resolved.     

Isolation of rotavirus from calves, foals, dogs and cats in New Zealand

The incidence of rotaviruses in calves, foals, dogs and cats in the Dunedin urban and rural areas was investigated using electron microscopy and enzyme-linked immunosorbent assays. Of the 283 faecal specimens examined, 26% were positive for rotavirus. Comparison of the genetic electropherotypes was made by separating the viral dsRNA segments using polyacrylamide gel electrophoresis. It is possible that rotavirus infection is a zoonotic disease.