Detection of astroviruses in feces of a cat with diarrhea. Brief report

Molecular characterization of an avian astrovirus

Astroviruses are known to cause enteric disease in several animal species, including turkeys. However, only human astroviruses have been well characterized at the nucleotide level. Herein we report the nucleotide sequence, genomic organization, and predicted amino acid sequence of a turkey astrovirus isolated from poults with an emerging enteric disease.

Propagation of human astrovirus in the PLC/PRF/5 hepatoma cell line

Astroviruses are associated with gastroenteritis in humans and many diseases in animals. Human astroviruses (HAstVs) cannot be propagated readily or isolated in conventional cell cultures. The presence of trypsin supports HAstV growth in selected cell cultures such as the continuous colonic carcinoma cell line (CaCo-2). This study reports on the propagation of cell culture adapted reference strains of HAstV, and the direct isolation of HAstV from stool specimens in the human hepatoma cell line PLC/PRF/5.

Growth and characterisation of human faecal astrovirus in a continuous cell line

We report conditions for the growth of human faecal astrovirus in a continuous colonic carcinoma cell line (CaCo-2). Purified particles contained three polypeptides, one of which (24k) appeared loosely held on the exterior.

Cytopathic astrovirus isolated from porcine acute gastroenteritis in an established cell line derived from porcine embryonic kidney

A cytopathic astrovirus was isolated from pigs with acute diarrhea in an established cell line that was derived from porcine embryonic kidneys with the aid of trypsin. The virus showed a distinct cytopathic effect characterized by an enlargement of cells and the appearance of fine granules in the cytoplasm. Porcine astrovirus was shown to have an RNA genome, as determined by the effect of 5-iodo-2'-deoxyuridine on its replication, and five polypeptides with molecular masses of 13,000, 30,000, 31,000, 36,000, and 39,000 daltons; and it was shown to be stable to lipid solvents and heating at 50 degrees C for 30 min but somewhat labile to acid (pH 3.0). The buoyant density of the isolate determined in CsCl was 1.35 g/ml. Seroconversion to the virus was evident in the paired serum specimens obtained from pigs with diarrhea that were housed at the farm where the disease occurred. The neutralization test on serum specimens collected randomly from 128 adult pigs of eight herds revealed that 50 of the serum specimens were positive for antibody to porcine astrovirus, although there was considerable variation in the prevalence among herds, ranging from 0 to 83%. Hysterectomy-produced, colostrum-deprived, 4-day-old pigs developed mild diarrhea after oral exposure to porcine astrovirus propagated in the cell culture; and the virus was isolated again from diarrheal stool specimens.

Cultivation and partial characterization of bovine astrovirus

Bovine astrovirus serotype 2 (US2) was adapted to primary neonatal kidney cell (NBK) cultures by the addition of 50 micrograms ml-1 of trypsin in the medium. Infectious virus was released from the cells within 7 days post-infection in early passages and within 3 days in later passages. In the absence of trypsin, neither passage of infected cells nor release of infectious virus occurred. The virus was shown to be similar to the fecal astrovirus by a neutralization test and by ultrastructural studies of infected cells. Primary embryo bovine kidney (EBK) and NBK cell cultures supported infection with both fecal and tissue culture adapted (TCA) astrovirus. The time-related development of infection, as studied by immunofluorescence, was similar for both fecal and TCA astrovirus and for both cell culture types. The first indication of viral infection and expression of viral antigens occurred at 7 h post-infection and was characterized by the appearance of a diffuse faint immunofluorescence (IF) of the cytoplasm. Soon after, two or three brilliant IF granules were observed in the nucleus, which appeared to involve the nucleoli. Subsequently, dense granular IF was seen in the perinuclear region of the cytoplasm, which later extended to involve all the cytoplasmic area. In both EBK and NBK cultures infected with either fecal or tissue culture adapted astrovirus, only a minority of cells became infected, even when the multiplicity of infection exceeded one. Occasionally 10-20% of cells were infected, but in most cultures the proportion did not exceed 2% and in NBK cultures, from 3/9 calves, no infected cells were observed. The virus did not infect bovine cell lines. Infectivity of the virus was not removed by treatment with chloroform, and iododeoxyuridine and actinomycin D when added to the medium, did not block replication. Masses of virions were observed by electron microscopy in discrete areas in the cytoplasm, with similar distributions as the viral antigen foci as seen by IF. The mean diameter of the virions was 34 nm. In conclusion, bovine astrovirus lacks both essential lipids and an envelope, probably has an RNA genome, may have a nuclear phase of replication involving the nucleoli which is not blocked by DNA inhibitors, and has a selective cell tropism.

Virus and virus-like particles in the faeces of cats with and without diarrhoea

Negative staining electron microscopy was used to identify viruses in 166 normal and 62 diarrhoeal faecal samples from 208 cats admitted to an animal shelter during a 16-month period (March 1984 to June 1985). On the basis of size and shape 7 distinct viral types were detected: 24 nm parvovirus-like particles, 30 nm astrovirus, 30 nm picornavirus-like particles, reovirus, rotavirus, coronavirus and a 75 nm "togavirus-like" particle. The incidence of these particles in the 208 cats was 11%, 7%, 6%, 0.4%, 5%, 1% and 1% respectively. Virus isolation studies using 40 of the faecal samples succeeded in isolating reovirus 1 in 2 cases. Immune electron microscope studies demonstrated the presence of antibody in a human serum to cat astrovirus, but failed to clarify the identity of the parvovirus-like particles and picornavirus-like particles, other than showing that some of the parvovirus-like particles were not related to feline panleukopenia virus. It was found that parvovirus-like particles, astrovirus, picornavirus-like particles, reovirus and rotavirus could be excreted by cats with normal faeces as well as cats with diarrhoeal faeces. Parvovirus-like particles, astrovirus, picornavirus-like particles and rotavirus could be excreted in high concentration in normal faeces. There was no simple relationship between age and diarrhoea in the population of cats studied. Age was not a critical factor in the excretion of parvovirus-like particles, astrovirus, picornavirus-like particles and rotavirus. The incidence of diarrhoea was not clearly associated with the seasons.

Detection of astroviruses in gut contents of nude and normal mice. Brief report

Gut contents of nude and normal mice were examined by electron microscopy in association with an outbreak of diarrhea in a colony of nude mice. Virus-like particles with a morphology consistent with previous descriptions of astroviruses of other species were demonstrated in a high percentage of the animals.

Characterization of a calici-like virus (Newbury agent) found in association with astrovirus in bovine diarrhea

A bovine calici-like virus and astrovirus, present in the same fecal sample from an outbreak of diarrhea, were separated from each other by calf passage. The calici-like virus (Newbury agent SRV-1) caused anorexia, diarrhea, and xylose malabsorption in gnotobiotic calves aged 17 to 60 days, whereas the bovine astrovirus was nonpathogenic in similar calves. The calici-like virus was shown to be antigenically distinct from a previously described isolate (Newbury agent SRV-2) by two-way cross-protection experiments in calves; calves immune to homologous challenge became clinically ill and excreted virus when challenged with the heterologous virus.

Gastrointestinal disorders of the cat

Several areas of feline gastroenterology deserve critical attention in the near future. For example, as compared with the dog, little is known about the various causes of malabsorptive disease in the cat. So frequently, intestinal biopsy samples reveal nothing more than intestinal thickening with fibrosis and nonspecific mild cellular infiltration, and the inciting cause is never determined. It is, perhaps, wrong to be critical about the use of the bark of Berberis vulgaris and the root of Rheum in modern feline gastroenterology, since most of us occasionally use unconventional therapies. It has been rumored that I have been known to advocate the daily addition of a tablespoon of pumpkin-pie filling to the food of cats suffering from recurrent constipation and acquired megacolon. The rumors are true, and colonic evacuation is sometimes promoted with the use of this unusual bulking agent after traditional drug therapy has failed. We all have our weaknesses!