Horizontal transmission of Aujeszky's disease virus from sheep to pigs.

Eight 2-month-old merino lambs were inoculated intranasally with different (10(2.0)-10(5.0)TCID50) amounts of Aujeszky's disease virus (ADV). Electron microscopic studies indicated that ADV replicated in extra-neural sites, in the epithelial cells of the mucosa of the upper and lower respiratory tract. Although the virus was excreted continuously in nasal discharges, horizontal transmission to contact lambs failed. The surviving exposed and contact lambs had no demonstrable antibodies against ADV and they were susceptible when challenged by ADV. However, the virus was transmitted to susceptible pigs in contact with the exposed lambs. One of the five contact pigs showed characteristic clinical signs of Aujeszky's disease, developed a nonsuppurative meningoencephalomyelitis and ADV was recovered from the brain, nasal discharge and other organs. Restriction enzyme analysis of DNA from this virus confirmed the sheep origin of the isolate. The other 4 pigs seroconverted. ADV infection in sheep is therefore a possible source of infection for pigs, but the lack of horizontal transmission in sheep was confirmed.

Aujeszky's disease of sheep: experimental studies on the excretion and horizontal transmission of the virus.

Five 5-month-old merino lambs were nasally inoculated with 10(5.0) TCID50 of Aujeszky's disease virus (ADV). The dynamics of virus excretion in the nasal discharges--in agreement with the histologic findings--indicated that ADV also replicates in extraneural sites, in the upper and lower parts of the respiratory tract. The virus was excreted continuously in the nasal discharges, even during the incubation period. The titres, with certain fluctuations, increased gradually up to the final stage of the fatal disease. Following the onset of the clinical disease, the titre of excreted virus (ranging from 10(4.0) to 10(6.0) TCID50/0.1 ml) was comparable with the ADV content found in the nasal discharge of naturally infected piglets. However, the horizontal transmission of ADV to contact lambs failed.

Colostral IgA, IgG, and IgM-IgA fractions as fluorescent antibody for the detection of the coronavirus of transmissible gastroenteritis.

Colostrum from sows and gilts inoculated with virulent transmissible gastroenteritis virus was fractionated into the 3 major immunoglobulin classes, IgA, IgG, and IgM-IgA fractions, by chromatographic and gel-filtration procedures. Each fraction was assayed for purity with rabbit anti-porcine serum and rabbit monospecific anti-porcine IgG, anti-porcine IgA, and anti-porcine IgM. These analyses showed that the IgG and IgA fractions were pure. The IgM fraction contained some IgA in the polymeric form and was designated the IgM-IgA fraction. Each Ig was assayed for virus-neutralizing activity on swine testes cells by the plaque-reduction method before and after conjugation with fluorescein isothiocyanate. On the basis of activity per milligram of protein, the virus-neutralizing titers were 1:641, 1:44, and 1:6.8 for the IgA, IgG, and IgM-IgA fractions respectively; the fluorescent antibody titers were 1:31.3, 1:0.1, and 1:15.6, respectively, for the same Ig.

Enterotoxigenic Escherichia coli, rotavirus, porcine epidemic diarrhoea virus, adenovirus and calici-like virus in porcine postweaning diarrhoea in Hungary.

In order to obtain data about the significance of enterotoxigenic E. coli (ETEC), and of the different enteric viruses in the aetiology of porcine postweaning diarrhoea, bacteriological, electron microscopic and ELISA studies were made on dead and live pigs. E. coli from the small intestine of diarrhoeal weaned pigs that died were tested for serogroups, pili (fimbriae) and toxin-geno-type. The 108 haemolytic E. coli representing 14 farms and 42 pigs were typed as follows: 0149:K88+ETEC (56.5%), OX:K88+ETEC (21.3%), O141:F18ac+ ETEC (4.6%), O147:F18ac+ETEC (3.7%), OX and O157:F18ac+ETEC (9.3%), verotoxigenic O141:F18ac (2%). In another study, when faecal samples of 92 live diarrhoeal weaned pigs (representing 19 farms) were tested, rotaviruses (18.6%), porcine epidemic diarrhoea virus (PED) (5.5%) and calici-like viruses (5.5%), and adenovirus (two pigs) were detected, besides K88+ETEC (12%) and K99+ or 987P+ETEC (one of each). Combined infections were detected in 9% of the samples. Sequential studies of diarrhoeal and nondiarrhoeal weaned and unweaned pigs indicated that PED virus and group A rotavirus were related to diarrhoea but adeno- or calici-like virus were not. It was concluded that K88+ETEC was the overwhelming aetiologic agent of porcine postweaning diarrhoea in Hungary, but F18ac+ETEC, group A rotavirus and PED virus were also significant.

Ultrastructural changes in the small intestinal epithelium of suckling pigs affected with a transmissible gastroenteritis (TGE)-like disease.

The small intestine of piglets collected during a sudden outbreak of diarrhoeal disease resembling transmissible gastroenteritis (TGE) was examined by light and electron microscopy. The principal histopathological changes were moderate infiltration by mononuclear cells in the lamina propria of the villi and cytoplasmic vacuolation. These were most pronounced in the epithelial cells covering the villous tips. By scanning electron microscopy, the intestinal villi were swollen and the transverse furrows disappeared. Microvilli were reduced in number leaving denuded areas on the brush border of the villous epithelial cells. The ultrastructural changes were restricted to the cytoplasm of affected villous epithelial cells. The cell organelles were missing in rounded areas leaving cleared areas in the cytoplasm. Parallel fascicles and bundles were seen in these areas. Viral particles with an average diameter of 70 nm were found within the dilated apical tubulo-vesicular system, free in the cytoplasm, among the microvilli, or lying free in the intestinal lumen. Viral particles surrounded a non-membrane bound viroplasm in some cases. The negatively stained particles showed a typical coronavirus morphology. These particles were found to be distinct from the known coronaviruses of swine, TGE virus and hemagglutinating encephalomyelitis virus by immune electron microscopy.