Serological and bacteriological investigations of chickens from flocks naturally infected with Salmonella enteritidis

Groups of 10 birds were obtained from four flocks which had shown evidence of natural salmonella infection. S enteritidis had been isolated from three flocks and S typhimurium from the fourth. Each bird was housed in a separate cage and blood samples and cloacal swabs were taken weekly to follow the course of natural infection. After four weeks the birds were killed and examined post mortem. The isolation of Salmonella species could not be related to the serological results. In individual birds the rapid slide test and tube agglutination test could not be relied upon to detect infection; the microantiglobulin test and the enzyme-linked immunosorbent assay (ELISA) were more sensitive than the other tests and detected some infected birds that were negative by the rapid slide and tube agglutination tests, and also showed high titres in some birds from which Salmonella species could not be isolated post mortem. Sera obtained from two flocks which had a history of natural S enteritidis infection were evaluated by all the tests; evidence of infection was found with the microantiglobulin and ELISA tests but not with the other tests.     

Protection of newborn calves against fatal multisystemic infectious bovine rhinotracheitis by feeding colostrum from vaccinated cows.

To determine whether consumption of colostrum with high levels of serum neutralizing antibody to bovine herpesvirus 1 would protect neonatal calves from the frequently fatal multisystemic form of infectious bovine rhinotracheitis, Holstein calves were fed for 48 h after birth with either pooled colostrum from seropositive vaccinated cows or colostrum from seronegative unvaccinated cows. The serum neutralizing antibody achieved in the former calves was between 64 and 256 and the titer in the latter calves was below 8. At 48 h of age the calves were challenged by aerosolization with bovine herpesvirus 1. All five seronegative calves died or were euthanized in a moribund state between days 5 and 7 of the trial, whereas all five seropositive animals remained healthy throughout the study. Twice daily clinical examination revealed significantly lower scores in the seronegative group from 60 h postinfection. Relative lung weights were greater in the seronegative group, associated with a severe acute necrotizing bronchiolitis with fibrin exudation. The seronegative group of calves also demonstrated an acute necrotizing rumenitis, pharyngitis, glossitis, esophagitis, laryngitis and tracheitis. The seropositive animals had only small areas of subacute necrotizing fibrinopurulent rhinitis. Bovine herpesvirus 1 virus was isolated from all nasal passages of all calves but isolation of virus in the seronegative calves was made from the trachea (5/5), lung (4/5), bronchial lymph nodes (4/5), spleen (4/5), thymus (3/5), liver (2/5), rumen (2/5) and brain (1/5).(ABSTRACT TRUNCATED AT 250 WORDS)     

Serological response of chickens either vaccinated or artificially infected with Haemophilus paragallinarum

The serological response of chickens either vaccinated or artificially infected with Haemophilus paragallinarum (Hpg) serovar A or C was investigated using both a specific hemagglutinin (HA) antigen and a common HA antigen. With Hpg serovar A, both vaccinated and artificially infected chickens produced hemagglutination-inhibition (HI) antibodies to Hpg serovar-specific and Hpg common HA antigens. Most chickens vaccinated with Hpg serovar C had detectable HI antibodies to both types of HA antigen by 3 weeks postvaccination, after which titers gradually declined. In contrast, most chickens artificially infected with serovar C produced HI antibodies to only the common HA antigen; very few of these chickens produced HI antibodies to the serovar-specific HA antigen.     

Enzyme-linked immunosorbent assay with a Salmonella enteritidis antigen for differentiating infected from vaccinated poultry

The specificity and sensitivity of indirect ELISA, based on the use of four different antigenic extracts obtained from a clinical isolate of Salmonella enteritidis, were compared with those obtained with the gm-flagellin based ELISA (IDEXX). A total of 116 serum samples from salmonellae free, naturally infected and vaccinated hens were studied. The results showed that the indirect ELISA, based on lipopolysaccharide (LPS), O-polysaccharide (PS) or membrane sediment (SD) antigens, enable the identification of a greater number of infected birds and discriminated field antibody responses from vaccinal ones better than the commercial IDEXX test. The indirect ELISA that used a O-polysaccharide rich fraction (PS) proved to be the most specific and sensitive test, suggesting that this indirect ELISA could be used to confirm IDEXX results, especially when the differentiation between vaccinated and infected poultry is required.     

Serological response of chickens naturally infected with Salmonella typhimurium detected by ELISA.

Four laying flocks of chickens in Britain, each with a history of Salmonella typhimurium infection, were investigated serologically and bacteriologically. Blood samples were taken from identified birds from a single house on each site and sent to the Central Veterinary Laboratory, Weybridge for serological examination using enzyme-linked immunosorbent assays (ELISA) and rapid slide agglutination test (RST) using stained S. pullorum. The identified birds were taken to the local Veterinary Investigation Centre for bacteriological examination. On site A no salmonellae were recovered from birds in the house chosen for serological examination. Of these birds approximately 20% had antibodies to S. typhimurium in ELISA which used either a lipopolysaccharide (LPS) or heat-extract (HE) antigen from S. typhimurium. S. typhimurium was recovered from birds in one other of the four houses on the same site; these birds were not tested serologically. On site B, S. typhimurium was isolated from 8% of the birds examined. Of the total tested serologically, a third to half were seropositive by S. typhimurium ELISA using the LPS and HE antigen respectively. A small proportion of birds was seropositive by S. enteritidis ELISA and RST. No salmonellae were isolated from the other two sites although about 10% of birds tested on site C were seropositive in S. typhimurium ELISA. Cross-reactions were seen between S. typhimurium antigens in the ELISA and experimentally prepared antiserum to S. enteritidis. The S. enteritidis ELISA was generally more specific although cross-reacting antibodies were detected in sera from birds on sites A and B.     

Decreased serum apolipoprotein A-I concentrations in cows infected with Salmonella typhimurium.

Serum apolipoprotein A-I concentrations in cows infected with Salmonella Typhimurium were evaluated to assess its relevance in salmonellosis. Apolipoprotein A-I has been shown in rats to be secreted by the intestine as well as the liver. Clinical symptoms such as diarrhea revealed an outbreak of salmonellosis in 22 cows on a farm, and sera were obtained at 6 (acute phase), 16, 28 (convalescent period) and 42 d (postconvalescent period) after the outbreak. Apolipoprotein A-I concentrations (mean +/- SD, mg/mL), determined by ELISA, were 0.598 +/- 0.497 (day 6), 0.111 +/- 0.060 (day 16), 0.432 +/- 0.311 (day 28) and 0.727 +/- 0.516 (day 42). Compared with the concentration at day 42, those at 16 and 28 d were significantly (P < 0.01, P < 0.05) lower, but that at day 6 was not. The serum concentration of apolipoprotein B-100 (of liver origin in cattle) was unaltered during the course of salmonellosis. The concentration of apolipoprotein A-I was positively correlated with those of serum total cholesterol (r = 0.589, P < 0.01) and phospholipids (r = 0.590, P < 0.01). These results suggest that apolipoprotein A-I in cattle is in part of intestinal origin, and also that its decreased serum concentration in salmonellosis can be attributed to the reduced intestinal synthesis or secretion of this apolipoprotein. Moreover, as a potential carrier for dietary lipids such as cholesterol, determination of serum apolipoprotein A-I concentration is suggested to be useful when assessing the nutritional status of the affected cows.     

Measurement of telomerase activity in bovine leukaemia virus infected cows

Telomerase adds new telomeric sequences to the end of chromosomal DNA in order to overcome the end-replication problem. The upregulation of telomerase activity in tumours has been reported in humans and some mammals and is considered to be a tumour marker; however, such activity has not been investigated in cows. Therefore, we investigated telomerase activity in bovine leukaemia, the most common tumour in cows and its relationship with the bovine leukaemia virus (BLV) infection, which is the major cause of leukaemia. Telomerase activity was detected in 25 of 29 bovine leukaemia tissue samples. In peripheral blood lymphocytes (PBL) from BLV-infected cases that did not develop the tumour, telomerase activity was detected in 11 of 71 cases (15.5%). When these cases were classified based on serological tests and the peripheral blood lymphocyte count, the telomerase activity was observed to be the highest in the seropositive, non-lymphoproliferative (PBL<8000 microl(-1)) cases (three of seven cases, 42.9%), and not observed in the lymphoproliferative cases (PBL<16,000 microl(-1)) except in one case. Although the precise pathogenesis of BLV-related diseases remains obscure, persistent lymphocytosis is considered as a pre-neoplastic state. In contrast, our results suggested that given the fact that telomerase activity indicates tumour development, the aleukaemic stage could be defined as the 'pre-neoplastic state'. In conclusion, similar to many tumours in humans, telomerase activity was detected in bovine leukaemia; further, this activity can be a potentially useful prediction marker for tumour development and/or a good therapeutic target.     

Detection of viral antigen in placenta and fetus of cattle acutely infected with bovine viral diarrhea virus.

The reproductive organs and fetuses of seven Norwegian Red heifers were investigated for the presence of bovine viral diarrhea virus (BVDV) antigen during the time of initial transplacental transmission of the virus. The heifers were inoculated with a noncytopathogenic BVDV at day 85/86 of gestation and were slaughtered at day 7, 10, 14, 18, or 22 postinoculation (pi). Cryostat sections of uterus, ovaries, placentomes, intercotyledonary fetal membranes, and fetal organs were examined using immunohistochemical techniques. A double immunofluorescence technique was used to identify cells that showed staining with antibodies against the leukocyte common antigen CD45 or the intermediate filament vimentin and BVDV antigens. The earliest stage of infection at which BVDV antigen could be detected in the fetuses was 14 days pi. At this stage, BVDV antigen was detected in cells of mesenchymal origin in the lungs and in large cells that morphologically resembled immature megakaryocytes in the liver. In the intercotyledonary fetal membranes and in the placentomes, BVDV antigen was not detected until 18 and 22 days pi, respectively. BVDV antigen was not detected in maternal tissue from any of the heifers. The present results indicate that fetal infection with BVDV can take place without preceding or simultaneous high concentrations of BVDV in uterus or placenta of acutely infected heifers.     

Detection of antibodies to the nonstructural protein (NS1) of influenza A virus allows distinction between vaccinated and infected horses.

Antibodies to the nonstructural protein (NS1) of A/equine/Miami/1/63 (H3N8) influenza virus were detected exclusively in the sera of mice experimentally infected with A/Aichi/2/68 (H3N2) and horses infected with A/equine/Kentucky/1/81 (H3N8) or A/equine/La Plata/1/93 (H3N8), but not in those of the animals immunized with the inactivated viruses, by enzyme-linked immunosorbent assay (ELISA) using a recombinant NS1 as antigen. The results indicate that the present method is useful for serological diagnosis to distinguish horses infected with equine H3 influenza viruses from those immunized with the inactivated vaccine.     

Recombinant polypeptide from the gp48 region of the bovine viral diarrhea virus (BVDV) detects serum antibodies in vaccinated and infected cattle.

To characterize the immune response of cattle to bovine viral diarrhea virus (BVDV) glycoprotein gp48, we have produced a large amount of recombinant glutathione-s-transferase-gp48 (GST-gp48) fusion protein in Escherichia coli. Antibodies to gp48 were present in cattle vaccinated with killed or modified-live virus vaccination, or following natural infection. These results were in agreement with results of serum neutralization (SN) test which detected gp53 of BVDV.