Oral Newcastle disease vaccination trials in Ethiopia.

Vaccination experiments were carried out in Ethiopia to study the efficacy of the NDV-I(2) vaccine against challenge with an Ethiopian velogenic strain of NDV. In experiment A, which comprised 300 broiler chicks, the efficacy of the ocular/drinking water application of the HB1/La Sota vaccine was compared with the ocular/drinking water and the feed application of the NDV-I(2) vaccine on untreated barley and sorghum. The NDV-I(2) vaccine applied by eye-drop or drinking-water protected the chickens against challenge as efficiently as combined HB1/La Sota vaccination but untreated barley and sorghum were unsuitable vaccine carriers. The vaccine virus could not be recovered and chickens neither seroconverted nor were they protected. In experiment B, 120 broiler chicks were divided into 6 treatment groups. One group each received NDV-I(2) vaccine mixed with untreated barley or sorghum which was applied immediately, or 14h after mixing and standing at ambient temperature. The fifth group was vaccinated intraocularly and via the drinking water with the NDV-I(2) vaccine. The sixth group remained untreated. Experiment B confirmed the results of experiment A. In experiment C, 100 chicks were divided into 5 groups of 20 chickens each. One group each received the NDV-I(2) vaccine on parboiled barley or sorghum as vaccine carriers 0 and 6h after mixing. The last group remained untreated. Parboiled barley given 0 or 6 h and parboiled sorghum given 0 h after mixing with the vaccine led to seroconversion and protection of the chickens. Parboiled sorghum given 6h after mixing with the vaccine did not. It is concluded that the thermostable NDV-I(2) vaccine may be a suitable vaccine for oral application under Ethiopian conditions.

Comparison of commercial ELISA test kits from Australia and the USA with the serum neutralization test in cell cultures for the detection of antibodies to the infectious laryngotracheitis virus of chickens.

The objective of this work was the evaluation under our conditions of two commercial ELISA kits for the detection of antibodies to avian infectious laryngotracheitis (ILT) virus, one from Australia (Trop-ELISA, TropBio) and one from the USA (ProFLOK-ELISA, KPL), and to compare their performance with the conventional serum neutralization test (SNT) in chick embryo liver cells. Repeatability varied considerably, particularly when using the Trop-ELISA. Therefore, if individual results are important, at least two parallel measurements per serum sample are recommended. In 89.3% of the sera tested by SNT, results of two parallel measurements did not vary by more than one 2-fold dilution step. There was good linear correlation between both ELISAs and the SNT, the correlation coefficient for the Trop-ELISA being r = 0.758 and for the ProFLOK-ELISA r = 0.867. The negative/positive cut-off was redefined to suit our conditions. Sera with a SN titre of > or = 1:4 were considered positive. Sera with < or = 15% absorption in the ProFLOK-ELISA were considered clearly negative. For the Trop-ELISA, extinctions of > or = 0.477 were considered positive, < or = 0.168 clearly negative. Values in between were regarded as doubtful for young chickens and as possibly due to non-specific reactions in older chickens. The sensitivity and specificity of the ELISAs relative to the SNT were 87 and 77% for the Trop-ELISA, and 95 and 60%, respectively, for the ProFLOK-ELISA. However, the results indicate that the sensitivity of the ELISA is higher than that of the SNT, because most sera showed similar deviations from SNT results with both ELISAs. Generally, both ELISAs were a suitable alternative to the SNT under our conditions, as long as only negative/positive results are required.

Enteropathogenic Escherichia coli in Psittaciformes.

A total of 103 Escherichia coli isolates from psittaciform birds were examined for the presence of genes coding for shigatoxin 1 (Stx1), shigatoxin 2 (Stx2) and for intimin (eae), using the polymerase chain reaction (PCR). Sixty-eight E. coli strains were isolated from necropsy cases and faecal samples, the other 35 were from 205 cloacal swabs from Psittaciformes with various conditions. All isolates were tested for enterohaemorrhagic E. coli-haemolysin (HlyEHEC), some also for Stx production, but there was no geno-typic or phenotypic evidence of Stx in any of them. Seven isolates, six from birds with diarrhoea, harboured the eae gene, three of them belonging to the O110:H6 serotype, one each to serotypes O153:H10, O131:H-, O63:H6 and Osp:H6. These seven eae-positive strains were negative for shigatoxin and HlyEHEC, and the hlyEHEC gene was not detectable by PCR. However, a PCR amplifying the enteropathogenic E. coli (EPEC)-specific bundle-forming pili structural gene bfpA detected four bfpA positive strains (three of serotype O110:H6, one O131:H-) among the seven eae positive strains, which classifies them as EPEC. Our findings suggest that shigatoxin-producing E. coli are uncommon, but that EPEC should be considered as potential pathogens in psittaciform birds, which may be a source of human EPEC infections.

[Verotoxin production and adhesion genes of E. coli isolates from commercial poultry and psittacines: detection by PCR]. / Verotoxinbildungs- und Anheftungsgene bei E.-coli-Isolaten aus Wirtschaftsgeflügel und Psittaciformes: Nachweis mittels PCR.

A total of 101 E. coli isolates from commercial poultry, companion psittacine birds and psittacine faecal samples were tested by the PCR technique for the presence of genes coding for verotoxin (slt I and slt II) production and adhesion to intestinal cells (eaeA gene). The O 157:H 7 strain EDL 933 served as positive control. Verotoxin production was assessed in Vero cell cultures. One E. coli isolate showed both alpha-haemolysis and enterohaemolysis (haemolysin production) but no gene for verotoxin production. All other isolates were negative for slt I, slt II and eaeA genes.

Comparison of the genomes of 15 avian herpes-virus isolates by restriction endonuclease analysis.

Differentiation of herpesvirus isolates has been performed mostly on the basis of biological properties and serology. In this study, 15 herpesvirus isolates from different species of birds were compared by restriction endonuclease analysis of genomic DNA. All herpesviruses were isolated in Europe or are used as vaccine viruses there. The isolates could be differentiated into seven groups based on restriction patterns. The largest group contains isolates from passeriform and psittacine birds and could further be subdivided into four subgroups. Two other groups are represented by herpesvirus isolates of quail and crane, and by isolates of pigeon and owl. Duck plague virus, herpesvirus of turkey, infectious laryngotracheitis virus and a herpesvirus isolate from tragopan all exhibited distinct restriction patterns. In general, our results parallel earlier cross-neutralization studies and yield additional, more detailed information on the relationship between different herpesvirus isolates of birds.

[Evaluation of three commercial ELISA test kits for the detection of antibodies against Salmonella enteritidis]. / Beurteilung von drei kommerziellen ELISA-Teskits zum Nachweis von Antikörpern gegen Salmonella enteritidis.

We evaluated three commercial enzyme-linked immunoassay (ELISA) test-kits, using either lipopolysaccharide (LPS) or flagellar extracts as antigens, for the demonstration of Salmonella enteritidis (S. e.) antibodies in serum and egg yolk. They were also compared with conventional serological tests, such as the pullorum rapid slide agglutination test (RST), the pullorum slow agglutination tube test and a rapid slide agglutination test, using gm flagellar extracts as antigen. We tested sera and eggs from six different layer flocks. In 84.1 to 90% of the sera and egg yolks tested the three commercial ELISA test kits gave comparable results. There were a number of serological cross-reaction with other serovars, particularly S. typhimurium. However, the possibility of infections with more than one salmonella serovar, other than S. e., cannot be excluded. The ELISA-antibody levels in serum and egg yolk ran parallel and were still high after one year. However, the level of egg yolk antibodies was on an average 33.9% lower than in serum. The S. e.-ELISA seems to be well suited for epidemiological investigations and for preventive and control measures.

Diagnosis of infectious bronchitis (IB) by examination of tracheal mucus for IB-precipitating antigens.

The use of tracheal exudates for detecting precipitating infectious bronchitis (IB) antigen by the agar-gel precipitin (AGP) technique is described. Of 47 experimentally infected tracheas, 24 gave positive precipitin lines between the second and 12th day postinfection; 9 out of 18 tracheas from birds from natural outbreaks of IB were also positive. Tests can be read within 18-24 hr. For best results, several antisera or an antiserum at various concentrations should be used.

Infectious bronchitis agar-gel precipitin test--use of infected allantoic fluid as antigen.

The use of infected allantoic fluid (AF) as precipitating infectious bronchitis (IB) antigen was investigated. The results show that unconcentrated AF harvested at the right time can be a very satisfactory precipitating IB antigen. With the majority of the virus strains used, unconcentrated AF, harvested 68 hours postinoculation (PI), showed more precipitating activity than that harvested at 20 or 120 hours PI. If further antigen concentration is required, dialysis with polyethyleneglycol MW 20,000, freeze-drying, and precipitation with polyethyleneglycol 6,000 are satisfactory methods of concentration.