First international collaborative study to evaluate rabies antibody detection method for use in monitoring the effectiveness of oral vaccination programmes in fox and raccoon dog in Europe.

The most effective and sustainable method to control and eliminate rabies in wildlife is the oral rabies vaccination (ORV) of target species, namely foxes and raccoon dogs in Europe. According to WHO and OIE, the effectiveness of oral vaccination campaigns should be regularly assessed via disease surveillance and ORV antibody monitoring. Rabies antibodies are generally screened for in field animal cadavers, whose body fluids are often of poor quality. Therefore, the use of alternative methods such as the enzyme-linked immunosorbent assay (ELISA) has been proposed to improve reliability of serological results obtained on wildlife samples. We undertook an international collaborative study to determine if the commercial BioPro ELISA Rabies Ab kit is a reliable and reproducible tool for rabies serological testing. Our results reveal that the overall specificity evaluated on naive samples reached 96.7%, and the coefficients of concordance obtained for fox and raccoon dog samples were 97.2% and 97.5%, respectively. The overall agreement values obtained for the four marketed oral vaccines used in Europe were all equal to or greater than 95%. The coefficients of concordance obtained by laboratories ranged from 87.2% to 100%. The results of this collaborative study show good robustness and reproducibility of the BioPro ELISA Rabies Ab kit.

Prion protein gene polymorphism in healthy and BSE-affected Slovak cattle.

Variation of the PrP gene was examined in healthy and BSE-affected Slovak cattle. According to previous studies, the 23-bp indel polymorphism is supposed to be associated with higher susceptibility to BSE. We investigated 301 samples from healthy cattle of various Slovak breeds and 24 samples obtained from tissues of BSE-affected cattle in Slovakia. We examined the PrP gene for the 23-bp indel polymorphism in the putative promoter region, 12-bp indel polymorphism in the first intron of the PrP gene, variations in number of octapeptide repeat units, and presence of the silent AAC>AAT transition in codon 192 within the protein-coding region of the PrP gene. Altogether we found 23 different genotypes in the group of healthy cattle and only 6 genotypes in the group of BSE-affected cattle. Comparison of homozygotes for the 23-bp insertion and heterozygotes showed significant differences (P < 0.05) in genotype distribution between the examined groups. Thereby the homozygous insertion genotype at the 23-bp indel polymorphism site in the promoter region of the prion protein gene seems to have a protective effect against BSE.

Evaluation of vaccine-induced maternal immunity against classical swine fever.

The vaccine-induced maternal immunity against classical swine fever (CSF) was investigated in this study. Eight sows were vaccinated with the Chinese strain of classical swine fever virus (CSFV). The length of time between vaccination and farrowing was 167-217 days. Milk samples from the front, middle and back udder sections and blood samples were taken from the sows on days 3 and 14 after farrowing. Blood samples were obtained from the piglets at the age of 3, 6 and 10 weeks. The antibody level of the milk was examined by ELISA, and that of blood samples by the virus neutralization (VN) test as well. In all 3-week-old piglets and in 80% of the 6-week-old animals the neutralizing antibody level reached the titre of 1:40. In none of the 10-week-old piglets did the titre exceed the value of 1:20, but in about 25% of the piglets it reached 1:20; the half of these piglets came from two litters. In none of the piglets did the antibody level reach the negative threshold in the ELISA test during the study. No significant differences were found between the udder sections in milk antibody level by ELISA.

Genetic analysis of classical swine fever virus isolates from a small geographic area.

Twenty-eight field CSFV samples were isolated from outbreaks of CSF which have occurred in three small geographic areas in Slovakia in the period of December 1993-November 1994. All the organ homogenates were positive by virus isolation and RT-PCR assay using general pestivirus 324/326 primers selected from 5'-noncoding (5'-NC) genomic region. Specific discrimination of CSFV was confirmed by the cleavage of amplicons using Bgl1 and Ava 1. Four viral isolates (A, B, C, E) were selected for a comparative sequencing study. Sequencing of amplicons in the 5'-NC, gp55 (E2), p54 (NS2) and NS5B genomic regions revealed that A, B isolates (originated from SR geographic area) were the same but different from identical C (NR geographic area) and E (ER geographic area) isolates. Results of molecular-genetic study were very well supported with epizootological data. All CSFV isolates from Slovakia phylogenetically fell into the group of recent European isolates clearly separated from old European and American strains.