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Palm, Katrin (2016): Nachweis spezifischer Antikörper gegen Borrelia burgdorferi in equinen Serumproben aus dem Bayerischen Haupt- und Landgestüt Schwaiganger unter Berücksichtigung aktueller Kriterien der Diagnostik. Dissertation, LMU München: Tierärztliche Fakultät
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Abstract

It is widely known that horses mainly living on meadows in endemic regions are exposed to a high infection risk with Borrelia burgdorferi sensu lato. Although most cases of equine borrelia infection seem to proceed inapparent, there are numerous reports of cases of borrelia-infection associated illnesses in horses with direct confirmation of B. burgdorferi sensu lato. The clinical signs described in literature are versatile and there is no homogeneous disease pattern defined for horses. The more important it is to have a reliable serological verification of pathogenic agents as soon as there is the suspicion of Lyme disease. Huge problems result of the still deficient standardisation of examination methods. The superior target of this dissertation was the revision of the diagnostic suitability of an immunoblot of Mikrogen and an ELISA of Virotech, both of which had been used in a preliminary paper and provided contradictory results. As the current recommendation of serological clinical diagnostics of Lyme disease allots a two-step test, both examination systems mentioned above were chosen. For this purpose, a subgroup, whose blood samples had already been tested with those systems in 2007, was again tested with another immunoblot of Virotech. In order to be able to make a declaration concerning the diagnostic value the results were confronted and compared. The analysed blood samples came from horses of the Bavarian “Haupt- und Landgestüt Schwaiganger“ and were taken in the period between July 2005 to June 2006 in intervals of four to six weeks. The via PCR estimated prevalence of Borrelia burgdorferi in the ticks of the stud’s grounds amounted to 18 %. The samples of the fifth and sixth blood withdrawal of the preliminary paper were chosen for the subgroup as most samples had been tested concordantly with immunoblot as well as ELISA V at these dates. 96 samples of the fifth blood withdrawal, subsequently to be referred to as blood withdrawal A were again tested in 2015. 73 samples of the sixth blood withdrawal, subsequently to be referred to as blood withdrawal B, were chosen from another testing. All age groups of the formerly tested horses were included in the subgroup. 11 foals were chosen. Due to the small number of animals the samples of all eight blood withdrawals could be tested. At first sight, the comparison of the results of the Virotech-blot and the Mikrogen-blot of all horses showed that a distinct majority of the samples of the Mikrogen-blot could be rated as positive. In the blood withdrawal A only 2 % of the horses reacted positively on the Virotech-blot, compared to 64 % on the Mikrogen-blot. In the blood withdrawal B there was no positive horse to be listed on the Virotech-blot whereas there were again 64 % on the Mikrogen-blot. Out of 96 samples of blood withdrawal A there were 33 correlating results of both tests. Out of 73 samples of blood withdrawl B there were only 22 conformities. The comparison of the results of both blots with sera of the foals provided a similar pattern. While no sample reacted positively on the Virotech-blot, 10 % to 78 % of the tested horses were tested positively on the Mikrogen blot between the 33rd and 328th day after the first withdrawal. Accordingly, there were only few matches of the two blots. The comparing examination of the banding pattern of three exemplarily chosen horses showed that there were no positively rated bands on the part of the Virotech-blot whereas there were various bands to be positively rated on the part of the Mikrogen-blot whose control strips all received the attribute “positive”. Concerning the three exemplarily chosen foals there again was no control strip rated “posi-tive” on the Virotech-blot. Only five of 44 evaluated control strips of the Virotech-blot were rated as “marginal”. Compared to Virotech, four control strips were rated as “marginal” and fourteen as “positive” on the Mikrotech-blot. The comparison of the results of the Virotech-blot and Virotech-ELISA of all horses, including the foals, showed that on Virtoech-ELISA 195 out of 222 samples and on the Virotech-blot 184 samples were rated negatively which means that 11 samples could not be confirmed. 13 samples reacted positively on ELISA, two on the blot. The label “marginal” was given to 14 ELISA samples and 36 of the blot. The comparing observation revealed a larger consensus between the results of Virotech-blot and Virotech-Elisa than between Virotech-blot and Mikrogen-blot. The results of the ReclomBlot Borrelia IgG of Mikrogen can be rated as unreliable. The excessive amount of positively adjudged samples aberrates from the diagnostic reality. Due to the results of this work the diagnostic suitability of the Borrelia Veterinär plus OspA Line IgG Line Immunoblot and the Borrelia burgdorferi Veterinär ELISA of Sekisui Virotech could be confirmed. Both testing systems approve as suitable diagnostic instruments to proof Lyme disease in the recommended two-step test.