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Kolb, Anna-Katharina (2009): Verlauf der mittleren Antikörperkonzentration von Haemophilus parasuis, Mycoplasma hyorhinis, PRRSV und PCV2. Dissertation, LMU München: Faculty of Veterinary Medicine
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Abstract

The aim of this study was to describe the serological course of H. parasuis in three farms during a present coinfection with M. hyorhinis, PRRSV and PCV2. The examinations occurred in three breeding farms and their complementary finishing units. A clinical examination and blood sampling was done in regular two-week intervals of animals from the 1st to the 11th week of life and the same was done with animals between the 14th and 22nd week of life but in four-week intervals. Furthermore, blood samples were taken from sows in the first week after farrowing. The detection of antibodies against H. parasuis, M. hyorhinis, PCV2 and PRRSV was done using ELISA. The increased lameness that was seen in farm 1 from the 14th week of life was due to H. parasuis because of a simultaneous occurrence in the rise of the antibody titer and the seroprevalence for H. parasuis. In the second and third farm, H. parasuis probably played a role as a cofactor in the porcine respiratory disease complex (PRDC). A correspondent increase in the age of the animals and the clinical scores could be detected for all three farms. In addition, an increase in the occurrence of multiple infections was observed during the finishing period. Double and single infections were present in most of the examined animals, and PCV2 was involved in all cases. Antibodies against PCV2 were found in all animals at the end of the finishing period. A significant association was detected for the mutual occurrence of H. parasuis and PCV2 in the 18th week of life. A synergism of both agents cannot be fully ascertained because of the time at which the significant mutual detection occurred. The tendency of both PCV2 and PRRSV to mutually occur was observed but a significant association was not found. A significant correlation between the antibodies of the sows and their piglets was found for all examined agents in the first week of life. In the first week of life, identical antibody titers for H. parasuis were measured in the sows and piglets and the PRRSV and PCV2 antibody titers of the piglets were even higher in the first week of life. The drop in the antibody titer in the following week of life depended on the specific agent and the starting antibody titer of the piglet in the first week of life. This fall was prolonged if the antibody titer in the first week of life was very high. High antibody titers in the sows are a prerequisite for a good passive immunity in piglets in the first week of life. The maternal immunity against H. parasuis, PRRSV and PCV2 can be improved by sow vaccination. No uniform seroconversion time was found for the four examined agents in the three farms. Thus the seroconversion of H. parasuis and M. hyorhinis began in the ninth and eleventh week of life; PCV2 began in the 9th, 11th, 18th week and PRRSV in the 14th and 18th week of life. Therefore a farm specific serological profile for every relevant agent should be done. In farm 2 and also in farm 3, a mutual seroconversion time in the 9th and 11th week of life was detected for H. parasuis, M. hyorhinis and PCV2. This points to a mutual infection time for these three agents at different times in the respective farms. A simultaneous seroconversion for PRRSV and PCV2 in the 18th week of life was observed in farm 1. Mutual agent influence is possible for H. parasuis, M. hyorhinis and PCV2 and probable for PRRSV and PCV2. The present study demonstrates the difficulty of the interpretation of serological profiles and indicates that an appropriate interpretation of the serological profile can only be done when the clinical signs are also taken into consideration.