Findings of antibodies to Mycoplasma suis on swine farms in Serbia

Abstract

Background: Hemoplasmas are eperythrocytic procaryotes, including Mycoplasma species which were recently transferred from the genera Eperythrozoon and Haemobartonella, based on their similarity of the 16S rRNA sequences, and newly identified hemotropic mycoplasmas. Eperythrozoonosis of pigs is caused by the haemotrophic bacterium M. suis, and the disease has a worldwide distribution. The disease manifests as a severe and often fatal acute febrile icteroanemia, mainly in piglets, pregnant sows before parturition and fattening pigs exposed to stress. The aim of this study was to determine the seroprevalence of IgG to M. suis in swine populations in Serbia, using a Western Blot test with the recombinant protein MSG1. Materials, Methods & Results: Four farms were chosen to represent the main swine-producing geographic regions of Serbia, including South Bačka District (farms 1 and 2), North Bačka District (farm 3) and Branicevo District (farm 4). A total of forty-six clinically healthy pigs, age 8-20 weeks, were included in the study. Blood samples from pigs randomly selected from the four farms were collected by jugular vein puncture into serum vacutainer tubes with clot activator. After clotting at room temperature for 1 h, blood samples were centrifuged at 1500 g, for 15 min at room temperature. Sera were carefully harvested and stored at -20°C until assayed. The sera samples were tested by the Western Blot test with recombinant protein MSG1 (p40). Production of recombinant protein MSG1 (p40), dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting were performed as previously described by Hoelzle. Specific IgG antibodies to MSG1 of M. suis were identified in 20 of the 46 samples tested, giving a total seroprevalence of 43.47%. The M. suis-specific antibody response was detected in pigs from all tested farms, within farm seroprevalences of 54.54% on farm 1; 27.27% on farm 2; 36.36% on farm 3 and 53.84% on farm 4. Discussion: Reports on the prevalence of swine infected with Mycoplasma suis in other countries are rare, but have been communicated for USA, Brazil, Japan, Portugal, China and Germany. Previously published values of the prevalence of the pigs infected with haemoplasmas in Serbia, determined through a microscopic examination of the peripheral blood smear according to Giemsa was 39% and with Acridine orange was 47%. These prevalences are similar to the overall prevalence found in this study (43.47%). In this present study, the prevalence of M. suis in the farm pigs studied in Serbia (43.47%) was higher than the serological evidence of the infection reported in pigs in the USA, Brazil and Japan, but lower than the prevalence in sows in Portugal and China. In this present study, the prevalence of M. suis on the studied pig farms in Serbia (43.47%) was more similar to results obtained in Germany, where M. suis infections were detected in 79 out of 196 pig farms (40.3%) by employing a quantitative real-time LightCycler PCR. Also, M. suis was detected in 36 out of 359 wild German boars (10.03%) with similar methodology. Our seroprevalence of anti-M. suis IgG in farmed pigs is probably higher than that in wild boar because of the conditions of intensive breeding on pig farms, but perhaps this may also be partly due to the different geographic locality, and/or to different analytical methods. This overall determined seroprevalence of 43.47% from a small sample within a relatively small area suggests a significantly higher presence of infection on pig farms in Serbia, and hence, significantly more economic losses in pig production than could be expected based on the worldwide reports of M. suis prevalence.