Serological monitoring of ornitobacteriosis in broilers in South Banat district

Ornithobacterium rhinotracheale is a relatively recently discovered bacterium and its role in the pathology of avian respiratory infections has not yet been clarified. Since there was no data relating to the prevalence of this infection in Serbia at the time of carrying out our investigations, we decided to explore the prevalence of the infection in broilers and its influence on clinical manifestations at the selected apizootiological area with developed poultry industry. A total of 430 blood samples from 26 flocks of broilers of different ages, from five municipalities were taken for examination. The serum samples were tested by ELISA for the presence of specific antibodies to the agent. Epizootiological investigation was carried out based on the results obtained with serological testing and epizootiological data, collected from the farms. The data were analyzed statistically to identify association between the infection and manifestation of clinical symptoms by Fisher’s exact test. Seropositive chickens were detected in 16 out of 26 examined broiler flocks at the age of 3 to 56 days. The percentage of seropositive samples per flock was 5-30%. The titer values of specific antibodies ranged from 946 to 6886. Serological response to O. rhinotracheale was evidenced in five flocks which had clinical symptoms in the form of respiratory tract disorders or stunting. However, specific antibodies against the agent were discovered in 11 flocks which did not show clinical symptoms. Statistical analysis revealed no association between the presence of infection and the appearance of clinical symptoms (p = 0.1213). The results are in agreement with those of other authors who investigated the prevalence of this infection and its manifestations in other countries. The present investigation determined indirectly, serologically a presence of O. rhinotracheale in the majority of examined broiler flocks (61,54%) and a small average number of individual seropositive chickens per flock - 10 % of all examined samples. Although O. rhinotracheale is wide-spread in intensive broiler production in South Banat its presence does not always lead to clinical manifestation of respiratory tract disorders. Seropositive chickens are detected in the first week of life, which indicates the presence of maternal antibodies. Presence of antibodies as the response of organism to the natural infection is detected in chickens after four weeks of age.