Quality of broilers infected with autochthonous MGA strain, alone or in combination with Infectious Bronchitis Virus (IBV) vaccine
ABSTRACT. da Silva C.C., dos Santos F.F., Faria T.S., José D.S., Tortelly R., Abreu D.L. da C., do Nascimento E.R., Machado L. dos S., Soares M.V. & Pereira V.L.A. [Quality of broilers infected with autochthonous MGA strain, alone or in combination with Infectious Bronchitis Virus (IBV) vaccine.] Qualidade de frangos de corte infectados com Mycoplasma gallinarum isoladamente ou em combinação com o vírus vacinal da Bronquite Infecciosa das Galinhas. Revista Brasileira de Medicina Veterinária, 38(4):420-430, 2016. Departamento de Saúde Coletiva, Faculdade de Veterinária, Universidade Federal Fluminense, Rua Vital Brazil Filho, 64, Niterói, RJ 24230-340, Brasil. E-mail: firstname.lastname@example.org
Brazil is the world’s largest exporter and third largest producer of poultry meat. Advances in management, biosecurity and genetics have contributed to the increase in productivity of the poultry industry, at the same time the pronounced production increased the risk of spreading respiratory diseases, such as avian mycoplasmosis and Infectious Bronchitis. Mycoplasma gallisepticum (MG), Mycoplasma synoviae (MS) and Mycoplasma meleagridis (MM) are recognized as indisputable pathogens for the poultry industry, however Mycoplasma gallinarum (MGA) has been considered commensal. The aim of this study was to evaluate the quality of broilers infected with autochthonous MGA strain, alone or in combination with Infectious Bronchitis Virus (IBV) vaccine. There were raised 96 broiler chicks since one-day-old, Cobb line, mycoplasma free. They were separated in four groups of 24 birds kept in isolation units: Group 1 (G1), uninfected and unvaccinated; Group 2 (G2), infected with autochthonous MGA strain; Group 3 (G3), vaccinated with commercial IBV strain H120 (Bio-bronk-vet ®, Biovet, SP); Group 4 (G4), infected with MGA and vaccinated with commercial IBV. The infection was monitored by MGA PCR and IBV vaccination was confirmed by RT-PCR. The feed intake record was made for the period of the experiment. Weekly, four broilers were randomly taken from each group, individually weighed and submitted for blood sampling and the necropsy for obtaining samples for laboratory analysis. It was collected fragments of trachea, lungs, air sacs, liver, heart, chest muscles, kidneys and digestive tract, fixedin 10% formalin for histopathology. Tracheas scraping samples were pooled for each group and subjected to detection of MGA, MG, MS by isolation and PCR and IBV detection by RT-PCR. Serum samples, obtained from blood, were subjected to ELISA for MG, MS and IBV. Weight gain was calculated by weight mean divided for the number of days old of the birds. Feed intake between the groups was similar up to 42 days. The differences in final weight mean and weight gain among groups were not significant (ANOVA, p> 0.05). All samples were negative for mycoplasma isolation. By PCR all samples were negative for MG and MS. As for MGA samples were positive in G2 (at the 35th day of age) and G4 (at the 14th, 35th, and 42sd days of age) and negative in G1 and G3. By RT-PCR, the samples were positive in groups vaccinated against IBV in G3 (at the seventh and 42sd days old) and G4 (seventh, 14th, 35th and 42sd days old). By ELISA, all groups were negative for MG and MS and for IBV, had titles in the first, credited to maternal antibodies, which decreased with seven days and were negative with 14 days of age in all groups. By necropsy, observed lesions were not noteworthyin G1 and G3. In the other groups it was observed ascitis, catarrhal exsudate in the trachea, airsacculitis, hydropericardium, pneumonia, synovitis, and pectoral myopathy in variable number of birds between groups and according to age groups. The differences in the frequencies of macroscopic lesions among the groups were significant (Mann-Whitney test, p <0.05). By histopathology, in G2 was observed pneumonia with multiple nodules characteristic peribronchial lymphoid and diameters variables and in G4, was observed vacuolar muscle degeneration accompanied by muscle atrophy and necrosis of the breast, also inflammation associated with focal necrosis in the lung. The MGA alone was not capable of causing apparent disease in broilers infected, although produced pulmonary lesions in the final stage of creation but when associated with BIG vaccine caused lesions amenable to condemnation that may compromise the quality of broilers at slaughter.