Experimental Coinfection of Chicken Anemia Virus and Mycoplasma gallisepticum Vaccine Strains in Broiler Chicks
By CF Prezotto, SY Marin,TS Araújo, FO Barbosa, PR Barrios, AM Gomes, AP Peconick, M Resende, RV Sousa, NRS Martins
This study aimed at determining the clinical and pathological effects of the coinfection of young SPF chickens with chicken anemia virus (CAV) and Mycoplasma gallisepticum (MG) vaccine strains. The clinical signs, gross and microscopic lesions were determined after the experimental coinfection broilers with a CAV genotype 1 vaccine strain given intraperitoneally on the first day of age and a MG F-strain vaccine given intranasally on the 8th day of age. The experimental groups included the negative control (group 1), a group infected with the MG F-strain vaccine (group 2), and a group coinfected with CAV and MG vaccines (group 3). Chicks were examined clinically and post mortem at 23 days of age, and gross and microscopic lesions of the trachea, thymus, and air sacs were compared among treatments (Kruskal-Wallis test). Infections were confirmed by PCR for specific genetic fragments of each agent in the target tissues. Mortality was only observed in chicks on group 3, with two deaths and more severe lesions in the trachea, thymus and air sacs compared with groups 1 and 2 (p< 0.01). Dead chicks presented reduced thymus and spleen size, hemorrhagic trachea with catarrhal exudate and partial obstruction, pericarditis, catarrhal airsacculitis, lungs with liquid and ascites. The surviving chicks in group 3 showed more severe respiratory changes than those in group 2, in addition to thymus and spleen size reduction. Results indicate the adverse effects of the coinfection of young chickens with MG F-strain and CAV genotype 1 vaccines.
Mycoplasma gallisepticum (MG) may cause increased mortality, reduction in weight gain, a higher rate of condemnations in the processing plant due to airsacculitis in broilers, and reduction in egg production in layers, which result in very significant losses to the poultry industry (Evans et al., 2005; Ley, 2003; Lütticke, 1997; Nascimento and Pereira, 2009; Yashpal et al., 2004). However, MG may cause a much more serious disease if associated with other respiratory agents, such as other bacteria and viruses (Yashpal et al., 2004; Couto et al. , 2015). The chicken anemia virus (CAV) is an immunosuppressive agent that may predispose chickens to primary and secondary infections, mainly by affecting the bone marrow and thymus, thus compromising the immune response and health of poultry (Brentano, 2009; Toro et al., 2009; Gallardo et al., 2012; Silveira et al. , 2013).
Important poultry-producing regions are densely concentrated, and occasionally farms have poor biosecurity. Live vaccines, including those against CAV and MG strains, are commercially available and have been used for the prevention of diseases. This study aimed at evaluating the clinical signs and the gross and microscopic lesions in young chickens experimentally coinfected with commercial vaccine strains of MG and CAV. For this purpose, chicks were administered with the F strain of Mycoplasma gallisepticum (MG) in coinfection or not with a chicken infectious anemia virus (CAV) genotype 1 vaccine strain.
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Source: Rev. Bras. Cienc. Avic. vol.18 no.3 Campinas July/Sept. 2016. http://dx.doi.org/10.1590/1806-9061-2016-0235