The dissertation is devoted to the peculiarities of non-specific immunity in chickens infected with Marek’s disease virus isolates: Borky 31/12 (m pathotype), Merepha 2004 (vv pathotype), Bolshevik (m pathotype), AlexandrovskPF (v pathotype), and also in vaccinated chickens (‘Cultural Bivalent Vaccine against Marek’s Disease’ and ‘Recombinant DNA vaccine «DNA VAC MDV») with the further inoculation by the JM strain (vv pathotype).
The obtained results extend the understanding of the mechanisms of the Marek’s disease virus action in chicken and can be taken into account during the development of preventive measures. The research has proved that the Marek’s disease virus has immunosuppressive influence, contributes to the development of endogenous intoxication degrading the balance in the work of the lipid proxidation-antioxidant system, which is confirmed by hematological, immune-biochemical and pathological studies.
The obtained results showed that Marek’s disease virus isolates Merepha 2004, JM and Alexandrovsk PF (vv and v pathotype) provoke clinical manifestations of acute form of Marek’s disease from the 42nd day. At the intersection there were observed dystrophic processes and nodules of light gray color in the spleen, liver, kidneys, atrophy in bursa of Fabricius, increased testicles and ovaries, hypertrophy of the heart muscle.
In chicks infected with Marek’s disease virus isolates Borky 31/12 and Bolshevik (moderately virulent (m patotype)) starting from the 50th day of the experiment, the classical form of Marek’s disease with a weak manifestation of clinical signs (lameness, paralysis of limbs, wings, neck) was recorded. During the autopsy of the chickens, thickening of the walls of the glandular stomach, degenerative processes in the spleen and the liver, hemorrhages in the thymus, necrotic changes in the genital organs, kidney enlargement and hypertrophy of the heart muscle were observed.
Our studies have shown that changes in hematological parameters in chickens that were infected with Marek’s disease virus isolates Merepha 2004 and Alexandrovsk PF isolates begin earlier (from the 30th day) than in chickens that were infected with Marek’s disease virus isolates Borky 31/12 and Bolshevik (from the 50th day).
Blood protein profile has been studied: level of α globulins increased up to 42.2% (p ˂ 0.05)at the beginning of the experiments, β globulins — up to 58.5% (p ˂ 0.05), and on the 50th day of the trial — γ globulins up to 72.2% (p ˂ 0.05) (in chickens infected with isolates Merepha 2004 and AlexandrovskPF). In chickens infected with isolates Borky 31/12 and Bolshevik, the increase of γ globulins up to 75.0% (p ˂ 0.05) was observed at the 50th day of the experiment, and α globulins up to 60.8% (p ˂ 0.05), β globulins — up to 65,1% (p ˂ 0.05), starting from the 70th day of the experiment.
In all birds, especially in the groups of birds infected with Marek’s disease virus isolates Borky 31/12 and Bolshevik, the number of Ig G and Ig M increased simultaneously at the beginning of the experiment to 39.7% (p ˂ 0.05) and 64.4% (p ˂ 0.05), as well as there was noted an increase in seromucoids and circulating immune complexes up to 36.3%.
The study of the condition of endogenous intoxication showed its severity from the second half of the study, which is due to excessive accumulation of protein exchange products, which in turn indicate a functional impairment of the hepatoperenal system.
The conducted studies revealed excessive formation of free radicals, namely in chickens infected with isolates Borky 31/12 and Merepha 2004, which leads to decrease in catalase activity to 15.0%. Inhibition of catalase activity at the last observation period indicates the accumulation of LPO products, which in turn leads to deformation of cell membranes primarily in liver and kidneys (the level of MDA in these organs is increased to 43.0%). Depletion of the antioxidant potential is proved by the studied parameters: carotenoids, vitamin A and vitamin E. During the whole trial, the decrease in the level of vitamin A was recorded up to 65.5% (p ˂ 0.05), carotene up to 59.7% (p ˂ 0.05), vitamin E up to 50.9% (p ˂ 0.05) in serum of chickens of all infected groups.
During the study of the effect of the high-virulent strain of Marek’s disease virus JM on the body of vaccinated chickens (with the ‘Cultural Bivalent Vaccine against Marek’s Disease’ and ‘DNA VAC MDV’), the direction of changes in the proteinogram in chicken was noted, which indicates the beginning of the development of immune responses, but starting from the 70th day — indicates the beginning of the development of the toxic effect of the JM strain of Marek’s disease virus on the liver of chickens from vaccinated group. The dynamics of the concentration of class G immunoglobulins in the serum of chickens vaccinated with the bivalent vaccine and DNA vaccine was similar with the highest level on the 70th day of the experiment by 40.0% (p ˂ 0.05) and on the 68th da
