Aim of the study: In view of the frequent occurrence of immunosuppression in pigeons, which is a consequence of viral infections, studies with the use of a synthetic immunomodulator (methisoprinol) were undertaken to evaluate its impact on the course of an experimental infection with PPMV-1. The aim of the study was to determine the usefulness of methisoprinol for the treatment or prophylaxis of viral infections in pigeons. Materials and Methods: Three groups of 5-week-old pigeons, with 15 birds in each, were used in the experiment. Before the experiment, the birds were tested for the presence of antibodies specific to paramyxovirus, and their sensitivity to PPMV-1 infection was evaluated. The virus had been cultured earlier on SPF chicken embryos of 9-12 days. The pigeons from all three groups were infected intravenously with aparamyxovirus suspension (strain APMV-1/ pigeon/Poland/AR3/95 obtained from the Veterinary Institute in Puławy) at a concentration of LD50 10-7 in 0.1 ml at a dose of 0.1 ml/pigeon. The birds in the experimental groups (B1 and B2) were immunomodulated with methisoprinol administered at a dose of 200 mg/1 kg of body weight. The immunomodulator was administered by intramuscular injection for 3 successive days before (group B1) or three successive days after (group B2) the experimental infection. Pigeons in group K (used as a control) were given water by intramuscular injection for 3 days before and 3 days after infection. On days 4, 8, and 12 after infection, 5 birds from each group were euthanized, and sections of internal organs (lung, kidney, brain), as well as cloacal swabs, were collected to detect viral RNA by the RT-PCR method. Results and discussion: Symptoms were recorded from the first day after infection. Neurological symptoms occurred in birds from all groups: in 100% of pigeons from groups B1 and K, and in 80% of pigeons from group B2. Deaths of birds occurred from day 5 after infection in group B1. In the other groups, deaths were observed from day 6 after infection. The total mortality of the infected birds ranged from 70% (group B2) to 100% (groups B1 and K). The resolution of symptoms was observed from day 6 after infection in pigeons from group B2. During molecular examination, it was noted that the highest number of positive samples (presence of PPMV-1) on each day of the investigation was obtained from brain samples and cloacal swabs. The highest number of positive results in kidney samples was obtained from groups B1 and K on day 4 after infection. On the successive days of the investigation the percentage of positive samples increased to 100 in birds from all groups except group B2. Based On the basis of the results of the present study, it can be concluded that methisoprinol, used at a dose of 200 mg/kg of body weight after infection, has antiviral activity, manifested by a slower development of paramyxovirosis in pigeons infected intravenously with PPMV-1. Therefore, the administration of methisoprinol to naturally infected and diseased birds may be useful in the treatment of viral diseases.
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