Abstract
It is clear that currently the question of study of the pathological changes in the respiratory tract of chickens due to the impact of the fowlpox virus remains relevant, as the pathogenesis of nutritional deficiency, the presence of mycotoxins or the papilloma virus are characterized by the same clinical manifestations. We analyzed 88 chickens, naturally infected with the fowlpox virus, using clinical and immunohistochemical methods of investigation. Among all species of birds, we studied only chickens, data on which were collected for five years from veterinary clinics. The investigation revealed lesions basically characterized by the presence of changes in the typical structure of the chicken’s respiratory tract. As a result, we found clear criteria for the pathological process in the respiratory tract of chickens, which are typical for fowlpox. Thus, we discovered respiratory tract obstruction, as well as many intracytoplasmic pale eosinophilic inclusions in hyperplastic cells. We found an accumulation of mononuclear cells consisting mainly of macrophages, lymphocytes, plasma and mononuclear cells inside the mucous and muscle membranes. Bronchial lumens were blocked by necrotic and desquamated epithelial cells, red blood cells, bacterial colonies and amorphous eosinophilic material. We found accumulations of lymphocytes and macrophages in the parenchyma of the lungs. The hyperplastic epithelial cells reacted immunohistochemically with antibodies against the fowlpox virus in the respiratory tract. Immunoreaction occurred mainly in the cytoplasm of infected cells, inclusions, and necrotic and desquamated cells. The study proved immunohistochemical methods of investigation can be a useful additional tool for establishing a final diagnosis, especially in acute and subacute phases of the disease. The following respiratory signs were observed in severe cases of fowlpox: damage to the lungs in 33 cases (46.5%), parabronchium – 20 (28.2%), parabronchial connective tissue – 8 (11.3%), and mucous membrane of the larynx and trachea – 10 (14.1%). In mild and moderate cases of fowlpox, the following respiratory signs were observed: hyperemia and thickening of the mucous membrane of the trachea – 14 (82.4%), as well as hyperemia in the nasal conchae and paranasal sinuses – 3 (17.7%). In the future, it will be necessary to conduct deeper studies to detect pathological manifestations of this disease, not only in the respiratory tract, but also in other organs and systems of chickens.
Highlights
According to the literature, fowlpox is a disease that is widespread all over the world and is caused by the virus of the family Poxviridae, the genus Avipoxvirus (Fauquet, 2005; Tripathy, 2000)
Our study revealed that it was the epithelium of the lower respiratory tract that was significantly affected in the chickens, which was characterized by hyperplasia of epithelial cells in the trachea and bronchi, and by accumulation of mononuclear cells in the underlying layers, tissue damage near the bronchi, which confirms the severe degree of this infection
It has been reported that Avipoxvirus is caused by symptoms such as the appearance of pustules in the skin of birds, as well as signs of disease similar to diphtheria, which may include characteristic necrotic lesions covering the oral cavity and upper respiratory tract (Zhao et al, 2014), which may be due to the fact that, like other avian viruses, the fowlpox virus can be transmitted through vectors mechanically, for example, through mosquitoes
Summary
Fowlpox is a disease that is widespread all over the world and is caused by the virus of the family Poxviridae, the genus Avipoxvirus (Fauquet, 2005; Tripathy, 2000). Fowlpox is characterized by large economic losses, which is mainly due to the decline in egg production and excess mortality among birds (Ali et al, 2016; Bande et al, 2016). It has been reported that fowlpox is a slowly spreading viral infection which is often characterized by proliferative skin lesions, and by changes in the upper gastrointestinal tract, respiratory tract (diphtheria form) (Singh et al, 1987; Docherty et al, 1991; Fallavena et al, 1993; Gortázar et al, 2002; Cavanagh, 2007; Bande et al, 2016)
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