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This page explains the viral cause of Myxomatosis and the associated clinical signs, pathology and pathogenesis, treatment, control and prognosis.
This page explains the viral cause of Myxomatosis and the associated clinical signs, pathology and pathogenesis, treatment, control and prognosis.
===Myxoma virus===
===Myxoma virus===
====Hosts====
*Causes Myxomatosis in rabbits
*Causes Myxomatosis in rabbits
====Transmission====
*Infectious myxomatosis is highly contagious and transmitted by direct or indirect contact with ocular or skin discharges or by mechanical vectors.
*Infectious myxomatosis is highly contagious and transmitted by direct or indirect contact with ocular or skin discharges or by mechanical vectors.
*Arthropod vectors such as mosquitoes and fleas provide the principal means of transmission.
*Arthropod vectors such as mosquitoes and fleas provide the principal means of transmission.
*High ambient environmental temperatures are associated with increased survival of infected animals. Some authors consider the California strains of the virus (California rabbit fibroma virus) as distinct from the myxoma virus, while others feel that the antigenic differences do not justify the separate distinction.
*High ambient environmental temperatures are associated with increased survival of infected animals. Some authors consider the California strains of the virus (California rabbit fibroma virus) as distinct from the myxoma virus, while others feel that the antigenic differences do not justify the separate distinction.
*Several proteins encoded by the virus are immunosubversive in that they mimic host ligands or regulators (virokines) or are homologues of cellular cytokine receptors (viroceptors)
*Several proteins encoded by the virus are immunosubversive in that they mimic host ligands or regulators (virokines) or are homologues of cellular cytokine receptors (viroceptors)
====Antigenicity====
*Myxomatosis is enzootic in rabbits of the genus Sylvilagus in both South and North America and in wild rabbits of the genus Oryctolagus in South America, Europe, and Australia
*Following introduction into Europe and Australia, genetic modification of the myxoma virus produced markedly attenuated strains that replaced the virulent virus as the dominant virus strain
===Clinical signs===
===Clinical signs===
*The skin tumors result from proliferation of undifferentiated mesenchymal cells which become large stellate cells (myxoma cells). These cells may contain intracytoplasmic eosinophilic inclusions. These cells lie in a homogeneous matrix of mucinous material interspersed with capillaries and inflammatory cells. Endothelial proliferation with narrowing of the lumen and extrusion of stellate "myxoma" cells has been described.
*The skin tumors result from proliferation of undifferentiated mesenchymal cells which become large stellate cells (myxoma cells). These cells may contain intracytoplasmic eosinophilic inclusions. These cells lie in a homogeneous matrix of mucinous material interspersed with capillaries and inflammatory cells. Endothelial proliferation with narrowing of the lumen and extrusion of stellate "myxoma" cells has been described.
*Epithelial cells overlying the tumor may show hyperplasia or degeneration, or may appear normal. Epithelial proliferation is characterized by ballooning of cells in the stratum granulosum and hyperkeratosis. Epithelial vesiculation progresses to crust formation. Large, eosinophilic, intracytoplasmic inclusions are especially prominent in the stratum spinosum. Lesions in other organs include cellular proliferation of alveolar epithelium and the reticulum cells of [[Lymph Nodes - Anatomy & Physiology|lymph nodes]] and [[Spleen - Anatomy & Physiology|spleen]]. Focal hemorrhage may be present in skin, kidneys, lymph nodes, testes, heart, stomach, and intestinal walls. Myxoma cells may be present in [[Lymph Nodes - Anatomy & Physiology|lymph nodes]], [[Bone Marrow - Anatomy & Physiology|bone marrow]], uterus, ovaries, testes, and lungs.
*Epithelial cells overlying the tumor may show hyperplasia or degeneration, or may appear normal. Epithelial proliferation is characterized by ballooning of cells in the stratum granulosum and hyperkeratosis. Epithelial vesiculation progresses to crust formation. Large, eosinophilic, intracytoplasmic inclusions are especially prominent in the stratum spinosum. Lesions in other organs include cellular proliferation of alveolar epithelium and the reticulum cells of [[Lymph Nodes - Anatomy & Physiology|lymph nodes]] and [[Spleen - Anatomy & Physiology|spleen]]. Focal hemorrhage may be present in skin, kidneys, lymph nodes, testes, heart, stomach, and intestinal walls. Myxoma cells may be present in [[Lymph Nodes - Anatomy & Physiology|lymph nodes]], [[Bone Marrow - Anatomy & Physiology|bone marrow]], uterus, ovaries, testes, and lungs.