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The pathogenesis of mucosal disease
1National Animal Disease Center, United States Department of Agriculture, Agricultural Research Service, Ames, Iowa, USA.
Abstract:
The pathogenesis of MD is complex and remains somewhat obscure. Clearly, the disease occurs in cattle persistently infected with noncytopathic BVDV. It also is clear that cytopathic BVDV is associated with MD, and is the likely trigger of the cellular destruction that leads to clinical disease. Whether the cellular destruction is attributable directly to the cytopathic virus, or occurs as the result of other mechanisms remains unclear. Although immunotolerance is involved in MD, it can be broken and its role in the disease process needs further research. It is logical, and well supported by research, that noncytopathic BVDV is the source of cytopathic BVDV. It also is likely that most outbreaks of MD are the result of a spontaneous mutation of noncytopathic to cytopathic virus within a PI animal. Antigenic homology between viruses would be expected in those outbreaks. MD also occurs when PI cattle are exposed with a cytopathic BVDV that is antigenically heterologous with the resident noncytopathic BVDV. In those situations, it may be a race between the cytopathic virus and the immune system.
Insights
Mucosal disease (MD) in cattle is complex, often triggered by cytopathic Bovine viral diarrhea virus (BVDV) in persistently infected animals. Further research is needed to fully understand the mechanisms of cellular destruction and immunotolerance in MD pathogenesis.
Area of Science:
- Veterinary Pathology
- Virology
- Immunology
Background:
- Mucosal disease (MD) pathogenesis in cattle is complex and not fully understood.
- Persistent infection with noncytopathic Bovine viral diarrhea virus (BVDV) is a prerequisite for MD.
- Cytopathic BVDV is associated with MD and likely triggers the cellular destruction leading to clinical signs.
Purpose of the Study:
- To elucidate the complex pathogenesis of Mucosal Disease (MD) in cattle.
- To investigate the role of cytopathic and noncytopathic BVDV in disease development.
- To explore the mechanisms of cellular destruction and the involvement of immunotolerance.
Main Methods:
- Analysis of existing research on MD pathogenesis.
- Review of viral characteristics (cytopathic vs. noncytopathic BVDV).
- Examination of the role of persistent infection and immune tolerance.
Main Results:
- Cytopathic BVDV is the likely trigger for cellular destruction in MD.
- Noncytopathic BVDV is the probable source of cytopathic BVDV through spontaneous mutation.
- MD outbreaks can result from spontaneous mutation or exposure to heterologous cytopathic BVDV in persistently infected cattle.
Conclusions:
- MD pathogenesis involves complex interactions between noncytopathic and cytopathic BVDV.
- Spontaneous mutation of noncytopathic to cytopathic BVDV within persistently infected animals is a likely cause of MD outbreaks.
- Further research is required to clarify the precise mechanisms of cellular destruction and the role of immunotolerance in MD.