The infection caused by bovine diarrhoea virus (BVDV) generally causes mild clinical symptoms in immunocompetent cattle. A severe disease can be observed mainly in young animals. The infection of pregnant animals is especially important because the virus may invade the fetus. Due to an infection caused by a non-cytopathogenic BVDV strain persistently infected, immunotolerant animals may be born wich are consistently viraemic and can shed the virus during the whole lifetime. Such an infection can not be caused by a cytopathogenic biotype. Developmental disorders of central nervous system and eyes may develop in case of an infection between the 90th and 150th days of pregnancy. The fetus is able to produce antibiodies against the virus during the second half of pregnancy. Venereal infections are also important. Bulls - in case of an acute infection with lower titres and for a shorter period, however in case of persistent infections persistently and with a higher titre - shed the virus. The virus in the semen may cause seroconversion, return to heat, embryonic disorders, etc. in the infected animals and the animals born can be persistently infected. Mucosal disease (MD) may develop in animals persistently infected with a non-cytopathogenic BVDV during the fetal life - between the 40th and 120th days - when the animals are super infected with a cytopathogenic BVDV later on. When the super infecting virus has a homologous antigenic structure a disease develops with low morbidity but high mortality. When the antigenic structure of the super infecting virus is partly heterologous, due to the antibodies produced against it the super infecting virus disappear from the blood. MD develops weeks or months after the super infection. MD does not develop after a super infection with homologous or heterologous cytopathogenic BVDV, even antibodies are produced against the heterologous virus. Diagnosis of the diseases caused by BVDV is based on the clinical symptoms, pathological and histological alterations and results of laboratory investigations. Demonstration of the virus, virus antigen or nucleic acid are used for the laboratory diagnosis of BVDV.
|Number of pages||9|
|Journal||Magyar Allatorvosok Lapja|
|Publication status||Published - dec. 1 1998|
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