Many viral diseases are endemic in cattle populations worldwide. The ability of many viruses to cross the placenta and cause abortions and fetal malformations is well understood. There is also significant evidence tha...Many viral diseases are endemic in cattle populations worldwide. The ability of many viruses to cross the placenta and cause abortions and fetal malformations is well understood. There is also significant evidence that viral infections have additional actions in dairy cows, which are reflected in reduced conception rates. These effects are, however, highly dependent on the time at which an individual animal first contracts the disease and are less easy to quantify. This paper reviews the evidence relating to five viruses that can affect fertility, together with their potential mechanisms of action. Acute infection with non-cytopathic bovine viral diarrhea virus (BVDV) in mid-gestation increases abortion rates or causes the birth of persistently infected calves. BVDV infections closer to the time of breeding can have direct effects on the ovaries and uterine endometrium, which cause estrous cycle irregularities and early embryo mortality. Fertility may also be reduced by BVDV-induced immunosuppression, which increases the susceptibility to bacterial infections. Bovine herpesvirus (BHV)-1 is most common in pre-pubertal heifers, and can slow their growth, delay breeding, and increase the age at first calving. Previously infected animals subsequently show reduced fertility. Although this may be associated with lung damage, ovarian lesions have also been reported. Both BHV-1 and BHV-4 remain latent in the host following initial infection and may be reactivated later by stress, for example associated with calving and early lactation. While BHV-4 infection alone may not reduce fertility, it appears to act as a co-factor with established bacterial pathogens such as Escherichia coli and Trueperella pyogenes to promote the development of endometritis and delay uterine repair mechanisms after calving. Both Schmallenberg virus (SBV) and bluetongue virus (BTV) are transmitted by insect vectors and lead to increased abortion rates and congenital malformations.BTV-8 also impairs the development of hatched blastocysts;furthermore, infection around the time of breeding with either virus appears to reduce conception rates. Although the reductions in conception rates are often difficult to quantify, they are nevertheless sufficient to cause economic losses, which help to justify the benefits of vaccination and eradication schemes.展开更多
Objective: To investigate the prevalence of bovine coronavirus(BCo V), bovine rotavirus, and bovine viral diarrhea virus in the feces of normal and diarrheic Korean native calves aged 1-81 days between April and Octob...Objective: To investigate the prevalence of bovine coronavirus(BCo V), bovine rotavirus, and bovine viral diarrhea virus in the feces of normal and diarrheic Korean native calves aged 1-81 days between April and October of 2016 in the Republic of Korea. Methods: Samples were obtained from 50 normal and 93 diarrheic(56 semi-formed, 28 loose, and 9 watery feces) calves in six different regions of northern and southern Korea. These fecal samples were tested for BCo V, bovine rotavirus, and bovine viral diarrhea virus by RT-PCR. Results: Among the three pathogens examined, infection with BCo V was especially prominent in relation to diarrhea among calves aged 1-21 days [odds ratio(OR)=9.3, 95% confidence interval(CI): 1.1-78.9; P=0.02). Infection with BCo V alone(OR=2.9; 95% CI: 1.1-7.6; P=0.03) or coinfection of BCo V with bovine viral diarrhea virus(OR=3.6; 95% CI: 1.0-12.4; P=0.04) was significantly associated with the development of loose feces. Grazing and colostrum intake strongly reduced the occurrence of diarrhea as compared to housed calves(OR=0.2; 95% CI: 0.1-0.4; P=0.00) and calves that had not been fed colostrum(OR=0.2; 95% CI: 0.1-0.7; P=0.02), respectively. Conclusions: The present study suggests that BCo V is involved in calf diarrhea in the Republic of Korea. Therefore, grazing and colostrum intake is recommended for preventing and controlling calf diarrhea caused by BCoV.展开更多
文摘Many viral diseases are endemic in cattle populations worldwide. The ability of many viruses to cross the placenta and cause abortions and fetal malformations is well understood. There is also significant evidence that viral infections have additional actions in dairy cows, which are reflected in reduced conception rates. These effects are, however, highly dependent on the time at which an individual animal first contracts the disease and are less easy to quantify. This paper reviews the evidence relating to five viruses that can affect fertility, together with their potential mechanisms of action. Acute infection with non-cytopathic bovine viral diarrhea virus (BVDV) in mid-gestation increases abortion rates or causes the birth of persistently infected calves. BVDV infections closer to the time of breeding can have direct effects on the ovaries and uterine endometrium, which cause estrous cycle irregularities and early embryo mortality. Fertility may also be reduced by BVDV-induced immunosuppression, which increases the susceptibility to bacterial infections. Bovine herpesvirus (BHV)-1 is most common in pre-pubertal heifers, and can slow their growth, delay breeding, and increase the age at first calving. Previously infected animals subsequently show reduced fertility. Although this may be associated with lung damage, ovarian lesions have also been reported. Both BHV-1 and BHV-4 remain latent in the host following initial infection and may be reactivated later by stress, for example associated with calving and early lactation. While BHV-4 infection alone may not reduce fertility, it appears to act as a co-factor with established bacterial pathogens such as Escherichia coli and Trueperella pyogenes to promote the development of endometritis and delay uterine repair mechanisms after calving. Both Schmallenberg virus (SBV) and bluetongue virus (BTV) are transmitted by insect vectors and lead to increased abortion rates and congenital malformations.BTV-8 also impairs the development of hatched blastocysts;furthermore, infection around the time of breeding with either virus appears to reduce conception rates. Although the reductions in conception rates are often difficult to quantify, they are nevertheless sufficient to cause economic losses, which help to justify the benefits of vaccination and eradication schemes.
基金supported by the National Research Foundation of Korea(NRF)funded by the Korea government(No.2015R1C1A2A01053080)the "Cooperative Research Program for Agriculture Science&Technology Development(Project No.PJ01194503)" from the Rural Development Administration,the Republic of Korea
文摘Objective: To investigate the prevalence of bovine coronavirus(BCo V), bovine rotavirus, and bovine viral diarrhea virus in the feces of normal and diarrheic Korean native calves aged 1-81 days between April and October of 2016 in the Republic of Korea. Methods: Samples were obtained from 50 normal and 93 diarrheic(56 semi-formed, 28 loose, and 9 watery feces) calves in six different regions of northern and southern Korea. These fecal samples were tested for BCo V, bovine rotavirus, and bovine viral diarrhea virus by RT-PCR. Results: Among the three pathogens examined, infection with BCo V was especially prominent in relation to diarrhea among calves aged 1-21 days [odds ratio(OR)=9.3, 95% confidence interval(CI): 1.1-78.9; P=0.02). Infection with BCo V alone(OR=2.9; 95% CI: 1.1-7.6; P=0.03) or coinfection of BCo V with bovine viral diarrhea virus(OR=3.6; 95% CI: 1.0-12.4; P=0.04) was significantly associated with the development of loose feces. Grazing and colostrum intake strongly reduced the occurrence of diarrhea as compared to housed calves(OR=0.2; 95% CI: 0.1-0.4; P=0.00) and calves that had not been fed colostrum(OR=0.2; 95% CI: 0.1-0.7; P=0.02), respectively. Conclusions: The present study suggests that BCo V is involved in calf diarrhea in the Republic of Korea. Therefore, grazing and colostrum intake is recommended for preventing and controlling calf diarrhea caused by BCoV.
