Seroprevalence of Bovine Leukemia Virus & Associated Risk Factors in Black & White Yaks

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Ma et al. published a paper in 2016 that focused on the presence of bovine leukemia virus in black and white yaks in northwest China. The researchers also examined the risk factors that affect the seroprevalence of the bovine leukemia virus. This virus is a member of the genus Deltaretrovirus and a member of the family Retroviridae. The virus can be transmitted via horizontal and vertical transmission. The virus can cause a chronic disease called enzootic bovine leucosis in cattle. This results in economic losses to the cattle owners.

The study design is described in the following sentences. The researchers obtained 974 blood samples from white yaks and 610 blood samples from black yaks. The blood samples were centrifuged to collect the serum. The researchers used an ELISA kit to evaluate the presence of bovine leukemia virus antibodies. The samples that tested positive for this antibody were further evaluated for risk factors such as gender, season, age, region and breed using statistical analysis.
Results show that 21% of the black and white yak population was seropositive for bovine leukemia virus. Researchers analyzed the statistical data for risk factors associated with the virus. Results show that males had a higher seroprevalence compared to females. Spring and autumn seasons had a higher seroprevalence than other seasons. The yaks aged between 3 and 5 years had a higher seroprevalence than yaks aged less than 1 year. The seroprevalence of the region where the black yaks reside had a higher seroprevalence than the region where the white yaks live. This may be due to the fact that the region where the white yaks reside is close to the capital of Gansu province in China. This location may have better farm management methods compared to the region where the black yaks reside. When all of these results are statistically analyzed, the P value determined if the risk factor is associated with the virus. If the P value was less than 0.05 then the risk factor was said to be associated with the virus. The statistical analysis showed that only the breed risk factor was associated with the virus. The black yaks had a 1.36 times higher risk of infection compared to the white yaks. The genetic differences between the black and white breeds may result in different susceptibilities to the virus. Additionally, the number of white yaks that exist is much lower than the number of black yaks that exist. This may indicate that the white yaks are managed more properly compared to the black yaks.

This research is valuable in many ways. First, the results indicate that black yaks are more likely to be infected than white yaks. This would allow yak owners to take better care of their black yaks to prevent them from getting infected by the virus. Secondly, since the virus can be transmitted vertically and the virus infects the yaks for life, the yaks that have the virus should not be allowed to mate. These yaks can be separated from the yak population to prevent another generation of virus-infected yaks from occuring. More emphasis should be placed on taking care of the black yaks to prevent them from being infected.

The research design mentioned above and the results of the study add a lot to our understanding. First, the association between risk factors and a disease can be determined using statistical analysis. This research design can be replicated in other studies that focus on other wildlife diseases that affect animals. This may be helpful in determining which risk factor associated with diseases needs more preventative measures. This can be utilized for preventing diseases from occurring in animals. Secondly, this is the first documented research that assesses yaks for the bovine leukemia virus in China. Further research on this topic can examine if the virus can be transmitted to other animals through horizontal transmission. Also, further research can examine if this virus has the potential to infect humans in the future.


Ma JG, Zheng WB, Zhou DH, Qin SY, Yin MY, Zhu XQ, and Hu GX. 2016. First Report of Bovine Leukemia Virus in Infection in Yaks (Bos mutus) in China. BioMed Research International. [Internet]. Retrieved from



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