Bovine Viral Diarrhoea Virus (BVDV), is one of the most important pathogenic viruses in cattle. The objective of this study was to evaluate the prevalence of BVDV infection in dairy cattle in Gyeunggi province in Korea and use this data as the basis for establishing an effective eradication program ...
Bovine Viral Diarrhoea Virus (BVDV), is one of the most important pathogenic viruses in cattle. The objective of this study was to evaluate the prevalence of BVDV infection in dairy cattle in Gyeunggi province in Korea and use this data as the basis for establishing an effective eradication program for this virus in both beef and dairy cattle. A total of 2,194 samples were tested for BVDV antibodies using bulk milk samples from 2,194 farms. A total of 55,263 samples were tested for BVDV antigens using ear notch samples from 842 farms from Mar to Nov 2009. The test method used was the IDEXX ELISA kit specifically targeted for this purpose. The methods used to confirm and identify PI (persistently infected) positive cattle comprised RT-PCR and immunohistochemistry(IHC). Somatic cell counts were also measured in the milk samples for all cattle. Other information gathered included milk volumes, calving intervals and open day intervals. Out of a total of 2,194 bulk milk samples, 2,007 samples (91.5%) were BVDV antibody positive and 187 samples (8.5%) were antibody negative. BVDV PI cattle were detected at 387 farms out of 842 farms (46%). There was a total of 669 out of 55,263 heads of cattle (1.2%) identified as being BVDV PI positive. The distribution of these PI positive cattle by age, were: 178 head (65.4%) less than 14 months and 94 head (34.6%) more than 14 months of age - in total 272 PI positive cattle. Most of these PI positive cattle were older than 14 months and 80.9% of them less than 23 months. 4 BVDV antigen positive samples (taken from ear notches) which were confirmed by and all shown to be positive using RT-PCR. The same samples were tested using IHC and gave clear positive results when examining ketatin cells and epidermal hair follicles. The average milk volume produced per animal on farms with some PI positive cattle in the herd was 9,630ℓ which was 211ℓ (2.15%) lower as compared to 9,841.6ℓ on negative farms. When taking results for PI positive and non PI cattle separately, the average annual milk volume from PI positive cattle per head was 7,328.4ℓ and for non PI cattle 9,735.8 ℓ. This represents a lower annual milk volume from PI positive cows of 2,407.4ℓ (24.7%) less than that from non PI cattle. Average milk fat yield was 3.81% from PI positive farms which was 0.26% lower as compared to 3.82% on negative farms. There is no significant difference between the two groups. The milk fat and milk protein figures from PI positive cattle alone were 3.75% and 3.03% respectively. These results are lower when compared to the 3.91% and 3.09% figures obtained from non PI cattle. Average calving interval per animal was 452 days on farms with some PI positive cattle which is 7 days more as compared to 445 days on farms with all negative animals. The calving interval as taken from PI positive cattle alone was 491 days which is 44 days longer compared to 447 days for non PI cattle. In addition, the open day intervals between the two groups with PI positive cattle showing 193 days and non PI cattle 11 days shorter at 182 days. The average somatic cell count per animal on farms with some PI positive cattle in the herd was 251,000/ml. This is 18,000/ml (7.7%) greater than the average count of 233,000/ml on negative farms. The average somatic cell count per animal in milk taken from PI positive cattle alone was 286,000/ml which is 39,000/ml more (15.8%) than the average figure of 247,000/ml for non PI cattle. In summary, the majority of milk samples taken from cows at the farm tested positive for BVDV antibodies. PI positive cows were widely distributed across the farms at a rate of 1.2% of all individual cattle tested. PI positive cattle yielded lower milk fat, milk protein and had longer open day intervals compared to PI negative cattle. The somatic cell counts in their milk were also greater. The IDEXX ELISA kit proved to be a successful method to detect BVDV antibodies in milk and detecting BVDV antigens from ear notch samples. RT PCR with IHC was equally successful in confirming results. This study has met its objective of evaluating the prevalence of BVDV infection in the bovine dairy population in Gyeunggi province. It forms the foundation and basis on which to build a nationwide BVDV PI eradication program. Although the scope of this study was dairy cattle, it is also crucial to evaluate the situation in beef cattle to minimize economic loss on farms in Korea.
Bovine Viral Diarrhoea Virus (BVDV), is one of the most important pathogenic viruses in cattle. The objective of this study was to evaluate the prevalence of BVDV infection in dairy cattle in Gyeunggi province in Korea and use this data as the basis for establishing an effective eradication program for this virus in both beef and dairy cattle. A total of 2,194 samples were tested for BVDV antibodies using bulk milk samples from 2,194 farms. A total of 55,263 samples were tested for BVDV antigens using ear notch samples from 842 farms from Mar to Nov 2009. The test method used was the IDEXX ELISA kit specifically targeted for this purpose. The methods used to confirm and identify PI (persistently infected) positive cattle comprised RT-PCR and immunohistochemistry(IHC). Somatic cell counts were also measured in the milk samples for all cattle. Other information gathered included milk volumes, calving intervals and open day intervals. Out of a total of 2,194 bulk milk samples, 2,007 samples (91.5%) were BVDV antibody positive and 187 samples (8.5%) were antibody negative. BVDV PI cattle were detected at 387 farms out of 842 farms (46%). There was a total of 669 out of 55,263 heads of cattle (1.2%) identified as being BVDV PI positive. The distribution of these PI positive cattle by age, were: 178 head (65.4%) less than 14 months and 94 head (34.6%) more than 14 months of age - in total 272 PI positive cattle. Most of these PI positive cattle were older than 14 months and 80.9% of them less than 23 months. 4 BVDV antigen positive samples (taken from ear notches) which were confirmed by and all shown to be positive using RT-PCR. The same samples were tested using IHC and gave clear positive results when examining ketatin cells and epidermal hair follicles. The average milk volume produced per animal on farms with some PI positive cattle in the herd was 9,630ℓ which was 211ℓ (2.15%) lower as compared to 9,841.6ℓ on negative farms. When taking results for PI positive and non PI cattle separately, the average annual milk volume from PI positive cattle per head was 7,328.4ℓ and for non PI cattle 9,735.8 ℓ. This represents a lower annual milk volume from PI positive cows of 2,407.4ℓ (24.7%) less than that from non PI cattle. Average milk fat yield was 3.81% from PI positive farms which was 0.26% lower as compared to 3.82% on negative farms. There is no significant difference between the two groups. The milk fat and milk protein figures from PI positive cattle alone were 3.75% and 3.03% respectively. These results are lower when compared to the 3.91% and 3.09% figures obtained from non PI cattle. Average calving interval per animal was 452 days on farms with some PI positive cattle which is 7 days more as compared to 445 days on farms with all negative animals. The calving interval as taken from PI positive cattle alone was 491 days which is 44 days longer compared to 447 days for non PI cattle. In addition, the open day intervals between the two groups with PI positive cattle showing 193 days and non PI cattle 11 days shorter at 182 days. The average somatic cell count per animal on farms with some PI positive cattle in the herd was 251,000/ml. This is 18,000/ml (7.7%) greater than the average count of 233,000/ml on negative farms. The average somatic cell count per animal in milk taken from PI positive cattle alone was 286,000/ml which is 39,000/ml more (15.8%) than the average figure of 247,000/ml for non PI cattle. In summary, the majority of milk samples taken from cows at the farm tested positive for BVDV antibodies. PI positive cows were widely distributed across the farms at a rate of 1.2% of all individual cattle tested. PI positive cattle yielded lower milk fat, milk protein and had longer open day intervals compared to PI negative cattle. The somatic cell counts in their milk were also greater. The IDEXX ELISA kit proved to be a successful method to detect BVDV antibodies in milk and detecting BVDV antigens from ear notch samples. RT PCR with IHC was equally successful in confirming results. This study has met its objective of evaluating the prevalence of BVDV infection in the bovine dairy population in Gyeunggi province. It forms the foundation and basis on which to build a nationwide BVDV PI eradication program. Although the scope of this study was dairy cattle, it is also crucial to evaluate the situation in beef cattle to minimize economic loss on farms in Korea.
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