RESUMEN
Enzootic bovine leukosis caused by the bovine leukemia virus (BLV) results in substantial damage to the livestock industry; however, we lack an effective cure or vaccine. BoLA-DRB3 polymorphism in BLV-infected cattle is associated with the proviral load (PVL), infectivity in the blood, development of lymphoma, and in utero infection of calves. Additionally, it is related to the PVL, infectivity, and anti-BLV antibody levels in milk. However, the effects of the BoLA-DRB3 allele and BLV infection on dairy cattle productivity remain poorly understood. Therefore, we investigated the effect of BLV infection and BoLA-DRB3 allele polymorphism on dairy cattle productivity in 147 Holstein dams raised on Japanese dairy farms. Our findings suggested that BLV infection significantly increased milk yield. Furthermore, the BoLA-DRB3 allele alone, and the combined effect of BLV infection and the BoLA-DRB3 allele had no effect. These results indicate that on-farm breeding and selection of resistant cattle, or the preferential elimination of susceptible cattle, does not affect dairy cattle productivity. Additionally, BLV infection is more likely to affect dairy cattle productivity than BoLA-DRB3 polymorphism.
RESUMEN
Introduction: Bovine leukemia virus (BLV) belongs to the family Retroviridae and is a causative agent for enzootic bovine leucosis, the most common neoplastic disease affecting cattle worldwide. BLV proviral load (PVL) is associated with disease progression and transmission risk but requires blood collection and quantitative PCR testing. Anti-BLV antibodies in whey have been used as a diagnostic tool for BLV infection; however, quantitative utilization has not been fully investigated. Furthermore, bovine leukocyte antigen (BoLA)-DRB3 is a polymorphic gene associated with BLV infectivity and PVL, but its effect on anti-BLV antibody levels in whey from BLV infected dams is unknown. Therefore, we aimed to investigate whether it is possible to correctly predict PVL in the blood and milk based on the amount of anti-BLV antibodies in milk, and whether the BoLA-DRB3 alleles associate with the amount of anti-BLV antibodies in milk. Methods: We examined whey from 442 dams from 11 different dairy farms located in 6 prefectures in Japan, including susceptible dams carrying at least one BoLA-DRB3* 012:01 or * 015:01 allele related with high PVL, resistant dams carrying at least one BoLA-DRB3 * 002:01, * 009:02, or * 014:01:01 allele related with low PVL, and neutral dams carrying other alleles. Results: First, our results provided compelling evidence that anti-BLV antibody levels in whey were positively correlated with the anti-BLV antibody levels in serum and with BLV PVL in blood and milk, indicating the possibility of estimating BLV PVL in blood and milk by measuring anti-BLV antibody levels in whey. Thus, our results showed that antibody titers in milk might be effective for estimating BLV transmission risk and disease progression in the field. Second, we demonstrated that anti-BLV antibody levels in whey from BLV resistant dams were significantly lower than those from susceptible and neutral dams. Discussion: This is the first report suggesting that the BoLA-DRB3 polymorphism affects anti-BLV antibody levels in whey from BLV-infected dams. Taken together, our results suggested that anti-BLV antibody levels in whey, measured by enzyme-linked immunosorbent assay, may be a useful marker to diagnose the risk of BLV infection and estimate PVL in blood and milk.
RESUMEN
Bovine leukemia virus (BLV), which causes enzootic bovine leukosis, is transmitted to calves through the milk of BLV-infected dams. Bovine leukocyte antigen (BoLA)-DRB3 is a polymorphic gene associated with BLV infectivity and proviral load (PVL). However, the effect of BoLA-DRB3 polymorphism on the infectivity and PVL of milk from BLV-infected dams remains unknown. This study examined milk from 259 BLV-infected dams, including susceptible dams carrying at least one BoLA-DRB3*012:01 or *015:01 allele with high PVL, resistant dams carrying at least one BoLA-DRB3*002:01, *009:02, or *014:01:01 allele with low PVL, and neutral dams carrying other alleles. The detection rate of BLV provirus and PVL were significantly higher in milk from susceptible dams than in that from resistant dams. This result was confirmed in a three-year follow-up study in which milk from susceptible dams showed a higher BLV provirus detection rate over a longer period than that from resistant dams. The visualization of infectivity of milk cells using a luminescence syncytium induction assay showed that the infectious risk of milk from BLV-infected dams was markedly high for susceptible dams compared to resistant ones. This is the first report confirming that BoLA-DRB3 polymorphism affects the PVL and infectivity of milk from BLV-infected dams.
RESUMEN
Fluoroquinolone is widely used for the treatment of bacterial diseases, and the emergence of quinolone resistance has become a serious concern in recent years, owing to an increase and inappropriate use of antimicrobials. Here, we attempted to understand the differences in the emergence frequency of quinolone-resistant bacterial variants in three Salmonella serotypes S. Infantis, S. Schwarzengrund, and S. Manhattan-which are mainly found in broiler industries in Japan. Emergence frequency tests for quinolone-resistant variants using enrofloxacin-containing agar plates and sequence analysis in the quinolone resistance-determining region (QRDR) of gyrA in DNA gyrase were performed. The results showed no significant difference in the emergence frequency among the three serotypes, and most of the resistant variants had mutations in the QRDR region. These findings suggest that differences in the serotypes tested are not associated with the emergence frequency of quinolone-resistant variants.
