CONICET | Buscador de Institutos y Recursos Humanos

Lomonaco Mariana, Sowul Mariana, Malacari Dario, Alvarez Irene, Porta Natalia, Jaworski Juan Pablo, Gutierrez Geronimo, Zabal Osvaldo, Trono KarinaPasteurization and the spray-drying heat treatments are affective to inactive bovine leukemia virus in milk and colostrumThe consumption of fresh colostrum and milk during calf breeding as usual practices in dairy facilities is strongly suspected to be responsible of BLV transmission at very young ages, according to our recent findings. To determine the effect of colostrum spray-drying and milk pasteurization on BLV infectivity, both treatments were run on scale-down conditions using fresh colostrum and milk from BLV-negative cows spiked with BLV. Four groups of susceptible lambs were inoculated with (1) raw colostrum spiked with BLV-infected cells, (2) raw colostrum spiked with cell-free BLV particles, (3) raw colostrum spiked with BLV-infected cells and then spray-dried, (4) raw colostrum spiked with cell-free BLV virus and then spray-dried. Other four groups of susceptible lambs were inoculated with (5) raw milk spiked with BLV-infected cells (FLK cell line), (6) raw milk spiked with cell-free BLV particles, (7) raw milk spiked with BLV-infected cells and then pasteurized, (8) raw milk spiked with cell-free BLV virus and then pasteurized. Pasteurization was done in-house with a calibrated laboratory water bath. A spray-dryer with industry settings for inlet and outlet temperatures was used. Groups inoculated with untreated colostrum and milk BLV-spiked samples, showed evidence of infection 60 days after inoculation, with seroconversion and provirus detection in blood. Infection was detectable in both cases, with colostrum/milk spiked with BLV-infected cells or cell-free BLV virus. None of the lambs inoculated with treated colostrum or milk showed evidence of infection after 60 days post-inoculation. This work provides direct evidence that the experimental spray-drying process as well as pasteurization used in this study were effective in inactivating infectious BLV in colostrum and milk. These findings suggest that the risk for BLV transmission could be reduced if both secretions are treated previous to consumption in dairy facilities. The effect of these treatments on the antibodies and their characteristics present in colostrum and milk should be investigated.

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