Dose response of black American mink to Aleutian mink disease virus

Introduction Aleutian mink disease virus (AMDV) causes a serious health problem for mink globally. The disease has no cure nor an effective vaccine and selection for tolerance using antibody titer is adopted by many mink farmers. The objective of this study was to investigate the effects of various doses of a local AMDV isolate on the response of black American mink to infection with AMDV. Methods Eight black American mink were each inoculated intranasally with 0.5 mL of eight serial 10‐fold dilutions (100 to 10−7) of a 10% spleen homogenate containing a local AMDV isolate. Blood samples were collected on days 0, 20, 35, 56, 84, 140, and 196 postinoculation (dpi). Anti‐AMDV antibodies and viral DNA were tested by counter‐immunoelectrophoresis (CIEP) and PCR, respectively. Animals that were PCR or CIEP positive at 196 dpi (n = 41) were killed at 218 dpi, and samples of blood and seven organs were tested by CIEP and PCR. Results Antibody production persisted in all seroconverted mink until the termination of the experiment, whereas 71.1% of the mink showed short‐lived viremia. Significant associations were observed between inoculum dose and the incidence of viremia until 84 dpi which disappeared thereafter, whereas associations between inoculum dose and the incidence of seropositive mink were significant on all sampling occasions. Antibody titer at 218 dpi significantly decreased with decreasing inoculum dose. AMDV DNA was detected in the bone marrow, lymph nodes, and spleen samples of almost all mink inoculated at every dose but was not detected in other organs of some mink. Conclusions CIEP is more accurate than PCR for detecting AMDV infection in mink. Using antibody titer in naturally infected mink may not be accurate for the identification of tolerant mink.
The predicted probabilities for viremia across all inoculum doses were the greatest at 20 dpi, and the effect became smaller as times after inoculation prolonged, and almost disappeared after 84 dpi. The predicted probabilities for viremia across all eight inoculum doses (100 to 10‐7) on the six sampling occasions (20, 35, 56, 84, 140 and 196 day post‐inoculation) were the greatest at 20 dpi, and the effect became smaller as times after inoculation prolonged, and almost disappeared after 84 dpi.