2013 Annual Report
1a.Objectives (from AD-416):
To determine the level of ivermectin in the blood serum of pastured cattle that are provided with free-access to a solid, cooked protein supplement that is medicated with ivermectin.
1b.Approach (from AD-416):
Cattle will be placed in a 17-acre pasture and allowed to freely range the entire pasture. A single tub containing an ivermectin-medicated protein block and/or a single tub containing an ivermectin-medicated mineral block will be placed inside a central penning area supplied with water. The protein block and/or mineral block(s) will be weighed prior to allowing cattle access. Once the cattle are allowed access to the treatment block(s), the blocks will be weighed twice per week to determine (by weight) the quantity of material that is being taken in by the cattle. Once per week the cattle will be placed in a chute and a blood sample will be obtained from the jugular vein of each animal in separate vacuum tubes. Blood samples will then be processed to obtain the serum from the whole-blood, and the serum will be frozen for later analysis. Serum samples will be analyzed by HPLC to determine the concentration of ivermectin in each serum sample. All data collected from the study will then be tabulated to establish the amount of medicated material they are taking in and the subsequent concentration of ivermectin in the blood system.
Results of the study that were essentially completed in FY 2011 led to the initiation of further field studies that are now being conducted in two separate locations within the permanent quarantine zone under the direction of the USDA, APHIS, VS, Cattle Fever Tick Eradication Program. One portion of the study was conducted in Webb Co., TX, against southern cattle ticks. Initiation of the study occurred in September 2011, and the number of ticks on the animals at that time, before treatment, was 502. By the end of three months (December 2011), the number of ticks on the animals was reduced to 3 ticks in total. Since the fourth month after treatments with the ivermectin-medicated tubs were deployed (January 2012), no ticks have been obtained from any of the animals in the study. The second portion of the study was conducted in Kinney Co., TX, against cattle ticks. At ten months after the study was initiated, the number of ticks on the animals has been reduced from 1,247 down to 0. One major advantage of this technology is that it does not require frequent gathering of cattle for treatment, which is a major incentive to the producer to maintain cattle on the premises rather than vacating the premises. Thus, this technology continues to show great promise as a "stand alone" treatment method for eradicating cattle fever ticks. Monitoring of the cattle herds at each location is conducted by APHIS, Animal Health Technicians and Veterinarians through on-site visits that occur on a monthly basis, and data obtained from the studies is transmitted to cooperating parties through emails. A third field trial was initiated in January 2013 in Starr Co, Texas, and is presently ongoing.