Use of Supplemental Feeding and Delivery of Oral Treatment for Managing Wildlife Diseases: A Case Study of Ivermectin Use in South Texas

Biosurveillance of zoonotic diseases of public health concern is a necessary action to protect communities and animal health from potentially life-threatening effects. Many zoonoses have a wildlife component which presents a challenge for effective delivery of treatment to prevent disease. Bovine babesiosis (cattle fever) caused by infection with Babesia bovis or B. bigemina and vectored by two species of ticks, Rhipicephalus microplus and R. annulatus, had devastating impacts on the United States cattle industry in the late 1800’s and the first half of the 20th century. Due to the continued presence of cattle fever ticks along the Texas-Mexico border and occasional outbreaks recorded beyond the permanent quarantine zone, treatment programs targeting wildlife, which also can be hosts for the tick vectors in addition to cattle, are now being implemented. The use of corn treated with ivermectin, an anti-parasitic agent effective at killing cattle fever ticks, has been identified as an effective method to treat white-tailed deer (Odocoileus virginianus) to treat and prevent infestation with cattle fever ticks. In Texas, many white-tailed deer populations are accustomed to consuming corn from supplemental feeders, and previous studies found feeding ivermectin treated corn is a successful method for controlling ticks on deer. Infested white-tailed deer were recently discovered in Port Mansfield, TX. However, on East Foundation’s El Sauz Ranch, an adjacent property to Port Mansfield, cattle fever ticks were not found. Therefore, as a preventative measure, ivermectin treated corn is being used to keep ticks from coming onto the property. The overall research goal is to evaluate the use of ivermectin treated corn feeders for mitigating tick infestation. White-tailed deer were the primary target species in my study. Deer frequency and corn consumption data were collected from feeder stations utilizing infrared cameras to capture animal species and feeder visitation. The distances for 18 feeders on El Sauz Ranch relative to the study boundary fence line were categorized as near (2.5 km). Ivermectin treated corn consumption for the treatment period (March-July 2020) after pre-baiting for one or two months was highest at near feeders, with an average consumption rate of 750 pounds, followed by far feeders (709 pounds) and mid feeders (629 pounds). Pre-baiting was conducted in December of 2019 and January of 2020. Due to visitation of larger male deer, it is likely that they are consuming more ivermectin corn and have a higher chance of receiving treatment for tick infestation. This study found that feed availability encouraged wildlife visitations throughout the year and pilot results suggest pre-baiting increased ivermectin treated corn consumption, which is recommended to aid in maintaining the current cattle fever tick free environment