Simulated interactions of white-tailed deer (Odocoileus virginianus), climate variation and habitat heterogeneity on southern cattle tick (Rhipicephalus (Boophilus) microplus) eradication methods in South Texas, USA

Authors: WANG, HSIAO-HUNG - Texas A&M University; TEEL, PETE - Texas A&M University; GRANT, WILLIAM - Texas A&M University; SCHUSTER, GRETA - Texas A&M University; Perez De Leon, Adalberto - Beto

Submitted to: Ecological Modeling
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/2016
Publication Date: N/A
Citation: N/A

Interpretive Summary: White-tailed deer can be infested with cattle fever ticks, which transmit microbes causing diseases that are deadly. These white-tailed deer infestations compromise efforts by the Cattle Fever Tick Eradication Program to keep the U.S. free of cattle fever ticks. As part of our research efforts to generate science-based evidence to adapt Cattle Fever Tick Eradication Program operations in the context of global change, a model was developed to assess how the involvement of white-tailed deer impacts eradication practices. Specifically, we assessed effects on: 1) the treatment of cattle against ticks every two weeks for nine, or twelve consecutive months; and 2) the removal of cattle, also known as pasture vacation, for twelve consecutive months to eliminate ticks infesting pastures. The application of each of these eradication methods was simulated during each of three different annual temporal weather profiles for temperature, a humidity index, and rain. Each of the methods suppressed the number of immature ticks in the environment to near zero. However, some immature ticks survived, and white-tailed deer remained infested throughout the treatment period. Within 30 to 60 days after the termination of each treatment, tick infestations began to increase, and within 2 years after the initiation of each treatment, populations of immature ticks had increased to pretreatment levels. Differences in treatment efficacy and tick population recovery rates were influenced by (1) the level of pre-treatment infestation, (2) weather conditions during the treatment year, and (3) weather conditions during the post-treatment recovery period. Treatment efficacy and tick population recovery also was influenced by the habitat preferences of cattle and white-tailed deer. During treatment periods, white-tailed deer participated in creating isolated places, or refugia, where ticks could survive by dispersing female ticks engorged with blood into, and collecting immatures ticks from, habitats favorable for the survival and development of tick life stages in pastures. These refugia facilitated the recrudescence of infestations following the termination of treatment periods. This research-based knowledge can be used to further assess cattle fever tick-host-landscape interactions and to design alternative tick suppression methods for cattle and white-tailed deer that form part of integrated tick eradication systems.

Technical Abstract: White-tailed deer (odocoileus Virginiamis) is a host for cattle fever ticks, Rhipicephalus (Boophilus) sp.), which are vectors of the pathogens causing bovine babesiosis and anaplasmosis in cattle. Thus the potential role of white-tailed deer in compromising tick eradication efforts focused on cattle along the U.S.-Mexico border is of great concern. We developed a spatially-explicit, individual-based model to assess the impact of white-tailed deer on the efficacy of three tick standard eradication protocols: the application of acaricides to cattle every two weeks for (1) nine or (2) 12 consecutive months, or (3) the removal of cattle (“pasture vacation”) for 12 consecutive months. We simulated the application of each of these eradication methods during each of three different annual temporal weather profiles for temperature, saturation deficit, and precipitation. Each of the methods suppressed the number of host-seeking larvae in the system to near zero. However, some host-seeking larvae remained, and white-tailed deer remained infested throughout the treatment period. Within 30 to 60 days after the termination of each treatment, tick infestations began to increase, and within 2 years after the initiation of each treatment, populations of host-seeking ticks had increased to pretreatment levels. Differences in treatment efficacy and tick population recovery rates were influenced by (1) the level of pre-treatment infestation, weather conditions during the treatment year, and (3) weather conditions during the post-treatment recovery period. Treatment efficacy and tick population recovery also was influenced by the habitat preferences of cattle and white-tailed deer. During treatment periods, white-tailed deer participated in creating tick refugia by dispersing engorged females into, and collecting host-seeking larvae from, habitats favorable for the survival and development of off-host life stages. These refugia facilitated the recrudescence of infestations following the termination of treatment periods. Future applications to assess tick-host landscape interactions and to consider alternative tick suppression tactics in integrated tick eradication systems are discussed.