EWF-033 FEBRUARY 2016 Wild Pigs and Ticks: Implications for Livestock Production, Human and Animal Health ii Wild Pigs and Ticks: Implications for Livestock Production, Human and Animal Health Cover: Photos courtesy of Josh Gaskamp, The Samuel Roberts Noble Foundation 1 Photo courtesy of Bill Frankenberger Wild Pigs and Ticks: Implications for Livestock Production, Human and Animal Health Introduction Today, wild pigs can be found in most regions of the Agricultural damage, habitat degradation, water U.S. and occupy 39 of 50 states (Fogerty 2007), as a quality issues, and potential for infectious and result of intentional (illegal) and accidental releases. In vector-borne disease transmissions associated with Texas, an estimated 2.6 million wild pigs can be found wild pigs (Sus scrofa) concern natural resource in all 10 ecological zones (Rollins et al. 2007) and 234 of managers and agricultural producers in TX and the 254 counties in Texas (Timmons et al. 2012). A number U.S. The problems we face today date back to early of factors including high reproductive capacity, life translocations of this animal. Domestic swine were expectancy, intelligence, and adaptability contributed to introduced to North America in the 1500s as a reliable the continued population growth of wild pigs in TX and food source, and husbandry practices allowed pigs in the U.S. (Mungall and Sheffield 1994). to range freely for forage, leading to the eventual establishment of feral populations (Wood and Barrett Wild pigs caused at least $52 million a year in damages 1979). Intentional releases of Eurasian wild boar to agricultural production in Texas alone (Adams et during the 20th century were done for recreational al. 2005), while at the national scale they likely caused purposes, and these actions also contributed to feral an estimated $1.5 billion in annual damages (Pimentel populations in the U.S. (Wood and Barrett 1979). In et al. 2007). They compete with native wildlife Texas, Eurasian wild boar were occasionally released for resources, degrade habitat, and threaten water on hunting preserves in Aransas, Bexar, and Calhoun quality by contributing to an increase in bacterial counties from 1930 to 1940. Some of these animals contamination (fecal coliforms) and cause damage escaped and interbred with wild pigs originating from to livestock pastures and crops. Recent studies domestic stock (Whitaker 1988). confirmed that wild pigs can also be infested with ticks capable of transmitting tick-borne diseases to livestock, wildlife, and humans. 2 Wild Pigs and Ticks: Implications for Livestock Production, Human and Animal Health Ticks on wild pigs in Texas surface (Figures 1-6). Sixty-two percent of the more Wild pigs from eight eco-regions of Texas were than 800 animals examined were infested with one examined for ectoparasites from 2008-2011 (Sanders or more of seven species of ticks. Ticks were found et al. 2013) in longitudinal and expanded surveys. infesting juvenile and adult male and female wild Wild pigs were taken with box, corral, and panel traps pigs year-round. Depending on species, evidence over multi-year periods at stationary sites located suggested that all tick life stages (larvae, nymphs and in the Edwards Plateau, Post-oak Savannah, and adults) infest wild pigs. Some medium sized wild pigs South Texas Plains with additional samples taken (100-150 lbs) were observed supporting more than from animals harvested by aerial gunning as part of 1000 ticks per animal. Seven species of ticks were the Texas A&M AgriLife Extension Service-Wildlife collected from wild pigs during these studies [the Services feral hog abatement program. Seven species Lone Star tick, Amblyomma americanum (Figure 1), of ticks in the family Ixodidae, or “hard” ticks, were the Cayenne tick, Amblyomma cajennense (Figure 2), identified as blood-feeding on wild pigs. The “hard the Gulf Coast tick, Amblyomma maculatum (Figure ticks” are so described because of their hard exterior 3), the Winter tick, Dermacentor albipictus (Figure 4), Figure 1. The Lone Star tick is well established in the eastern 2/3 Figure 3. The Gulf Coast tick is well established within 100- of Texas, however recent collections from the Rolling Plains and 150 miles of the Texas Gulf Coast, with expansions inland to High Plains ecoregions indicate possible range expansion into the Oklahoma. This is a 3-host tick whose adults prefer to attach to Panhandle. This is a 3-host tick with a wide host range in all life medium-to-large animals (e.g. cattle, horses, and dogs) most stages and most active from spring to fall. (Source by permission: frequently encountered from May-October, peaking in August and http://tickapp.tamu.edu) September; immature ticks are active during late-fall and winter months found commonly on ground dwelling birds. (Source by permission: http://tickapp.tamu.edu) Figure 2. The Cayenne tick is well established in the Gulf Prairies Figure 4. The Winter tick is encountered throughout TX, but it is and Marshes and South Texas Plains ecoregions. This is a 3-host most commonly encountered in a wide corridor stretching from tick with a wide host range in all life stages and can be active year the upper South Texas Plains and Edwards Plateau through the round with highest activity during spring and summer. (Source by Rolling Plains and Cross Timbers and Prairies ecoregions. This permission: http://tickapp.tamu.edu) is a 1-host tick that typically attacks large animals, especially cattle, horses, and deer during fall and winter months. (Source by permission: http://tickapp.tamu.edu) 3 Photo courtesy of Bill Frankenberger a tick with no common name, Dermacentor halli (no blood-loss, reduced growth potential, reduced figure available), the American Dog tick, Dermacentor reproductive potential, or illness resulting from the variabilis (Figure 5), and the Black-legged or Deer tick, transmission of tick-borne pathogens. Five of these Ixodes scapularis (Figure 6)]. Six of these species are tick species are known to attach to humans and have important to livestock producers whose animals may the potential for transmission of tick-borne pathogens. experience stress from tick parasitism due to irritation, Figure 5. The American Dog tick is well established in the eastern Figure 6. The Black-legged tick or Deer tick is most frequently 2/3 of Texas, and recent collections, including those from wild encountered in the eastern 1/3 of Texas, and less so moving west pigs, indicate range expansion through the Rolling Plains and High through the Cross Timbers and Prairies and Edwards Plateau Plains ecoregions to encompass the Panhandle to New Mexico. ecoregions. This is a 3-host tick with a fairly wide host range on This is a 3-host tick with a wide host range in all life stages and small-, medium-, and large-hosts in the adult stage; adult ticks are is most active from spring to fall. (Source by permission: http:// most active from October to March. (Source by permission: http:// tickapp.tamu.edu) tickapp.tamu.edu) 4 Wild Pigs and Ticks: Implications for Livestock Production, Human and Animal Health Tick life cycles await the passage of the third host used in the cycle. The species of hard ticks found on wild pigs complete On the 3rd host adult ticks will blood-feed for about 8 their life cycles in one of two patterns, either by to 14 days and mate. The large blood-fed female ticks obtaining blood meals from 3 hosts separated by drop into the habitat of the 3rd host to lay from 2,500 periods off-host (Figure 7), or by obtaining all 3 to 20,000 eggs, depending on the tick species, and blood-meals on one host (Figure 8). The potential role then die. Male ticks remain on the host to mate with of wild pigs on tick populations and tick dispersal can other female ticks until they die. There is a tendency be explained in the dynamics of these life cycles. for some 3-host tick species to select progressively larger hosts with each stage feeding, beginning The life stages of all hard ticks include the larvae, with larvae selecting small animals as depicted in nymphs and adults (Figure 12). In the 3-host life cycle, Figure 7. However many tick species are indiscriminate the larvae which are 6-legged tiny objects (sometimes regarding host selection and will use larger animals for referred to as “seed” ticks) emerge from eggs, attach to each of the 3 separate blood feedings. Three-host ticks a host for about 3-5 days for blood-feeding and drop typically produce one generation per year and exhibit into the host’s habitat to molt to 8-legged nymphs. different seasonal activity patterns by life stage. There Nymphs ascend vegetation or hide in leaf litter are active ticks in Texas year-round. awaiting a second host. Nymphs attach and blood-feed for about 4-6 days and drop into the habitat to molt In the 1-host life cycle all blood-feedings are completed to 8-legged adults. At this point the male and female on a single host in sequence: larvae, nymphs and then ticks look different (See Figures 1 - 6). Adult ticks will adults without leaving the host. This life cycle takes Figure 7. Diagram of the progression of a three host tick life cycle. (Credit Dr. Pete Teel) 5 Figure 8. Diagram of the progression of a typical one host tick life cycle. (Credit Dr. Pete Teel) from 20-30 days to complete and is restricted to Vegetation communities that provide wildlife and medium-to-large sized animals. As above, blood-fed livestock with cover, food, water, and relief from heat- engorged females drop into the habitat of the host to stress not only increase opportunities for ticks to find lay eggs and begin the cycle anew, while male ticks their next host, but support off-host tick survival.