J. Mathews Pound

The '4-poster' passive topical treatment device to apply acaricide for controlling ticks (Acari: Ixodidae) feeding on white-tailed deer.

Abstract A ‘4-poster’ device that attracts white-tailed deer to a bait source, and as they feed, allows a self-application of a pesticide to the head, ears, and neck to control ticks was designed, constructed, and tested. The device consists of a central bin containing bait to attract deer and two feeding and application stations. These stations each have one bait port and two vertical pesticide-impregnated applicator rollers. This design allows unrestricted vertical retraction of the head to minimize injury to the deer or damage to the posts supporting the pesticide application rollers. Observations using deer demonstrated ready acceptance and repeated use by both antlered and antlerless deer. Results of an initial trial indicate that control values for lone star ticks,Amblyomma americanum(L.), exceeded 92–97% on deer that used the device regularly.

Efficacy of Amitraz Applied to White-Tailed Deer by the ‘4-Poster’ Topical Treatment Device in Controlling Free-Living Lone Star Ticks (Acari: Ixodidae)

Abstract White-tailed deer treated themselves with a commercial pour-on acaricide formulation containing 2% amitraz as they fed from an ARS-patented ‘4-poster’ topical treatment device. Whole kernel corn attracted deer to a single device placed in each of two deer-fenced pastures. In the treatment pasture, the rollers of the treatment device were charged with the acaricide, whereas the rollers of the device in the other pasture remained untreated. Deer were allowed to use the ‘4-posters’ during periods of tick activity beginning in early to midspring and lasting through late summer to early fall for three consecutive years. Pretreatment sampling of adults and nymphs with dry-ice traps and larval masses with flip cloths showed no significant differences in population indices between the two pastures; however, after the third year of treatment, control of nymphal and adult ticks in the treated pasture was 91.9 and 93.7%, respectively, when compared with the untreated pasture. Control of larval masses increased from 68.4% in year 1 to 96.4% in year 2, but declined to 88.0% in year 3, probably because of the presence of feral hogs. This study demonstrated that application of amitraz to white-tailed deer through free-choice interaction with a ‘4-poster’ device significantly reduced the abundance of free-living lone star ticks in a deer-fenced experimental pasture. Moreover, the yearly pattern of incremental increases in control and the final percentage control values for all three parasitic life stages in this topical application study were similar in magnitude to that observed in a previously conducted study in which the systemic acaricide ivermectin was used to reduce populations of free-living ticks by controlling ticks on deer.

Topical Treatment of White-Tailed Deer with an Acaricide for the Control of Ixodes scapularis (Acari: Ixodidae) in a Connecticut Lyme Borreliosis Hyperendemic Community

The 4-Poster device for the topical treatment of white-tailed deer, Odocoileus virginianus (Zimmermann), against ticks using the acaricide amitraz, was evaluated in a Lyme borreliosis endemic community in Connecticut. As part of a 5-year project from 1997 to 2002, 21-24 of the 4-Posters were distributed at residential sites in Old Lyme, CT, in a core treatment area of approximately 5.2 km(2) in fall 1997. The 4-Posters were active October to mid-December and March into May, corresponding to the peak periods of activity for adult Ixodes scapularis in this particular area. Corn consumption ranged from 361 to 4789 kg/month for October and November and 696-3130 kg/month during April. Usage of 4-Posters by deer generally was high (>90%), except during acorn masts in fall 1998 and 2001. Amitraz was applied by rollers at the estimated rate of 1.3 g active ingredient/ha/year. The abundance of host-seeking I. scapularis nymphs declined significantly (p < 0.001) in the core treatment area, as compared to a control community in Old Saybrook, CT, through 2004, over the project period from 1998 to 2003, from 9.3/100m(2) to 0.97/100m(2), rising to 1.90/100m(2) in 2004. From 1999 through 2003, there were 46.1%, 49.6%, 63.4%, 64.6%, and 70.2% reductions, respectively, in the nymphal tick population in comparison with the untreated community and initial tick abundance in 1998. Control of I. scapularis adults declined to only 19.1% in 2004; 2 years after the treatment of deer was discontinued. Differences in nymphal tick abundance between the control and core treatment area were significant in 1999 (p = 0.042) and highly significant in 2001 (p < 0.001) and 2002 (p = 0.002). The passive topical application to deer of the acaricide amitraz resulted in a significant decrease in the population of free-living I. scapularis nymphs in the treated core in Connecticut.

Therapeutic and persistent efficacy of a long-acting (LA) formulation of ivermectin against Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) and sera concentration through time in treated cattle.

The concentration-time profile, therapeutic, and persistent efficacy of a single subcutaneous injection of cattle with a long-acting (LA) formulation of ivermectin at a concentration of 630microg/kg of body weight were determined against Rhipicephalus (Boophilus) microplus. Ivermectin sera concentration in treated cattle increased to 13.0ppb within 1d after treatment, and peaked at 26.2ppb at 11d post-treatment. Ivermectin sera levels remained above the threshold level for control of feeding ticks (>or=8ppb) for 42.6d after treatment. Therapeutic efficacy of ticks on treated animals was >99.9%, and tick number, index of fecundity, engorgement weight, and egg mass weight of ticks from treated animals remained dramatically less than ticks from untreated animals. Tick number and reproductive capacity of ticks infested on treated animals at 14 and 28d post-treatment were less than for ticks on untreated animals, whereas engorgement weight and egg mass weight of treated ticks remained lower than that of untreated ticks 49d post-treatment. However, the level of control against ticks infested at 14d after treatment (99.9%) was the only post-treatment infestation interval that provided the required 99% control necessary for use in the U.S. tick eradication program. The 14d post-treatment infestation was also the only interval at which infested ticks were exposed to ivermectin levels above the threshold level of 8ppb for the entire parasitic development period. Cattle would have to be treated at intervals of no more than 31d apart to ensure that no viable ticks could reach repletion and detach from the host. Although this treatment interval is >2-fold longer than the present treatment requirement (14d), it is dramatically less than the label claim for the LA ivermectin formulation of 75d of prevention against re-infestation.

Acaricidal treatment of white-tailed deer to control Ixodes scapularis (Acari: Ixodidae) in a New York Lyme disease-endemic community.

The efficacy of topically treating white-tailed deer with an acaricide was evaluated in a Lyme disease-endemic community of southern New York State. Twenty-four 4-Poster feeders were placed in a 5.2 km(2) treatment area in Bedford, NY, while a site in Lewisboro, NY, 4.8 km distant, served as control. Treatment periods ran from 15 September to 15 December each fall from 1997 to 2001, and from 15 March to 15 May each spring from 1998 to 2002. Corn consumption averaged 15,779 kg in fall sessions and 9054 kg in spring sessions, and a mean of 89.6% of deer in the study area showed evidence of using the feeders. Deer densities, estimated by aerial snow counts, averaged 22 and 28 deer per km(2) in Bedford and Lewisboro, respectively, over a 3-year period. Significant reductions in tick numbers on deer captured in the treatment area were noted in fall 1999 compared to deer captured at the control site. Drag sampling for nymphal host-seeking ticks indicated 63.6% control in 2001, which dropped to 54.8% the following year, but reached 80% in 2003. Higher-than-normal acorn production in 2001 that likely caused a drop in deer visitation to the feeders may have reduced efficacy against larval ticks in 2002. The 4-Poster effectively reduced the density of Ixodes scapularis, though the level of control is dependent on environmental factors that affect feeding behavior of white-tailed deer.

The impact of 4-Poster deer self-treatment devices at three locations in Maryland.

From 1998-2002 twenty-five deer self-treatment devices (4-Posters), using 2% amitraz, were operated at three locations in Maryland to determine their effectiveness in controlling blacklegged ticks, Ixodes scapularis Say, and lone star ticks, Amblyomma americanum (L.). Each treatment site was approximately 518 ha and paired with a similar site lacking 4-Posters. Locations varied in deer density, tick abundance, and land use. Flagging for host-seeking ticks showed declines in tick populations at all treatment sites compared to control sites by the third year. By 2002, control of I. scapularis nymphs attributable to the 4-Poster intervention at the three sites was 69.0%, 75.8%, and 80%. Control of A. americanum nymphs at the two sites where they occurred was 99.5% and 95.3%. In 2003, the first posttreatment year, control of I. scapularis remained around 2001-2002 levels, but by 2004, an upward trend in nymphal numbers was detectable. Populations of A. americanum showed no increase posttreatment. These results demonstrate that control of these tick species is locally possible with 4-Poster intervention.

The Ivomec SR Bolus for Control of Boophilus annulatus (Acari: Ixodidae) on Cattle in South Texas

Abstract When Hereford heifers infested with Boophilus annulatus (Say) were treated with a single Ivomec SR Bolus, the concentration of ivermectin in the serum of the treated cattle reached a maximum of 8.8 ± 0.9 ppb at 2 wk posttreatment. The single bolus treatment resulted in 84.4% control of standard engorging B. annulatus females on treated cattle over the 20-wk trial. Although fewer engorged ticks were collected from the sentinel heifers exposed in the treated pasture than those in the control pasture at weeks 4, 10, and 16 posttreatment, none of the differences was statistically significant. Each exposure of sentinel cattle found free-living ticks in both the treated and control pastures, indicating the infestation was not eliminated by the treatment. When the trial was repeated using two Ivomec SR Boluses/heifer, the concentration of ivermectin in the serum of the treated cattle reached a maximum level of 31.2 ± 3.9 ppb at week 13 posttreatment. The use of two boluses/heifer resulted in 99.6% control of standard engorging B. annulatus females over the 20-wk trial. No ticks were found on sentinels placed in the treated pasture after week 9 posttreatment, an indication that the treatment had eliminated the free-living population in the treated pasture. From these studies, we conclude that a single Ivomec SR Bolus is incapable of sufficient control of B. annulatus to meet the rigid requirements of the Cattle Fever Tick Eradication Program in South Texas. Although two boluses per animal did eliminate the ticks from treated heifers and the pasture they were in, the treatment would not be sufficiently efficacious for mature cattle (>400 kg) for it to be useful in the program.

Sustained Control of Gibson Island, Maryland, Populations of Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae) by Community-Administered 4-Poster Deer Self-Treatment Bait Stations

In 1998, twenty-five 4-Poster deer treatment bait stations were deployed on Gibson Island (GI), Maryland, as part of the U.S. Department of Agriculture (USDA) Northeast Area-Wide Tick Control Project. Treatments concluded in June 2002, having achieved 80% and 99.5% control of blacklegged ticks, Ixodes scapularis, and lone star ticks, Amblyomma americanum, respectively. No area-wide tick control was attempted again on the island until 2003, when 15 Dandux-manufactured 4-Posters were purchased by the GI Corporation and operated until the present. Annual flagging at sites on the island and a similar untreated area on the nearby mainland in May and June from 1998 to 2007 has demonstrated that populations of host-seeking nymphs of both tick species have remained at consistently low levels on the island during GI Corporation administration of the 4-Posters, in spite of 40% fewer 4-Posters and increased deer density during 2003-2007.

Efficacy of the Ivomec SR Bolus for Control of Horn Flies (Diptera: Muscidae) on Cattle in South Texas

The concentration of ivermectin in the serum of Hereford heifers treated with a single Ivomec SR bolus reached a maximum of 8.8 +/- 0.9 ppb at 2 wk post-treatment. The single bolus treatment resulted in <10% mortality of adult horn flies feeding on the blood of the treated animals over the 21-wk trial. Bioassays of the manure from treated cattle showed complete inhibition of development of immature horn flies through week 19 post-treatment. When the trial was repeated using two Ivomec SR boluses/heifer, the concentration of ivermectin in the serum of the treated cattle reached a maximum level of 31.2 +/- 3.9 ppb at week 13 post-treatment. During the first 17 wk of treatment, the use of two boluses/heifer resulted in 96.2 and 81.2% mortality of adult male and female horn flies feeding on the blood of treated animals, respectively. From these studies, we conclude that a single Ivomec SR bolus used as an anthelmintic treatment can be expected to provide significant control of immature horn flies developing in the manure, but not of adults feeding on the treated cattle.

Depletion rates of injected and ingested ivermectin from blood serum of penned white-tailed deer, Odocoileus virginianus (Zimmermann) (Artiodactyla: Cervidae).

Abstract Penned female and male white-tailed deer, Odocoileus virginianus (Zimmerman), were administered ivermectin both by direct subcutaneous injection and by ingestion of ivermectin-medicated whole kernel corn. Depletion rates of ivermectin were determined by biweekly and weekly assays of blood serum. No statistical differences were observed between mean peak ivermectin serum concentrations in deer (data of sexes combined) from injection and ingestion studies, and ivermectin concentrations decreased to below detectable within 21 d after injection and 14 d after ingestion.