Burridge_41-51.qxd INTRODUCTION Wildlife are important hosts for ticks in many regions of the world (Hoogstraal & Aeschlimann 1982). In an attempt to develop a practical and stress-free method for control of ticks on wild animals, a self- medicating applicator was designed and tested successfully on deer (Sonenshine, Allan, Norval & Burridge 1996). It did not, however, lend itself to use with large numbers of animals. Consequently, an improved self-medicating applicator was developed, which could be retrofitted to existing devices that attract wild animals, such as troughs containing feed or water (Burridge, Simmons & Simmons 2000, 2003; Simmons, Burridge & Simmons 2001). This improved applicator was designed to transfer oil- based acaricides passively to wild animals, but its versatile design was such that it had the potential to be used to treat animals of any size with any oil- based compound. Consequently preliminary trials with this applicator were formulated to test whether the concept of delivery of oil-based treatments to both domestic and wild animals through the device was practical using various animal species natural- ly infected or infested with endo- or ecto-parasites. Initial studies were conducted to determine the effi- cacy of the applicator as a method for delivery of treatments to control gastrointestinal nematodes in cattle and deer in the United States, flies on cattle in the United States, and ticks on cattle in South Africa. The results of these trials are described in this report. 41 Onderstepoort Journal of Veterinary Research, 71:41–51 (2004) Development of a novel self-medicating applicator for control of internal and external parasites of wild and domestic animals M.J. BURRIDGE1, L.A. SIMMONS1, E.H. AHRENS2, S.A.J. NAUDÉ3 and F.S. MALAN3 ABSTRACT BURRIDGE, M.J., SIMMONS, L.A., AHRENS, E.H., NAUDÉ, S.A.J. & MALAN, F.S. 2004. Develop- ment of a novel self-medicating applicator for control of internal and external parasites of wild and domestic animals. Onderstepoort Journal of Veterinary Research, 71:41–51 Four trials, three in the United States and one in South Africa, were conducted to evaluate the poten- tial value of a novel self-medicating applicator in the passive control of gastrointestinal nematodes in cattle and deer, and of flies and ticks on cattle using oil-based treatments. The results of the tri- als demonstrated that this applicator is an effective and practical device for the passive treatment of both deer and cattle for trichostrongyle infections using the endectocide, moxidectin (Cydectin®, Fort Dodge Animal Health, USA), of cattle for horn fly (Haemotobia irritans) infestations using the insec- ticide, cyfluthrin (CyLence®, Bayer AG, Germany) and of cattle for tick infestations (in particular Amblyomma hebraeum and Rhipicephalus appendiculatus) using the acaricides deltamethrin and amitraz (Delete All®, Intervet, South Africa). Keywords: Amitraz, cattle, cyfluthrin, deer, deltamethrin, fly control, moxidectin, nematode control, self-medicating applicator, tick control 1 Department of Pathobiology, College of Veterinary Medicine, University of Florida, P.O. Box 110880, Gainesville, Florida 32611-0880, USA 2 3551 Zenner-Ahrens Road, Kerrville, TX 78028, USA 3 Intervet Research Unit, P.O. Box 124, Malelane, 1320 South Africa Accepted for publication 23 September 2003—Editor MATERIALS AND METHODS Self-medicating applicator The applicator, given the trademark of the Appli- Gator™ (University of Florida), is a semicircular device composed of a solid outer pipe made of rigid polyvinyl chloride containing a rigid porous internal pipe made of high-density polyethylene, with an upper portion of the outer pipe removed to allow animals to contact the internal porous material (Fig. 1). It was attached to a feed trough using plastic ties or nuts and bolts, and primed with a predeter- mined volume of oil-based compound sufficient to saturate the porous pipe, after which an additional measured treatment dose is added to the porous pipe. Both the priming and treatment doses were added by syringe through treatment fill ports in the exposed porous pipe. When cattle or deer feed from the trough the applicator deposits the com- pound on the neck region, thus treating them in a stress-free manner without the need for handling equipment. Treatments Anthelmintic The anthelmintic used was Cydectin® (Fort Dodge Animal Health, Fort Dodge, Iowa, USA) containing 0.5 % of the second-generation endectocide mox- idectin. Moxidectin was selected because it is high- ly efficacious against gastrointestinal parasites of cattle and deer (Craig 1999), it is of low toxicity in terms of tissue residues and ecological safety (Herd 1995), it has been used successfully for internal par- asite control in farmed deer in New Zealand (Audigé, Wilson & Morris 1998; Waldrup, Mackintosh, Duffy, Labes, Johnstone, Taylor & Murphy 1998), it has a persistent effect against target nematodes (Eysker & Eilers 1995; Hubert, Kerboeuf, Cardinaud & Blond 1995; Rendell & Callinan 1996), and it is formulated as an oil-based pour-on that is absorbed through the skin. Insecticide The insecticide used is CyLence® (Bayer AG, Lever- kusen, Germany) containing 1% cyfluthrin. Cyfluthrin was selected because it was commercially market- ed for use in fly control on cattle in the USA, it is available as an oil-based pour-on formulation, and it is an effective insecticide (Sulaiman, Pawanchee, Othman, Jamal, Wahab, Sohadi, Rahman & Pandak 1998; Vale, Mutika & Lovemore 1999). Acaricide The acaricide used was Delete All® (Intervet, Isan- do, South Africa) containing 0.5 % deltamethrin, 2 % amitraz and 0.5 % piperonyl butoxide. This acarici- dal combination was selected because it is formu- lated as an oil-based pour-on and because delta- methrin and amitraz are effective for the control of ticks on cattle in Africa (Haigh & Gichang 1980; Lu- guru 1991; Kagaruki 1996; Mekonnen 2001). Experimental designs Anthelmintic trial Nineteen male fallow deer (Dama dama), resident on a private wildlife ranch in Putnam County, Flor- ida, USA, were selected for the cervid anthelmintic trial. They were 2–5 years of age and were natural- ly infected with trichostrongyles. The deer were randomly assigned to one of two fenced pastures on the ranch. Ten of them were kept in a pasture containing an applicator attached to a feed trough (the applicator group) and the remaining nine on the other pasture with no attachments to the feed trough (the control group). Eight Brahman, Angus and Hereford cattle from a privately owned farm in Hendry County, Florida, were selected for the bovine anthelmintic trial. They were 1–4 years of age and consisted of four heif- ers, two steers and two bulls, all naturally infected with trichostrongyles. The cattle were assigned ran- domly by sex to one of two fenced pastures so that each group contained two heifers, one steer and one bull. They were divided into an applicator group and a control group as for the deer. The 19 deer and eight cattle were individually restrained in squeeze chutes, and faecal material was removed manually from the rectum of each animal for examination for trichostrongyle eggs. The animals were then returned to their respective pas- tures on either the wildlife ranch or the cattle farm. The applicators were primed with enough mox- idectin to saturate the porous columns, then addi- tional moxidectin (80 ml for the ten deer and 84 ml for the four cattle) was added to the devices to form reservoirs for treatment, based on a dosage of 0.5 mg moxidectin per kg body mass. Commercial deer or cattle feed was placed in the feed trough in each of the pastures, and the animals were allowed to feed. While feeding, the ten deer and the four cattle in the applicator groups received a total of 80 ml and 84 ml of moxidectin respectively, until all 42 Self-medicating applicator for control of parasites of wild and domestic animals available moxidectin in the reservoirs had been transferred to the necks of the animals. The deer and cattle were restrained individually again on days 6 and 12 and on days 7, 14, and 21 respec- tively, after initiation of the trials to obtain a series of post-treatment faecal samples. Each faecal sample was placed in a plastic bag immediately after collection, and the bag was sealed and stored on ice for transport to the laboratory. The sample was quantitatively examined for tricho- strongyle eggs using a modification of the McMas- ter egg-counting method (Whitlock 1948). A 4 g amount of faeces was mixed with 26 ml of Fecal Float (Phoenix Pharmaceuticals Inc., St. Joseph, Missouri, USA), poured through a layer of cheese cloth, and distributed to a two-chambered McMas- ter slide. After a 5-min interval the McMaster slide egg-counting grid was examined microscopically at 100x magnification for the presence of trichostron- gyle eggs. Insecticidal trial Sixteen 2 to 5-year-old Brahman-cross cows from a privately owned ranch in Starr County, Texas, USA, were selected for the insecticidal trial. They were randomly assigned in equal numbers to one of two fenced pastures at the ranch, and were divided into an applicator group and a control group as in the anthelmintic trial. The trial commenced in March when horn flies (Haematobia irritans) were natural- ly abundant on the cattle on the ranch. Counts of horn flies were made visually on each of the 16 cattle in the trial on the day prior to onset of the trial. The applicator was primed with enough cyfluthrin to saturate the porous column, then 96 ml 43 M.J. BURRIDGE et al. � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �� � � � � � � � � � � � � � � � �� � � � � � � � � � � � � � � � � � � � ��������� ������ � ��� ����� ��� ���� � ����� ����� �� ��� ��� � �� ������� � ��� ��������� � �������� ��� �� � ��� � � � � FIG. 1 Schematic drawing of cross-section of an AppliGator™ self-medicating applicator mounted on the edge of a feed trough of additional cyfluthrin were added to the device to form a reservoir for treatment of the cattle, based on a dosage of 12 ml for animals exceeding 363 kg body mass. Commercial cattle feed was placed in the trough in each pasture, and the animals were allowed to feed. Counts of horn flies were made on day 1 and then weekly from days 7–42 to obtain a series of post-treatment fly counts. Acaricidal trial Fifteen Beefmaster-cross cattle on a farm belong- ing to the Intervet Research Unit in Malelane, Mpu- malanga Province, South Africa were selected for the acaricidal trial. The cattle were 1-year-old ani- mals of mixed sexes and were randomly assigned in equal numbers to one of three fenced tick-infest- ed pastures at the farm. Five cattle were kept on a pasture containing an applicator attached to a feed trough (the applicator group) and five each in two other pastures with no attachments to the feed troughs (the positive control and negative control groups). The trial commenced in January when ticks (including Amblyomma hebraeum, Rhipicephalus appendiculatus, Rhipicephalus simus and Boophi- lus spp.) were naturally abundant on the pastures of the farm. Counts of adult ticks were made by species on each of the 15 cattle on the day prior to onset of the trial. The ticks were counted macroscopically in situ while the animals were restrained on a cement floor in a crush pen with both a head and a body clamp. Two people performed the tick count on each ani- mal, and a third person recorded the data. Dispos- able latex gloves were worn during tick counting, with new sets of gloves worn for each experimental group. The applicator was primed with enough deltamethrin/amitraz to saturate the porous col- umn, then 95.5 ml of additional deltamethrin/ami- traz was added to the device to provide a reservoir for treatment of the cattle, based on a dosage of 0.1 ml per kg body mass. Cattle on the pasture containing the positive control group were treated by application of deltamethrin/amitraz pour-on along the back line using a dosage of 0.1 ml of pour-on per kg body mass. Cattle in the pasture containing the negative control group were treated only for ethical reasons when their tick burdens became too heavy, and in those instances the acaricide used was Triatix Cattle Spray® (Intervet, Isando, South Africa) containing 12.5 % amitraz at a rate of 5 l per animal. Commercial cattle feed was added to the trough in each pasture, and the animals were allowed to feed. Cattle in the applicator and positive control groups were treated with deltamethrin/amitraz weekly from days 0 to 77 using an applicator and pour-on, respectively. After tick counts had been made, cat- tle in the negative control group were treated with amitraz for ethical reasons on days 0, 14, 28, 35, 49, 63 and 84 due to the heavy tick challenge. Counts of adult ticks were made on day 7 after treatment and then weekly to day 84 to obtain a series of post-treatment tick counts by species. Statistical analyses The data were analyzed for statistical differences in trichostrongyle egg counts, fly counts and tick counts between the test groups using the two-tailed t test. For egg and fly counts, differences between treated and untreated animals were analyzed for each day on which counts were made. For tick counts, differences between treated animals (the applicator and positive control groups) and untreat- ed animals (the negative control group) were ana- lyzed only for those days when the negative control cattle were treated for ethical reasons, with the tick counts on negative control cattle preceding treat- ment. These analyses were selected to minimize 44 Self-medicating applicator for control of parasites of wild and domestic animals TABLE 1 Effect of moxidectin on trichostrongyle infections in fallow deer when applied passively using a self-med- icating applicator Animal no. No. of trichostrongyle eggs per by group gram of faeces by day of trial Day 0 Day 6 Day 12 Applicator group 362 75 0 a 367 25 0 0 374 300 0 0 400 100 a 0 441 75 0 0 444 25 0 0 489 75 0 0 523 100 0 0 544 125 a 0 561 75 0 0 Control group 307 50 50 50 364 50 75 75 372 125 125 125 410 75 50 50 467 125 125 150 490 25 25 a 533 100 125 100 568 150 100 175 586 75 100 75 a = No sample collected due to empty rectum the effect of treatment of the negative control cattle. Ideally from the scientific point-of-view, the nega- tive controls should not have been treated, increas- ing the number of ticks on each animal, but ethical- ly these cattle had to be treated periodically to min- imize the impact of the heavy burdens on their health and well-being. RESULTS Anthelmintic trials The ten deer in the applicator group had a mean burden of 97.5 trichostrongyle eggs per gram (epg) of faeces before treatment with moxidectin from an applicator. The egg counts in all deer in the group dropped to zero by day 6 post-treatment and re- mained at zero by day 12 post-treatment (Table 1). The trichostrongyle egg counts were significantly less (P < 0.001) in the deer treated using the appli- cator than were those in the untreated deer on both days 6 and 12 of the trial. The four cattle in the applicator group had a mean trichostrongyle egg count of 300 epg of faeces before treatment with moxidectin. After treatment, the egg counts dropped to zero in three of the four cattle, the exception being steer no. 109 in which the count dropped to 50 epg (Table 2). This steer did not feed from the trough during the first day of the trial and thus had no contact with the applicator 45 M.J. BURRIDGE et al. TABLE 2 Effect of moxidectin on trichostrongyle infections in cattle when applied passively using a self-medicating applicator No. of trichostrongyle eggs per gram of faeces by day of trial Animal no. by group Day 0 Day 7 Day 14 Day 21 Applicator group 102 250 0 0 0 105 475 0 0 0 109a 200 50 50 50 111 275 0 0 0 Control group 101 225 175 175 200 107 175 200 225 300 110 400 475 500 550 113 200 175 175 175 a Steer no. 109 did not make contact with the applicator during the first day of trial TABLE 3 Effect of cyfluthrin on horn fly infestations on cattle when applied passively using a self-medicating applicator No. of horn flies on animal by day of trial Animal no. by group Day -1 Day 1 Day 7 Day 14 Day 21 Day 28 Day 35 Day 42 Applicator group 34 150 0 0 4 18 70 220 470 39 300 0 0 4 20 50 200 500 41 200 0 0 2 26 110 240 500 42 200 0 0 10 24 100 240 480 43 250 0 0 4 14 68 180 500 44 400 0 0 12 18 76 300 450 45 300 0 0 6 16 60 200 600 47 550 0 0 14 22 80 250 450 Control group 38 180 200 470 400 400 400 450 600 48 250 250 500 380 420 380 470 460 49 300 400 550 400 370 300 440 500 50 500 450 600 470 410 500 450 450 55 280 300 400 360 350 360 400 500 61 200 250 450 350 380 400 380 450 73 550 600 560 500 450 500 500 480 93 300 400 600 480 400 450 500 550 46 Self-medicating applicator for control of parasites of wild and domestic animals T A B L E 4 E ff e ct o f d e lta m e th ri n /a m itr a z o n t ic k in fe st a tio n s o n c a tt le w h e n a p p lie d p a ss iv e ly u si n g a s e lf- m e d ic a tin g a p p lic a to r N o . o f a d u lt tic ks a o n a n im a l b y d a y o f tr ia l A n im a l n u m b e r b y g ro u p D a y -1 D a y 7 D a y 1 4 D a y 2 1 D a y 2 8 D a y 3 5 D a y 4 2 D a y 4 9 D a y 5 6 D a y 6 3 D a y 7 0 D a y 7 7 D a y 8 4 A p p lic a to r g ro u p b 0 1 /0 1 4 8 5 7 8 1 7 1 7 1 1 2 7 1 4 9 1 8 5 1 6 2 0 7 0 1 /0 2 5 4 2 4 5 1 1 2 2 2 3 3 4 1 3 2 0 1 7 1 5 4 3 1 8 0 1 /1 1 4 4 8 4 0 1 3 9 1 2 1 9 1 2 1 1 1 3 4 1 6 3 0 1 /2 2 4 2 3 2 9 4 4 0 7 1 2 6 6 4 5 6 3 6 3 9 1 9 1 5 2 3 1 9 0 2 /0 4 3 8 5 6 2 4 6 3 9 1 8 7 1 4 2 2 6 7 3 2 0 5 2 2 2 1 1 P o si tiv e c o n tr o l g ro u p b 0 1 /1 3 3 8 2 1 9 2 1 0 2 7 7 1 8 2 2 7 6 5 7 7 2 7 1 9 5 6 0 1 /1 4 4 5 1 3 2 0 2 0 3 1 3 5 2 2 4 4 8 9 9 7 7 1 1 6 3 6 2 5 1 1 0 1 /2 4 4 9 2 4 3 6 1 4 0 1 0 0 1 6 0 3 2 5 3 1 9 9 3 2 2 2 1 2 1 4 0 1 /3 2 4 5 7 8 7 8 7 8 6 1 6 9 2 4 5 8 2 2 8 1 7 1 0 9 5 0 2 /0 8 2 9 9 6 9 7 7 3 1 1 0 6 8 3 6 1 2 3 1 7 1 4 4 6 N e g a tiv e c o n tr o l g ro u p c 0 1 /0 3 3 5 5 2 9 4 5 4 6 1 1 6 6 5 2 1 5 1 1 5 4 3 2 2 4 7 2 0 2 1 8 9 4 1 1 7 0 1 /0 6 3 5 6 3 1 2 6 5 1 1 5 8 8 3 6 1 7 4 1 5 2 3 1 7 8 3 3 1 6 3 0 1 0 0 1 3 3 0 1 /1 2 3 8 3 3 7 3 5 4 6 1 8 5 6 3 6 2 1 6 1 8 3 4 1 0 1 2 4 4 1 8 3 4 1 0 9 1 2 8 0 1 /2 6 3 9 4 3 7 3 6 7 1 1 6 3 7 2 6 1 7 2 1 3 1 5 0 1 4 0 4 3 1 2 8 1 0 7 1 2 7 0 2 /0 7 5 0 0 2 4 1 6 3 5 4 7 9 1 2 1 5 4 1 7 3 7 1 3 4 1 4 8 3 2 6 6 6 1 4 6 a A m bl yo m m a he br ae um , R hi pi ce ph al us a pp en di cu la tu s, R hi pi ce ph al us s im us a n d B oo ph ilu s sp p . tic ks b E a ch a n im a l t re a te d w ith d e lta m e th ri n /a m itr a z a t w e e kl y in te rv a ls f ro m d a y 0 t h ro u g h d a y 7 7 c E a ch a n im a l t re a te d w ith a m itr a z o n d a ys 0 , 1 4 , 2 8 , 3 5 , 4 9 , 6 3 a n d 8 4 f o r e th ic a l r e a so n s d u e t o h e a vy t ic k ch a lle n g e 47 M.J. BURRIDGE et al. T A B L E 5 E ff e ct o f d e lta m e th ri n /a m itr a z o n A m bl yo m m a he br ae um in fe st a tio n s o n c a tt le w h e n a p p lie d p a ss iv e ly u si n g a s e lf- m e d ic a tin g a p p lic a to r M e a n n o . o f a d u lt tic ks o n a n im a l b y d a y o f tr ia l T ri a l g ro u p a D a y -1 D a y 7 D a y 1 4 D a y 2 1 D a y 2 8 D a y 3 5 D a y 4 2 D a y 4 9 D a y 5 6 D a y 6 3 D a y 7 0 D a y 7 7 D a y 8 4 A p p lic a to r 7 3 .4 2 4 1 6 .2 9 5 .4 6 .8 7 .6 3 .2 3 .8 2 4 .2 1 .6 2 .2 P o si tiv e c o n tr o l 7 4 .6 1 2 .6 6 .2 4 3 .6 1 .4 1 .4 0 .8 0 .2 6 .8 6 .6 4 .6 3 .4 N e g a tiv e c o n tr o l 8 6 .8 1 4 .4 5 3 .2 4 .8 5 9 .4 8 .4 1 .6 3 7 .8 2 .2 4 3 .2 2 8 1 4 .6 a A p p lic a to r g ro u p a n d p o si tiv e c o n tr o l g ro u p t re a te d w ith d e lta m e th ri n /a m itr a z a t w e e kl y in te rv a ls f ro m d a y 0 t h ro u g h d a y 7 7 ; n e g a tiv e c o n tr o l g ro u p t re a te d w ith a m itr a z o n d a ys 0 , 1 4 , 2 8 , 3 5 , 4 9 , 6 3 a n d 8 4 f o r e th ic a l r e a so n s d u e t o h e a vy t ic k ch a lle n g e T A B L E 6 E ff e ct o f d e lta m e th ri n /a m itr a z o n R hi pi ce ph al us a pp en di cu la tu s in fe st a tio n s o n c a tt le w h e n a p p lie d p a ss iv e ly u si n g a s e lf- m e d ic a tin g a p p lic a to r T ri a l g ro u p a M e a n n o . o f a d u lt tic ks o n a n im a l b y d a y o f tr ia l D a y -1 D a y 7 D a y 1 4 D a y 2 1 D a y 2 8 D a y 3 5 D a y 4 2 D a y 4 9 D a y 5 6 D a y 6 3 D a y 7 0 D a y 7 7 D a y 8 4 A p p lic a to r 3 6 3 .8 4 .8 4 .4 1 3 4 .2 2 7 .6 1 4 .4 7 .2 9 .8 0 .4 0 .2 0 .2 0 .6 P o si tiv e c o n tr o l 3 2 0 .6 1 1 1 .8 8 4 .2 6 5 .2 1 4 0 .6 2 2 .8 5 4 .6 7 .2 3 .8 3 6 1 1 .2 4 .4 3 .8 N e g a tiv e c o n tr o l 2 8 5 .6 2 4 8 .4 5 2 2 1 0 9 5 3 2 .4 1 4 8 .6 1 4 6 .6 3 7 5 .2 6 0 3 0 1 .2 2 1 .2 7 9 .4 1 0 6 .8 a A p p lic a to r g ro u p a n d p o si tiv e c o n tr o l g ro u p t re a te d w ith d e lta m e th ri n /a m itr a z a t w e e kl y in te rv a ls f ro m d a y 0 t h ro u g h d a y 7 7 ; n e g a tiv e c o n tr o l g ro u p t re a te d w ith a m itr a z o n d a ys 0 , 1 4 , 2 8 , 3 5 , 4 9 , 6 3 a n d 8 4 f o r e th ic a l r e a so n s d u e t o h e a vy t ic k ch a lle n g e until day 1 post-treatment. The trichostrongyle egg counts were significantly less (P < 0.02) in the cat- tle treated using the applicator than were those in the untreated cattle on days 7, 14 and 21 of the trial. Insecticidal trial The eight cattle in the applicator group had a mean infestation of 293.8 horn flies before treatment with cyfluthrin from an applicator. After treatment, the fly counts on these cattle dropped to zero by day 1 post-treatment, remained at zero through day 7, and gradually increased from a mean of 7.0–493.8 during days 14–42 post-treatment (Table 3). The fly counts were significantly less (P < 0.001) on the cattle treated using the applicator than on the un- treated cattle on days 1 through 35 of the trial. Acaricidal trial Control of all tick species The five cattle in the applicator group had a mean infestation of 456.6 adult ticks before treatment with deltamethrin/amitraz from an applicator, after which their mean adult tick count fell with weekly treat- ments to 11.6 adult ticks by day 84 of the trial (Table 4). Similarly, the five cattle in the positive control group had a mean infestation of 416.2 adult ticks before treatment with deltamethrin/amitraz pour-on, after which their mean adult tick count fell with weekly treatments to 8.4 adult ticks by day 84 of the trial (Table 4). In contrast, the tick challenge in the negative control group was so heavy that the cattle in this group had to be treated on days 14, 28, 35, 49, 63 and 84 of the trial for ethical reasons. The adult tick counts were significantly less (P < 0.001) on both the cattle treated using the applicator and those treated by pour-on than were those for the cattle in the negative control group on days 14, 28, 35, 49, 63 and 84 of the trial. Furthermore, adult tick counts were significantly less (P < 0.05) on the cattle treated using the applicator than on those treated by pour-on on days 14, 21 and 42 of the trial. Control of Amblyomma hebraeum The five cattle in the applicator group had a mean infestation of 73.4 adult A. hebraeum (range 35– 114) before treatment with deltamethrin/amitraz from an applicator, after which the mean adult A. hebraeum count fell with weekly treatments to 2.2 adult ticks (range 0–5) by day 84 of the trial (Table 5). Similarly, the five cattle in the positive control group had a mean infestation of 74.6 adult A. hebraeum (range 47–100) before treatment with deltamethrin/amitraz pour-on after which the mean adult A. hebraeum count fell with weekly treatments to 3.4 adult ticks (range 2–5) by day 84 of the trial (Table 5). In contrast, the mean adult A. hebraeum count in the negative control group remained high, necessitating treatment with amitraz on days 14, 28, 35, 49, 63 and 84 of the trial for ethical reasons. The adult A. hebraeum counts were significantly less (P < 0.01) on both the cattle treated using the applicator and those treated by pour-on than were those for the cattle in the negative control group on days 14, 28, 49, 63 and 84 of the trial. Control of Rhipicephalus appendiculatus The five cattle in the applicator group had a mean infestation of 363.8 adult R. appendiculatus (range 295–430) before treatment with deltamethrin/ami- traz from an applicator, after which the mean adult R. appendiculatus count fell dramatically with weekly treatments to 0.6 adult ticks (range 0–2) by day 84 of the trial (Table 6). Similarly, the five cat- tle in the positive control group had a mean infes- tation of 320.6 adult R. appendiculatus (range 229– 362) before treatment with deltamethrin/amitraz pour-on, after which the mean adult R. appendicu- latus count fell with weekly treatments to 3.8 adult ticks (range 0–8) by day 84 of the trial (Table 6). In contrast, tick challenge with R. appendiculatus in the negative control group was so heavy that the cattle in the group had to be treated on days 14, 28, 35, 49, 63 and 84 of the trial for ethical reasons. The adult R. appendiculatus counts were signifi- cantly less (P < 0.001) on both the cattle treated using the applicator and those treated by pour-on than on the cattle in the negative control group on days 14, 28, 35, 49, 63 and 84 of the trial. Further- more, adult R. appendiculatus counts were signifi- cantly less (P < 0.05) on the cattle treated using the applicator than were those for those treated by pour-on on days 7, 14, 21, 28, 42 and 70 of the trial. DISCUSSION Since the advent of deer farming in the early part of the last century, it has become apparent that nem- atode parasites can cause severe disease and death in deer and, when infections are subclinical, they can lead to reduced productivity (Fletcher 1982; Mackintosh, Mason, Manley, Baker & Little- john 1985). Control of nematodes has relied on 48 Self-medicating applicator for control of parasites of wild and domestic animals treatment of deer with ivermectin administered by injection, as an oral drench or by topical application (Mackintosh et al. 1985; Rehbein & Visser 1997). More recently moxidectin (Waldrup et al. 1998) has been the anthelmintic of choice. The administration of anthelmintics to deer requires the use of han- dling facilities, and it induces stress in the animals and incurs labour costs. These constraints increase the costs of parasite control, result in losses of deer due to stress and/or handling accidents, and limit the frequency of treatments. Use of self-medicating applicators is an alternative delivery method for anthelmintics to deer, and has the advantages of eliminating stress in the deer and of minimizing costs in labour and facilities. There are numerous reports summarizing the adverse impact of nematodes on the productivity of cattle (Williams 1983; Gibbs & Herd 1986; Craig 1988; Hawkins 1993; Reinemeyer 1994; Clymer 2001; Vercruysse & Claerebout 2001). However, nematode control programmes are often difficult or impossible to implement economically on cattle farms which lack animal handling facilities (Herd 1988). Herd (1988) reviewed new anthelmintic delivery systems, such as medicated feed blocks and water dispensers, designed to simplify worm control in bovines by eliminating the necessity to handle animals or to put them in a crush to deliver the anthelmintic. He pointed out that, if these new delivery systems were to be used, profitable worm control strategies could be introduced to farms where lack of handling facilities had previously pre- vented any type of control programme. He argued that farmers want fast, simple and easy deworming programmes that involve minimal handling of cattle. Self-medicating applicators could provide such an anthelmintic delivery system for cattle producers. It is apparent from the cattle trial in Florida, that animals must feed readily from the trough to which the applicator is attached in order to receive an appropriate dose of anthelmintic. Steer no. 109 was unaccustomed to supplemental feeding and did not feed from the trough during the first day of the trial and, consequently, was only partially treated for tri- chostrongyles. It is recommended, therefore, that animals to be treated using a self-medicating appli- cator be allowed to acclimatize to feeding from a trough (or whatever receptacle to which the appli- cator is attached) before treatment commences. The results of the trial on the cattle ranch in Texas demonstrated that self-medicating applicators can be effective devices for the passive treatment of cattle for fly infestations. Other self-medicating devices have been developed for fly control on cat- tle. They include dust bags, cable back-rubbers and oilers. Dust bags typically consist of two burlap sacks one inside the other which contain insectici- dal dust (Adkins & Seawright 1967). Dust bags are suspended in a place which cattle frequent such as over gate openings, which force the animals to brush against the bags, dispensing the insecticidal dust from the burlap sacks onto their heads and backs. Dust bags require shelter and may be unsat- isfactory in humid climates (Foil & Hogsette 1994). Cable back-rubbers consist of a chain or barbed wire suspended between two posts, with the chain or wire wrapped with burlap sacks which are soaked with an insecticidal solution (Rogoff & Moxon 1952) which is typically an insecticide diluted with diesel or mineral oil (Dobson & Peterson 1963). Cattle passing under and contacting the back-rubbers are treated. The oiler consists of a tank containing insecticide which is attached to a post and from which is suspended a rubbing element such as a rope or a mop-like device (Barlow & Surgeoner 1979). When cattle rub the element, small quanti- ties of insecticide are delivered to it, some of which is passed on to the cattle. The results of the trial on the research farm in South Africa demonstrated that self-medicating applica- tors can be effective devices for the passive treat- ment of cattle for tick infestations. Other self-med- icating devices have been developed for tick con- trol on animals. They include the Duncan applicator and the ‘4-poster’ device. The Duncan applicator consists of a drum-like base incorporating a feed bin, with an acaricide container on top of a treat- ment column rising from the centre of the bin (Dun- can & Monks 1992). The Duncan applicator has been used to control ticks on eland (Taurotragus oryx), African buffaloes (Syncerus caffer) and cattle using the acaricide flumethrin (Duncan & Monks 1992; Duncan 1992). The ‘4-poster’ device consists of a central feed bin with a feeding/application sta- tion on each side of the bin, each station consisting of one bait port and two vertical pesticide-impreg- nated application rollers (Pound, Miller, George & Lemeilleur 2000). The ‘4-poster’ device has been tested experimentally in the United States as a pas- sive method for control of ticks on white-tailed deer (Odocoileus virginianus) using the acaricide ami- traz (Pound, Miller & George 2000). The results of this and other studies have demon- strated that the concept of passive delivery of treat- ments to animals using self-medicating applicators has practical potential in the control of gastroin- 49 M.J. BURRIDGE et al. testinal nematodes, flies and ticks. 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