THE EFFICACY AND USE OF AMITRAZ FOR THE CONTROL OF HOG LICEl

THE EFFICACY AND USE OF AMITRAZ FOR THE CONTROL OF HOG LICEl R. E. Williams' and S. M. Gaafar' Purdue University West Lafayette, IN 47907 Abstract: An evaluation was made of three concentrations of amitraz TAKTICil' 12.5% emulsifiable concentrate for controlling hog lice, Haematopinus suis (L.). Comparisons were made of single treatments and two treahnents 14 days apart. A follow-up study was conducted on three plivately owned farrow to finish swine facilities using a 0.05% rote of amitraz in an integrated treatment program. In the initial study, all rates tested (0.025%, 0.05%. and 0.1 %) reduced lice numbers on animals. However, a second treatment, at 14 days, was necessary to provide 1(}() percent control. In the follow-up study, the integrated treatment program consisted of an initial whole-herd treatment phase followed by scheduled treatments applied in conjunction with daily management of the operations. Total hog lice control ranged from 20 weeks at one fann through 53 weeks at another farm. Key \Vords: Amitraz, hog lice, Haematopinus suis. J. Agric. Entomol. 5(1): 29-34 (January 1988) Hog lice, Haematopinus suis (L.), along with sarcoptic mange mites, Sarcoptes scabiei val'. suis (De Geer), are generally recognized as the most economically important ectoparasites of swine. In a sulvey of Indiana veterinarians, it was estimated that 51.5% of the farms visited had swine infested with lice (Wooten Saadi et al. 1987). It is estimated that $40 million is lost annually in the United States by producers due to hog lice alone (Anonymous 1979). A 1979 suivey of pesticide use in Nebraska indicated that 75% of pesticides used on swine were for hog louse conb'ol (Campbell and Kamble 1981). In a survey of market-weight swine in Indiana conducted during 1980 to 1981, hog lice were found on 18% of all animals examined (Wooten-Saadi et al. 1987). Hog lice pass their entire life cycle on the host. Their blood-sucking activity results in an apparent irritation and discomfort to swine. Davis and Williams (1986) demonstrated physiological changes (blood chemistry) in growing pigs due to hog lice infestation. Conb'olling hog lice on swine is directed at 1) eliminating both active adults and nymphs from the animals, 2) eliminating nymphs hatching from attached eggs, and 3) eliminating re~introduction of lice into the herd. Conb'ol should also be directed toward prevention of transmission of lice infestations not previously controlled in a herd. These steps of treatment and control should be integrated with the routine daily tasks of the producer. Various insecticides have been used for hog lice control (Williams et al. 1980) but many of these compounds have since been removed from the market 01' are marginal in effectiveness. This report describes the use of a new insecticide, for controlling hog lice in swine. Amitraz (TAKTICo1I) is a biazapentadiene which has shmvn high parasiticidal I Contribution from the Departments of Entomology and Veterinary Microbiology, Pathology {lnd Public Health, Joumul Paper No. 11,387, Purdue University, Agricultural Experiment Station, West Lnfnyette, IN 47907. l\ccl'pted for publication 22 FebnlUry 1988. Fee pllid for early publication. Z Depruiment of Entomology. 3 Depurtml.!nt of Veterinary Microbiolo{,,)', Pathology and Public Hcnlth. 29

30 J. Agric. Entomol. VoL 5, No. 1 (1988) activity against various ectoparasites of livestock (Curtis 1985). This report is based on two studies: an initial study evaluating different rates of active ingredient and comparing single and double treatments; and a follow-up study on commercial swine herds in Indiana establishing an integrated program using amitraz to control hog lice. The control of sarcoptic mange in these studies was described by Ganfal' et a!. (1986). MATERIALS AND METHODS Study I Forty pigs, averaging 7.4 kg each, were divided into 8 similar weight groups of 5 pigs each and placed in separate pens. The treatments evaluated were amitraz 12.5% emulsifiable concentrate (Ee) sprays at 0.025%, 0.05% (labeled rate), and 0.1% active ingredient (a i) comparing a single treatment (3 groups) with two treatments (3 groups). Two groups were used as untreated controls and sprayed with inert carrier solvent at 0.05% as a single treatment and two treatments. In the groups given two treatments, the second treatment was made 14 days after the initial spraying. Treatments were applied with a 7.57 liter B & G hand-held pressure sprayer equipped with a Teejet #6502 fan-pattern nozzle at a rate of 1 to 2 liters of finished spray per animal in each group. Thorough body coverage was achieved including the inner surface of the ear pinna, the axillae and groin. Population assessment of hog lice was obtained by making total body counts on each animal. Louse infestations were established by placing 50 to 100 lice pel' animal 3 weeks pre-treatment. After pre-treatment counts, louse populations were monitored on the pigs twice weekly for 4 weeks. Louse count data obtained were statistically analyzed in a one-way analysis of variance. Mean counts each day were compared using Duncan's New Multiple Range Test (P < 0.05) (Duncan 1955). Sudy 2 In this study, three commercial farrow to finish swine operations were selected and a treatment program using amitraz was devised to control the hog lice on the animals at these farms. The swine herds used in this study were selected because they had a history of problems with hog lice and sarcoptic mange during previous years. Although these herds had been previously treated periodically with various chemicals, no animals had been treated for at least 2 months prior to initiation of the present trials. The spray material for each fann was prepared f.rom a stock solution containing 12.5% ai arnitraz. Before spraying, all feeders and waters were removed, emptied or tightly covered to prevent contamination. All animals in each herd were initially sprayed with an emulsion of 0.05% ai in water. A second application of the same concentration of spray was made 7-14 days later. All animals were thoroughly sprayed to runoff with particular attention being given to the ear pinna, the axillae and groin. Approximately 2 liters of spray material were used on each animal with more solution used on larger sows and boars and less on the smaller animals. Newborn pigs, up to 3 weeks of age, were dipped in the same concentration of spray solution. The premises, including the walls, pen dividers, and equipment in the pens, were also sprayed. The equipment lised fol' spraying consisted of power sprayers with coarse nozzles and wand spray handles.

W1LLlAMS and GAAFAR: Amitraz for the Control of Hog Lice 31 Following the two comprehensive sprayings, a maintenance prevention program was initiated in each herd. This program focused on preventing infestation of the young piglets. At weaning and before piglets from various litters were mixed together, they were dipped in a 0.05% ai emulsion of amitraz. The dip solution was renewed after each 50 piglets. Boars were also sprayed once every 3 months. New animals added to the herd during this study were isolated and sprayed twice (at 7 10 day intervals) before being placed with the rest of the animals. Sows in late pregnancy were sprayed as they were being moved to the farrowing crates and again in the farrowing pen after weaning their piglets and before transferring to the gestation stalls. Farm A, located in White County, Indiana, had approximately 2800 animals. All the animals in this herd were sprayed tv.ice with amib az. The first spraying was on 20, 23, and 24 May 1983 followed by a 'econd treatment on 27, 31 May and 1 June 1983. Farm B, located in Carroll County, Indiana, had approximately 2300 animals. The first spraying was on 20 June 1984 and the second spraying was made on 5 July 1984. Fann C, located in Jasper County, Indiana, had approximately 2400 animals. The first spraying was on 26 June 1984 and the second spraying on 10 July L984. Before the initial sprayings, 20 animals from each farm were examined for hog lice. Five animals were randomly selected from each of four age groups of pigs (sows, nursery stock, early feeder pigs, and late feeder stage pigs). Lice counts consisted of total body counts on each animal. After the second spraying of the animals examinations for the presence of lice were made on 20 animals, chosen as above, at 1 week, 2 weeks and monthly thereafter until July 1985. RESULTS AND DISCUSSION Study I The mean numbers of hog lice from each treatment group over the duration of the study are shown in Table 1. It is evident from the data that amitraz was effective in reducing lice numbers on the animals treated with each spray concentration. However, after the first spray treatment, live lice were observed on the animals at 7 days post treatment in all amitraz treatment groups. The majority of these lice were nymphs, probably having hatched from eggs after the initial treatments were made. In each nmitraz group where a second treatment was made, no lice were found on the pigs after tv.'o weeks. Lice numbers in the groups where one treatment was made continued to increase in numbers for the remainder of the trial. However, pigs in all three groups treated once still had fewer lice on them than did pigs in the untreated groups after 4 weeks. Study 2 Control of lice was achieved at each fann following the initial treatments (Table 2). On Farm A, all the animals examined before treatments had lice infestations. It was 20 weeks later before lice were again found on the animals sampled. Lice were found on most of the sampling dates thereafter. At Farm B, lice first reappeared at week 24, on two lactating sows, and were observed again at weeks 47 and 55. On Farm C, total lice control was achieved for the duration of the 53 weeks during which counts were made.

32 J. Agric. EntomoL Vol. 5, No. I (1988) Table 1. Mean numbers of Haematopinus suis on swine treated with different concentrations of amitraz. 8 Single Treatment 1 and 14 Day Treatment Days Amitraz Amitraz Amitraz Amitmz Amitraz Amitraz Post-trt 0.025% 0.05% 0.1% Control 0.025% 0.05% 0.1 % Control o 13.00b 21.00b 6.40 19.0bc 24.6bc 16.20b 19.8ab 38.6c 3 00 00 00 9.0b On 0. 0. 18.6c 7 6.4.b 1.2. 2.4. 17.6b 2.2n 0.6. 1.8. 44.8c to 21.4.b 12.6.b 1.60 32.0b 20.0.b l3.4.b 5.8.b 109.4c 14 34.4.b 21.8.b 5.4. 66.0b 34.0nb 17.6.b 25.4.b 247.6c 17 35.2. 35.8. 12.4. 95.6b 0. 00 00 358.0c 21 36.8. 87.8b 21.8a 141.0c 0. 0. 0. 443.2d 24 38.5.b 67.2b 23.6.b 141.0c 0. 0. 0. 495.8d 27 39.6. 62.2. 19.2. 202.4b 0. 0. On 51O.0c Menns within rows followed by the some letter lire not signilicnntly different (P < 0.05) - Duncan's New f\'lultiplc Range Test. In these studies, it was demonstrated that amitraz is an effective insecticide for controlling hog lice on pigs, but only if 8P1>lied twice with a 7-14 day interval between sprayings and if the maintenance program is strictly followed. This interval is needed to allow for nymphs to hatch from eggs. In the commercial farms used in Study 2. the maintenance program was effective in providing longer term lice control. It is essential, however, that the maintenance program be followed closely to insure proper control of lice. Single applications to new animals brought into the herds at Farms 1 and 2 probably led to the reinfestation of the herds. Comparisons of pre-treatment and post-treatment production records at these farms, as presented by Gaafar et al. (1986), showed 10-15 days earlier maturity in finishing pig market weight, an average increase of 2.1 weaned pigs/litter, and decreases in piglet processing and nursing mortality following implementation of the amitraz treatment program for controlling both lice and sarcoptic mange mites.

WILLIAMS and GAAI"AR: Amitraz for the Contl'Ol of Hog Lice 33 Table 2. Mean percentage of swine from commercial farms infested with Haematopinus suis following treatments with amitraz. Farm A Farm B Farm C % Infested % Infested % Infested Week With Lice Week With Lice Week With Lice 0 100 0 20 0 5 3 0 3 0 3 0 4 0 4 0 4 0 8 0 6 0 7 0 12 0 10 0 11 0 16 0 15 0 16 0 20 10 20 0 19 0 24 5 24 10 24 0 28 20 26 0 28 0 31 35 32 0 32 0 36 0 35 0 36 0 39 40 43 0 40 0 44 25 47 40 44 0 49 5 51 0 48 0 53 35 55 10 53 0 57 40 62 60 66 0 70 35 75 60 79 30 82 35 87 20 92 60 99 30 103 20 107 15 111 0 REFERENCES C1TED Anonymous. 1979. Proceedings of EI workshop on livestock pest management: rib llssess nationn] research and extension needs for integrated pest management of insects, ticks, and mites affecting livestock and poul!.ry. Kansas Stilte University, Manhattan, Kansas. 322 pp. Campbell, J. 8., and S. T. Kamble. 1981. A survey of insecti(~ide use against livestock pests in Nebraska-1979. Report no. 11, Department of Entomology, Univ. Nebraska-Lincoln. Curtis, R. J. 1985. Amitraz in the control of non-ixodid ectoparasites of livest.ock. Vet. Parasito!. 18: 251-264. Davis, D. P., and R. E. Williams. 1986. Inl1uence of hog lice, Hnematopinus suis, on blood components, behavior, weight gain and feed efficiency of pigs. Vel Parasito!. 22: 307-314. Duncan, D. 8. 1955. Multiple range and multiple F tests. Biometrics 11: 1-42. Gaafar, S. M., J. M. Arends, A. Hogg, l<. H. Holscher, and R. Eo Williams. 1986. An integrated program using TAKTIC'll to conl,rol mange in swine. J. Agric. Entomol. 3: 374-381.

34 J. Agric. Entoroo!. Vol. 5, No. 1 (1988) Williams, R. E., T. L. McCain, and A. Teklehaimanot. 1980. Survey of pesticide usage by livestock producers in Indiana. Research Bulletin 964, Purdue Univ. Agric. Exp. StO" West Lafayette. 35 pp. Wooten-Sandi, E. L., C. A. Towell-Vail, R. E. Williams, and S. M. Gaafar. 1987. Incidence of Sarcoptes scabiei (DeGccr) (Acariformes: Sarcoptidae) and Haematopinus suis (L.) (Alloplum: Haematopinidae) on swine in Indiana. J. Eeon. Entomol. 80: 1031-1034.