Efficacy of ivermectin against internal parasites in dromedaries (Camelus dromedarius)

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1 Rev. sci. tech. Off. int. Epiz., 1989, 8 (1), Efficacy of ivermectin against internal parasites in dromedaries (Camelus dromedarius) B. ROBIN *, K. KÖNIG ** and M.D. ANSTEY *** Summary: Three trials were undertaken in Egypt, Morocco, and Niger under controlled test conditions to evaluate the efficacy of ivermectin in dromedaries against a range of important gastro-intestinal nematodes. Thirty-two naturally infested dromedaries were included in these studies; within pairs, dromedaries were randomly allocated to a treated or a control group based on body weight. Treated animals received a single subcutaneous injection of ivermectin 1.0% w/v solution at adose of 200 \.g/kg. Animals were slaughtered 14 to 29 days after treatment and the parasites remaining were recovered for identification and enumeration. Overall statistical analysis performed for each parasite demonstrated significant (P < 0.05) reductions of adult stages of Ostertagia spp., Haemonchus spp., Trichostrongylus spp., Nematodirus spathiger, Oesophagostomum spp. and Chabertia ovina. Although no Cooperia spp. were recovered from treated animals, the efficacy was not significant due to the variability of infection amongst the controls. Based on these results it is recommended that dromedaries be treated at least twice a year with ivermectin, once during the dry season and once at the beginning of the winter. KEYWORDS: Anthelmintics - Antiparasitic agents - Cephalopina - Dromedary - Gastro-intestinal nematodes - Ivermectin. The dromedary is found mostly in arid or semi-arid desert areas of northern Africa, Arabia and India. This animal is well adapted to those conditions and can survive as a producer of meat, milk and by-products from natural resources which might otherwise be unusable. Although these environmental conditions would seem to be unfavourable to parasite transmission, fifty different helminth parasites have been reported in dromedaries (3). Infection usually takes place during the rainy season when grass is the main feed. Many anthelmintics used in cattle and sheep for the control of gastro-intestinal (g.i.) nematodes have also been tested in dromedaries. In most of these studies, efficacy was calculated on the basis of reduced faecal egg counts compared with control animals (3, 4, 5, 6, 8, 12, 13, 14). * Merck, Sharp & Dohme Research Laboratory (MSDRL), 43, rue de Villiers, F Neuilly-sur- Seine Cedex, France. ** MSDRL, Kathrinenhof, Walchenseestrasse 8-12, D-8201 Lauterbach, Federal Republic of Germany. *** MSDRL, Hertford Road, Hoddesdon EN11 9BU, Herts, United Kingdom.

2 156 The antiparasitic compound ivermectin has been tested in most domestic animals and is active against a wide range of nematodes and arthropods (2). Only a few studies are reported in Camelidae (1,7). To evaluate the efficacy of ivermectin in dromedaries against a range of important gastro-intestinal nematodes, three trials were undertaken in Egypt, Morocco and Niger under controlled test conditions. MATERIALS AND METHODS Thirty-two naturally infested dromedaries were included in these studies to evaluate the efficacy of ivermectin administered subcutaneously at 200 itg/kg body weight against g.i. nematodes; trial details are presented in Table I. TABLE I Details of trials Location No. of animals Ivermectin Controls Age (yrs) Sex Weight (kg) Management Niger 5 5* adult young 6 female 4 male Penned by treatment group outdoors Morocco male 3 female ** Individually penned indoors Egypt male ** Individually tied outdoors * Vehicle-treated controls ** Estimated according to a formula devised by the Indian Army Veterinary Corps (Anon., 1964) Within pairs, dromedaries were randomly allocated to a treated or a control group based on body weight. Treated animals received a single subcutaneous injection of ivermectin 1.0% w/v solution (Ivomec* Injection) at a dose of 200 itg/kg. Animals were fed locally-available roughage ad libitum, supplemented with barley or bean haulms (in two trials). Water was either freely available or given at intervals of 5 or 6 days. Faecal samples were collected from each animal before the start of each trial, on the day of treatment (Day 0), after 7 and 14 days, and at slaughter. Nematode eggs were counted by using the Stoll or modified McMaster techniques. Both treated and control dromedaries were slaughtered 14 to 29 days after treatment and the remaining parasites recovered for identification and enumeration. The abomasum, small intestine, large intestine, lungs and trachea were removed separately. After thorough washing of the intestinal mucosae, the contents were sieved separately with repeated washing and the residues made up to a fixed volume with * Ivomec: Trademark of Merck and Co., Rahway, N.J., USA.

3 water. Parts or the total abomasal mucosa were removed and digested with pepsin and hydrochloric acid. In the trials undertaken in Morocco and Niger, the first six metres of the small intestine were similarly digested, the material collected, formalinised and retained for counting. Worms were identified and counted in aliquots or total collections as appropriate. Differentiation of species was performed by examination of aliquots where possible. The lungs were opened along the bronchi and examined for the presence of lungworms. In the trials carried out in Egypt and Niger, the lungs were floated overnight in warm saline for further recovery of any remaining worms. The head of each animal was cut longitudinally and the nasopharynx and the turbinate bones were examined to recover Cephalopina titillator larvae. Worm counts at post-mortem were transformed by the transformation log (x + 1). Geometric means and percent efficacy of treated groups relative to the controls were determined. Statistical analyses on the transformed data were undertaken in all cases, using the unequal variance t-test (11). When one of the groups had zero variance, this variance was replaced by the non-zero variance of the other group and the t- value calculated. Overall statistical analysis for each parasite was carried out, provided that data was available from at least two trials, using the modified Friedman test (10). 157 RESULTS AND DISCUSSION No adverse reactions attributable to treatment were observed in any animal up to four hours after treatment. In one trial (Niger) a reaction was seen at the site of injection in some treated animals and in controls which had been treated with the vehicle. This reaction (plaque-like thickenings or swelling) disappeared spontaneously within three or four days. In other experiments conducted in the Canary Islands, Egypt and Tunisia, it was observed at the time of treatment that a few dromedaries presented some reaction at the injection site but all these adverse reactions resolved quickly without therapy and were acceptable to the owners (unpublished data). Mean strongyle faecal egg counts are presented in Table II. All control animals were positive at each sampling. At slaughter the reduction in the treated group compared with controls was 99%. TABLE II Number of strongyle eggs per gram of faeces (geometric means*) Unmedicated Ivermectin 200 ng/kg subcutaneously, once % of reduction Before treatment At slaughter * Based on log (x + 1)

4 158 TABLE III Efficacy of ivermectin administered subcutaneously at 200 ig/kg body weight against gastro-intestinal nematodes and nasal bots of dromedaries for each study, as recorded at slaughter Parasite Stage Trial Geometric mean Efficacy burden % Control Ivermectin Camelostrongylus A M 1, <0.001 mentulatus C. mentulatus I M <0.05 Ostertagia spp. A M n.s. A E n.s. Haemonchus A M n.s. contortus H. longistipes A E <0.001 A N 2, <0.01 Cooperia spp. A M n.s. Cooperia spp. A E n.s. C. pectinata A N n.s. Trichostrongylus axei A M n.s. T. colubriformis A M n.s. A N n.s. T. colubriformis A E < probolurus T. probolurus A M <0.001 T. vitrinus A M n.s. Impalaia tuberculata A N <0.05 Nematodirus A M <0.01 spathiger A E n.s. Strongyloides A E papillosus Oesophagostomum A M <0.01 venulosum O. columbianum A N <0.05 Chabertia ovina A M n.s. A E n.s. Trichuris globulosa A E _ + T. cameli T. globulosa A M n.s. A N n.s. Cephalopina I. N n.s. titillator I M (nasal bot) 100 n.s. A: adult 1: immature n.s.: not significant E: Egypt M: Morocco N: Niger

5 No lungworms were recovered from any animal at necropsy. Table III summarises the geometric means, percent efficacy and significance value for each parasite and for each study. For parasites found in at least two studies, the overall geometric means, percent efficacy and significance value are presented in Table IV. 159 TABLE IV Overall efficacy against parasites found in at least two trials Geometric mean Parasite Stage burden Control Ivermectin Efficacy Ostertagia spp. A <0.01 Haemonchus spp. A <0.001 Cooperia spp. A n.s. Trichostrongylus spp. A <0.05 Nematodirus spathiger A <0.05 Oesophagostomum spp. A <0.001 Chabertia ovina A <0.01 Trichuris spp. A n.s. Cephalopina titillator I n.s. A: adult I: immature n.s.: not significant The following species were significantly (P < 0.05) reduced in treated animals by more than 95%: adult and immature Camelostrongylus mentulatus (Morocco), adult Haemonchus longistipes (Egypt, Niger), Trichostrongylusprobolurus (Morocco), Impalaia tuberculata (Niger), Oesophagostomum venulosum (Morocco) and O. columbianum (Niger). Overall statistical analysis performed for each parasite demonstrated significant (P < 0.05) reductions of adult stages of Ostertagia spp., Haemonchus spp., Trichostrongylus spp., Nematodirus spathiger, Oesophagostomum spp. and Chabertia ovina. Although no Cooperia spp. were recovered from treated animals, the efficacy was not significant due to the variability of infection amongst the controls. Larval stages of Cephalopina titillator were found in animals from two studies (Niger and Morocco); an overall efficacy of 87.1% was defined, although too few were present to make a valid conclusion of efficacy. For this parasite more experiments with a large number of infested animals should be conducted to evaluate the efficacy of ivermectin, taking into account the results obtained against larvae of Hypoderma spp. and Dermatobia spp. in cattle and Oestrus ovis in sheep (2). Results of these experiments confirm that the injectable solution of ivermectin is clinically acceptable when administered subcutaneously to dromedaries at a dose rate of 200 jttg/kg body weight. Its efficacy was demonstrated against the most common

6 160 nematodes of dromedaries in Egypt, Morocco and Niger. In addition to these studies, the efficacy of ivermectin against Sarcoptes scabiei var. cameli was well demonstrated by several authors (7, 9) and in our own studies from Egypt (not yet published). It is recommended that dromedaries be treated at least twice a year with ivermectin, once during the dry season in order to decrease contamination of grazing land and once at the beginning of winter to reduce sarcoptic mite infestation which generally becomes a problem at this time. ACKNOWLEDGEMENTS The authors wish to thank: Prof. Dr S. Afram Michael, Prof. Dr Mohamed Refaii, Dr Gamal Helmy, Dr Mamdouh Girgis, Dr Emad Adel, Dr Ahmad Anwas from Egypt; Dr A. Dakkak, Dr H. Ouhelli from Morocco and Dr P. Tager-Kagan (in memoriam) from Niger who were instrumental in setting up these studies. Thanks are also due to Mr P. Taranchon (MSDRL, France) for his technical assistance and Ms M.C. Durette-Desset (Laboratoire de Zoologie, Muséum d'histoire Naturelle, Paris, France) who identified the species of Haemonchus and Impalaia. * REFERENCES 1. BOYCE W., KOLLIAS G., COURTNEY CH., ALLEN J. & CHALMERS E. (1984). - Efficacy of ivermectin against gastrointestinal nematodes in dromedary. J. Am. vet. med. Ass., 185 (11), CAMPBELL W.C (1985). - Ivermectin: an update. Parasitology Today, 1, DAKKAK A. & OUHELLI H. (1987). - Helminths and helminthoses of the dromedary. A review of the literature. Rev. sci. tech. Off. int. Epiz., 6 (2), GRABER M. (1966). - Etude dans certaines conditions africaines de Paction antiparasitaire du thiabendazole sur divers helminthes des animaux domestiques. II. Dromadaire. Rev. Elev. Méd. vét. Pays trop., 19, GRABER M. (1969). - Essais de traitement du parasitisme gastro-intestinal du dromadaire au moyen du tétramisole. Premières observations. Rev. Elev. Méd. vét. Pays trop., 22, HIGGINS A. (1986). - The camel in health and disease. Baillière & Tindall, London, IBRAHIM M.S., MOHAMED A.R., EL-BALKEMY F.A., OMRAN H. & EL-MEKKAWI M.F. (1981). - Studies on the relation between the effect of Ivomec as a parasitic control and the general health condition in camels. Zagazig University, Egypt, Res. Bull. No. 375, Oct LODA K.R., RAISINGHANI P.M. & KARWASRA R.S. (1977). - Chemotherapeutic trials of some anthelmintics against helmintic parasites in camels. Indian J. Anim. Sci., 47, OPPERMAN R.R. (1985). - Treatment of sarcoptic mange in dromedary camel. J. Am. vet. med. Ass., 187, PuRi M.L. (1965). - On the combination of independent two sample tests of a general class. Review Int. Stat. Inst., 33,

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