ANTHELMINTIC TREATMENT OF EQUIDS : CAPABILITIES AND LIMITATIONS CRITICAL TESTS OF NINE ANTHELMINTIC AGENTS ON PONIES

Transcription

1 ANTHELMINTIC TREATMENT OF EQUIDS : CAPABILITIES AND LIMITATIONS CRITICAL TESTS OF NINE ANTHELMINTIC AGENTS ON PONIES M. Pecheur To cite this version: M. Pecheur. ANTHELMINTIC TREATMENT OF EQUIDS : CAPABILITIES AND LIMITATIONS CRITICAL TESTS OF NINE ANTHELMINTIC AGENTS ON PONIES. Annales de Recherches Vétérinaires, INRA Editions, 1981, 12 (3), pp <hal > HAL Id: hal Submitted on 1 Jan 1981 HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

2 ANTHELMINTIC TREATMENT OF EQUIDS : CAPABILITIES AND LIMITATIONS CRITICAL TESTS OF NINE ANTHELMINTIC AGENTS ON PONIES M. PECHEUR Faculty of Veterinary Medicine, 45, rue des V6t6rinaires, 1070 Brussels Service de Parasito%gie : Dir. Prof Dr. L. Pouplard Résumé POSSIBILITÉS ET LIMITES DU TRAITEMENT ANTIHELMINTHIQUE DES ÉQUIDÉS. TESTS CRITIQUES DE NEUF ANTIHELMINTHIQUES SUR PONEYS. - Il existe actuellement de très bons antihelminthiques permettant d éliminer à plus de 90 % les nématodes gastro-intestinaux des équidés. Cette constatation provient de la comparaison par la méthode du test critique de 9 antihelminthiques testés chez le poney : les Embonate de Pyrantel 19 mg/kg, Oxfendazole 10 mg/kg, Mebendazole 10 mg/kg, Albendazole 5 mg/kg, Dichlorvos 40 mg/kg, Thiabendazole 44 mg/kg, Fenbendazole 7,5 mg/kg, Cambendazole 20 mg/kg, Parbendazole 7 mg/kg. Six à neuf poneys ont été traités avec chacun des produits. En tenant compte de l activité totale vis-à-vis des différents helminthes, il n y a pas de différence significative entre les 9 médicaments. A l égard des Trichonematidae ou petits strongles, nématodes les plus nombreux et les plus courants chez les équidés, l analyse statistique permet de classer les neuf produits en trois groupes : le groupe 1 renfermant les plus efficaces : Oxfendazole et Pyrantel ; le groupe 2 : Thiabendazole, Mebendazole, Albendazole et Cambendazole ; le groupe 3 : Parbendazôle, Fenbendazole et Dichlorvos. Vis-à-vis des grands strongles ( Strongylus spp. les variations dans les résultats sont parfois considérables, les Pyrantel et Dichlorvos donnent les meilleurs résultats. Contre Oxyuris equi, les Mebendazole et Dichlorvos sont les produits à recommander ; contre Strongyloides westeri, le Cambendazole ; contre Parascaris equorum, le Pyrantel, le Cambendazole, le Dichlorvos ; contre Gasterophilus equi, les Dichlorvos, Mebendazole + Trichlorfon, Pyrantel + Trichlorfon. Aucune action des 9 produits vis-à-vis de Tüchostrongylus axei, Anoplocephala sp. et Habronema sp. n a été notée. Anti-parasitic compounds are probably among those which have undergone the most dramatic developments in recent years. Some twenty years ago, phenothiazine was virtually the only anthelmintic agent available. Its activity was very limited, however, and it had a high toxicity level. Discovery of thiabendazole opened up a new era for parasite control, and since then the list of new anthelmintic drugs has considerably expanded, so that drugs are currently available which are particularly effective. When we reviewed numerous publications dealing with activity of such drugs and reporting efficiency rates often near 100 %, we wondered how parasites can still present a problem. In fact, parasite control remains

3 quite complicated, and it is important to be aware of both capabilites and limitations of any anthelmintic treatment. Results reported in literature do not always agree with the activity spectrum announced in insert leaflets that come with the drug package. At times, these contradictions can be quite disturbing. It would take too long to analyse here reasons for such contradictions, but we should note that many efficiency trials have been based on nematode egg counts in faeces before and after treatment. Such a method, although it has some value, is fraught with many pitfalls. The number of eggs passed by an animal may vary considerably depending on time of infection, season of the year, state of immunity of the host animal, genus and species of nematodes involved, cyclical activity of the parasite, and many other factors. Even if faecal tests remain negative for a period of time after treatment, it may admittedly be due to real anthelmintic activity of a compound, but also to a mere inhibition of the egg laying process in the parasite. On the other hand, re-emergence of reproductive forms after a certain time may just as well be due to a resumption of the egg laying process as to a re-infection. Results of faecal counts should always be subjected to stringent critical tests. In order to give an accurate picture of the effectiveness of various anthelmintic compounds available on the Belgian market, we used them in critical trials on ponies (Raynaud, 1972). Critical trial consists of counting eliminated worms in faeces after treatment and non-eliminated worms after necropsy. Materials and Methods Animals The ponies used in our study were from one to ten years old and came from various parts of this country where they had become naturally infected. At least six of them were treated with each of the nine drugs tested, and a total of 69 animals were included in this study. Three days before administering the drug, each pony was placed in an individual box where droppings could be easily collected. Drugs The following drugs were used, and doses were those recommended by manufacturers : 1. Pyrantel embonate (strongid-p, Pfizer) : 19 mg/kg (in paste form), to 9 ponies. 2. Oxfendazole (Systame XR Wellcome) : 10

4 mg/kg (in liquid suspension), to 9 ponies. 3. Mebendazole (Telmin R, Janssen Pharmaceutical : 10 mg/kg (in past form), to 7 ponies. 4. Albendazole (Valbazen, Smith Kline) : 5 mg/kg (in liquid suspension), to 9 ponies. 5. Dichlorvos (Equigard Shell) : 40 mg/kg (in pellet form), to 6 ponies. 6. Thiabendazole (MSD) R: 44 mg/kg (in paste form), to 6 ponies. 7. Fenbendazole (Panacur R, Hoechst) : 7.5 mg/kg (in liquid suspension), to 7 ponies. 8. Cambendazole (Noviben, MSD) : 20 mg/kg (paste form), to 8 ponies. 9. Parbendazole (Helmatac l, SK Et F) : 7 mg/kg in two doses of 3.5 mg/kg each, two days in succession (in powder form), to 8 ponies. Worms numeration After administration of the drug, faeces were individually collected every 24 hours for a period of 96 hours. Daily collections were diluted in water so as to obtain a homogenous mixture. An aliquot (1/10 in this case) was fixed in alcohol-glycerin. All ponies were slaughtered 4 days after completion of treatment. Methods used for collection of digestive tract parasites have been described (Pecheur et al., 1979). Quantities examined varied between 1/10 and 1/100 for faeces as well as for stomach and gut contents. Parasite identification Helminth identification was based mainly on Lichtenfels determination key (1975). Larvae were not identified. of Tiichonema spp. (L4) Adult Trichonema with no buccal capsule were classed as undetermined adult Trichonema. Migrating larvae of Strongylus vulgaris, Strongylus equinus and Strongylus edentatus were not looked for since the anthelmintic doses normally used are not active against these forms. Statistical analysis Data were analysed by one-way analysis of variance. t-test was used to compare means of treatments. Results For each anthelmintic, the number of worms counted in faeces (worms eliminated) and the number of worms counted after slaughter (worms not eliminated) are shown in table 1. Except for Parbendazole, activity of each agent is mostly similar. Trichonema spp. are the only nematodes to be evenly distributed in ponies, and be present in large numbers. This is why a statistical analysis could be made for this group of parasites. Tables 2, 2A, 2B, 2C, 2D show results obtained for this particular group. Statistical analysis shows Oxfendazole to be significanlty more active than Parbendazole (P < , Dichlorvos (P < 0.01) and Cambendazole and Fenbendazole (P < 0.1 ). On the other hand, Pyrantel embonate was significantly more active than Parbendazole (P < 0.01) and Dichlorvos (P < 0.1 Mebendazole and Thiabendazole were significantly more active than Parbendazole (P < 0.05) and Dichlorvos (P < 0.1). Cambendazole and Albendazole were significantly more active than Parbendazole (P < 0.05). Fenbendazole is more active than Parbendazole (P < 0.011, and no significant difference was noted between Parbendazole and Dichlorvos. To sum up, based on their activity against Trichonema spp., anthelmintic agents may be classed in three groups : Oxfendazole and Pyrantel embonate have the highest activity. A second group would include Cambendazole, Mebendazole, Thiabendazole and Albendazole. Finally, we would place Fenbendazole, Parbendazole and Dichlorvos in the third group. Other nematodes Apart from activity against Trichonema spp., it is difficult to compare accurately activity of the various anthelminintic drugs studied here, for presence and population of certain species vary widely from one animal to another. Pyrantel embonate eliminated all 420 Strongylus vulgaris found in three ponies (respectively 100, 120 et 200). Three ponies had Strongylus edentatus : one had 10 which were all passed, another had 450 and passed

5

6

7

8 420, the third had 10 and failed to pass any (table 3A1. In one pony with Oxyuris equi, half the parasites present were passed (table 3B). Oxfendazole failed to eliminate the 100 Strongylus vulgaris in the only infected pony. Out of 3 ponies with pinworms, 32 % were eliminated by this drug (tables 3A, 3B). Rate of efficacy of Mebendazole against Strongylus vulgaris was 100 % in two ponies, but 0 % in two others (table 3A). Four ponies had pinworms, and 93 % were passed (table 3B). Activity of Albendazole ranged from to 100 % in 4 ponies with Strongylus vulgaris. One pony had 100 Strongylus edentatus which were not eliminated (table 3A). Efficacy was 48 % in the two ponies which had pinworms (table 3B). In the Dichlorvos group, one pony had 100 Sirongylus vulgaris all of which were eliminated (table 3A). Six ponies had pinworms, and elimination rate reached 91 %. This was the only group where Parascaris equorum was found : one pony had 200, and they were all eliminated (table 3B). To say that Thiabendazole was not active against large strongyles would be an exaggeration, since animals treated with this drug had only a few of these : only two ponies had 30 and 10 Strongylus respectively, and these were not eliminated (table 3A). One animal in

9 this group had L4 pinworms, of which only 150 were passed (table 3B1. If we consider the group treated with Fendazole, we note that 3 out of the 7 ponies had about one hundred Strongylus vulgaris ; 2 of them all passed parasites, but the third showed a negative result (table 3A). The result was also negative in the one pony which had Strongyloides westeri. Rate of activity in the four animals which had pinworms averaged 39 % (range %) (table 3B). Two out of the 8 ponies treated with Cambendazole has 200 Strongylus vulgaris : in one of them, effectiveness was rated at 100 %, while it was 0 % in the other (table 3A). Pinworms infection showed a more consistent distribution in this group since five ponies were infected, and activity of Cambendazole on the L4 form of these pinworms was only 13.9 %. In contrast, in one pony with Strongyloiiles vvesteri, all parasites were eliminated (table 3B). Out of the 8 ponies treated with Parbendazole, only one had 10 Strongylus edentatus and two had 100 Strongylus vulgaris which were not eliminated. In contrast, a fourth animal passed all of the 200 Strongylus vulgaris with which it had been infected. One animal had 300 Strongyloides westeri and 100 L4 pinworms which proved resistant to treatment (tables 3A, 3B). Variations in efficiency percentage It should be noted that, as shown in table 4, wide individual variations exist in efficiency percentage for certain anthelmintics. Time required to pass parasites Fig. 1 shows time required to pass parasites. Elimination of nematodes occurred 4 days after administration of the drug, and reached a maximum between 24 and 48 hours for Thiabendazole, Pyrantel embonate, Fenbendazole, Parbendazole and Albendazole. Maximum elimination occurred between 48 and 72 hours for Mebendazole, Oxfendazole and Dichlorvos. Pyrantel embonate caused the fastest elimination, with 24 % in the first 24 hours after dosage, 52 % in the period between 24 and 48 hours, 21 % in the period between 48 and 72 hours, and only 3 % in the period between 72 and 96 hours.

10 Stomach bots No bots are shown in the tables. Bot larvae were found in large numbers in stomach contents of all ponies except for animals treated with Dichlorvos, Mebendazole plus Trichlorfon, and Pyrantel embonate plus Trichlorfon. Discussion Lyons et al. (1974) have obtained with one 19.2 mg/kg dose of Pyrantel embonate 100 % efficacy against pinworms, both adult and L! larvae ; 91 % against Strongylus vulgaris ; 89 % against Strongylus edentatus, and % against Trichonema spp.. Troncy and Hubert (1976) and Bussieras (1977) have obtained similar results. We made identical observations, apart from L4 pinworms against which activity was low (50 % and Trichonema spp. against which activity was higher with 98 % for adults and 83 % for free L4 larvae. In combination with Trichlorfon (30 mg/kg), Pyrantel embonate presents efficacy of 98 % against stomach bots (Gasterophilus equfl (table 5) and 100 % against L, pinworms (Pecheur and Benakhla, ). With one 10 mg/kg dose of Oxfendazole, Duncan and Reid (1978) noted a good efficacy of 99.8 % against Trichonema spp. in adult and free L4 stages, and 97.6 % against Trichonema spp. L4 in mucosa. He reported 100 % activity against adult forms of Strongylus vulgaris and Strongylus edentatus, immature stages of Strongylus edentatus in peritoneum, adult pinworms, Trichostrongylus axei, and Parascaris equorum. Colglazier (1979) noted a similar response of large and small strongyles. Our results compare with those of Duncan and Reid (1978) with respect to adult Trichonema spp.. With respect to L4 larvae, they are lower, and there was no elimination of Strongylus vulgaris even though infection was on a low level. Activity against L4 pinworms was only 33 %. McCurdy et al. (1976) using one 10 mg/kg dose of Mebendazole, reported an activity level between 98.4 % and 100 % against Parascaris, Strongylus vulgaris, Strongylus edentatus, Trichonema spp., and pinworms. Using one 8.8 mg/kg dose, Colglazier et al.

11 (1978) reached lower activity levels : % against large strongyles, 97 % against small strongyles, 78 % against L4 of these strongyles, and 100 % against adult pinworms. They noted an activity of only 63 % against Parascaris. Our trials confirmed the efficacy of the drug against adult stages of Trichonema spp., a low level of activity against Tiichonema spp. L4, while activity against L4 pinworms seemed to us especially noteworthy (93 %1. Colglazier et a/. (1978), using 5 mg/kg of Albendazole, reported an activity level of 100 % against Strongylus vulgaris and Strongylus equinus, adult Trichonema spp., Parascaris equorum, and adult and L4 pinworms ; of 99 % against Strongylus edentatus and of 69 % against Tiichonema spp. L4. We noted a similar degree of activity as Colglazier et al. (1978) against adult Tiichonema spp. Activity was lower against Strongylus vulgaris (79 %) and pinworms (48 %), but better against Tiichonema spp. L4 (88.2 %). Drudge and Sharp (personal communication from Shell B.C.) reported 100 % activity of Dichlorvos at a dose rate of 43 mg/kg against Strongylus vulgaris, Strongylus equinus, Pascaris equorum, pinworms and bots ; % against Trichonema spp. ; % against bots and % against Strongylus edentatus. In other studies,

12 Drudge and Lyons (1972) noted that one 43 mg/kg dose was 100 % active against Parascaris equorum and adult pinworms, % against Strongylus vulgaris, % against Strongylus edentatus, and % against Trichonema spp., although with respect to the latter species activity was stronger against L4 than adults. Reineke (personal communication from Shell B.C.) noted results similar to those of Drudge and Lyons. On our part, we recorded results quite close to those above, apart from pinworm L4 larvae, for which activity was 91 %. Here again, activity against L4 was stronger than that against adult forms. Dichlorvos is often regarded as the only anthelmintic to be active against bot larvae. It should be noted, however, that Benzimidazole derivatives, in combination with Trichlorfon, produce similar results. We noted in 7 ponies that combination of Mebendazole and Trichlorfon was 98 % active against bots (table 5). Our results proved better than those obtained by Muylle et al (1979) (Pecheur and Benakhla, 1980). Lyons et a/ ) found Thiabendazole to be active against all Strongylus vulgaris and adult pinworms, % of Strongylus edentatus, and 40 % of Ascaris. By contrast, it appeared totally ineffective against Strongylo;- des even with a 88 mg/kg dose. We noted a good level of activity against adults and immatures Tiichonema spp., but a weak activity against L4 pinworms, and against large strongyles.

13 Regarding Fenbendazole, a large number of publications bear out its high level of activity. However, doses used vary widely. In trials using 5 mg/kg (Drudge et al., 1975 ; Colglazier et al., 1978), efficacy was 100 % against Strongylus vulgaris, % against Strongylus edentatus and Strongylus equinus, % against adult forms of Tiichonema spp., 78 % against immature forms of Trichonema spp., 100 % against adult pinworms, and % against immature pinworms. Drudge et a/. (1978) reported 100 % activity with one 10 mg/kg dose against Parascaris, Oxyuris, Strongylus vulgaris and Strongylus edentatus. Duncan et al. (1978) are not as optimistic. Using one 30 mg/kg dose of Fenbendazole, they reported 87 % activity against Trichonema spp. 4L in mucosa and 98 % against L5, 76 % against migrating Strongylus vulgaris L4 and 70 % against Strongylus edentatus. Generally speaking, our results are mostly below usually reported levels. Colgiazier et al. (19781, Cairns and Holmden (1977), and Lyons et al (1971) have shown that Cambendazole is 100 % active against Strongylus vulgaris, 99 % active against Strongylus edentatus, 99 % against adult forms of Trichonema spp., 77 % against Trichonema spp. L4, 100 % against adult forms of Parascaris equorum, and over 85 % against immature forms of Parascaris equorum, at least those in gut lumen. The results of our studies have not been so good, and they confirm, among other things, the excellent activity of the anthelmintic agent against Strongyloi = des (table 3B1. Its activity against L4 pinworms and large strongyles has not been confirmed (table 3B). Colglazier et al (1978) had noted 100 % activity against both adult and L4 forms of pinworms. We have found no data in literature on the subject of controlled critical tests with Parbendazole on horses. However, it seems that this antiparasitic agent has a much lower activity than other drugs. It averaged 83 % against adult forms of Trichonema spp. and only 33 % against immature forms. Conclusion All currently available anthelmintic agents used on equids show a good level of activity and some have interesting properties, so that choice of an anti-parasitic treatment will have to be guided, on the one hand, by genus and species of infecting parasites (based on a faecal examination), and on the other, on convenience of a particular treatment. Also of importance is the fact that results will be affected by the animal s physical condition, by presence of unaffected, immature forms, and by continuous re-infection. Dosages will therefore be required on a regular basis, and this is in turn poses the problem of parasite resistance to anthelmintic agents. Dewormers have been divided into two groups for nematodes according to their mode of action, spectrum of activity, and effectiveness against resistant populations : benzimidazoles and probenzimidazoles were placed in group I, while Pyrantel and Dichlorvos were placed in group II (Prichard et al., 1980). In order to prevent emergence of resistant strains and to control their resistance, a twofold approach is required : (1) decrease the frequency of anthelmintic dosages by resorting to prophylactic measures which lower the degree of pasture contamination, and (2) alternately use agents of group I and group II at yearly intervals. Accepted for publication, September 22nd, Acknowledgements We thank Prof. Hanset and Dr. Leroy for their kind collaboration in statistical evaluation of results. Summary A number of good anthelmintic drugs are currently available which eliminate gastrointestinal nematodes of equids with over 90 % success. This is shown by comparing results of critical tests conducted with 9 anthelmintic agents on ponies using the following dosages : 19 mg/kg for Pyrantel embonate, 10 mg/kg for Oxfendazole, 10 mg/kg for Mebendazole, 5 mg/kg for Albendazole, 40 mg/kg for Dichlorvos, 44 mg/kg for Thiabendazole, 7.5 mg/kg, for Fenbendazole,

14 20 mg/kg for Cambendazole and 7 mg/kg for Parbendazole. From 6 to 9 ponies were treated with each of these anthelmintic agents. Based on total activity of various parasites involved, there was no significant difference in activity of any of the nine agents. With respect to Trichonema spp., or small strongyles, which are most numerous and most common in equids, statistical analysis enabled all nine products to be classified into three groups as follows : group 1, with the most active being Oxfendazole and Pyrantel embonate ; group 2, including Thiabendazole, Mebendazole, Albendazole and Cambendazole ; group 3, with Parbendazole, Fenbendazole et Dichlorvos. Results with large strongyles sometimes vary quite significantly. Dichlorvos and Pyrantel embonate should be recommended against Strongylus spp. ; Mebendazole and Dichlorvos against pinworms ; Cambendazole against Strongyloi cles westeri ; Pyrantel embonate, Cambendazole and Dichlorvos against Parascaris equorum ; and Dichlorvos, Mebendazole with Trichlorfon and Pyrantel embonate with Trichlorfon against bots. No activity against Trichostrongylus axei, Anoplocephala spp. was noted with any of the nine agents tested. References BUSSIERAS J., Essai de traitement des helminthoses digestives des 6quid6s par le pamoate de Pyrantel. Rev. Méd. Vét., 128, CAIRNS G., HOLMDEN J., The anthelmintic efficacy of Cambendazole in horses. Vet. J., 25, COLGLAZIER M., ENZIE F., KATES K., Critical anthelmintic trials in ponies with four benzimidazoles : Mebendazole, Cambendazole, Fenbendazole and Albendazole. J. Parasitol, 63, COLGLAZIER M., Critical anthelmintic trials in ponies with Oxfendazole and Caviphos and concomitant studies on the spontaneous elimination of small strongylids. Am. J. Vet. Res., 40, DRUDGE J., LYONS E., TOLLIVER S., Critical tests of the Benzimidazole Anthelmintic, Fenbendazole in the horse. Vet. Med. Small Anim. Clin., 70, DRUDGE J., LYONS E., TOLLIVER S., Critical and controlled tests and clinical trials with suspension and granule formulations of the anthelmintic, Fenbendazole, in the horse. J. Equine Med. Surg., 2, DRUDGE J., LYONS E., Helminths of domestic equids. Critical tests of a resin-pellet formulation of Dichlorvos against internal parasites of the horse. Am. J. Vet. Res., 33, DUNCAN J., McBEATH D., BEST J., PRESTON N., The efficacy of Fenbendazole in the control of immature strongle infections in ponies. Nelminthol. Abstr., 47, abstract n DUNCAN J., REID J., An evaluation on the efficacy of Oxfenbendazole against the common nematode parasite of the horse. Vet. Rec., 103, LICHTENFELS J., Helminths of domestic equids. Proc. Helminthol. Soc. Wash., Special Issue, 42, 92. LYONS E., DRUDGE J., TOLLIVER S., Observations on development of Strongyloiiles westeri in foals nursing dams treated with Cambendazole or Thiabendazole. Am. J. Vet. Res., 38, LYONS E., DRUDGE J., TOLLIVER S., Critical tests of three salts of Pyrantel against internal parasites of the horse. Am. J. Vet. Res., 35, LYONS E., DRUDGE J., TOLLIVER S., Critical tests of anthelmintic activity of a paste formulation of Thiabendazole in horse. Am. J. Vet. Res., 37, Mc CURDY H., SHARP M., SWEENY W., Evaluation of Mebendazole in paste formulation in the horse. Vet. Med. Small Anim. Clin., 71, MUYLLE E., OYAERT Q., ROGIERS M., Endoscopic examination of the horse stomach in the assessment of the efficacy of a Mebendazole/Trichlorfon paste against Gasterophilus intestinalis larvae. Vlaams Diergeneeskd. Tijdschr., 48, PECHEUR M., DETRY-POUPLARD M., GERIN G., TINAR R., Les helminthes parasites du syst6me digestif de poneys abattus en Belgique. Ann. Méd. Vét., 123, PECHEUR M., BENAKHLA A., Activite du Trichlorfon en association avec le Mebendazole vis-6-vis des larves de Gasterophilus equi. Ann. M!d. V!t., 124, PECHEUR M., BENAKHLA A., L efficacité de I Embonate de Pyrantel + Trichlorfon sur les parasites du poney. Ann. Méd. Vet. en publication. PRICHARD R., HALL D., KELLY J., MARTIN I., DONALD A., The problem of anthelmintic resistance in nematodes. Aust. Vet. J., 56,

15 RAYNAUD Jy, Examen critique des techniques de mise au point d un antheimintique actif sur les strongyloses, digestives des petits ruminants. 8ee: MOd. V6,t., 148, TRCFNGY L7. ; Hl)BEEiT J., Essai dlinique du pamoate de pyrantel chez le ehevai. Ree. M6d V6t!., 152, 8 f 1-$T!S.