Effectiveness of Therapeutic Anticoccidial Drugs Against Recently Isolated Coccidia 1

Effectiveness of Therapeutic Anticoccidial Drugs Against Recently Isolated Coccidia 1 GREG F. MATHIS and LARRY R. McDOUGALD 2 Department of Poultry Science, University of Georgia, Athens, Georgia 30602 BIRCH McMURRAY Central Soya, Athens, Georgia 30601 (Received for publication July 1, 1983) ABSTRACT Litter samples were collected weekly from 17 broiler houses and coccidial oocysts were counted. Oocysts per gram were low on the Weeks 1 and 2 of the growout, increased to a peak on the Week 4, then declined to near zero on Weeks 6 and 7. Coccidia from each house were propagated and tested for sensitivity to therapeutic formulations of amprolium, sulfaquinoxaline, and sulfaquinoxaline plus pyrimethamine. The degree of control was based on the weight gains and lesion scores of the medicated groups in comparison with those of the unmedicated, infected, and uninfected groups. The predominant species found in the 17 isolates were Eimeria tenella and E. acervulina. Amprolium was effective against E, tenella in all isolates but only partly effective against E. acervulina. Sulfaquinoxaline and the potentiated mixture were effective against the E. acervulina but only partly effective against the E. tenella. The potentiated mixture was better against E. tenella than sulfaquinoxaline alone. (Key words: coccidiosis, therapeutic, field isolates, Eimeria tenella, Eimeria acervulina, broilers, amprolium, sulfonamides, potentiated sulfonamides) INTRODUCTION Despite the continuous feeding of prophylactic anticoccidial drugs in broiler chickens, control of coccidiosis is incomplete. There are many variables that can cause outbreaks of coccidiosis, such as drug resistance, limited species spectrum of activity, interrupted medications, climatic conditions, and management. Drugs may be given in the drinking water to control these clinical outbreaks. Three classes of drugs are currently available in liquid form for therapeutic use in poultry. These are amprolium, sulfonamides, and sulfondamides potentiated with 2,4-diaminopyrimidines. Because all of the drugs in these classes have been used for many years, drug resistance might have become a serious limit to their effectiveness. This study was done to determine the prevalence of coccidia on some typical poultry farms, to identify the species of Eimeria present, and to measure the therapeutic effec- 1 Supported by State and Hatch funds allocated to the Georgia Agricultural Experiment Stations of the University of Georgia. 2 To whom correspondence should be addressed. 1984 Poultry Science 63:1149-1153 tiveness of representative drugs of the three types. MATERIALS AND METHODS Litter samples were collected weekly from 17 broiler houses hear Athens, GA during the autumn of 1981 by the method of Long et al. (1975). Each sample was identified as to farm and house location by an alphanumeric code. After the oocysts were counted, a portion of each sample was fed to susceptible chicks for propagation of oocysts and identification of species of Eimeria present. One such isolate from each house was chosen for further study. Drug Sensitivity Tests. Groups of 5 to 6 isolates of coccidia were tested for sensitivity to the three types of drugs in standard tests lasting 8 days. Broiler cockerels, 14 days old, were randomized into cages of clean Petersime finishing batteries. Each treatment was replicated in two cages of 10 birds each. They were given experimentally medicated drinking water for 1 day, then inoculated with 500,000 oocysts/chick of the test coccidia. Daily observations were made to detect signs of coccidiosis and to record mortality. The birds were weighed at the time of inoculation and 7 days 1149

1150 MATHIS ET AL. later feed consumption was determined; all birds were killed on Day 7 for lesion score (Johnson and Reid, 1970). The drugs studied in this way were amprolium, 125 ppm (Amprol Liquid, MSD Agvet, Rahway, NJ), sulfaquinoxaline, 125 ppm (SQ. liquid formulation, MSD Agvet), and sulfaquinoxaline plus pyrimethamine, 50/15 ppm (Whitsyn S, Whitmoyer, Myerstown, PA). Data were analyzed for significance (P<.05) by analysis of variance and Duncan's (1955) multiple range test. RESULTS Oocysts were found in all 17 broiler houses in all samples collected. The oocyst counts were very low at the start of the growout, averaging 134 to 250/g of litter on weeks 0, 1, and 2. The counts on weeks 3, 4, or 5 averaged 6164, 1260, or 1462/g, respectively. By the 6th week, the counts had fallen to 290/g and on the 7th week to 97/g. Examination of oocyst size and the location and appearance of lesions revealed Isolate 1 Ml CI A3 Bl B2 B3 M2 Al A4 A5 S3 S4 S2 A2 SI C2 S5 that the most common important species of coccidia in the isolates were E. tenella and E. acervulina. Almost all of the isolates were highly pathogenic, producing significant reduction in weight gain in the unmedicated, infected controls (Table 1). None of the drugs gave good protection of weight gains, although most treated groups gained more weight than the unmedicated, infected controls. When the lesion scores were considered separately for each part of the intestinal tract, however, the limited spectrum of activity of each drug was apparent (Table 2). In every instance, amprolium was highly effective in controlling cecal lesions and reduced average cecal scores for the 17 isolates from 4 to.2 (93% reduction). Amprolium was not as effective against upper intestinal coccidia where the lesion scores were reduced from 2.93 to 0 (28% reduction). Both sulfaquinoxaline and sulfaquinoxaline plus pyrimethamine were highly effective against upper intestinal coccidia, reducing the lesion TABLE 1. Weight gain (g/bird) and feed conversion of birds infected with field isolates of coccidia and treated with various drugs 2 228 a 99 e 92 c 82 d 100 c 30e Unmedi icated 178 a 121 b 155 ab 43 c 130 b 43 c 146 a 86 c 106 ab 99b 73b 79c 63b 3 1.4 3.5 4.3 3.1 3.2 3.4 4.1 3.4 Amprolium 190 b 17 9 b 178 b 171 b 160 b 164 b 164 a 159 ab 93 b 181 a 67 b 113 b 93bc 88 b 69 b 106 b 88 b 1.8 1.9 2.9 3.5 3.8 Sulfaquinoxal ine 124 d 129 c 142 b 143 c 155 ab 180 a 93b 109 b 58 b 70 c 120 bc 78 b 76 b 63 c 45 bc 3.1 5.1 162 c 160 b 127 c 158 b 100 c 88 d 121 a 105 b 93b 108 b 19c 62 c 55 c 66 b 23 c 52 c 10 c Sulfaquinoxaline plus Pyrirr leth amine 4.2 3 b c d p ' ' ' ' Values for each isolate are significantly different (P<.05) from other values in the same row or with uninfected controls if not followed by a similar superscript letter. 1 Code used to identify the source of the isolate based on farm and house. 2 Weight gain (g/bird). 3 Feed conversion (g feed/g gain).

TREATMENT OF COCCIDIOSIS 1151 TABLE 2. Duodenal (U) or cecal (C) lesion scot treated with an of birds infected with isolates of coccidia and occidial drugs Unmedicated Amprolium Sulfaquinoxaline Sulfaquinoxaline plus Pyrimethamine Isolate U C U C J C U C Ml 3.2 a a a 0 d CI 3.5 a 3.8 a a 0 C A3 3.6 a b 3.2 a 0 C Bl 3.8 a 3.8 a b B2 3.2 a a b 0 C B3 3.6 a a b.5 C M2 a 3.1 a b.ic Al 3.5 a 1.0 a b.lb A4 2.9 a 3.3 a b A5 a b 1.9b 53 2.9 a a 1.5b.5 b c 54 a 2.l b a.4 C S2 a l.l ab 1.0 b 0 C A2 2.7 a a 1 SI a 2.7 a a 0 b C2 a 2.9 a 1.5b 55 a a 1.5b 0 C X 2.93 a 4 a 0 b ' ' ' Values within a row are significantly differen controls if not followed by a similar superscript letter. scores to.30 (90%) or to.22 (92%), respectively. In most instances, neither of the sulfonamide products had significant activity against cecal coccidia, although the potentiated sulfa gave an overall reduction in cecal lesion scores to 1.90 (33% reduction). There was no reduction in cecal lesion scores with the sulfonamide alone. The partial activity of the potentiated sulfa against E. tenella was recorded with isolates M2, A5, S3, A2, C2, and S5. Nothing unique was discovered about any isolates to account for different responses to drugs except for the obvious species differences. DISCUSSION Populations of oocysts found in the present study were probably typical of the time of year and control programs in use. Much higher oocyst counts were reported by Long et al. (1975) in houses where the control program was not as effective, but the pattern of production and decline was much the same. Our finding that oocysts could be isolated from all of the houses in the study is consistent with previous reports on the prevalence of coccidia in commercial poultry (Jeffers, 1974a,b). l b >.6 C A c.8 C C 2bc.6.30C 3.5 b 3.6 a 3.8 a 3.8 a 3.3 b a 2.7 a.5 b 3.5 a 3.6 a a 3.4 a 1.9 b 2.9 a a 2.9 C a 4 a.6 b 0 b.6 b.2<= Od 0 C 0C 1.0 b.2c Od,22 c C b b b 3.6 ab 2.7 b 1.4 b b.6 C l.l b b.7 b 1.4 b a b l.lb 1.91 b (P<.05) from other values in the row or with uninfected The incomplete spectrum of activity of anticoccidial drugs has long been recognized as a limitation to the effectiveness of their use. Even though amprolium had some activity against E. acervulina and E. maxima in the laboratory (Cuckler et al., I960; Rogers, 1962), control of E. tenella was better in commercial practice, and the drug was later combined with ethopabate to provide better control of E. acervulina and E. maxima (Rogers et al., 1964). In other instances, amprolium has been combined with sulfaquinoxaline and pyrimethamine to provide a broader spectrum (Long, 1963; McManus et al., 1967; Roncalli, 1974). Similarly, sulfaquinoxaline has some activity against E. tenella when used at high levels (Delaplane et al., 1947) but is most effective against the other intestinal species of coccidia (Long, 1963; Davies and Joyner, 1963). Field problems were reported with E. tenella when sulfaquinoxaline was used alone (Joyner, 1964). The synergism of sulfaquinoxaline by concurrent feeding of pyrimethamine (Lux, 1954; Kendall and Joyner, 1956; Ball and Warren, 1956) allowed development of products with lower recommended levels of the drugs, thereby reducing the toxicity. The addition of pyrimethamine to sulfaquinoxaline (and other similar combina-

1152 MATHIS ET AL. tions) synergized the action of sulfas against E. acervulina and E. maxima and provided a weak but measurable activity against E. tenella. Recent reports on the widespread occurrence of coccidia resistant to amprolium and sulfaquinoxaline (Jeffers, 1974a,b; Oikawa et al, 1975; Mathis and McDougald, 1982; Chapman, 1980, 1982) led us to expect resistance to be common in the present study. Isolates of E. maxima from farms in the United Kingdom previously treated for several years with mixtures of amprolium, ethopabate, and sulfaquinoxaline were resistant to this combination of drugs (Chapman, 1980). Partial resistance was found with isolates of E. acervulina (type) from the same farms (Chapman, 1982). Although incomplete control was observed in most instances in the present study, analysis of the lesion score evidence revealed that there was good control of the species which the drug is known to control. In this way, surprisingly good control was found with all three types of drugs. The failure of complete control could be attributed to limited species spectrum in almost all instances. The apparent lack of correlation of these results with previous drug resistance studies might be attributed to three points: 1) The drug intake via the drinking water is approximately double that expected via the feed. 2) The drugs might be better absorbed from water than from the feed (personal communication from MSD Agvet, Rahway, NJ) or 3) Previous studies did not always take into account the differing results against intestinal and cecal coccidia when testing mixed isolates of coccidia. These results clearly demonstrate the importance of an accurate species diagnosis before initiating treatment of clinical outbreaks and also illustrate the difficulty in dealing with field cases that involve more than one species. In some instances more than one treatment will be required before all species of coccidia will be brought under control. Control of E. tenella is most important, followed by E. maxima and E. acervulina. Based on the results of this study and previously published work, outbreaks of E. tenella could best be treated by amprolium, and outbreaks of E. acervulina could best be treated by sulfonamides or potentiated sulfonamide products. These results should be interpreted in a generic sense, rather than as recommendations for specific products, because other drugs in the same class should be equally suitable. REFERENCES Ball, S. J., and E. W. Warren, 1965. Synergism in the chemotherapy of Eimeria infection of chicks. Vet. Rec. 77:1028-1030. Chapman, H. D., 1980. Studies on the sensitivity of field isolates of Eimeria maxima to combinations of anticoccidial drugs. Avian Pathol. 9:67 76. Chapman, H. D., 1982. 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TREATMENT OF COCCIDIOSIS 1153 York Acad. Sci. 98:412-429. Rogers, E. F., R. L. Clark, H. J. Becker, A. A. Pessolano, W. J. Leanza, E. C. McManus, F. J.Andruili, and A. C. Cuckler, 1964. Antiparasitic drugs. V. Anticoccidial activity of 4-amino-2-ethoxybenzoic acid and related compounds. Proc. Soc. Exp. Biol. Med. 117:488-492. Roncalli, R. A., 1974. The genesis of Pancoxin Plus, a better coccidiostat. Merck & Co., Misc. Publ., March 21.