Efficacy of toltrazuril and amprolium against turkey coccidiosis caused by a mixed E. adenoeides and E. meleagrimitis infection.


Robrecht Froyman   Bayer HealthCare, Animal Health, 51368 Leverkusen, Germany

Ten-day-old turkeys, raised in floor-pens (2 replicate pens of 5 turkeys per experimental group, 14/24 h lighting), were gavage challenged with a mixed inoculum containing drug sensitive Weybridge strains of E. adenoeides (Ead) and E. meleagrimitis (Eme) at 3,000 and 10,000 oocysts/bird, respectively. Experimental groups consisted of positive controls (challenged, untreated), negative controls (unchallenged, untreated), and 4 groups that were challenged and subsequently treated in the drinking water with amprolium (Nemaprol 10.6 %) at 240 ppm for 5 days (114 mg/kg daily), or with toltrazuril (Baycox 2.5%) using either one of 3 dosage regimens, viz. 7 mg/kg daily for 2 days (label claim), 15 mg/kg for one day, and 20 mg/kg for one day. Six out of 10 challenge control turkeys died from coccidiosis whereas all treated turkeys survived. The oocyst count of faecal samples pooled at day 4-8 post infection (PI) amounted to 544,000/g for the challenge controls and was reduced in the amprolium treated group to 51,000/g. No oocysts were shed in any of the toltrazuril treated groups. Mean lesion scores (on a scale of 0-4) for Ead/Eme were 3.5/3.3 and 1.7/2.2 in the positive control and amprolium group, respectively. A mean score as low as 0.1 was observed in the toltrazuril 7mg-2days group, only for Ead, and in the toltrazuril 15mg-1day group, only for Eme. Also in the toltrazuril 20mg-1day group a very low score of 0.6 was observed, only for Eme. Negative controls gained 303 +46 g of weight from the day of infection until 7 days PI whereas weight gain was severely depressed in the surviving challenge control turkeys (161 +75 g) and the amprolium treated turkeys (162 +14 g). Growth was unaffected by coccidiosis challenge in all toltrazuril treated groups with weight gains of 320 +35 g (7mg-2days), 318 +12 g (15mg-1day) and 300 +49 g (20 mg-2days). In conclusion, toltrazuril cured turkey coccidiosis better than amprolium and limiting the duration of toltrazuril treatment to a single day, whilst maintaining the total therapeutic dose, did not diminish the efficacy.