BackgroundCoccidiosis due to Eimeria spp. infections in lambs causes increased mortality and substantial production losses, and anticoccidials are important for control of the infection. Anticoccidial resistance has been reported in poultry and swine, and we recently described reduced toltrazuril efficacy in ovine Eimeria spp. in some Norwegian sheep farms using a newly developed faecal oocyst count reduction test (FOCRT). The aim of the present study was to use a controlled efficacy trial to assess the efficacy of toltrazuril against a field isolate suspected of being resistant.MethodsTwenty lambs, 17–22 days old and raised protected against exposure to coccidia, were infected with a field isolate of 100,000 Eimeria spp. oocysts. This isolate was obtained from a farm with a previously calculated drug efficacy of 56% (95% confidence interval: -433.9 to 96.6%). At day 7 post-infection, 10 of the lambs were orally treated with 20 mg/kg toltrazuril (Baycox Sheep vet., Bayer Animal Health), while the other 10 lambs (controls) were given physiological saline. Clinical examinations were conducted, and weight gains recorded. Daily faecal samples were scored for diarrhoea on a scale from 1 to 5, and oocyst excretion was determined using a modified McMaster technique. Oocysts were morphologically identified to species level. At 17–24 days post-infection, the lambs were euthanized and necropsied.ResultsThe tested Eimeria isolate was resistant against toltrazuril, and resistance was seen in both pathogenic and non-pathogenic species. In addition, no significant differences in faecal score, growth, gross pathology or histological changes were identified between the two groups. The pathogenic E. ovinoidalis was the dominant species, and no significant difference in the individual prevalence of E. ovinoidalis post-treatment was found between treated (66.9%) and control lambs (61.9%). Other species identified included E. crandallis/weybridgensis, E. parva, E. marsica, E. faurei, E. pallida, E. ahsata and E. bakuensis.ConclusionsThis study confirms toltrazuril resistance in ovine Eimeria spp.; in addition, the data support the use of FOCRT as an appropriate tool for field evaluation of anticoccidial efficacy. Due to limited anticoccidial treatment alternatives, these findings may have important implications for the sheep industry, particularly in northern Europe.Electronic supplementary materialThe online version of this article (10.1186/s13071-018-2976-4) contains supplementary material, which is available to authorized users.

No abstract

BackgroundIron is an essential nutrient, and iron supplementation has been shown to reduce the incidence of abomasal bloat in lambs. Additionally, iron deficiency is linked to pica, which may increase uptake of Eimeria oocysts. Coccidiosis in sheep, caused by Eimeria spp., is an important infection, leading to reduced welfare and economic losses. The aims of our study were to investigate: (1) the use of iron supplementation in Norwegian sheep flocks using a questionnaire survey, and (2) whether iron supplementation reduced excretion of Eimeria oocysts and increased the growth rates of young lambs.ResultsA questionnaire regarding the use of iron supplementation, sent to all members of the Norwegian Sheep Recording System (n = 4993), showed that 152/1823 farmers iron-supplemented lambs, either orally (56.7%) or by injection (43.3%). The main purpose of supplementation was to prevent abomasal bloat (38.4%), coccidiosis (9.3%), or both (27.8%). In the field study, 102 twin lambs from five flocks were included: one twin (treated) received 600 mg of gleptoferron subcutaneously within 3 days of birth, whereas the control was given saline. McMaster analysis of individual faecal samples obtained at weekly intervals (n = 4 per lamb, starting at turnout) showed no significant difference in oocyst excretion between treatment groups at any sampling, except for one flock 14 days after turnout. Mean growth rates, measured at iron injection, 21 days after turnout, and in the autumn, differed significantly between treated and untreated lambs from iron injection to 21 days after turnout, however, no difference in growth rates was observed in the overall period from iron injection to autumn. Blood analysis suggested that the controls were at risk of developing iron deficiency anaemia during the housed period, but signs of anaemia were not observed.ConclusionIron supplementation of lambs was used by 8.3% of the farmers responding to the questionnaire, mainly with the intention to prevent abomasal bloat, coccidiosis, or both. The field trial results indicate that iron supplementation of young lambs do not reduce oocyst excretion and only induced a transitory increase in weight gain. However further studies, including more flocks and possibly repeated iron injections, would provide more definitive information.Electronic supplementary materialThe online version of this article (10.1186/s13028-018-0404-6) contains supplementary material, which is available to authorized users.