In vitro and in vivo protective action of a thymol-based blend of botanicals against coccidiosis

Chicken coccidiosis is a parasitic disease caused by Eimeria spp. Research has focused on finding new alternatives to fight these pathogens and botanicals have gained much interest in this field. The aim of this study was to test the anticoccidial activity of a thymolbased blend of botanicals both in an in vitro model of coccidiosis and in vivo in broiler chickens. For the in vitro assay, Madin-Darby bovine kidney cells were challenged with 5x104E. tenella sporozoites without (control) or with a thymol-based treatment (14 ppm). After 24 h at 37°C the efficiency of invasion was determined by counting the sporozoites left in the medium that were not able to invade the cells. Moreover, intracellular E. tenella DNA was detected by qPCR. Data were analyzed with T-test and differences considered significant at P<0.05. Sporozoites counts data showed that the treatment reduced the efficiency of invasion compared to control by 33% (P<0.0001). Accordingly, the presence of intracellular E. tenella DNA was reduced by 51.2% in treated cells compared to control cells (P<0.05). For the in vivo trial, 1,800 day-old broiler chicks (50 chicks/pen) were assigned to 3 treatment groups (12 pens/group) as follows: (1) control, fed a basal diet; (2) salinomycin, fed a basal diet + salinomycin 60 ppm; (3) treatment, fed a basal diet supplemented with a microencapsulated thymol-based blend at 100 ppm (3). On d22 all chicks were infected with a multispecies Eimeria inoculum. Eimeria lesion score was measured on d28 and oocysts per gram (OPG) of feces determined on d29 and d36. Data were analyzed with ANOVA and differences considered significant at P<0.05. Compared to control, lesion score was reduced by salinomycin and, to a similar extent, by the treatment (P=0.01). OPG were not affected on d29 but both salinomycin and the thymol-based blend reduced oocysts shedding compared to control on d36 (P<0.05). In conclusion, these studies showed both in vitro and in vivo anticoccidial properties for the thymol-based blend tested and it can be proposed as alternative to traditional anticoccidial products.