Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/11/2006
Publication Date: 3/1/2007
Citation: Allen, P.C. 2007. Anticoccidial effects of xanthohumol. Avian Diseases. 51:21-26.
Interpretive Summary: Avian coccidiosis is the most economically important parasitic disease of the poultry industry world-wide. However, the protozoan parasites of the genus Eimeria that are responsible for this disease have developed wide-spread resistance to the anticoccidial medications that traditionally have been used for prophylactic control. Consequently, novel methods for controlling avian coccidiosis need to be developed. As part of this effort, a search for potential new agents, particularly those that might be considered GRAS (generally regarded as safe), has been ongoing. Xanthohumol (XN) is a major component of the alcohol-soluble compounds found in hops flowers. Recent reports in the literature have highlighted its antimicrobial, and antimalarial activities which have prompted tests in this laboratory to determine whether it also has anticoccidial properties. The experiments in this report show that treatment of the sporozoite stages of E. tenella and E. acervulina with 20 ppm XN is detrimental to the morphology of the sporozoites, and inhibits their invasion into host cells, indicating that XN has anticoccidial properties. However, a pilot test of XN as a feed additive at 20 ppm proved ineffective when judged by effects seen on weight gain, feed conversion and lesion scores of treated, challenged chickens. Nevertheless, 20 ppm XN did reduce oocyst out put from chickens infected with E. acervulina and E. maxima, indicating that it can inhibit reproduction of these parasites. Further experiments are needed to determine proper dosing strategies to enable XN use as a new anticoccidial.
Technical Abstract: Xanthohumol (XN), a prenylated chalcone from the hops flower, was examined for its ability to reduce invasion of MDBK cells by E. tenella sporozoites, as well as to reduce invasion by E. tenella and E. acervulina sporozoites in the chick host. additionally, XN was tested as an anticoccidial feed additive at 20 ppm against challenge infections with E. acervulina, E. maxima and E. tenella. Cell invasion by E. tenella sporozoites was inhibited 66% by treatment of sporozoites with 22 ppm XN. This inhibition was associated with apparent physical disruption of the apical ends of the sporozoites. Rectal challenges with E. tenella sporozoites treated with 5, 10 and 20 ppm XN resulted in significantly reduced gross lesion scores and normal chick host weight gains compared to challenge with untreated sporozoites. Oral challenges with similarly treated E. acervulina sporozoites, accomplished with prior antacid treatment, resulted in significantly reduced gross lesions and reduced oocyst shedding compared to challenge with untreated SZ, and was associated with physical disruption of sporozoite morphology. In a pilot test, provision of feed supplemented with 20 ppm XN for three days prior to challenge to six days post challenge did not control challenge infections with E. acervulina, E. maxima or E. tenella as judged by measurements of weight gain , feed conversion and gross lesions. However, oocyst shedding by E. acervulina and E. maxima–infected chickens was reduced indicating that it can inhibit parasite reproduction. Further experiments are planned to determine proper dosing strategies to enable XN use as a new anticoccidial