Infection with the protozoa Histomonas meleagridis in poultry has re-emerged since the ban of effective drugs. Consequently efforts are set to find alternatives to chemotherapeutics to combat histomonosis. At present histomonads need accompanying bacteria when cultured in vitro, probably serving nutrient supply due to their appearance in parasitic food vacuoles. However, the relationship of the parasite and the bacteria is not fully clear.
Six previously established clonal cultures of H. meleagridis were used to evaluate the effect of five Artemisia annua derived materials (i.e. dry leaves, artemisinin; and hexane, dichloromethane or methanol extracts). Dry leaves, artemisinin, hexane and dichloromethane extract displayed significant inhibitory activity against all six mono-eukaryotic cultures.
The aim was to assess whether the observed effects on H. meleagridis multiplication could be accounted as direct or indirect. The disc diffusion method was applied to evaluate the antibacterial activity on the accompanying xenic bacteria from all six clonal H. meleagridis cultures.
E. coli (8/19) was isolated at least once from all six H. meleagridis cultures, including four APEC isolates (O1, O2, or O78). Streptococcus spp. (5/19) or Proteus spp. (5/19) were isolated from four protozoal cultures. Staphylococcus sp. was isolated once.
No antibacterial effect was noticed with compound concentrations identical to the antihistomonal screening.
Combining the results of the antiprotozoal screening with the antibacterial tests, it is reasonable to assume that the observed inhibitory effect of the tested materials is attributed to a direct effect on the protozoa. However, the potential of these materials on histomonosis has been tested in vivo in chickens and in turkeys without success.