Drug resistance and genetic characteristics of one Eimeria tenella isolate from Xiantao, Hubei Province, China.

Chicken coccidiosis causes retarded growth and low production performance in poultry, resulting in huge economic losses to the poultry industry. In order to prevent and control chicken coccidiosis, great efforts have been made to develop new drugs and vaccines, which require pure isolates of Eimeria spp. In this study, we obtained the Eimeira tenella Xiantao isolate by single oocyst isolation technology and compared its genome with the reference genome GCF_000499545.2_ETH001 of the Houghton strain. The results of the comparative genomic analysis indicated that the genome of this isolate contained 46,888 single nucleotide polymorphisms (SNPs). There were 15,107 small insertion and deletion variations (indels), 1693 structural variations (SV), and 3578 copy number variations (CNV). In addition, 64 broilers were used to determine the resistance profile of Xiantao strain. Drug susceptibility testing revealed that this isolate was completely resistant to monensin, diclazuril, halofuginone, sulfachlorpyrazine sodium, and toltrazuril, but sensitive to decoquinate. These data improve our understanding of drug resistance in avian coccidia.

Anticoccidial activity of a botanical natural product based on eucalyptus, apigenin and eugenol against Eimeria tenella in broiler chickens.

BACKGROUND: Chicken coccidiosis is an intracellular parasitic disease that presents major challenges to the development of the commercial poultry industry. Perennial drug selective pressure has led to the multi-drug resistance of chicken coccidia, which makes the prevention and control of chicken coccidiosis extremely difficult. In recent years, natural plant products have attracted the attention of researchers due to their inherent advantages, such as the absence of veterinary drug residues. The development of these natural products provides a new direction for the prevention and treatment of chicken coccidiosis. METHODS: The anticoccidial effect of a natural plant product combination formulation (eucalyptus oil + apigenin + eugenol essential oil) was tested against Eimeria tenella in broilers. To search for the optimal concentration of the combination formulation, we screened 120 broilers in a chicken cage trial in which 100 broilers were infected with 5 × 104 sporulated Eimeria tenella oocysts; broilers receiving a decoquinate solution was set up as a chemical control. The optimal anticoccidial concentration was determined by calculating the anticoccidial index (ACI), and the suitable concentration was used as the recommended dose for a series of safety dose assessment tests, such as feed conversion ratio (FCR), hematological indices and serum biochemical indices, as well as liver and kidney sections, at onefold (low dose), threefold (medium dose) and sixfold (high dose) the recommended dose (RD). RESULTS: The results showed that this combination formulation of three plant natural products had a better anticoccidial effect than formulations containing two plant natural products or a single one, with an ACI of 169.3. The dose gradient anticoccidial test revealed that the high-dose formulation group had a better anticoccidial effect (ACI = 169.2) than the medium- and low-dose groups. The safety evaluation test showed that concentrations of the formulation at one-, three- and sixfold the RD were non-toxic to Arbor Acres broilers, indicating the high safety of the combination formulation. CONCLUSIONS: The combination formulation showed not only a moderate anticoccidial effect but also had a high safety profile for broilers. The results of this study indicate a new alternative for the prevention and control of coccidiosis in broilers.