| Chicken coccidia mainly parasites in chicken’s intestinal cells, causing coccidiosis with main feature of intestinal lesions, is seriously harmful to the development of the poultry industry. Currently, due to the vaccines used to prevente coccidiosis are mostly live vaccines, under certain conditions their virulences may return and they has certain risk to some of the susceptible animals. Therefore, drug prevention and treatment of coccidiosis is still the most important way, such as salinomycin, maduramicin, monensin, Hainan neomycin. But with the emergence of drug-resistant strains of coccidium, it makes a lot of difficulties for clinical prevention and treatment of coccidiosis. Thus, finding new drugs is the key to control coccidiosis.A recent study found that protease inhibitors can inhibit the cell invasion of protozoa, Serine thiolproteinase inhibitor(3, 4-dichloroisocoumarin, DCI) is a compound capable of inhibiting serine kinase’s activity. Studies have shown the addition of DCI had a certain inhibitory effect on the progress of sporozoites infect cells in vitro. Gefitinib, Erlotinib and Crizotinib are all tyrosine kinase inhibitor drugs,which are capable of inhibiting the invasion of Toxoplasma gondii of host cells. However, it has not been reported whether it can be used in the prevention and treatment of Coccidiosis, further researches about if DCI, gefitinib and other tyrosine kinase inhibitors are able to prevent Coccidiosis have not been reported.In this experiment, for the identification of new drug candidate to prevent and treat coccidiosis, we intend to use DCI; Gefitinib,Erlotinib and Crizotinib to prevent and treat Coccidiosis and select the medicine which can effectivelly prevent Coccidiosis. Then, take safty evaluation for the selected medicine by clinical observation and analysis of Blood biochemistry.1. The screening of protease inhibitor drugs to prevent Coccidiosis380 healthy chickens with similar weight were divided into 19 groups, 20 chickens / group(Healthy controls, drug controls, positive controls, three Fold dilution groups of DCI, four fold dilution groups of Gefitinib, four fold dilution groups of Crizotinib, five fold dilution groups of Erlotinib). Except healthy control and positive control groups, infected each group with avian coccidiosis after drug delivery in 7 days(1.0×104 Eimeira tenella sporulated oocysts for one chick). Then the status of chickens’ spirit and appetite during infection were observed. A week later, weighed and killed each chicken; metered their survival rate, weight gain rate, bloody situation, the relative weight gain rate, cecal lesions; and collected each group’s chicken feces, calculated the number of oocysts. The result shows that: DCI group ACI 117.34-161.04;Gefitinib group ACI 87.83-110.55; Crizotinib group ACI 98.94-132.79; Erlotinib group ACI 68.54-97.49. In conclusion,the DCI middle dose group(0.005 mg/one chick in drinking water for a consecutive 7 days) has the best prevention of coccidiosis, the ACI is 161.04.2. The screening of protease inhibitor drugs to treat Coccidiosis380 healthy chickens with similar weight were divided into 19 groups, 20 chickens / group(Healthy controls, drug controls, positive controls, three fold dilution groups of DCI, four fold dilution groups of Gefitinib, four fold dilution groups of Crizotinib, five fold dilution groups of Erlotinib). Infected the each group with avian coccidiosis, 1.0×104 E. tenella sporulated oocysts for one chick, at the same time, dilivered the drugs for five days, except healthy control and positive control groups. Then the status of chickens’ spirit and appetite during infection were observed. A week later, weighed and killed each chick; metered their survival rate, weight gain rate, bloody situation, the relative weight gain rate, cecal lesions; and collected each group’s chicken feces, calculated the number of oocysts. The result shows that: DCI group ACI 133.13-178.73; Gefitinib group ACI 110.66-135.96; Crizotinib group ACI 85.51-125.17; Erlotinib group ACI 89.76-109.47.In conclusion. The DCI middle dose group(0.005 mg/one chick in drinking water for a consecutive 5 days) has the best prevention of coccidiosis, the ACI is 178.73. 3. Security research of DCI to the target animal250 healthy chickens with the similar weight were divided them into 5 groups by different delivery dose: 1× dose group(0.005 mg / only), 3×dose group(0.015 mg / only), 5× dose group(0.025 mg / only) and 10×dose group(0.05 mg / only), 50 chickens / group. Each group is delivered drugs by water for 21 days, except the control group. The safety of drugs was evaluated through clinical observation, hematological, blood biochemical, pathohistological and autopsy indexes of the experimental animals. The results indicated that there are no significant changes in hematology parameters between the experiment groups and control group(p>0.05). There were not any changes in all the indicators in 1×dose group.However, ALP, AST and T-BIL of 3× dose group, 5×dose group and 10×dose had significant difference with those of the control(p<0.05). We had observed the yellow liver and bleeding and bleeding spots in intestinal in some chickens. The tissue slices of liver and intestinal were observed by light-microscope. There are mild edema and steatosis in the 3× dose group, no pathological changes in the intestinal tract. There are fatty degeneration of liver and rupture of intestinal villi in 5× dose group. There are inflammatory cells form a filamentous network of the 10×dose group and with fatty degeneration of liver and rupture of intestinal villi. The safety experments suggest that more than 3×dose of DCI is toxic for the chickens’ healthy, which mainly caused yellow liver and bleeding spots in intestinal. The tests indicated that the DCI below the 1× dose group is safe to the target animal chicken. |
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