| Coccidiosis is a common parasitic disease in rabbits with a mortality rate up to70%in young animals. This study was base on epidemiological investigation and species identification of rabbit coccidiosis in Nantong area. The specific pathogen-free (SPF) New Zealand rabbits as the control, we observed the pathology structure of liver and duodenum and liver function parameter changes of ordinary grade rabbits with coccidiosis infection. We evaluated the treatment effects of sulfaquinoxaline (SUL), robenidine (ROB) and toltrazuril (TOL) against rabbit coccidiosis and their interaction with antibiotics of Florfenicol. Clarification the influcence on the drug metabolizing enzyme CYP450by the anti-coccidiosis drugs on gene and protein levels, we expected to provide theoretical support for compatibility of antibiotics and anticoccidial drugs, to base on elevation the control efficiency of rabbit coccidiosis.1. Epidemiological investigation of rabbit coccidiosis in Nantong area of Jiangsu province. Seventy five rabbit fecal samples were collected from four commercial rabbit farms (A, B, C and E) and one SPF rabbit farm (D) in Nantong area, and checked for coccidial oocysts under light microscope. The results showed that all of rabbits from the four commercial rabbit farms (A, B, C and E) were infected by different coccidians, whereas no infection was found in the SPF rabbit farm. Among the60oocyst-positive fecal samples detected, the maximal averaged infection intensity of oocyst per germ (OPG) value was38.75×104and the minimum OPG value was14.75×104. Among the10coccidian species found, the most common was E. perforans with a percentage of27.8%, followed by E. exigua (15.1%) and E. intesstinalis (10.2%). E. intestinalis was the dominant species in farm A (23.6%) and E. perforans was the dominant species in farms B, C and E (35.2%,28%and37.2%, respectively).2. Comparison of histological and enzyme activity changes of liver and duodenum between SPF and coccidian-affected commercial rabbits. The ear blood samples were collected from coccidian infected commercial New Zealand rabbits for the hepatic function index determination, including alanine transaminase (ALT), glutamic-oxal (o) acetic transaminase (AST), albumin (ALB), gamma glutamyl transferase (GGT), alkaline phosphatase (ALP). Then, liver and duodenum tissues were collected from anesthesia animals for tissue section preparation and histopathological observation. The results showed that both ALT and ALP activity of coccidian infected commercial rabbits were significantly higher (p<0.05) than that of SPF rabbits. The AST and GGT activity of the coccidian infected commercial rabbits were also significantly higher (p<0.01) than that of SPF rabbits, whereas the ALB levels of the former animals were significantly lower (p<0.05) than of SPF rabbits. Compared to that in SPF New Zealand rabbits histopathological observation showed apparent liver and duodenum pathological changes in coccidian infected commercial rabbits, including necrosis and hyperplasia of hepatocytes with disordered arrangement, thinness of the intestinal wall and endomembrane, and gradual change from the local necrosis to vacuolation in intestinal tract. The ultrastructural changes included hepatocyte necrosis and vacuole formation, sheding and fracturation of duodenum microvillus, with irregular length. These results suggest that coccidian infection is common in commercial rabbits, which has detrimental influence for use as experiment animals.3. The prophylactic treatment effect of three anti-coccidiosis drugs. Forty coccidian infected New Zealand rabbits about2months old were randomly equal divided into four groups. The control group was fed with conventional pellet feed which did not add any drugs, the three experimental groups with the pellet feed containing250mg/kg of sulfaquinoxaline (SUL) five days and after drug withdrawal five days continuous used five days,100mg/kg of robenidine (ROB) continuous used fourteen days,10mg/kg of toltrazuril (TOL) two days and after drug withdrawal eight days continuous used two days. On the tenth day, the twentieth day and the thirtieth day after feeding experiment, the levels of OPG, ALT, AST, ALB, total bilirubin (TBIL), GGT, ALP and daily bodyweight gaining were determined and the data was analyed by t tests. The results showed ROB had some anti-coccidian effect at specific period of time, but the TOL and SUL had significantly higher inhibitory effects on production and sheding of coccidian eggs, and beneficial effects on improvement of the liver function parameters of the animals.4. Influence of three anti-coccidiosis drugs on the pharmacokinetics of FFC in rabbits. Thirty two Zealand rabbits were randomly equal divided into four groups. The control group was fed with conventional pellet feed and experimental group were fed with the pellet feed containing250mg/kg of SUL,66mg/kg of ROB or2mg/kg of TOL. On day21after feeding, each group animals were injected with25mg/kg FFC, and the heart blood samples were collected within24h after injection. The concentrations of FFC were detected by high performance liquid chromatography (HPLC) and the pharmacokinetics was analyzed according to the "one compartment open model". Compared to the control group, the values of tl/2Ke and AUC were significantly decreased and the values of Ke and CL were apparently elevated in FFC+ROB group, but not in FFC+SUL group and FFC+TOL group. In addition, the Vd value was significantly higher (p<0.05) in FFC+TOL than that in the other two experimental groups. These results suggest co-administratio of ROB, but not SUL or TOL, interferes with metabolism of FFC.5. Influence of three anti-coccidiosis drugs on the enzyme activity and expression of CYP3A6in liver of rabbits. Twenty four New Zealand rabbits were randomly divided into four groups. The control group (n=6) was fed with conventional pellet feed and the experimental groups were fed with pellet feed containing250mg/kg of SUL (n=6),66mg/kg of ROB (n=8) or2mg/kg of TOL (n=8). On day21after feeding, the liver samples were collected from each group. Both the total RNA and protein samples were analyzed by real-time RT-PCR and western blot. The results showed that both CYP3A6mRNA and protein levels were significantly (p<0.05) up-regulated in both SUL-and TOL-fed groups. Detection of the metabolite1-Hydroxymidazolame of CYP3A in the liver tissues by LC-MS/MS showed that the enzyme CYP3A activity was significantly (p<0.01) elevated in the three experimental groups. These results suggest that continuous administration of SUL, ROB or TOL can induce CYP3A expression in the liver of rabbits, which was relevant to the drug metabolism. |
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