| In order to provide foundation for clinic trial of the trivalent live vaccine with 4 Strains against avian coccidiosis, following Quality Standard Assembly of Veterinary Biological Products and Technical Guidelines of Veterinary Biological Products Experimental Study, using blood stools, mortality, relative weight gain rate (RWG), average intestinal lesion score and reduction of lesion scores (RLS) as indexes, fundamental research, for instance, toxicity attack dose test of mixed virulent strains, vaccine composition test, laboratory efficacy test, laboratory safety test and stability test, was studied. Results indicated that:1.14d-old SPF chicks were attacked by mixed virulent strains. When the doses of E. acervulina (Asx), each E. maxima (MSX/MSD) and E. tenella (TSX) were 20.00×104,15.00X 104 and 4.00 X104 oocysts/ per, mortality was at least 40.00%, average intestinal lesion score of duodenum, jejunum and caecum were 3.00, 2.00 and 3.00. Each of the indexes was up to the attack group requirement of efficacy test standards.2. Vaccine composition was designed by orthogonal test. Twice immunizations were at the age of 4 and 14 days respectively, and attacking on the 14th day after second immunization. With the raising of immunizing dose level, RWG, RLS and oocyst inhibition in the immune-attack group were increasing, while average intestinal lesion score was reducing. When the first immunizing doses of E. acervulina (PASX), each E. maxima (PMSX/PMSD) and E. tenella (PTSX) were at least 400.00,100.00,100.00 and 1000.00 oocysts/ per, the second immunizing doses were at least 800.00,200.00,200.00 and 2000.00 oocysts/ per, mortality was at most 10.00%, RWG was at least 80.00%, RLS was at least 70.00%, oocyst inhibition was at least 75.00% and average lesion score of 3 intestinal segments were at most 1.50. All indexes were up to the efficacy test standards. Consequently, the minimum first immunizing doses of E. acervulina (PASX), each of E. maxima (PMSX/PMSD) and E. tenella (PTSX) were 400.00,100.00,100.00 and 1000.00 oocysts/per, the minimum second immunizing doses were 800.00,200.00,200.00 and 2000.00 oocysts/per. The suggested first immunizing doses of E. acervulina (PASX), each E. maxima (PMSX/PMSD) and E. tenella (PTSX) were 600.00,150.00,150.00 and 1500.00 oocysts/per, the suggested second immunizing doses were 1200.00,300.00,300.00 and 3000.00 oocysts/per.3. First immunization was at the age of 2 to 5 days respectively. Second immunization was on the 10th day after first immunization. Attacking was on the 14th day after second immunization. With the enlargement of first immunizing age, RWG and RLS were increasing, while average intestinal lesion score was reducing. When first immunizing age was greater than 4d-old, all vaccinated chicks survived, average lesion score of 3 intestinal segments were at most 1.50. All indexes were up to the efficacy test standards. Therefor, the minimum first immunizing age was 4d-old.4. First immunization was at 4d-old, second immunizing time interval was 7 to 11d respectively, and attacking was on the 14th day after second immunization. With the extension of second immunizing time interval, RWG and RLS were increasing, while average intestinal lesion score was reducing. All vaccinated chicks survived, average lesion score of 3 intestinal segments were at most 1.50. All indexes were up to the efficacy test standards. Therefor, the minimum second immunizing time interval was 7d.5. Attacking on the 10th and 14th day after first immunization, mortality was at least 20.00%, average lesion score of caecum was at least 2.00 of the vaccinated chicks. It indicated chicks had partly immunity. Twice immunizations were at the age of 4 and 14 days respectively, and attacking on the 6th,10th,14th,28th, 42nd and 56th day after second immunization respectively. The peak of immunity was on the 14th day after second immunization, and then immunity declined. Mortality was at most 10.00%, average lesion score of 3 intestinal segments were at most 1.50. All indexes were up to the efficacy test standards. Consequently, immunity producing time was on the 6th day after second immuniazation, and immunity duration could be to last until the 56th day after second immuniazation.6. Immunizing cage-rearing and floor-rearing chicks twice at the age of 4 and 14 days respectively, attacking was on the 14th day after second immunization. All vaccinated chicks survived, average lesion score of 3 intestinal segments were at most 1.50. All indexes were up to the efficacy test standards. Average weight gain in the immune period had no significant difference between cage and floor rearing chicks (P≥ 0.05). It indicated cage-rearing and floor-rearing had no impact on the immunity and dynamiting.7. Inoculation with a single dose, a repetitive single dose and an overdose respectively, no inoculated chick die, average lesion score of 3 intestinal segments were at most 1.00. Test on the dynamiting of vaccinated chicks, no significant difference between the average weight gain of vaccinated and control group. This vaccine was up to the safety requirements of veterinary biological products.8. The characters of this vaccine had no change during retention period (10 months). Immunization in different retention period (2,3,6 and 10 months), and attacking on the 14th day after second immunization. With the extension of retention period, RWG and RLS were reducing, while average intestinal lesion score was increasing. All vaccinated chicks survived, average lesion score of 3 intestinal segments were at most 1.50. All indexes were up to the efficacy test standards. It indicated, in the condition of darkness,2 to 8℃ and 2.5% potassium bichromate solution, the retention period of this vaccine was up to 10 months. |
PDF Full Text Request