(Aujeszky’s Disease Vaccine (Inactivated) for Pigs, Ph. Eur. monograph 0744)
1 DEFINITION
Aujeszky’s disease vaccine (inactivated) for pigs is a preparation of a suitable strain of Aujeszky’s disease virus, inactivated while maintaining adequate immunogenic properties, or a preparation of an inactivated fraction of the virus
having adequate immunogenic properties. This monograph applies to vaccines intended for the active immunisation of pigs and for passive protection of their progeny against Aujeszky’s disease.
2 PRODUCTION
2-1 PREPARATION OF THE VACCINE
The vaccine virus is grown in cell cultures. The viral suspension is harvested and inactivated; it may be treated to fragment the virus and the viral fragments may be purified and concentrated. The vaccine may be adjuvanted. 2-2
2-2 SUBSTRATE FOR VIRUS PROPAGATION
2-2-1 Cell cultures
The cell cultures comply with the requirements for cell cultures for the production of vaccines for veterinary use (5.2.4).
2-3 CHOICE OF VACCINE COMPOSITION
The vaccine is shown to be satisfactory with respect to safety (5.2.6) and efficacy (5.2.7) for the pigs for which it is intended.
The following tests for safety (section 2-3-1) and immunogenicity (section 2-3-2) may be used during the demonstration of safety and efficacy.
2-3-1 Safety
2-3-1-1 Laboratory tests. Carry out the tests for each route and method of administration to be recommended for vaccination and where applicable, in pigs of each category for which the vaccine is intended (sows, fattening pigs), using in each case pigs not older than the minimum age to be recommended for vaccination. Use a batch of vaccine containing not less than the maximum potency that may be expected in a batch of vaccine.
2-3-1-1-1 General safety. For each test, use not fewer than 8 pigs that do not have antibodies against Aujeszky’s disease virus. Administer to each pig 1 dose of the vaccine. If the schedule to be recommended requires a 2 dose, administer another dose after an interval of at least 14 days. Observe the pigs at least daily until 14 days after the last administration. If the test is carried out in pregnant sows, observe the sows until 1 day after farrowing.
The vaccine complies with the test if no pig shows abnormal local or systemic reactions or dies from causes attributable to the vaccine during the test. If the test is carried out in pregnant sows, no adverse effects on gestation or the offspring are noted.
2-3-1-1-2 Safety in the pigs used in tests 2-3-2 for immunogenicity. The pigs used in the tests for immunogenicity are also used to evaluate safety. Measure the body temperature of each vaccinated pig at the time of vaccination and 6 h, 24 h and 48 h later. Examine the injection site at slaughter for local reactions.
The vaccine complies with the test if no pig shows:
— a temperature rise greater than 1.5 °C and the number of pigs showing a temperature greater than 41 °C does not exceed 10 per cent of the group;
— other systemic reactions (for example, anorexia);
— abnormal local reactions attributable to the vaccine.
2-3-1-2 Field studies. The pigs used for field trials are also used to evaluate safety. Carry out a test in each category of pigs for which the vaccine is intended (sows, fattening pigs). Use not fewer than 3 groups each of not fewer than 20 pigs with corresponding groups of not fewer than 10 controls. Measure the body temperature of each vaccinated pig at the time of vaccination and 6 h, 24 h and 48 h later. Examine the injection site at slaughter for local reactions.
The vaccine complies with the test if no pig shows:
— a temperature rise greater than 1.5 °C and the number of pigs showing a temperature greater than 41 °C does not exceed 25 per cent of the group;
— abnormal local reactions attributable to the vaccine.
2-3-2 Immunogenicity
A test is carried out for each route and method of administration to be recommended, using in each case pigs of the age to be recommended for vaccination. The vaccine administered to each pig is of minimum potency. 2-3-2-1 Vaccines intended for active immunisation. Use for the test not fewer than 15 fattening pigs that do not have antibodies against Aujeszky’s disease virus. The body mass of none of the pigs differs from the average body mass of the group by more than 20 per cent. Vaccinate not fewer than 10 pigs, according to the schedule to be recommended.
Maintain not fewer than 5 pigs as controls. At the end of the fattening period (80-90 kg), weigh and challenge each pig by the intranasal route with a sufficient quantity of virulent Aujeszky’s disease virus (challenge with at least 10 CCID50 of a virulent strain having undergone not more than 3 passages and administered in not less than 4 mL of diluent has been found to be satisfactory). The titre of excreted virus is determined in swabs taken from the nasal cavity of each pig daily from the day before challenge until virus is no longer detected. Each pig is weighed 7 days after challenge or at the time of death if this occurs earlier and the average daily gain is calculated as a percentage. For each group (vaccinated and controls), the average of the average daily gains is calculated.
The test is invalid unless all the control pigs display signs of Aujeszky’s disease and the average of their daily gains is less than -0.5 kg. The vaccine complies with the test if:
— all the vaccinated pigs survive and the difference between the averages of the daily gains for the 2 groups is not less than 1.5 kg;
— the geometrical mean titres and the duration of excretion of the challenge virus are significantly lower in vaccinates than in controls.
2-3-2-2 Vaccines intended for passive immunisation. If the vaccine is intended for use in sows for the passive protection of piglets, the suitability of the strain for this purpose may be demonstrated by the following method.
Use for the test not fewer than 12 sows that do not have antibodies against Aujeszky’s disease virus. Vaccinate not fewer than 8 sows, according to the schedule to be recommended. Maintain not fewer than 4 sows as controls. At 6-10 days of age, challenge the piglets from the sows with a sufficient quantity of virulent Aujeszky’s disease virus. Observe the piglets at least daily for 21 days.
The test is not valid if the average number of piglets per litter for each group is less than 6. The vaccine complies with the test if not less than 80 per cent protection against mortality is found in the piglets from the vaccinated sows compared to those from the control sows.
2-4 MANUFACTURER’S TESTS
2-4-1 Residual live virus
The test for residual live virus is carried out using 2 passages in the same type of cell culture as that used in the production of the vaccine or cells shown to be at least as sensitive. The quantity of inactivated virus harvest used in the test is equivalent to not less than 25 doses of the vaccine. The inactivated virus harvest complies with the test if no live virus is detected.
2-4-2 Batch potency test
It is not necessary to carry out the potency test (section 3-3) for each batch of vaccine if it has been carried out using a batch of vaccine with a minimum potency. The test described under Potency is carried out for a given vaccine, on one or more occasions, as decided by or with the agreement of the competent authority. Where this test is not carried out, an alternative validated method is used, the criteria for acceptance being set with reference to a batch of vaccine that has given satisfactory results in the test described under Potency.
3 BATCH TESTS
3-1 Identification
The vaccine contains the antigen or antigens stated under Definition.
3-2 Bacteria and fungi
The vaccine, including where applicable the diluent supplied for reconstitution, complies with the test for sterility prescribed in the general monograph Vaccines for veterinary use (0062).
3-3 Potency
The vaccine complies with the requirements of the test described below when administered by a recommended route and method.
Use for the test not fewer than 10 pigs weighing 15-35 kg and that do not have antibodies against Aujeszky’s disease virus or against a fraction of the virus. The body mass of none of the pigs differs from the average body mass of the group by more than 25 per cent. Vaccinate not fewer than 5 pigs with 1 dose of the vaccine. Maintain not fewer than 5 pigs as controls. After 3 weeks, weigh each pig, then challenge them by the intranasal route with a sufficient quantity of virulent Aujeszky’s disease virus. Weigh each animal 7 days after challenge or at the time of death if this occurs earlier and calculate the average daily gain as a percentage. For each group (vaccinated and controls), calculate the average of the average daily gains.
The test is invalid unless all the control pigs display signs of Aujeszky’s disease and the average of their daily gains is less than -0.5 kg. The vaccine complies with the test if the vaccinated pigs survive and the difference between the averages of the daily gains for the 2 groups is not less than 1.1 kg.
