The Review of Newcastle Disease Live Vaccines Application. By: M. Abdoshah

Transcription

1 The Review of Newcastle Disease Live Vaccines Application By: M. Abdoshah

2 Introduction Only one serotype (PMV1) Maternally derived antibodies are protective All vaccines are efficacious Is vaccine protection still a problem? The answer is YES because : High viral pressure with very virulent strains Bad handling of the vaccines (questionable cold chain and vaccination techniques) Unreliable vaccination programmes

3 Designing a Vaccination Program Type of vaccine Immune statuses of the birds Disease statuses of the birds Level of protection required under local conditions

4 OIE definition of the NDV pathogenicity scale: Viscerotropic velogenic - a highly pathogenic form in which haemorrhagic intestinal lesions are frequently seen; Neurotropic velogenic - a form that presents with high mortality, usually following respiratory and nervous signs; Mesogenic - a form that presents with respiratory signs, occasional nervous signs, but low mortality Lentogenic - a form that presents with mild or subclinical respiratory infection; Asymptomatic enteric - a form that usually consists of a subclinical enteric infection.

5 Pathotyping of NDV strains Pathotype ICPI IVPI MDT (hours) Plaque formation Velogenic < 60 Yes Mesogenic Yes Lentogenic > 90 No Asymptomatic > 90 No (After Heffels-Redmann U. 1992)

6 ND Vaccine Strains Mesogenic neurotropic strain : Komarov strain Lentogenic pneumotropic strains: Hitchner B1 Lentogenic enteric strains : VG/GA La Sota Cloned La Sota Apathogenic enteric strains : Australian V4 Ulster 2C PHY.LMV.42

7 Main tropism & replication 2/ Viremia : Virus circulation in the blood 1/ Primary local replication Pneumotropic strains 3/ Main tropism of replication Enterotropic strains

8 Prevention of ND Early vaccination ( 1 to 7 days of age )? Compulsory, except if the infective pressure is low High susceptibility of young chicks to the infection BUT : Interference of vaccine virus with maternally-derived antibodies (MDA) Vaccination schedule not so easy: At the hatchery or farm Proper vaccine type & vaccination route Intervals between vaccinations Susceptibility of young chicks: post-vaccination reaction (PVR)

9 MDA In one-day-old chicks, at the hatchary or farm: Blood level of Ab related to vaccination, don t increase very well. BUT early vaccination is beneficial : Local immune response induction in respiratory tract. Protection is less sustainable than after vaccination at an older age.

10 Efficacy of HB1 vaccine administered to day-old chicks (ocular route) % protection Chickens Vaccinated Control M.D.A. with without Age (days) (after Bennejean G. et al., 1978, Av Path 7, 15-27)

11 Vaccination at the hatchary In ovo : * until recently, it killed or weakend the embryo 1- to cripple the virus by ethylmethane sulfonate 2- neutralizing antibody-ndv complex vaccine 3- reverse genetic products After hatch

12 Vaccination at the farm 1- Most live vaccines are derived from lentogenic field strains. 2- These strains have variable pathogenicity. 3- The immune response increases as the pathogenicity of the live vaccine increases. 4- Consequently PVRs are inevitable.

13 Vaccination at the farm (cont.) 5- To obtain the desired level of protection without serious reaction: * more than one form of vaccination is necessary (due to inadequate physiological capacity of chicks to respond to immunogenic stimulation). * sequential use of progressively more virulent viruses. * live virus followed by inactivated vaccine.

14 Some of the present live vaccinal strains Virus strain Phy.LMV.42 Ulster 2 C Hitchner B1 (and its clones) VG/GA La Sota (and its clones) ICPI Classification Apathogenic enterotropic Apathogenic enterotropic Lentogenic pneumotropic Lentogenic enterotropic Lentogenic pneumotropic After Heffels-Redmann U., 1992, Villegas P., 2003

15 Effective vaccination Usually induces clinical protection. Virus replication and shedding may still occur (at a reduced level). Local cellular & humoral immunity in the respiratoty tract: * Preventing infection of mucosal surface * Reducing virus replication at this site Virus invasion to the systemic tissues is blocked

16 Effective Vaccination (cont.) All birds in a flock get vaccine Spread of lentogenic viruses may be limited : 1- Individual application ( preferred but laborious ) * Eye drop * Nose drop 2- Mass application ( more convenient ) * Spray : coarse or aerosol * Drinking water

17 سرعت القای ایمنی واکسن نيوکاسل با روش های مختلف واکسيناسيون واکسن ب ١ در ۴ هفتگی چالش به روش ا ي روسل با سو یه Essex 70 تعداد مرده ها از ٣ تا جوجه 3 2 اسپری 1 تعداد زنده ها چشمی تلفات بعد از چالش ا شاميدنی کنترل روزهای بعد از واکسن (from Gough R.E. and Alexander D.J., 1973, Vet Rec, May 26th, )

18 مقایسه روش های اسپری-قطره چشمی-ا شاميدنی در واکسن نيوکاسل 6 واکسن ب ١ در سن ۴ هفتگی - جوجه SPF HI test (log2) روزهای بعد از واکسيناسيون کنترل ا شاميدنی چشمی اسپری (from Gough R.E. and Alexander D.J., 1973, Vet Rec, May 26th, )

19 Early Priming : Spray, Tracheal instillation or Drinking water HB1 in commercial broilers : 1 or 7-day-old. Ocular challenge. % protection (ED challenge) % 54% Spray 1 d 60% 20% Tracheal instillation 1 d Challenge at 35 d 67% 20% D.W. 7 d Challenge at 49 d 0% 0% Unvacc. Control (Giambrone 1985)

20 Respiratory Post-Vaccination Reactions Usual PVR from 3-6 days up to 8-12 days post-vaccination mild cough no harmful effect Unusual PVR (PVR) severe PVR: growth delay, clinical signs incl. mortality complicated PVR: superinfections (Ecoli, MG) «rolling infections»

21 Respiratory PVR (cont.) Severity varies according to : residual pathogenicity of the vaccine: ICPI of the vaccine strain health status of the chickens (carrier state...) immune status of the chickens (M.D.A....) vaccine application (size of the droplets, incomplete spraying) comfort offered to the chickens: T, NH3 level, dust, density.

22 Induced tracheal lesions with pneumotropic strains Normal image (x 20) Lymphoid Infiltration : +++ Congestion : + (x 20) Lymphoid Infiltration : +++ (x 40)Congestion : ++ AFSSA, 1999

23 Impact of ND vaccination on performances Fine spray at 1 day-old, commercial broilers Average weight (g) Pneumotropic str. Enterotropic str. Control Days of age (Van Eck and Goren, 1991)

24 Conclusion Vaccination programme : Priming & Booster Vaccination programmes will vary according to: viral pressure cost of work workers technical skills tool quality vaccine properties and quality health of the birds

25 Some Solutions for the Some Problems In ovo route of vaccination, will be an attractive alternative. Usage of enterotropic strains : 1- Lentogenic enterotropic 2- Asymptomatic enteric * tropism for the gut * don t cause PVR; at least not in the respiratory tract * vaccine take by : Spray or Eye Drop

26 Some Solutions (cont.) Cloning : * high immunogenicity + acceptable PVR Spray vaccination is : * the most rapid : 1 to 3 days * priming : the most protective of live vaccination; high and long lasting * booster : the most protective of live vaccination (after aerosol); high and long lasting Aerosol application should limit to secondary vaccination

27 Some Solutions (cont.) Spray dryings an alternative to freeze drying : * inactivation of the vaccine virus by evaporation of droplets after generation * broad droplet size ( µ ) distribution generated by the nebulizers: 1- PVR in a coarse spray for primary vaccination 2- Reduction of efficiency for secondary vaccinations

28 THANK YOU FOR YOUR ATTENTION

29 با تشكر از حضور يكايك شما همكاران گرامي