Infectious Coryza in Israel: Lessons from South Africa and Control

1. Infectious Coryza in Israel: Lessons from South Africa and Control Prof. Rob Bragg Dept of Microbial, Biochemical and Food Biotechnology University of the Free State Bloemfontein South Africa

2. Infectious coryza in Israel • In order to try and understand the situation in Israel – study case history of IC in South Africa. • IC has been an ongoing problem in South Africa. • Still not completely under control in South Africa.

3. Infectious Coryza in Israel • Appears to be serogroup C strain which is causing problems. • This situation appears similar to the situation in South Africa. • Selected for a highly virulent strain through the use of vaccines not providing protection.

4. IC in South Africa – A Brief History • First problems with IC noted in 1970’s – serogroup A. - Produced a vaccine containing A. • Vaccine changed in late 1970’s to contain serogroup A and B – controlled disease. • Started to use imported vaccines. – some control. • Increased problems in mid 1980’s – serogroup C found. Changed vaccine – problem persisted. • Serovar C-3 strain identified – modified vaccine – problem persists.

5. Characterization of SA isolates • Tested with a panel of Monoclonal antibodies – Mabs not against haemagglutinins –thus of no further use. • Serotyping of isolates obtained during the 1990s. • Testing of stored isolates from the 1970s and 1980s.

6. Serotypes in South Africa • Four different serovars found in South Africa.(A-1, B-1, C-2 and C-3). • Serovar C-3 appears to be unique to Southern Africa (recently isolated in Zimbabwe). • We have produced a serovar C-3 specific serum for serotyping. • Investigated the incidence of the different serovars over a 30 year period.

7. Changes in Incidence of Different Serovars.

8. IC in South Africa • Have demonstrated a significant change in the incidence of different serovars. (Most interesting is decrease in serovar A-1 and increase in serovar C-3). • Could be related to use of vaccines not containing serovar C-3 (Vaccines with C-3 only used in South Africa after this work)

9. IC in South Africa • No indication of any “new” serovars or serogroups found. • Did find a significant change in the incidence of the different serovars. • Have found that serovar C-3 is highly virulent. • This finding lead to the suggestion of the need for a local vaccine – particularly a vaccine containing serovar C-3 .

10. Application to Israeli Situation • Could have unique serovar (likely) – or even serogroup (unlikely). • Could have selected for as particular serovar over time through the use of vaccines which do not provide high levels of cross protection to certain Israeli strains (Highly likely). • A need for a “local vaccine” in Israel, containing one or more Israeli isolates.

11. Research Needs • Accurately determine serogroups and serovars which occur in Israel. • Try to get some indication of serovar history in Israel – investigate stored isolates. • Establish virulence of any Israeli serovar or predominate field isolate. • Establish protection levels against Israeli strains.

12. Control of IC

13. Control Options • Use of antibiotics • Use of inactivated vaccines • Alternative control strategies: • Live IC vaccine • Continual disinfection

14. Use of Antibiotics • A. paragallinarum is sensitive to wide range of antibiotics. • Not used for control of IC in South Africa due to antibiotic withdrawal times – cannot sell eggs from birds treated with antibiotics. • If antibiotics are used, ensure that the antibiotic selected is effective by doing MIC tests. • Difficult to do antibiograms due to bacterial growth requirements.

15. Vaccines • Ensure that the vaccine used contains the serovars present in the country. • Vaccination with inactivated vaccines can only take place before the birds go into production. • Vaccines should provide protection for the duration of the life of the birds.

16. Local Vaccine in South Africa • Developed local vaccine containing all four SA isolates of A. paragallinarum in aluminium hydroxide based vaccine. • Birds vaccinated at 12 weeks of age and 18 weeks of age • Extensive safety and efficacy testing of vaccine in chickens in laboratory and on two farms.

17. Results • Experimental vaccine showed better levels of protection than commercial vaccines in South Africa. • However, still got clinical signs of IC in all vaccinated chickens when challenged with serovar C-3. • This lead to further investigation (Determination of virulence of isolates).

18. Protection Against Serovar C-3

19. Protection Levels • Serovar A-1 85% • Serovar B-1 72% • Serovar C-2 73% • Serovar C-3 76%

20. Effects of Virulence on Perceived Vaccination Efficacy

21. Comparison Between Different Serovars Compare disease scores between vaccinated birds challenged with C-3 and unvaccinated birds challenged with A-1 or B-1.

22. Clinical signs in vaccinated birds challenged with serovar C-3 and unvaccinated birds challenged with serovar A-1

23. Comparison Results • Clinical signs in vaccinated chickens challenged with serovar C-3 are similar to those obtained in unvaccinated chickens challenged with serovar A-1. • Possible to think that there is a “vaccination break” with C-3, if not considering the disease profile in unvaccinated birds challenged with C-3.

24. Protection Levels • High levels of protection are seen when birds are vaccinated with the vaccine containing local isolates. • However, virulence of serovar C-3 is so high that severe clinical signs are still seen. • Current inactivated vaccines will not completely control IC problem is South Africa.

25. Local Vaccines in Australia • Australia has two unique serovars of A. paragallinarum. • Importation of vaccines into Australia is just about impossible. • Made local vaccines to control IC in Australia. • These vaccines have effectively controlled IC in Australia.

26. Application to Israel • Need to determine virulence of Israeli isolates. • Need to determine protection levels provided by Israeli vaccines against Israeli isolates using new challenge model. • Need to investigate the incorporation of any new local strain into the Israeli vaccine.

27. There is a Need for New Vaccination or Disease Control Strategy for the Control of Infectious Coryza.

28. New Vaccination Strategies • Live vaccines • Possible candidates • Transformed NAD independent isolates • Various deletion mutations. • Possible live vaccine candidates currently under test.

29. Alternative Disease Control Strategies • Improve biosecurity • Use of continual disinfection with a non-toxic, highly effective disinfectant which can be used through-out the production cycle to reduce pathogen load.

30. Continuous Disinfection Program Consists of: • Hard surface disinfection before placement. • Continuous treatment and disinfection of drinking water throughout the production period. • Daily spraying or fogging of birds with a disinfectant throughout the production period.

31. Requirements of Disinfectant to use in Continuous Disinfection • Highly effective against pathogens – even at low dilutions. • Non-toxic to birds at application rates. • Should have no negative effects on production parameters. • Should be specifically registered for these applications.

32. Modified DDAC based disinfectant • This disinfectant is a unique patented modification of a DDAC based disinfectant. • Modification has boosted the efficacy against viruses, bacteria and fungi. • Modification has reduced toxicity of this disinfectant. • Low toxicity and high efficacy has allowed for the development of continual disinfection program.

33. Experimental Design • Groups of vaccinated and unvaccinated commercial layers were challenged with different serovars of A. paragallinarum. • One group of chickens received no this disinfectanttreatment (control) while the other group received a constant dose of 100 ppm of this disinfectantin the drinking water plus a daily spraying with a 1% of this disinfectantsolution.

34. Experimental Design • Clinical signs were recorded in each group and the mean daily disease scores were plotted. • The mean daily disease score was calculated and this can be used to evaluate the effectiveness of this disinfectanttreatment. • The experiment was repeated a number of times until each of the different NAD dependent and NAD independent serovars of A. paragallinarum which occur in SA were tested.

35. Challenge Results

36. Challenge Results

37. Mean Disease ScoresNAD Dependent IsolatesVaccinated Chickens

38. Mean Disease ScoresNAD Dependent IsolatesUnvaccinated Chickens

39. Conclusions • The South African Serovar C-3 has been shown to be highly virulent. • High levels of protection with current vaccines have been demonstrated. • High virulence of C-3 is capable of braking through even high levels of protection.

40. Conclusions • Inactivated vaccines unlikely to completely control IC in South Africa. • Need for new vaccination strategy and disease control strategy. • Working on live IC vaccines. • Demonstrated that continual disinfection with a highly effective non toxic disinfectant reduces clinical disease.

41. Control Options in Israel • If local serovars are of moderate virulence – a local vaccine could control the disease – as is the case in Australia. • If local strains are highly virulent – local vaccine might not control the disease – case in South Africa. • Need to investigate other options for the control of IC such as live vaccines or the continual disinfection program.

42. Thank you.