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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
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.
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.
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.
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.
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.
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)
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 .
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.
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.
Control Options • Use of antibiotics • Use of inactivated vaccines • Alternative control strategies: • Live IC vaccine • Continual disinfection
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.
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.
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.
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).
Protection Levels • Serovar A-1 85% • Serovar B-1 72% • Serovar C-2 73% • Serovar C-3 76%
Comparison Between Different Serovars Compare disease scores between vaccinated birds challenged with C-3 and unvaccinated birds challenged with A-1 or B-1.
Clinical signs in vaccinated birds challenged with serovar C-3 and unvaccinated birds challenged with serovar A-1
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.
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.
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.
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.
There is a Need for New Vaccination or Disease Control Strategy for the Control of Infectious Coryza.
New Vaccination Strategies • Live vaccines • Possible candidates • Transformed NAD independent isolates • Various deletion mutations. • Possible live vaccine candidates currently under test.
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.
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.
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.
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.
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.
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.
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.
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.
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.