field aspects on avian influenza diagnosis &control by prof.dr. ahmed sayed hamouda

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Field aspects on Avian Field aspects on Avian Influenza Influenza Diagnosis &Control Diagnosis &Control By By Prof.Dr. Ahmed Sayed Prof.Dr. Ahmed Sayed Hamouda Hamouda CAAVS 7 2009 CAAVS 7 2009

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Field aspects on Avian Influenza Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda. H5N1 avian influenza is being a considerable problem for both veterinary and public health. - PowerPoint PPT Presentation

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Page 1: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Field aspects on Avian Field aspects on Avian Influenza Influenza

Diagnosis &ControlDiagnosis &ControlByBy

Prof.Dr. Ahmed Sayed Prof.Dr. Ahmed Sayed HamoudaHamouda

CAAVS 7 2009 CAAVS 7 2009

Page 2: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

H5N1 avian influenza is being a H5N1 avian influenza is being a considerable problem for both considerable problem for both

veterinary and public healthveterinary and public health..

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Page 3: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

When the viruses are spread over a When the viruses are spread over a wide area and have infected wide area and have infected multiple avian species, culling and multiple avian species, culling and physical containment are not physical containment are not likely to be successfullikely to be successful..

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Page 4: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

In recent years, several vaccines In recent years, several vaccines have been developed against highly have been developed against highly pathogenic avian influenza virus pathogenic avian influenza virus (HPAI) in poultry(HPAI) in poultry . .

Their use has shown that it can protectTheir use has shown that it can protectchickens fromchickens from : :

1.1. Developing disease symptoms. Developing disease symptoms. 2.2. Dying from infection.Dying from infection.3.3. Reduce the shedding rate.Reduce the shedding rate.

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Page 5: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

In outbreaks of HPAI control In outbreaks of HPAI control measures still by killing infected measures still by killing infected birds as it is not known whether birds as it is not known whether vaccinated poultry could vaccinated poultry could ‘silently’ spread the disease, ‘silently’ spread the disease, increasing the risk of new increasing the risk of new outbreaks causing a serious outbreaks causing a serious threat to humansthreat to humans..

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Page 6: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

little was known about how HPAI was little was known about how HPAI was transmitted in chickens, or how transmitted in chickens, or how vaccines reduced transmissionvaccines reduced transmission

vaccination does not appear to block vaccination does not appear to block viral transmission completely, so viral transmission completely, so some slaughtering may also be some slaughtering may also be necessarynecessary . .

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Page 7: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Diagnosis of AI infectionDiagnosis of AI infection

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Page 8: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

infections in animal and humans has infections in animal and humans has traditionally relied on virus isolation and traditionally relied on virus isolation and identification, but this delays obtaining a identification, but this delays obtaining a

definitive diagnosis for 1 to 2 weeksdefinitive diagnosis for 1 to 2 weeks . .

Recently Recently PolymerasePolymerase chain reaction PCRchain reaction PCR)) rapid real-time PCR (RRT-PCR)rapid real-time PCR (RRT-PCR))) tests tests have been developed and used in human have been developed and used in human and animal field diagnostic situations, and animal field diagnostic situations,

respectivelyrespectively..

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Page 9: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

SamplesSamples

Samples from live birds should include:Samples from live birds should include:

Tracheal swabs.Tracheal swabs. Cloacal swabs.Cloacal swabs. Serum samples.Serum samples.

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Page 10: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Samples from dead birds should Samples from dead birds should include:include:

Intestinal contents.Intestinal contents. Faeces or cloacal swabs. Faeces or cloacal swabs. Oropharyngeal swabs. Oropharyngeal swabs. Trachea, lungs, air sacs, intestine, Trachea, lungs, air sacs, intestine,

spleen, kidney, brain, liver and heart spleen, kidney, brain, liver and heart may also be collected separately or in may also be collected separately or in pools.pools.

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Page 11: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Handling of samplesHandling of samples

The samples should be placed in The samples should be placed in isotonic phosphate buffered saline isotonic phosphate buffered saline (PBS), (PBS), pH 7.0-7.4pH 7.0-7.4, containing , containing antibiotics.antibiotics.

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Page 12: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

The The antibiotics for sample antibiotics for sample preservationpreservation

penicillin (2000 units/ml).penicillin (2000 units/ml). Streptomycin (2 mg/ml).Streptomycin (2 mg/ml). Gentamycin (50 µg/ml) Gentamycin (50 µg/ml) Mycostatin (1000 units/ml) should be Mycostatin (1000 units/ml) should be

added for tissues ,tracheal and faecal added for tissues ,tracheal and faecal swabs, but at five-fold higher swabs, but at five-fold higher concentrations for faeces and cloacal concentrations for faeces and cloacal swabs.swabs.

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It is important to readjust the pH of the It is important to readjust the pH of the solution to pH 7.0-7.4 following the solution to pH 7.0-7.4 following the addition of the antibiotics. addition of the antibiotics.

Faeces and finely minced tissues should Faeces and finely minced tissues should be prepared as 10-20% (w/v) suspensions be prepared as 10-20% (w/v) suspensions in the antibiotic solution. in the antibiotic solution.

Suspensions should be processed as Suspensions should be processed as soon as possible after incubation for 1-2 soon as possible after incubation for 1-2 hours at room temperature. hours at room temperature.

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Storage& transport of Storage& transport of samplessamples

When immediate processing is When immediate processing is impracticable, samples may be stored impracticable, samples may be stored and or transferred at 4°C for up to 4 and or transferred at 4°C for up to 4 days.days.

For prolonged storage, diagnostic For prolonged storage, diagnostic samples and isolates should be kept at samples and isolates should be kept at -80°C. -80°C.

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Page 15: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Serological detection of AISerological detection of AI

Direct RNA detection.Direct RNA detection. Agar gel immunodiffusion.Agar gel immunodiffusion. HA and HI tests. HA and HI tests. ELISA.ELISA. RT PCR.RT PCR.

  

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Page 16: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Direct RNA detectionDirect RNA detection   Rapid test Rapid test

It is a field rapid test to detect the AI It is a field rapid test to detect the AI antigen in antigen in oropharyngeal or tracheal samples oropharyngeal or tracheal samples from clinically affected or dead birds which show from clinically affected or dead birds which show good sensitivitygood sensitivity..

The test can demonstrate the presence of The test can demonstrate the presence of AI within 15 minutes. AI within 15 minutes.

It Is an antigen-capture enzyme It Is an antigen-capture enzyme immunoassay system, has been used for immunoassay system, has been used for detecting the presence of influenza A detecting the presence of influenza A viruses in poultry.viruses in poultry.

The kit uses a monoclonal antibody The kit uses a monoclonal antibody against the nucleoprotein and should against the nucleoprotein and should therefore be able to detect any influenza A therefore be able to detect any influenza A virus.virus.

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Page 17: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

The disadvantages are:The disadvantages are:

1.1.Lack sensitivity. Lack sensitivity. 2.2.It has not validated for different It has not validated for different

species of birds.species of birds.3.3.Subtype identification is not Subtype identification is not

achieved. achieved. 4.4.The kits are expensive.The kits are expensive. The test is interpreted as a flock and The test is interpreted as a flock and

not an individual bird test. not an individual bird test.

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Page 18: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Agar gel immunodiffusionAgar gel immunodiffusion  

This test is used to detect the presence of This test is used to detect the presence of influenza A virus by demonstrating the influenza A virus by demonstrating the presence of the nucleocapsid or matrix presence of the nucleocapsid or matrix antigens, both of which are common to all antigens, both of which are common to all influenza A viruses.influenza A viruses.

Precipitin lines can be detected after Precipitin lines can be detected after approximately 24-48 hours, but this may be approximately 24-48 hours, but this may be dependent on the concentrations of the dependent on the concentrations of the antibody and the antigen.antibody and the antigen.

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HA&HI testsHA&HI tests

Variations in the procedures for HA Variations in the procedures for HA and HI tests are practiced in different and HI tests are practiced in different laboratories.laboratories.

This variation may lead to miss This variation may lead to miss diagnosis and erroneous interpretation diagnosis and erroneous interpretation of the results.of the results.

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Page 20: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Haemagglutination test (HA)Haemagglutination test (HA)

The titration should be read to the highest The titration should be read to the highest dilution giving complete HA (no streaming); dilution giving complete HA (no streaming); this represents 1 HA unit (HAU) and can be this represents 1 HA unit (HAU) and can be calculated accurately from the initial range calculated accurately from the initial range of dilutions.of dilutions.   

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Haemagglutination Haemagglutination inhibition testinhibition test

HI: HI: The haemagglutination inhibition The haemagglutination inhibition test is serotype specifictest is serotype specific..Each H-subtype has an individual HI Each H-subtype has an individual HI test. Positive HI titres (> 1:8)test. Positive HI titres (> 1:8)develop a few days later than seen in develop a few days later than seen in ELISA or AGID tests; andELISA or AGID tests; andtitres persist till long after the infection. titres persist till long after the infection. The HI test is the standardThe HI test is the standardtest for all avian speciestest for all avian species..

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Page 22: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Haemagglutination inhibition test Haemagglutination inhibition test (HI)(HI)

  1.1. Dispense 0.025 ml of PBS into each well of a plasticDispense 0.025 ml of PBS into each well of a plastic V V-bottomed -bottomed microtitre plate.microtitre plate.

2.2. Place 0.025 ml of serum into the first well of the plate. Place 0.025 ml of serum into the first well of the plate. 3.3. Make twofold dilutions of 0.025 ml volumes of the serum across the Make twofold dilutions of 0.025 ml volumes of the serum across the

plate.plate.4.4.

Add Add 4 HAU4 HAU of virus/antigen in 0.025 ml to each well and leave for a of virus/antigen in 0.025 ml to each well and leave for a minimum of 30 minutes at room temperature (i.e. about 20°C) or 60 minimum of 30 minutes at room temperature (i.e. about 20°C) or 60 minutes at 4°C. minutes at 4°C.

5.5.     Add 0.025 ml of 1% (v/v) chicken RBCs to each well and after Add 0.025 ml of 1% (v/v) chicken RBCs to each well and after gentle mixing, allow the RBCs to settle for about 40 minutes at gentle mixing, allow the RBCs to settle for about 40 minutes at room temperature, i.e. about 20°C, or for 60 minutes at 4°C if room temperature, i.e. about 20°C, or for 60 minutes at 4°C if ambient temperatures are high, by which time control RBCs should ambient temperatures are high, by which time control RBCs should be settled to a distinct button. be settled to a distinct button.

6.6. The HI titre is the highest dilution of serum causing complete The HI titre is the highest dilution of serum causing complete inhibition of 4 HAU of antigen. The agglutination is assessed by inhibition of 4 HAU of antigen. The agglutination is assessed by tilting the plates. Only those wells in which the RBCs stream at the tilting the plates. Only those wells in which the RBCs stream at the same rate as the control wells (containing 0.025 ml RBCs and same rate as the control wells (containing 0.025 ml RBCs and

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Page 23: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

HI interpretationHI interpretation

HI titres may be regarded as being positive HI titres may be regarded as being positive if there is inhibition at a serum dilution of if there is inhibition at a serum dilution of 1/16 (24 or log2 4 when expressed as the 1/16 (24 or log2 4 when expressed as the reciprocal) or more against 4 HAU of reciprocal) or more against 4 HAU of antigen. Some laboratories prefer to use 8 antigen. Some laboratories prefer to use 8 HAU in HI tests. While this is permissible, it HAU in HI tests. While this is permissible, it affects the interpretation of results so that a affects the interpretation of results so that a positive titre is 1/8 (2_3 or log2 3) or more. positive titre is 1/8 (2_3 or log2 3) or more.

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Page 24: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

The following recommendation The following recommendation can be applied in the testcan be applied in the test

1.1. Use of V-bottomed microwell plastic plates in Use of V-bottomed microwell plastic plates in which the final volume for both types of test is which the final volume for both types of test is 0.075 ml.0.075 ml.

2.2. Use Use HAU of virus/antigen HAU of virus/antigen

3.3. The reagents required for these tests are isotonic The reagents required for these tests are isotonic PBS (0.1 M), pH 7.0-7.2.PBS (0.1 M), pH 7.0-7.2.

4.4. RBCs taken from a minimum of three SPF chickens RBCs taken from a minimum of three SPF chickens and pooled in an equal volume of Alsever's and pooled in an equal volume of Alsever's solution.solution.

5.5. Positive and negative control antigens and Positive and negative control antigens and antisera should be run with each test, as antisera should be run with each test, as appropriate.appropriate.

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Page 25: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Genetic Change in Influenza Genetic Change in Influenza VirusesViruses

Influenza viruses have the propensity to change Influenza viruses have the propensity to change genetically, which contributes to the interspecies genetically, which contributes to the interspecies transmission and zoonotic potential of AI viruses transmission and zoonotic potential of AI viruses Change can occur by 2 mechanisms: random Change can occur by 2 mechanisms: random mutations in the RNA genome, especially in the mutations in the RNA genome, especially in the haem agglutinin, which occur gradually over time; haem agglutinin, which occur gradually over time; and reassortment of the 8 gene segments that and reassortment of the 8 gene segments that occurs abruptly between 2 influenza viruses that occurs abruptly between 2 influenza viruses that infect a single cell, resulting in progeny that are infect a single cell, resulting in progeny that are hybrid viruseshybrid viruses..

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Page 26: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

In birds, the greatest diversity of In birds, the greatest diversity of influenza viruses (all combinations of influenza viruses (all combinations of the 16 hemagglutinin and 9 the 16 hemagglutinin and 9 neuraminidase subtypes) is found in neuraminidase subtypes) is found in (ducks and geese) and other aquatic (ducks and geese) and other aquatic birdbird

Infections in these species are usually Infections in these species are usually subclinicalsubclinical . .

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Page 27: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Immune exclusion by circulating or Immune exclusion by circulating or mucosa-bound haemagglutination-mucosa-bound haemagglutination-inhibiting (HI)inhibiting (HI)

antibodies is believed to be a major antibodies is believed to be a major contributor to protection (Suarez and contributor to protection (Suarez and Shultz-Cherry,2000)Shultz-Cherry,2000) . .

Thus, HI serum antibodies are used as Thus, HI serum antibodies are used as a reasonably reliable test marker fora reasonably reliable test marker for

measuring the protection at least in measuring the protection at least in gallinaceous birdsgallinaceous birds..

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Page 28: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Transmission and Host Transmission and Host AdaptationAdaptation

Influenza viruses manifest some host adaptation with frequent Influenza viruses manifest some host adaptation with frequent and easy transmission between individuals of the same and easy transmission between individuals of the same species or occasionally transmission to closely related species or occasionally transmission to closely related speciesspecies..For example, numerous human cases of influenza occur each For example, numerous human cases of influenza occur each year, predominantly caused by human-origin Influenza virus A year, predominantly caused by human-origin Influenza virus A strains but infrequently caused by nonhuman-origin Influenza strains but infrequently caused by nonhuman-origin Influenza virus A strains, such as swine-origin influenza A virusesvirus A strains, such as swine-origin influenza A viruses..16 On On even rarer occasions, AI viruses have been directly even rarer occasions, AI viruses have been directly transmitted from birds to humanstransmitted from birds to humans. . Furthermore, in Furthermore, in experimental studiesexperimental studies, , a few AI viruses have shown limited a few AI viruses have shown limited replication in the nasal cavity of humans. The difficulty for replication in the nasal cavity of humans. The difficulty for transmission and infection of AI virus to humans can be transmission and infection of AI virus to humans can be partially attributed to different binding efficiencies of partially attributed to different binding efficiencies of hemagglutinin of influenza viruses for surface cell receptors hemagglutinin of influenza viruses for surface cell receptors on avian or human respiratory epithelial cellson avian or human respiratory epithelial cells . .

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Page 29: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

VACCINATIONVACCINATION

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Page 30: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

An effective HPAI vaccine for poultry should not An effective HPAI vaccine for poultry should not only protect against disease but also againstonly protect against disease but also against

virus transmission (van der Goot et al., 2005). virus transmission (van der Goot et al., 2005). Efficient protection seems to depend to a largeEfficient protection seems to depend to a large

extent on antibodies which neutralise the virus and extent on antibodies which neutralise the virus and are predominantly directed against theare predominantly directed against the

haemagglutinin (HA). haemagglutinin (HA).

However, also antibodies against neuraminidase However, also antibodies against neuraminidase may neutralise the virus (Swayne et al., 2000b; may neutralise the virus (Swayne et al., 2000b; McNulty, 1986; Sylte et al., 2007)McNulty, 1986; Sylte et al., 2007)

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Page 31: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Advantages of VaccinationAdvantages of Vaccination

Vaccination reduces susceptibility to infection.Vaccination reduces susceptibility to infection.A higher dose of virus is necessary to infect the A higher dose of virus is necessary to infect the vaccinated birdsvaccinated birds

Vaccinated birds shed less virusVaccinated birds shed less virusDecreased contamination of the environmentDecreased contamination of the environmentDecreased risk of human infectionDecreased risk of human infection

Used strategically vaccination compliments a Used strategically vaccination compliments a stamping out strategy by slowing/stopping the stamping out strategy by slowing/stopping the spread of the virusspread of the virus    

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Page 32: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Traditional control measures for HPAI Traditional control measures for HPAI have centered on stamping out, have centered on stamping out, which entails the large scale culling which entails the large scale culling of infected flocks and contact flocksof infected flocks and contact flocks..

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Page 33: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

The expected advantages of The expected advantages of vaccinationvaccination

FirstlyFirstly vaccination reduces susceptibility to infection, vaccination reduces susceptibility to infection, a higher dose of virus isa higher dose of virus isnecessary for establishing an infection in vaccinated necessary for establishing an infection in vaccinated birdsbirds..SecondlySecondly there is a significant reduction in the there is a significant reduction in the amount of virus shed by infected birds, thus lessamount of virus shed by infected birds, thus lessvirus to contaminate the environment reducing the virus to contaminate the environment reducing the risk of spread to other avian species and reducing risk of spread to other avian species and reducing the occupational risk faced by poultry workersthe occupational risk faced by poultry workers..

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Page 34: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Vaccine efficacy is dependant on the Vaccine efficacy is dependant on the vaccine antigen and field virus being vaccine antigen and field virus being of the same H typeof the same H type

))homologous haemagglutininhomologous haemagglutinin.(.(

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Page 35: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Types of Inactivated Types of Inactivated VaccinesVaccines

Inactivated homologous vaccinesInactivated homologous vaccines:: These are generally autogenouslyThese are generally autogenouslyvaccines prepared from the field strainvaccines prepared from the field strain . .

Efficacy of homologous vaccines has Efficacy of homologous vaccines has been proven, however the been proven, however the disadvantage is that no serological disadvantage is that no serological distinction can be made between distinction can be made between vaccinated and field exposed birdsvaccinated and field exposed birds..

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Page 36: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Inactivated heterologous Inactivated heterologous vaccinesvaccines

These vaccines are prepared from a virus These vaccines are prepared from a virus with the same H type as the field strain with the same H type as the field strain but a different N type (heterologous but a different N type (heterologous neuramidase)neuramidase) . .

The immune response to the homologous H The immune response to the homologous H type ensures protection, while antibodies type ensures protection, while antibodies against theagainst the

neuramidase of the field virus can be used neuramidase of the field virus can be used as a markeras a marker..

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Vaccination Schedule for Vaccination Schedule for Influenza H5Influenza H5**

a. Dosage: 0.5 ml per dose in birds older than 3 weeks of age, a. Dosage: 0.5 ml per dose in birds older than 3 weeks of age, 0.25 mlper dose in younger birds0.25 mlper dose in younger birds

b. Administration: subcutaneously in the lower back of the neck b. Administration: subcutaneously in the lower back of the neck ororintramuscularly in older birdsintramuscularly in older birds..

c. Emergency Vaccination Schedulec. Emergency Vaccination Schedule::

Primary vaccination administered to all poultry irrespective of Primary vaccination administered to all poultry irrespective of ageage..Booster vaccination administered 4 – 6 weeks laterBooster vaccination administered 4 – 6 weeks later..

))If the primary vaccination was givento birds younger than 3If the primary vaccination was givento birds younger than 3weeks of age a third vaccination is recommended at 16 – 18 weeks of age a third vaccination is recommended at 16 – 18 weeks ofweeks ofageage((

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Page 38: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Vaccination of BroilersVaccination of Broilers::

Vaccination of broiler chickens that are slaughtered Vaccination of broiler chickens that are slaughtered within 7 – 8 weeks is in principle discouragedwithin 7 – 8 weeks is in principle discouraged

, ,as there is not sufficient time to develop adequate as there is not sufficient time to develop adequate immunity following a primer and booster immunity following a primer and booster vaccinationvaccination . .

However in situations where live bird tradeHowever in situations where live bird tradepredominates and meat chickens are raised for longer predominates and meat chickens are raised for longer periods thisperiods thismay be reconsidered. (In Hong Kong local meat type may be reconsidered. (In Hong Kong local meat type chickens arechickens arevaccinated at 8 and 36 days of agevaccinated at 8 and 36 days of age(.(.

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Vaccination of Replacement Vaccination of Replacement FlocksFlocks

Vaccination schedule is dependant on perceived risk Vaccination schedule is dependant on perceived risk of infectionof infection..In high risk areas (active infection) primary In high risk areas (active infection) primary vaccination (0.25 ml) isvaccination (0.25 ml) isrecommended at day old to establish immunity as recommended at day old to establish immunity as early as possibleearly as possible..Two booster vaccinations (0.5ml) are recommended Two booster vaccinations (0.5ml) are recommended

at 4 – 6 and 16at 4 – 6 and 16– – 1818 weeks of ageweeks of age..

In areas with high infection pressure revaccination at In areas with high infection pressure revaccination at midlay may beindicatedmidlay may beindicated..

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Page 40: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

killed viral vaccines are generally more killed viral vaccines are generally more stable and do not pose the risk of stable and do not pose the risk of reversion to virulence compared to live reversion to virulence compared to live vaccines, but their inability to infect cells vaccines, but their inability to infect cells and activate cytotoxic T cells makes them and activate cytotoxic T cells makes them much much less protectiveless protective. Consequently, . Consequently, they generally they generally requirerequire strong adjuvants strong adjuvants and and severaseveral l injectionsinjections to induce the to induce the required level of immunity and are usually required level of immunity and are usually effective in controlling only clinical effective in controlling only clinical signs rather than infectionsigns rather than infection..

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Page 41: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Monitoring Efficacy of Monitoring Efficacy of VaccinationVaccination

− −Assessment of vaccination should be Assessment of vaccination should be done by HI test onedone by HI test onemonth after the second vaccinationmonth after the second vaccination..

− −Test 10 - 20 serum samples per flockTest 10 - 20 serum samples per flock.. − −Require an HI titre greater than 1:16 in Require an HI titre greater than 1:16 in

more than 70% of testedmore than 70% of testedsamplessamples

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Page 42: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Monitoring for Virus Circulation in Monitoring for Virus Circulation in Vaccinated FlocksVaccinated Flocks

− −Thirty to sixty clearly identified sentinels chickens Thirty to sixty clearly identified sentinels chickens left unvaccinated must be placed in each houseleft unvaccinated must be placed in each house..

− −Ten to twenty serum samples collected from Ten to twenty serum samples collected from sentinels should be tested every 30 – 45 days sentinels should be tested every 30 – 45 days (ELISA or HI)(ELISA or HI)..

− −If the sentinels seroconvert the flock is considered If the sentinels seroconvert the flock is considered AI positiveAI positive..However, in case of HPAI infection the sentinels will However, in case of HPAI infection the sentinels will most likely die within 2-3 days of infectionmost likely die within 2-3 days of infection..

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Page 43: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

Confirmation of InfectionConfirmation of Infection

Confirmation of an AI infection in a Confirmation of an AI infection in a vaccinated flock Byvaccinated flock By

1.1. Mortality.Mortality.

2.2. Seroconversion of sentinels.Seroconversion of sentinels.

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Page 44: Field aspects on Avian Influenza  Diagnosis &Control By Prof.Dr. Ahmed Sayed Hamouda

ELISA is of limited value when multiple ELISA is of limited value when multiple serotypes of virus areserotypes of virus are

circulating (e.g. H9 in Asia)circulating (e.g. H9 in Asia)

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