avian mycoplasmosis vaccination

Avian MycoplasmosisVaccination

Plan of Talk

Introduction Live vaccines

– Live strains– Administration– Effect on respiratory tract– Effect on egg production and quality

Inactivated vaccines– Administration– Effect on MG transmission through the egg– Effects on respiratory disease

Introduction

Vaccination is the preferred method of control to maintain MG- and MS-free flocks.

Vaccination should be considered only in situations where:1. Field exposure is inevitable, such as on multi-age sites. 2. There is a potential exposure of neighboring poultry.

Types of Vaccines

Two types of vaccines are available for the control of MG:1. Live vaccines, contains mild to avirulent MG strains. 2. Inactivated oil-emulsion bacterins.

Although there is antigenic variability among MG strains, it is thought that vaccination with a single strain is sufficient.

Characteristics of Ideal MG Vaccines

1. Living vaccines should not:1. Cause disease in the vaccinated animal. 2. Be transmissible, either through the egg or horizontally to susceptible

flocks.3. Cause disease in neighboring flocks.

2. Attenuated strains should not revert to virulent form. 3. A marker which readily distinguishes vaccine strain from field

strain is a useful characteristic.4. Vaccine must be capable of stimulating solid lifelong

protection, preferably from a single dose.

Plan of Talk




Live Vaccines

The objective is to infect the flock with a mild, immunogenic MG strain at an age and time when little or no significant damage occurs.

Such exposure results in resistance to challenge later in life.

Cont. …

The virulence of a M. gallisepticum strain and the ability to stimulate a protective immune response are related characteristics.

Completely avirulent strains do not appear to stimulate the immune system.

Cont. …

Successfully vaccinated birds:1. Are resistant to respiratory disease.2. Are resistant to airsacculitis.3. Are resistant to egg production drops caused by MG.4. Reduced levels of egg transmission in breeders.

Plan of Talk




Live Vaccines – F Strain

The F strain of MG has been the most commonly used vaccine strain.

It is a naturally occurring strain of mild to moderate virulence for chickens, but it is virulent for turkeys.

It ordinarily spreads slowly from bird to bird.

Cont. …

Hens vaccinated with F strain by eye drop while in lay showed: No signs of egg transmission. F-strain was isolated from 8/352 (2.27%) eggs laid in a seven-week

period after aerosol vaccination. Lateral transmission of F strain between vaccinated birds and

unvaccinated pen mates occurred readily in 4 weeks after vaccination, but thereafter became progressively slower, although it was still occurring as late as 27 weeks after vaccination.

Cont. …

Vaccinated chickens are permanent carriers, so a single dose is adequate.

Use of F strain vaccine in each replacement flock on a multi-age site will eventually result in displacement of the field strain with the vaccine strain.

Live vaccines – ts-11 & 6/85

Strains ts-11 and 6/85 are avirulent Spread to unvaccinated birds does not occur or occurs very

poorly when birds are in very close contact.

Plan of Talk




Live Vaccines Administration Timing

Commercial pullets are usually vaccinated between 12-16 weeks of age.

In cases of probable early field exposure can be carried out in birds as young as 2-4 weeks of age.

Live Vaccines Administration Route – F strain

F strain vaccines can be administered through:1. Drinking water.2. Spray. 3. Eye drop.

Vaccination in the drinking water gave better results than vaccination by spray.

A respiratory reaction should be expected at approximately 5 -7 days after vaccination if aerosol administration is used.

It is desirable that birds are to be vaccinated at an age when there is no reaction to other respiratory vaccines.

Live Vaccines Administration Route – 6/85 and ts-11

Strain ts-11 should be administered by eye drop. Strain 6/85 is given as a fine spray. No post-vaccination reaction should be observed with 6/85 or

ts-11.

Live Vaccines Administration Dosage

F strain: 10 log 5 CFU/dose is sufficient for eye drop administration of live F strain vaccine. ts-11 strain: ≥ 10 log 7.7 color changing units (CCU)/dose 6/85 strain: 10 log 7–8 CFU/dose

Plan of Talk




Effects On The Respiratory TractF-Strain

Moderate to severe respiratory reactions - air sac lesions F strain. One-day-old broilers Administered by aerosol Combined NDV and IBV vaccines

Moderate to severe lesions F strain 90% of birds One-day-old chickens

Cont. …

little or no respiratory reaction is observed F strain Healthy chickens Administered via upper respiratory tract

Respiratory signs and air sacculitis may result F strain Administered by aerosol or in the presence of other respiratory

disease agents, such as Newcastle disease or infectious bronchitis virus.

Effects On The Respiratory Tract6/85 Strain

Mild to moderate air sac lesions in 20% to 30% of birds. Strain 6/85 Aerosol. Chickens and turkeys

Effects On The Respiratory Tractts-11 Strain

No lesions Strain ts-11 Air sac inoculation Two-week old chickens 28-week-old layer hens

No lesions Strain ts-11 Large doses into the thoracic air sacs One-day-old chickens

Cont. …

No air sac lesions up to three weeks later Day-old broilers. Aerosol. ts-11 in combination with IBV vaccine.

No respiratory signs 10 doses of ts-11 Eight-week-old chickens Eye drop Immediately following relocation by road transport, beak trimming

and fowl pox vaccination.

Cont. …

Transient mild respiratory signs and conjunctivitis Field trial involving 11,000 birds, ts-11 strain in combination with infectious laryngotracheitis (ILT) virus

vaccine (strain ILTA20) These were similar to signs observed in previous studies using ILTA20

alone (F. Gordon, unpublished findings).

Cont. …

Slight respiratory reactions Strain ts-11 Three-week-old chickens In combination with NDV/IBV vaccine

Vaccination with ts-11 has been shown not to interfere with the efficacy of NDV vaccination.

Plan of Talk




Effects on Egg Production and Quality

Egg quality parameters were unaffected F strain 45-week-old pullets Branton et al. found that the lowered production could not be

attributed to any obvious effect on oviduct structure and function

Egg production Group vaccinated with F strain produced significantly fewer eggs over

the same period.

Cont. …

Strain 6/85 There was no significant difference in the percentage of eggs laid

between vaccinated and unvaccinated birds up to peak production.

Cont. …

No significant difference egg production over the following 7 weeks

ts-11 strain Layer hens at peak production Inoculated directly into the abdominal air sacs

Plan of Talk




Inactivated Vaccines

MG bacterins are prepared from a concentrated suspension of whole cells that is emulsified into an oil adjuvant.

Cont. …

Bacterins are ordinarily used in commercial pullets to:1. Provide protection against egg-production drops that occur

after MG exposure on multi-age layer sites. 2. Reduce the level of egg transmission in breeder pullets.

Use of bacterins in broilers is limited by the fact that birds vaccinated before 1–2 weeks of age are not protected.

Cont. …

Although bacterins may provide protection against:1. Respiratory signs2. Airsacculitis3. Egg production lossesBut, vaccinated flocks are readily infected.

Cont. …

Antigen content: at harvest, the titer should be from 10 log 8 to 10 log 9 CFU/ml.

Plan of Talk




Inactivated VaccinesSite of Injection

The site of injection is important. Oil emulsion bacterins are administered either by SC or IM

injection.

Subcutaneous Injection

Chickens vaccinated subcutaneously; at the base of the skull Developed a transient oedema around the eyes

Chickens vaccinated subcutaneously; at midway or lower in the nape of the neck.

Showed no obvious adverse reaction

Intramuscular Injection

Chickens vaccinated intramuscularly; Breast muscle is preferred

Ease of administration Fewer clinical complications But this results in losses at processing

The upper leg is an alternative, But has resulted in a granulomatous cellulitus which was exacerbated

by the movement of pullets from grower to layer houses.

Inactivated VaccinesAge of Vaccination

Vaccination age effects the level of protective immunity elicited by bacterins.

Chickens vaccinated with a single dose at one week of age were protected against challenge with virulent M. gallisepticum seven weeks or three weeks later.

Chickens vaccinated with a laboratory-prepared vaccine at; One day of age demonstrated little protection Seven days old demonstrated variable protection 11 days or older demonstrated significant protection

Inactivated VaccinesNO. of Doses

An effect caused by the number of doses has been noted in some (but not all) artificial challenge studies, with two doses providing superior protection to a single dose.

Cont. …

In a field trial,

Twice-vaccinated pullets Housed to 64 weeks Laid 12.8 eggs more per hen than a control group which is

vaccinated only with F strain.

Once-vaccinated group The difference was only 3.8 eggs.

Cont. …

Two doses of bacterin during rearing; Hen-housed egg production to 66 weeks of age 7.6% to 9.1% higher than unvaccinated controls

Plan of Talk




Effect on MG Transmission Through the Egg

After aerosol challenge with virulent M. Gallisepticum, vaccination with one or two doses of bacterin delayed the onset and reduced the rate of M. gallisepticum transmission through the egg, in comparison with unvaccinated hens.

However, vaccination was not effective when administered two weeks after experimental challenge.

Effects on Egg Production

A beneficial effect in the prevention of drops in egg production associated with M. gallisepticum was confirmed in experimental pen trial studies.

In the four-week period after challenge, unvaccinated hens laid only ½ the number of eggs produced by once- or twice-vaccinated birds.

Plan of Talk




Effects on Respiratory Disease

The subcutaneous administration of bacterin was reported to reduce the number of organisms in the trachea following challenge.

Experimental use of the product developed by Hildebrand and colleagues resulted in a reduced incidence of respiratory signs following artificial challenge and improved performance of layer flocks.

Cont. …

Detailed quantitative studies showed that the mean number of M. gallisepticum isolated from the tracheas of bacterin vaccinated chickens up to 8 weeks after intra-tracheal challenge was only slightly less than that of unvaccinated controls.

While the infective dose 50% (ID50) only increased from 10 log 2.9 organisms in unvaccinated controls to 10 log 3.7 organisms in chickens receiving two doses of bacterin.

Cont. …

It was concluded that protection against respiratory infection elicited by parenteral administration of bacterin is limited and unlikely to be of practical significance.

The results corroborated field observations that the continued use of M. gallisepticum bacterin on multiple-age poultry farms had failed to eliminate the infection.

avian mycoplasmosis vaccination

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