1. Vaccinations at 14–21 days are optional. A single drinking water application for Newcastle disease/bronchitis is also common. A This is an example of a vaccination program. Individual programs are highly variable and reflect local conditions, disease prevalence, severity of challenge, and individual preferences.
  2. 11.Keep proper records on mortality and its causes and the treatment given to birds. Dates of vaccination for each flock should be properly recorded. 12.Rats are important carriers of poultry disease. Use suitable rat poisons/rat traps. 13.Many poultry medicines can be given in drinking water. When medication is to be given, remove the.

The protective effect of various Salmonella vaccines regimens against an experimental Salmonella Gallinarum challenge (SGNalr strain at 12 wk of age) was evaluated in two experiments. In Experiment 1 commercial brown layers were vaccinated according to one of the following programs: (i) two doses of a SE bacterin (Layermune SE; group 1); (ii) a first dose of a live SG9R vaccine (Cevac SG9R) followed by a SE bacterin (Layermune SE; group 2); (iii) one dose of each of two different multivalent inactivated vaccines containing SE cells (Corymune 4 & Corymune 7; group 3) or (iv) not vaccinated (group 4). In Experiment 2, broiler breeders were given the same vaccination treatments except for the group vaccinated with the multivalent vaccines. Overall, in both experiments, all vaccination schemes were effective in reducing mortality after challenge with a SG field strain. Primary vaccination with an initial dose of a live SG9R vaccine followed some weeks later by a dose of an inactivated SE bacterin was the most effective (p<0.05) vaccination program against mortality induced by field SG experimental challenge in both experiments. In conclusion, Salmonella vaccination programs containing SE bacterins alone or in combination with a live SG9R vaccine are effective in preventing mortality induced by infection of field SG. Nevertheless, it is important to emphasize that any vaccination program against any Salmonella serotype will only be effective if it is part of a sound and comprehensive biosecurity program designed for Salmonella control in poultry farms.

Fowl Typhoid; killed Salmonella vaccines; live Salmonella vaccines; Salmonella Gallinarum; Salmonella Gallinarum challenge

Efficacy of several Salmonella vaccination programs against experimental challenge with Salmonella gallinarum in commercial brown layer and broiler breeder hens

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Paiva JB deI; Penha Filho RACI; Argüello YMSI; Silva MD daI; Gardin YII; Resende FIII; Berchieri Junior AI; Sesti LIII

IAvian Pathology Group. FCAV/Unesp, Jaboticabal, SP, Brazil

IICEVA SANTÉ ANIMALE - Libourne Cedex, France, 35501

IIICEVA SAÚDE ANIMAL - Paulínia, SP, Brazil

Mail Address

ABSTRACT

The protective effect of various Salmonella vaccines regimens against an experimental Salmonella Gallinarum challenge (SGNalr strain at 12 wk of age) was evaluated in two experiments. In Experiment 1 commercial brown layers were vaccinated according to one of the following programs: (i) two doses of a SE bacterin (Layermune SE; group 1); (ii) a first dose of a live SG9R vaccine (Cevac SG9R) followed by a SE bacterin (Layermune SE; group 2); (iii) one dose of each of two different multivalent inactivated vaccines containing SE cells (Corymune 4 & Corymune 7; group 3) or (iv) not vaccinated (group 4). In Experiment 2, broiler breeders were given the same vaccination treatments except for the group vaccinated with the multivalent vaccines. Overall, in both experiments, all vaccination schemes were effective in reducing mortality after challenge with a SG field strain. Primary vaccination with an initial dose of a live SG9R vaccine followed some weeks later by a dose of an inactivated SE bacterin was the most effective (p<0.05) vaccination program against mortality induced by field SG experimental challenge in both experiments. In conclusion, Salmonella vaccination programs containing SE bacterins alone or in combination with a live SG9R vaccine are effective in preventing mortality induced by infection of field SG. Nevertheless, it is important to emphasize that any vaccination program against any Salmonella serotype will only be effective if it is part of a sound and comprehensive biosecurity program designed for Salmonella control in poultry farms.

Keywords: Fowl Typhoid, killed Salmonella vaccines, live Salmonella vaccines, Salmonella Gallinarum, Salmonella Gallinarum challenge.

INTRODUCTION

Salmonella enterica serovar Gallinarum (SG) is the etiologic agent of Fowl Typhoid, a severe systemic disease of chickens and other galliform birds (Shivaprasad, 2000). Salmonella Gallinarum is a non-motile hostspecific bacterium in domestic poultry. Infection in chickens occurs at all ages and is characterized by severe hepatomegaly and splenomegaly accompanied by liver with bronzing aspect, anemia, and septicemia (Shivaprasad, 2000). The disease is dose-dependent and differences in pathogenicity may be found depending upon the susceptibility of the infected genetic line of chickens (Oliveira et al., 2005).

S. Gallinarum is primarily associated with the mononuclear phagocyte system and resides prematurely within macrophages in the liver and spleen. SG can be found in the gastrointestinal tract early in the infection after oral contamination or at the final stage when the birds are dying (Barrow et al., 1994; Wigley et al., 2002). Regarding the epidemiology of fowl typhoid, the most important transmission route is horizontal, and very little information is available on direct evidences of transmission of the pathogen through the eggs to the progeny (Hall, 1949). S. Gallinarum infection generally results either in mortality of susceptible birds or bacterial clearance in resistant birds within three to four weeks of the initial infection, although occasionally persistent infection may occur (Wigley et al., 2002; Wigley, 2004).

Mortality and morbidity rates due to Fowl Typhoid may reach up to 80%. Fowl typhoid has been eradicated from Australia, North America, and most European countries, where rigorous biosecurity and specific control programs including vaccination and good management practices have been largely applied. However, it is still of considerable economic importance in many countries of Africa, Asia, and Central and South America (Pomeroy & Nagajara, 1991; Lee et al., 2003). The most effective means of control is a combination of stringent biosecurity and management procedures and eradication (Calnek et al., 1997). Removal of birds that had died from disease from the environment, reduced the resultant mortality/morbidity and is regarded as a very useful measure for control of the Fowl Typhoid (Oliveira et al., 2005).

Vaccination to prevent or reduce Salmonella infection in poultry has been accepted worldwide. Presently in Brazil there are commercially available Salmonella Enteritidis (SE) bacterins and live attenuated Salmonella Gallinarum vaccines. Commercial layer and broiler industries in Brazil have gradually accepted routine vaccination as a preventive intervention method to reduce the Salmonella in industrial farms.

SE bacterins contain bacteria organisms that were inactivated and suspended in water-in-oil or aluminum hydroxide adjuvant. Bacterins stimulate high levels of circulating antibodies in commercial layers, which persist into the laying period (Timms et al., 1990; Barbour et al., 1993; Timms et al., 1994). Those SE bacterins provide cross-protection against S. Gallinarum and other serotypes. Some disadvantages of bacterins are the labor cost for administration and the post-vaccination stress due to tissue reaction at the site of injection, which is caused by the release of bacterial cell wall endotoxins subsequent to vaccine antigen metabolization in the birds (Nakamura et al., 1994).

For fowl typhoid prevention, inactivated Salmonella vaccines and live SG vaccine using the 9R strain have been introduced (Lee et al., 2005). Killed vaccines can be efficacious in reducing Salmonella in poultry. They are safe because there is no reversion to virulence, no spreading in the environment and are considered good enough to protect chickens when applied in large-scale poultry production (Barrow et al., 1991; De Buck et al., 2004). Nevertheless, live vaccines are considered to have advantages over killed vaccines as far as induced immunity is concerned (Van Immerseel et al., 2005). Live vaccines, by causing the expression of all appropriate antigens in vivo, induce better protection against Salmonella because they stimulate both cellmediated and humoral immunity and expression of all appropriate antigens in vivo, while inactivated ones mainly stimulate the production of antibodies only against the antigens present at the time of in vitro harvesting (Collins, 1974; Gast et al., 1993; Barrow & Wallis, 2000). Killed vaccines may also be rapidly destroyed and eliminated from the host, and they are generally considered as unable to induce activation of cytotoxic T cells (Barrow & Lovell, 1991; Nagajara & Rajashekara, 1999). It is widely accepted that cellmediated immunity is more important than humoral responses in the protection against Salmonella, especially in infections caused by host-specific serotypes (Collins, 1974; Mastroeni et al., 1993; Van Immerseel et al., 2005; Barrow, 2007).

The strain 9R of SG is routinely administered to chickens in countries with endemic fowl typhoid (Smith, 1956; Shivaprasad, 2000). The 9R strain developed in the 1950s has a semi-rough lipopolysaccharide structure that reduces the virulence of that microorganism (Smith, 1956 a,b; Silva et al., 1981; Silva, 1984; Feberwee et al., 2001a,b). This vaccine may also provide some protection against Salmonella Enteritidis and Salmonella Typhimurium (Barrow et al., 1991; Audisio & Terzolo, 2002; Tan et al., 2008ab). SG9R vaccine presented acceptable safety and efficacy in young layer hens even when administered at 4 weeks of age (Lee et al., 2005). In addition, no evidence of fecal shedding of the vaccine strain was found (Feberwee et al., 2000). However, there have been reports of SG9R vaccine strain fecal shedding for a maximum time of 24 hours after vaccination (Silva et al., 1981).

Live vaccine 9R strain induces cellular and humoral responses in chickens, and both immune responses reach their peaks at similar times. Bacterial clearance three weeks post-vaccination coincides with an increase in circulating anti-Salmonella antibodies, increased cytotoxic T cell proliferation directed to Salmonella cells, and increased expression of interferon gamma (Wigley et al., 2005). A slight increase in the expression of the pro-inflammatory cytokine interleukin-Iβ was detected early in the infection (Wigley et al., 2005).

Some primary breeder and commercial layer producers administer the live SG or ST vaccine early in the pullets' life, followed by a SE bacterin at the end of rearing (Nassar et al., 1994; Schaller, 1996; Cookson & Maiers, 2004). The combined use of live and killed vaccines had not been studied at that time, but a broader range of protection against other serotypes with this live/killed vaccine approach would certainly be expected.

This study assessed the efficacy of commercial killed SE vaccines alone or in combination with a commercial live SG9R vaccine in controlling an experimental SG challenge.

MATERIAL AND METHODS

Birds

Female birds from a commercial strain of brown table-egg layers (Dekalb white; Granja Planalto, Uberlândia, MG, Brazil) were used in the Experiment 1. Brown layers are highly susceptible to Salmonella Gallinarum infections (Berchieri Jr. et al., 2000; Freitas, et al., 2007). In Experiment 2, female birds from a commercial strain of broiler breeders (Cobb 500; Cobb-Vantress Brasil, Guapiaçú-SP-Brazil) were used. They were obtained at one day of age and were reared and fed according to the recommendations of the production manuals of each strain.

At arrival, all birds were inspected according to Zancan et al. (2000) to confirm if they were free from Salmonella sp infection and antibodies against SE.

All birds were housed in the same house in separate sets of five cages containing 6 birds each (Experiment 1) or sets of four cages containing 5 birds each (Experiment 2). Experiment 2 was carried out first, and there was a downtime period of few weeks for cleaning and disinfection before Experiment 1 started.

Vaccines

The vaccines used were commercial vaccines produced by CEVA-Phylaxia (Cevac Corymune 4K & 7K; Budapest, Hungary), CEVA Biomune (Layermune SE; Lenexa, USA), and CEVA Campinas (Cevac SG9R; Campinas, Brazil).

Cevac Corymune 4K contains an inactivated combination of Avibacterium paragallinarum serotypes A, B and C, and Salmonella Enteritidis strain, homogenized with aluminum hydroxide adjuvant and thiomersal as a preservative. Cevac Corymune 7K contains an inactivated combination of Avibacterium paragallinarum serotypes A, B and C, Salmonella Enteritidis strain, La Sota strain of Newcastle Disease virus, Massachussetts strain of the Infectious Bronchitis virus, and B8/78 strain of the EDS virus, homogenized with oil adjuvant and thiomersal as a preservative. Layermune SE is an inactivated bacterial vaccine (bacterin) that contains multiple selected strains of Salmonella Enteritidis (SE) in oil adjuvant. Cevac SG9R contains live Salmonella Gallinarum strain (strain 9R; at least 107 CFU per dose) naturally attenuated and non-pathogenic for chicken, in freeze-dried form.

At 5 and 9 weeks of age, birds in each group were either vaccinated intramuscularly in the breast muscle (Cevac Corymune 4K & 7K and Layermune SE) or subcutaneously in the dorsal lower part of the neck (Cevac SG9R) as recommended by the manufacturers.

Challenge

A virulent Salmonella Gallinarum 9S strain, isolated from diseased chickens was used. A spontaneous mutant isolate resistant to nalidixic acid (SGNalr) was used to allow recovery.

The inocula consisted of overnight cultures in LB broth (DIFCO-244620) prepared in shaking incubator (100rev/min) at 37ºC for 24h. These cultures contained approximately 8x108 colony forming units (CFU)/mL.

At 12 weeks of age all chickens were orally inoculated directly into the crop with 2mL of a broth culture of the bacterial strain.

Experimental design

For the two experiments, mortality was recorded over a period of 28 days post-infection. Mortality rates were analyzed using the Chi-Square test (p<0.05).

RESULTS

All birds in both experiments were completely negative for Salmonella spp at arrival.

Experiment 1. Cumulative mortality data in commercial brown layer hens are shown in Table 1 and Figure 1. A considerable reduction in mortality was observed in the groups of birds vaccinated with SE inactivated vaccines (Groups 1 and 3; p<0.05). No mortality occurred in brown layer hens vaccinated with a live SG9R vaccine (Cevac SG9R) plus an inactivated bacterin (Layermune SE).

Experiment 2. Cumulative mortality data in broiler breeder hens are shown in Table 2 and Figure 2. Both vaccination schemes reduced mortality during the fourweek period after challenge. However, protection was significant (lower mortality; p<0.05) only in birds vaccinated initially with the live SG9R vaccine (Cevac SG9R) followed by a dose of the inactivated SE vaccine (Layermune SE).

DISCUSSION

The primary source of S. Gallinarum infection in poultry flocks is other infected poultry and vertical transmission; thus, introduction of these organisms in poultry flocks can be reasonably well controlled by standard biosecurity measures to minimize the risk of contact with infected flocks or people, equipment, and other fomites that may have originated from an infected site (Shivaprasad, 2003). However, in high field infection pressure farms, particularly multiage ones, vaccination presents an additional and effective control tool (Barrow, 2007).

Killed vaccines have been used to control Salmonella infections in poultry with variable success. Killed vaccines protect chickens against massive Salmonella challenge (particularly the non-typhoid serotypes) at any age (Timms et al., 1994). Nonetheless, they may reduce but not totally eliminate the microorganism from internal organs (Gast et al., 1993), perhaps because humoral immunity alone is unlikely to fully protect against SE, as complete protection against Salmonella requires the induction of both humoral and cellular immunity (Miyamoto et al., 1999). Notwithstanding, the recent development of novel adjuvant technology is very promising for the development of totally safe, inactivated Salmonella vaccines capable of inducing potent immune stimulation targeting different weapons of the chickens' immune system (Barrow, 2007).

It has been proposed that cell-mediated immunity is more important than humoral immunity for tissue clearance of Salmonella, whereas humoral responses seem to be the key in reducing intestinal colonization (Hassan & Curtiss 1994; Barrow & Wallis, 2000; Babu et al., 2004 ). An ideal vaccine should promote protection of birds against mucosal and systemic infection by effectively stimulating both immune responses (Van Immerseel et al., 2005). Although some authors (Barrow & Wallis, 2000; Meyer et al., 1992, Zhang-Barber, 1999) demonstrated that killed Salmonella vaccines induce only partial immune response, in the present work this response was good enough to significantly prevent mortality in the groups of birds challenged with a virulent SGNalr strain (p< 0.05). These findings are very interesting since the same vaccines were also assessed against a SE challenge and demonstrated significant efficacy (Penha Filho et al., unpublished data). Salmonella Gallinarum and Salmonella Enteritidis belong to the same serogroup (D1) and share the same 'O' somatic antigenic formula (1,9,12; Ewing, 1986) which explains the cross protection provided by the SE bacterin against SG (Kingley & Baumler, 2000). It has been demonstrated that Salmonella vaccines can elicit crossimmunity against members of the same serogroup. The ability of a SE bacterin to cross protect against other Salmonella has been demonstrated by field use in Latin America (Norton & Lozano, 1997). In an endemically SG-contaminated layer farm, cumulative mortality by Fowl Typhoid during an 11 wk period was significantly lower in a house where birds were vaccinated with a SE bacterin (1.8 % mortality) as compared to the average mortality in non-vaccinated houses (8.1% mortality; Norton and Lozano, 1997).

According to Liu et al. (2001), inactivated vaccines can decrease SE fecal excretion and that effect may depend on their composition. A study conducted by Barbour et al. (1993) comparing six inactivated SE vaccines showed variable reduction in SE fecal excretion. The same was observed by Freitas et al. (2008) comparing three commercial SE bacterins. These authors suggested that several factors could be responsible for this effect, such as adjuvant type and composition, Salmonella Enteritidis strain, inactivation method, etc. These factors could explain the different protection results observed in birds vaccinated with Layermune SE or Corymune bacterins in Experiment 1, although in the present study a SG and not a SE challenge was used. There is very scarce information on the effectiveness of Salmonella Gallinarum inactivated bacterins. In the recent article of Haider et al. (2007), it was demonstrated that a SG bacterin made from field isolates was able to induce significant seroconversion, although no information was provided in regard to protection against an experimental challenge.

In the present experiments, the best protection was observed in groups of birds vaccinated with the live SG 9R vaccine. Vaccination against host-specific Salmonella serotypes that cause severe systemic disease induces strong serotype-specific protective immunity (Smith, 1956; Barrow & Wallis, 2000).

A number of studies (Smith, 1956; Harbourne, 1957; Gordon & Luke, 1959; Gordon et al., 1959; Lee et al., 2005) have shown that the SG9R vaccine strain as an effective means for fowl typhoid prevention. Mortality in highly susceptible chicks exposed to virulent strains of S. Gallinarum was limited by SG9R vaccine (Silva et al., 1981). Lee et al. (2005) showed that a 9R vaccine provided excellent protection and is safe for vaccination of 4 week-old chickens. Indeed, in the present studies, birds that received the SG9R strain by subcutaneous route showed no evidence of disease, while SGNalr challenge strain was highly virulent to both genetic lines of birds assessed.

In this study we did not find any differences in the protection induced by the SG9R vaccine among the genetic lines used in both experiments. However, the vaccination program with two doses of an inactivated SE bacterin (Layermune SE + Layermune SE) apparently had lower effectiveness, which may indicate lower susceptibility to fowl typhoid by meat-type chickens. Regardless possible differences in susceptibility to a SG challenge and despite of the genetic evolution of commercial bird lines throughout the past decades, the present situation is similar to that previously described by Gordon et al. (1959). Notwithstanding Bumstead et al. (1993) state that the modern genetic lines of commercial birds exhibit different patterns of immunity to Salmonella.

There is quite little scientific information available in literature on the control of Fowl Typhoid through vaccination programs adopting live and inactivated Salmonella vaccines. However, several published experiments indicate that such combination programs using live (including the SG9R strain) plus inactivated Salmonella vaccines can be very effective against SE infections in layer hens (Nassar et al., 1994; Schaller, 1996; Cookson & Maiers, 2004). It is not possible to directly compare our study with the previously mentioned SE experiments as the vaccination schemes and vaccines used are quite different. However, it stands very clear that the combination of an initial live Salmonella vaccine followed some weeks later by an inactivated product may be a very useful and effective program in preventing fowl typhoid.

In conclusion, vaccination programs containing SE bacterins alone or in combination with a live SG9R vaccine induced variable protection against mortality caused by infection of field SG, depending on the specific vaccination program used. Bacterins only, although having significantly decreased mortality in challenged brown layers, did not have a significant effect on broiler breeder hens. The combination of an initial dose of a live SG9R vaccine followed some weeks later by a dose of an inactivated SE bacterin was the most effective vaccination program.

Nevertheless, it is crucial to emphasize that any vaccination program against any Salmonella serotype will only be effective if it is part of a sound and comprehensive biosecurity program designed for Salmonella control.

Acknowledgements

The authors would like to express their sincere thanks to Miss Adriana Almeida for her invaluable technical assistance in the laboratory and research facilities.

Arrived: January/2009

Approved: February/2009

Complete vaccination program for gamefowl
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  • Wigley P, Hulme S, Powers C, Beal R, Smith A, Barrow P. Oral infection with the Salmonella enterica serovar Gallinarum 9R attenuated live vaccine as a model to characterise immunity to fowl typhoid in the chicken. BMC Veterinary Research 2005; 1:1-6.
  • Zancan FB, Berchieri Jr A, Fernandes SA, Gama NMSQ. Salmonella spp investigation in transport box of day old birds. Brazilian Journal of Microbiology 2000; 31:230-232.
  • Zhang-Barber L, Turner AK, Barrow PA. Vaccination for control of Salmonella in poultry. Vaccine 1999; 17:2538-2545.
  • Luiz Sesti Ceva
    Paulinia, SP, Brasil
    E-mail:
  • Publication in this collection
    17 June 2009
  • Date of issue
    Mar 2009

I have started a series of articles on LinkedIn on various aspects of Poultry Industry. Purpose is to educate colleagues on LinkedIn about the different segments of Poultry Industry as a whole. Some of the contents are taken from reliable sources as well.

Vaccination plays an important part in the health management of the poultry flock. There are numerous diseases that are prevented by vaccinating the birds against them. A vaccine helps to prevent a particular disease by triggering or boosting the bird’s immune system to produce antibodies that in turn fight the invading causal organisms.

A natural invasion that actually causes the disease will have the same result as the bird will produce antibodies that fights the current invasion as well as to prevent future invasions by the same causal organisms. Unfortunately birds that become diseased usually become unthrifty, non-productive or even die. An infection caused by natural invasion will be uncontrolled and therefore has the possibility of causing severe damage, however vaccination provides a way of controlling the result with minimal harm to the birds.

Vaccines are generally sensitive products, some of which are live but in a state of suspended animation. Others are dead. All have a finite life that is governed by the way they are handled and used. Handling and administration procedures also influence the potency of many vaccines and consequently the level of immunity the bird develops.

Types of vaccines

Live vaccine – the active part of the vaccine is the live organism that causes the disease. As such, it is capable of inducing the disease in birds that have not had previous contact that organism. Vaccinated birds, in many cases are able to infect non-vaccinated birds if housed together.

Attenuated vaccine – with this type of vaccine the organism has been weakened by special procedures during manufacture so that it has lost its ability to cause the serious form of the disease. At worst, the birds may contract a very mild form of the disease, however, the vaccine still has the ability to trigger the immune system to produce antibodies.

Killed vaccine – with this type of vaccine the organism has been killed and is unable to cause the disease, although the ability to trigger the immune system remains. In many cases, the level of immunity produced by this form of vaccine is weaker than that produced by live and attenuated vaccines.

Vaccine production

Vaccines are produced mainly in three forms:

1. Liquid vaccine – it is in fluid form ready to use.

2. Freeze dried vaccine – the vaccine is stored as one pack of freeze dried material and one pack of diluent, often a sterile saline solution. These have to be combined before use.

3. Dust – where the vaccine is prepared for administration in the dry form.

Vaccines are sold in dose lots, the number of doses being the number of fowls that may be vaccinated with that amount of vaccine when using the recommended technique. In the case of many vaccines there are differences in the disease organism strains that they are effective against. It is important that the correct vaccine strain be used and this can only be determined by veterinary advice.

Handling vaccines on the farm

Vaccines are fragile in many respects and require very careful handling to ensure they retain their potency. Poor handling procedures will, in most cases, result in a rapid decline of potency.

The important handling requirements on the farm are:

On receipt of the vaccine on the farm, check and record:

1. That the vaccine has been transported in the recommended manner which is usually in the chilled or frozen state. Prolonged exposure to atmospheric temperature will result in rapid loss of potency.

2. Type of vaccine – is it the vaccine ordered.

3. The number of doses – has the correct amount been delivered.

4. The expiry date of the vaccine – vaccines have a date by when there is a significant risk that they will no longer retain their potency and will not produce the immunity required. The expiry date is based on the vaccine being handled and stored in the recommended manner.

· As soon as possible place the vaccine into recommended storage conditions. Read the instructions to find out what these are. However, freeze dried material should be kept at a temperature below freezing and its diluent at a temperature just above freezing. Liquid vaccines are generally kept at temperatures just above freezing.

· Remove the vaccines from storage immediately prior to their being used. Only remove and re-constitute enough for immediate needs and repeat this through the day if more is required. Do NOT mix what is required for an entire day at the start of the day and leave it stand until required, as the vaccine will rapidly lose it efficacy.

· Protect the vaccines after mixing by holding them in an ice bath. Place ice in a small container and place the container of mixed vaccine in the ice. Some vaccines have a very short life once mixed. For example, Marek’s Disease has a life of about 1.5 hours after mixing IF HELD IN AN ICE BATH. It is much shorter if held in higher temperatures.

· Use the recommended administration techniques and do not vary these without veterinary advice.

· Always clean and sterilise the vaccinating equipment thoroughly after use.

· Always destroy unused mixed vaccines after the task has been completed. Some vaccines have the potential to cause harm if not destroyed properly.

· Do not vaccinate birds that are showing signs of disease or stress.


Vaccination procedures

There are a number of ways that vaccines may be administered to poultry and it is very important that the correct method be used for each vaccine. To use the wrong method will often result in failure of the vaccine to produce the desired immunity. Some of the methods require the operator to handle every bird and, consequently are time consuming and stressful to the birds and operator. Other methods involve administration by methods much less stressful and time consuming. These methods include administration via the drinking water or as an aerosol spray. The different ways that the vaccines may be administered to poultry are below.

In-ovo vaccination

Using the method of in-ovo vaccination, the vaccine is administered into the embryo before hatch.

In general, vaccines can be applied to five different areas of the egg: the air cell, the allantoic sac, the amniotic fluid, the body of embryo and the yolk sac. Vaccine uptake and therefore the immune response of the chicken depend largely on the area of injection. While injection in the air cell has been shown to be minor/not effective, injection in the body of the embryo or the allantoic sac is effective. Therefore, the optimum period to inject the embryo is in the late stage of development, i.e. the time between the ascendance of the stalk of the yolk sac into the abdomen (about the time when the chicken tucks its head under its wings) and external pipping.

During that late stage of development, the embryo is mature enough to cope with the viral stimulus and the trauma induced by the penetrating needle is unlikely to cause severe tissue damage. Signs of too early vaccination include reduced hatch-ability, late death and increased number of culled birds. However, if vaccination is done too late in embryo-nation, the risk of egg shell breakage is significantly higher. Therefore, in ovo vaccination is commonly performed between days 18-19 of incubation.

The system of a larger outer needle (penetrating the egg shell) that contains an inner needle (penetrating the embryo) enables for strong but careful penetration of the egg and minimizes trauma to the embryo. In addition, the use of two needles reduces the likelihood of transferring contaminants on the outer egg shell into the sterile embryo. The needle for punching the egg shell should not penetrate the embryonic cavity (the inner shell membrane, the chorio-allantoic membrane or air cell membrane). While the penetration of the outer egg shell increased the relative pore volume about 30%, the risk for increased gas exchange of the embryo occurs.

Hygiene management including reduced air circulation, well maintained air filters, adjustment to weather conditionsand well maintained hatchery insulation has to be taken into account when performing in ovo inoculation. Only strict management of these environmental factors can reduce the likelihood of infections of the egg, especially with aspergillosis or other air-borne pathogens. Continuous training of reliable staff is of highest priority to prevent reduced hatchability and to maintain high hygienic standards. A sterile environment and the usage of chlorine based sanitizers are crucial. The storage and preparation of the vaccine in a separate biosecure area as well as strict precautions in using sterile devices such as containers and water should be implemented. While the cost of machine acquisition is high, the investment can pay back by its advantages.

The advantage of commencing immunity development before hatch can prevent young chicks from early infection after hatch. Since high tech machines are used for in ovo injection, the volume and concentration of the vaccine to be administered are highly standardised, reducing human error and labour cost when compared to vaccination of chickens later in life. Furthermore, vaccination of every single chicken can be ensured resulting in better uniformity of the flock. Coming with this is improved animal welfare due to less handling of birds later in life.

Currently Marek’s disease, Newcastle disease, infectious laryngotracheitis and infectious bursal disease vaccines are routinely administered using in ovo vaccination in various countries. In ovo vaccination does not interfere with maternal antibodies that may still present in the embryo. In fact, it increases the level of immunity and as a consequence one injection is sufficient to offer life-long protection against the target disease.

Intramuscular injection

This method involves the use of a hypodermic needle or similar equipment to introduce the vaccine into the muscle (usually the breast muscle) of the bird. The task is sped up greatly by the use of an automatic syringe which makes the technique relatively easy and doesn’t harm the bird. Care must be taken to ensure that the correct dose is administered to each chicken and the equipment should be checked regularly to ensure this.

Care must be taken to ensure that the needle does not pass through into a key organ and that other unwanted organisms are not administered to the bird at the same time by contaminated vaccine or equipment. Contamination can be prevented by good hygiene and recommended vaccine handling procedures.

Subcutaneous injection

This method involves the use of similar equipment to that used for the intramuscular technique. The main difference between the two techniques is that, in this case, the vaccine is injected under the skin, usually at the back of the neck, and not into the muscle. Care must be taken to ensure that the vaccine is injected into the bird and not just into the feathers or fluff in the case of very young chickens. The dose being administered should be checked for accuracy frequently. Maintain good hygiene practices to limit introducing contaminating organisms during the procedure.

Ocular

This method involves the vaccine being put into one of the bird’s eyes. From here the vaccine makes its way into the respiratory tract via the lacrimal duct. The vaccine is delivered through an eyedropper and care must be taken to ensure that the dropper delivers the recommended dose. If it is too little, the level of immunity may be inadequate, while if too much, the vaccine may not treat the total flock but will run out beforehand.

Complete Vaccination Program For Gamefowl

Nasal

This method involves introducing the vaccine into the birds’ nostrils either as a dust or as a drop. Always ensure that the applicator delivers the correct dose for the vaccine being used.

Complete Vaccination Program For Gamefowl

Oral

With this method the vaccine dose is given in the mouth. From here it may make its way to the respiratory system or it may continue in the digestive tract before entering the body.

Drinking water

With this method the vaccine is added to the drinking water and, as a consequence, is less time consuming and is significantly less stressful on the birds and operator. Take care to ensure the vaccine is administered correctly as there is much scope for error. The recommended technique observes the following:

· All equipment used for vaccination is carefully cleaned and free of detergents and disinfectants

· Only cold, clean water of drinking quality should be used

· Open the stopper of vaccine bottle under water

· The water present in the drinking trough should be consumed before vaccination

· By ensuring that all birds drink during the vaccination phase, all should receive an adequate dose of the vaccine

Cloacal

This method involves the introduction of the vaccine to the mucus membranes of the cloaca with an abrasive applicator. The applicator is firstly inserted into the vaccine and then into the bird’s cloaca and turned or twisted vigorously to cause an abrasion in the organ. The vaccine enters the body through the abrasion. The technique is time consuming and stressful to the birds and care must be taken to ensure no contamination is introduced with the vaccine particularly from bird to bird. As a rule, the technique is not used on commercial farms.

Feather follicle

With this method the vaccine is introduced into the feather follicles (the holes in the skin from where the feathers grow). The technique involves the removal of a group of adjacent feathers or fluff in young chickens, and the brushing of the vaccine into the empty follicles with a short, stiff bristled brush. Good hygiene is necessary to prevent the introduction of contaminant organisms with the vaccine.

Wing stab

With this method the vaccine is introduced into the wing by a special needle(s). These needles have a groove along their length from just behind the point. When dipped into the vaccine some of the vaccine remains on the needle to fill the groove. The needle(s) are then pushed through the web just behind the leading edge of the wing and just out from its attachment to the body of the bird. Care must be taken to select a site free of muscle and bone to prevent undue injury to the bird. Ensure that the needles penetrate the layers of skin at the ideal site. A common problem is for the vaccine to be brushed from the needles by fluff or feathers before it is brushed into the follicles.

Spray

With this method the vaccine is sprayed onto the chickens (or into the air above the chickens) using a suitable atomiser spray. The vaccine then falls onto the chickens and enters the body of other chickens as they pick at the shiny droplets of vaccine. A small quantity may be inhaled as well.

Monitoring

In the case of some vaccines, an important part of the procedure is to ascertain whether the vaccine has worked, or “taken”. A good example of this is fowl pox vaccine, which is administered by wing stab. Within 7 to 10 days after vaccination a “take” should appear at the vaccination site. This is in the form of a small pimple one half to one centimetre in diameter. If the take is larger and has a cheesy core, it indicates that contaminants have been introduced either with the vaccine or with dirty vaccinating equipment. A check for takes would involve inspecting approximately 100 birds for every 10,000 vaccinated.

Another example of whether the birds are reacting satisfactorily to the vaccination is the systemic reaction found in chickens vaccinated against infectious bronchitis disease. In many cases the birds react approximately 5 to 7 days after vaccination by showing signs if ill health such as slight cough, a higher temperature and lethargy. In cases where there are no obvious signs of success, blood samples may be taken and sent to the laboratory for examination. The usual test is for the presence of an adequate number of the appropriate antibodies (called the titre) in the blood. If the vaccination has been unsuccessful, it may be necessary to re-vaccinate to obtain the desired protection.

Failure to find evidence of success could be because of:

· Faulty technique resulting in the vaccine not being introduced into the vaccination site.

· Faulty vaccine – too old or not stored or mixed correctly. It would be unusual but not impossible for the vaccine to be faulty from manufacture.

· The birds are already immune i.e. the immune system has already been triggered as a result of parental (passive) immunity, previous vaccination or other exposure to the causal organism.


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