Vaccination by injection - the dos and don'ts

The arrival on the market of inactivated injectable vaccines in the early 1980s was a significant and welcome development for the poultry industry. It immediately reduced the reliance on the use of live vaccines during lay and also resulted in better safety for both birds and staff performing the vaccination. Here Intervet’s Tibor Cserep discusses how to best to injectable vaccines to ensure optimum efficacy.

Inactivated vaccines work by acting as boosters, after an initial priming with live vaccines. They are designed to induce a high and long lasting immunity against a wide variety of infectious diseases. What makes them even more useful, particularly for broilers or free-range units where disease challenge is high, is the fact that they can confer maternal antibodies to progeny, thus providing chicks with passive immunity against early challenges from IBD, CIA or reo viruses.

Inactivated vaccines are usually given during the rearing period and, assuming the birds have been properly primed with live vaccines, the immunity can last for at least one laying cycle. Inactivated vaccines have to be injected, so mass application techniques like spraying or adding to drinking water cannot be used. Rather than being seen as a hindrance or excuse not to use them, injecting ensures each bird is individually handled and given a uniform dose. This results in generally less variability in the immune response than, for example, with the drinking water administration method.

Time pressures

It is important to be aware that problems with injecting birds can occur if the teams performing the task are under any kind of time pressure. This has the effect of increasing the potential for missing birds, which in itself can cause subsequent problems. For example, if we take Egg Drop Syndrome, against which a layer flock is vaccinated only once in its entire lifetime (for example with Nobilis RT+IBmulti+ND+EDS - Intervet), a ‘miss rate’ of just five percent can have a significant and potentially devastating effect on flock performance following an EDS field challenge. Similarly, pullets will receive live IB, ND and TRT vaccine during the rearing period. If, as a result of administrator error, they do not receive a ‘booster’ dose the ensuing immunity will not be sufficient to cope with a field challenge from any of these viruses. The pressure for speedy vaccination should always be weighed against the potential loss resulting from careless work.

Penning-up and presenting birds

Injecting birds can be a stressful exercise. Penning-up, catching and handling must be done very carefully to avoid smothering injuries and to minimise lameness problems in the early laying period. Stressful penning-up jeopardizes the birds’ welfare and can lead to smothering. To ensure proper flock welfare, farm managers should be present at vaccination or at least when penning-up, and at the start of vaccination. They should then return periodically. Administration of inactivated vaccines needs good teamwork, with catchers helping the vaccinators by presenting the birds gently, safely and in a good position for vaccination.

There are several methods for presenting birds for vaccination. Any method is acceptable as long as the birds’ welfare is not at risk and a full protective dose of vaccine is injected into the correct area the bird. Holding too many birds in one hand is stressful for the birds (and for the catcher) and increases the risk of missing some of them or incorrectly vaccinating.

Injection sites and methods

The most frequently used sites for injection are the back of the neck underneath the skin (subcutaneous or SC), and the breast or leg muscles (intramuscular or IM). The back of the neck is thought to be a quicker site than the breast or leg but requires more care to avoid accidental self-injection. The injection should be made about midway down the neck under the skin and not into bones or neck muscles. Intramuscular injection presents fewer potential problems than the subcutaneous method, although problems can still occur. The breast muscle is preferable to leg muscle for several reasons. Leg muscles are small compared to breast muscles and there are important blood vessels, nerves and tendons above the hock area, which can be easily damaged by a needle, resulting in transient or permanent lameness. If the needle is inserted into this part of the leg it can easily hit the bone, leading to local inflammation and lameness. It is thought that tenosynovitis/lameness problems of the early laying period are at least partly due to rough handling and poor leg injection technique. The size and the thickness of breast muscles offer a relatively safe area for IM vaccination. When injecting into breast muscle, the needle should be placed so as to deposit the vaccine in the thickest part of the muscle. If the needle is inserted too close to the end of the keel or too far to the side it may penetrate the abdominal wall and the vaccine will be deposited in the abdominal cavity. This can result in mortality, in the case of a liver puncture, or peritonitis. Conversely, if the needle is inserted into the breast muscles too near the collar bone or the crop then relatively big blood vessels can be damaged resulting in haemorrhages.

Do it gently!

Injecting inactivated vaccines into poultry or other birds does not require strength. A common problem is to use excessive force when inserting the needle into the leg or breast of a bird. This can be dangerous in the case of leg vaccination as the needle can easily hit the bone causing pain for the bird and damage the bone and the periosteum (tissue surrounding and nurturing the bones.)

In this context, it is perhaps not surprising that many layers vaccinated into the leg sit and show general malaise after vaccination. Excessive pressure on the ribcage by pushing the gun too hard into the breast muscles should also be avoided as the needle can reach the heart or the liver causing fatal injuries.

Inactivated vaccines definitely have a significant role to play in the health management of today’s poultry flocks. They are extremely useful tools for use in the fight against infectious diseases. However, it is important to realise that their effect does not spread from bird to bird like it can do with live vaccines. A missed bird is missed forever! If 20% of a breeder flock is missed then 20% of the potential hatching eggs are also missed.