4 Vaccination Schedules

Vaccination schedules need to be thought about individually for each flock according to the flock disease history and the likelihood of a particular disease being introduced, and should be an essential part of any flock health programme. In organically run flocks, vaccination is usually only carried out if a particular disease is known to occur on the farm. It would obviously be expensive to use all the vaccines listed below so a decision is usually made by weighing up the risk and cost of possible losses against the cost of the vaccine. All flocks are potentially at risk from clostridial diseases, and because these are usually fatal, vaccination should be a priority.

At the time of writing there are vaccines available to protect against the following diseases (all, except the orf vaccine, are administered by injection):

• clostridial
• pasteurellosis
• combined clostridial and pasteurellosis
• bluetongue
• enzootic abortion
• toxoplasmosis
• footrot
• erysipelas
• louping ill
• orf.

Storing and Handling Vaccines

The sheep vaccines available today are excellent, although no vaccine can be guaranteed to be absolutely 100 per cent effective. The development and improvement of vaccines is going on all the time – the speed with which bluetongue vaccines were produced is an example of this.

Note that it is a waste of time and money to buy a pack of vaccine, then to store or administer it incorrectly; most vaccine failures are the result of this type of mistake. Generally, vaccines should be stored in a refrigerator between +2 and +8°C, protected from freezing and from exposure to light. Live vaccines (the abortion vaccines) should be made up immediately before use and not left standing about on a warm day as they will deteriorate rapidly. Vaccines with an oily base (footrot and louping ill) may need to be slightly warmed before use to make them easier to inject (for example, by putting in a pocket for a short time).

Vaccines should be handled carefully, particularly live vaccines and those suspended in oil, as these can be dangerous if accidentally self-injected, with serious con sequences – for example, the loss of a finger; an urgent visit to hospital is necessary should the worst happen. Take the package insert along so the doctor has the necessary information. At the end of the day, discard partially used packs as they can be accidentally contaminated; if they are used later and are contaminated they can cause abscesses or even make the sheep ill.

Most injectable vaccines are given under the skin (subcutaneously), although the abortion vaccines either can, or must (depending on the manufacturer), be given into the muscle (intramuscularly). Always read the instructions before starting – sometimes they change! Sheep should be dry and clean – injecting wet or dirty sheep will increase the risk of infections or abscesses developing. Most vaccines produce minor lumps, which usually disappear within a few weeks, but vaccines with oil in them can produce larger and longer-lasting lumps, and even occasionally an abscess.

One other occasional consequence with these is that a patch of black wool grows in a white fleece at the vaccination site. Probably this would not be of concern in a commercial flock, but pedigree breeders need to be aware of this possibility.

Most people use an automatic syringe, but an ordinary syringe can be used for small numbers, making sure that it is sterile. If an automatic syringe is used, make sure it is well maintained, clean and accurate. Although it is usually impractical to change needles between each animal, it is possible that diseases may be spread, or that needles become contaminated accidentally, causing abscesses at the injection sites. So to avoid these sorts of problem needles should be changed frequently, or a system of disinfecting the needle between animals (the ‘Sterimatic’ system) should be used. This also protects the needle when it is not in use, and so helps guard against you accidentally sticking it in yourself.

Discarded needles should be disposed of safely by putting into a sharps container. Your vet will provide one if necessary.

Fig. 160 This automatic syringe has a protective cap over the needle that disinfects it each time it injects.

Fig. 161 A 50ml pack of combined clostridial and pasteurellosis vaccine, suitable for a small flock. Large packs are available for bigger flocks, but any vaccine remaining at the end of the day on which it is used should be discarded as it may have become contaminated.

Vaccination Against Clostridial Diseases

Many sheep keepers have never experienced, or have forgotten, the devastating losses that can result from these diseases, and therefore may not vaccinate either on the grounds of cost or because they have not seen the diseases in their flock. Yet the bacteria that cause these diseases are widespread and can lie dormant in the soil for many years, and the diseases they cause mostly kill without warning. In spite of readily available cheap and effective vaccines, every year laboratories report significant losses from this group of diseases. The most well known clostridial diseases are:

• lamb dysentery
• pulpy kidney
• enterotoxaemia
• abomasitis
• struck
• braxy
• bacilliary haemoglobinuria
• blackleg
• black disease
• tetanus
• botulism (no vaccine).

There are vaccines available prepared to cover four, seven, eight or ten of the clostridial organisms, the so-called all-in-one vaccines. The four-in-one is usually used in growing lambs, which are particularly susceptible to the specific diseases it covers, whilst the others are used for breeding animals, both rams and ewes, and via the colostrum, to protect newborn lambs. Although protecting young lambs is one of the big benefits of vaccination, you should remember that the vaccines also provide important protection to the ewes that receive them.

When a clostridial disease does occur it is usually found that this is the result of one or more of the following possibilities:

• Not completing the primary course of two injections. For example, with breeding ewes bought in early autumn, it is common practice to give a single injection after purchase and to leave the second injection until pre-lambing. This leaves animals insufficiently protected over the winter months.
• It is common to assume that bought-in animals have been fully vaccinated when they have not. Always check for full details if the seller says they are vaccinated.
• The rams are often forgotten.
• Forgetting to give ewes the pre-lambing booster. If this is discovered at the beginning of lambing it is probably still worth vaccinating, bearing in mind the increased risk of handling heavily pregnant ewes. Lambs from unvaccinated ewes should receive a first dose of vaccine as soon as possible, with a second dose four weeks later.

Fig. 162 All types of flock, whether hill or lowland, should be fully vaccinated against clostridial disease. This requires two injections 4–6 weeks apart.

Fig. 163 Previously vaccinated breeding ewes should be given a booster dose 4–6 weeks before lambing is due.

Vaccination Against Pasteurellosis

Pasteurellosis is the term used to cover diseases caused by bacteria formerly called Pasteurella but now renamed Mannheimia and Bibersteinia. There are a large number of species and strains of these bacteria so the vaccine cannot cover all of them, but it does cover some of the commonest and most important, and was significantly improved a few years ago as a result of research carried out at the world-leading Moredun Institute in Edinburgh. This vaccine is commonly combined with the clostridial vaccine but can be used alone if necessary.

Fig. 164 Replacement ewes or ewe lambs should receive a full course of two injections 4–6 weeks apart as soon as possible after they have been brought in, unless they are known to be already fully vaccinated.

Fig. 165 New lambs are born with no protection against disease so rely on antibodies in their mother’s colostrum. They should have a good feed as soon as possible after birth.

Fig. 166 The vaccination of growing and fattening lambs is often neglected. Remember that the protection they gain from their vaccinated mother’s colostrum only covers them for clostridial diseases for about 12 weeks, so they should themselves receive a full course of vaccine (two doses 4–6 weeks apart) starting at about 8 weeks of age. Many lambs reach slaughter age unprotected, but the loss of only a few (usually the best ones!) from diseases such as pulpy kidney can be prevented through vaccination for very little cost.

Fig. 167 Rams should be fully vaccinated and receive a booster each year at the same time as the ewes.

Fig. 168 Previously vaccinated in-lamb ewes are usually given the booster dose of combined clostridial and pasteurellosis vaccine 4–6 weeks before lambing is due. Where pneumonia is a problem, attention should be paid to ventilation. This lambing shed is well ventilated.

Fig. 169 The ventilation is poor in this shed and could lead to problems with pneumonia in ewes and lambs.

Fig. 170 Antibodies in the colostrum of ewes vaccinated with pasteurellosis vaccine protect young lambs for only 2–5 weeks. This protection is much shorter than for the clostridial vaccines. If pneumonia is a problem in lambs they should themselves be vaccinated. This can be started at 3 weeks of age or even earlier if your vet advises it.

The diseases covered include pneumonia in housed sheep, pneumonia and septicaemia in very young lambs, and systemic pasteurellosis (commonly seen as sudden death) in store and fattening lambs in autumn.

As with clostridial vaccines, the primary course consists of two doses of vaccine given four to six weeks apart, followed by an annual booster before lambing or before particular risk periods. The combined clostridial and pasteurellosis vaccines are used in exactly the same way.

Fig. 171 Store or fattening lambs are particularly susceptible to systemic pasteurellosis in autumn. This often follows sales or other movement, especially if put on lush grass, or bad weather. Sudden death is often the first sign. Vaccination (two doses 4–6 weeks apart) should be started before the stress of movement if possible. For newly purchased lambs start vaccination as soon as possible, minimise stress and keep on short pasture to begin with. Your vet might advise injection of a long-acting antibiotic in addition to vaccination.

The main problems that can occur with vaccination against pasteurellosis are as follows:

• Expecting a vaccine to protect in circumstances where sheep are housed in poorly ventilated buildings. No vaccine can be expected to be 100 per cent effective in these conditions.
• Vaccinating ewes too close to lambing – handling at this late stage may provoke metabolic disease such as hypocalcaemia.
• Forgetting that colostral antibodies only protect young lambs for a short time.
• Not fully vaccinating store or fattening lambs in autumn, and not minimizing stress until vaccination is completed.

Vaccination Against Bluetongue

This exotic viral disease was diagnosed in the UK in East Anglia for the first time in August 2007. It spread here from the continent, with the midges that transmit it being blown across by the wind. Thanks to the extremely rapid development of effective vaccines and a campaign to promote vaccination of cattle and sheep, there were no new cases (other than in imported infected animals) in 2008 or 2009, and it is unclear whether it will occur again; however, the risk from infected animals across the English Channel is always likely to be present. An added complication is that new strains of the disease are moving north in France and could pose an added threat, since vaccines will need to be developed to cover more than the one strain currently available.

The advice given here may well become outdated, but it would seem sensible to carry on vaccinating as a precaution for the foreseeable future. Currently there are three different vaccines which require either a single annual injection, given under the skin, or a primary course of two injections three weeks apart, then annual booster injections are recommended before the midges that spread the disease become active in late spring. Lambs get some protection via the ewes’ colostrum, but can be vaccinated from four weeks of age.

Vaccination Against Abortion

The two most common causes of abortion in UK are enzootic abortion and toxoplasmosis, both of which can be largely prevented by vaccination. Vaccines for both diseases can be given simultaneously, but must never be mixed and are given with different syringes at different sites. Both vaccines have withdrawal periods, although it would obviously be a complete waste of money to vaccinate, only to slaughter soon afterwards. (See Chapter 9 for details of these diseases.)

Fig. 172 Sheep infected with bluetongue virus are ill, get swollen heads with haemorrhages in the mouth, and often die.

Fig. 173 Aborted lambs, such as that on the right, can result in large financial losses. Such cases should be investigated to see if the cause can be determined so that vaccination can be planned, if appropriate.

Enzootic Abortion, EAE (Chlamydophila abortus)

As the name suggests, the main sign that this disease is present in a flock is abortions in the run-up to lambing, although weakly lambs can also be seen. Vaccination is the key method of control. Both the vaccines available consist of live, attenuated (weakened) organisms and must be given well before tupping. There used to be a dead vaccine that could be given to pregnant ewes, but this is no longer available. The most common strategy is to vaccinate young replacement ewes at least four weeks before tupping. This single vaccination gives protection for several years, and booster injections are not commonly needed. The vaccine needs to be handled carefully, so read the instructions before starting! Pregnant women should not handle this vaccine.

Injection is either under the skin or into the muscle, depending on the particular product used. Already pregnant ewes should not be vaccinated, and the administration of antibiotics around the time of vaccination should be avoided, as these can damage the vaccine.

Toxoplasmosis (Toxoplasma gondii)

This disease can cause great losses through barrenness, abortion and the birth of weak lambs. Vaccination is very effective. The vaccine contains live organisms that stimulate immunity but do not themselves cause disease. Where a flock problem exists, older sheep are more likely to have met infection and to have developed immunity, so the most usual procedure is to vaccinate young replacement ewes each year well before they go to the ram. The vaccine is not usually repeated. Like the vaccine for EAE, it needs the same careful handling. Injection is into the muscle of the neck.

Vaccination Against Footrot

Lameness due to footrot is a huge problem worldwide (see Chapter 14 for details of the disease). Vaccination is one method of control that can be very effective in helping to reduce the number of animals affected in a flock by both helping to cure existing cases and protecting uninfected animals. Immunity to the natural disease is poor, so the vaccine has to be made more effective by preparing it in an oily material called an ‘adjuvant’.

The disadvantage is that this can cause noticeable lumps at the injection site. Special care needs to be taken to ensure the vaccination technique is as clean as possible, and care must be taken in handling the vaccine, as already highlighted. Use of the vaccine in lambs for slaughter should be carefully considered because of the possibility of injection-site reactions impacting on carcase quality.

A single injection is given under the skin at any time, best of all just before a particular risk period (warm, wet weather or housing); avoid injecting ewes for a month either side of lambing. If necessary, a booster injection can be given three months later, but once the disease is under control a single annual injection may suffice.

Footrot vaccine should not be given to sheep that have previously received injectable moxidectin, and conversely injectable moxidectin (not the long-acting preparation, which is not a danger) should not be given to sheep vaccinated with footrot vaccine as adverse reactions have been reported.

Fig. 174 Vaccination can help reduce the number of sheep suffering from footrot, but make sure the diagnosis is correct before spending money on buying vaccine.

Vaccination Against Louping Ill

Louping ill is caused by a virus transmitted by bites from ticks that feed on sheep; it is therefore only a problem for sheep grazing rough, tick-infested pasture. Like the footrot vaccine, this also contains oil so is dangerous if accidentally self-injected. Ewes are usually vaccinated in their first autumn or during their first pregnancy. Rams and older replacement ewes should be vaccinated at least a month before grazing on tick-infested pasture. Pregnant ewes that are unvaccinated, or have not been previously exposed to ticks, should not be put on infested pasture as they may abort as a result of other diseases carried by these parasites.

Vaccination Against Erysipelas

This vaccination is only carried out where disease caused by these particular bacteria has been diagnosed as a significant problem on the farm. There are two distinct diseases involved:

Fig. 175 Lambs from ewes vaccinated against louping ill are protected by antibodies in the colostrum in their first summer. They can be vaccinated in autumn.

Fig. 176 This lamb has several chronically swollen joints. The most likely cause is infection with erysipelas soon after birth.

In both cases vaccination is effective at future prevention. For protecting lambs, the pregnant ewes should be vaccinated with a schedule as for clostridial diseases (an initial course of two injections four to six weeks apart, then an annual booster before lambing). Protection is via the colostrum. In the case of problems following dipping, the vaccine can be used if necessary, but dipping and handling procedures should be improved so the disease is no longer a risk.

Vaccination Against Orf

The orf vaccine contains live virus so should be handled and used carefully as it can infect people. Unlike all the other vaccines described, this is applied by scratching the skin with a special applicator containing the vaccine. It should never be used in flocks that have not had problems with the disease, as this would result in the introduction of live virus into the environment. In flocks where the disease is a problem it is generally used a few weeks before an outbreak is expected, or when animals are to be sold, a few weeks before the sale time.

After vaccination, scabs form on the skin where the vaccine was applied. These take several weeks to fall off and contain live virus so can contaminate housing. For this reason recently vaccinated ewes should not be kept in the shed where they will lamb. The usual site for vaccination is on the skin inside the thigh, but if it has to be done in ewes just after lambing it should be done inside the front leg where the scabs will be protected from lambs looking for the teats. Occasionally the vaccine is used in very young lambs, when again, the inside of the front leg should be used to try to prevent lambs spreading infection to the ewes’ teats.

Vaccination against Johne’s Disease and Caseous Lymphadenitis

Although vaccines to protect against these diseases are available overseas, they are not generally available in the UK. In the case of severe flock problems your vet may be able to obtain special permission to import some.

Fig. 177 This lamb has severe orf infection and it is very likely to spread it to its mother’s teats. If it is decided to vaccinate ewes this should be done at least seven weeks before lambing. In the case of a severe outbreak around lambing time, ewes should be vaccinated inside the front leg to prevent lambs becoming infected from the vaccination site.