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Improving sheep performance through vaccination

With 88% of NZ sheep farms having endemic Campy and 100% having Toxo, the vaccination of hoggets or maiden 2-tooths with Toxovax® and Campyvax4® is routine for the majority of sheep operations.

The Toxo story is an easy one; one vaccination gives lifetime protection from toxoplasmosis abortion and associated lamb losses. Putting to one side the protection from abortion storms, multiple studies have demonstrated a 3% higher lambing percentage in Toxo vaccinated flocks than those where vaccination is not performed as well as reducing dry ewes by an average of 13.5%.

Toxovax® is a live vaccine, injected into the muscle of the neck using a 2 mL dose, at least four weeks prior to the start of mating.

Campy is more complex. There are multiple strains of Campylobacter and hence the number “4” in the vaccine’s name, Campyvax4®. Campy Is a bacterial disease which spreads when susceptible sheep ingest contaminated feed or water, or when they have direct contact with infected fetuses or fetal membranes.

Commonly we associate campylobacteriosis with abortions in the last six weeks of pregnancy and in naïve flocks abortion levels of up to 30% do occur. However Campy also causes losses at other times which are not as easy to see. In early gestation, infection causes embryonic loss resulting in dry ewes or late lambers and the disease will also cause still-births or the birth of weak lambs that die soon after birth.

In flocks where Campy abortions have occurred historically, vaccination of the flock has resulted in a 9-percentage point lift in tailing.
Campyvax4® is killed vaccine and maiden hoggets/ewes require two subcutaneous vaccinations, four to eight weeks apart, with the second shot ideally given prior to the start of mating.

Traditionally few flocks continue Campy vaccination past the maiden hoggets/ewes and consequently the vaccinal immunity of the flock wanes year by year.

Following an abortion Campy will persist in some ewes. These carriers do provide some level of natural exposure to boost their flock mates, but this is a hit and miss approach to providing protection. It is in flocks using a partial vaccination program, that we see periodic abortion storms and/or higher levels of dry ewes, still births and weak lambs.

The solution is the annual re-vaccination of ewes to provide the full protective performance of this vaccine.

The third disease which can impact the reproductive performance of your flock is Salmonella, and for those who have experienced an outbreak, you know how devastating this is.

For some reason this gastrointestinal disease seems to take out the biggest and best conditioned ewes towards the end of summer, the ones that were set up to perform the best at tupping.

If Salmonella has previously occurred in your flock, this disease should be considered endemic and is waiting for the right conditions to flourish. Any factor that alters rumination may trigger an event and this may be as subtle as a change in feed quality.

The clinical signs are wide ranging; frequently you just find dead ewes often located near water sources. Other cases will have a profuse scour which quickly become dehydrated, and this is why affected animals seek water. Those that linger will be obviously sick and lethargic; they have a high temperature, the diarrhoea has a characteristic khaki green colour, and blood and mucous may be seen in the faeces.

Death rates for enteric salmonellosis range from 1% to 5%.

Vaccination with Salvexin®+B provides effective protection. The initial vaccination requires two shots, with four to eight weeks between the initial sensitising dose and the booster. The dose is 2 mL and the injection is subcutaneous. Thereafter ewes will need an annual booster.

All three vaccines, Toxovax®, Campyvax4® and Salvexin®+B are to be stored at two to eight degrees Celsius; this is fridge temperature, and these products are not to be used if a pack freezes.

Vaccinate sheep that are dry and clean and regularly change the vaccinator needle, every 20 sheep. The vaccination site is the upper third of the neck, closest to the head.

Toxovax® and Campyvax4® may be injected on the same day provided one is placed on the right-hand side and the other on the left.