WORDS: Trudi Baird

We had a dreadful lambing.

Unfortunately, we were let down by our toxoplasmosis vaccination programme. More than half of our scanned inlamb two-tooths either aborted, reabsorbed fetuses or gave birth to dead lambs.

The dead loss, based on a conservative figure of $105 per lamb, amounts to over $35,000 of lost income. A significant loss on our 200-hectare farm.

We tried to salvage what we could and thanks to amazing pretup pasture growth, our triplet drop was abundant and so we mothered-on triplet lambs to more than 100 two-tooths.

We would have done more but not all of them came on to their milk so at least another 100 were left as wet-dry. A similar number again of twinning two-tooths only gave birth to one healthy lamb.

Initially we didn’t know what the issue was so acted fast to find out what we were dealing with, particularly in case it was contagious.

When the first lab tests didn’t test positive to any of the common issues, we knew by then whatever the problem was the ewes weren’t showing signs of it despite been mixed up with the two-tooths since scanning. This pointed to a vaccination issue, prompting us to expand the lab testing net wider to include toxoplasmosis. This time the lab result was a positive for all samples tested, which our vet expressed surprise at seeing such definitive results.

As we had vaccinated against the disease our vet said the animal health company would be on the ball to find out where the breakdown had occurred. Unfortunately, communication was slow and then suggestions were made that just didn’t sit well with either Phil or I.

I felt we were being talked down to and disregarded, which just made us more determined to push for answers.

In order for an abortion storm like this to occur, about three scenarios can occur. Our situation didn’t make a good fit with any of these, which was puzzling for both us and the animal health company.

MSD was insistent the vaccine batch was not the problem. They were initially insistent we must have a cat problem. We don’t. We have a neighbouring farmer with a dislike for cats so we’ve always assumed this is why we seldom see a stray.

Sure, it only takes one young cat with an infection, which is possibly what has happened, but to over-ride the immune system of a fully vaccinated two-tooth mob takes some doing. To put a fine point on it, this is what a vaccination programme is designed to mitigate for.

We were extensively questioned on dry feed, but we don’t store hay, feed hay or other dry feed that cats might like to live in. The other issue was with the handling of the vaccination, but because I behave like a security guard in charge of couriering money when it comes to handling our vaccines, I feel confident I couldn’t follow the procedures any better than I already do.

The company undertook extensive testing over our whole flock and it showed elevated toxo antibodies is widespread and yet only the two-tooths showed signs of being affected. The company suggested there was more than a toxo issue and seemed intent on taking this line but the tests kept pointing to toxo and nothing else.

Our own inquiries have highlighted to us the vaccine is no longer considered as reliable as it used to be and I was most interested to read in our local newspaper that there have been a number of reports of toxo abortions this past lambing in vaccinated sheep.

So why has the problem occurred?

This is the big question the vaccine manufacturer cannot give us a definitive answer to. In our meeting with the company rep, with our vet present, there was an acknowledgement from her the vaccine hasn’t lived up to or delivered on its marketed promise but this doesn’t change our dead loss.

We inquired about compensation and were asked to submit figures but it has come to a dead end. We were asked at least three times if we were going to get our lawyer involved and initially we did contemplate it but I’m from a legal office background and it really irked me that in order to have the company act further we would have to involve lawyers, who, with respect, know very little about farming, sheep vaccinations and stressful lambings, and who will basically spend the next few months firing letters backwards and forwards.

I imagine things would be different if it were babies we were dealing with and not lambs.

We received a final report from MSD in the new year, which really sheds no light at all on why the problem occurred. In summary, our opinion is their conclusion is weak and continues to ‘pass the buck’ by questioning the validity of lab testing, the possibility of other diseases being the problem (although no others were detected on any of the tests), the immune response of our two-tooths and the continued insistence we probably have a feral cat problem.

I now know more about the disease than I ever wanted to. Apart from the fact the vaccination doesn’t give full protection, I’ve learned that when lab testing for the disease, a negative test doesn’t always mean a negative result.

Initial testing is done on the gut but toxoplasmosis doesn’t always reach the gut but should be present in the brain. So, brain analysis is very helpful – but it needs to be specifically requested of the lab by the vet who probably won’t think to ask for it unless the farmer asks.

Of course, testing comes at a price. My advice is, where reabsorption in maiden sheep is apparent, or there are unexplained abortions, or weak lambs and any initial testing is negative, pay the extra money to have the sheep blood tested for toxo antibody levels and viable aborted samples tested for toxoplasmosis in the brain, even if you have vaccinated.

Understanding what I do now, I think if more farmers do this kind of analysis there may potentially be a significant issue alerted to, that so far is occurring under the radar. What’s more, any ewe lambs that have been infected in the womb but born otherwise healthy (which is potentially more common than we realise) have an apparently small but increased chance of aborting or reabsorbing the fetus in their first lambing.

I think there could be a significant issue here too and wonder if the increased incidence of unexplained wet-dries in maiden stock is a silent toxoplasmosis issue, despite vaccination?

It turns out the disease is a much more complicated beast than I ever realised – or wanted to.

There is a breakdown occurring somewhere and this is where the opportunity lays, so surely worthy of more focus.

MSD Animal Health technical services manager Jo Holter responds:

MSD Animal Health recognises the anguish and difficulty in dealing with an abortion outbreak and takes all reported cases of suspected lack of product efficacy very seriously. As per our pharmacovigilance requirements the details of this case have been reported through to the local regulatory authorities.

As per normal procedure, a full investigation into the vaccine was carried out and MSD Animal Health is confident the batch used was potent and was delivered to the clinic with no potential quality issues.

It is vital to consider the efficacy expectations when using Toxovax.

As with all vaccines, efficacy is based on the immune response of animals to vaccination. In any animal population there may be a small number of individuals which fail to respond fully to vaccination.

Successful vaccination depends upon correct storage and administration of the vaccine together with the animal’s ability to respond.

The level of exposure to challenge, management issues, health status of animal, genetic constitution, intercurrent infection, age, nutritional status, concurrent drug therapy and stress all affects the level of protection from disease.

Immune responses can never be regarded as 100% protective in 100% of animals and in field situations heavy challenge may overwhelm some animals’ vaccinal immunity. This potential for variability in immune response in animals is recognised on the product label.

MSD Animal Health remains fully confident in the field efficacy of Toxovax.