Many of you may already be aware of some of the large scale Botulism outbreaks we have seen in the practice in the last few years resulting in the loss of over 100 cows in some cases.
Whilst news of the larger outbreaks often travels fast, we also see a number of more isolated cases on farms across the practice with fewer cows affected. However, it is not uncommon for 5 – 10% of cows in a herd to die when the disease strikes.
Botulism is caused by ingestion of the toxin produced by bacteria Clostridum botulinum in feed or water, the bacteria proliferate in rotting carcases and decaying organic material. Commonly outbreaks are associated with the spreading of broiler manure which can contain chicken carcasses. Some more recent outbreaks have been linked to silage fed where it is assumed a carcass must have been included in the clamp.
Silage that has a pH of >4.5 can increase risk as the bacteria can still proliferate under these conditions. Modern day feeding practices mean that often a small amount of feed can be disseminated to hundreds of cows using the mixer wagon.
Isolating the source can be difficult as the carcass may be limited to a small area of the ensiled forage and subsequent testing may be unrewarding. This means it can be almost impossible to define if a forage is safe to feed and therefore there is always a risk to any herd. The presence of chicken farming nearby is certainly a risk factor for botulism being present in forage, this information is often not known when purchasing forage and so this represents an increased risk of disease.
Treatment of botulism cases is generally unrewarding, the disease causes a progressive paralysis resulting in death in as short as a few hours to several days. Cases can continue for around 7-10 days after the contaminated feed or water source has been removed but can continue for up to 3 weeks. Suspected contaminated feed or water source should be removed as soon as possible but as discussed earlier it can be hard to define the safety of a clamp of forage.
With an apparent increase in cases within the practice area and due to the lack of effective treatment and the difficulty in reducing the risk on farm, we are now recommending that herds strongly consider vaccinating against botulism.
We can discuss the specific risks for your farm and then apply for a vaccine import license if appropriate.
Cattle and sheep require a two dose primary course followed by an annual booster to ensure adequate protection. Please contact our Farm Team to discuss further.