Health risks & diseases
Learn more about the risks that face your herd.
BVD (Bovine Viral Diarrhoea)
BVD (Bovine Viral Diarrhoea) is a viral disease of cattle which is wide-spread in New Zealand.
Affecting both dairy and beef herds, it is estimated that about half of herds are “actively-infected” with BVD at any given time and the cost of BVD to the New Zealand cattle industry is around $150 million a year.
BVD can cause pregnancy loss, diarrhoea, milk drop, and reduced growth rates. It also suppresses the immune system, making animals more susceptible to other diseases, such as pneumonia and salmonella.
For more information on this disease watch the following videos.
Salmonella
Salmonella is a bacteria spread by healthy carrier animals via their intestinal tract. Cattle may not show signs of disease, but shed bacteria (usually intermittently at low levels) via their faeces. Abortive material can also be infective, spreading bacteria to other animals. These bacteria go on to infect other animals. Carrier animals can shed Salmonella for months or even years.
There are many different strains of Salmonella in New Zealand, with the most prevalent in cattle being:
- Brandenburg (primarily causes abortions)
- Typhimurium (primarily affects the gut (enteric))
- Bovismorbificans (primarily affects the gut (enteric))
- Salmonella Give (primarily affects the gut (enteric))
Irrespective of the strain, all types of Salmonella can cause death and make people sick (zoonotic disease).
How does Salmonella work?
- Usually spread through ingestion of infected faeces or aborted material
- Normally a large infective dose is required (>107) to cause disease, but many fewer bacteria are needed if the animal has been fasted or their gut is upset
- Survival in the environment: months to years, longest in wet weather. Killed by freezing or pasteurising.
What causes Salmonella outbreaks?
- Carrier animals (which may appear healthy) shed Salmonella from faeces or body fluids into the environment. Most often the carriers are cattle or sheep (not ducks or birds)
- Cattle/sheep pick up the Salmonella which has been shed into the environment
- If the animals are stressed, fasted, or if the environmental contamination is high enough, animals are more susceptible and may become sick
- Sick animals shed very high numbers of Salmonella into the environment, furthering the outbreak
Controlling and minimising Salmonella risk
The most common way Salmonella is introduced to a farm is through healthy looking carrier animals (cattle, sheep etc.).
Higher risk practices include:
- Off-farm grazing
- Intensive feeding
- Purchasing/leasing stock
- Shared boundaries/stock yards
The number of animals that become infected, ill or die depends on the risk factors on farm. Reducing these risks is the first step to helping prevent an outbreak.
Calf Scours
Neonatal diarrhea is arguably one of the most common diseases of newborn calves worldwide. The consequences on animal welfare and those managing the calves can be devastating. The cost of mortality, poor growth and performance as well as treatment costs, all need to be considered. The infectious agents that cause neonatal calf diarrhoea are prevalent in New Zealand. In a recent survey 96% of farms in New Zealand had pathogens that can cause calf scours detected1.
For more information on this disease and calf health in general watch the following videos:
