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:
Leptospirosis (Lepto)
Leptospirosis (Lepto) is an infectious disease transmitted from animals to humans (a zoonosis), and from animal to animal, through cuts or cracks in the skin or through the mucous membranes of the eyes, nose or mouth. Infection can occur in almost all warm-blooded mammals, including farm (sheep, cattle , deer and pigs), domestic (dogs) and feral animals (e.g. rats and mice).
Signs of Lepto include:
In humans: Symptoms can range from minor flu-like symptoms to serious illness needing hospital admission, such as meningitis and kidney or lung failure. In some cases it may be fatal. Always seek medical attention immediately (within 24 hours) if there has been suspected exposure or if flu like symptoms develop. Ensure to tell the doctor that leptospirosis may be the cause of your symptoms as not all doctors may be familiar with the symptoms.
In animals: The infection is often subclinical, meaning the infected animal does not appear unwell. The infection can also cause visible illness in animals, especially young animals.
Common clinical signs associated with Leptospirosis in cows
- Mastitis
- A drop in milk production
- Reproductive losses
Common clinical signs associated with Leptospirosis in calves
- Depression
- High fever
- Jaundice (yellow mucous membranes)
- Blood in the urine