On-farm biosecurity for monitored free dairy herds

Now that all dairy herds in Queensland are monitored free (MF) for enzootic bovine leucosis (EBL), dairy farmers should ensure they have on-farm biosecurity measures to keep the disease out of their herds.

If a future bulk milk test shows that your herd is infected, you will be responsible for a testing program to allow you to return to MF status.

How the disease is spread

EBL is primarily spread through milk from infected cows to calves. In addition, about 5% of infected cows pass the infection to their calves during pregnancy. Now that all dairy herds are monitored free, this is not an important method of spread.

The EBL virus can also spread by transfer of blood between animals. This may occur during management procedures such as dehorning, injecting, tattooing, ear tagging or rectal examination. Blood sucking insects may also be involved in transmitting the virus.

Other opportunities for the spread of infected blood include contamination from open wounds, during natural mating or at calving. Artificial insemination does not spread the virus.

On-farm biosecurity

Buy wisely

Before purchasing animals, check the EBL status of the herd of origin. You should only purchase animals from other MF dairy herds, according to the standard definition and rules of the EBL eradication program. If you have to buy animals that are not MF, they must be tested before entering your herd.

Heifer or calf-rearing businesses are not certified under the EBL eradication program. They may have EBL-free and untested animals mixing on their property. Therefore, dairy farmers who use a heifer rearer must reassure themselves that the animals returning to their herd are free from EBL infection. The only reliable method is to blood test them for EBL.

Introduced bulls, unless coming from a MF dairy herd, must be tested before entering the herd.

Avoid contact with beef animals

The national EBL eradication program only includes dairy farms. EBL occurs sporadically in beef animals in Queensland. Dairy farmers need to be careful to avoid contact between their dairy herds and beef cattle on their own properties and neighbouring farms.

Avoid disease spread between animals

To avoid the spread of EBL to your dairy cattle:

  • do not borrow equipment from other dairy or beef farms
  • do not mix beef and dairy animals during management procedures
  • do not share the equipment between dairy and beef animals on the same property
  • quarantine newly introduced animals until they have been tested for EBL
  • disinfect equipment such as dehorners, tattooing and tagging instruments between animals
  • consider using new vaccination needles for each animal
  • discard rectal gloves if they are contaminated with blood.