Biosecurity risks following heavy rainfall – a timely reminder for producers in northern Australia

Jess Rummery, Manager Biosecurity & Extension, Northern Australia

The wet season has well and truly arrived in many parts of northern Australia. Whilst we all love to see the rain, increased rainfall can increase the risks of certain pests, weeds and diseases. This is particularly the case in northern Australia during the wet season, but also applicable at times to many areas in the southern half of the country – for example three-day sickness is known to spread as far down as Victoria in extremely wet years.

The key to disease management is prevention and early detection. The management practices you have can vastly reduce the impact these diseases and weeds can have on your property. For example, feeding and supplementing at the right time can keep your livestock healthy and fighting fit – reducing their susceptibility to disease. Monitoring stock over periods of wet weather can help you identify unusual signs early and get help before it spreads or takes hold.

It is important that you know the risks in your area and monitor stock for any signs of disease following heavy rainfall. In this article I will briefly cover some of these risks.

Bovine Ephemeral Fever or three-day sickness

This cattle disease causes serious economic repercussions through loss of condition, decreased weight gain, deaths and reduced fertility in bulls. Cattle usually have a fever, are stiff from muscle pain and often go down. They sometimes have nasal discharge, drooling saliva and weeping eyes.

The virus is transmitted between cattle by biting insects such as mosquitoes and midges, and these insects become more prevalent after significant rain. The disease can affect cattle of all ages and is often seen after a prolonged dry spell because of the lack of immunity built up in a herd.

To ensure that animals are fully immune before insect populations have the opportunity to breed, it is recommended that vaccinations are completed annually before spring, especially in northern Australia.


Similar to BEF, akabane is a disease spread by biting insects which is why the risk increases in wet tropical weather. The disease can cause abortion, still births and deformities in foetus development.

Australia closely monitors the distribution of these insects via the National Arbovirus Monitoring Program.


The main problem causers in northern Australia are buffalo fly, cattle tick and coccidiosis (black scours). Buffalo fly thrive in humid conditions and in the case of cattle tick, numbers increase about December and persist into the dry season in June.  Naïve cattle from tick free areas are most at risk.

Coccidiosis is a little different in that it doesn’t seem to be directly impacted by weather, but instead increases risk in times of stress (including yarding/weaning) which is why we sometimes see increased cases towards the end of the wet season.

For more information check out MLA’s cattle parasites atlas.


This bacterial disease can infect many species of livestock, including cattle (although it is more common in other livestock species). It can also infect humans. The bacteria lives in the soil and is brought to the surface in times of heavy rain when soil is disturbed. It can cause severe illness in stock and, if infected, often results in death. Signs can include depression, fever, weight loss, respiratory signs, lameness and joint swelling.

The best prevention is to keep livestock away from high risk or contaminated areas and where possible, increase drainage of grazing areas.


Paying attention to weeds is particularly important if you have had heavy rain or flooding which can spread weed seeds and plant reproductive materials. Monitor for germination of foreign plants in areas where flooding has occurred, so you can address the problem early.


If you would like any further information on biosecurity in northern Australia, please feel free to get in touch with me.

Phone: 0499 077 213