Stop tick disease spreading

Vet's vision
with Phil Rennie
Tauranga Vets

The ‘tick disease’ theileria has continued to insidiously spread through cattle herds of the North Island including the Bay of Plenty, as well as further down the country.  

Nationwide cases have been reported since September 2012  with the breadth of new farms being infected showing that in  due course virtually every cattle farm – both dairy and beef – will become infected in the short to medium term.

Distribution generally follows the known distribution of the cattle tick Haemophysalis longicornis  but there have been cases on the West Coast of the South Island and other random occurrences outside the tick zone.

Many cows are infected without becoming clinically ill, while others are devastated by the infection and do not survive.

In recent years September has been the peak month for new adult cattle infections, associated with the stress of calving and weather. Of most concern moving into the future are naive young stock that are vulnerable especially during the New Year period when other post-weaning stresses start to figure; and again around April with the late-autumn surge in tick larvae.

Telling signs

The main effect of the blood-borne parasite is to cause anaemia by destruction of red blood cells.

Farmers should look out for lethargy, weakness, depression, inappetance, poor milk production and growth, mortality. Also pale or yellow mucous membranes in the gums, vulva and white of the eyes is a telling sign. Or animals could have increased respiration and heart rates, raised temperature, or bloody urine.

If you suspect any of your animals have anaemia, you should contact your local vet for advice.

A specific treatment is available that improves the chance of survival – but it’s a restricted drug that comes with a very long milk withholding period and an 18-month meat withholding period and has other practical and compliance conditions that limit its use.

 An additional option is to give a blood transfusion, which does give an immediate response in worst-affected cows when done early in the disease course. Some cattle will recover well with supportive treatments, plus vitamin injections and tonics.

Tick control

The most important preventative measure is to control ticks on cattle with a specific topical tickicide, as opposed to a standard pour-on drench. During summer and into autumn is a good time, with the aim of reducing the number of ticks before risk periods. If you already see ticks on your cattle or you have cattle sick with theileria unfortunately the best time to treat ticks was yesterday so to speak.

All the same the impact of disease on your cattle may be mitigated if tick control is done at the next available opportunity. Don’t forget stock movement including bulls – ideally all stock should be treated when entering or leaving the farm.

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