New Zealand appears to be lucky in having only one major livestock tick.
DairyNZ veterinarian and technical policy advisor Nita Harding says stock now grazing, such as heifers, that will be coming onto the farm could pose a risk – or be at risk of Theileria – depending on the situation onfarm.
Harding says farmers can help the industry and veterinarians manage and prevent the spread of the disease if they are moving cattle between Theileria zones this season.
“Pregnant cattle are at the highest risk. Other stock classes appear not to be as susceptible,” she says.
“To assess your risk you need to understand your current level of risk where you farm and the risk in the area the cattle are moving from or to. We’ve subdivided the country into three general zones based on our current knowledge of tick distribution and farms on which the disease has been confirmed.
“Essentially we have stable, unstable and free areas – and they equate to high, moderate and low risk areas for Theileria. At particularly high risk are high performing animals from free and unstable areas moving into stable areas. We strongly recommend that farmers shouldn’t bring in pregnant heifers and cows from tick free areas into stable areas without seeking veterinary advice.
“Sharemilkers who are forming their herds or farmers undertaking conversions and forming new herds need to take particular care.”
If you are buying in replacements or are building a herd from multiple sources, it is a lot more complicated to assess the risk of Theileria to your farm, she says.
“Remember there could be multiple diseases that could pose a risk to your farm so it’s important to talk to your veterinarian and do a bit of risk assessment and management planning.”
Franklin Vets managing director Mark Hosking says there is a movement risk tool on the Franklin Vets’ website (www.franklinvets.co.nz) which farmers can quickly use to see what risk they may face.
There is also advice on DairyNZ’s website www.dairynz.co.nz/theileria and the New Zealand Veterinary Association website www.nzva.org.nz
“We’ve dealt with a lot of cases in our area so we have worked to help others across the country to understand the disease,” says Hosking. “For people who are moving stock into areas with ticks, we would strongly advise they carry out blood tests to determine if the animals being moved have been exposed to the parasite. If they have been exposed then there should be relatively little risk of them developing clinical disease. However if they haven’t come across the parasite before then they will be at a high risk of breaking down with clinical Theileriosis.
“If you are moving animals from one property to another, it is paramount that you try to assess the risk you face of running into problems.
“Farmers should avoid exposing naïve animals to infected ticks six-eight weeks prior to calving/peak milk production. Most naïve dairy animals arrive in infected areas in May/June, two months prior to the major stress of calving and milk production.”
What to look out for
The signs of Theileriosis are those associated with anaemia and include:
- pale or yellow, rather than healthy pink, vulva (open up the vulva and look at the colouring inside)
- whites of eyes yellow (a sign of jaundice)
- lethargy – exercise intolerance, cows lagging on the walk to the shed
- sick cows not responding as expected to treatment for conditions such as milk fever
- cows go off their food and appear hollow-sided
- a decrease in milk production
- sudden death especially in late pregnancy or early lactation.