News & Advice

Theileria- the tick disease

Jun 18, 2015 | Biosecurity, Dairy, Dairy Animal Health & Welfare

Theileria is a parasite that lives in the red blood cells of cattle. It destroys the red blood cells (causing anemia) and releases the pieces of the red blood cells into the blood stream (causing jaundice). 
Don’t we already have Theileria in New Zealand? 
Yes, we have had one type of Theileria in New Zealand since at least the 1980s. However, the recent cases are being caused by a new strain (Ikeda) which has likely been in New Zealand since 2011. 
How does Theileria spread? 
It is spread by ticks. Ticks pick up the infection from an infected cow and transmit it to an uninfected cow. Ticks can also ride on deer and potentially hares resulting in spread between farms. 
What if I don’t have ticks on my farm? Will I get Theileria? 
If you live in the Waikato you have ticks on your farm. Every farm in the tick zone will get Theileria. Ticks have three stages in their lifestyle with the immature ticks being very hard to see. 
What are the signs of Theileria infection? 
Signs are caused by anemia and jaundice: slow/lethargic cows with weight loss, decreased milk production, exercise intolerance (stop often when walking), yellow vulva or yellow third eyelid. Ask your vet for the FANI card to help identify sick animals. If undetected and untreated, a small percentage of affected cows will die. FANI CARD web link: 
What are the treatment options for sick animals? 
Reducing stress (once a day milking, minimal walking, ad lib feeding, gentle handling) is the MOST important treatment for affected animals. 
Severely affected animals may need treatment with a blood transfusion and/or drug therapy (e.g. buparvaquone). 
Are there any other drugs I can use to treat Theileria? 
There are no other available treatments for Theileria. Oxytetracyclines have been used in the past, with minimal success. 
Which animals are most susceptible to disease? 
Any animal experiencing stress (calving, peak lactation, any other disease, dry off, newly born beef calves, etc.) 
How many farms already have Theileria? 
At least 500 farms have been diagnosed with Theileria in the North Island. It is likely that many more herds are already infected but have not detected clinical cases. Theileria is expected to spread through the remaining herds in the tick zone over the next 1-2 years. 
How long does Theileria take to spread through the herd? 
There is no data on this right now, but it appears to take about a year. Most sick animals are noticed in the first 2-3 months after the first case is found. 
Should I be using a tickicide on my cows? 
This decision is very farm-specific and should be discussed with your veterinarian. Tickicide is useful in some cases. However, as the majority of ticks on a farm at any given time are actually on pasture, and because tickicides have a limited duration of effect (3 to 6 weeks), it is unlikely that even with frequent tick application, that Theileria can be totally prevented. 
Can I reduce the risk that my farm will get Theileria? 
The first question to ask is whether in fact Theileria is already present on the farm. 
As most cases of Theileria do not show any signs, it is highly possible that the infection is already within a Waikato herd, but not detected. 
Blood testing a sample of cows from a herd may help determine if a herd has infection or not. If infection is already present in the herd, it is likely that many animals are immune and the issue is then just to manage any clinically affected animals that are found. 
For herds that aren’t currently infected, we recommend having a management discussion with your vet about any animals coming on to the farm, including animals returning from run-offs and bulls being introduced for mating. The vendor should be asked about the Theileria status on their farm. The animals potentially could be bled to establish their Theileria status. 
Can other species get Theileria? 
No. Theileria is cattle-specific (dairy and beef). The disease poses no risk to humans or other species. 
What should I do if I have questions about Theileria or I think that I have a cow with Theileria? 
Contact your local Anexa veterinarian.  We can examine your animal and help you make a plan to decrease the impact of Theileria on your herd. 

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