Keith Christensen: Tick-borne diseases a bane for farmers and pet owners

Tick-borne diseases in cattle can lead to their death. Photo / Getty Images

THREE KEY FACTS

• Theileria associated bovine anaemia or theileriosis in cattle is a protozoan parasite that causes anaemia and is transmitted through cattle ticks.
• Ticks are much less common in the South Island.
• Theileria arrived in New Zealand in 2012.

OPINION

Keith Christensen BVSc is a vet at Levin and Horowhenua Veterinary Centre.

As I stood over the carcass of the yearling bull I was performing an autopsy on, the sense of disappointment and sheer bad luck was hanging like a cloud over me and my client.

Raising bull beef is supposed to be reasonably uncomplicated if you get them well past weaning like these ones: they may need an occasional drench, but keep their bellies full of grass and away they go.

However, this bull and a bunch of its mates had moved up from the South Island, and unfortunately been bitten by a tick carrying the theileria protozoa, to which it had no immunity because they don’t have ticks in much of the South Island. As a result, its red blood cells had essentially fallen apart, and without the ability to carry oxygen in the blood, it had died. Five others of its mates were undergoing what amounts to altitude sickness and another had already died.

I’ve been privileged to work in the vet industry in four countries. One thing we can say is that in Aotearoa we are very fortunate to be free of many diseases that are a scourge of animals in other countries, and much of it has to do with the lack of vectors in this country. Vectors, in this sense, are parasites (usually insects or insect-like creatures) that provide a means for a disease to spread between animals.

Control of these vectors and vector-borne diseases is a huge industry overseas and a huge cost to animal production and pet owners. Most other cattle-rearing countries will have three or more parasites that are spread by ticks, causing various syndromes such as abortion and anaemia.

The arrival of theileria in 2012 marked an important change in New Zealand because we have now “joined the gang” of countries with tick-borne cattle illness. Treatment for theileria is mostly about supportive care to let the animal get over it itself. Control of the ticks is problematic due to fact they spend most of their life off the animal on grass, where they can wait until tick treatments on the animal wear off.

So, as I stood in the paddock, I was not full of answers for this client. We knew the cause but the therapy options were limited. Both I and the client were thinking he was very unlucky, but perhaps in the big picture we are the lucky ones, that vector-borne diseases are not a bigger feature of our farming landscape.