Ticks on the block: cattle ticks, Theileria and when to treat

🪲 The short version

Spring is when tick treatment starts to matter.

Over the last week or two, the beef and deer farmers have been coming into the store where I work asking for tick treatment. That is the season turning: in the warmer half of the country, tick numbers climb from late winter, and the risk period commonly runs from mid-August to mid-March.

On a lifestyle block, ticks mean three things. They take blood, which matters most for calves, lambs, kids and fawns. They carry Theileria, a blood parasite that can make cattle badly anaemic, especially cows around calving and young beef calves. And most of them aren't on your animals at all — they are sitting in the base of the grass, waiting.

You can't get rid of ticks. The aim is to keep numbers down, treat at the right times, and know what to look for. This guide covers all three.

🔎 Know your tick

Which tick is it?

In New Zealand there is really only one tick that matters on the farm: the New Zealand cattle tick (Haemaphysalis longicornis). Despite the name, it isn't fussy. It feeds on cattle, sheep, goats and deer, and has been found on horses, dogs, hares and birds.

• Where: mostly the North Island — Northland, Auckland, much of the Waikato, Bay of Plenty, Gisborne and Taranaki — and the top of the South Island around Marlborough, Nelson and Tākaka. It likes warm, humid conditions and is most active between about 10 and 20°C with humidity over 60%.
• No males needed. New Zealand's cattle tick is all female. Each one can lay eggs without mating — up to about 2,000 of them — which is why numbers can build so quickly.
• Size: a larva is about 1 mm, like a speck of pepper. A fully fed adult swells to about 6 mm, like a small grey-brown bean.

📅 The calendar

The tick's year, and why spring matters.

A tick has three feeding stages — larva, nymph and adult. At each stage it climbs onto an animal, feeds for a few days, drops off into the grass, and moults into the next stage. DairyNZ sets out when each one is most active:

So right now, in late September, it is the nymphs that are out: larvae that hatched last autumn, got through the winter in the grass and are now looking for their next feed. They become the adults of November and December, which lay the eggs that become next autumn's larvae.

That is why vets usually talk about tick control in spring and again in autumn. Knocking back the spring nymphs means fewer adults laying eggs in summer. In warm, mild places like Northland there can be more than one generation a year, and ticks stay active through much of winter too — as long as the average air temperature is above about 7°C.

🩸 Why it matters

What ticks do to your animals.

A few ticks on a grown animal do very little. A heavy load is a different matter.

• Blood loss. Enough ticks cause anaemia, poorer growth and lost production. It hits young animals hardest — calves, lambs, kids and deer fawns — and heavy burdens have killed young lambs.
• Irritation. Animals carrying a lot of ticks rub and are unsettled.
• Hide and skin damage, which matters to deer and beef farmers selling skins and hides.
• Theileria in cattle, which is the big one, and gets its own section below.

Horses, dogs and people get bitten too. For them the New Zealand cattle tick is mostly a nuisance, but check your dog after it has been running in long grass and remove any ticks you find.

🐄 Cattle owners, read this

Theileria: the reason cattle owners worry.

Theileria (Theileria orientalis Ikeda type) is a tiny parasite that lives in the red blood cells. It was first formally recognised as a problem in New Zealand in Northland in August 2012, and has since spread through much of the upper North Island and into parts of the South Island.

• It only affects cattle. Sheep, deer, horses and dogs carry the ticks but don't get sick from Theileria.
• It needs ticks to spread. It doesn't pass from animal to animal by contact.
• Once infected, always a carrier. MPI's vet handbook notes infected cattle stay infective to ticks for life. Most infected cattle never show signs at all.
• There is no vaccine.

Who gets sick: DairyNZ says it is usually seen in cows around calving and in beef calves 5–10 weeks old. Beef + Lamb NZ adds animals under stress — calving, weaning — and cattle that have recently been moved, especially from areas with few ticks into areas with many.

What to look for:

• An animal that is tired, slow and lagging behind the others
• Breathing hard or gasping after only a little effort
• Pale or yellow gums, vulva or udder, and yellow whites of the eyes (jaundice), instead of healthy pink
• Off its feed, losing condition, or a drop in milk
• Sudden death

✋ Hands on

How to check your animals.

Ticks go for thin skin and places an animal can't easily reach. On cattle, DairyNZ suggests looking:

• around and under the tail
• on the udder or scrotum
• inside the back legs
• on the brisket (the chest between the front legs)
• in and around the ears

On sheep and goats, check the same places plus the face and the bare skin around the legs. On a dog, run your hands over the head, ears, neck and between the toes.

Nymphs are small, so look closely rather than glancing. A good time to check is when the animals are already in for something else — tagging, weighing, drenching. If you are finding ticks on your animals now, there are far more in the grass.

🧴 Before you buy

Treating: what to know before you buy.

Tick treatments for livestock are mostly pour-ons and sprays. Rather than recommend a product, here is what to check at the counter and on the label:

• Is it registered for this species? A product registered for cattle isn't automatically safe or approved for sheep, goats, deer or horses. Some can be used on other species only under a vet's direction. If the label doesn't list your animal, ask your vet first.
• Does it cover all three stages? Larvae, nymphs and adults — you want all three.
• How long does it last? Products differ in how many weeks of protection they give. That tells you when to do it again.
• What's the withholding period? For meat and for milk. Some tick products have none; others do. If you milk a house cow or goats, or you're sending anything to the works, this is the line to read first.
• Dose by weight. Guessing low wastes the product and may not work. Weigh, or use a weigh tape.

For dogs, use a tick product made for dogs, from your vet or pet shop. Never use a livestock product or a dog product on a cat unless the label says it is safe for cats — some are toxic to them.

If Theileria is a concern, the timing matters as much as the product. Your vet can help you plan treatments around calving, weaning and bringing new stock in.

🌾 On the ground

Most ticks aren't on the animal.

This is the part that surprises people. A tick spends only a few days of each stage on an animal, and the rest of its life at the base of the grass. An unfed tick can survive there for up to 12 months. So treating the animals only deals with the ticks that happen to be on them that week.

A few things help keep numbers down on the ground:

• Know your tick paddocks. Ticks like long, rough, shaded grass — along bush edges, scrubby gullies, hedgerows and rank corners. If you find ticks on animals from one paddock more than others, write it down.
• Keep young stock off the worst of it in spring and autumn if you have the choice. Calves and lambs on short, open pasture pick up fewer ticks than those in rough country.
• Graze rough areas down where you can, or top them. Ticks need humidity, and the base of short grass is drier than the base of long, rank grass.
• Hares, deer and birds carry ticks too, so a paddock can be re-seeded with ticks even if your own stock are clean.

None of this gets rid of ticks, and it isn't meant to. It lowers the number waiting for your animals, so treatments go further.

🚚 Stock movements

Buying and moving cattle.

Moving cattle is the biggest single Theileria risk on a small block, in both directions.

• Cattle from a low-tick area coming into a tick area are the most at risk. They haven't met Theileria before, and they arrive stressed from the move. Ask where they came from.
• Cattle from a tick area going somewhere with few ticks can take ticks and Theileria with them. Treat before they go.
• Beef + Lamb NZ recommends holding new cattle separately for 7–14 days and treating them with an effective tick product before they join the rest.
• A bull coming in for mating is new stock too — ask for him to be treated for ticks before he arrives.

Our guide to buying and quarantining new stock covers the rest of what to do before new animals meet your own.

📲 Keeping track

Keeping track of it.

Tick control is easy to lose track of, because it happens twice a year and the details slip in between. It helps to write down:

• What you used, on which animals, and when — so you know when the protection runs out.
• The withholding period, and the date it ends, for meat and milk.
• Where you found ticks — which paddock, which animals — so next spring you know where to look first.
• Any animal that went pale or lagged behind, and when, so your vet has a history to work from.

That is what My Block Hand does. Record a tick treatment against one animal or a whole herd at once, with the product and its withholding period, and the app shows the withholding on each animal until it ends. Add a job for the next treatment and it reminds you when it's due.

🚧 Where this guide stops

What this guide cannot do for you.

This is general information for lifestyle-block owners. It is not veterinary advice, and it doesn't recommend any product. Always read the label, use products only on the species they are registered for unless your vet directs otherwise, and follow the withholding periods for meat and milk.

If you think an animal has Theileria, or cattle are pale, weak or dying, call your vet.

📚 Further reading

Where the information on this page comes from.

• DairyNZ — Theileria and anaemia in cattle, Fact Sheet #5: Ticks and Theileria (PDF): when each tick stage is active, how long each feeds, where ticks live, where to check cattle, and tick sizes.
• DairyNZ — Theileria: signs of Theileria, the mid-August to mid-March risk period, spring and autumn tick control, and the drug treatment's withholding conditions.
• DairyNZ — Short guide to Theileria (PDF): cows around calving and beef calves 5–10 weeks old as the animals most often affected; treating bulls before they arrive.
• Beef + Lamb New Zealand — Fact sheet 76: Anaemia (theileriosis) in cattle (PDF): signs, animals most at risk, minimising stress and movement, blood transfusion, no vaccine, and holding new cattle for 7–14 days with tick treatment.
• MPI and NZVA — Theileria Veterinary Handbook 2 (2015): first recognition in Northland in August 2012, the tick's wide host range, and infected cattle remaining infective for life.
• XLVets — Theileria fact sheet (2019): ticks active whenever mean air temperature is above 7°C, and the risk to cattle moved from low-tick areas.
• Rural News — Hardy ticks well-equipped to survive, thrive: all-female New Zealand ticks, regions affected, 10–20°C and humidity, egg-laying from late November, and unfed ticks surviving up to 12 months.
• VetMed — Tick lifecycle, infestation and treatment options: up to 2,000 eggs per female, more than one generation a year in mild regions, and blood loss in fawns and calves.
• Anexa Vets — Ticks, ticks and more ticks: species affected, including sheep, goats, deer and horses, deaths in young lambs, and taking care with withholding periods.