The Ikeda strain was identified in Northland last spring, where it caused calf deaths, and it has now spread over the upper North Island. Cattle can become infected only after cattle tick infestations but movements of infected cattle can spread the disease theileriosis.
An infected beast that moves to a new area can be infested by new ticks, which can then spread the parasite. It cannot be spread cattle-to-cattle, and there are no human health or food safety issues.
The Ministry for Primary Industries said cases of parasite infection are being confirmed quickly this spring, perhaps helped by tick-friendly drought conditions last autumn and a mild winter. In mid-September nearly 130 reports had been received, more than 100 of them confirmed theileriosis. Waikato herds are harbouring up to 30% of cows with the parasite and there have been multiple deaths.
Northland veterinarian Meredith Love, of The Vet Centre, Ruawai, started picking up cases of theileriosis last spring, firstly among beef cattle calves. It was on the west coast of Northland but farmers and vets in other districts were possibly not yet tuned in, or calf deaths were attributed to something else, she said.
On farms where calves were infected, up to 10% of them died
Mature cattle in Northland had not been badly affected, because of prior exposure to benign strains of theileria, which have been present for 30 years.
Cattle movements in tick-prone areas are the problem this spring, both cattle into Northland which haven’t been exposed before, and infected cattle out of Northland to fresh pastures further south.
It was important to take bloods and get the parasite identified, if present, so that more intensive prevention and control measures can be used, Love said. She is recommending two Bayticol pourons, three weeks apart, best applied in spring when the ticks are immature. Most farmers use tick control when the engorged ticks become obvious, in the middle of summer, but theileria could be present by then.
DairyNZ chief scientist Dr Eric Hillerton said cattle are at risk of infection when moved to areas where infected ticks are present.
Likewise, if an infected animal is transported, it can spread infection to ticks in the new location, in turn spreading disease to uninfected animals. The infected ticks themselves do not have to be transported and the blood parasite cannot spread from animal to animal without ticks.
Prevention measures include quarantine periods after cattle movements, chemical control of ticks and easing of underlying disease or stress in cattle from things like trace element deficiency, bovine viral diahorrea and facial eczema.
“There is no vaccine and only limited supplies of drugs for treatment of theileriosis,” he said.
“Exercise intolerance will be likely. Farmers may notice animals lagging behind the rest of the mob when being shifted or lying down in the paddock.
“Affected animals should be rested, given high quality feed and water, and handled only when absolutely necessary.
“Risk of the disease is minimised by good stock management and applying tick control when necessary, especially if moving animals, including calves, off-farm or purchasing new cows.”
Farmers who suspect they have animals with anaemia should contact a veterinarian for advice.
To date, the affected areas include Northland, Waikato, King Country, Bay of Plenty, and parts of the lower North Island.
Keeping the risk at bay
DairyNZ is advising farmers to:
• Check the health of animals before purchase and ask for records of veterinary and other treatments.
• Check a sample of the herd at least weekly for tick infestation and use a tick control product, obtainable from a vet centre, as often as the label says.
• Quarantine new stock from the rest of the herd for at least seven days. Inspect the animals for ticks during this time and treat for ticks as necessary.
• Make sure animals leaving the farm are healthy and not tick infested.
• Check the tick status of the bull supplier’s or grazier’s farm and if they have had cattle with Theileriosis infection.
• Check boundary fences are intact. Mixing with stock of unknown health status is a risk for several diseases.
The signs of anaemia in cattle include straggling on the walk to the dairy, pale rather than healthy pink vulva and lips, and increased respiratory and heart rates.
Farmers might notice animals lagging behind the rest of the mob when being shifted, or lying down in the paddock. Such animals should not be stressed or moved as their reduced capacity to transport oxygen around the body can lead to collapse and death.
They should be rested, given high quality feed and water, and handled only when necessary. There are a number of causes of anaemia and its signs can be similar to those of other diseases.
