Is it Theileria? Recognising the signs of an uncommon infection

Local Land Services District Vets are advising cattle producers to be on the lookout for signs of bovine anaemia caused by the Theileria group.

Theileria are protozoal parasites that are endemic in parts of Australia and are carried and transmitted by ticks. After last year’s wet conditions, District Vets are reporting high numbers of Theileria infection (called theileriosis) in areas where it is not often observed.

District Veterinarian Lyndell Stone said, ‘When ticks feed on cattle the parasite enters the red blood cells and these cells are then destroyed. If large numbers of red cells are destroyed the ability of blood to carry oxygen is reduced and the animal will become ill.’ Lack of red blood cells is called ‘anaemia’.

Clinical signs of bovine anaemia caused by theileriosis include weakness and lethargy, exercise intolerance, difficulty breathing, anaemia and/or jaundice, reduced milk production, and abortion or stillbirths in pregnant cows.

‘As these signs are often symptomatic of many other conditions, it is important to confirm diagnosis via a blood sample taken by a veterinarian’ Lyndell said.

Cattle in endemic areas generally develop immunity to the parasite early in life, although clinical cases may be seen in young calves from around 6 weeks to 6 months of age. In non-endemic regions, or in naïve cattle brought into endemic regions, disease is usually seen 6-12 weeks after exposure to infected ticks. Naïve heavily pregnant cows and heifers are often most severely affected, and the introduction of these classes of cattle should be avoided.

“Unlike animals who have been bred and raised in Theileria-endemic regions, cattle introduced from inland or southern areas are at risk of being naïve to this disease which can lead to illness or death and render bulls temporarily infertile,” Lyndell said.

The Theileria parasite can be introduced into new areas by introducing cattle from endemic areas, typically by moving coastal cattle inland.

Current treatment options for cattle that are affected with Theileria are limited and responses to treatment are often poor, especially in severely affected animals.

Avoid stressing animals that you suspect of being infected with theileriosis to prevent compromising the movement of oxygen in their body any further. This includes avoiding stress and movement and ensure they have cool, fresh water and good quality feed available in immediate proximity to them.

North Coast Local Land Services has an excellent Tips from our Team video about Theileria and how to minimise its impact on your herd. Watch the video on Theileria on our YouTube channel.

A more detailed factsheet on theileriosis can be found at the NSW DPI website.

For further information contact your private veterinarian or your nearest Local Land Services office on 1300 795 299.

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