In general, older cattle are more likely to be severely affected than young ones. Calves up to several months old may not show any signs at all. The parasites enter red cells where they multiply, destroying many of the cells. The resultant anaemia decreases the blood’s ability to carry oxygen around the body, resulting in fever and weakness. In tick fever due to B. bovis the destruction of the red blood cells provokes a strong immune reaction and the release of inflammatory chemicals which damage the circulatory system particularly in the brain and lungs.

Babesiosis

The first signs of illness usually occur 8-10 days after tick attachment for B. bovis and 14-20 days for B bigemina. The severity of the illness can range from a mild fever to one which is rapidly fatal. Clinical illness is rarely seen in animals less than 9 months of age.

Typical symptoms of babesiosis are as follows:

• Sudden onset of high fever up to 44°C(106°F) — often the first sign of this is that the animal isolates itself from the others and becomes uneasy and seeks shade.
• At first the membranes around the eye are bright red but over a few days turn pale, or even white, as anaemia develops.
• The animal’s appetite is depressed and there is a rapid loss in condition. In dairy cows, a drop in milk production occurs at the same time as the fever develops.
• Nervous signs are a feature of infection with B. bovis. Circling and personality changes such as aggression are often seen.
• The urine is often red or brown to almost black, hence tick fever is sometimes referred to as ‘redwater’.
• Pregnant cows may abort.
• Infected bulls may be temporarily infertile for 6-8 weeks.

An animal may die at any time from about 3 days to 4 weeks after the onset of the illness. The fever usually lasts for about a week and the course of the disease is about 3 weeks.

In animals that survive, the appetite gradually returns to normal but recovery is slow and may take weeks or even months. Treatment with specific drugs usually results in rapid recovery if given early in the course of disease; however, animals showing clinical signs and left untreated frequently die.

Anaplasmosis

The incubation period for anaplasmosis is longer than babesiosis usually taking around three–six weeks after infection for symptoms to appear. These symptoms are:

• Mild fever, and anaemia, but no ‘redwater’
• Jaundice (yellow colouring of the membrane around the eyes)
• Abortions.

Affected cattle can die acutely or more commonly become emaciated and take months to recover. As with babesiosis clinical signs are rare in animals under nine months of age.

If you suspect tick fever you must notify either Local Land Services (1300 795 299) or the Department of Primary Industries and Regional Development (animal.biosecurity@dpird.nsw.gov.au) within one working day.

When tick fever is diagnosed the herd is subject to regulation to enable eradication of tick fever and the vector cattle tick. If unrestricted by regulation, cattle ticks would be endemic in much of NSW.

Notifiable disease testing is conducted by NSW DPIRD as a cost-free service to the submitter/owner.

In NSW a diagnosis of tick fever is supported by history, clinical signs and smear examination and confirmed via PCR (NSW DPI Laboratory qPCR includes Babesia bovis, Babesia bigemina or Anaplasma marginale).

Submissions for tick fever diagnosis (per animal) should include:

• A thin (conventional) blood smear,
• A thick blood smear, and
• Minimum of 10mL whole blood (EDTA).

For veterinarians submitting to EMAI for tick fever testing, note the following:

• Smear slides should be labelled with animal ID and whether each is a ‘thin’ or ‘thick’ smear
• Submit smears in a plastic slide transport container to prevent breakage during transit
• Submit whole blood (EDTA) chilled
• Clearly label specimens and send in appropriate packaging via courier to the NSW APHL:

NSW Animal and Plant Health Laboratories  
Elizabeth Macarthur Agricultural Institute (EMAI)  
Woodbridge Road  
Menangle NSW 2568  
Phone: 1800 675 623

• If you do not routinely dispatch samples to EMAI, contact laboratory customer service (1800 675 623, laboratory.services@dpird.nsw.gov.au) in advance for assistance with dispatch logistics.

For detailed information of sample collection, smear preparation and submission for tick fever diagnosis visit the NSW DPIRD Laboratory (EMAI) website, Tick Fever of Cattle .

A vector is required to transmit the tick fever organism from one animal to another. In Australia, the bloodsucking cattle tick Rhipicephalus (Boophilus) microplus is the vector for tick fever.

The Babesia parasites are taken up from an infected animal when female ticks engorge with blood. The parasites are then transferred through the tick’s eggs to the larvae or ‘seed ticks’. The disease is spread when these ticks attach to a new host and subsequently infect it by injecting their saliva, which is carrying the parasites. Not all ticks become infected, nor do all larvae from these ticks become infective.

Babesia bovis develops rapidly in infected cattle ticks and is spread to other cattle by the larvae as they feed while Babesia bigemina takes longer to mature in infected ticks and is only spread by nymph and adult ticks.

In Australia Anaplasma marginale is mainly transmitted by male cattle ticks as they move from animal to animal in close contact. Male ticks typically spend more than two months on a host, much longer than female ticks. Anaplasma can also be spread by blood transmission by contaminated equipment like syringes and ear pliers. Transplacental transmission also occurs with anaplasmosis.

Tick fever occurs sporadically in the Far-North Coast region of NSW due to proximity to cattle tick endemic regions of Queensland.

Tick fever does not present a risk to humans.

Control and prevention

Following confirmation of the disease, further losses in a herd can be prevented by treatment and tick eradication.

Treatment for tick fever is conducted under the advice of a practicing veterinarian, as the drugs required for treatment require veterinary prescription.

In cattle tick endemic areas in northern Australia tick fever vaccine is regularly used to protect cattle. The vaccine has a short shelf life as it contains living organisms so must be used straight away. It is available from the Tick fever centre at Wacol Qld.

Additional information

• NSW DPIRD Cattle Tick Resources
• Cattle tick
• NSW DPI Cattle Tick - Tick Fever Procedure PDF, 190.82 KB
• Tick fever technical information for veterinarians PDF, 2060.84 KB
• NSW DPI Laboratory (EMAI) – investigation of tick fever