Tick fever is a cattle disease caused by any one of the following blood parasites:
- Babesia bovis
- Babesia bigemina
- Anaplasma marginale
These parasites are all transmitted by the cattle tick (Boophilus microplus). Disease caused by Babesia bovis or Babesia bigemina is called babesiosis, often referred to as ‘red water’. Disease caused by Anaplasma marginale is called anaplasmosis.
Babesia bovis is the most important parasite, causing more than 80% of outbreaks of tick fever in Queensland each year.
Tick fever is highly prevalent in our area and will kill non-immune cattle if they are not vaccinated.
Clinical signs of tick fever
Signs of tick fever include:
- weakness
- depression
- loss of appetite
These signs are mainly due to the associated fever and red blood cell destruction (causing anaemia).
Despite the common name ‘red water’, red urine is only occasionally present and late in the course of the disease. Other clinical signs may include jaundice and neurological signs.
Cattle with Babesia bovis infections may be quite sick even in the absence of anaemia and red urine.
Diagnosing tick fever
It is difficult to diagnose tick fever based on clinical signs alone.
The best way to diagnose tick fever is to send blood smears to a laboratory for examination.
Risk factors for tick fever
Breed
British, European and other Bos taurus cattle breeds are more susceptible to tick fever caused by Babesia organisms than Brahman and Bos indicus breeds. Cross breeds (Bos taurus x Bos indicus) have intermediate susceptibility determined by the percentage of each breed type.
All breeds, including Bos indicus breeds, are highly susceptible to disease caused by Anaplasma marginale.
Age
There is a strong link between age and resistance. Most outbreaks occur in animals 18 to 36 months of age. Calves exposed to tick fever organisms between 3 to 9 months of age rarely show clinical signs and develop a solid, long-lasting immunity.
Exposure
Cattle born and raised in areas where cattle ticks are endemic can develop natural immunity through exposure to ticks infected with tick fever. However, this immunity can disappear quite quickly if the tick challenge is eliminated. We have witnessed several outbreaks of tick fever subsequent to excessive use of pour-on products.
Tick fever vaccine
Chilled tick fever vaccine is an excellent vaccine that provides strong, durable immunity from a single shot.
Shelf life and storage
Chilled vaccine is supplied ready to use. It is stored and transported at 2-8°C (do not freeze) and must be used within 4 days of manufacture.
Dosage and administration
Using a vaccinator gun, inject a single 2mL dose either subcutaneously (under the skin) or intramuscularly (into the muscle).
Animals’ response to vaccination
Animals undergo mild reactions as the immune system is stimulated to produce long-term (usually lifelong) protection against the disease.
Development of immunity
- 3-4 weeks after vaccination for both species of Babesia
- 8 weeks after vaccination for Anaplasma
- loss of appetite
Recommendations for use
Cattle of any age can be vaccinated, but it is best to vaccinate animals at 3-9 months of age when there is little risk of reactions to the vaccine.
The risk of reactions is greater when vaccinating adult cattle (especially bulls and pregnant cows) and they should be closely observed during reaction periods.
Development of tick fever immunity after vaccination
Following a single vaccination, immunity to tick fever takes 30-42 days to develop, but the immunity is usually lifelong.
Cattle can be at risk of developing tick fever if exposed to ticks before the vaccine immunity has taken effect. This is only of concern in animals older than 9 months of age.
The most common type of tick fever, Babesia bovis, is transmitted 1-3 days after the attachment of the larval (seed) tick. Pour-on and injectable tick control chemicals do not kill seed ticks soon enough to prevent the transmission of Babesia bovis. Commonly used dip chemicals have short residual activity.
Protecting cattle while immunity develops
You can minimise the risk of tick fever in introduced cattle by vaccinating at least 60 days before cattle enter tick-infested areas. This allows time for immunity to develop for all 3 tick fever organisms. If a 60-day delay in moving cattle is not possible, then:
- delay movement for 3-4 weeks after vaccination to allow immunity to both species of Babesia to develop
- isolate introduced animals from other local cattle for 60 days after vaccination to help prevent transmission of anaplasmosis
- keep animals tick-free before and for 28 days after vaccination when vaccinating animals that have been introduced into a tick-infested area. This is very difficult to achieve, so you must monitor the cattle carefully during the period when immunity is developing.
Moving cattle before immunity has developed
If it is not possible for you to delay the movement of cattle, move them before day 7 or from 21 to 30 days after vaccination.
These ‘windows’ prevent animals being transported and stressed during reaction periods, but the risk of disease from field infection still exists until immunity develops.
Reactions to tick fever vaccines
After vaccination, the organisms in the vaccine multiply and mimic the progress of naturally acquired disease. However, the organisms in the vaccine are much less virulent than organisms acquired in the field from ticks.
Calves vaccinated at 3-9 months of age rarely show visible reactions. Older cattle rarely show visible reactions after vaccination, but, in severe cases, animals may have a persistent fever or anaemia. Bulls or pregnant cattle may be most at risk.
Severe reactions are rare, but can potentially result in loss of condition, abortion, temporary reduction in bull fertility, and, on rare occasions, death. You can manage reactions by monitoring the animals and treating if required.
Note: The consequences of an outbreak caused by a virulent tick-borne infection far outweigh the risks associated with vaccine reactions. Vaccine reactions are also easier to manage than a disease outbreak because of the predictable reaction periods.
Vaccine reaction periods
- Babesia: 7-21 days after vaccination
- Anaplasma: 30-60 days after vaccination
Signs of vaccine reaction
- Babesia
- Fever
- General signs of ill health – lethargy, weakness, reduced appetite
- Red urine – also known as ‘red water’
- Anaemia – pale mucous membranes in mouth, eyes and vagina, as a result of loss of red blood cells
- Anaplasma
- Anaemia
- Weight loss
Monitoring reactions to tick fever vaccines
- Individual animals
Reactions can be detected sooner by monitoring cattle for the development of fever rather than the clinical signs associated with Babesia spp. in the vaccine.
You can do this by measuring early morning rectal temperatures in the period 10 to 21 days after vaccination. This is particularly important in bulls or heavily pregnant cows. Treat promptly if fever exceeds 40.5°C or if you see other signs of severe reactions.
Fever is not a useful indicator for Anaplasma reactions. Daily visual monitoring for clinical signs from 30 days after vaccination will be adequate.
- Paddock monitoring
With larger herds of cattle, observe the animals daily during reaction periods. Be sure to move them around to better detect stragglers and check for clinical signs. If any signs are detected, move them to yards to take rectal temperatures, collect appropriate samples and treat as necessary.
Sampling animals to confirm vaccine reactions
Samples taken from animals with suspected vaccine reactions can help confirm or rule out whether a vaccine reaction was the cause of the illness. Discuss sample requirements with your local veterinarian, Biosecurity Veterinary Officer or Tick Fever Centre staff.
Stabler and Howlett would like to thank our partners at Tick Fever Research for their assistance in compiling this post.
