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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.

Treating reactions to tick fever vaccines

Babesia reactions

Imidocarb (Imidox®) is the only available drug that treats reactions to both species of Babesia. Read the manufacturer's instructions before using this drug.

Inject 1mL per 100kg live weight under the skin, preferably in the neck. It may cause some tissue damage, so, if the dose exceeds 5mL, split the dose over 2 injection sites.

Treatment may eliminate vaccine organisms before durable immunity develops, so you should revaccinate cattle 8 weeks after treatment.

The withholding period for imidocarb is 28 days for meat. Restrictions apply to the treatment of lactating dairy cattle, but a permit has been issued for a 14-day withholding period for milk.

Anaplasma reactions

You can treat Anaplasma reactions using oxytetracycline or imidocarb. Read the manufacturers' instructions before using these drugs.

Option 1

Inject imidocarb at 2.5mL per 100kg live weight under the skin. This dose rate cannot be used in lactating dairy cows.

Option 2

Administer oxytetracycline treatment as per the veterinarian's recommendations.

Oxytetracycline is the preferred treatment because the use of imidocarb could impair the immunity provided by the Babesia components in the vaccine. Restrictions apply to the supply of this drug, so talk to your local veterinarian.

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