Vaccines and Prevention

Tick fever vaccination

About the vaccine

The trivalent tick fever vaccine is a live, whole organism, blood-based vaccine containing attenuated strains of B. bovis and B. bigemina as well as Anaplasma centrale. The attenuated vaccine strains of Babesia spp are derived from Australian field isolates. A centrale is a related organism imported from South Africa in the 1930s and provides reasonable cross protection against the Australian isolates of Anaplasma marginale.

The vaccine is mostly sold in a chilled ready-to-use form with just a short 4-day shelf life. A frozen vaccine (Combavac 3in1; stored in liquid nitrogen) is available for remote areas where it can be difficult to deliver overnight, or for larger holdings where it is convenient to have vaccine stocks on hand for use as required. Combavac 3in1 is also available for export.

Clinical disease associated with use of the live vaccine is possible, but most animals show no visible reactions.

Vaccination program

Vaccination is the only reliable method for long-term protection of susceptible cattle against all three causes of tick fever.

Cattle of any age can be vaccinated, but it is best to vaccinate animals between 3-9 months of age when the age-related resistance is present and there is little risk of reactions to the vaccine. Many producers find it convenient to vaccinate around weaning time. It takes about 3-4 weeks after vaccination for immunity to develop to babesiosis and up to two months for immunity to develop to anaplasmosis.

When introducing cattle from outside the tick areas which have never previously been exposed to tick fever organisms, keep in mind this time taken for immunity to develop after vaccination. Ideally, vaccination occurs well before introduction to allow time for immunity to develop to all components of the vaccine. One dose of vaccine is sufficient in most cases for lifetime immunity; but there will always be a small percentage of vaccinated animals which do not become immune to all three organisms in the vaccine after a single dose. An argument can therefore be made for a second dose for introduced cattle and especially for valuable animals such as bulls.

Bovine anaemia caused by theileriosis

There is no specific treatment or vaccine to build immunity to theileriosis so it is important for cattle producers to manage the risk. In Australia, this disease can be managed by following an integrated plan that focuses on prevention.

Prevention and management

• When buying in new stock, ascertain their health status, particularly avoid buying animals from known affected properties or localities. A laboratory test could be utilised to assess the presence of Theileria before purchasing cattle.
• Quarantine new stock, check for the presence of ticks and consider treating with a chemical registered for the control of ticks on cattle. When using insecticides, make sure you observe the prescribed withholding periods before marketing products of treated animals.
• In areas where Theileria are commonly found (generally coastal areas, see Figure 1), source cattle locally.
• In endemic (where the disease occurs regularly) areas where most adult cattle are usually immune, calves should be closely inspected when they are 6-12 weeks old.
• Introduced cattle into an endemic area should be examined closely when they have been in the district for 3-8 weeks.
• In districts where Theileria is normally not present, but cattle from an endemic area have been introduced, check home cattle regularly between 2 and 6 months after the introductions.
• If signs of disease are noted, seek veterinary advice as treatment when animals are mildly affected has been most successful.
• Careful attention to nutrition, worm control and trace element supplementation (if required) will minimise susceptibility to theileriosis.
• Avoid mustering, movement or otherwise stressing stock around calving when there is a high risk of the disease.
• If practicable, items such as castration knives should be cleaned and then disinfected between animals. Where not possible such as vaccinating a mob of cattle, use sharp needles and change regularly to minimise blood transfer.
• Bush ticks, wallaby ticks and bandicoot ticks (all in the genus Haemaphysalis) transmit Theileria and are almost impossible to eradicate from a property as they are on and off the host in a week or so, and live in pasture for many months, as well as infesting other animals including wildlife. See also control of bush ticks.

Tick paralysis

Prevention of tick paralysis revolves around:

• Reducing paralysis tick numbers and preventing paralysis tick attachment.
• Killing attached paralysis ticks before signs of tick paralysis take place.
• Reducing susceptibility to paralysis ticks.

Reducing paralysis tick numbers and preventing paralysis tick attachment

As the paralysis tick is a 3-host tick, reducing tick numbers is less about treating the cattle and more about strategies to control the environment.

The native hosts cannot be treated with tickicides, and the most common host, the bandicoot, is a protected native species.

The most common losses are from tick paralysis in young calves so some strategies that may help reduce numbers and prevent attachment are –

• Identify low risk paddocks with a low / non-existent native host population for calving paddocks.

– Paddocks with evidence of bandicoot activity (small holes created by rooting in the soil) are best avoided.

– Bandicoots favour open grassland paddocks, especially where Sally Wattle and Black Wattle grow.

– Paddocks that have been burnt in the last 5 years are lower risk as fire destroys the population of bugs in the leaf litter that the bandicoots seek.

• Use paddocks that have historically low numbers of paralysis ticks for calving paddocks.
• Consider moving calving patterns away from the high tick danger periods of August to December.
• Removal of mulch and dead grass by slashing can help expose the off animal stages of the paralysis tick life cycle to environmental extremes and help reduce numbers.
• Treatment of adult cattle before movement into low risk paddocks may help reduce contamination by larvae, nymphs and adults.

Killing attached paralysis ticks before signs of tick paralysis occur

Unfortunately there are no long acting acaricides registered for treatment of paralysis ticks in cattle.

Treatment of paralysis ticks on cattle is usually with an amitraz, cypermethrin or flumethrin based spray. Dependant on climactic conditions, duration of activity is only 5 to 10 days. Ear tags containing synthetic pyrethroids (SPs) can aid in the control of paralysis tick on suckling beef and dairy calves for up to 42 days.

Paralysis ticks can attach to calves literally at the time of birth, and can cause paralysis as early as 4 days of age. Regular mustering to apply chemical sprays is expensive and frequently results in mis-mothering problems.

Use of home remedies such as injections of oil of turpentine have shown to be ineffective and create residue issues. Their use is strongly discouraged and indeed there use may lead to legal liability issues. The use of dietary supplements such as sulphur lick blocks has also failed to be of proven benefit for repelling ticks.

Reducing Susceptibility

It is generally accepted that herds that have a greater than 50% Bos indicus genetic content have greater innate tick resistance and therefore are less likely to be affected in tick paralysis areas (see breed selection). This strategy may be the only viable alternative in some areas.