The cattle tick is an economically serious external parasite affecting, primarily, cattle. It is one of the most economically important diseases of cattle in Australia. If left unchecked, cattle tick can significantly reduce cattle live-weight gain and milk production. It is also responsible for transmitting Tick Fever.
The cattle tick, Rhipicephalus microplus, formerly known as Boophilus microplus, affects primarily cattle but can also infest other species such as sheep, horses, goats, buffaloes, camels, alpacas, llamas and deer. It is responsible for transmitting three blood-borne tick fever organisms, Babesia bovis, B. bigemina and Anaplasma marginale, which cause “Tick Fever”. Tick fever results in sickness and death in cattle.
The best time to identify the cattle tick is when it is at the adult stage. When cattle are heavily infested, ticks can be found anywhere on the body. On a lightly infected animal the main places to look are the escutcheon, tail butt, belly, shoulder, dewlap and ears. Other ticks which may be commonly found on cattle and can be confused with cattle tick are scrub ticks, New Zealand cattle (or bush) ticks. Correct tick identification is vital. Species of ticks other than cattle tick may also cause stock losses, but their life cycle and therefore control are different to cattle ticks.
In Australia, the distribution of cattle tick is limited by legislated movement controls of cattle and other susceptible species. The tick infected zone comprises the coastal area east of the Great Dividing Range and north of the Great Northern Rail line in Queensland. Cattle ticks are also found in the northern areas of Western Australia and the Northern Territory. Cattle ticks occur sporadically through the northern rivers area of New South Wales. In these states and territory, there are legislated movement controls in place to prevent the movement of cattle ticks to the south of the “Tick Line”. Cattle tick outbreaks can and do occur in the tick free zones from inappropriate cattle movement. Outbreaks are more common in the marginal areas adjacent to the infected zone.
Heavy cattle-tick infestation causes loss of condition and even death because of tick-worry and blood loss. Tick fever can also cause illness and death in cattle. Hides of heavily infested animals are damaged by tick bites which reduces their value. In severe cases hides may be unsaleable.
Cattle are particularly vulnerable when they first encounter cattle ticks but develop a degree of resistance after repeated exposure. Bos indicus cattle (tropical breeds) and their crosses develop better resistance than do Bos taurus (British and European breeds). Horses, goats and sheep also suffer tick-worry but after a period of time they will develop strong resistance.
The cattle tick is a single host tick, meaning that it spends the parasitic stage of its life on the one host. This stage takes approximately 21 days, during which the tick changes from a minute larva to a nymph and finally an adult. Adult females feed slowly for about a week before rapidly filling with blood just prior to detachment. They then drop onto pasture, lay up to 3000 eggs and die. Eggs hatch to produce larvae which infest the pasture until picked up by a suitable host or they die.
This non-parasitic stage on the pasture can vary from approximately two months in summer to six to seven months over winter and numbers are adversely affected by extremes in temperature and moisture levels. Adult males feed occasionally, but do not fill with blood. They wander over the beast for two months or more, mating with females. Because they do not engorge, male ticks are relatively small.
In southern Queensland, ticks that fall between mid-April and late June produce virtually no progeny due to cold winter conditions. However, engorged female ticks dropped in early autumn can produce larvae that will survive the winter and eventually result in a spring rise in tick numbers. If not controlled, these ticks breed up to a stage where there are great numbers in autumn and early winter the following year.
In the north of Queensland, ticks lay viable eggs year round. Further south, the reproduction cycle slows during winter. Heavy rain during the wet season can interfere with tick reproduction.
Management and Control
Cattle ticks can be controlled to varying degrees using tick-resistant cattle, strategic treatments with chemicals, use of a cattle tick vaccine, pasture spelling or combinations of these methods.
Before entering tick free or control zones, stock from the tick infected zone must be inspected clean and treated. Contact relevant state government animal health officers for more details of movement restrictions and the necessary legislated treatments that must be undertaken.
Cattle tick control is aimed at preventing the “spring rise” by commencing a strategic treatment program in the late autumn and early spring.
Avoid chemical residues
It is essential that producers observe withholding periods and retreatment intervals with chemicals used for cattle tick control. Producers must be aware that retreatment intervals apply to all chemicals in that class and not just that particular product because chemicals in the same family will be excreted using common mechanisms. This applies in particular to members of the macrocyclic lactone group of chemicals.
Cattle ticks are an economically important parasite of mostly cattle but also a number of other species. Their distribution is limited by a regulated control strategy managed by state governments throughout Australia. Control involves the use of non-chemical and chemical means. Strategic chemical based control programs begin in the spring months and aim to prevent the spring rise in tick numbers or part of the regulated “tick clearance” procedures involved in moving cattle south of the “tick line”.
*Photo courtesy of Queensland Primary Industries and Fisheries.