Ticks are economically the most significant external parasites of livestock. Heavy infestations cause direct harm (blood loss, a reduced rate of live weight gain, a lower milk yield, and a degradation of hide quality) and indirect harm (tick-borne diseases such as redwater, heartwater, anaplasmosis, and sweating sickness).
Efficient tick control enables profitable stock farming. Without it, it would probably have been impossible to farm with cattle in many regions of South Africa where high tick populations of single- and multi-host ticks occur.
To plan a complete external parasite control strategy, farmers need to know all the information available for their farms on the following:
In South Africa, 85 Ixodidae (hard) tick species and 21 Argasidae (soft) tick species have been identified. The following are of economic importance to livestock farmers:
They all have different lifecycles and anything from one host up to three. The lifecycle has four distinct stages of development: egg, larva, nymph, and adult. Depending on the tick species, the different stages can survive in the veld for between six and eight months without a host.
To distinguish between the different species, one needs to look at their size, mouthparts, and the patterns/colouring on their legs and bodies. All the engorged female ticks may appear to look the same from a distance (blue-grey in colour) and can all be mistaken for blue ticks.
If you have identified all the different tick species that occur on your farm, you can adapt your dipping methods and frequency to reduce their numbers, which help to reduce tick-borne disease outbreaks and the mechanical damage they cause.
Knowledge on the seasonal occurrence of a tick species identified on the farm is an important factor in the successful control of external parasites by reducing the ticks’ numbers, for example:
One-host ticks: Although tick numbers might still be low between October and December, farmers need to implement a strategic dipping programme during these months to reduce the high tick populations that will occur from February to May. To put this into perspective; every engorged female blue tick lays between 2500 and 3500 eggs. If only 200 ticks survive and lay eggs from October to December, more than 400 000 tick larvae will hatch in the next 30 to 60 days. By reducing the early-summer peak (reducing the number of females that can lay eggs), we reduce the late-summer peak. During the months of February to May, dip intervals may have to be shortened where needed to reduce the high number of ticks.
Product choice and tick-control regime:
A number of products available in the form of either a pour-on, dip (spray race/plunge dip), or injectable are available with different trade names. These products represent five chemical groups: organophosphates, synthetic pyrethroids (i.e. cypermethrin), formamidines (i.e. amitraz), macrocyclic lactones (i.e. ivermectin), and chitin synthesis inhibitors or growth regulators. The product and method of choice will depend on the type of ticks that occur on your farm and the number of animals that need to be dipped:
Other factors to consider with a tick-control strategy:
The previous tick-control and -resistance history of the farm, total/tactical strategic tick control, the use of vaccines against tick-borne diseases, and movement of animals to rested camps: All this information should be considered when deciding which control method(s) and product(s) to use on a specific farm to ensure effective control.