Over the last century many advances have been made in the management of livestock production systems. Looking holistically at red meat production, we manage systems (Figure 1) and within these systems we manage risk.

 Figure 1: A systems approach to managing risk.

Input refers to all the activities needed for the production of safe meat such as land, cattle, grazing, management and many more. Process refers to all the activities we do with these inputs or animals in a process to gain output (immunisation, dip, deworming, feeding, etc.). All of the above does not take place in an isolated space, but is exposed to the environment. This is where the risk factor comes in.

Ticks, as vectors of disease and damaging agents, impact directly and indirectly on the economic output of the livestock industry in Southern Africa. The risk associated with their presence cannot be ignored. We estimate the cost of acaricides alone in the control of ticks amounted close to R104 million in 2016.

Ability to transmit diseases

The veterinary and economic importance of ticks has long been recognised due to their ability to transmit diseases, not only to animals but also to humans. Approximately 80% of the world’s cattle population of 1 281 million are at risk from ticks and tick-borne diseases. Over a decade ago McCosker (1979) estimated global costs of control and productivity losses to be some US$7 000 million annually.

In Africa, with around 186 million head of cattle, ticks and tick-borne diseases are the most serious constraints to increased production. Weekly or twice-weekly applications of chemical acaricides are still a common form of control. However, immunisation against tick-borne diseases and the strategic application and use of drugs have recently been receiving increasing attention.

Ticks cause great economic losses and adversely affect livestock hosts in several ways. Loss of blood is a direct effect of ticks but they also act as potential vectors for blood parasites. Blood sucking by large numbers of ticks causes reduction in live weight and anaemia among domestic animals, while their bites also reduce the quality of hides. However, major losses caused by ticks are due to their ability to evoke disease.

New acaricides

The development of new acaricides is a long and very expensive process. Worryingly, there is increasing resistance to available acaricides leading to the real possibility that our dwindling supply of effective acaricides will be exhausted unless alternative approaches are taken to manage ticks.

Recent years have seen great progress in approaches to drug development and tick control strategies. Such advances will undoubtedly help to decrease the risk associated with ticks and diseases. One simple strategic approach is by the use of chemical products and drugs at the right time of the year, such as planning ahead in winter for the summer explosion of ticks and diseases.

Tick numbers (especially blue ticks) follow a predictive population growth curve. In Figure 2 the green line indicates the normal growth curve of blue ticks. Soon after the first seasonal rain in September or October, we see an exponential increase in tick numbers reaching a high around February to early April. During this peak population times the risks are at its highest for major economic losses.

Figure 2: Tick population growth curve.

A simple though effective risk management plan is to treat all animals around three weeks after the first good rains in spring, with an injectable macrocyclic lactone product. This will decrease the potential second and following generation of ticks (F2 – F5, etc.) and thus lower the pasture contamination and potential risk.

Dip all animals

In the absence of pyrethroid resistance in ticks, a good option is to follow up the treatment of all animals with a flumethrin type dip. The idea is to obtain a parasite population as indicated by the red line in Figure 2. Enough ticks should still be present to ensure endemic stability to tick transmitted diseases, but low enough numbers to prevent economic losses. Critically important is dip tank testing and resistance surveillance to establish baseline values for future control strategies.

In the area of tick control, much has been achieved, but much more remains to be done. Problems with acaricide resistance make the managing of risk around tick control ever more important. – Article supplied by Afrivet

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