Tick resistance raises concerns

Ticks are the cause of significant annual economic losses, primarily because of the diseases they transmit. In South Africa, the blue tick species is the main culprit.

- By Izak Hofmeyr

Dr Luther van der Mescht, a parasitologist at the University of the Free State, says research points to a troubling rise in resistance in blue ticks to commonly used chemical control agents. He stresses the importance of individual farm testing - not only to identify the species present but also to determine which chemicals these ticks have developed resistance to.

Tick species are generally classified as either single-host or multi-host ticks. Blue ticks fall into the single-host category, while species such as the bont-legged and red-legged ticks are the multi-host type.

"The blue tick is usually the biggest challenge in South Africa because it mainly transmits redwater," Dr Van der Mescht explains. "The issue with the two blue tick species — the African blue tick (Rhipicephalus microplus) and Asian blue tick (Rhipicephalus decoloratus) - is that they are single-host ticks. This means they complete their entire life cycle on a single host, resulting in a shorter generational interval compared to two- or three-host ticks. Since the tick’s entire life cycle is exposed to the same chemical treatment when animals are dipped, resistance can develop much faster."