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Tick Control

# Understanding Tick Resistance: Why Acaricide Rotation Is Essential

Acaricide resistance is a major threat to livestock productivity. Learn how strategic chemical rotation can protect your herd and preserve the efficacy of available treatments.

SA
System Admin
15 October 2025
6 min read
Article #01
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## What Is Acaricide Resistance?

Acaricide resistance occurs when a population of ticks is no longer effectively controlled by a chemical that previously worked. This is not a sudden event — it develops gradually over multiple generations as ticks with natural tolerance survive treatment and pass their genes to offspring.

In East Africa, resistance has been documented against virtually every chemical class used for tick control, including organophosphates, synthetic pyrethroids, and amidines. The economic consequences are severe: increased tick-borne disease, higher mortality, reduced milk yields, and wasted expenditure on ineffective treatments.

## Why Does Resistance Develop?

The primary driver of resistance is selection pressure — the repeated use of a single chemical class over extended periods. When the same acaricide is used week after week, year after year, susceptible ticks are killed while those carrying resistance genes survive and reproduce. Over time, the resistant population dominates.

Other contributing factors include under-dosing (using concentrations below the recommended rate), irregular treatment intervals, and poor dip management. Each of these practices increases the chance that partially resistant ticks survive and breed.

## The Rotation Strategy

Chemical rotation involves alternating between acaricides from different chemical classes on a planned schedule. The principle is simple: ticks that are resistant to one class remain susceptible to another, so alternating chemicals prevents any single resistance mechanism from becoming dominant.

A practical rotation programme for East African conditions might alternate between an amitraz-based product (such as Sangatraz 125® or Sangatraz 250®) and a pyrethroid-based product (such as Sangadelta®) on a quarterly or seasonal basis. The key is to change the chemical class, not merely the brand name.

## Practical Tips for Farmers

- Always use the recommended concentration — never dilute below label rates
- Rotate chemical classes every 3–4 months, or at least seasonally
- Monitor tick counts after treatment to detect early signs of reduced efficacy
- Maintain dip tanks properly — test concentration regularly and top up correctly
- Keep records of which products you use and when, so you can track rotation

### When to Seek Help

If you notice that tick numbers are not declining after treatment, or if ticks reappear within a few days of dipping, resistance may already be developing. Contact your veterinarian or Sanga Vet. Chem. advisory team for guidance on adjusting your rotation programme.

SA
System Admin
Sanga Vet. Chem. Ltd

This article was written by a member of the Sanga Vet. Chem. Ltd team. For specific veterinary advice, please consult a qualified veterinarian.

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