Video 9: What is resistance and how does it develop?

Resistance is due to genetic mutations in the coccidia allowing them to escape the anticoccidial activity of some of the drugs. Thus, there are 2 factors contributing to resistance: the genetic changes and the selection pressure by the anticoccidial.

Giving resistant coccidia a selective advantage over the sensitive coccidia in the population of coccidia in the broiler facility. This allows the resistant coccidia to become the predominant coccidia in the population within the broiler facility.

The probability of resistance is dependent on the mode of action of the anticoccidial.

  • Chemicals have a simple mode of action and therefore coccidia can develop resistance to them readily. Sometimes with only a single gene mutation.
  • Ionophores have a complex mode of action and are thus much less likely to any kind of resistance due to the many complex genetic changes that would be required on the coccidia to escape this complex mode of action.


Take a look back at the other videos from the series:

Video 1: Quantifying the costs of coccidiosis

Video 2: Measuring the efficacy of an anticoccidial

Video 3: Evaluating chemicals for coccidiosis control and prevention

Video 4: Evaluating vaccines as a coccidiosis control option

Video 5: Using ionophores to provide long-term control of intestinal integrity

Video 6: Understanding ionophore-nicarbazin combinations

Video 7: Synergistic success of narasin and nicarbazin

Video 8: What to expect when using ionophore programmes