Non-treatment management practices that can help reduce parasite infections in herds include:
- Quarantining new livestock.
- Rotating pastures with other livestock species or horses.
- Dragging or harrowing pastures to break up manure piles.
- Managing pastures for taller grass during grazing. Most parasite larvae stay within an inch of the ground, so cattle grazing short grass can have more exposure. (Well-managed rotational grazing systems have been shown to reduce parasite loads in cattle.)
- Reducing stocking density, especially so animals are not forced to graze near manure piles.
The paper also includes a discussion of using fecal egg count reduction tests (FECRT) to monitor treatment efficacy in a herd. This involves examining fecal samples before and after treatment and counting the parasite eggs. Less than a 90 percent reduction could indicate resistance, as can a decline in percent reduction over a series of treatments. The authors note, however, that several biological factors reduce the sensitivity of FECRT in cattle compared with other livestock such as small ruminants.
The paper lists several other available tests to identify resistant parasites, but these tend to be expensive.
The paper is available online from FDA’s Center for Veterinary Medicine.
We’re interested to hear the thoughts of veterinarians and parasitologists on the ideas presented in the FDA paper. Are the factors FDA lists as contributing to resistance on target? Is the refugia concept viable? We would welcome your comments, either here or by e-mail to email@example.com.