Farmers could switch to DIY spore counting as the summer risk of facial eczema looms. By Lisa Whitfield.
As we head through mid-summer, facial eczema season looms large on the horizon for northern farmers. Spore counting is the measure of risk for facial eczema, and one of the big frustrations I have seen from proactive farmers is significant delays getting spore counting results back for their properties. So have you ever considered doing your own spore counting?
If you can find your way around a microscope, then you could do your own spore counting. Onfarm spore counting allows you to get timely results as you need them, and to check samples for little cost. It takes eight to 12 minutes to process and count each pasture sample.
What you need:
- Microscope (with 10 x magnification lens)
- 60 grams of grass
- A 1L leak-proof container
- A spore-counting slide and coverslips
- 1ml pipettes
- Clean water
After collecting a representative sample of grass from the paddock of interest, a 60-gram grass sample is weighed out into the leakproof container 600ml of clean water is added to the container, and with the lid in place it is shaken vigorously for three minutes.
The grass is removed from the container and a sample of water is collected with a pipette. A drop of the water is placed onto the spore counting slide over the grid and a coverslip placed over the water drop. The slide is ready to be examined under the microscope.
The counting grid consists of a 3×3 set of squares, which is further subdivided into smaller squares used for other lab work. For spore counting you use the larger 3×3 formation of squares. All facial eczema spores found in the centre and each of the four corner squares are counted. There is a lot of debris and other types of spores found in the mix, so learning what facial eczema spores look like is important. Facial eczema spores are described as looking like hand grenades, and only these spores should be counted.
Three further samples from the water are counted for spores and the counts tallied up. The spore count for the paddock is calculated by multiplying the total number of spores by 5000.
There are variations on this methodology, so ask your vet clinic for the methodology they use to count spores. If spore counting is not for you, then get your clinic to check your grass samples for you. Spore counts are the only tool available for assessing the risk to your stock. They allow you to decide when to start your facial eczema control program, as well as when it is safe to end it. There are such wide variations in counts between farms, and even between paddocks on farms, that relying solely on regional spore counts for risk assessment is problematic and may mean you get caught out.
Facial eczema is a devastating disease which has a significant welfare cost in cattle, sheep and camelids each year. Spore counting is the best place to start to assess the risk to your stock, as part of a complete control programme.
- Lisa Whitfield is a Production Animal Veterinarian in the Manawatu.
