We are starting to see cases of red-worm disease this year; early signs can be subtle and easily attributed to less serious conditions, until a sudden onset of life-threatening disease can occur, which is deadly in up to 50% of horses.
Every year we see horses die from redworm, even though owners believe they have wormed adequately. So why are we still seeing significant disease?
MOXIDECTIN is the only wormer that effectively treats encysted (hibernating) redworm, and we recommend giving it to healthy adult horses, at the correct dose, in late Autumn-Winter before any encysted larvae emerge. Ivermectin & Pyrantel are not effective treatments.
WORM EGG COUNTS (WEC) DO NOT MEASURE WORM BURDEN. They measure an individual’s contribution to pasture-contamination and are a way of managing wormer-resistance. They identify low egg-shedders which are left untreated, allowing eggs that have not been exposed to wormer selection-pressure to dilute resistant worms on pasture.
WORM EGG COUNTS DO NOT IDENTIFY ENCYSTED REDWORM OR TAPEWORM, both of which can be fatal.
We do not consider it safe to only worm once a year without regular WEC until consistently low WEC have been achieved 3-4 times per year on correctly timed and sampled tests.
FALSE WEC RESULTS can occur when
1. Performed less than 2-4 WEEKS AFTER THE EGG REAPPEARANCE PERIOD of the last wormer used, because worms may still be immature and therefore not shedding eggs.
2. Manure incorrectly sampled or stored (3 pinches from 3 balls, refrigerated in an airtight bag is required)
3. Tested in winter when egg-shedding is reduced.
We believe WEC are very important for sustainable worming programmes, but
SAFE targeted worming using WEC requires a thorough understanding of:
1. Individual & herd factors such as age, disease or medications
2. Pasture management (stocking-density, poo-picking, co-grazing…)
3. The actions of all types of wormers
4. Worm life-cycles (egg, larval, adult & intermediate host stages)
5. The latest veterinary research.
Currently, re-emergence of large stronglyes, a cause of serious colic, is occurring in Denmark, probably due to very infrequent worming following negative WECs. We are incorporating this into our worming advice for 2017 to manage the risk.