Elliott Clifton BVSc MRCVS Worming your horse. Elliott Clifton BVSc MRCVS

Worming Worming advice can be confusing and controversial Blanket treatment is outdated Strategic and targeted approach needed Resistance issues important

The Worms Nematodes Cestodes Lungworm Large Redworm Pinworm Tapeworms Worms (Helminths) Nematodes Cestodes Lungworm Large Redworm Pinworm Tapeworms Small Redworm Roundworm Threadworm

Probably the most common worm in our horses Over 40 different species Small Redworm (Cyathostomes) Probably the most common worm in our horses Over 40 different species The larvae of these worms hibernate (encyst) in the large intestine wall Emergence of these larvae can be fatal.

These worms can be serious Large Redworm (Strongyles) These worms can be serious There is extensive larval migration within the abdomen Their lifecycle can be 6 – 11 months long Rapid weight loss, diarrhoea and potentially surgical colic Rarely become clinical because of regular worming now.

Typically affects foals Complete lifecycle can take place on pasture Threadworm (Strongyloides westeri) Typically affects foals Complete lifecycle can take place on pasture Diarrhoea is the prominent clinical sign Natural immunity is usually present at 6 months of age.

Eggs can survive in the soil Roundworm – Parascaris equorum Can be up to 50 cm in length!! Eggs can survive in the soil Greatest risk is 6 months to 2 years of age Respiratory signs as well as diarrhoea and weight loss.

Donkeys are the main host Horses can’t complete the lifecycle Lungworm (Dictyocaulus arnfieldi) Donkeys are the main host Horses can’t complete the lifecycle Respiratory signs

Pinworm (Oxyuris equi) Adults live in the colon (large intestine) Females deposit eggs around the anus Causes intense itching.

Oribatid (forage) mite is intermediate host Tapeworm (Anoplocephala) Oribatid (forage) mite is intermediate host Adults live in small intestine and caecum Infestation can cause intususception or food impaction

Bots (Gastrophilus) Their lifecycle takes one year Migrate through horses mouth and latch onto stomach wall Can cause inflammation of oral cavity and contribute to gastric ulcers

Adults live in the nuchal ligament for years.. Neck Threadworm (Onchocerca cervicalis) Adults live in the nuchal ligament for years.. Larvae cause severe itching and skin reaction Can cause ocular disease Spread by biting insects (midges) Climate change?

Stomach Worm (Habronema) Attach to stomach wall House and stable fly intermediate hosts Can cause severe wounds and gastritis (inflammation of stomach wall)

RESISTANCE!!! Ability of parasites (organisms) to survive a dose of treatment which would normally be effective Resistance to fenbendazole (Panacur) well documented Some evidence of resistance to avermectin wormers Worm-free horses do not help the issue of resistance Refugia is important

Faecal Worm Egg Counts 20% of the horse population will be infested with 80% of the worm population of that pasture Faecal worm egg counts detect eggs produced by worms except tapeworm, pinworm and bots. Just a ‘snapshot’ of the bigger picture Fresh sample, keep it cool, deliver it same day to lab/vets A count of <250 epg does not necessitate treatment Faecal egg count reduction tests to monitor treatment effectiveness and resistance Save money in the long run!

Testing for Tapeworm Can test antibodies to tapeworm in blood or saliva Saliva test easy to use and quick results – doesn’t need a vet to do Blanket treatment not necessary in a lot of cases Results have to be interpreted with care Tests can’t be use to assess wormer efficacy

The encysted stages cannot be detected using any test at present The encysted Cyathostomes The encysted stages cannot be detected using any test at present The recommended time of treatment is between November and February – this is typically when larvae ‘hibernate’ Once a year dosing for the encysted stages reduces resistance

Tetrahydropyrimidines The Drugs... Ivermectin Moxidectin Avermectins Benzimidazoles Tetrahydropyrimidines Fenbendazole Pyrantel Praziquantel

Don’t treat March/April TREAT May/June Same as above Same as above ‘Gold Standard’ Protocol Don’t treat <200epg March/April Worm egg count TREAT >200epg Test for tapeworm? May/June Worm egg count Same as above Worm egg count Same as above August/September Test for tapeworm Treat/don’t treat using Praziquantel or Double dose Pyrantel Treat for encysted cyathostomes November - Feb Treat for bots

How heavy are your horses?? Holistic Approach Poo Pick Co grazers Where’s the muck heap? Avoid ‘dose and move’ Avoid overstocking Harrowing?? How heavy are your horses??

QUIZ!!! What is PSSM an abbreviation of? Which worm can encyst in the large intestine gut wall? What disease can the ingestion of sycamore cause in horses? Which famous actor is the president of the British Horse Society? When was the Shire Horse Society set up a) 1870 b) 1901 c) 1884? Which drugs are effective against tapeworm? What is PSSM an abbreviation of?

QUIZ!!! What is the normal heart rate of the horse? What is the proper name for the equine pinworm? How high is the world record for the highest jump jumped by a horse and rider? What is the trade name for Fenbendazole? How far can worm larvae travel from a muckheap? What is the medical name for the disease responsible for a ‘roarer’?