Equine Parasitology

19/03/2022

THE BOT FLY - GASTEROPHILUS INTESTINALIS
Adult bot flies are brown, hairy and bee-like with one pair of wings and measure about three-quarters of an inch. The larva is also three-quarters of an inch long with a narrow hooked end and a broad, rounded body. In the warm summer months adult bot flies are a common sight around horses. Yet this adult stage is just a brief part of the bot fly lifecycle. Female bot flies have no mouthparts so they cannot feed. They live in stored reserves only long enough to lay eggs on the hair around a horse’s eye, mouth, nose or on the legs. Moisture from the skin or from the horse’s licking causes the eggs to hatch into larvae.

THE BOT LIFE CYCLE
After a three-week developmental period in the mouth, bot fly larvae of both species, Gasterophilus intestinalis and Gasterophilus nasalis migrate and attach themselves to the mucous lining of the horse’s stomach and remain there during the winter. After about 10 months they detach from the lining and are passed out of the body through the faeces. The larvae burrow into the ground and mature. Depending on the conditions, adults emerge in three to 10 weeks. Adult females deposit eggs on the horse’s legs, shoulders, chin, throat and the lips. Depending on geographic location, the lifecycle of bot flies is not fixed to only certain times of the year and bot larvae can be active in horses anywhere from August to May.

Egg laying begins in early summer. Eggs of the two species differ in colour and placement. Gasterophilus intestinalis lays up to 1,000 pale yellow eggs on the horse’s forelegs and shoulders. Moisture and friction from a horse licking itself cause the eggs to hatch in about seven days. After hatching, Gasterophilus intestinalis larvae are licked into the mouth. Gasterophilus nasalis lays about 500 yellow eggs around the chin and throat of the horse. These eggs are not dependent on the horse licking them to hatch. Gasterophilus nasalis burrows under the skin to the mouth, wandering through it for about a month before migrating to the stomach for over wintering. Then the cycle begins again.

06/07/2021

Spanish researchers concluded that the pour-on ivermectin preparation was highly successful against gastrointestinal nematodes, but Turkish scientists found it less effective at reducing the faecal strongyle worm egg count.

06/07/2021

"Results indicate that properly selected plant additives obtained from arable crops may be helpful in limiting the numbers of drug-resistant strongylids."

05/07/2021

https://youtu.be/kZudmlwV8dU

Get a full insight into the process and learn how a FEC test is performed.https://au.virbac.com/3dworming

26/06/2021

Keeping bot fly presence on your property under control will reduce/eliminate this problem.
By understanding the bot fly life cycle, it is possible to successfully manage infection. See additional post for life cycle.

04/12/2018

New product that may help break the worm cycle

Introducing the world’s FIRST biological control for infective nematode larvae for grazing animals!

BioWorma® and LIVAMOL® with BioWorma® contain the spores of Duddingtonia flagrans, a natural fungus found in soil and on pasture. When fed to grazing animals the spores of Duddingtonia flagrans pass through into the manure. There they germinate and form trapping organs that capture, paralyse and consume emerging worm larvae…

✔ It is a non-chemical biological control for the free-living stages of parasitic gastrointestinal nematodes of grazing animals
✔ Acts by substantially reducing the numbers of infective worm larvae emerging from manure onto pasture (including chemical/multi-resistant larvae)
✔ Biological control with Duddingtonia flagrans is applicable to the larvae of Horses, Cattle, Sheep, Goats and other grazing animals including Deer, Alpacas and Zoo animals
✔ A natural fungus that is safe, non-toxic and residue-free
✔ No negative effects on non-target soil nematodes, earthworms, microarthropods etc.

For more information see www.duddingtonia.com and www.iahp.com.au
Contact International Animal Health Products free call 1800 801 201 (AUS) or 0800 424999 (NZ)
Official product launch date to be advised for 2018

19/02/2018

Bot larvae at the 1st instar stage of development in the interdental spaces in a horses mouth.

17/02/2018

Bot treatment time... remember to treat your horses now regardless of FEC results - bot presence does not show up in FEC tests. Use ivermectin, abamectin or moxidectin.

GASTEROPHILUS or Bots
Infection occurs during the summer months. Adult flies are active in early summer & have one life cycle per year with 3 larval stages. G. intestinalis (common bot fly) has a yellow egg & mainly deposits on forelegs & flanks of the horse. The egg develops over 5 days & requires moisture & friction to hatch. Once in the horses mouth, the larvae pe*****te the anterior end of the tongue, the buccal mucosa (cheek tissue) or gum at the interdental spaces between the teeth & remain there for approx. 28 days. After wandering in the mucosal tissue in the mouth, larvae moult to 2nd instar stage & pass to the stomach. After 5 weeks in the stomach they moult to the 3rd instar stage with the vast majority of larvae attaching to the mucosa of the oesphageal region. The larvae remain immobile in the stomach for the following 9 - 12 months. Once larvae reach maturity they detach are then passed in the manure & pupate in the soil within 3 - 4 weeks.
The adult fly emerges after a 3 - 10 week period and quickly find a mate with mating activity generally occurring in the early afternoon during warm, sunny weather in relative proximity to horses. Within hours of mating the female fly begins host seeking & oviposits her eggs on the horse. The adult fly's life span is 7 - 10 days. The adult fly has non-functional mouthparts & does not feed.
Most of the bot eggs you see on your horse are empty cases as the larvae have already hatched & have been ingested by your horse.
***Many horses with high burdens show little if any clinical evidence of infection.***
Treatment - Mectins (ivermectin - Equimax LV & Equimec, abamectin - Equimax, Ammo & MecWorma & moxidectin - Equest) are the compounds of choice for treating bot infection. Treatment should be given after fly activity has ceased & after the larvae have established in the stomach but before gastric damage has occurred.
Management - Close vigilance during times of fly activity can help minimise infection by using a bot knife to cut off eggs or washing with warm water & an insecticidal solution inducing the eggs to hatch & killing the larvae. The 1st stage larvae die soon after hatching if they do not reach the mouth of the host.
Spraying the horses body with an insecticidal spray ie. Muscoban, or a simple homemade spray from certain herbs will reduce the infection rate. Herbs to be used include lemon balm, lemongrass, basil, tansy, wormwood, lavender or eucalyptus oil.

28/01/2018

GET A HEAD START ON YOUR WORM MANAGEMENT.
NOW is a great time to harrow your paddocks & get a head start on those worms! With rain forecast for some areas & warm days for the rest of the week it is perfect hatching conditions for strongyle eggs. The EGGS can remain viable in the pasture environment for up to 2 years but the newly hatched LARVAE only have a few days to develop & become ingested by the horse which enables them to reach adult stage & produce more eggs. Once they hatch they NEED warmth & moisture to survive & develop to a larval stage that has the ability to crawl up grass blades where they have the opportunity to be swallowed by the horse.
No horses + no rain + warm dry weather = time up for the strongyle nasties!
So get out & break up all that manure in your paddocks to promote larval development, improve manure breakdown & improve water retention in the dry soil. Leave the paddock empty of horses for a few weeks to allow complete desication of all larvae with the dry conditions ahead or even put some sheep, cattle or goats in to 'vaccum' up any lingering larvae - strongyles cant survive the ruminant digestion process. Harrows, an old gate or piece of weld mesh towed behind a quad-bike or even your car will do the trick.
Your horses next FEC test will show how effective this can be!

11/01/2018

Ivermectin toxicity in foals - it is unnecessary to treat foals this young as the PPP (infection to detection) for most of the main intestinal parasites of horses is longer than 2 weeks.