Diseases

Identification, Prevention and Control of External Parasites on Horses

EXTERNAL PARASITES
External parasite infestation can cause irritation and unthriftiness in your horse. Some external parasites can help proliferate lifecycles of internal parasites. External parasites may also carry infectious diseases. External parasites however may be easier to detect visually, which helps to determine program effectiveness and type of parasitic infestation. ALWAYS consult your veterinarian if you have any concerns. He or she is a very good subject matter expert.

CHEMICAL SAFETY
Fly repellents are very dangerous chemicals and care should be taken to wash off any residue remaining from any overspray or contact on your hands / other body parts. with soap and water. Wash any clothes or gloves that come in contact with these agents. All hazardous chemicals should be stored as per the label in secure storage and be properly disposed when outdated. Mixing chemicals such as DMSO can cause serious health problems.

COMMON PARASITES
Bots (Stomach bots & Gasterophilus)
Physical Description
Mature botflies have an appearance similar to a honeybee. The eggs are light brown specks the size of pin heads in small clusters.

Lifecycle
The female botfly lays her eggs directly to a hair on the horse in areas that will be able to be in contact with the horse's mouth. The areas most commonly targeted are the legs, lips and other spots that allow direct contact with the mouth and nostril during self grooming or grooming another horse. Licking the attached botfly eggs will cause them to hatch and produce the larvae. The hatched larvae will then migrate to the tongue or gums of the horse and burrow in or attach itself for the 3 weeks incubation period. Following the incubation period they free themselves and pass to the lining of the stomach for a duration of approximately 9 months. After the 9-month period the larvae are transported out of the stomach via manure to become an adult botfly. The activity of an adult botfly will last from late spring until the first hard frost.

Problems Caused by Bots
The botfly larvae may cause only minimal damage to the horse, the biggest threat would be intestinal obstruction due to infestation. The larvae may also reduce the efficiency of the stomach to digest effectively.

Signs of Infestation of Bots
If any botfly eggs are observed to attached to your horse you should consider that your horse has ingested some of them. If eggs are observed remove with them as soon as possible with a Bot knife to reduce ingestion.

Black Fly
Physical Description
Small grayish-black fly.

Breeding Habitat
Require moving water such as streams and pond overflows.

Favorite Biting Area on a Horse
Belly lines, inside the back legs and in the ears.
Diseases Commonly Carried or Problems Caused
General irritation to horse.

Deer Fly
Physical Description
Large flies capable of inflicting a painful bite.

Breeding Habitat
Plants around water's edge or salt marshes.

Favorite Biting Area on a Horse
Entire body.

Diseases Commonly Carried or Problems Caused
Equine Infectious Anemia and very painful bites.

Face Fly
Physical Description
Small grayish-black fly.

Breeding Habitat
Fresh cattle manure.

Favorite Biting Area on a Horse
Generally on horse's face.

Diseases Commonly Carried or Problems Caused
Cause some eye problems but mostly a nuisance to the horse.

Horn Fly
Physical Description
A very small fly that congregates in large swarms.

Breeding Habitat
Fresh cattle manure.

Favorite Biting Area on a Horse
Horse's neck, shoulders and abdomen. They also target skin unprotected by hair loss.

Diseases Commonly Carried or Problems Caused
Contribute to severe dermatitis leading to skin ulcers.

Horse Fly
Physical Description
Very large fly capable of inflicting a painful and deep bite.

Breeding Habitat
Water puddles, lake or pond water's edge, salt marshes, or plant debris.

Favorite Biting Area on a Horse
Entire body.

Diseases Commonly Carried or Problem Caused
Equine Infectious Anemia and Very painful bite.

House Fly
Physical Description
The common everyday housefly.

Breeding Habitat
Manure or use a wide range of organic materials.

Favorite Biting Area on a Horse
Tear ducts and around the horse's eye.

Diseases Commonly Carried or Problems Caused
Transmit stomach worms and prolific transmitter of vertebrate pathogens. General nuisance to horses.

Lice
Physical Description
About 1/8 inch in length. May vary in color from white to dirty gray.

Breeding Habitat
Remote areas of horse.

Favorite Biting Area on a Horse
Remote areas, dry patches of skin, head, neck, mane or tail.

Diseases Commonly Carried or Problems Caused
Some weight loss, stunted growth or anemia. Very irritating bite that may lead to rubbing the hair off the skin.

Mosquitoes
Physical Description
Small winged insect with prominent bloodsucking probe extending from head.

Breeding Habitat
Standing water, old tires, barrels and other objects capable of holding water and blocking wind.

Favorite Biting Area on a Horse
Entire body.

Diseases Commonly Carried or Problems Caused
Prolific transmitters of disease and associated with Equine Encephalomyetis, Equine Infectious Anemia and West Nile Virus.

Stable Fly
Physical Description
Very similar in appearance to the housefly, but the stable fly has large mouth.

Breeding Habitat
Hay contaminated with urine and manure.

Favorite Biting Area on a Horse
Legs and abdomens.

Diseases Commonly Carried or Problems Caused
Helps contribute to the transmission of Equine Infectious Anemia and summer sores.

Ticks
Physical Description
Small brownish watermelon seed shaped insect and peanut sized cream colored when full of host's blood.

Breeding Habitat
Eggs laid on ground then larvae ticks migrate to trees or shrubs.

Favorite Biting Area on a Horse
Inside ears or remote spots.

Diseases Commonly Carried or Problems Caused
Sleeping Sickness, Lyme disease, Piroplasmosis and EIA.

EXTERNAL PARASITE CONTROL PROGRAM
Just like dewormer chemicals, there are many fly repellent systems available for a wide range of external parasites. Before relying solely on chemical repellents you may consider a first step of prevention and reduction. As you probably noted most external parasites required water or fresh manure as a breeding ground. If the breeding ground is limited so will the parasites.

Before purchasing an insecticide or repellent you may want to read label to ensure this product is safe and will be an effective part of your program. You may also want to use one product at a time to reduce chances of the parasites becoming resistant to both products during the same period. Switch to another insecticide before the parasites become resistant.

Below are listed some tasks that will help reduce the parasite population:
– Remove and properly dispose of materials that may be breeding grounds at least every seven days. Preferably you should remove any suspected breeding material daily.
– Design or arraign stables, paddocks and pasture so that they allow easy waste removal.
– Ensure good drainage for rainwater and at wash racks.
– Turn off barn lights at night or use fluorescent lights.
– Clean water buckets regularly and use repellents.

Monitor which parasites are most prolific and then establish a sound plan to reduce their numbers. Contact your veterinarian, County Extension Agent or other experts in your area for specific advice. When spreading manure attempt to place as thin a layer as possible in order to speed up drying out the manure. Add horse manure to a compost pile to help segregate manure from horse living area. Ensure you follow all directions for disposal of any insecticide, these chemicals can be very lethal and can easily make their way into ponds, lakes, streams and ground water. The insecticides must also be kept in the original container.

Commonly biting flies are very active during hours of bright daylight. Set up your repellent or stabling program around that period. Common offense techniques and methods that can be very successful yet very environmentally friendly are Fly Predators. The Fly Predators are small sterile non-stringing forms of wasps that eat fly larvae. There are also systems that use propane gas to expel CO2 gas to attract mosquitoes and similar insects then suck them into a trap. Both systems work exceptionally well.

Old fashioned, tried and true methods can include fly tapes, baited bottle traps or poison baits Machines such as Mosquito Magnets lure and destroy mosquitoes as well as other similar insect pests. There are also powders and liquids that can be applied to the ground and plants which will kill insects. As with any chemicals read and follow the label so as you don't harm any animals or children.

Protective clothing such as fly masks or full body fly sheets. It has been reported that herbal remedies such as vinegar or garlic consumed orally will help the horse become less attractive thus bitten less. External parasites will never be 100% controllable, but having an effective program with monitoring will aid in your horse having a life of quality.

SKIN PARASITES
Horses may have several skin problems or skin parasites. Proper diagnosis by your veterinarian is important to quickly rid your horse of any skin problems.

Mange
Physical Description
Extremely small, must use magnifying glass to see.

Breeding Habitat
Under host's skin.

Favorite Biting Area on a Horse
Upper layers of skin.

Diseases Commonly Carried or Problems Caused
Irritations of skin which may lead to severe dermatitis or secondary infections. Proper nutrition will help prevent infestation.

Rain Rot (Dermatophilosis)
Physical Description
A microscopic rod-shaped bacteria that causes raw open sores under matted crusty hair.

Breeding Habitat
Horse's skin during periods of wet / moist and warm weather. The bacteria live in the soil and proliferate during long periods of wetness.

Favorite Biting Area on a Horse
A location on a horse that stays moist and warm allows these microscopic bugs to flourish.

Diseases Commonly Carried or Problems Caused
Irritations of skin which may lead to severe dermatitis or secondary infections. Cleaning infected areas with a medicated shampoo, betadine or cooper salt-based solutions. In rare severe cases veterinary care may be required. Also called rain scald and dew poisoning when referring to the infection on lower limbs.

Ringworm (Dermatophytosis)
Physical Description
Microscopic fungus that causes small circular patches of hair loss with flaky scabs.

Breeding Habitat
Conditions most likely to cause a risk to ringworm are dark and damp conditions during fall and winter. Young horses (yearling to three years old), senior horse and sickly horses are more prone to infection. This fungus is very infectious and will spread rapidly to other horses, other animals and humans. If ringworm is suspected clean all tack, brushes, blankets or other items used on the infected horse (s) until it successfully treated.

Favorite Biting Area on a Horse
The ringworm fungus typically infects the heart girth area, face and legs.

Diseases Commonly Carried or Problems Caused
It is very important to get and keep ringworm under control. Treatments with a ringworm medicine should be aggressive and consistent and maintained until all signs are completely gone. Irritations of skin which may lead to severe dermatitis or secondary infections.

SKIN PARASITES CONTROL PROGRAM
It is important not to spread any contagious skin disease from one part of your horse to another part or from one horse to another horse. Washing your grooming tools in medicated shampoo or other disinfectant after use should prevent spreading of infections. Usually medicated (iodine based) shampoos will fix minor skin problems. If veterinarian assistance is required, follow the instructions thoroughly to ensure complete infestation elimination.

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