Withdrawal Period Milk:
N/A
Withdrawal Period Milk:
Cattle: Do not use in female dairy cattle of breeding age.
While pinworms and roundworms have fairly efficient life cycles, strongyles have a very unusual method of reproduction, especially considering that they developed in a desert environment. Large and small strongyles share identical life cycles outside of the horse but behave very differently once they're ingested.
Eggs are passed in the fecal material, just like ascarid eggs. Unlike ascarid eggs, which remain in egg form until they are ingested by the horse, strongyle eggs hatch into larvae in the manure paddy when weather conditions are favorable. From here, they go through a series of three molts. It's the third stage that can infect the horse. Under optimal conditions, third-stage larvae can live for up to three months. For their species to survive, strongyles must be ingested shortly after molting to this stage.
The Typical Life Cycle of Small Strongyles
Strongyle Larvae in Dew Drop
To increase its chances for survival, the larva climbs up on blades of grass where a horse can ingest it while grazing. This is less likely under natural conditions, because the horse herd that deposited this larvae-ridden manure may have migrated many miles.
Strongyles are prolific egg layers. A single horse can pass 75-100 million eggs daily. The eggs can crawl up and down a blade of grass many times or bury themselves in the soil to protect against adverse weather.
Small Strongyles
Small strongyles also developed another unique trait - the ability to encyst themselves in the horse's tissues and remain in an encysted state for a prolonged time. Unfortunately, it causes real problems for the horse.
This encysted state helps the small strongyle: When larvae are ingested, they immediately penetrate the bowel lining and begin a two- to three-month migration in the intestinal tract. The immune system recognizes these migrating parasites as foreign invaders and sends its defense cells to deal with the invasion. Because the migrating parasites are too large and are moving, the defense mechanism can't deal with them effectively. The only result from the immune response is mucosal inflammation.
If the horse already has an adult population of this parasite, there appears to be a communication between the adult population and the migrating larvae. This negative feedback tells the larvae, "We have enough adults laying eggs in the intestine. Slow your migration and wait your turn to become an adult." Once the larva slows its migration, the immune system can deal with this invader and surround it with scar tissue.
Cycle Requires Only Occasional Exposure
The small strongyle has developed a way to make the horse an egg-laying machine, and keep it that way with only occasional exposure to the larvae. Horses only have to pick up these infected larvae one time every two or three years for the small strongyle's life cycle to function.
Small strongyles, however, are the most significant causes of chronic under-performance, loss of condition, feed inefficiency and predisposition to secondary disease.
Strongylus vulgaris Migration
The pattern of migration for Strongylus vulgaris, a large strongyle, is quite different. Eggs are passed in the feces and develop through two larval stages. When a third-stage larva is ingested, it migrates to the large intestine, where it loses its sheath and penetrates the intestinal wall. The fourth-stage larvae penetrate the submucosal arterioles and migrate to the cranial mesenteric artery - the artery that supplies blood throughout the intestinal tract - where they molt to the fifth stage. These larvae return via intestinal arteries to the gut, where they reproduce.
Arterial Damage From Large Strongyles
No matter where a strongyle larva penetrates, leaves the gut and begins its migration, it will always end up at the same spot - the beginning of the cranial mesenteric artery, which is the primary blood source for the intestinal tract. All these larvae in one spot cause tremendous damage and reaction. In fact, in rare cases, the artery can rupture, causing rapid death. The more common problem is a weakening of the arterial wall, which can lead to a malformed artery - an aneurysm. This malformation causes abnormal blood flow, which can lead to formation of blood clots in the artery. These clots cling to the artery walls like clusters of grapes. Should one of these clots break free, it will be forced downstream in the blood supply of the intestines, where it may block blood flow. This situation, called thromboembolic colic, can result in serious illness and death.
The pinworm is a grey/white worm with a long tail, which tapers to a point. While the male is significantly smaller, the female pinworm can reach up to 20cm in length.
Infective pinworm eggs are ingested orally and, once in the colon, the larvae develop through various stages before becoming sexually mature in about five months. As horses migrate, they take the eggs and adults with them.
Pinworms have the most efficient life cycle of all the parasites that infect the horse. They don't migrate through any organ tissue, and they have developed a means of reproduction by which the eggs don't leave the herd of horses.
Although pinworms live in the large intestine and colon, the adult worm emerges at night to lay eggs on the skin around the rump. After laying her eggs, the female pinworm will then return inside the rectum. A female pinworm can lay up to 60,000 eggs per day.
Pinworm infestations commonly occur in horses older than 18 months, but rarely cause the animal major problems. Unlike many other worms, the pinworm will not cause damage to the horse’s digestive system, nor will it cause other internal damage. However, they will cause significant irritation.
When the adult worm lays her eggs it can cause intense irritation leading to rubbing and self-harm around the anus. Biting and licking of hindquarters may also be observed. There are no eggs on faecal examination. However, eggs may be seen in a gelatinous mass around the anus.
Stomach Bots are the larvae of Gasterophilus flies. The adult horse bot fly emerges a during the summer or fall season. After the fly emerges from the pupa, it quickly finds a mate, lays the eggs on the horse's coat and, on grooming, the eggs make their way to the mouth where they hatch in mouth as larvae. These larvae migrate to the stomach, causing an infestation for 8-10 months.
The larvae cause ulcerations in the lining of the stomach, and it is this which leads to disease. Disease is also caused by the larvae in mouth. Larvae here create borrowing holes, which in turn become infected. The 3rd stage larvae are passed in the faeces and over winters to develop the following summer.
Here is more information about bots and detail regarding how the Bimectin Range can be an effective weapon in your bot treatment strategy.
The Bot: More Than a Pest
Bots Flies are common in most stables. Often swatted at, but rarely hit, they are a pest poorly tolerated by horse and owner. Bot flies can be much more than just pests, however. The annoyance and distraction they cause can interfere with feeding and affect nutrition. The migration of bot larvae under the skin in mucous membranes causes lesions that may provide openings for infection. Flies also carry diseases that can seriously harm your horse's health and performance. Without treatment, bots can cause severe damage in the stomach and intestine of your horse.
A Long Life Cycle
Adult bot flies are brown, hairy and bee-like, with one pair of wings, and measure about 3/4". The bot larva is also 3/4" long, with a narrow, hooked end and a broad, rounded body. In the summer months, adult bot flies are a common sight around horses. Yet this adult stage is just a brief part of the bot fly life cycle. Female bot flies have no mouth parts, so they cannot feed. They live on stored reserves only long enough to lay eggs on the hair around a horse's eyes, 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 mucus 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 feces. 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 lips. Depending on geographic location, the life cycle 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 color and placement.
G. intestinalis – G. nasalis
G. intestinalis lays up to 1,000 pale-yellow eggs on the horse's forelegs and shoulders. Moisture and friction from the horse's licking itself cause the eggs to hatch in about seven days. After hatching, G. intestinalis larvae are licked into the mouth.
G. nasalis lays about 500 yellow eggs around the chin and throat of the horse. These eggs are not dependent on the horse's licking them to hatch. G. nasalis burrows under the skin to the mouth, wandering through it for about a month before migrating to the stomach for overwintering. Then the cycle begins again.
Signs of Bot Infestation
Horses that show no outward signs of illness can be severely infested, giving no clue to damage occurring inside. However, some horses do show signs of infestation, including an inflamed mouth area and stomach irritation. Infestation with bot larvae may cause ulcers in the stomach lining. If the infestation is severe, the opening from the stomach to the intestines may be blocked, which can cause irritation, ulcers and even colic. The burrowing larvae can cause small tears in the skin, which can become infected.
Treatment for Bots
Traditionally, horses are treated for bots in the fall, after a frost that kills the adult flies, and again in the spring, to rid the stomach of all the larvae. In the past, the treatment was worse than the disease, with extremely toxic chemicals given via stomach tube to the horse. Modern anthelmintics like Ivermectin, the active ingredient in Bimectin Paste 1.87%, are extremely effective and safe in the treatment of bots and have had an impact on lowering the number of bot flies in areas where good anthelmintic treatment is practiced.
Dr. David Ellefson, DVM, is Director of Technical Services at Bimeda. He is passionate about animal health and the ethical use of products; and a key element of his role is helping customers understand how a product is used most effectively. A former practicing veterinarian and practice owner, Dr Dave has a wealth of experience in animal health issues and a full understanding of the issues and concerns facing veterinarians and animal owners.
Bimectin is a global brand, delivering effective anti-parasitic treatments for cattle, sheep, pigs and horses around the world. In the USA, farmers, vets and horse owners have placed their trust in the quality Bimectin range for a number of years, and continue to do so. From a pour-on for cattle, to a de-wormer for horses, and an injection for cattle and pigs, you can be sure that the Bimectin range has the product for your needs.
What’s more, we also have excellent advice on best practice and disease control from our Bimeda Technical Service Veterinarian, Dr. Dave Ellefson, DVM.
Bimectin® (ivermectin) Pour-On contains 5 mg of ivermectin per ml and delivers effective, long-lasting control against a wide range of internal and external parasites in cattle, in one convenient low-volume application. Bimectin® Pour-On penetrates quickly to reach and kill parasites, and also offers long-activity against them. The Pour-On presentation facilitates ease of application and reduced stress on treated animals, and is also Beef Quality Assurance-friendly, since no injection is required.
Bimectin® Pour-On is well tolerated by breeding animals and is also available in five different package sizes, to meet a variety of producer needs. It is also FDA approved.
Bimectin® (ivermectin) Pour-On is indicated for the effective treatment and control of Gastrointestinal Roundworms, Lungworms, Cattle Grubs, Mites, Lice and Horn Flies. Bimectin® Pour-On is indicated for the treatment and control of the following specific parasites:
| Parasite | Stage |
|---|---|
| Gastrointestinal Roundworms | |
|
Ostertagia ostertagi (includign inhibited stage)
|
(Adults and L4) |
| Haemonchus placei | (Adults and L4) |
| Trichostrongylus axei | (Adults and L4) |
| T. colubriformis | (Adults and L4) |
| Cooperia oncophora | (Adults and L4) |
| Cooperia punctata | (Adults and L4) |
| Cooperia surnabada | (Adults and L4) |
| Strongyloides papillosus | (Adults) |
| Oesophagostomum radiatum | (Adults and L4) |
| Trichuris spp. | (Adults) |
| Lungworm | |
| Dictyocaulus viviparus | (Adults and L4) |
| Cattle Grubs | (Parasitic stages) |
| Hypoderma bovis | |
| H. lineatum | |
| Mites | |
| Sarcoptes scabiei var. bovis | |
| Lice | |
| Linognathus vituli | |
| Haematopinus eurysternus | |
| Damalinia bovis | |
| Solenopotes capillatus | |
| Horn Flies | |
| Haematobia irritans | |
A proven anthelmentic and boticide Bimectin contains 1.87% ivermectin, providing the broadest spectrum activity against parasites and bots. Apple flavored and scented for excellent palatability and ease of dosing. The calibrated syringe allows accurate dosing and the gel formulation facilitates absorption.
The product is safe to use in horses of all ages including mares at any stage of pregnancy.
Bimectin is indicated for the treatment of nematode or arthropod infestations in horses due to:
