stoicfish
Nov. 26, 2009, 08:17 PM
Due to the amount of worm threads, I thought a sticky might save some time.
I am not a vet or a professional relating to this subject, this is simply what I have learned from my personal research.
So as a result of having read about horse parasites from several different sources and still not being sure, I thought this might be a short cut for others. One of the problems in trying to come up with a worming program is the seemingly conflicting information. Many sites/information list the worming drugs intended use (what they should kill), and not the actual effectiveness. The difference being increasing resistance. I would encourage anyone trying to make up a worming plan not to ignore the issues associated with resistance, not just in accounting for widespread resistance but in creating your own. Once the worms on your farm, barn, horse are resistant they will be forever, and it is not difficult to create. Plus, there are not that many de-worming agents to switch too, in many cases there is only one or two effective drugs available to start with.
The four major drug classes with some product examples:
1. macrocyclic lactones (ivermectin -Zimecterin, Eqvalan and Equimectrin), (moxidectin-Quest, must be careful of doseage and not for horses under 6 months old)
2.benzimidazoles (fenbendazole-Panacur/Safe Guard), (oxibendazole-Anthelcide EQ)
3.tetrahydropyrimidines (pyrantel pamoate,-Strongid and Exodus), (pyrantel tartrate -Strongid C, Strongyle, Equi Aid)
4.prazino-isoquinolines (praziquantel -Zimecterin Gold and Equimax, this drug is mainly for tapeworms).
These are worms that are discussed the most, there are many others;
Large Strongyles (bloodworms or redworms)
benzimidazoles kills adults, Power Pak kills migrating stages
macrocyclic lactones both adult and migrating
tetrahydropyrimidines adults, some resistance
Small Strongyles (cyathostomes)
benzimidazoles -Power Pak for encysted larva only,
macrocyclic lactones -kills adults, moxidectin kills larva and adult
tetrahydropyrimidines -About 50% resistance reported
Ascarids (large roundworms)
Benzimidazoles-double dose (in foals and horses under 18 months)
macrocyclic lactones -resistance reported, used as a larvicidal
Neck Threadworms (Onchocerca cervicalis)
Ivermectin-kills the microfilariea
Double douse of Equimax, apparently kills the adults (if you have 10hrs read this http://www.chronofhorse.com/forum/showthread.php?t=155469&highlight=onchocerca )
Pinworms
benzimidazoles
macrocyclic lactones
tetrahydropyrimidines some resistance
Tapeworms
prazino-isoquinolines
Bots
macrocyclic lactones
Threadworms
Ivermectin -the mare 24 hrs after foaling. Or the foal in the first month. Most horses over the age of 6 months have a natural immunity.
So what I learned,
Only 20 to 30% of horses are very susceptible to worms. 70-80% of horses range from having moderate to high natural resistance to worms. Horses that have a high natural resistance to worms have a recommended twice a year worming program, spring and fall. Moderate, 3 times a year spring, fall and your prime worm season (winter in the south and summer in the north NA). For my horses, in Canada, I can use Zimecterin Gold in fall after the first freeze, Quest or Power Pak in spring and Ivermictin in mid summer, to cover everything. Small strongyles are the biggest concern due to their life cycle and their ability to cyst for up to 2 years in the horse. Large strongyles are easy to control or even eradicate and the rest are seasonal or are generally not a threat to an adult horse as well as being covered by the program.
Foals have different worming requirements till they are about 18 months old. This is one case where every 4 to 6 weeks is necessary. My area has an ascarid resistance to Ivermectin, as I read in The Horse, primarily due to 30 day programs. So to catch everything I must rotate Ivermectin and Panacur (Strongid is also has resistance due to the local TB industry and over worming).
To find out if your horses is naturally resistant do fecals. They are most effective in identifying small strongyles which are the hardest to control. Some areas are more prone to certain types of parasites then others.
Life Cycles and Effects (directly quoted from this http://www.drsfostersmith.com/pic/article.cfm?d=508&articleid=1602 page)
Large Strongyles (bloodworms or redworms)
Life Cycle: Start out as eggs, which hatch into larvae that are consumed by horses as they graze or drink infected water. The larvae mature in the intestinal tract. One type (Strongylus vulgaris or bloodworm) migrates into the blood vessels of the intestines. Their entire life cycle takes about 6 to 7 months. The other two types (Strongylus edentatus and Strongylus equines) migrate into the liver. Their entire life cycle takes about 8 to 11 months.
Effects: Heavy bloodworm infestation can cause severe or even fatal colic or blood vessel ruptures that lead to extensive blood loss. Other large strongyles cause less severe damage. Other signs include weight loss, anemia, or colic.
Small Strongyles
Life Cycle: Similar to large strongyles. Start out as eggs, develop into infective larvae which are ingested by the horse, and travel into the intestinal tract. However, instead of migrating into other body parts, small strongyle larvae burrow (or encyst in) the wall of the large colon. Here they can stay for months or years before the proper conditions trigger them to emerge. While encysted, small strongyles - which usually are the most damaging of internal parasites - are resistant to most dewormers
Effects: If large numbers of larvae emerge at once, they can cause severe health problems, including diarrhea, weakness, muscle wasting, and colic
Ascarids (large roundworms)
Life Cycle: Horses become infected with roundworms by swallowing the eggs in contaminated hay or water. In the stomach, the eggs develop into larvae which migrate to the liver and the heart and to the lungs, where they are coughed up and swallowed. Once back in the stomach, they develop into egg-laying adults. The life cycle takes about three months.
Effects: Most damage occurs as roundworms migrate through the body. They cause coughing, pneumonia, liver damage, diarrhea, and colic. Large numbers of adult roundworms can cause intestinal blockage or rupture. Other signs include unthriftiness, pot belly, rough hair coat, and slow growth
Threadworms
Life Cycle: Mostly a concern in foals, larvae are ingested in the mare's milk or by threadworm larvae present in the bedding, which can penetrate the foal's skin. The larvae migrate through the lungs and small intestine. The life cycle takes only about 2 weeks.
Effects: The main concern from threadworms is diarrhea.
Neck Threadworms (Onchocerca cervicalis)
Life Cycle: The adult worms of this parasite live in the nuchal ligament, a very thick, elastic ligament that runs along the horse's neck between the withers and the poll. Larvae from these adults migrate to the skin. The larvae are eventually ingested by insects, especially the Culicoides gnat.
Effects: Larvae burrowed into the skin can cause inflammation so intense that some horses will scratch and roll until the skin is red and the hair is rubbed off. Usually the irritation is in the skin of the forelegs, chest, eyelids, and withers, and along the middle of the belly.
Pinworms
Life Cycle: Female pinworms lay their eggs in the skin around the horse's anus where they are often rubbed off onto the ground. They are then eaten by a horse and the life cycle repeats.
Effects: The egg masses are extremely itchy. Horses with pinworm infections will sometimes rub their tails until all the hair is pulled off. Adult pinworms (about 1-3/4 inches long) may be seen around the anal area, along with a clear discharge (the egg masses). Most adult horses do not have issue with pinworms.
Tapeworms
Life Cycle: Similar to tapeworms in dogs, cats, and humans, equine tapeworms require an intermediate host to mature. Tapeworm eggs are ingested by a tiny mite called the orabatid mite that lives on the grass in pastures. Horses ingest the mites (and the tapeworm eggs inside the mites) while they graze. Inside the horse, the tapeworm eggs mature in 6-10 weeks into adult tapeworms that attach to the intestinal lining, where they absorb nutrients. Packets of eggs break off from the tapeworm and are passed out in the horse's feces, where they are ingested by pasture mites and the cycle starts again
Effects: Tapeworm infestations can lead to colic, rough hair coat, slow growth, and other conditions due to nutrient deficiencies. In addition, heavy tapeworm infestation is considered to be a significant cause of colic.
Bots
Life Cycle: Adult bot flies deposit their eggs on horses' forelegs and shoulders, or around the jaws and lips. When the larvae hatch, they move into the mouth where they burrow into the tissues of the gums and the tongue to develop further. Eventually, they move into the tissues of the stomach and intestines, where they live for up to 12 months before passing out of the horse in the manure and developing into adult bot flies in the soil. However, cold weather kills bot flies.
Effects: Although bots can cause damage to the tissue of the horse's mouth and intestinal tract, most horses do not show signs of serious diseases from bots. However, very large numbers of bots have been associated with gastric ulcers.
Sources:
http://www.avma.org/animal_health/brochures/internal_parasites/horses/parasites_brochure.pdf General worm article - American Veterinary Medical Association
http://www.ag.ndsu.edu/pubs/ansci/horse/v543.pdf General worm article – North Dakota State University
http://www.thehorse.com/ViewArticle.aspx?ID=1621 Age-Related Parasites: Scourges of Foals and Young Horses
http://www.alphahorse.com/horse-wormers.html Horse Wormers – Alpha Horse
http://www.thehorse.com/ViewArticle.aspx?ID=14719 Choosing Wormers – The Horse
http://www.thehorse.com/ViewArticle.aspx?ID=15206 Parasite Resistance: 10 Things to Remember– The Horse
http://www.thehorse.com/ViewArticle.aspx?ID=13969 and
http://www.thehorse.com/ViewArticle.aspx?ID=14011 Resistance article – The Horse
http://www.thehorse.com/ViewArticle.aspx?ID=6064 Principles of Deworming
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TD7-4JX37BS-2&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1106217909&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=3124f7e0e3cb5c2f389bcd5a7bd4c8bb Small Strongyle resistance in Canada
http://www.equinescienceupdate.co.uk/worms3.htm Cyathostomes resistant to benzimidazoles and in some cases pyrantel
http://diss-epsilon.slu.se/archive/00000799/01/Avh_29.till_Epsilon.pdf
Doc thesis on Strongyle
http://www.extension.org/pages/Strongyloides_(Threadworm)_in_horses Thread worms
http://www.thehorse.com/parasites/parasites0304.pdf Ascarids –The Horse article
http://www.montanaequine.com/docs/news_08_07.doc Ascarid article
The Horse Webinars (Highly recommend the first one)
http://www.thehorse.com/Video.aspx?vID=183 Deworming Your Horse
http://www.thehorse.com/Video.aspx?vID=18 Strategic Deworming
http://www.foalcare.com/calendar.aspx foal care calendar generator
I am not a vet or a professional relating to this subject, this is simply what I have learned from my personal research.
So as a result of having read about horse parasites from several different sources and still not being sure, I thought this might be a short cut for others. One of the problems in trying to come up with a worming program is the seemingly conflicting information. Many sites/information list the worming drugs intended use (what they should kill), and not the actual effectiveness. The difference being increasing resistance. I would encourage anyone trying to make up a worming plan not to ignore the issues associated with resistance, not just in accounting for widespread resistance but in creating your own. Once the worms on your farm, barn, horse are resistant they will be forever, and it is not difficult to create. Plus, there are not that many de-worming agents to switch too, in many cases there is only one or two effective drugs available to start with.
The four major drug classes with some product examples:
1. macrocyclic lactones (ivermectin -Zimecterin, Eqvalan and Equimectrin), (moxidectin-Quest, must be careful of doseage and not for horses under 6 months old)
2.benzimidazoles (fenbendazole-Panacur/Safe Guard), (oxibendazole-Anthelcide EQ)
3.tetrahydropyrimidines (pyrantel pamoate,-Strongid and Exodus), (pyrantel tartrate -Strongid C, Strongyle, Equi Aid)
4.prazino-isoquinolines (praziquantel -Zimecterin Gold and Equimax, this drug is mainly for tapeworms).
These are worms that are discussed the most, there are many others;
Large Strongyles (bloodworms or redworms)
benzimidazoles kills adults, Power Pak kills migrating stages
macrocyclic lactones both adult and migrating
tetrahydropyrimidines adults, some resistance
Small Strongyles (cyathostomes)
benzimidazoles -Power Pak for encysted larva only,
macrocyclic lactones -kills adults, moxidectin kills larva and adult
tetrahydropyrimidines -About 50% resistance reported
Ascarids (large roundworms)
Benzimidazoles-double dose (in foals and horses under 18 months)
macrocyclic lactones -resistance reported, used as a larvicidal
Neck Threadworms (Onchocerca cervicalis)
Ivermectin-kills the microfilariea
Double douse of Equimax, apparently kills the adults (if you have 10hrs read this http://www.chronofhorse.com/forum/showthread.php?t=155469&highlight=onchocerca )
Pinworms
benzimidazoles
macrocyclic lactones
tetrahydropyrimidines some resistance
Tapeworms
prazino-isoquinolines
Bots
macrocyclic lactones
Threadworms
Ivermectin -the mare 24 hrs after foaling. Or the foal in the first month. Most horses over the age of 6 months have a natural immunity.
So what I learned,
Only 20 to 30% of horses are very susceptible to worms. 70-80% of horses range from having moderate to high natural resistance to worms. Horses that have a high natural resistance to worms have a recommended twice a year worming program, spring and fall. Moderate, 3 times a year spring, fall and your prime worm season (winter in the south and summer in the north NA). For my horses, in Canada, I can use Zimecterin Gold in fall after the first freeze, Quest or Power Pak in spring and Ivermictin in mid summer, to cover everything. Small strongyles are the biggest concern due to their life cycle and their ability to cyst for up to 2 years in the horse. Large strongyles are easy to control or even eradicate and the rest are seasonal or are generally not a threat to an adult horse as well as being covered by the program.
Foals have different worming requirements till they are about 18 months old. This is one case where every 4 to 6 weeks is necessary. My area has an ascarid resistance to Ivermectin, as I read in The Horse, primarily due to 30 day programs. So to catch everything I must rotate Ivermectin and Panacur (Strongid is also has resistance due to the local TB industry and over worming).
To find out if your horses is naturally resistant do fecals. They are most effective in identifying small strongyles which are the hardest to control. Some areas are more prone to certain types of parasites then others.
Life Cycles and Effects (directly quoted from this http://www.drsfostersmith.com/pic/article.cfm?d=508&articleid=1602 page)
Large Strongyles (bloodworms or redworms)
Life Cycle: Start out as eggs, which hatch into larvae that are consumed by horses as they graze or drink infected water. The larvae mature in the intestinal tract. One type (Strongylus vulgaris or bloodworm) migrates into the blood vessels of the intestines. Their entire life cycle takes about 6 to 7 months. The other two types (Strongylus edentatus and Strongylus equines) migrate into the liver. Their entire life cycle takes about 8 to 11 months.
Effects: Heavy bloodworm infestation can cause severe or even fatal colic or blood vessel ruptures that lead to extensive blood loss. Other large strongyles cause less severe damage. Other signs include weight loss, anemia, or colic.
Small Strongyles
Life Cycle: Similar to large strongyles. Start out as eggs, develop into infective larvae which are ingested by the horse, and travel into the intestinal tract. However, instead of migrating into other body parts, small strongyle larvae burrow (or encyst in) the wall of the large colon. Here they can stay for months or years before the proper conditions trigger them to emerge. While encysted, small strongyles - which usually are the most damaging of internal parasites - are resistant to most dewormers
Effects: If large numbers of larvae emerge at once, they can cause severe health problems, including diarrhea, weakness, muscle wasting, and colic
Ascarids (large roundworms)
Life Cycle: Horses become infected with roundworms by swallowing the eggs in contaminated hay or water. In the stomach, the eggs develop into larvae which migrate to the liver and the heart and to the lungs, where they are coughed up and swallowed. Once back in the stomach, they develop into egg-laying adults. The life cycle takes about three months.
Effects: Most damage occurs as roundworms migrate through the body. They cause coughing, pneumonia, liver damage, diarrhea, and colic. Large numbers of adult roundworms can cause intestinal blockage or rupture. Other signs include unthriftiness, pot belly, rough hair coat, and slow growth
Threadworms
Life Cycle: Mostly a concern in foals, larvae are ingested in the mare's milk or by threadworm larvae present in the bedding, which can penetrate the foal's skin. The larvae migrate through the lungs and small intestine. The life cycle takes only about 2 weeks.
Effects: The main concern from threadworms is diarrhea.
Neck Threadworms (Onchocerca cervicalis)
Life Cycle: The adult worms of this parasite live in the nuchal ligament, a very thick, elastic ligament that runs along the horse's neck between the withers and the poll. Larvae from these adults migrate to the skin. The larvae are eventually ingested by insects, especially the Culicoides gnat.
Effects: Larvae burrowed into the skin can cause inflammation so intense that some horses will scratch and roll until the skin is red and the hair is rubbed off. Usually the irritation is in the skin of the forelegs, chest, eyelids, and withers, and along the middle of the belly.
Pinworms
Life Cycle: Female pinworms lay their eggs in the skin around the horse's anus where they are often rubbed off onto the ground. They are then eaten by a horse and the life cycle repeats.
Effects: The egg masses are extremely itchy. Horses with pinworm infections will sometimes rub their tails until all the hair is pulled off. Adult pinworms (about 1-3/4 inches long) may be seen around the anal area, along with a clear discharge (the egg masses). Most adult horses do not have issue with pinworms.
Tapeworms
Life Cycle: Similar to tapeworms in dogs, cats, and humans, equine tapeworms require an intermediate host to mature. Tapeworm eggs are ingested by a tiny mite called the orabatid mite that lives on the grass in pastures. Horses ingest the mites (and the tapeworm eggs inside the mites) while they graze. Inside the horse, the tapeworm eggs mature in 6-10 weeks into adult tapeworms that attach to the intestinal lining, where they absorb nutrients. Packets of eggs break off from the tapeworm and are passed out in the horse's feces, where they are ingested by pasture mites and the cycle starts again
Effects: Tapeworm infestations can lead to colic, rough hair coat, slow growth, and other conditions due to nutrient deficiencies. In addition, heavy tapeworm infestation is considered to be a significant cause of colic.
Bots
Life Cycle: Adult bot flies deposit their eggs on horses' forelegs and shoulders, or around the jaws and lips. When the larvae hatch, they move into the mouth where they burrow into the tissues of the gums and the tongue to develop further. Eventually, they move into the tissues of the stomach and intestines, where they live for up to 12 months before passing out of the horse in the manure and developing into adult bot flies in the soil. However, cold weather kills bot flies.
Effects: Although bots can cause damage to the tissue of the horse's mouth and intestinal tract, most horses do not show signs of serious diseases from bots. However, very large numbers of bots have been associated with gastric ulcers.
Sources:
http://www.avma.org/animal_health/brochures/internal_parasites/horses/parasites_brochure.pdf General worm article - American Veterinary Medical Association
http://www.ag.ndsu.edu/pubs/ansci/horse/v543.pdf General worm article – North Dakota State University
http://www.thehorse.com/ViewArticle.aspx?ID=1621 Age-Related Parasites: Scourges of Foals and Young Horses
http://www.alphahorse.com/horse-wormers.html Horse Wormers – Alpha Horse
http://www.thehorse.com/ViewArticle.aspx?ID=14719 Choosing Wormers – The Horse
http://www.thehorse.com/ViewArticle.aspx?ID=15206 Parasite Resistance: 10 Things to Remember– The Horse
http://www.thehorse.com/ViewArticle.aspx?ID=13969 and
http://www.thehorse.com/ViewArticle.aspx?ID=14011 Resistance article – The Horse
http://www.thehorse.com/ViewArticle.aspx?ID=6064 Principles of Deworming
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TD7-4JX37BS-2&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1106217909&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=3124f7e0e3cb5c2f389bcd5a7bd4c8bb Small Strongyle resistance in Canada
http://www.equinescienceupdate.co.uk/worms3.htm Cyathostomes resistant to benzimidazoles and in some cases pyrantel
http://diss-epsilon.slu.se/archive/00000799/01/Avh_29.till_Epsilon.pdf
Doc thesis on Strongyle
http://www.extension.org/pages/Strongyloides_(Threadworm)_in_horses Thread worms
http://www.thehorse.com/parasites/parasites0304.pdf Ascarids –The Horse article
http://www.montanaequine.com/docs/news_08_07.doc Ascarid article
The Horse Webinars (Highly recommend the first one)
http://www.thehorse.com/Video.aspx?vID=183 Deworming Your Horse
http://www.thehorse.com/Video.aspx?vID=18 Strategic Deworming
http://www.foalcare.com/calendar.aspx foal care calendar generator