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Equine Parasites. General Considerations Parasites are most successfully prevented through a combination of management and therapeutic strategies Parasites.

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Presentation on theme: "Equine Parasites. General Considerations Parasites are most successfully prevented through a combination of management and therapeutic strategies Parasites."— Presentation transcript:

1 Equine Parasites

2 General Considerations Parasites are most successfully prevented through a combination of management and therapeutic strategies Parasites are most successfully prevented through a combination of management and therapeutic strategies Management Management Decrease parasite burden in environment Decrease parasite burden in environment Therapeutic Therapeutic Deworming with proper product at proper intervals Deworming with proper product at proper intervals

3 Parasite Prevention Adequate pasture acreage Adequate pasture acreage Compost manure Compost manure Cleanliness Cleanliness Pasture rotation Pasture rotation Mixed grazing (cattle and horses) Mixed grazing (cattle and horses)

4 Pasture Rotation Infective larvae on pasture decreases greatly over the winter and also in hot, humid days of summer Infective larvae on pasture decreases greatly over the winter and also in hot, humid days of summer Move horses from old, infested pastures to ones that have minimal numbers of infective larvae Move horses from old, infested pastures to ones that have minimal numbers of infective larvae Deworm prior to moving Deworm prior to moving Foals and young horses should go to cleanest available pastures Foals and young horses should go to cleanest available pastures

5 Internal parasites The amount of clinical disease a horse will show depends on three factors: The amount of clinical disease a horse will show depends on three factors: 1. Type of parasite involved 2. Number of parasites involved 3. Host defenses. Young and debilitated animals more susceptible

6 Life Cycle of Parasites Eggs Eggs Larvae (immature worms) Larvae (immature worms) Adults (mature worms) Adults (mature worms)

7 Life cycle of the parasite Eggs or larvae are deposited on the ground in the manure of infected horse Eggs or larvae are deposited on the ground in the manure of infected horse The eggs and larvae develop in the environment and are swallowed while the horse is grazing The eggs and larvae develop in the environment and are swallowed while the horse is grazing Larvae mature in the horse’s digestive tract where most of them become egg laying adults. Larvae mature in the horse’s digestive tract where most of them become egg laying adults.

8 Internal parasites – Common signs Poor growth Poor growth Weight loss Weight loss Decreased feed efficiency Decreased feed efficiency Colic Colic Diarrhea Diarrhea Pneumonia Pneumonia Death Death

9 Dull hair coat

10 Clinical sign – colic

11 Poor performance

12 Important Parasites in the horse Large strongyle (Stongylus vulgaris, S.edentatus, S.equinus) Large strongyle (Stongylus vulgaris, S.edentatus, S.equinus) Small strongyle (Cyathostemes) Small strongyle (Cyathostemes) Round worm (Ascarids) Round worm (Ascarids) Bots (Gastrophilus spp) Bots (Gastrophilus spp) Pin worms (Oxyuris equi) Pin worms (Oxyuris equi) Tapeworms (Anoplochephala) Tapeworms (Anoplochephala) Threadworm (Strongyloides) Threadworm (Strongyloides)

13 Large Strongyle Strongylus vulgaris Blood worm- bloodsucking of the large instestine Blood worm- bloodsucking of the large instestine Most dangerous parasite of horses Most dangerous parasite of horses Causes thromboembolic colic, various degrees of anemia. Causes thromboembolic colic, various degrees of anemia. Direct life cycle Direct life cycle Larvae live in artery supplying blood to the intestines. Blood clots form which block blood supply to the intestine Larvae live in artery supplying blood to the intestines. Blood clots form which block blood supply to the intestine

14 First stage is the egg in feces or soil, molts to 2 nd stage in feces or soil. 3 rd stage becomes “sheathed” or sticks to walls, buckets, etc. First stage is the egg in feces or soil, molts to 2 nd stage in feces or soil. 3 rd stage becomes “sheathed” or sticks to walls, buckets, etc. When ingested by the horse the infective 3 rd stage larvae of S.vulgaris cast off there sheath in the lumen of the s. intestine and enter the wall of the cecum and ventral colon. They curl up under the mucous membrane and prepare to molt. After 8 days the molt is complete and become a 4 th stage larva and resume migration. When ingested by the horse the infective 3 rd stage larvae of S.vulgaris cast off there sheath in the lumen of the s. intestine and enter the wall of the cecum and ventral colon. They curl up under the mucous membrane and prepare to molt. After 8 days the molt is complete and become a 4 th stage larva and resume migration.

15 4 th stage penetrate nearby small arterioles and wanders to the cranial mesenteric artery, which supplies blood to the instestine. (this leaves a path of inflammation, which can lead to thrombosis or occlude the vessel) After 2-4 months they enter the surrounding tissue of the intestinal wall and a final molt takes place and the immature adults (5 th stage) enter the lumen of the cecum and ventral colon, mature and reproduce 6 months after original ingestion 4 th stage penetrate nearby small arterioles and wanders to the cranial mesenteric artery, which supplies blood to the instestine. (this leaves a path of inflammation, which can lead to thrombosis or occlude the vessel) After 2-4 months they enter the surrounding tissue of the intestinal wall and a final molt takes place and the immature adults (5 th stage) enter the lumen of the cecum and ventral colon, mature and reproduce 6 months after original ingestion Collateral circulation Collateral circulation

16 Life Cycle

17 Adult large strongyle

18 Strongylus vulgaris,adults in equine intestine “bloodworms”

19 After deworming “red worms”

20 This verminous arteritis lesion is from the cranial mesenteric artery of a weanling Quarter Horse colt. Verminous arteritis is caused by the migration of larvae of Strongylus vulgaris through the blood vessels. It was once a common cause of colic and death in domestic horses. This verminous arteritis lesion is from the cranial mesenteric artery of a weanling Quarter Horse colt. Verminous arteritis is caused by the migration of larvae of Strongylus vulgaris through the blood vessels. It was once a common cause of colic and death in domestic horses.

21 S.edentatus, S. equinus 2 times as large as adults 2 times as large as adults The 3 rd stage of S. edentatus migrate to the liver, become encapsulated and molt to the 4 th stage in approx. 2 weeks. After molting the larvae wander aimlessly in the liver for 2 months, leave the liver by ligaments that hold the liver in position, wander for months in the connective tissues, and 11 months (PPP) after ingestion can be found in the lining of the cecum and colon. The 3 rd stage of S. edentatus migrate to the liver, become encapsulated and molt to the 4 th stage in approx. 2 weeks. After molting the larvae wander aimlessly in the liver for 2 months, leave the liver by ligaments that hold the liver in position, wander for months in the connective tissues, and 11 months (PPP) after ingestion can be found in the lining of the cecum and colon.

22 3 rd stage S.equinus encyst and undergo molt in the wall of the large intestine. After molting they bore into the right half of the liver which lies in contact with this portion of the large intestine. They stay for 6-7 weeks, enter the pancreas and abdominal cavity where the complete their development to adults. Reenter the lumen of the large intestine and mate. (9mo. PPP) 3 rd stage S.equinus encyst and undergo molt in the wall of the large intestine. After molting they bore into the right half of the liver which lies in contact with this portion of the large intestine. They stay for 6-7 weeks, enter the pancreas and abdominal cavity where the complete their development to adults. Reenter the lumen of the large intestine and mate. (9mo. PPP)

23 Large and small strongyle

24 Diagnosis Diagnosis of mixed strongyle infection is based on demonstration of eggs in the feces. Specific diagnosis can be made by identifying the infective larvae after fecal Diagnosis of mixed strongyle infection is based on demonstration of eggs in the feces. Specific diagnosis can be made by identifying the infective larvae after fecal

25 Large Strongyles Treat every 6 months Treat every 6 months Use Ivermectin or monoxidecin Use Ivermectin or monoxidecin

26 Small Strongyle- Cyathostominae Numerous species of strongyles (40) Numerous species of strongyles (40) Direct Life cycle Direct Life cycle Larvae life in gut wall of large intestine- therefore not as pathogenic as large stongyle Larvae life in gut wall of large intestine- therefore not as pathogenic as large stongyle Cause damage to gut wall resulting in G.I. upset, and severe diarrhea. Cause damage to gut wall resulting in G.I. upset, and severe diarrhea. Internal parasites of highest concern- encysted stage is not affected by dewormers Internal parasites of highest concern- encysted stage is not affected by dewormers Very short life cycle 4 to 6 weeks Very short life cycle 4 to 6 weeks

27 Life Cycle

28 Symptoms Colic Colic Diarrhea Diarrhea Ill-thrift, loss of body condition Ill-thrift, loss of body condition Subclinical diseases is more common and may result in greater economic losses Subclinical diseases is more common and may result in greater economic losses

29 Diagnosis of Strongyles Fecal flotation- small and Fecal flotation- small and large stongyles look similar on float. Assume the worst and treat for large Necropsy Necropsy

30 Encysted cyathostome larvae in the large colon of a horse. Encysted cyathostome larvae in the large colon of a horse.

31 Treatment Many products available – nearly all horse wormers are effective against adults in the GI tract Many products available – nearly all horse wormers are effective against adults in the GI tract Ivermectin, mixodectin, and fenbendazole effective against migrating larvae Ivermectin, mixodectin, and fenbendazole effective against migrating larvae Check fecal samples for eggs to gauge success of worming program Check fecal samples for eggs to gauge success of worming program

32 Control of strongyles Use effective wormers routinely Use effective wormers routinely Avoid overgrazing pasture Avoid overgrazing pasture Use clean pastures for young animals Use clean pastures for young animals Pile and compost manure Pile and compost manure *No public health significance

33 Pinworms Oxyuris equi Adult pinworms lay eggs around the anus Adult pinworms lay eggs around the anus Direct lifecycle Direct lifecycle Eggs cause irritation and horses will rub their tails against objects Eggs cause irritation and horses will rub their tails against objects Bare patches around the tail and perineum- pruritus ani Bare patches around the tail and perineum- pruritus ani Vague signs of abdominal discomfort if any Vague signs of abdominal discomfort if any Controlled by most wormers Controlled by most wormers

34 Life Cycle

35 Pinworms

36 Diagnosis of Pin Worms Egg masses in perineal region Egg masses in perineal region Tail rubbing Tail rubbing Eggs in feces (rare) Eggs in feces (rare) Adults in feces Adults in feces

37 Pinworms usually are the cause of the irritation that leads to tail rubbing. Adult females deposit adhesive egg masses on anal and perianal skin. Note the broken hair at the base of the tail. Pinworms usually are the cause of the irritation that leads to tail rubbing. Adult females deposit adhesive egg masses on anal and perianal skin. Note the broken hair at the base of the tail.

38 Adults in feces

39 Control of Pin Worms Thorough cleaning of stalls Thorough cleaning of stalls Fresh food and water Fresh food and water

40 Stomach bots Gastrophilus ssp Insects – the adult is a fly, the larvae live in the horse’s stomach Insects – the adult is a fly, the larvae live in the horse’s stomach Flies lay eggs on hair, they hatch and penetrate into the mouth tissue, then migrate to stomach Flies lay eggs on hair, they hatch and penetrate into the mouth tissue, then migrate to stomach May cause stomach irritation and colic May cause stomach irritation and colic G. nasalis, G. hemorrhoidalis, G. intestinalis G. nasalis, G. hemorrhoidalis, G. intestinalis

41 Life Cycle

42 Bot fly and egg

43 Bot fly larvae Migrate thru the tongue and esophagus after they are ingested, and attach themselves to the lining of the stomach, where they stay for up to 11 months. In large numbers, they contribute to gastric (stomach) ulcers and occasionally rupture of the stomach. Migrate thru the tongue and esophagus after they are ingested, and attach themselves to the lining of the stomach, where they stay for up to 11 months. In large numbers, they contribute to gastric (stomach) ulcers and occasionally rupture of the stomach.

44 gross lesion with adult worms, equine stomach

45 Mutual grooming leads to the ingestion of bot eggs by horses Mutual grooming leads to the ingestion of bot eggs by horses

46 Diagnosis of Bots See eggs on hair and mane See eggs on hair and mane Endoscopy of stomach Endoscopy of stomach Necropsy Necropsy Knowing flies are in area Knowing flies are in area

47 Treatment of Bots Because flies are insects, only wormers that are effective against insects will kill bots Because flies are insects, only wormers that are effective against insects will kill bots Ivermectin and moxidectin are effective Ivermectin and moxidectin are effective Nits can be removed from hair before they hatch Nits can be removed from hair before they hatch Nit removal combs, pumice stones Nit removal combs, pumice stones Warm water with insecticide added Warm water with insecticide added

48 Public health significance Flies can lay eggs on human hair Flies can lay eggs on human hair Larvae will hatch and burrow into skin Larvae will hatch and burrow into skin

49 The stomach worms Habronema muscae H microstoma, and Draschia megastoma The adults are 6-25 mm in size. Draschia are found in tumor-like swellings in the stomach wall. The adults are 6-25 mm in size. Draschia are found in tumor-like swellings in the stomach wall. The eggs or larvae are ingested by larvae of house or stable flies, which serve as intermediate hosts. Horses are infected by ingesting flies that contain infective larvae or by free larvae that emerge from flies as they feed around the lips The eggs or larvae are ingested by larvae of house or stable flies, which serve as intermediate hosts. Horses are infected by ingesting flies that contain infective larvae or by free larvae that emerge from flies as they feed around the lips

50 Habronema If the larvae which are in the mouthparts of the immediate host are deposited in the open skin well the fly feeds it can cause summer sores. If the larvae which are in the mouthparts of the immediate host are deposited in the open skin well the fly feeds it can cause summer sores. Summer sores are ulcerated irritations. These lesions can cause soreness and itchiness and become covered in a reddish-yellow tissue Summer sores are ulcerated irritations. These lesions can cause soreness and itchiness and become covered in a reddish-yellow tissue If the worms get deposited into the eye or the area around the eye it can cause a persistent case of conjunctivitis. If the worms get deposited into the eye or the area around the eye it can cause a persistent case of conjunctivitis.

51 Cycle

52 Lesions

53 Ascarids - Roundworms Parascaris equorum Parascaris equorum Most common in foals/young horses –can cause impactation and colic Most common in foals/young horses –can cause impactation and colic Interfere with digestion and absorption of nutrients, notably protein Interfere with digestion and absorption of nutrients, notably protein Cause telescoping of intestine in foals Cause telescoping of intestine in foals Direct life cycle Direct life cycle Larvae migrate through lungs where they can cause pneumonia Larvae migrate through lungs where they can cause pneumonia Build up in large numbers in the anterior part of the small intestine Build up in large numbers in the anterior part of the small intestine

54 Parascaris equoru m 1 celled egg in feces (1-2 weeks) Infective eggs are swallowed, they hatch and liberate infective 2 nd stage larvae, which burrow into the wall of the small intestine and are carried to the liver by the portal vein. After migrating through the liver tissue, they enter the hepatic vein and are carried by the posterior vena cava to the lungs, where they break the into the alveoli, molt and are coughed up and swallowed, returning to the small intestine to mature. (3months) Eggs have proteinaceous layer and is sticky. Eggs adhere to stall walls, mangers, buckets, etc.

55 Life Cycle

56 Ascarid Can grow up to 12 inches in length within 4 weeks and block the small intestines. Can grow up to 12 inches in length within 4 weeks and block the small intestines.

57 Ascarids – Clinical Signs Impaction colic – death Impaction colic – death Pneumonia Pneumonia Pot belly Pot belly Unthrifty appearance Unthrifty appearance Poor hair coat Poor hair coat

58 Spaghetti for dinner??

59 Ascarid impactation and rupture

60 Parascaris equorum

61 Ascarid in the bile system of the liver

62 Diagnosis of ascarids Clinical signs Clinical signs Fecal flotation Fecal flotation Necropsy Necropsy

63 Control of Ascarids Good sanitation Good sanitation Eggs live in environment for many years Eggs live in environment for many years Avoid putting foals in same pastures year after year Avoid putting foals in same pastures year after year Regular worming of foals and young stock Regular worming of foals and young stock

64 Treatment of Ascarids Most common wormers are effective against ascarids (Safeguard, Panacur, Strongid, Ivermectin) Most common wormers are effective against ascarids (Safeguard, Panacur, Strongid, Ivermectin) If a foal has a very heavy infection it should be wormed with less effective products to prevent impaction If a foal has a very heavy infection it should be wormed with less effective products to prevent impaction

65 Tapeworms Three species of tapeworms are found in horses: Anoplocephala magna, A perfoliata, and Paranoplocephala mamillana Three species of tapeworms are found in horses: Anoplocephala magna, A perfoliata, and Paranoplocephala mamillana Found mostly in the cecum but may also be in the small intestine. Found mostly in the cecum but may also be in the small intestine. Young and older horses more susceptible -mite Young and older horses more susceptible -mite Difficult to detect on fecal exam. Difficult to detect on fecal exam.

66 Tape worms (Anaplocephala) Cause colic Cause colic Live at ileo-cecal valve Live at ileo-cecal valve Disrupt motility Disrupt motility Use prazinquantel Use prazinquantel

67 Difucult to detect the eggs on fecal sample Difucult to detect the eggs on fecal sample

68 Infection of A. perfoliata with intussusception of the ileum into the cecum.

69 A cluster of tapeworm segments at the ileocecal valve are of the cecum of a naturally infected horse.

70 Thread worms Intestinal Threadworm Strongyloides westeri – (strongyle-like) Strongyloides westeri – (strongyle-like) Life cycle as short at 2 weeks Life cycle as short at 2 weeks Infects young foals (2 weeks-6 months) Infects young foals (2 weeks-6 months) Larvae passed in mare’s milk to foals Larvae passed in mare’s milk to foals May cause diarrhea in young foals May cause diarrhea in young foals Immunity quickly developed Immunity quickly developed DOES NOT cause foal heat diarrhea DOES NOT cause foal heat diarrhea Strongyloides is zoonotic, cutaneous larva migraines, but not this species Strongyloides is zoonotic, cutaneous larva migraines, but not this species

71 Thread worms

72 Can be free living in the soil

73 Cutaneous larva migrans Larva can penetrate foal’s skin to cause infection Larva can penetrate foal’s skin to cause infection May species penetrate human skin and cause problems in people as well May species penetrate human skin and cause problems in people as well

74 Diagnosis of Strongyloides Fecal exam for larvae Fecal exam for larvae Fecal culture Fecal culture VERY rarely may see eggs VERY rarely may see eggs

75 Stronglyoides egg (larvae moving)

76 Treatment of Strongyloides Worm mare prior to foaling to prevent larval migration to udder Worm mare prior to foaling to prevent larval migration to udder Worm foals at 4 weeks of age Worm foals at 4 weeks of age

77 Control of Strongyloides Sanitation Sanitation Keep stall dry to kill larvae Keep stall dry to kill larvae

78 Diagnosis of internal parasites Fecal egg counts can be very helpful Fecal egg counts can be very helpful negative fecal does not always mean no parasites Monitor multiple horses on the farm at the same time Monitor multiple horses on the farm at the same time Some parasites are difficult to diagnose – tapeworms Some parasites are difficult to diagnose – tapeworms Smear, float, centrifuge, and Baermann apparatus

79 Baermann apparatus Lung worms Lung worms

80 Dewormers None are 100% effective None are 100% effective 2 month interval (6 times a year) *think life cycles* 2 month interval (6 times a year) *think life cycles* Use a broad spectrum product as basis for control (ivermectin, moxidectin) Use a broad spectrum product as basis for control (ivermectin, moxidectin) Be sure to treat for tapeworms 1-2 time per year Be sure to treat for tapeworms 1-2 time per year Avoid creating resistance to anthelmintics Avoid creating resistance to anthelmintics *Double dose strongid *Product containing prazinquantel

81 Dewormers Avermectins Avermectins Ivermectin (Eqvalan, Zimectin, Equimectrin Moxidectin (Quest) Tetrahydropyrimidines Tetrahydropyrimidines Pyrantal (Strongid, Rotation0 Benzimidazoles Benzimidazoles Febendazole (Panacur, Safeguard) Prazinquantel Prazinquantel

82 Parasite control Manure removal at least 2x/week Manure removal at least 2x/week Spread manure in hot weather away from fields where horses are grazing Spread manure in hot weather away from fields where horses are grazing Rotate Pasture- limit overgrazing (different species) Rotate Pasture- limit overgrazing (different species) Group horses by age Group horses by age Use feeder for hay and grain Use feeder for hay and grain Remove bot eggs from hair Remove bot eggs from hair Deworm new arrivals Deworm new arrivals

83 Questions ?? CTVT pages 473-475, 488-504 CTVT pages 473-475, 488-504 LACP pages 329-330 LACP pages 329-330


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