Equine Helminths Quiz

Classification of Equine Parasites

• Draschia megastoma, Habronema muscae, and Habronema microstoma are nematodes classified under the order Spirurida, commonly known as equine stomach worms.
• Strongyloides westeri is a nematode under the order Rhabditida, referred to as the equine threadworm.
• Parascaris equorum is a large roundworm classified under the order Ascaridida, known as the equine ascarid or large roundworm.
• Strongylus spp. are nematodes in the order Strongylida, known as large strongyles or bloodworms.
• Oxyuris equi is classified as a nematode under the order Oxyurida, commonly called the equine pinworm.
• Small strongyles, or cyathostomins, belong to the superfamily Strongyloidea and order Strongylida, consisting of over 40 species.
• Anoplocephala perfoliata is a cestode (tapeworm) in the order Cyclophyllidea and family Anoplocephalidae, being the most common tapeworm in horses.

Prevalence and Clinical Impact

• Habronema muscae is the most prevalent equine stomach worm, while Draschia megastoma causes the most severe lesions, including large nodules filled with necrotic material in the stomach.

Life Cycle of Stomach Worms

• The life cycle of Draschia megastoma, Habronema muscae, and Habronema microstoma is indirect, with flies as the intermediate host.
• Adult worms in the horse's stomach release eggs or L1 larvae, which are ingested by flies, developing into infective L3 larvae.
• If ingested by the horse, L3 larvae mature into adults; if deposited on wounds, they cause summer sores but do not mature into adults.
• The prepatent period for these worms is approximately two months.

Clinical presentations of Stomach Worm Infections

• Most horses ingesting L3 larvae remain asymptomatic; however, heavy infections can lead to gastritis.
• Draschia megastoma can cause severe lesions with nodules up to 10 cm in diameter, potentially leading to fatal complications.
• Cutaneous habronemiasis occurs when L3 larvae are deposited on wounds, causing reddish-brown, itchy lesions known as summer sores.

Diagnosis and Treatment of Stomach Worms

• Diagnosis is challenging; routine fecal flotation often misses eggs, necessitating alternative methods like gastroscopy or necropsy.
• Anthelmintics like moxidectin are used for treatment; surgical intervention may be necessary for severe summer sores.
• Accordingly, fly management is crucial to decrease exposure to larvae.

Classification and Life Cycle of Strongyloides westeri

• Strongyloides westeri’s life cycle is direct, alternating between parasitic and free-living forms, with parasitic females in hosts.
• Infective L3 larvae can penetrate skin or be ingested, affecting the small intestine, or be transmitted through mare's milk to foals.

Clinical Presentation of Strongyloides westeri

• Affects primarily foals, leading to enteritis, diarrhea, and skin irritation from larval penetration, with rare signs in adult horses.

Diagnosis and Treatment of Strongyloides westeri

• Diagnosis involves fecal examination for eggs or skin scraping for larvae.
• Treatment includes anthelmintics such as ivermectin; preventive measures involve maintaining clean environments.

Life Cycle and Clinical Implications of Parascaris equorum

• Direct life cycle with infective eggs remaining viable in the environment for extended periods.
• Clinical signs in foals include coughing, weight loss, and potential fatal intestinal complications from heavy infections.

Pathology and Diagnosis of Parascaris equorum

• Light infections may show mild signs, while heavy burdens can cause severe complications.
• Diagnosis is based on identifying characteristic eggs in fecal samples.

Strongylus spp. Life Cycle and Clinical Presentation

• Direct life cycle with infective L3 larvae ingested by horses leading to adult maturation in the cecum and colon.
• Clinical signs include weight loss, lethargy, and diarrhea; S. vulgaris being the most pathogenic species.

Diagnosis, Treatment, and Control of Strongylus spp.

• Diagnosis is based on clinical signs and strongyle-type eggs in feces.
• Treatment includes broad-spectrum anthelmintics, coupled with pasture management to control parasite load.

Life Cycle and Diagnosis of Oxyuris equi

• Direct life cycle; infection occurs through egg ingestion, leading to symptoms primarily involving intense itching around the tail.
• Diagnosis typically employs the "scotch tape test" for egg collection.

Small Strongyles (Cyathostomins) Overview

• Small strongyles do not migrate extensively; they encyst in the gastrointestinal mucosa, potentially leading to serious clinical issues upon mass emergence.
• Light infections may be asymptomatic, while heavy infections can cause significant intestinal damage and associated clinical signs.

Pathology, Diagnosis, and Treatment of Small Strongyle Infections

• Severe mucosal damage can occur due to emerging larvae, causing significant clinical disease.
• Fecal egg counts assist in diagnosis, but cases of larval cyathostominosis may present low egg counts.

Anoplocephala perfoliata Life Cycle and Clinical Presentation

• Indirect life cycle involving oribatid mites as intermediate hosts; infection occurs through ingestion of infected mites.
• Horses may be asymptomatic but can develop severe complications like colic or intussusception with heavy infections.

Pathology Associated with Anoplocephala perfoliata

• Causes local inflammation and mucosal damage, particularly at the ileocecal junction, leading to potential serious gastrointestinal complications.### Anoplocephala perfoliata (Tapeworm)
• Inflammation from Anoplocephala perfoliata can cause impaired motility and complications like ileal impaction, cecal intussusception, and potential rupture of the cecum.
• Younger horses and those in poor pasture management are at higher risk for heavy infections and clinical signs.
• Horses grazing in areas with dense vegetation and high humidity are more likely to get infected, as these environments support oribatid mite populations.
• Diagnosis is challenging due to inconsistent shedding of eggs in feces; fecal flotation has low sensitivity. Enhanced fecal egg counts or ELISA tests improve diagnostic accuracy.
• Treatment involves anthelmintics like praziquantel or double doses of pyrantel pamoate; deworming should occur yearly, typically in the fall or winter.
• Preventive strategies include managing pasture conditions to reduce oribatid mite exposure.
• Anoplocephala perfoliata poses no zoonotic threat and is specific to equines.

Dictyocaulus arnfieldi (Lungworm)

• Dictyocaulus arnfieldi is classified under the order Strongylida and primarily affects equines, especially donkeys.
• Donkeys are asymptomatic carriers, while horses can develop clinical signs when sharing pastures with infected donkeys.
• The direct life cycle involves adult lungworms in the bronchi, laying eggs that develop into larvae, which horses and donkeys ingest while grazing.
• Clinical signs in horses may include coughing, nasal discharge, dyspnea, and exercise intolerance. Donkeys seldom show symptoms despite carrying the infection.
• The presence of lungworms causes bronchitis, excess mucus, and can lead to secondary bacterial infections.
• Donkeys serve as reservoirs for Dictyocaulus arnfieldi, increasing infection risk for horses in shared spaces.
• Diagnosis can involve Baermann technique to identify larvae in fresh feces or bronchoalveolar lavage.
• Treatment with ivermectin or moxidectin is effective; controlling co-grazing with donkeys is essential for prevention.

Thelazia lacrymalis (Equine Eyeworm)

• Thelazia lacrymalis is classified under Spirurida and resides primarily in horses' tear ducts and conjunctival sacs, causing irritation.
• The indirect life cycle involves adult worms producing larvae that are picked up by flies, which then deposit infective larvae back onto the horse's eye.
• Clinical signs include excessive tearing, conjunctivitis, swollen eyelids, photophobia, and eye rubbing. In severe cases, ulcers may form.
• Diagnosis is based on direct observation of worms in the eye or signs like excessive tearing.
• Treatment includes manual removal of worms and the use of anthelmintics like ivermectin, along with fly control measures to prevent reinfection.
• Thelazia lacrymalis is not zoonotic; it does not pose a risk to humans.

Onchocerca spp. (Filarial Worms)

• Onchocerca spp. are nematodes under the order Spirurida primarily affecting the skin and connective tissues of horses.
• Biting flies, like Culicoides and Simulium species, are the vectors for transmission.
• The life cycle is indirect, with adult worms residing in connective tissues and their microfilariae migrating to the skin, which are ingested by flies.
• Most infections are asymptomatic but may cause pruritus, hair loss, and localized nodules due to microfilariae in the skin and eye inflammation.
• Diagnosis is based on clinical signs, skin biopsies, and serological testing for Onchocerca DNA.
• Treatment primarily involves ivermectin or moxidectin, with control focusing on reducing fly exposure.
• Onchocerca spp. are not zoonotic, posing no risk to humans.

Habronema spp. (Stomach Parasite)

• Habronema spp. are classified under Spirurida, typically inhabiting the stomach of horses but can cause cutaneous lesions known as summer sores.
• The life cycle is indirect, involving eggs or larvae passed in feces and ingested by flies, which then deposit infective larvae on the horse's skin.
• Cutaneous habronemiasis leads to non-healing, granulomatous skin lesions, particularly around the face, eyes, and wounds.
• Lesions may appear reddish-brown, greasy, and can contain calcified material.
• Diagnosis involves identifying non-healing lesions and larvae in skin scrapings or biopsies.
• Treatment includes systemic anthelmintics and topical medications; fly control measures are crucial for prevention.
• Habronema spp. do not pose zoonotic threats as they are specific to equines.

Classification of Equine Parasites

• Draschia megastoma, Habronema muscae, and Habronema microstoma are nematodes classified under the order Spirurida, commonly known as equine stomach worms.
• Strongyloides westeri is a nematode under the order Rhabditida, referred to as the equine threadworm.
• Parascaris equorum is a large roundworm classified under the order Ascaridida, known as the equine ascarid or large roundworm.
• Strongylus spp. are nematodes in the order Strongylida, known as large strongyles or bloodworms.
• Oxyuris equi is classified as a nematode under the order Oxyurida, commonly called the equine pinworm.
• Small strongyles, or cyathostomins, belong to the superfamily Strongyloidea and order Strongylida, consisting of over 40 species.
• Anoplocephala perfoliata is a cestode (tapeworm) in the order Cyclophyllidea and family Anoplocephalidae, being the most common tapeworm in horses.

Prevalence and Clinical Impact

• Habronema muscae is the most prevalent equine stomach worm, while Draschia megastoma causes the most severe lesions, including large nodules filled with necrotic material in the stomach.

Life Cycle of Stomach Worms

• The life cycle of Draschia megastoma, Habronema muscae, and Habronema microstoma is indirect, with flies as the intermediate host.
• Adult worms in the horse's stomach release eggs or L1 larvae, which are ingested by flies, developing into infective L3 larvae.
• If ingested by the horse, L3 larvae mature into adults; if deposited on wounds, they cause summer sores but do not mature into adults.
• The prepatent period for these worms is approximately two months.

Clinical presentations of Stomach Worm Infections

• Most horses ingesting L3 larvae remain asymptomatic; however, heavy infections can lead to gastritis.
• Draschia megastoma can cause severe lesions with nodules up to 10 cm in diameter, potentially leading to fatal complications.
• Cutaneous habronemiasis occurs when L3 larvae are deposited on wounds, causing reddish-brown, itchy lesions known as summer sores.

Diagnosis and Treatment of Stomach Worms

• Diagnosis is challenging; routine fecal flotation often misses eggs, necessitating alternative methods like gastroscopy or necropsy.
• Anthelmintics like moxidectin are used for treatment; surgical intervention may be necessary for severe summer sores.
• Accordingly, fly management is crucial to decrease exposure to larvae.

Classification and Life Cycle of Strongyloides westeri

• Strongyloides westeri’s life cycle is direct, alternating between parasitic and free-living forms, with parasitic females in hosts.
• Infective L3 larvae can penetrate skin or be ingested, affecting the small intestine, or be transmitted through mare's milk to foals.

Clinical Presentation of Strongyloides westeri

• Affects primarily foals, leading to enteritis, diarrhea, and skin irritation from larval penetration, with rare signs in adult horses.

Diagnosis and Treatment of Strongyloides westeri

• Diagnosis involves fecal examination for eggs or skin scraping for larvae.
• Treatment includes anthelmintics such as ivermectin; preventive measures involve maintaining clean environments.

Life Cycle and Clinical Implications of Parascaris equorum

• Direct life cycle with infective eggs remaining viable in the environment for extended periods.
• Clinical signs in foals include coughing, weight loss, and potential fatal intestinal complications from heavy infections.

Pathology and Diagnosis of Parascaris equorum

• Light infections may show mild signs, while heavy burdens can cause severe complications.
• Diagnosis is based on identifying characteristic eggs in fecal samples.

Strongylus spp. Life Cycle and Clinical Presentation

• Direct life cycle with infective L3 larvae ingested by horses leading to adult maturation in the cecum and colon.
• Clinical signs include weight loss, lethargy, and diarrhea; S. vulgaris being the most pathogenic species.

Diagnosis, Treatment, and Control of Strongylus spp.

• Diagnosis is based on clinical signs and strongyle-type eggs in feces.
• Treatment includes broad-spectrum anthelmintics, coupled with pasture management to control parasite load.

Life Cycle and Diagnosis of Oxyuris equi

• Direct life cycle; infection occurs through egg ingestion, leading to symptoms primarily involving intense itching around the tail.
• Diagnosis typically employs the "scotch tape test" for egg collection.

Small Strongyles (Cyathostomins) Overview

• Small strongyles do not migrate extensively; they encyst in the gastrointestinal mucosa, potentially leading to serious clinical issues upon mass emergence.
• Light infections may be asymptomatic, while heavy infections can cause significant intestinal damage and associated clinical signs.

Pathology, Diagnosis, and Treatment of Small Strongyle Infections

• Severe mucosal damage can occur due to emerging larvae, causing significant clinical disease.
• Fecal egg counts assist in diagnosis, but cases of larval cyathostominosis may present low egg counts.

Anoplocephala perfoliata Life Cycle and Clinical Presentation

• Indirect life cycle involving oribatid mites as intermediate hosts; infection occurs through ingestion of infected mites.
• Horses may be asymptomatic but can develop severe complications like colic or intussusception with heavy infections.

Pathology Associated with Anoplocephala perfoliata

• Causes local inflammation and mucosal damage, particularly at the ileocecal junction, leading to potential serious gastrointestinal complications.### Anoplocephala perfoliata (Tapeworm)
• Inflammation from Anoplocephala perfoliata can cause impaired motility and complications like ileal impaction, cecal intussusception, and potential rupture of the cecum.
• Younger horses and those in poor pasture management are at higher risk for heavy infections and clinical signs.
• Horses grazing in areas with dense vegetation and high humidity are more likely to get infected, as these environments support oribatid mite populations.
• Diagnosis is challenging due to inconsistent shedding of eggs in feces; fecal flotation has low sensitivity. Enhanced fecal egg counts or ELISA tests improve diagnostic accuracy.
• Treatment involves anthelmintics like praziquantel or double doses of pyrantel pamoate; deworming should occur yearly, typically in the fall or winter.
• Preventive strategies include managing pasture conditions to reduce oribatid mite exposure.
• Anoplocephala perfoliata poses no zoonotic threat and is specific to equines.

Dictyocaulus arnfieldi (Lungworm)

• Dictyocaulus arnfieldi is classified under the order Strongylida and primarily affects equines, especially donkeys.
• Donkeys are asymptomatic carriers, while horses can develop clinical signs when sharing pastures with infected donkeys.
• The direct life cycle involves adult lungworms in the bronchi, laying eggs that develop into larvae, which horses and donkeys ingest while grazing.
• Clinical signs in horses may include coughing, nasal discharge, dyspnea, and exercise intolerance. Donkeys seldom show symptoms despite carrying the infection.
• The presence of lungworms causes bronchitis, excess mucus, and can lead to secondary bacterial infections.
• Donkeys serve as reservoirs for Dictyocaulus arnfieldi, increasing infection risk for horses in shared spaces.
• Diagnosis can involve Baermann technique to identify larvae in fresh feces or bronchoalveolar lavage.
• Treatment with ivermectin or moxidectin is effective; controlling co-grazing with donkeys is essential for prevention.

Thelazia lacrymalis (Equine Eyeworm)

• Thelazia lacrymalis is classified under Spirurida and resides primarily in horses' tear ducts and conjunctival sacs, causing irritation.
• The indirect life cycle involves adult worms producing larvae that are picked up by flies, which then deposit infective larvae back onto the horse's eye.
• Clinical signs include excessive tearing, conjunctivitis, swollen eyelids, photophobia, and eye rubbing. In severe cases, ulcers may form.
• Diagnosis is based on direct observation of worms in the eye or signs like excessive tearing.
• Treatment includes manual removal of worms and the use of anthelmintics like ivermectin, along with fly control measures to prevent reinfection.
• Thelazia lacrymalis is not zoonotic; it does not pose a risk to humans.

Onchocerca spp. (Filarial Worms)

• Onchocerca spp. are nematodes under the order Spirurida primarily affecting the skin and connective tissues of horses.
• Biting flies, like Culicoides and Simulium species, are the vectors for transmission.
• The life cycle is indirect, with adult worms residing in connective tissues and their microfilariae migrating to the skin, which are ingested by flies.
• Most infections are asymptomatic but may cause pruritus, hair loss, and localized nodules due to microfilariae in the skin and eye inflammation.
• Diagnosis is based on clinical signs, skin biopsies, and serological testing for Onchocerca DNA.
• Treatment primarily involves ivermectin or moxidectin, with control focusing on reducing fly exposure.
• Onchocerca spp. are not zoonotic, posing no risk to humans.

Habronema spp. (Stomach Parasite)

• Habronema spp. are classified under Spirurida, typically inhabiting the stomach of horses but can cause cutaneous lesions known as summer sores.
• The life cycle is indirect, involving eggs or larvae passed in feces and ingested by flies, which then deposit infective larvae on the horse's skin.
• Cutaneous habronemiasis leads to non-healing, granulomatous skin lesions, particularly around the face, eyes, and wounds.
• Lesions may appear reddish-brown, greasy, and can contain calcified material.
• Diagnosis involves identifying non-healing lesions and larvae in skin scrapings or biopsies.
• Treatment includes systemic anthelmintics and topical medications; fly control measures are crucial for prevention.
• Habronema spp. do not pose zoonotic threats as they are specific to equines.

Classification of Equine Parasites

• Draschia megastoma, Habronema muscae, and Habronema microstoma are nematodes classified under the order Spirurida, commonly known as equine stomach worms.
• Strongyloides westeri is a nematode under the order Rhabditida, referred to as the equine threadworm.
• Parascaris equorum is a large roundworm classified under the order Ascaridida, known as the equine ascarid or large roundworm.
• Strongylus spp. are nematodes in the order Strongylida, known as large strongyles or bloodworms.
• Oxyuris equi is classified as a nematode under the order Oxyurida, commonly called the equine pinworm.
• Small strongyles, or cyathostomins, belong to the superfamily Strongyloidea and order Strongylida, consisting of over 40 species.
• Anoplocephala perfoliata is a cestode (tapeworm) in the order Cyclophyllidea and family Anoplocephalidae, being the most common tapeworm in horses.

Prevalence and Clinical Impact

• Habronema muscae is the most prevalent equine stomach worm, while Draschia megastoma causes the most severe lesions, including large nodules filled with necrotic material in the stomach.

Life Cycle of Stomach Worms

• The life cycle of Draschia megastoma, Habronema muscae, and Habronema microstoma is indirect, with flies as the intermediate host.
• Adult worms in the horse's stomach release eggs or L1 larvae, which are ingested by flies, developing into infective L3 larvae.
• If ingested by the horse, L3 larvae mature into adults; if deposited on wounds, they cause summer sores but do not mature into adults.
• The prepatent period for these worms is approximately two months.

Clinical presentations of Stomach Worm Infections

• Most horses ingesting L3 larvae remain asymptomatic; however, heavy infections can lead to gastritis.
• Draschia megastoma can cause severe lesions with nodules up to 10 cm in diameter, potentially leading to fatal complications.
• Cutaneous habronemiasis occurs when L3 larvae are deposited on wounds, causing reddish-brown, itchy lesions known as summer sores.

Diagnosis and Treatment of Stomach Worms

• Diagnosis is challenging; routine fecal flotation often misses eggs, necessitating alternative methods like gastroscopy or necropsy.
• Anthelmintics like moxidectin are used for treatment; surgical intervention may be necessary for severe summer sores.
• Accordingly, fly management is crucial to decrease exposure to larvae.

Classification and Life Cycle of Strongyloides westeri

• Strongyloides westeri’s life cycle is direct, alternating between parasitic and free-living forms, with parasitic females in hosts.
• Infective L3 larvae can penetrate skin or be ingested, affecting the small intestine, or be transmitted through mare's milk to foals.

Clinical Presentation of Strongyloides westeri

• Affects primarily foals, leading to enteritis, diarrhea, and skin irritation from larval penetration, with rare signs in adult horses.

Diagnosis and Treatment of Strongyloides westeri

• Diagnosis involves fecal examination for eggs or skin scraping for larvae.
• Treatment includes anthelmintics such as ivermectin; preventive measures involve maintaining clean environments.

Life Cycle and Clinical Implications of Parascaris equorum

• Direct life cycle with infective eggs remaining viable in the environment for extended periods.
• Clinical signs in foals include coughing, weight loss, and potential fatal intestinal complications from heavy infections.

Pathology and Diagnosis of Parascaris equorum

• Light infections may show mild signs, while heavy burdens can cause severe complications.
• Diagnosis is based on identifying characteristic eggs in fecal samples.

Strongylus spp. Life Cycle and Clinical Presentation

• Direct life cycle with infective L3 larvae ingested by horses leading to adult maturation in the cecum and colon.
• Clinical signs include weight loss, lethargy, and diarrhea; S. vulgaris being the most pathogenic species.

Diagnosis, Treatment, and Control of Strongylus spp.

• Diagnosis is based on clinical signs and strongyle-type eggs in feces.
• Treatment includes broad-spectrum anthelmintics, coupled with pasture management to control parasite load.

Life Cycle and Diagnosis of Oxyuris equi

• Direct life cycle; infection occurs through egg ingestion, leading to symptoms primarily involving intense itching around the tail.
• Diagnosis typically employs the "scotch tape test" for egg collection.

Small Strongyles (Cyathostomins) Overview

• Small strongyles do not migrate extensively; they encyst in the gastrointestinal mucosa, potentially leading to serious clinical issues upon mass emergence.
• Light infections may be asymptomatic, while heavy infections can cause significant intestinal damage and associated clinical signs.

Pathology, Diagnosis, and Treatment of Small Strongyle Infections

• Severe mucosal damage can occur due to emerging larvae, causing significant clinical disease.
• Fecal egg counts assist in diagnosis, but cases of larval cyathostominosis may present low egg counts.

Anoplocephala perfoliata Life Cycle and Clinical Presentation

• Indirect life cycle involving oribatid mites as intermediate hosts; infection occurs through ingestion of infected mites.
• Horses may be asymptomatic but can develop severe complications like colic or intussusception with heavy infections.

Pathology Associated with Anoplocephala perfoliata

• Causes local inflammation and mucosal damage, particularly at the ileocecal junction, leading to potential serious gastrointestinal complications.### Anoplocephala perfoliata (Tapeworm)
• Inflammation from Anoplocephala perfoliata can cause impaired motility and complications like ileal impaction, cecal intussusception, and potential rupture of the cecum.
• Younger horses and those in poor pasture management are at higher risk for heavy infections and clinical signs.
• Horses grazing in areas with dense vegetation and high humidity are more likely to get infected, as these environments support oribatid mite populations.
• Diagnosis is challenging due to inconsistent shedding of eggs in feces; fecal flotation has low sensitivity. Enhanced fecal egg counts or ELISA tests improve diagnostic accuracy.
• Treatment involves anthelmintics like praziquantel or double doses of pyrantel pamoate; deworming should occur yearly, typically in the fall or winter.
• Preventive strategies include managing pasture conditions to reduce oribatid mite exposure.
• Anoplocephala perfoliata poses no zoonotic threat and is specific to equines.

Dictyocaulus arnfieldi (Lungworm)

• Dictyocaulus arnfieldi is classified under the order Strongylida and primarily affects equines, especially donkeys.
• Donkeys are asymptomatic carriers, while horses can develop clinical signs when sharing pastures with infected donkeys.
• The direct life cycle involves adult lungworms in the bronchi, laying eggs that develop into larvae, which horses and donkeys ingest while grazing.
• Clinical signs in horses may include coughing, nasal discharge, dyspnea, and exercise intolerance. Donkeys seldom show symptoms despite carrying the infection.
• The presence of lungworms causes bronchitis, excess mucus, and can lead to secondary bacterial infections.
• Donkeys serve as reservoirs for Dictyocaulus arnfieldi, increasing infection risk for horses in shared spaces.
• Diagnosis can involve Baermann technique to identify larvae in fresh feces or bronchoalveolar lavage.
• Treatment with ivermectin or moxidectin is effective; controlling co-grazing with donkeys is essential for prevention.

Thelazia lacrymalis (Equine Eyeworm)

• Thelazia lacrymalis is classified under Spirurida and resides primarily in horses' tear ducts and conjunctival sacs, causing irritation.
• The indirect life cycle involves adult worms producing larvae that are picked up by flies, which then deposit infective larvae back onto the horse's eye.
• Clinical signs include excessive tearing, conjunctivitis, swollen eyelids, photophobia, and eye rubbing. In severe cases, ulcers may form.
• Diagnosis is based on direct observation of worms in the eye or signs like excessive tearing.
• Treatment includes manual removal of worms and the use of anthelmintics like ivermectin, along with fly control measures to prevent reinfection.
• Thelazia lacrymalis is not zoonotic; it does not pose a risk to humans.

Onchocerca spp. (Filarial Worms)

• Onchocerca spp. are nematodes under the order Spirurida primarily affecting the skin and connective tissues of horses.
• Biting flies, like Culicoides and Simulium species, are the vectors for transmission.
• The life cycle is indirect, with adult worms residing in connective tissues and their microfilariae migrating to the skin, which are ingested by flies.
• Most infections are asymptomatic but may cause pruritus, hair loss, and localized nodules due to microfilariae in the skin and eye inflammation.
• Diagnosis is based on clinical signs, skin biopsies, and serological testing for Onchocerca DNA.
• Treatment primarily involves ivermectin or moxidectin, with control focusing on reducing fly exposure.
• Onchocerca spp. are not zoonotic, posing no risk to humans.

Habronema spp. (Stomach Parasite)

• Habronema spp. are classified under Spirurida, typically inhabiting the stomach of horses but can cause cutaneous lesions known as summer sores.
• The life cycle is indirect, involving eggs or larvae passed in feces and ingested by flies, which then deposit infective larvae on the horse's skin.
• Cutaneous habronemiasis leads to non-healing, granulomatous skin lesions, particularly around the face, eyes, and wounds.
• Lesions may appear reddish-brown, greasy, and can contain calcified material.
• Diagnosis involves identifying non-healing lesions and larvae in skin scrapings or biopsies.
• Treatment includes systemic anthelmintics and topical medications; fly control measures are crucial for prevention.
• Habronema spp. do not pose zoonotic threats as they are specific to equines.