Review Questions Exam 3- Final Exam Flashcards
Name the two parasites (only genus) that parasitize the stomach of horses. What are their specific predilection sites?
◦ Drascheia – in tumor-like swellings in the stomach (nodules with creamy pus)
◦ Habronema – on the mucosal surface (does not penetrate the intestinal wall.
How are stomach worms of horses transmitted? Direct or indirect lifecycle? Intermediate hosts?
◦ Indirect lifecycle - The housefly, Stable fly intermediate host
◦ Fly larva develops into adult fly, and then deposits nematode around mouths and lips and are then swallowed.
Which nematode causes summer sores in horses? Where are the larvae found on the horse?
◦ Cutaneous habronemiasis- Infective larvae (L3) deposited on skin wounds
What is the key clinical manifestation of Habronemiasis in horses? How can you control the infection?
◦ “Summer sores” Cutaneous habronemiasis – easy to diagnose based on c/s and L3 morphology( Non-healing skin wounds, Intense pruritus, Larvae in wound scrapings)
◦ Control: Ivermectin (ML) is effective, Control by proper manure management – break the lifecycle, reduce fly population, Fly repellents
Name the most common ascarid of horses? What age group of horse sheds the greatest number of ascarid eggs?
◦ Parascaris equorum
◦ Worm counts high at around 5 months of age!
Know the typical egg morphology of equine ascarid, Parascaris equorum.
◦ Sticky, Thick, Rough Shell, resistant
Which parasite undergoes hepatic-tracheal migration in horses? What is the clinical importance of this migration?
◦ Parascaris equorum -> Physical damage/scarring of liver, lungs, and intestine
◦ Strongyloides westeri-> ?
What is the most significant transmission route of equine threadworm?
◦ Trans-mammary (lactogenic) – most significant route of transmission in foals. Larvae shed in milk for up to 2 months
Which intestinal helminth can cause diarrhea in a 2-week-old foal?
◦ Strongyloides westeri (Equine threadworm)
What is the shed stage of Strongyloides westeri?
◦ Larvated eggs (L1)
Which large strongyle of horse is commonly referred to as “blood worm”?
◦ Strongylus vulgaris (Blood worm)
What is the key pathogenicity of Strongylus vulgaris?
◦ Verminous arteritis, Thrombus – may lead to necrosis
What is the common name of small strongyles of horses?
◦ Cyathostomins
Do small strongyles migrate to visceral organs?
◦ Do not migrate beyond mucous membrane
How does larval cyasthostominosis occur? Which horses are most likely to suffer from this? What are key clinical symptoms?
◦ Occurs in late winter/early spring, when enormous number of larvae emerge from into the gut lumen simultaneously!
◦ Young horses are more susceptible, but any ages can be infected during any season
◦ Diarrhoea, Serious colic and mortality up to 50% , Sometimes may result to granulomatous colitis
Is fecal flotation useful in the diagnosis of larval cyasthostominosis? Why?
◦ Fecal flotation and egg counts not useful – Condition caused by larval stages (not egg-producing adults)
What are common clinical signs associated with pinworm infection in horses? How can you diagnose pinworms? Approach and general morphology?
◦ c./s - Tailrubbing, automutilation
◦ Usually swab or tape mount from perianal region . Fecal float ( less sensitive- eggs not released in feces)
◦ Eggs morphologically distinct from other helminths : asymmetric (flat on one side of oval) with plug on one end. Larval development within egg – very tough!
◦ Morphology (adult): Pointed tail 3/4 length of entire body, may see adult females passed in feces or tail sticking out of perianal region. Classically greyish/white.
What is the most common species of tapeworm in horses? How does the transmission occur?
◦ Anoplocephala perfoliata- ileum and Caecum. Transmitted via free living mites (oribatid mites) Horse must ingest mite that had ingested eggs with hexecanth larvae/ pyriform apparatus.
Remember the characteristic morphology of an equine tapeworm egg.
◦ Eggs with hexacanth larvae/ pyriform apparatus
Where, on the body of the horse, can you find the adults of Onchocerca cervicalis? How is Onchocerca transmitted among horses?
◦ Filarial nematode – Adults in connective tissues - ligamentum nuchae in Equines
◦ Vector-borne – Flies (Biting midges) - Microfilaria in the dermis, rarely in the blood
Which parasite can cause severe coughing in horses, which is often difficult to diagnose from another disease? What do you recommend (approach) for diagnosing this parasite?
◦ Dictyocaulus arnfieldi – Lungworm
◦ Baermann method – Larvae in feces, Clinical signs – Respiratory disturbances, Examination of airways, x-rays, Bronchoscopy – BAL may contain larvae, egg
Which species of Eimeria is common in horses? Is this pathogenic?
◦ Eimeria leukarti
◦ Nonpathogenic
Which species of Sarcocystis is pathogenic in horses? What is the disease caused by this organism? What is the role of horses in the epidemiology of this species? What species maintain this parasite in the wild? Pathophysiology of EPM? The most common symptoms?
◦ Sarcocystis neurona
◦ Equine Protozoal Myeloencephalitis
◦ HORSES are Aberrant IH
◦ Opossum maintains this parasite in the wild.
◦ Pathophysiology of EPM:Zoites cause direct destruction of host neural cells, Acute immune response/inflammation.
◦ Clinical signs: 3A’s - Asymmetry, Ataxia, and Atrophy
‣ Weakness, Muscle atrophy, Ataxia, Seizures, Lameness, Head tilt, facial paralysis, Loss of reflexes
Which parasites are considered as foreign animal diseases (FAD) in horses?
◦ Babesia caballi,
◦ Theileria (Babesia) equi
What is the key clinical sign of Babesiosis in horses?
◦ Acute hemolytic anemia
◦ Fever > 40 C ! Dark urine (hemoglobinuria) Dx: Blood smear
Which mange can lead to “mud fever” in horses?
◦ Chorioptes equi
Which mite species of horses are most contagious and which species is least contagious?
◦ most contagious: Chorioptes equi , Psoroptes equi, Scarcoptes scabiei var. equi,
◦ least contagious: Demodex equi
