Equine Nematodes Flashcards
Drashia megastoma-Hosts
Habronema spp.
Equine
Drashia megastoma-Identification
Habronema spp.
D. megastoma-Adults: 13mm long, funnel-shaped buccal cavity, nodules close to the margo plicatus
Habronema spp.-Adults: 22-25 mm long, cylindrical buccal cavity
Eggs: Thin-shelled, larvated, 40-55 x 8-16 um
Drashia megastoma-Life Cycle
Habronema spp.
Indirect.
IH: Diptera Muscidae, Musca spp., Stomoxys calcitrans
L3 infective stage
Adults/larvae in stomach
larvae also in skin (“wrong place at wrong time”)
Drashia megastoma-Pathogenesis and Lesions
Habronema spp.
Larvae -cutaneous habronemiasis and cutaneous draschiasis -granular conjunctivitis Adults -nodules in stomach
Drashia megastoma-Site of Infection
Habronema spp.
Adults/larvae in stomach
L3 in skin = “wrong place at wrong time”
Draschia megastoma-Clinical Signs
Habronema spp.
Larvae cause “summer sores”
Adults cause gastritis
Draschia megastoma-Diagnosis
Habronema spp.
Biopsy or skin-scraping of lesions to reveal larvae
Eggs difficult to recover in feces
Draschia megastoma-Treatment and Prevention
Habronema spp.
MCLs approved
Fly control
Ivermectin no longer effective-Resistance?
Parascaris equorum-Hosts
Equine
Parascaris equorum-Identification
Adults: Long, 30cm, white to cream colored, 3 large lips
Eggs: thick-walled, 90um
Parascaris equorum-Life Cycle
Direct. PPP = 10-12 wks
Direct and Per Os
No transmammary or transplacental transmission
L2 in egg is infective is swallowed→ hepatic-tracheal migration→ devel. to L3 in trachea→ swallowed→ devel. to L4 and migrate to small intestine→ adult
Parascaris equorum-Site of Infection
Small Intestine
Parascaris equorum-Pathogenesis and Lesions
Perforation, intestinal obstruction, unthriftiness or production losses
Parascaris equorum-Clinical Signs
Coughing during migratory phases, unthriftiness in young animals with heavy infections
Parascaris equorum-Diagnosis
Fecal flotation for eggs
Eggs may be absent with clinical signs
Parascaris equorum-Treatment and Prevention
Anthelmintics, timing of treatment
Resistance with some MCLs
Strongyloides westeri-Common Name
Threadworm
Strongyloides westeri-Hosts
Equine
Strongyloides westeri-Identification
Adults: slender hair-like nematodes, less than 1 cm long, long esophagus (1/3 of body)
Eggs: Thin-shelled, larvated, 30-40 um
Strongyloides westeri-Life Cycle
Direct. PPP = 10-14d
Parasitic (homogonic) and Free-living (heterogonic) phases
L3 infective stage
Per Os, Percutatneous, Transmammary
Strongyloides westeri-Site of Infection
Adults in small intestine
Larvae in somatic tissues
Strongyloides westeri-Pathogenesis and Lesions
Erythematous reaction from larval penetration of skin
Strongyloides westeri-Clinical Signs
Larvae cause urticaria, “frenzy”
Adults cause diarrhea (usually in young)
Strongyloides westeri-Diagnosis
Fecal flotation reveals eggs with L1
Baermann
expect to see parasite in <5mths old horses
Strongyloides westeri-Treatment and Prevention
Incorporated with control of Strongyles and ascarids, normally not a critical parasite
Oxyuris equi-Common Name
Large Pinworm
Oxyuris equi-Hosts
Equine
Oxyuris equi-Identification
Adults: long white nematode with pointed tails reaching 10cm (4in)
Eggs: 85 x 40um, single operculum, flatter on one side
Oxyuris equi-Life Cycle
Direct. PPP = 4-5mths
Adults in dorsal colon→ gravid female migrates to anus to lay eggs around perineum→ eggs laid with gelatinous substance (irritant)→ larva devel. to L3 in egg
Egg with L3 infective stage
Oxyuris equi-Site of Infection
Large Intestine
Oxyuris equi-Pathogenesis and Lesions
Pruritus
Oxyuris equi-Clinical Signs
Peri-anal irritation (from eggs and gelatinous substance)
Oxyuris equi-Diagnosis
Broken hair at tailhead
Adhesive tape method
Perianal scraping method
Oxyuris equi-Treatment and Prevention
Parasitides (MCLs, FBZ, etc.)
Resistance suspected
Strongylus spp.-Common Name
Large Strongyles
S. vulgaris, S. edentatus, S. equinis
Strongylus spp.-Hosts
Equine
Strongylus spp.-Identification
Adults: globular mouth capsule,
S. vulgaris: 1-2cm, 2 dorsal ear-shaped teeth in mouth
S. edentatus: 3-4cm, no teeth
S. equinus: 3-4cm, one large tooth with a bifid tip and two smaller subventral teeth
Eggs: all the same, 60-120 x 35-60um
Strongylus spp.-Life Cycle
Direct. PPP = 6mths
L3 are infective stage
L3 ingested while grazing→ migrate to cranial mesenteric and ileocolic a.a. molting along the way (S. vulgaris) / through liver and abdominal tissues (S. edentatus) / through liver (S. equinus)→ migrate back to large intestines→ adults
Strongylus spp.-Site of Infection
Larvae in arterial vessels of intestines (S. vulgaris), liver and abdominal tissues (S. edentatus) or liver (S. equinus)
Adults: Large intestine
Strongylus spp.-Pathogenesis and Lesions
Larvae-
Arteritis, marked thickening of arterial wall, thrombus, infarction, death, aberrent larval migration
Adults-
bloodsuckers, remove plugs of mucosa
Strongylus spp.-Clinical Signs
Larvae cause thrombo-embolus, colic
Adults cause anemia with heavy infection
Strongylus spp.-Diagnosis
Eggs in fecal–Cannot differentiate small from large strongyles
L3 in culture
Migrating larvae–ultrasound, rectal exam and palpation, arteriography
Adults–necropsy
Strongylus spp.-Treatment and Prevention
Anthelmintics
No resistance
Cyathostominae-Common Name
Small strongyles or cyathostomins
Cyathostominae-Hosts
Equine
Cyathostominae-Identification
Adults: less than 15mm in length, mouth capsule not globular but rectangular or square
Eggs: typical strongyle, 60-120 x 35-60um
Cyathostominae-Life Cycle
Direct. PPP = 6wks to 2-4 mths
L3 infective form
L3 ingested while grazing→ penetrate large intestinal wall→ emerge later as L4→ adults
Arrested devel. up to 2.5 yrs.
Cyathostominae-Site of Infection
Larvae within cecum, ventral/dorsal colon
Adults in intestinal lumen (lg. intestine)
Cyathostominae-Pathogenesis and Lesions
Larval cyathostominosis
lymphocytic and eosinophilic infiltration
Catarrhal colitis
Protein losing enteropathy
Cyathostominae-Clinical Signs
Affects younger horses
Clinical signs associated with emergence of L4
Chronic diarrhea, colic, severe weight loss, edema, intussusception
Seasonality
Cyathostominae-Diagnosis
Eggs in fecal exam
L3 in culture
Cyathostominae-Treatment and Prevention
Some BZs and MCLs for mucosal larval stages
BZs, MCLs, and others for adults
Resistance known to all drug classes
Treat animals contaminating the pasture, clean up feces, mixed grazing, do not overstock
Dictyocaulus arnfieldi-Common Name
Lungworm
Dictyocaulus arnfieldi-Hosts
Donkeys
In horses, adults do not reach sexually maturity
Dictyocaulus arnfieldi-Identification
Adults: Long, slender, white nematodes, 8cm
L1: 400um
Eggs: 75um
Dictyocaulus arnfieldi-Life Cycle
Direct. PPP = 2-4mths
Adults in bronchi lay eggs containing L1→ eggs hatch in lungs and in feces→ eggs and L1 found in feces→ devel. to L3→ migrate from feces to herbage→ L3 ingested
Dictyocaulus arnfieldi-Site of Infection
Bronchi
Dictyocaulus arnfieldi-Pathogenesis and Lesions
None in donkeys
Highly pathogenic in horses–damage to pulmonary tissues
Dictyocaulus arnfieldi-Clinical Signs
No clinical signs in donkeys
Horses: chronic, productive cough
Dictyocaulus arnfieldi-Diagnosis
L1 in eggs recovered from feces and lung washings with Baermann
Adults in lungs at necropsy
Dictyocaulus arnfieldi-Treatment and Prevention
In endemic areas do not pasture donkeys and horses together
Setaria equina-Hosts
Equine
IH: mosquitoes
Setaria equina-Identification
Superfamily: Filarioidea
Adults: long slender worms, 12cm
Setaria equina-Diagnosis
Mff in blood smears
Adults in peritoneal cavity
Onchocerca cervicalis-Hosts
Equine
IH: Culicoides spp.
Onchocerca cervicalis-Identification
Adults: slender nematodes b/w 2-6cm and lie tightly coiled in tissue nodules
Onchocerca cervicalis-Diagnosis
Mff in tissue spaces of the skin→recovered in saline incubation of skin biopsies
Fistulous withers-open purulent lesions
