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Flashcards in Equine Nematodes Deck (67):
1

Drashia megastoma-Hosts
Habronema spp.

Equine

2

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

3

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")

4

Drashia megastoma-Pathogenesis and Lesions
Habronema spp.

Larvae
-cutaneous habronemiasis and cutaneous draschiasis
-granular conjunctivitis
Adults
-nodules in stomach

5

Drashia megastoma-Site of Infection
Habronema spp.

Adults/larvae in stomach
L3 in skin = "wrong place at wrong time"

6

Draschia megastoma-Clinical Signs
Habronema spp.

Larvae cause "summer sores"
Adults cause gastritis

7

Draschia megastoma-Diagnosis
Habronema spp.

Biopsy or skin-scraping of lesions to reveal larvae
Eggs difficult to recover in feces

8

Draschia megastoma-Treatment and Prevention
Habronema spp.

MCLs approved
Fly control
Ivermectin no longer effective-Resistance?

9

Parascaris equorum-Hosts

Equine

10

Parascaris equorum-Identification

Adults: Long, 30cm, white to cream colored, 3 large lips
Eggs: thick-walled, 90um

11

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

12

Parascaris equorum-Site of Infection

Small Intestine

13

Parascaris equorum-Pathogenesis and Lesions

Perforation, intestinal obstruction, unthriftiness or production losses

14

Parascaris equorum-Clinical Signs

Coughing during migratory phases, unthriftiness in young animals with heavy infections

15

Parascaris equorum-Diagnosis

Fecal flotation for eggs
Eggs may be absent with clinical signs

16

Parascaris equorum-Treatment and Prevention

Anthelmintics, timing of treatment
Resistance with some MCLs

17

Strongyloides westeri-Common Name

Threadworm

18

Strongyloides westeri-Hosts

Equine

19

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

20

Strongyloides westeri-Life Cycle

Direct. PPP = 10-14d
Parasitic (homogonic) and Free-living (heterogonic) phases
L3 infective stage
Per Os, Percutatneous, Transmammary

21

Strongyloides westeri-Site of Infection

Adults in small intestine
Larvae in somatic tissues

22

Strongyloides westeri-Pathogenesis and Lesions

Erythematous reaction from larval penetration of skin

23

Strongyloides westeri-Clinical Signs

Larvae cause urticaria, "frenzy"
Adults cause diarrhea (usually in young)

24

Strongyloides westeri-Diagnosis

Fecal flotation reveals eggs with L1
Baermann
expect to see parasite in <5mths old horses

25

Strongyloides westeri-Treatment and Prevention

Incorporated with control of Strongyles and ascarids, normally not a critical parasite

26

Oxyuris equi-Common Name

Large Pinworm

27

Oxyuris equi-Hosts

Equine

28

Oxyuris equi-Identification

Adults: long white nematode with pointed tails reaching 10cm (4in)
Eggs: 85 x 40um, single operculum, flatter on one side

29

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

30

Oxyuris equi-Site of Infection

Large Intestine

31

Oxyuris equi-Pathogenesis and Lesions

Pruritus

32

Oxyuris equi-Clinical Signs

Peri-anal irritation (from eggs and gelatinous substance)

33

Oxyuris equi-Diagnosis

Broken hair at tailhead
Adhesive tape method
Perianal scraping method

34

Oxyuris equi-Treatment and Prevention

Parasitides (MCLs, FBZ, etc.)
Resistance suspected

35

Strongylus spp.-Common Name

Large Strongyles
(S. vulgaris, S. edentatus, S. equinis)

36

Strongylus spp.-Hosts

Equine

37

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

38

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

39

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

40

Strongylus spp.-Pathogenesis and Lesions

Larvae-
Arteritis, marked thickening of arterial wall, thrombus, infarction, death, aberrent larval migration
Adults-
bloodsuckers, remove plugs of mucosa

41

Strongylus spp.-Clinical Signs

Larvae cause thrombo-embolus, colic
Adults cause anemia with heavy infection

42

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

43

Strongylus spp.-Treatment and Prevention

Anthelmintics
No resistance

44

Cyathostominae-Common Name

Small strongyles or cyathostomins

45

Cyathostominae-Hosts

Equine

46

Cyathostominae-Identification

Adults: less than 15mm in length, mouth capsule not globular but rectangular or square
Eggs: typical strongyle, 60-120 x 35-60um

47

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.

48

Cyathostominae-Site of Infection

Larvae within cecum, ventral/dorsal colon
Adults in intestinal lumen (lg. intestine)

49

Cyathostominae-Pathogenesis and Lesions

Larval cyathostominosis
lymphocytic and eosinophilic infiltration
Catarrhal colitis
Protein losing enteropathy

50

Cyathostominae-Clinical Signs

Affects younger horses
Clinical signs associated with emergence of L4
Chronic diarrhea, colic, severe weight loss, edema, intussusception
Seasonality

51

Cyathostominae-Diagnosis

Eggs in fecal exam
L3 in culture

52

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

53

Dictyocaulus arnfieldi-Common Name

Lungworm

54

Dictyocaulus arnfieldi-Hosts

Donkeys
In horses, adults do not reach sexually maturity

55

Dictyocaulus arnfieldi-Identification

Adults: Long, slender, white nematodes, 8cm
L1: 400um
Eggs: 75um

56

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

57

Dictyocaulus arnfieldi-Site of Infection

Bronchi

58

Dictyocaulus arnfieldi-Pathogenesis and Lesions

None in donkeys
Highly pathogenic in horses--damage to pulmonary tissues

59

Dictyocaulus arnfieldi-Clinical Signs

No clinical signs in donkeys
Horses: chronic, productive cough

60

Dictyocaulus arnfieldi-Diagnosis

L1 in eggs recovered from feces and lung washings with Baermann
Adults in lungs at necropsy

61

Dictyocaulus arnfieldi-Treatment and Prevention

In endemic areas do not pasture donkeys and horses together

62

Setaria equina-Hosts

Equine
IH: mosquitoes

63

Setaria equina-Identification

Superfamily: Filarioidea
Adults: long slender worms, 12cm

64

Setaria equina-Diagnosis

Mff in blood smears
Adults in peritoneal cavity

65

Onchocerca cervicalis-Hosts

Equine
IH: Culicoides spp.

66

Onchocerca cervicalis-Identification

Adults: slender nematodes b/w 2-6cm and lie tightly coiled in tissue nodules

67

Onchocerca cervicalis-Diagnosis

Mff in tissue spaces of the skin→recovered in saline incubation of skin biopsies
Fistulous withers-open purulent lesions