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Parasitology > Ruminant Lungworms > Flashcards

Ruminant Lungworms Flashcards

1
Q

Lungworms of large animals

A

two superfamilies: trichostrongyloidea and metastrongyloidea

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2
Q

Trichostrongyloidea

A

direct life cycle

dictyocaulus species- unusual in that it lives in the lungs (i.e. other trichostrongylids live in GI tract)

Cause parasitic bronchitis (husk)- mostly in dairy cattle

HIGHLY pathogenic

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3
Q

Metastrongyloidea

A

indirect life cycle with IMHs

Metastrongylus species in pigs (earthworm IMH)

Muellerius capillaris in sheep/goats (mollusc IMH)

Protostrongylus rufescens in sheep/goats (snail intermediate host)

NON pathogenic

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4
Q

Trichostrongyloidea lungworms

A

**Ditcyocaulus viviparus- cattle

dictyocaulus arnfieldi- horse and donkeys

Dictyocaulus filaria- sheep and goats

Dictyocaulus eckerti- deer and other cervids–nb: deer can be carriers of dictyocaulus viviparus

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5
Q

Life cycle of Dictyocaulus viviparus

A

Direct life cycle

Adult worms in mainstem of bronchi/trachea (live for 1-2 months or so)–> produce eggs which hatch in lungs–> L1 migrate up trachea and get swallowed–> L1 in feces (different from GI nematodes because they hatch internally)–> L2–>L3–>L3 is infective; gets ingested and penetrates intestinal mucosa–>moults to L4 in mesenteric lymph nodes–>lymphovascular route to lungs–>enter into alveoli–> young adults in bronchioles and small bronchi

nb: pilobolus fungus aids in dispersal of L3s- can get this fungus on fecal pats–> larvae move up to fungus–> get explosion of spores which carry/spreads larvae

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6
Q

Appearance of dictyocaulus viviparus (various life stages)

A

L1 larvae: 400-450 microns in length, 25 microns in width

L1 larvae present in feces, NOT eggs

Adults: up to 8cm in length and slender- threadlike, creamy appearance

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7
Q

Immunity to d. viviparus

A

Strong immunity follow infection, but immune response itself can cause pathology–> Ig and eosinophils produced–> happening in lungs, therefore lung damage

Cf. GI nematodes: takes 1-2 years for a strong IR

Immunity is boosted by natural challenge– immunity lasts for ~6 months and wanes if unchallenged.

NB: there is a vaccine for dictyocaulus

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8
Q

Clinical signs of parasitic bronchitis

A

Mildly affected animals (~100 worms): intermittent cough- with an increase in coughing after exercise

Moderately affected animals: coughing at rest, tachypnoe (>60), hyperpnea (crackles in posterior lung lobe)

Severly affected animals (1000 worms approx): harsh cough, tachypnea (>80), dysnpea, mouth breathing (air hunger)

Pyrexia due to secondary bacterial infection, emphysema

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9
Q

Pathogenesis of Parasitic bronchitis

A

penetration phase: d1-7: larvae migrating to lungs (no pathology)

prepatent phase: days 8-25: larvae migrating up through lungs- start to see clinical signs

Patent phase: days 26-60: mature adults in airways–> cause response in lung tissue

Postpatent phase: days 61-90: adults expelled from airways (recovery)

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10
Q

Prepatent phase: days 8-25

A

L4 and young adults migrating up respiratory tree

Acute inflammatory response (monocytes and eosinphils)

Mucus/cellular plugs produced by lung tissue–> collapse of alveoli

First clinical signs seen

Heavy infection: calves can die from day 15 onwards

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11
Q

Patent phase: days 26-60

A

Clinical signs worsen

lesions due to presence of worms in bronchi: Profuse inflammatory exudate; hyperplasia of bronchial epithelium; overinflation of alveoli ; interstitial emphysema and oedema; eosinophilia

lesions due to aspirated eggs/larve: granulomatous response to aspirated eggs.

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12
Q

Post-patent phase: days 61-90

A

expulsion of worms due to IR

Most animals: gradual recovery and strong acquired immunity

Some animals (up to 25%): clinical signs increase–> often fatal

due to either “alveolar epithelialisation” or bacterial infection (acute interstitial pneumonia)

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13
Q

Reinfection syndrome

A

heavy challenge in immune (previously infected or vaccinated)

IR kills larvae in lungs

Mild syndrome: coughing and slight tachypnea

Diagnosis: clinical signs, history and response to tx

Not a patent infection- no L1s, not normally fatal.

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14
Q

Diagnosis of parasitic bronchitis

A

Clinical signs, time of year

Grazing/vax/anthelmintic history

L1 larvae present in feces (50-1000 L1/g, baermann technique)– not present during pre-patent phase

Bronchoalveolar lavage, eosinophilia

ELISA: detects AB to adult and L3 antigens; reflects exposure to infection

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15
Q

Epidemiology of bovine lungworm

A

temperate regions with high rainfall

In UK, disease usually july-sept/oct

L3 can overwinter on pasture

carrier animals are important

small number of L3s cause infection

small numbers of worms sufficient to cause disease (100-1000)

Development L1-L3 rapid in optimal conditions (warm and wet, ~7 days)

Traditionally disease of 1st season grazing calves, now common in adults

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16
Q

Changing age distribution of parasitic bronchitis

A

recently, disease more common in adult cattle

  • no previous history of lungworm or vax
  • anthelmintic usage in 1st and 2nd years so no immunity

susceptible to heavy challenge

also, stocking densities have increased with an increase in intensive farming.

17
Q

Prevention of bovine lungworm

A

vax with irradiated L3 vax (2 doses of 1000 irradiated L3s 4 weeks apart)

vax 1st season calves before turnout

oral vax: very effeceitve but not sterile immunity (therefore don’t mix with unvax animals)

immunity boosted by infection

18
Q

Treatment of bovine lungworm

A

anthelmintic drugs (use early to reduce pathology)

mildly infected animals: treat and move to clean pasture

severely affected: house, hydrate, NSAIDS to damp down IR, abx if pyrexic

Anthelmintics may exacerbate clinical signs in severly affected animals d/t parasite death. Use levamazole with heavy infection because it just paralyzes the worms, rather than killing them and releasing antigen (like BZ)

19
Q

Dictyocaulus arnfieldi

A

donkeys and horses

life cycle similar to D. viviparus except EGGS (not L1s) in feces

PPP=2-4 months

reaches patentcy in donkeys and foals/yearlings in horse

does NOT reach patentcy in adult horses.

Ubiquitous in donkeys–true definitive host (usually no clinical signs)

20
Q

Diagnosis of D. arnfieldi

A

Donkey: eggs or L1s in feces; close exam (harsh lung sounds)

Horse: usually no eggs or L1s; clinical signs (chronic cough or tachypnea); grazing/anthelmintic histroy (i.e. co grazing with donkeys)

Response to anthelmintic tx

Tracheal wash- eosinophilia to confirm infection

21
Q

Dictyocaulus filaria

A

Host: Sheep and Goats

Area: seen more in warmer climates but sporadic UK cases

PPP: 5 weeks

Causes sporadic disease- usually in lambs/yearlings in autumn

Milder clinical signs than d. viviparus: chronic cough/unthriftiness; nasal discharge; dysnpea in severe cases

Diagnosis: L1 in feces

Treat flock, move to clean pasture

22
Q

Metastrongyloid lungworms

A

Pig: metastrongylus apri, M. salmi, M. pudendotectus

pig IMH: earthworm

Sheep/Goats: muellerius capillaris (IMH mollusc) and protostrongylus rufescens (snail IMH)

none are particularly pathogenic

23
Q

Life cycle of Metastrongylus spp. in pigs

A

Ubiquitous

Adults in small bronchi and bronchioles–> eggs produced in feces–> L1 ingested by earthworm–> moult to L2, then L3 in IMH–> earthworms ingested by pigs–> L3 penetrate intestinal mucosa–> L4 in LN–>lymphovascular route to lungs, come out of capillaries into alveoli–> adults

PPP=4 weeks

nb: earthworms can remain infected for a very long time

24
Q

Metastrongylus species, appearance, clinical signs and diagnosis

A

Slender white worms, adutls 6cm long

Clinical signs: mostly light and asymptomatic

Heavy infections: coughing, dyspnea, nasal discharge

Most prevalent in pigs 6-8 months old- infection depends on access to earthworms

Diagnosis: eggs in feces (MgSO4 flotation)

25
Q

Muellerius capillaris

A

Sheep and goats, but goats more affected

Widespread and common

Brown “hair-like” worms found in alveoli

IMH= molluscs

NOT pathogenic

cause lead shot lesions in lungs

Diagnosis: L1 in feces (smaller than D. filaria, with a dorsal tail spine)

26
Q

Protostrongylus rufescens

A

Sheep and goats

less common than muellerius

adults in bronchioles: red 4-6cm

NOT pathogenic

IMH= snails

Lung lesions larger than M. capillaris

heaviest infection in ADULT sheep and goats (as for M. capillaris)

Parasitology (12 decks)

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