Ruminant

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Ruminant Lungworms and Miscellaneous Nematodes
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Site and ID
Dictyocaulus removed from the airways of a calf.
Worms are large with females 6-8 cm and males 4-5
cm. L1 are passed in feces that have
characteristic glycogen granules. Diagnosis is
by Baermann sedimentation or sugar flotation.
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Dictyocaulus viviparous in large airways of a
calf. Sheep and goats have D. filariae
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Optimum Development

• Direct life cycle. Prepatent period 25 days.
• Occurs sporadically in high rainfall, wet pasture
  conditions of winter and spring in the south,
  summer in the north
• L1-L3 stages are fragile (no sheath), non-feeding
  and very susceptible to heat and drought
• Lungworms oversummer in hosts (adults, /-
  hypobiotic L5) and overwinter as larvae on
  pasture or adults in hosts
• Major Problems Occur In animals with no
  immunity, young age and large L3 exposure in
  winter-spring on crowded, wet pastures
  contaminated by older carrier cattle. Strong
  immunity develops in 1st exposure year.

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Yearling calf with anoxic syndrome in the
prepatent (7-25 day) period. Due to migration
phase of larvae in lungs after massive pasture
exposure to lungworm L3
Dyspnea, anoxia and fever with open mouth
breathing, grunting, frothing, tongue out
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Pathogenesis of Dictyocaulus

• Penetration Clinical signs do not occur 1-7 days
  after infection. Larvae cause minor eosinophilic,
  granulomatous inflammation in lymph node and lung
  during early migration
• Prepatent Anoxic syndrome occurs in the third
  week, during the prepatent period after heavy
  exposure. Larvae cause bronchial pneumonia with
  eosinophilic exudate that blocks small airways,
  leading to atelectasis, edema, emphysema and
  secondary bacterial infection with some
  fatalities. Synergy with Pasteurella and a role
  in the bovine respiratory disease complex have
  been attributed to lungworms
• Patent Patency occurs at 25-55 days. Adult
  worms cause frothy, mucopurulant exudate with
  cough, anorhexia, reduced weight gain.
  Granulomatous consolidation, especially the
  diaphragmatic and cardiac lobes, occurs with
  proliferation of the bronchial epithelium,
  increased macrophages, giant cells and
  eosinophils
• Recovery Occurs at 55-70 days. Worms
  self-cure due to immune response and clinical
  signs decrease. Some become respiratory
  cripples or die 7-8 weeks after infection due to
  alveolar epithelization.

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Grossly visible pulmonary emphysema and
atelectasis associated with bovine lungworms
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Pulmonary emphysema, bovine lungworms
Emphysema occurs with one way valve partial
obstruction of airways, atelectasis is associated
with complete airway obstruction.
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Patent phase lesions Lung lobe showing severe
interstitial edema and inflammation. Lesions and
worms are concentrated in the diaphragmatic and
cardiac lobes. Note the frothy, mucopurulent
exudate with adult lungworms in the airways.
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Histopathological Lesions
Eosinophilic granulomatous inflammation
characterizes the response to lungworms
In some animals inflammation eventually
progresses to alveolar epithelialization and
death at 7-8 weeks
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Carriers are important. Immune older animals
shedding low numbers of larvae are a source of
pasture contamination for young, non-immune
stock. Lungworm losses occur sporadically in the
US. In cool, wet climates in Europe lungworms
can cause major problems (eg husk in Scotland),
where an irradiated L3 larvae vaccine was
developed.
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Sheep and goats (D. filariae) have a similar
pattern of disease as cattle, but are more prone
to chronic respiratory bacterial infections.
Initial cough, nasal discharge are often
concurrent with heavy GI nematode infections.
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Muellerius - alveolar level blister lesions of
this sheep and goat protostrongylid lungworm is
transmitted by land snail intermediate hosts.
Prepatent period is 5-7 weeks
Small, nodular eosinophilic, granulomatous
lesions occur at the terminal bronchiolar and
alveolar level. Muellerius is very common in
goats.
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Notched tail of Muellerius L1 from a goat.
Dictyocaulus L1 have a straight tail and
prominent glycogen granules
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Protostrongylus is a related lungworm that
resides more toward the terminal bronchioles,
with larger infarct-like lesions on the serosal
surface. Not considered to be clinically
important.
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Thelazia spp. (eyeworm)
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Musca autumnalis (face fly) intermediate host of
Thelazia lacrimalis in the Eastern U.S. The
lesser housefly (Fannia spp) transmits eyeworms
in the West.
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Thelazia effects
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Thelazia adults in situ, with corneal ulcer
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Stephanofilaria Typical crusty, eosinophilic
granulomatous dermatitis in umbilical region.
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Stephanofilaria - Horn fly is the intermediate
host.
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Stephanofilaria - Histopathological lesions
showing eosinophilic granulomatous inflammation
Both adults and microfilaria are present in
lesions
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Eleophora
Muzzle disease (necrotic dermatitis) due to
Eleophora in sheep gt5000 feet on Rocky mountain
ranges shared by deer, the normal host.
A tabanid fly is the intermediate host. Disease
is manifested mainly in older 3-5 year-old sheep.
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Eleophora sometimes resides in digital arteries,
with similar dermatitis of the lower limb.
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Adult filarid Eleophora in carotid arteries.
Microfilaria, and inflammatory debris is swept up
to muzzle skin, resulting in inflammation and
necrosis in sheep, an abnormal incidental host.
Elk and moose react even more intensely, with
fatal necrosis and sloughing of the entire
muzzle, including nasal turbinates. Eleophora is
a well tolerated, non pathogen in deer.
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Setaria microfilariae circulate in peripheral
blood to be picked up by mosquito intermediate
host. Adults reside in the abdominal cavity. A
non-pathogenic incidental finding in blood smears.
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Filarids Site and Hosts