Series of Presentations on Nematodes from Veterinary Parasitology By Urquhart, Jenning

1. Metastrongyloidea

2. Characteristics
• Most worms in this superfamily inhabit the lungs
or the blood vessels adjacent to the lungs.
• The typical life cycle is indirect, and the
intermediate host is usually a mollusk.

3. Oslerus osleri (TRACHEAL WORM)
Definitive Host Spectrum
• Canids
Geographic Distribution
• Worldwide, but low prevalence
Morphology
• Adults - males 5 mm, females 9-15 mm
• Eggs - larvated, 80 x 50 microns, hatch before
passing in feces
• Larvae - 232-266 microns, with S-shaped tail

4. Life Cycle (Stages)
• L 1 are passed in feces or saliva
• These L 1 are immediately infective
• Major modes of transmission are by the bitch
licking her pups, fecal contamination, licking of
mouth, and feeding by regurgitation (wild
canids)
• Once acquired larvae migrate to the trachea via
the lymphatic and venous portal systems
• Prepatent period - 6-7 mos.

5. Site of Infection
• Trachea and bronchi
Pathogenesis/Clinical Signs
• Adult worms live in or under the tracheal or
bronchial mucosa and cause grayish-pink
fibrous nodules to develop which cause a cough.
• These granulomas are usually less than 1 cm in
diameter
• Clinical signs - cough, dyspnea, anorexia,
emaciation
• Usually a chronic disease of young dogs, but
can be fatal

6. Diagnosis
• Bronchoscopy - nodules at the bifurcation of the
trachea (predilection site)
• Typical larvae in feces, tracheal swabs or sputum - in
feces they are neither plentiful nor very active
• Thoracic radiography
Treatment
• No satisfactory treatment - can try levamisole,
albendazole, fenbendazole or avermectins (cautionary
in dogs)
Other control Measures
• Remove pups by caesarian section and raise them in
isolation but not practical;

7. Filaroides hirthi (LUNGWORM)
Definitive Host Spectrum
– Canids
Geographic Distribution
– Eastern US, Texas
Morphology
– Adults - males 2-3 mm, females 6.6-13 mm
– Larvae - 240-290 microns long
Life Cycle (Stages)
– Similar to F. osleri
– Prepatent period - 5 weeks

8. Site of Infection: Lung parenchyma
Pathogenesis/Clinical Signs
• Focal granulomatous reaction
• Usually no clinical disease
• Fatalities have occurred in severely stressed or
immune deficient dogs
Diagnosis
• Finding larvae in feces - zinc sulfate flotation is better
than Baermann technique
• Usually diagnosed post mortem
Treatment
• Albendazole
• fenbendazole

9. Aelurostrongylus abstrusus (CAT LUNGWORM)
Definitive Host Spectrum
• Felids
Intermediate Host
• Snails
• Rodents, frogs, lizards and birds may serve as paratenic
hosts
Geographic Distribution
• Worldwide; in the US, southern states
Morphology
• Adults - rarely seen intact because they are deeply
imbedded in tissue; males up to 7 mm, females up to 10
mm
• Larvae - about 360 microns, tail has a double bend and a
dorsal spine

10. Life Cycle (Stages)
• Eggs are laid by females, L 1 hatch and are carried up the
bronchial tree and are swallowed and passed in feces
• Larvae penetrate IH and undergo 2 molts
• Cats acquire the infection either by eating snails or by eating
the paratenic host which has eaten an infected snail
• Larvae migrate from the stomach to the lungs through the
peritoneal and thoracic cavities
• Prepatent period - 4 to 6 weeks
Site of Infection
• Terminal bronchioles and lung parenchyma

11. Pathogenesis/Clinical Signs
• Usually nonpathogenic
• Lesions are subpleural grayish nodules which are firm, raised,
and 1-10 mm in diameter
• The parasite causes smooth muscle hypertrophy of the
bronchioles, alveolar ducts and tunica media of the small
arteries as well as hyperplasia.
• Clinical signs - usually none; in heavy infections cough,
dyspnea, emaciation, nasal discharge and sneezing
Diagnosis
• Typical L 1 in feces
• Radiographic evidence includes bronchial, alveolar disease and
pulmonary artery hypertrophy (PAH)
Treatment
• Fenbendazole
Other Control Measures
• Impractical, try to stop ingestion of intermediate or transport
hosts

12. Protostrongylus rufescens (RED LUNGWORM)
Definitive Host Spectrum: Sheep, goats,
Intermediate Host : Snails (several genera)
Geographic Distribution
– North America, Europe, Africa, Australia
Morphology
– Adults - slender, reddish, males 16-28 mm, females 25-35
mm
– Larvae - 250 to 340 microns; tip of tail has wavy outline, but
no spine
Life Cycle (Stages)
– Larvae (L 1 ) are passed in feces
– L 1 penetrate snails
– 2 molts in snail
– DH ingests snails while grazing
– Migration to the lungs via mesenteric lymph glands and
circulation
– Transplacental transmission occurs
– Prepatent period - 30 to 37 days

13. Site of Infection
– Small bronchioles
Pathogenesis/Clinical Signs
– Worms produce local inflammation of small bronchioles
– Exudate fills alveoli distal to the parasites
– The affected alveolar and bronchiolar epithelium is
desquamated, blood vessels are occluded and infiltration
with round cells occurs resulting in a small focus of lobular
pneumonia
– 2 o bacterial infections possible
– Usually no definite clinical signs

14. Diagnosis
• Finding larvae in feces
Treatment
• Levamisole, fenbendazole, ivermectin, doramectin
Other Control Measures
• Keep lambs off pastures previously used by infected
animals
• Salt blocks or range cubes containing anthelmintics
• Molluscicides

15. Muellerius capillaris (HAIR LUNGWORM)
Definitive Host Spectrum
Sheep, goats,
Intermediate Host
Snails ( Helix , Succinea )
Geographic Distribution
Worldwide, not of major importance in the US
Morphology
Adults - delicate, threadlike; males 12-14 mm, females 19-23 mm
Larvae - 230-300 microns, tip of tail wavy and with a dorsal spine
Life Cycle
L 1 are passed in feces
L 1 penetrate IH or are ingested
2 molts in IH
DH ingests snail or slug while grazing
Migration to lungs via lymphatics
Prepatent period - about 6 weeks

16. First larva of Muellerius
capillaries; whole larva
(A); anterior end (B);
posterior end (C);
wavy tip of the tail with a
dorsal spine

17. Site of Infection
– Alveoli and lung parenchyma, terminal bronchioles
– Pathogenesis/Clinical Signs
– Worms produce grayish nodules up to 2 cm in diameter,
consisting of degenerating leucocytes and pulmonary tissue
– Nodules may calcify
– Occasionally, adenoma-like proliferation of bronchial
epithelium is seen
– 2 o bacterial infection of the nodules may occur; nodules
may coalesce to form septic lesions
– Usually no clinical signs, but in heavily infected goats
coughing and dyspnea may occur
– Diagnosis
– Finding L 1 in feces
– Treatment
– Try repeated doses of fenbendazole, or avermectin class
– Other Control Measures
– Same as for Protostrongylus ; also spreading lime to kill
snails

18. Characteristic nodular lesions associated with
Muellerius infection of sheep lung