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

1. Superfamily Spiruroidae
– In this super family four genera are of veterinary
importance
– Spirocera, Habronema, Thelezia and gnathostoma
– A major characteristic of this group is the tight
spirally coiled tail of the male.
– The life cycle is indirect involving arthropod
intermediate hosts.

2. Spirocerca lupi (ESOPHAGEAL WORM)
Definitive Host Spectrum
• Canids, wild felids
• Accidentally goats and donkeys
Intermediate Host
• Coprophagous beetles
• Lizards, chickens, mice, rabbits may serve as paratenic hosts
Geographic Distribution
• Tropics, warm temperate areas;
Morphology
Adults - reddish, coiled when alive; males up to 5.5 cm, females
up to 8 cm
• Eggs - larvated, thick-shelled, 30-38 x 11-15 microns

3. Life Cycle (Stages)
• Adults reside in nodules, eggs containing L 1 pass through
fistulous tracts and out with the feces
• Eggs are ingested by IH, hatch and develop to L 3
• DH may ingest infected beetles or a paratenic host which has
eaten such a beetle
• Larvae penetrate the stomach wall of the DH and migrate in the
walls of the gastric arteries
• Migration continues to the thoracic aorta
• From the aorta they move into the esophagus
• Large oesophageal granuloma due to Spirocerca lupi infection
• Prepatent period - 5 to 6 months

4. Sites of Infection
• Esophagus- adults
• Thoracic aorta - larvae
Pathogenesis/Clinical Signs
• Migration in the arteries and aorta may cause
hemorrhage, granulomas, and possible rupture
• Adults cause formation of nodules (up to 4 cm) in the
esophagus
• Cause obstruction, hemorrhage
• Clinical signs - vomiting, weight loss

5. Diagnosis
• A flotation solution of high specific gravity (1.36), such as
sodium nitrate, is needed to recover eggs
• Radiography
• Endoscopy
• Necropsy
Treatment
• Fenbendazole or avermectins
Other Control Measures
• Isolate infected animals and dispose of their vomit and feces
• Keep dogs from eating beetles, paratenic hosts as much as
possible
Public Health Significance
• None

6. Habronema musca, H. microstoma
(STOMACH WORM OF HORSES)
Definitive Host Spectrum
– Equine species
Intermediate Host
– Houseflies ( Musca domestica ), stable flies ( Stomoxys
calcitrans )
Geographic Distribution
– Worldwide
Morphology
– Adults - males up to 22 mm, females up to 35 mm;
cylindrical buccal cavity
– Eggs - thin-shelled, larvated, 40-50 x 10-16 microns

7. Life Cycle (Stages)
• Larvae or eggs are passed in feces and are ingested by
maggots
• Larvae develop to L 3 in synchrony with maggots'
development to adult flies
• L 3 move out of the fly via the proboscis as the fly feeds on
the DH's lips, nostrils or wounds
• Horses also become infected when they ingest infected flies
in food or water
• Larvae mature in the stomach.
• Note: L 3 must be ingested and reach the stomach to mature;
otherwise, only cutaneous infection occurs
• Prepatent period - 2 months

8. Sites of Infection
– Stomach, on the mucosa ( Habronema ) - adults
– Skin, in cutaneous granulomas - larvae
– Lungs, in fibrotic nodules - larvae
Pathogenesis/Clinical Signs
– In the stomach - creates lesions on the stomach
mucosa
– It may cause chronic gastritis.
Cutaneous habronemiasis
– Also called "summer sores" - lesions appear in warm
weather, heal spontaneously in winter, reappear in
spring
» Larvae cause large, perhaps multiple,
granulomatous lesions which are painful and
pruritic

9. » lesion on the membrane or the skin around the eye
» Rarely, a mass of granulation tissue involving the
entire conjunctiva
– In the lungs - nodular peribronchitis
Diagnosis
» Eggs or L 1 are rarely found on fecal exam - do not
float very well (direct smear is possible)
» Eggs or L 1 may be found by gastric lavage
through a stomach tube
» Xenodiagnosis - feed IH maggots on feces,
examine later for larvae
Cutaneous infections
» History
» Gross appearance - circular
» Biopsy may reveal larvae

10. Treatment
• Stomach infections - moxidectin, ivermectin
• Cutaneous infections - ivermectin, surgical removal
Other Control Measures
• Eliminate or reduce fly breeding sites - dispose of
manure, straw, bedding
• Apply repellents
Public Health Significance
• None

11. Thelazia spp. (EYEWORM)
Definitive Host Spectrum
– Cattle, sheep, deer, horses, canids, felids, rabbits,
humans
Intermediate Host (Vector)
– Flies (Musca, Fannia)
Geographic Distribution
– Worldwide
Morphology
Adults - males up to 12 mm, females up to 20 mm; anterior
end has serrated cuticle

12. Life Cycle (Stages)
– Larvated eggs or L 1 are laid by females
– Flies ingest L 1 while feeding on lachrymal secretions
– Development in the fly for 15-30 days
– L 3 migrate to the mouthparts of the fly and infect the
DH as the fly feeds
– Prepatent period - probably about 6 weeks
Sites of Infection
– Conjunctival sac, lacrimal and nasolacrimal ducts,
under the nictitating membrane
Pathogenesis/Clinical Signs
– Seasonal due to the fly vectors
– The serrated cuticle of eyeworms causes lacrimation,
conjunctivitis, photophobia, and without treatment
ulceration of the cornea

13. Diagnosis
– Gross observation of the adults in the eye; eggs or L 1
in lacrimal secretions
Treatment
– Removal of the adults with fine forceps, under local
anesthesia
– Irrigation with Lugol's iodine or 2-3% boric acid
following removal or for parasites that are in the
lacrimal ducts where they cannot be removed
manually
– Levamisole, either orally or parenterally at 5 mg/kg (is
shed in lacrimal secretions), or 2 ml injected into the
conjunctival sac
Other Control Measures
– Difficult, but can try insecticides for fly control
Public Health Significance
– Humans can be infected with this parasite

14. Gongylonema spp.
Definitive Host Spectrum
– Ruminants, pigs, equids, birds, humans
Intermediate Host
– Coprophagous beetles, cockroaches (Blatella)
Geographic Distribution
– Worldwide
Morphology
– Adults - males up to 62 mm, females up to 145 mm;
cuticle of the anterior end has many round or oval
thickenings called "bosses"
– Eggs - thick-shelled, larvated, 50-70 x 25-37 microns

15. Life Cycle (Stages)
– Eggs are passed in feces, ingested by IH (beetles,
cockroaches)
– Development to L 3 in IH
– DH ingests IH
– Larvae probably migrate from the stomach to the oral
cavity then into the wall of the esophagus
– Prepatent period - about 8 weeks
• Sites of Infection
– Esophagus and/or rumen, woven into the wall in a
zigzag pattern
– In humans - oral epithelium or subcutaneously
– In birds - crop

16. Pathogenesis/Clinical Signs
– Usually nonpathogenic; perhaps some inflammatory
reaction
Diagnosis
– Usually found incidentally post mortem
Treatment
– None known
Public Health Significance
• Human infection has been reported