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

1. Superfamily Ascaridoidea

2. Ascaridia spp. (LARGE ROUNDWORM OF BIRDS)
Definitive Host Spectrum
– Chickens, turkeys etc, wild birds
Intermediate Host
Earthworms paratenic hosts
Geographic Distribution
– Worldwide
Morphology
– Adults - varies by species, females
20-120 mm, males 16-76 mm; 3
lips
– Eggs - oval, with smooth shell, in
single cell stage when laid, 73-92 x
40-60 microns

3. Life Cycle (Stages)
– Eggs are passed in avian feces
– Develop to infective larvated eggs in 10 days or longer
– Infective eggs may be ingested by birds in contaminated
food or water or earthworms may ingest the eggs and in turn
be eaten by birds
– After ingestion and hatching, larvae remain in the lumen of
the intestine for about 8 days, then they spend some time in
the mucosa
– Larvae then mature to the adult stage
– Prepatent period - varies, depending on age of host, 5-6
weeks or up to 8 weeks
Site of Infection
– Small intestine

4. Pathogenesis/Clinical Signs
– Most serious in birds 1-3 months old
– Larvae penetrating the mucosa cause hemorrhage and
enteritis
– Clinical signs - diarrhea, unthriftiness, emaciation,
weakness, decreased egg production
Diagnosis
– Eggs in feces or worms at necropsy
Treatment
– Avermectins
– Piperazine compounds
– Benzimidazoles
– Levamisole

5. Other Control Measures
– Separate young birds from old
– Rotate poultry runs
– Use good ventilation, feeding and drinking troughs for
housed birds
– Compost litter
Public Health Significance
– None

6. Heterakis gallinarum (CECAL WORM)
Definitive Host Spectrum
– Chickens, turkeys, geese, ducks, wild birds
Intermediate Host
– Earthworms may serve as paratenic (transport) hosts
Geographic Distribution
– Worldwide
Morphology
Adults - small, males 7-13 mm, females 10-15 mm; lateral
alae
Eggs - ovoid, smooth-shelled, in single cell stage when
laid, 65-80 x 35-46 microns

7. Life Cycle (Stages)
– Eggs are passed in feces and become infective after the
infective larva develops within
– DH ingests the infective eggs directly or in an earthworm
paratenic host
– Larvae hatch in the intestine and reach maturity in the ceca
– Prepatent period - about 1 month
Site of Infection
– Ceca
Pathogenesis/Clinical Signs
– Thickening of the cecal mucosa and petechial hemorrhages
occur only in heavy infections
– Important economically as a carrier of Histomonas
meleagridis , the causative agent of "blackhead" of turkeys

8. Diagnosis
• Finding eggs in feces
Treatment
• Avermectins in feed
• Benzimidazoles in feed
• Levamisole in drinking water
Other Control Measures
• Good sanitation
Public Health Significance
• None

9. Parascaris equorum (LARGE ROUNDWORM OF HORSES)
Definitive Host Spectrum
– Equids
Intermediate Host
– None
Geographic Distribution
– Worldwide
Morphology
Adults - large, robust, males 15-28 cm, females up to 50 cm; the
3 lips are very conspicuous
– Eggs - almost spherical, brown, with a 1-celled zygote and
a thick pitted shell, 90-100 microns

11. Life cycle
» Very similar to Ascaris suum
» Eggs are passed in feces
» Larvated egg is infective when ingested while
grazing or suckling a contaminated udder
» After the larvae penetrate the intestine, they
migrate through the liver, heart, lungs to the
trachea and pharynx and are swallowed
» Maturation occurs in the small intestine
» Prepatent period - 10 to 12 weeks
Sites of Infection
» Small intestine, bile ducts - adults (can break out of
the gut and into the peritoneum)
– Liver, lungs - larvae

12. Pathogenesis/Clinical Signs
• Clinical effects usually seen only in foals 2-6 months old
(immunity develops by 6 months)
– Migration produces petechial hemorrhages,
eosinophilic infiltration in the liver, lungs
– Adults produce catarrhal enteritis, may cause
obstruction or perforation of the intestine or bile duct
– Clinical signs - coughing, dirty mucoid nasal
discharge, pot-bellied appearance, weight loss, poor
hair coat, weakness, fetid diarrhea that is pale in color,
flatulence
– Lab findings - eosinophilia, lower total body albumin
and serum albumin
Diagnosis
– Finding eggs, perhaps adults, in feces

13. Treatment
– Ivermectin
– Mebendazole
– Moxidectin
– Fenbendazole
– Febantel
– Oxibendazole
– Dichlorvos
– Pyrantel pamoate
– Piperazine compounds
Other Control Measures
– Good sanitation
– Clean foaling boxes, mare's udder
– Turn mare and foal out into clean paddock
– Collect manure and compost it or spread it on land not used
as horse pasture
Public Health Significance
– None

14. Superfamily Oxyuroidea
 Adults oxyuroides of animals inhabit the large
intestine.
 They are commonly called as pinworms
because of the pointed tail of the female
parasites.
 They have a double bulb oesophagus.
 The life cycle is direct.
 The only genus of veterinary interest is oxyuris
which is parasitic in the horse.

15. Oxyuris equi (HORSE PINWORM)
Definitive Host Spectrum
• Equids
Intermediate Host
• None
G. Distribution: Worldwide
Morphology
Adults - males 9-12 mm, females up
to 150 mm long; mature females
have long narrow tails which may
be more than 3 times as long as
the rest of the body
• Eggs - elongate, flattened on
one side, operculated, 85-95 x
40-45 microns

16. Life Cycle (Stages)
• Females travel to the rectum and out the anus to lay eggs
on the perianal skin
• Eggs usually are rubbed off or fall on the ground and
become infective
• Infective (larvated) eggs are ingested by a DH
• Eggs hatch in the small intestine and larvae pass to the
cecum where they feed on the mucosa
• Adults develop in the cecum, do not attach and are
probably scavengers of the cecal contents
• Prepatent period - 4 to 5 months
Sites of Infection
• Cecum, large colon; also rectum, perianal area for egg-
laying females

17. Pathogenesis/Clinical Signs
– The L 4 may produce inflammation of the cecal and
colonic mucosa by its feeding activity
– Eggs laid by female worms cause pruritis ani
– Clinical signs - restlessness, loss of condition, butt
rubbing, "rat tail"
Diagnosis
– "Rat tail" appearance is indicative of infection; eggs
may be seen by using scotch tape technique
• Because of their egg laying habits, adult females may be
seen in feces

18. Treatment
– Fenbendazole
– Dichlorvos
– Ivermectin, (will kill adults and larvae)
– Moxidectin
Other Control Measures
– Change bedding frequently
– Provide clean water
– Construct feed boxes so they will not be
contaminated by bedding
Public significance
– None