Gastrointestinal Spirurid Parasites of the Dog and Cat

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Gastrointestinal Spirurid Parasites of the Dog
and Cat
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Physaloptera spp.
Physaloptera is a spirurid nematode that occurs
in the stomach and (less commonly) the duodenum
of dogs, cats and various wild carnivores. It is
reported mainly from the midwestern states where
up to 20 incidence can occur . Physaloptera is
of rare occurrence in domestic dogs and cats in
other areas. Intermediate hosts are crickets,
flour beetles, ground beetles and cockroaches.
Several species are thought to occur in dogs and
cats in the U.S.
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Histosection of Physaloptera in gastric mucosa
Physaloptera spp. are attached to the gastric
mucosa where they cause erosions at the point of
attachment, gastritis and excess mucous
formation. They feed largely on blood. Catarrhal
gastritis, vomiting, and loss of condition have
been reported. Confusable with ascarids.
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Anterior and posterior end of Phvsaloptera
A very characteristic collar-like cervical alae
occurs at the anterior end of the sexes of
Physaloptera. Males of Physaloptera have spicules
and very large caudal alae as compared to other
spirurids. Females have straight tails. The above
two slides illustrate characteristics which can
be used to differentiate this parasite from
ascarids which are of about the same size.
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Eggs of Physaloptera spp.
Stool examinations may reveal oval,
thick-shelled, embryonated eggs (49 x 58 by
30-34). For treatment of Physaloptera, literature
and informal practice reports indicate efficacy
by Dichlorvos (TASK), Fenbendazole (20mg/kg for
5 days) and pyrantel pamoate (5mg/kg twice, 3
weeks apart).
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Spirocerca Lupi
Spirocerca lupi is a Spirurid parasite that is
found in the esophagus, stomach, and aorta of the
dog and wild canidae such as the coyote, fox, and
wolf . Spirocerca is found in most warm countries
of the world and in the United States it occurs
primarily in the Southeast. The worms are robust,
about 4-5 cm in length, and are red in color .
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Arthropod Intermediate Hosts
Various species of coprophagous beetles (dung
beetles) serve as intermediate hosts for
Spirocerca lupi. Ova passed in the feces of
infected dogs hatch after ingestion by a suitable
dung beetle, develop to infective third stage
larva, and encyst in the insect's tissues.
Infected dung beetles are then ingested by the
definitive host, the dog, or anyone of a large
number of transport hosts.
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Transport or Paratenic Hosts
An exceptionally wide variety of animals can
serve as transport hosts, including various
birds, small mammals amphibians, and reptiles.
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Migration Pattern in the Definitive Host
After ingestion, encysted larvae penetrate the
wall of the stomach, and migrate in the
adventitia of the arteries of the stomach to the
thoracic aorta over a three week period.
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Regional Anatomy
This slide illustrates the close proximity of the
thoracic aorta to the esophagus and thoracic
vertebrae. Most worms migrate (as shown by the
arrow) to the wall of the esophagus by traversing
the connective tissue or the walls of small
arteries. The parasite penetrates completely to
the esophageal lumen and then withdraws back into
the esophageal wall. This establishes a fistulous
communication for later passage of ova to the
lumen. Worms generally do not migrate from the
aorta to the esophagus until the third month. The
final molt to the adult stage also occurs at
about this time. Worms are usually in the
esophageal wall by the end of the third month and
here they cause the formation of a granuloma of
variable size. Patency occurs in 5-6 months.
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Esophageal Granuloma
Considerable reaction occurs due to the presence
of Spirocerca in host tissues. Esophageal
granulomas formed vary from small nodular
swellings to large pedunculated masses (as seen
here).
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Ossifying Spondylitis
Ossifying spondylitis sometimes occurs in
adjacent thoracic vertebrae, apparently due to
irritation by migrating larvae.
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Aortic nodules and aneurisms
During the time that parasites are normally in
the aorta, or if parasites are arrested in the
aorta during migration, they may cause the
formation of small nodules or larger, more
diffuse granulomas and aneurisms which can
rupture leading to fatal extravasation into the
abdominal cavity.
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Ectopic sites
As with most migrating parasites, abnormal sites
are sometimes reached. Worms may be arrested
somewhere along the normal migration route or
they may migrate in the wrong vessel or tissues
and reach ectopic sites such as the stomach shown
here.
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Associated Sarcoma and Hypertrophic Pulmonary
Osteoarthropathy
Finally, there is a strong association of
Spirocerca with a malignant osteosarcoma or
fibrosarcoma. The majority of Spirocerca
infections are not clinically apparent and are
usually noted at necropsy. Only a small
percentage of cases develop sarcomas. The extent
of malignant lesions which can develop are seen
in this radiograph. (Dense or radiopaque areas).
Ossifying spondylitis involving the thoracic
vertebrae can also be seen in this radiograph.
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Factors leading to malignancy Reasons for the
development of Spirocerca sarcomas are poorly
understood. It is postulated that metabolic
products or some agent carried by this worm
interact with host tissues to stimulate
neoplasia. Genetic predisposition appears to play
a role in the case of hound breeds. Malignancy
is most common in older dogs gt 5 years old.
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Hypertrophic Pulmonary Osteoarthropathy
If malignancy develops, a common sequela is
hypertrophic pulmonary osteoarthropathv (a
thickening of the distal long bones associated
with a space occupying lesion in the thorax). The
dog seen here is severely affected with
hypertrophic pulmonary osteoarthropathy (HPO)
associated with a thoracic sarcoma. HPO can also
occur with large thoracic granulomas due to
Spirocerca. Note the formation of less dense
new bone on preexisting dense cortical bone.
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Clinical Signs
Clinical signs associated with Spirocerca
infections depend on where major lesions develop.
A large granuloma may cause persistent vomiting.
Aortic aneurisms may rupture and lead to sudden
death by extravasation. If malignancy occurs, a
wide variety of symptoms may occur depending on
the location of the primary neoplasm or
metastases. A thorough knowledge of the life
cycle of Spirocerca is necessary for diagnosis of
disease by this parasite.
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Epidemiology
The slide illustrates the general distribution of
reported Spirocerca sarcoma in the Southeast.
Incidence of simple Spirocerca infection would
follow a similar distribution. Bailey at Auburn
recorded an 8 infection rate in Alabama in a
survey between 1951 and 1963, but only 2 from
1963-1970. Georgia surveys show less than 1 of
the dogs infected. Bailey considered the feeding
of uncooked intestinal tracts of chickens to be a
primary source of infection for dogs . Incidence
of Spirocerca has decreased in recent years due
to better care of dogs, the shift to confinement
poultry operations, and reduction of dung beetle
numbers by large scale use of agricultural
insecticides.
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Diagnosis and Treatment

• Diagnosis can be made by
• Clinical signs and history
• Radiography with contrast media
• Endoscopy
• Stool examination
• NaNO3 Flotation (1.36 specific gravity) -
  Sugar and NaCl solutions are less effective.

Treatment Disophenol 1 ml/10 lb. for 10 days is
effective against adult worms.
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Egg of Spirocerca lupi
Note the small size, thick wall and larvae. A
whipworm egg is also present. Recovery of eggs is
dependent on a patent opening to the lumen of the
digestive tract and therefore ova are not
consistently found. Spirocerca worms do not live
more than a few years and lesions do not always
contain worms at necropsy.