Ocular Toxocariasis 2012

2. A 12-year-old female presented with
sudden onset of diminished vision and
redness of right eye to a private
practitioner who diagnosed her as a
case of acute iridocyclitis.
She was treated with topical mydriatic
(atropine) and topical corticosteroid
(dexamethasone).
Redness of eye improved but
diminution of vision progressed for
which she consulted the department of
ophthalmology at our Government
medical college.

3. HISTORY: There was no history of
ocular trauma or ocular ailment in
past.
O/E: Her general physical and
systemic examination was normal.
Left eye had vision of 6/6 and was
normal on examination. Right eye
had vision of hand movements
close to face and ciliary congestion.
Slit lamp bio microscopic
examination showed exudates in
vitreous cavity. Fundus
examination revealed yellowish
reflex in pupillary area, with hazy
media.
The patient is admitted for further
evaluation.

4. • Leucocoria (also leukokoria or white pupillary
reflex) is an abnormal white reflection from the
retina of the eye.
• Leukocoria resembles eyeshine, but leukocoria can
occur in humans and other animals that lack
eyeshine because their retina lacks a tapetum
lucidum.
• Because of the potential life threatening nature of
retinoblastoma, this condition is usually considered
in the evaluation of leukocoria.

5. Differentials
Leucocoria is a medical sign for a number of
conditions, including:
• Coats disease,
• congenital cataract,
• corneal scarring,
• melanoma of the ciliary body,
• Norrie disease,
• Ocular toxocariasis,
• persistence of the tunica vasculosa lentis (PFV/PHPV),
• retinoblastoma,
• and retrolental fibroplasia.

6. • It is an infestation caused by an intestinal
roundworm of dogs (Toxocara canis) and cats
(Toxocara catis).
• Mostly young children who play with dogs and cats
or eat dirt are infested by the ova of these worms.
• These worms then develop into larva in the human
gut, and produce:
covert toxocariasis
visceral larva migrans
ocular larva migrans

8. Life cycle/Parasitology
Toxocara canis accomplishes its life cycle in dogs, with humans acquiring the infection as
accidental hosts. Unembryonated eggs are shed in the feces of the definitive host . Eggs
embryonate and become infective in the environment . Following ingestion by dogs , the
infective eggs hatch and larvae penetrate the gut wall. In younger dogs, the larvae migrate
through the lungs, bronchial tree, and esophagus; adult worms develop and oviposit in the
small intestine . In older dogs, patent infections can also occur, but larval encystment in
tissues is more common. Encysted stages are reactivated in female dogs during late
pregnancy and infect by the transplacental and transmammary routes the puppies , in
whose small intestine adult worms become established. Puppies are a major source of
environmental egg contamination. Toxocara canis can also be transmitted through ingestion
of paratenic hosts: eggs ingested by small mammals (e.g. rabbits) hatch and larvae penetrate
the gut wall and migrate into various tissues where they encyst . The life cycle is completed
when dogs eat these hosts and the larvae develop into egg-laying adult worms in the small
intestine. Humans are accidental hosts who become infected by ingesting infective eggs in
contaminated soil or infected paratenic hosts . After ingestion, the eggs hatch and larvae
penetrate the intestinal wall and are carried by the circulation to a wide variety of tissues
(liver, heart, lungs, brain, muscle, eyes) . While the larvae do not undergo any further
development in these sites, they can cause severe local reactions that are the basis of
toxocariasis. The two main clinical presentations of toxocariasis are visceral larva migrans
and ocular larva migrans. Diagnosis is usually made by serology or the finding of larvae in
biopsy or autopsy specimens.

10. • Ocular infestation by the larva causes ocular
toxocariasis and is almost always UNILATERAL.
Toxocariasis
Covert Visceral Ocular
Toxocara chronic
endophthalmitis
Posterior pole
granuloma
Peripheral
granuloma

11. • It presents with
leucocoria due to
marked vitreous
clouding.
• Most common
among age group
of 2 – 10 years and
mimics
RETINOBLASTOMA

12. • Presents as a
yellow-white,
round, solitary,
raised nodule,
about 1-2 disc
diameter in size,
located either at
the macula or in the
centro-caecal area.
• Occurs in the age
group between 5
and 15 years of age.

13. • It is situated anterior to the equator.
• May be associated with vitreous band formation.
• Presents from 6 – 40 years of age.

14. Two separate patients with
peripheral granulomas due to
ocular toxocariasis. Note the
prominent, posteriorly extending
retinal folds and, in case A,
extensive exudate.
Two separate patients (A and B)
with healed posterior pole
granulomas due to ocular
toxocariasis. Note the prominent
retinal folds and epiretinal
membrane formation.

15. • Her routine investigations were within normal limits. Vitreous sample showed no microorganism on Gram staining and
KOH preparation. Both bacterial and fungal cultures were sterile.
• The patient was treated with topical gatifloxicin 0.3% (one drop six hourly), dexamethasone 0.1% (one drop two
hourly) and atropine sulphate 1% (one drop three times a day). The patient also received two intravitreal injections of
ceftazidime 2.25 mg/0.1 mL and vancomycin 1 mg/0.1 mL.
• Repeat indirect ophthalmoscopy revealed faint glow and organized exudates in vitreous, thus, possibility of mass in
mid-vitreal cavity or posterior pole granuloma was kept and a B-scan was advised, which revealed multiple echogenic
dot-like opacities of low-to-medium amplitude in mid-and posterior vitreous cavity. In view of high spike in mid-vitreal
cavity on B-scan, a differential diagnosis of right intraocular foreign body was raised and CT scan was advised to rule
out intraocular foreign body and retinoblastoma.
• With this clinical presentation, possibility of ocular toxocariasis was kept in mind. Antibodies specific to Toxocara
purified ES antigen were detected in serum, aqueous and vitreous sample by enzyme-linked immunosorbent assay
(ELISA) and treated with vitreo-retinal surgery.

16. Made on the basis of clinical
picture and ELISA blood test.

17. Medical
• Periocular (posterior sub-tenon) injection of
steriod and systemic steriods.
Surgical
• For unresponsive patients with
endophthalmitis and vitreous band formation:
• Pars plana vitrectomy

18. Most cases of isolated elevated granulomas of the disc or retina are
due to Toxocara.
Virtually all cases of toxocariasis in the United States come from pets.
When suspecting ocular toxocariasis, attempt to elicit a history of
exposure to puppies and soil.
While the systemic form is typically unnoticed and produces no
permanent damage, a similar nematode found in raccoons can also
infect humans and is much more virulent.

19. Bibliography
• Department of Ophthalmology, Chengalpattu
Government Medical College;
• Parson’s textbook of Ophthalmology, Pg. 371;
• A K Khurana’s Comprehensice Ophthalmology, Pg.
164;
• My Parents;
• And as always, Wikipedia and Google search
engine.