Download T. canis - Posters On Demand 2009

Diffuse Unilateral Subacute Neuroretinitis
with Visualized Ocular Larva Migrans
Shane McEntire M.D., Suzie T. Nemmers M.D., Jason Sorell
D.O., John D. Campagna M.D. MPHTM, Natasha Nemeth
M.D.
Tripler Army Medical Center, University of Hawaii
The views expressed in this poster are those of the authors and do not reflect the official policy or
position of the Department of the Army, Department of Defense or the U.S. Government.
None of the authors have any commercial or financial interests.
Purpose
To describe the uncommon findings of a visualized larva
attributed to Toxocara canis in ocular larva migrans.
Background



Human T. canis infections have been reported in nearly all parts of
the world, primarily in temperate and tropical areas where dogs
are popular household pets. Young children are at highest risk
because of their unsanitary play habits and tendency to place
fingers in the mouth.
T. canis larvae secrete large amounts of immunogenic glycosylated
proteins which induce immune responses that lead to eosinophilia
and polyclonal and antigen-specific immunoglobulin E (IgE)
production.
There are 3 major clinical syndromes associated with human
toxocariasis: visceral larva migrans, ocular larva migrans, and
covert toxocariasis.
Background
The ocular disease may appear in a number of ways, the
most common being in the form of a dense white
granuloma in the posterior pole or retinal periphery
where the larva has encysted.
 Patients may have a more marked inflammation that
may simulate DUSN and endophthalmitis, probably due
to massive antigen release by dying organisms.
 The pathology of toxocariasis consists of granuloma
formation with a predominance of eosinophils.
 The actual identification of a larva may require multiple
sections of the tissue.
 Visualization on retinal exam is uncommon.

Case
A 33 yo man who returned from Iraq noted blurred
vision and photophobia in his left eye. Exam noted a
uveitis with granuloma keratic precipitates, a retinal
granuloma of the left eye, and choroidal retinal scars
of both eyes possibly attributed to toxoplasmosis.
 He was treated initially with Pred-forte. Due to
failure to respond, lab analysis was performed which
showed a positive result for Toxocara canis,
eosinophilia, and negative for toxoplasmosis.
 Subtenon steroid injections were initiated followed
by oral steroids and albendazole 400 mg bid for five
days. After regression of the retinal granuloma, a
nonmotile nematode larva was visualized.

OS
Overlay
demonstrating
location
Visualized larva of T. canis
Surrounding granuloma
Discussion

Eyes that have active inflammation require treatment
with systemic or periocular corticosteroids. If the eye
disease is not responsive to corticosteroids, parasitic
infection should be considered. Parasitic infection with
Toxocara canis is uncommon and visualization of larva is
difficult to discern. Toxocariasis can present as
neuroretinitis thereby delaying diagnosis.
References

Glickman LT, Schantz PM: Epidemiology and pathogenesis of zoonotic
toxocariasis. Epidemiol Rev 1981; 3:230.

Walls KW, Schantz PM, ed. Immunodiagnosis of Parasitic Diseases, Vol 1,
Helminthic Diseases, New York: Academic Press; 1986:201-231.

Tropical Medicine and Emerging Infectious Diseases, 8th ed. Chapter 112

Cohen & Powderly: Infectious Diseases, 2nd ed.