Ocular Loaloa filariasis

1. LOALOA FIL ARIASIS
( AFRICAN EYE WORM)
P R E S E N T E R : D. I D D I N D YA B AW E
M O D U L ATO R : D R . A M PA I R E A N N E
M AY 2 0 2 1

2. OUTLINE
• Introduction
• Prevalence and Incidence
• Etiology
• Primary Prevention
• Diagnosis
• Ophthalmic Signs and Symptoms
• Systemic Signs and Symptoms
• Laboratory test
• Differential diagnosis
• Management
-Medical therapy
-Medical follow up
• Surgery
-Subconjunctival filariasis
-Intraocular filariasis
• Prognosis
• References

3. INTRODUCTION
• An infection of the submucosal and subcutaneous tissue caused by the filarial nematode Loa
loa
• Eyeworm is a pathognomonic finding in the disease course
• Cutaneous manifestations including Calabar swellings are also pathognomonic
• Regarded as a benign condition???
• Risk of encephalopathy

4. PREVALENCE AND INCIDENCE
• More than 10 million people are affected by loiasis and over 14 million people
currently reside in high-risk areas.
• Loa loa is endemic to sub-saharan African countries including Angola, Cameroon,
Central African Republic, Chad, Congo, Democratic Republic of the Congo, Equatorial
Guinea, Ethiopia, Gabon, Nigeria, and Sudan.

5. ETIOLOGY
• Loa loa is transmitted by the deerfly of the Chrysops genus
• Microfilariae are sheathed and can be found in the spinal fluid, urine, sputum, lungs,
and blood of an infected individual.

6. PRIMARY PREVENTION
• Primary prevention is focused on reducing the near-constant exposure to the Chrysops
spp. vector in endemic regions
• Mass drug administration (MDA) programs

7. DIAGNOSIS
• Detection of the worm in the subconjunctiva of the eye or visualization of microfilariae
on blood smear in a patient from an endemic region or who has traveled to a high-risk
area
• Surgical removal of the worm from the subconjunctival space allows for laboratory
identification of the species.
• Calabar swellings may also help to confirm the diagnosis.

8. OPHTHALMIC SIGNS AND SYMPTOMS
• Symptoms: discomfort and foreign body sensation; pain and photophobia. Visual
loss (variable)
• Signs:
-In rare cases, L. loa has been noted to enter the anterior chamber, and live L. loa
have been reported in the vitreous.
-Slit lamp exam often reveals fibrinous membrane formation, cell/flare, and keratic
precipitates
-More prolonged cases may develop retinal detachments

9. SUBCONJUNCTIVAL ADULT LOA LOA WORM, BEFORE
AND AFTER SURGICAL REMOVAL FROM
SUBCONJUNCTIVAL SPACE

10. SYSTEMIC SIGNS AND SYMPTOMS
• Pathognomonic signs of loiasis include Calabar swellings and visualization of the adult
worm migrating through peripheral tissues.
• “Hyperresponsive syndrome”
• Variable presentation in travelers vs permanent residents in endemic areas

11. LAB TESTS
• Loa loa-specific biomarkers have been identified that can be used to differentiate Loa
loa infection from onchocerciasis and lymphatic filariasis
• ELISA antibody assays
• Recombinant antigen testing
• Loop-mediated isothermal amplification (LAMP)

12. DIFFERENTIAL DIAGNOSES
• Onchocerciasis
• Lymphatic filariasis
• Thelaziasis

13. MANAGEMENT
MEDICAL THERAPY
• Diethylcarbamazine (DEC): 1st DOC; 8-10 mg/kg three times per day for three weeks
• Albendazole
• Ivermectin
• Medical follow up:
-Patients should be followed closely for the first three days after initiation of treatment for
concern of Mazzotti reaction
• Surgery
-Surgical removal of adult worms from the conjunctiva of the eye is indicated whenever the
adult worm presents in the subconjunctival space

14. .
• Subconjunctival filariasis
• Procedure: the worm should first be
grasped externally with forceps to
prevent migration.
• Subsequent subconjunctival injection
of 2% lidocaine with epinephrine
1:100,000 can then be used to
simultaneously numb the region and
paralyze the worm.
• A peritomy generally ≤ 5 mm allows
access to the paralyzed worm, which
can then be removed with a second
set of forceps
• Intraocular filariasis
• An uncommon occurrence, which
presents with pain and foreign body
sensation.
• Anterior Chamber: Procedure:
Intracameral filarial worms may be
removed with an anterior chamber
washout, followed by a subconjuctival
injection of steroids and antibiotics
• Vitreous Chamber: One case report of
L. loa in the vitreous was effectively
treated with vitrectomy with steroid
cover

15. PROGNOSIS
• Visual acuity is generally not affected by the presence of adult worms in the
subconjunctiva, and lasting tissue damage is not generally seen
• Intraocular filariasis, however, can be much more devastating, with some patients
ending up NPL.
• Patient’s pre-operative presentation is strongly correlated with the postoperative
outcome

16. REFERENCES
• Sanders CJ, Jaspers CA. Onchocerciasis or loiasis? Lancet 2007; 369(9558): 271-2; author reply 2.
• Mitra A, Sen A, Agrawal T, Kohli G. Ocular filariasis: "Dancing sensation in the anterior chamber". Trop
Parasitol 2019; 9(1): 57-8.
• Rautaraya B, Tiwari S, Mahapatra A, Nanda A. Ocular filariasis. Trop Parasitol 2011; 1(2): 116-8.
• CDC. CDC - Parasites - Lymphatic Filariasis. October 22, 2018 2018.
https://www.cdc.gov/parasites/lymphaticfilariasis/index.html (accessed June 8 2020).
• Das D, Islam S, Bhattacharjee H, et al. Parasitic diseases of zoonotic importance in humans of
northeast India, with special reference to ocular involvement. Eye Brain 2014; 6: 1-8.
• Zakir R, Zhong-Xia Z, Chioddini P, Canning CR. Intraocular infestation with the worm, Thelazia
callipaeda. Br J Ophthalmol 1999; 83(10): 1194-5.
• Otranto D, Eberhard ML. Zoonotic helminths affecting the human eye. Parasit Vectors 2011; 4: 41.
• Krishnachary PS, Shankarappa VG, Rajarathnam R, Shanthappa M. Human ocular thelaziasis in
Karnataka. Indian J Ophthalmol 2014; 62(7): 822-4.
• Sah R, Khadka S, Adhikari M, et al. Human Thelaziasis: Emerging Ocular Pathogen in Nepal. Open
Forum Infect Dis 2018; 5(10): ofy237.
• Nayak B, Sinha S, Nayak L. Loa loa in the vitreous cavity of the eye. BMJ Case Rep 2016; 2016.
• Wahl G, Georges AJ. Current knowledge on the epidemiology, diagnosis, immunology, and treatment
of loiasis. Trop Med Parasitol 1995; 46(4): 287-91.