LOA LOA
LOA LOA (AFRICAN EYE WORM)
• Loa Loa is a filarial nematode.
• It was first detected in 1770 in the eye of a patient in Santo
Domingo, Dominican Republic.
• The adult worm measures 30–70mm in length and 0.30.5mm in thickness.
• Microfilariae are sheathed with a column of nuclei extending
to the tip of the tail.
EPIDEMIOLOGY
• The parasite is endemic to forests of west and central
Africa.
• A few cases have been reported in the US but are
restricted to travelers who have returned from endemic
countries
LIFE CYCLE
• The life cycle is completed in 2 hosts.
1) Intermediate Host : Chrysops Flies
 Chrysops ingest microfilariae, which penetrate the stomach walls to
reach the thoracic muscles.
 The microfilariae then develop into 3rd stage larvae which migrate to
the fly’s head and proboscis.
1) Definitive Host : Human Beings
 During feeding, the Chrysops flies transfer the larvae to humans.
 Larvae enter the subcutaneous tissue where they molt into adult
worms within a period of 6-12 months.
 The female adults produce microfilariae, which can be ingested by
Chrysops during their blood meal, setting up another cycle.
PATHOGENESIS
• Once fully developed, the adult worms wander through the subcutaneous
tissue of the infected person causing inflammation (swelling).
• Swellings within the subcutaneous tissue are known as Calabar/Fugitive
swellings.
 They are temporary and disappear within a few days.
 They however reappear at other sites following the movement of the worm.
 The swellings mostly appear on the limbs and are up to 3cm in size.
• Movement of the worm through the subconjuctival tissue causes:
 Ocular granuloma.
 Painless edema of the eyelids.
 Proptosis (exophthalmos).
• The worm can also on rare occasions attack deeper tissues leading to:
neuropathy, encephalopathy and cardiomyopathy.
•
Calabar swelling and eye invasion
DIAGNOSIS
• Infection can be determined by:
1.The presence of fugitive (disappearing) swellings.
2.Detection of microfilariae in peripheral blood.
 Loa Loa microfilariae can only be detected in blood from 12
noon to 2pm (diurnal periodicity).
3. Isolation of adult worm from the eye, skin or subcutaneous
biopsy specimen of the patient.
TREATMENT
A.DEC (Diethylcarbamazine)
 The dosage is usually 8-10mg/Kg daily, for 21 days.
 Should be used with caution as adverse reactions may develop
following sudden death of large numbers of microfilariae.
•
A.Corticosteroids
 Administered to minimize adverse reactions following death of
microfilariae.
A.Ivermectin and Albendazole
 Are effective for treatment though not approved by the FDA.
Prevention
1. Wearing long sleeved shirts and long pants when
visiting an infested area.
2. Diethylcarbamazine 300mg taken once a week can
help prevent infection.
references
• Paniker ’s Textbook of Medical Parasitology
• .https://my.clevelandclinic.org/health/diseases/4696-trichomoniasis
• James, William D.; Berger, Timothy G. (2006). Andrews' Diseases of the Skin:
clinical Dermatology. Saunders Elsevier. ISBN 978-0-7216-2921-6.
Control of foodborne trematode infections. Report of a WHO Study
Group. World Health Organ Tech Rep Ser. 1995;849:1-157
https://www.ncbi.nlm.nih.gov/books/NBK532892/
https://www.cdc.gov