Loa Loa


  • Caused by Loa Loa

  • AKA eye worm

  • Epidemiology: West Africa

  • Life-cycle: Chrysops fly

  • Clinical: adults in subcutanous tissue (), microfilariae migrate around

  • Diagnosis: blood film (nuclei go 'lower and lower')

  • DEC etc.

What is LL?

  • Tissue nematode infection, microfilarial infection

  • Infected larvae of LL transmitted by the Chrysops fly which breeds in swamps (W/C Africa) (some overlap with Onco)

  • Usually results from years of exposure e.g. primatologist

  • Develop into adult worms in human host

  • adult worms migrate through (like LF, not Onc)

  • Symptoms from adult worm migrating through s/c and connective tissues, can be front, or under eye (eye worm)

What are the clinical features of Loa Loa?

  • Asymptomatic?

  • Calabar swelling: s/c non-tender, non-itch swellings, intermittent swellings from worm migration

  • Eye worm: passes through bulbar sub-conjunctiva.. can take 30min-24 hours (pathopneumonic**)

Other systemic sx:

  • chronic fatigue, inc.

  • Cardiomyopathy: SVTs, pericardial effusions..EMF

  • nephropathy (GN, nephrotic syndrome)

  • encephalitis meningoencephalitis… (esp. post-DEC)

What is the differential diagnosis of skin swellings & eosinophilia?


  • Loa Loa (calabar)

  • Cysticercosis

  • Larva currens (Strongyloides)

  • Mansonella

  • Katayama fever (urticarial rash)

  • Gnathostomiasis (Asia)

  • Sparganosis (Asia)

  • Angiostrongylus


  • Non-specific urticaria

  • Vasculitis (panniculitis?)

How is LL diagnosed?


  • Flitting s/c/ swellings & eosinophilia

  • Eye worm (ONLY LOA LOA)


  • Eosinophilia (>0.45)

  • Serology (not specific for LL)

  • Day bloods (c/w/ LF): look for adult worms (mf)

  • Sheathed mf, nuclei in tail? (produced by adult worms)

How is LL treated?

  • Not usually needed

  • Surgical removal?


  • only effective drug to kill adult worms

SE’s if treat with high mf load

  • GN

  • Encephalopathy

  • Death

  • Risk of Mazotti reaction if have Onco (must do skin snip)… if Onco, treat it first e.g. Doxy

Drugs to reduce mf load, pre-DEC: Albendazole, Ivermectin:

mf >8000

  • albendazole 200mg BD 21 days, then…

  • Ivermectin 150 mag/kg… then

  • DEC slowly


  • ivermectin 150-200 mpg stat.. then…

  • DEC low dose


  • start DEC low-dose and titrate up

What is the issue with Onco and LL?

  • Ivermectin bad if Loa Loa (meningoencephalitis)

  • DEC bad if Oncho (Mazotti reaction)

How is LL prevented?

  • Same zone as Oncho eradication programmes

  • Ivermectin risk of precipitating severe encephalitis in patients with high mf Loa Loa load e.g. 0.1%

  • PH importance of Loa Loa concerned with Oncho eradication programmes: not done in these regions


  • rural C/W africa

  • worm inf. via chrysops fly

  • Sx: eye worm, calabar swellings or asymptotic

  • D: E0, serology, day bloods mf

  • rx: DEC curative, problems if concurrent Oncho or mf

  • Problem: Ivermectin for oncho causes problems if concurrent Loa Loa (difficult for control programmes)


Case 1: DM

  • E0

  • Calabar swelling

  • Niger river to sea in Nigeria..

  • Crysops fly.. forest..

  • mf dayblood

  • serology

treatment depends on mf’aemia’

  • low: DEC

  • mod: ivermectin

  • high:


96. Loa loa

a. is confined to Central and West Africa

b. is spread by the vector Aedes aegypti

c. may cause a high eosinophilia (>10x10^9/L)

d. is diagnosed by histological examination of skin snips

e. is treated with DEC

  • High eosinophilia is particularly suggestive of infection with filarial worms or strongyloidiasis.

  • The vector is Crysops.

  • The diagnosis is usually made by finding microfilariae in the blood. Adult worms are sometimes (dramatically) seen crossing the eye subconjunctivally. Adult worms are also located in the pathognomonic Calabar swellings.