Loiasis: Loa Loa, Tropical Swelling…

From my Tripler Files…  A 19 year-old female presented with tender swellings involving her lower legs and an uncomfortable sensation of movement involving her eyelids.  Her father was in the Air Force and they were stationed in Western Africa for three years…the family was also deployed.  Her father was then assigned to Hawaii where the symptoms developed.

On examination she had some ill-defined swellings along her lower extremities.  There was some mild swelling of her left upper eyelid.   Loa Loa infections are often asymptomatic and is also known as the Eye Worm.  The parasite develops slowly and up to 3 years may elapse before manifestations are noted.  The usual interval is one year.  The first signs are often painful, localized, subcutaneous, nonpitting edema called Calaber or Fugitive Swelling.  These swellings usually occur on the lower extremities, may be as large as a hen’s egg, and subside within a few days.

The Calabar swellings may be a hypersensitivity to the adult worm and many patients will develop an eosinophilia on blood testing.  It has a prediliction for loose tissues such as the eye region, the frenum of the tongue and the genitalia.  The wanderings of the adult parasite may result in a tingling and or creeping sensation.

ETIOLOGY:  Loiasis is distributed throughout West and Central Africa.  It is transmitted by the mango fly, Chrysops dimidia or Chrysops silacea.  The fly bites only in the daytime and humans are the only important reservoir for this filariae worm.  Demonstration of microfilariae in peripheral blood is seen in about 20% of patients and confirms the diagnosis.  Serologic tests are also available.

SURGICAL TREATMENT:  Removal of the adult parasite whenever it comes to the surface is mandatory.  This must be done quickly by grabbing the worm with a forceps and placing a suture under it before cutting down to it.  Worms that are not secured can escape into the deeper tissues.

TREATMENT:  Diethylcaramazine kills both adults and microfilariae and is given in increasing doses for 21 days and that is how we treated our patient.  In regions where onchocerciasis and loiasis are both endemic and where Ivermectin is used, simultaneous infections can result in serious side effects.  Diethylcarbamazine is also an effective form of prevention and using 300 mg/week in visiting residents where Loiasis is endemic is very effective.  To read more about Loiasis click HERE and HERE.