Loiasis: An Unusual Cause of Eosinophilia in a Pediatric Patient.

Abstract

To the Editors: A 9-year-old girl from Equatorial Guinea with spastic tetraparesis and ventriculoperitoneal shunt due to congenital hydrocephalus for which she was periodically checked in Barcelona, Spain, was referred to our department because of eosinophilia. Her family lived in Malabo but had also stayed in the continental part of Equatorial Guinea and had no relevant previous history. The patient was asymptomatic and no new significant findings were found on physical examination. A blood count revealed eosinophilia (eosinophil count, 1600 eo/μL) with mild IgE elevation (IgE, 374 KUI/mL). Biochemistry and iron studies were normal, and allergy screening, Schistosoma/Strongyloides serologies and coproparasitologic studies were negative. Additional serologies including Echinococcus granulosus, Fasciola hepatica, Taenia solium and Toxocara canis were also negative. The microscopic microfilarial study in blood revealed 2 microfilariae/mL (8:30 am), later identified as Loa loa (Fig. 1). The test was repeated at 12 am to accurately quantify microfilaremia, which showed a significant increase in L. loa parasites (132/mL). Provided that coinfection with onchocerciasis could not be excluded and that L. loa parasitemia was low, a single dose of ivermectin 150 μg/kg orally was administered. After this initial management, loiasis was treated with 21 days of diethylcarbamazine (DEC) (progressive ascending dosage up to 9 mg/kg/d). The resolution of eosinophilia and L. loa parasitemia was later confirmed.FIGURE 1.: Microfilaria of Loa loa in a thick blood smear, stained with hematoxylin (100×).L. loa is a nematode responsible for a filariasis transmitted by tabanids of the genus Chrysops endemic in Angola, Chad, Democratic Republic of the Congo, Cameroon, Central African Republic, Equatorial Guinea, Gabon, Nigeria, Republic of Congo and South Sudan.1 The 2 main clinical manifestations are the “Calabar edema” due to a hypersensitivity reaction to the subcutaneous parasite migration, and the “eye worm,” which is the adult form migrating under the bulbar conjunctiva.1,2 Pruritus is also frequent. Nonetheless, a significant number of patients may only present eosinophilia, mild nonspecific symptoms or no symptoms at all.3 Although it has been traditionally considered a “benign” infection, it has recently been associated with an excess mortality rate4,5 and a broad range of vital organ involvement in patients with high microfilaremia.2 The diagnosis is based on the visualization of microfilariae using a blood concentration technique (Ho Thi Sang method with saponin) and subsequent staining of a smear with hematoxylin, extracting blood samples at midday in view of the diurnal periodicity of microfilariae circulation in peripheral blood. First-line medicine is DEC, which acts against both microfilariae and adult worms.3 Before starting the treatment, it is compulsory to exclude onchocerciasis coinfection—in patients coming from areas where both filariasis occur—providing that DEC could cause blindness or disease exacerbation in these cases. Besides, patients with high microfilaremia (>2500/μL) are at risk of encephalopathy after DEC or ivermectin administration. In these cases, a prior course of albendazole should be considered to reduce microfilarial load. This case shows the importance of loiasis screening in patients coming from an endemic country if eosinophilia is present. Universal screening of all pediatric patients coming from endemic areas is still not recommended according to the literature.