Loiasis: New Epidemiologic Insights and Proposed Treatment Strategy

Abstract

Among the two cases of loiasis published in this issue,1,2 one particularly deserves to be commented on because it is atypical in some respects.1 The patient was an expatriate who had an upper eyelid swelling from which a nematode was extracted. During the preceding 2 years, he had had transient swellings at various sites of the head, and at referral his eosinophilia was normal and no microfilaria (mf) was found in his blood. No serologic or polymerase chain reaction (PCR) assays were performed on blood samples. The parasite removed has not been examined morphologically to seek classical characteristics of adult Loa loa (cuticle with numerous, randomly arranged, smooth, round bosses); but the real‐time PCR assay performed on a piece of the worm demonstrated unambiguously that it was a L loa specimen. The first interesting point in this case is that the patient reported to have visited sub‐Saharan Africa only once for a business trip, 20 years before the extraction of the worm. Unlike Onchocerca volvulus or Wuchereria bancrofti (the most pathogenic human filariae), the average lifespan of adult L loa has never been evaluated. However, it is known that the parasite can live more than 10 years,3 the record reported so far being 17 years.4 The possibility that the patient presented in this report had been infected elsewhere than in Africa could be considered: experimental infections using monkey models have shown that at least one American Chrysops species supports the development of L loa up to the infective stage, and could thus theoretically retransmit the parasite locally after having taken a bloodmeal on an infected individual.5 However, this is rather unlikely (as stated by Orihel and Lowrie,5 no report exists of Loa establishment in America, even at the height of the slave trade) and … Corresponding Author: Michel Boussinesq, MD, PhD, Unite Mixte Internationale 233, Institut de Recherche pour le Developpement, 911 avenue Agropolis, BP 64501, F‐34394 Montpellier Cedex 5, France. E‐mail: michel.boussinesq{at}ird.fr