Encephalopathy in a patient with loiasis treated with albendazole: A case report

Eosinophils, basophils and myeloid-derived suppressor cells in chronic Loa loa infection and its treatment in an endemic setting

BACKGROUND

Chronic infection by Loa loa remains an unsolved immunological paradox. Despite harboring subcutaneously migrating adult worms and often high densities of microfilariae, most patients experience only relatively mild symptoms, yet microfilaricidal treatment can trigger life-threatening inflammation. Here, we investigated innate cell populations hypothesized to play a role in these two faces of the disease, in an endemic population in Gabon.

METHODOLOGY/PRINCIPAL FINDINGS

We analyzed numbers and activation of eosinophils and basophils, as well as myeloid-derived suppressor cell (MDSC) subsets and associated circulating cytokine levels by flow cytometry in sex- and age-matched L. loa-uninfected (LL-), -amicrofilaraemic (MF-) and -microfilaraemic (MF+) individuals (n = 42), as well as microfilaraemic individuals treated with albendazole (n = 26). The percentage of eosinophils was lower in LL- (3.0%) than in the combined L. loa-infected population, but was similar in MF+ (13.1%) and MF- (12.3%). Upon treatment of MF+, eosinophilia increased from day 0 (17.2%) to day 14 (24.8%) and had decreased below baseline at day 168 (6.3%). Expression of the eosinophil activation marker CD123 followed the same pattern as the percentage of eosinophils, while the inverse was observed for CD193 and to some extent CD125. Circulating IL-5 levels after treatment followed the same pattern as eosinophil dynamics. Basophil numbers did not differ between infection states but increased after treatment of MF+. We did not observe differences in MDSC numbers between infection states or upon treatment.

CONCLUSIONS/SIGNIFICANCE

We demonstrate that both chronic infection and treatment of L. loa microfilaraemia are associated with eosinophil circulation and distinct phenotypical activation markers that might contribute to inflammatory pathways in this setting. In this first ever investigation into MDSC in L. loa infection, we found no evidence for their increased presence in chronic loiasis, suggesting that immunomodulation by L. loa is induced through other pathways.

The African eye worm: current understanding of the epidemiology, clinical disease, and treatment of loiasis

Loa loa, the African eye worm, is a filarial pathogen transmitted by blood-sucking flies of the genus Chrysops. Loiasis primarily affects rural populations residing in the forest and adjacent savannah regions of central and west Africa, where more than 20 million patients are chronically infected in medium and high transmission regions. For a long time, loiasis has been regarded as a relatively benign condition. However, morbidity as measured by disability-adjusted life-years lost might be as high as 400 per 100 000 residents, and the population attributable fraction of death is estimated at 14·5% in highly endemic regions, providing unequivocal evidence for the substantial disease burden that loiasis exerts on affected communities. The clinical penetrance of loiasis is variable and might present with the classic signs of eye worm migration or transient Calabar swellings, but might include common, unspecific symptoms or rare but potentially life-threatening complications. Although adult worm migration seems most closely linked to symptomatic disease, high levels of microfilaraemia are associated with clinically important complications and death. Loiasis remains difficult to diagnose, treat, and control due to an absence of reliable point-of-care diagnostic assays, safe and efficacious drugs, and cost-effective prevention strategies. This Review summarises the major advances in our understanding of loiasis made over the past decade and highlights the many gaps that await to be addressed urgently.

Motile microfilaria captured by fluorescent microscopy and the unmasking of eosinophilia following treatment

A 24-year-old patient from Cameroon presented to our hospital because of a foreign structure in her left eye. To our knowledge, for the first time, fluorescent microscopy revealed motile microfilariae, and the diagnosis of loiasis was established. Despite substantial microfilaremia, eosinophilia only unmasked after the initiation of antiparasitic therapy.

Loiasis from where you don't expect it: an illustrative case of misled diagnosis

In the absence of pathognomonic signs, the diagnosis of filarial infections relies on geographical exposure and morphology of microfilariae, which requires expertise. We present a case of loiasis in a patient not reporting exposure in areas of known Loa loa endemicity, whose diagnosis was achieved by molecular analysis of microfilariae.

Loa loa in the Vitreous Cavity of the Eye: A Case Report and State of Art

Loa loa is a filarial nematode responsible for loiasis, endemic to West-Central Africa south of the Sahara and transmitted by flies. This study reports a case of L. loa in the vitreous cavity of the eye of a young patient, along with an in-depth literature review. A 22-year-old woman from Cameroon who migrated from Cameroon to Italy was referred to the Emergency Ophthalmology Department at Policlinico di Bari in July 2021 with the presence of a moving parasite in the subconjunctiva of the left eye. A recent onset of a papular lesion on the dorsal surface of the right wrist and a nodular lesion in the scapular region were detected. L. loa filariasis was diagnosed based on anamnestic data, clinical and paraclinical signs, and a parasitological test confirming the presence of microfilariae in two blood samples collected in the morning of two different days. Because of the unavailability of diethylcarbamazine (DEC), albendazole (ALB) 200 mg twice daily was administered for 21 days. A mild exacerbation of pruritus occurred during treatment, but resolved with the use of an antihistamine. A single dose of 12 mg ivermectin was prescribed at the end of the treatment with albendazole. Unlike other endemic parasite infections, L. loa is not included in the Global Program to Eliminate Lymphatic Filariasis, because it is not mentioned in the WHO and CDC list of neglected tropical diseases. This can result in an overall risk of lack of attention and studies on loiasis, with lack of data on global burden of the disease.