Loa loa (L. loa)

Loa loa is a filarial nematode parasite endemic to the rainforests of West and Central Africa, where it causes the disease loiasis, also known as African eye worm (CDC, 2020). The parasite is transmitted to humans via the bite of infected deer flies of the genus Chrysops (StatPearls, 2023). Once inside the host, adult worms migrate through subcutaneous tissues, often causing transient localized inflammatory edemas known as Calabar swellings (WHO, 2023). A hallmark of the infection is the visible migration of the adult worm across the subconjunctiva of the eye, which, while distressing, rarely causes permanent damage (NIH, 2022). Unlike other filarial parasites like Wuchereria bancrofti, Loa loa does not contain the endosymbiotic Wolbachia bacteria, meaning it cannot be treated with doxycycline (DNDi, 2021). The primary therapeutic challenge involves the use of diethylcarbamazine or ivermectin in patients with high microfilarial loads, as rapid killing of the larvae can trigger severe, life-threatening encephalopathy (PubMed, 2017). This safety concern significantly complicates mass drug administration programs for onchocerciasis and lymphatic filariasis in regions where Loa loa is co-endemic (WHO, 2023). Diagnosis typically relies on the identification of microfilariae in daytime blood smears or the clinical observation of subconjunctival worm migration (CDC, 2020).

Other names

African eye wormFilaria loaDracunculus loa

Diethylcarbamazine (DEC) inhibits arachidonic acid metabolism in microfilariae and the host, increasing parasite susceptibility to immune-mediated clearance (StatPearls, 2023). Ivermectin acts as an agonist at glutamate-gated chloride channels, leading to hyperpolarization and paralysis of the parasite (PubMed, 2017). Albendazole binds to parasite beta-tubulin, inhibiting microtubule polymerization and glucose uptake (CDC, 2020).