Generally, patients recovered from SAE within 6–7 months post-Ivermectin treatment; however, when their complications were unmanaged and patients were left bed-ridden, death resulted due to gastrointestinal bleeding, septic shock, and large abscesses.Mechanisms for SAE have been proposed. Though microfilarial load is a major risk factor to post-Ivermectin SAE, three main hypotheses have been proposed for the mechanisms.The first mechanism suggests that Ivermectin causes immobility in microfilariae, which then obstructs microcirculation in cerebral regions. This is supported by the retinal hemorrhaging seen in some patients, and is possibly responsible for the neurologic SAE reported.The second hypothesis suggests that microfilariae may try to escape drug treatment by migrating to brain capillaries and further into brain tissue; this is supported by pathology reports demonstrating a microfilarial presence in brain tissue post-Ivermectin treatment.Lastly, the third hypothesis attributes hypersensitivity and inflammation at the cerebral level to post-Ivermectin treatment complications, and perhaps the release of bacteria from L. loa after treatment to SAE. This has been observed with the bacteria Wolbachia that live with O. volvulus.More research into the mechanisms of post-Ivermectin treatment SAE is needed to develop drugs that are appropriate for individuals with multiple parasitic infections.One drug that has been proposed for the treatment of onchocerciasis is doxycycline. This drug has been shown to be effective in killing both the adult worm of O. volvulus and Wolbachia, the bacteria believed to play a major role in the onset of onchocerciasis, while having no effect on the microfilariae of L. loa.
These microfilariae are 250–300 μm long, 6–8 μm wide and can be distinguished morphologically from other filariae, as they are sheathed and contain body nuclei that extend to the tip of the tail. Lifecycle
The vector for Loa loa filariasis originates with flies from two hematophagous species of the genus Chrysops (deer flies), C. silacea and C. dimidiata. During a blood meal, an infected fly (genus Chrysops, day-biting flies) introduces third-stage filarial larvae onto the skin of the human host, where they penetrate into the bite wound. The larvae develop into adults that commonly reside in subcutaneous tissue. The female worms measure 40 to 70 mm in length and 0.5 mm in diameter, while the males measure 30 to 34 mm in length and 0.35 to 0.43 mm in diameter. Adults produce microfilariae measuring 250 to 300 μm by 6 to 8 μm, which are sheathed and have diurnal periodicity. Microfilariae have been recovered from spinal fluids, urine and sputum. During the day, they are found in peripheral blood, but during the noncirculation phase, they are found in the lungs. The fly ingests microfilariae during a blood meal. After ingestion, the microfilariae lose their sheaths and migrate from the flys midgut through the hemocoel to the thoracic muscles of the arthropod. There the microfilariae develop into first-stage larvae and subsequently into third-stage infective larvae. The third-stage infective larvae migrate to the flys proboscis and can infect another human when the fly takes a blood meal.