Post-treatment Effects of Ivermectin (IVM) or Diethylcarbamazine (DEC) in Loiasis

Overview

Background: * Loa loa is a small worm that infects people in West and Central Africa. It is spread by the bite of a fly. Adult worms live under the skin and can cause swelling in the arms, legs, and face. Some people have more serious infections in the heart, kidneys, or brain. Most people with Loa loa infection have no symptoms at all. The standard treatment for Loa loa infection is a medicine called diethylcarbamazine (DEC). Some people have bad reactions to DEC, including itching, muscle pains, and in severe cases coma and death. * Another drug, ivermectin, is used in mass drug treatment programs to prevent the spread of worm infections that cause blindness and massive swelling (elephantiasis). However, people who also have Loa loa have had serious bad reactions to ivermectin. Researchers want to study both DEC and ivermectin to find out why these reactions occur. If they can be prevented, mass drug treatment programs will be able to be used in areas in Africa where Loa loa exists. Objectives: \- To study the side effects of DEC and ivermectin treatment for Loa loa infection. Eligibility: \- Individuals who live in 4 villages in Cameroon where Loa loa infection is known to exist, who are between 20 and 60 years of age, not pregnant or breastfeeding and have a low level of Loa loa parasites in the blood, but are otherwise healthy. Design: * Participants will be screened with a physical exam and medical history. Blood samples will be collected to check for Loa loa infection. Participants will also have an eye exam and provide skin samples to check for other worm infections that may interfere with the study treatment. * Participants will be admitted to the hospital for 4 days (during and after the treatment). They will receive a single dose of either DEC or ivermectin. * After treatment, regular blood samples will be collected. Participants will be asked questions about how they feel after treatment. Physical exams will be performed. If side effects develop, participants will be treated at the hospital. * After leaving the hospital, participants will have followup visits. These visits will happen on days 5, 7, 9, and 14 after receiving the study medicine. They will involve a short physical exam and collection of blood samples. * At the end of the study, participants will be offered a full 21-day DEC treatment to cure the Loa loa infection.

Ivermectin is currently used for mass drug distribution for the control of onchocerciasis and elimination of lymphatic filariasis in Africa. Due to the occurrence of severe neurologic adverse events in individuals with concomitant Loa loa infection and high levels of circulating microfilariae, drug distribution has been halted in many areas in Cameroon, Democratic Republic of Congo and other Loa-endemic countries. Diethylcarbamazine citrate (DEC) is the treatment of choice for Loa loa infection in the United States and other non-endemic countries, but can also be associated with the development of severe adverse reactions, including fatal encephalopathy, that are correlated with the number of circulating microfilariae in the blood. The cause of these reactions is unknown, and it is not known if post-treatment reactions to DEC and ivermectin both have the same underlying mechanism. Post-treatment reactions to both medications are accompanied by a dramatic interleukin-5 (IL-5)-dependent increase in eosinophilia and evidence of eosinophil activation. Preliminary data suggests that, unlike post-treatment responses in Wolbachia-containing filariae, inflammatory mediators commonly seen in bacterial infections and malaria, including tumor necrosis factor (TNF)-alpha and IL-1-beta, are not increased post-treatment with DEC. The aim of this study is to characterize the immunologic mechanisms of ivermectin and DEC posttreatment reactions so that it can be established whether or not these posttreatment reactions have the same underlying mechanism. An understanding of the pathophysiology of these post-treatment reactions is necessary in order to develop strategies to prevent these reactions in the future. We plan to randomize 20 subjects with low- to- moderate numbers of circulating Loa loa microfilariae to receive a single oral dose of either ivermectin (200 mcg/kg) or DEC (8 mg/kg) in an inpatient setting in Cameroon. Signs and symptoms, blood microfilarial levels, complete blood counts, intracellular and serum cytokine levels and markers of eosinophil activation will be assessed at baseline, 4 and 8 hours, and 1, 2, 3, 5, 7, and 9 and 14 days post-treatment and compared between the two treatment groups. Subjects who received ivermectin will be treated with single dose DEC (8 mg/kg) on day 14. All subjects will then be followed at 6 and 12 months post-hospitalization to determine whether they have experienced Loa-specific symptoms (eyeworm or Calabar swellings). Mf count and complete blood count (CBC) with differential will be obtained at each follow-up visit. Subjects with Loa-specific symptoms or mf counts \> 100 mf/mL at the 6 month time point will be offered a full treatment course. If \> 50% of subjects meet criteria for full DEC treatment at the 6, month time point, all subjects will be treated and the study will enter a follow-up phase with a visit at 12 months (6 months after the full treatment course ).