Mapping Of Loa Loa Filariasis In Africa

Sept. 9, 2011, 1:05 p.m.


By Linda Diep

Loa Loa worm


Mapping of Loa Loa Filariasis (also known as loiasis) could help in the innovation of new strategies to eliminate and control onchocerciasis (river blindness) and lymphatic filariasis (LF), according to a recently released article from the open-access journal PLoS Neglected Tropical Diseases. The study found that mapping — a systematic method used in public health to monitor and track the pattern of a disease — could prove to be an effective way to help develop treatment for loiasis.

In African countries, an estimated 14 million people reside in the most high risk areas of loiasis, a disease that affects the skin and eyes causing itchiness, swelling, and pain. Loiasis is caused by the parasitic worm Loa Loa, and is transmitted through a bite from the African deer fly. Many sufferers of loiasis are also co-infected with river blindness and LF. In the past, co-infected individuals who have taken ivermectin, a drug used in the treatment of river blindness and LF, have experienced severe adverse neurological effects such as encephalopathy, which can put lives in danger.

Mapping of loiasis can address this issue. Identifying areas where cases of the disease are most prevalent can help dictate where ivermectin can be used for river blindness and LF treatment, or where usage of the drug should be avoided. The mapping will also be conducive to implementing one of the most widely-used approaches for eliminating river blindness – community-directed treatment. This approach uses volunteers within communities to collect ivermectin from local health facilities. The volunteers then decide how, when, and where to distribute the drug. Using the map to identify areas with low to nil prevalence of loiasis will serve as an effective tool in implementing community-directed treatment.

This new global map was developed from actual survey data, a first for loiasis mapping. Environmental risk models (used in risk assessment) were used to shape older maps, resulting in maps that were not always precise. This new map was created using a rapid assessment procedure specifically created for loiasis called RAPLOA. Developed by UNICEF, UNDP, World Bank, and WHO Special Programme for Research and Training in Tropical Diseases (TDR), RAPLOA uses questionnaires to survey the presence and history of loiasis in thousands of selected villages. The development of RAPLOA was assisted by funding from the WHO’s African Programme for Onchocerciasis Control (APOC), who is also responsible for the data collection involved in the mapping, and is continually providing the maps to the 11 countries that have frequent cases of loiasis.

New innovations and advancements such as the mapping of loiasis will soon lead to the control and elimination of NTDs, allowing for improved quality of life for billions of individuals.

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