Bancroftian filariasis is caused by the parasitic roundworm, Wuchereria bancrofti. The parasite is responsible for ~90% of lymphatic filariasis cases worldwide [1]; its wide range spans across tropical and subtropical regions of Africa, Asia, the Pacific, and the Americas, including Haiti [2]. The juvenile roundworms are known as microfilariae, and they circulate in an infected person’s blood, where they are ingested by a mosquito upon taking a blood meal. The microfilariae develop into stage 3 larvae and penetrate the mosquitoes mouthparts during a blood meal, where they drop off onto their human host. The larvae then enter the skin through penetrating into the bite wound. Once developed, adult worms reside in the lymphatics, where they reproduce, releasing millions of microfilariae into the blood stream [3]. Adult worms may live up to 8 years [4], and pathology is caused by damage to the lymphatic system. This can result in lymphedema from fluid build up, elephantiasis from skin thickening and secondary infections [3, 4]. The major mosquito vector genera are Culex across the Americas, Anopheles across Africa and Aedes in the Pacific islands [3]. Transmission is influenced by several factors including the density of microfilaria in the blood of infected persons, the number of infected persons (prevalence) and the behaviour of the mosquito vector including frequency of human-vector contact [3, 5]. All of these make lymphatic filariasis fairly inefficient and require a mosquito to bite many times for burden to increase.
- World Health Organisation. Lymphatic filariasis factsheet: Epidemiology. 2019. Available at http://www.who.int/lymphatic_filariasis/epidemiology/en/
- MSD Manuals: Professionals version. Bancroftian and Brugian Lymphatic Filariasis. March 2019. Available at https://www.msdmanuals.com/en-gb/professional/infectious-diseases/nematodes-roundworms/bancroftian-and-brugian-lymphatic-filariasis
- Centers for Disease Control and Prevention. Lymphatic Filariasis: Biology, Disease and Epidemiology. October 2018. Available at https://www.cdc.gov/filarial-worms/about/lymphatic-filariasis.html?CDC_AAref_Val=https://www.cdc.gov/parasites/lymphaticfilariasis/
- Shenoy RK. Clinical and pathological aspects of filarial lymphedema and its management. Korean J Parasitol. 2008 Sep;46(3):119-25. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2553332/
- Ottesen EA. The global programme to eliminate lymphatic filariasis. Tropical Medicine & International Health. 2000 Sep;5(9):591-https://onlinelibrary.wiley.com/doi/full/10.1046/j.1365-3156.2000.00620.x