Foot measurement of a lymphatic filariasis patient in Sukala, Satyavadi, Puri district, Odisha, India.
› The helminth worms responsible for causing parasitic
disease in animals and humans are classified into three species – roundworms or nematodes (including filarial worms and soil-transmitted helminths), flatworms, and flukes. Filarial worms are spread by blood-feeding insect vectors, and invade different parts of the human body causing chronic disease. Wucheria bancrofti, Brugia malayi, and B. timori adult worms invade the lymphatic system, and Onchocerca volvulus and Loa loa form deep tissue and subcutaneous nodules. Onchocerciasis is predominantly found in West and Central Africa where it causes river blindness, so-called because the black flies which spread disease breed in f ast-flow ing rivers and streams, and can produce blindness af ter many year s of chronic infection. Before large control programmes started, blindness was highly prevalent in villages along rivers infested with blackflies, leading to the abandonment of fertile land, and increased poverty. An estimated 37 million people are infected with O. volvulus worms, which cause severe itching and may result in blindness or impaired vision.
for LF and onchocerciasis control programmes using preventive mass drug administration (MDA) chemotherapy, as serious adverse events can occur in co-infected patients. MDA pr ogr amme s depend on donations fr om pharmaceutical companies, and although the drugs are effective in killing the different juvenile worms (microfilariae) of the O.volvulus, W. bancrofti, and Brugia worms, they do not kill adult worms (macrofilariae) which continue to reproduce during most of their long lifespan. MDA chemotherapy therefore needs repeating once or twice annually for over a decade. A short-course treatment that kills adult worms is needed to cure patients, and may also be useful in reducing the number of cycles of MDA to achieve disease control or elimination.
Treatments are needed for juvenile as well as adult worms
DNDi is aiming to develop a safe and effective fieldadapted macrofilaricidal drug with its partners, based on drugs used to treat animal helminth infections. A parallel approach is to target Wolbachia, a symbiotic intracellular bacterium present in Onchocerca, Wucheria, and Brugia worms, aiming to identify drugs which kill the Wolbachia and impact worm survival and reproduction. The year 2015 was a defining one for filarial diseases. In October, one half of the Nobel Prize for Medicine was awarded jointly to William Campbell and Satoshi Omura for their discovery of the antifilarial drug ivermectin, used in MDA programmes. Meanwhile, the 20-year old African Programme for Onchocerciasis Control, considered to be one the most successful public health initiatives ever, closed at the end of the year. While both milestones bear testament to the progress made in treating these diseases, millions of people remain affected and in need of a curative treatment.
Lymphatic filariasis (LF) is more widespread, found in tropical areas principally in Africa and Asia. Worms migrate to the lymph glands, resulting in swollen limbs and genitals, a disabling, painful, and highly stigmatizing affliction. Over 67 million people are infected and over 36 million are estimated to be clinically affected by the symptoms. Loiasis, also known as African eyeworm because of the migration of the adult worm through the conjunctiva, has less direct impact, with symptoms not considered to be as severe. But loiasis infection has important implications
DNDi Annual Report 2015 › 41