Anti-parasitic drug could speed up the elimination of infections that are endemic in Africa

Anti-parasitic drug could speed up the elimination of infections that are endemic in Africa

Tens of millions of people in Africa are infected by parasitic worms that cause lymphatic filariasis (also called elephantiasis), a disease that causes severe swelling and deformity of the limbs and genitals. Despite widespread treatment programs that have successfully reduced the risk of lymphatic filariasis, hundreds of millions of people remain susceptible to the infection.

A small clinical trial in Cote d'Ivoire led by researchers at Washington University School of Medicine in St. Louis shows that the anti-parasitic drug moxidectin—currently approved to treat river blindness, another tropical disease caused by parasitic worms—also for lymphatic filariasis than the current gold standard is more effective. Because moxidectin has a sustained effect in most treated individuals, fewer rounds of treatment may be required compared to annual treatment for ivermectin for at least five years, suggesting the possibility of accelerating clearance of the infection in Africa.

This study appears May 6 in the Lancet Infectious Diseases.

Moxidectin really works much better than the drugs we currently use for lymphatic filariasis. The fact is that in most of Africa, lymphatic filariasis and onchocerciasis or river blindness are co-endemic and you really need a drug that works well for both. “

Philip Budge, MD, PhD, associate professor of medicine in the Division of Infectious Diseases at Washu Medicine and senior author of the study

The experiment was carried out in collaboration with the Center Suisse de renherches Scientifique in Côte d’Ivoire. Lymphatic filariasis is endemic to many African countries, and it is estimated that more than 26 million people are infected in Cote d'Ivoire alone. The parasite that causes the disease, Wuchereria bancrofti, is spread by mosquitoes.

River blindness, which causes itching, rashes, skin bumps, and visual impairment (if left untreated can lead to permanent blindness), is endemic in many of the same countries as lymphatic filariasis. Both diseases have been coordinated by global elimination programs by the World Health Organization (WHO). For lymphatic filariasis, delivering anti-parasitic drugs to nearly 1 billion people is the Mass Drug Administration's largest infectious disease initiative to date. In addition to limb swelling, lymphatic filariasis can increase patients' risk of contracting other diseases such as malaria, tuberculosis and HIV/AIDS.

Typically, people need to receive annual doses of ivermectin and another anti-parasite drug, albendazole, for five years to completely clear the infection. The aim of this study was to determine whether moxidectin, a new river blindness drug that is superior to ivermectin in controlling this disease, might be a better option in combination therapies for the treatment of lymphatic filariasis.

Participants in the study - all adults aged 18 to 70 - had high blood levels of microfilariae, the larvae of adult worms. Those with high levels are considered infectious and contribute to the continued spread of this disease.

The study included four treatment groups, each receiving combinations of moxidectin or ivermectin with one or two other drugs commonly used to treat parasitic worm infections.

After 12 months, 18 of 19 participants in the group receiving moxidectin and another drug (albendazole) had cleared their infections, compared with 8 of 25 in the ivermectin plus albendazole group. After 24 months, 14 of 16 participants in the moxidectin group remained microfilariae-free.

Among participants who received either ivermectin or moxidectin in combination with two other medications, 21 of 23 people in the moxidectin group were parasite-free after 24 months, while 20 of 22 participants in the ivermectin group cleared their infections over the same period. The finding suggests that one dose of moxidectin and another drug is as effective as moxidectin or ivermectin combined with two other drugs.

“If you treat someone with moxidectin, they are more likely to clear their parasites for longer,” Budge said. "With ivermectin, people need to be treated multiple times. So in the global elimination program, the right place for moxidectin is in people who are repeatedly difficult to reach."

Budge explained that many people missed by Mass Drug Administration programs are difficult to dose because they live in remote villages.

Medicines Development for Global Health, a non-profit pharmaceutical company in collaboration with the UNICEF/UNDP/World Bank/WHO Special Program for Research and Training in Tropical Diseases (TDR), developed moxidectin for human use.

“The best possible outcome for this work would be for moxidectin to be used in Mass Drug Administration programs,” Budge said. "That would shorten the number of years it takes us to achieve lymphatic filariasis elimination. There are hundreds of millions of people who will not have this disease in the future if we can eliminate it, and moxidectin can potentially help speed up that process."

Sources: