Category Archives: Onchocerciasis

The Americas is One Step Closer to Eliminating Onchocerciasis

 

Less than a year after Colombia eliminated onchocerciasis from its borders, its neighboring country, Venezuela, is making similar strides in the fight against neglected tropical diseases (NTDs). Earlier this month, we were excited to hear that Venezuela interrupted transmission of onchocerciasis in its last remaining focus area of the country – meaning Venezuela is well on its way to being certified for eliminating this painful and disfiguring disease.

Onchocerciasis is the world’s fourth leading cause of preventable blindness. As one of the seven most common NTDs, onchocerciasis primarily affects poor populations living along rivers. Infection occurs when black flies carrying the filarial parasitic worm Onchocerca volvulus bite humans. After the larvae enter the body, develop into adult worms, and eventually die, the disease progresses to cause severe skin rashes and depigmentation, visual impairment and blindness. Control efforts in the both the Latin American and African regions are focused on eliminating this NTD as a public health concern.

If you can recall, six countries in the region of the Americas were previously endemic to onchocerciasis: Brazil, Colombia, Ecuador, Guatemala, Mexico, and Venezuela. Through the concerted efforts of the ministries of health of the endemic countries and the local communities, the Onchocerciasis Elimination Program for the Americas (OEPA), the Carter Center, the Pan American Health Organization (PAHO), and Merck & Co., 11 out of the 13 foci had achieved control of this NTD by 2013. The two remaining foci are found in the border region between Venezuela and Brazil, specifically in the migrant Yanomami indigenous community.

Francisco Armada, Venezuela’s Minister of Health, announced the interruption of transmission on World Health Day last week. The People’s Ministry of Health of Venezuela (MPPS) and the PAHO country office will now begin the three-year surveillance stage. If no new cases are found during the three years, Venezuela can begin the process for certifying the elimination of onchocerciasis. Minister Armada also reaffirmed the government’s commitment to Brazil to continue working together to reach the joint goal of onchocerciasis elimination in the region.

Colombia was the first country in the Americas to receive verification of the elimination of this NTD from the World Health Organization (WHO). Ecuador has completed the three-year surveillance phase and Guatemala and Mexico are close to completing it – after this phase, they will be able to request verification of elimination from WHO. The progress demonstrated in the Latin American and Carribbean region is encouraging.

We congratulate Venezuela on this success and look forward to following the country’s – and the region’s – progress towards onchocerciasis elimination!

A Test For River Blindness

 

A boy helps Samuel Nicol, (age unknown) who suffers from onchocerciasis, walk through the village of Gbonjeima, Sierra Leone. Olivier Asselin, 2012.

A boy helps Samuel Nicol, (age unknown) who suffers from onchocerciasis, walk through the village of
Gbonjeima, Sierra Leone. Olivier Asselin, 2012.

Re-posted from Greg Laden’s Blog on ScienceBlogs

River blindness, also called Onchocerciasis, is the result of the infection of several different eye tissues by the nematode Onchocerca volvulus. The bacterium Wolbachia pipientis lives symbiotically in the gut of the nematode, and escapes the small roundworm to cause an inflammatory response in human tissues, which results in damage to the tissue. These infections can occur in a number of different human tissues causing a variety of effects, but when the eye tissues are involved, the result can be river blindness. It is endemic and widespread in several areas of Africa, as well as more restricted areas in South America and the Middle East.

Treatment of the disease involves killing the bacterium, which in turn kills the host nematode, using various anti-biotics. However, as we have learned over recent decades, widespread use of antibiotics can be less than ideal because this can cause selection for resistant strains so that treatment can become generally ineffective across an affected population. Ideally, there would be a reliable test for river blindness infection that would allow more targeted use of treatments.

A research team at Scripps has just published a paper in PNAS that may lead to such a treatment. The team examined urine samples from people who are known to be infected with the nematode Onchocerca volvulus and its attending Wolbachia pipientis bacterium with those who were not thought to be so infected. A massive laboratory based hunt for differences in the contents of the urine was carried out, and one molecule was identified as unique to the infected humans. This was N-acetyltyramine-O,β-glucuronide, which started out as a neurotransmitter found in the nematodes while they are young, which is then converted to N-acetyltyramine-O,β-glucuronide in the human body and eventually secreted in the urine.

The nematode has a somewhat complex lifecycle in which the very young worms infect various tissues and reproduce there, causing the damage to the tissue via the bacterium’s release. This neurotransmitter seems to be unique, or nearly unique, to these young worms. This is important because the nematode is probably widespread in humans in the endemic areas, but as relatively dormant adults found here and there throughout the body. It is only the young reproducing worms that cause the river blindness. Therefore, N-acetyltyramine-O,β-glucuronide specifically identifies individuals at risk of tissue damage to the eyes.

The test is not yet ready for prime time. There needs to be a field test that can be administered easily in conditions where there are only minimal or no clinical facilities. The test materials have to be reasonably inexpensive and not require special handling such as refrigeration. Ideally, this would consist of a urine test strip as have been developed in the past to test for blood sugar levels or pregnancy.

Another important outcome of this finding is the method itself, which the researchers have dubbed “Metabolome-mining.” (The term “metabolome” refers to the full set of metabolites to be found in a particular organism or tissue, similar to the term “genome” for the full set of genes.)

More information will be available at the Scripps Research Institution web site.

Globisch, D, Moreno, A, Hixon, M, Nunes, A., Denery, J., Specth, S., HYoerauf, A, & Jand, K (2013). Onchocerca volvulus-Neurotransmitter Tyramine is a Biomarker for River Blindness PNAS

Keeping score: Will the new NTD Scorecard keep global action on track?


By Simon Bush,
Director of Neglected Tropical Diseases at Sightsavers. See his recent article in the Huffington Post here.

Today sees the publication of an NTD Scorecard which will bring further transformation to the way global partners, from endemic governments, and pharmaceutical companies to NGOs, are working together to achieve the elimination of this group of debilitating diseases.

Developed by the London Declaration partners and published alongside From Promises to Progress, a new report on NTDs, the Scorecard will help translate the aspirational vision of elimination of ten of the NTDs by 2020 into a reality.

When I first started working on NTDs 13 years ago, I never would have imagined progress like this. Elimination of NTDs such as blinding trachoma and river blindness (onchocerciasis) seemed such a distant goal. How things have changed!  We are now seeing promises turn into action which will make a colossal difference to the lives of over a billion people who are affected by NTDs.

The Scorecard sets out the strategic milestones that are crucial if we’re going to see real progress on these ten NTDs – in terms of raising funds, conducting research and development, and ultimately delivering the right number of treatments, to the right people, in the right communities. It’s all about achieving the scale-up needed. Continue reading

NTD Success Story: Guatemala Eliminates Onchocerciasis Transmission in Huehuetenango

Another battle in the fight against neglected tropical diseases (NTDs) has been won in Guatemala, where onchocerciaisis transmission has been eliminated in Huehuetenango.

A recent article in the Journal of Parasitology Research evaluated onchocerciasis transmission in the department of Huehuetenango in western Guatemala after 22 rounds of mass drug administration (MDA) over 13 years. In 2007-2008, prevalence of infection was determined to be zero percent through eye examinations of residents, antibody detection in school children and parasite detection in black flies. Following the results of this evaluation, mass treatment was halted in 2009 and post treatment surveillance of parasite prevalence in black flies was conducted from 2009-2011. Infection remained at zero percent, validating that transmission had been eliminated in the area.

Onchocerciasis, also known as river blindness, is caused by the parasite Onchocerca volvulus and is transmitted to humans by the bite of black flies. Infection with the parasite can produce nodules, inflammation, discoloration and itching of the skin, as well as lesions that can lead to blindness. Onchocerciasis is found in 37 countries across the world.

The Onchocerciasis Elimination Program of the Americas, or OEPA, was established in 1992 with the goal of supporting national programs in LAC countries to provide twice yearly MDA of ivermectin to a minimum of 85 percent of the eligible population at risk. The Guatemala Ministry of Public Health, with the assistance from OEPA, began MDA for onchocerciasis in 1996, and since 2002 has reached the targeted coverage of the eligible population through twice-yearly MDA. There were four endemic foci for onchocerciasis in Guatemala. Before this study, transmission in two of the four foci had already been declared eliminated. With this recent evidence of elimination in Huehuetenango and with post treatment surveillance being conducted in the fourth foci, Guatemala is well on its way to request the WHO certification of nation-wide elimination in 2015.