Onchocerciasis is a disease popularly known as " blindness In this article we will tell you all about this disease transmitted by the bite of a fly of the genus Simulium spp. So, learn more about it below!

What is river blindness?

To tell all about onchocerciasis, we talked to Dr. Vanessa Infante, infectologist at Hospital Santa Catarina (Paulista), and Dr. Luciana Galvão, infectologist at Hospital do Servidor Público Estadual (HSPE).

According to Dr Vanessa Infante, onchocerciasis is a parasitic disease caused by infection with the nematode (worm) Onchocerca volvulus , which settles in the subcutaneous tissue of those affected, and is more common in tropical regions.

How does transmission occur?

According to the infectologist at Santa Catarina Hospital (Paulista), onchocerciasis is transmitted by fly bite .

Dr. Luciana Galvão confirms that the parasite is transmitted to humans by the black, borrachuda, female fly, through the bite: "when the parasite is in its third larval stage," she adds.

What are the symptoms of onchocerciasis?

According to the infectologist, Dr Vanessa Infante, symptoms do not appear for up to one or two years after infection .

"When they appear, the most common symptoms are eye infections, which can lead to blindness. On the skin, there are rashes and subcutaneous swellings. In addition to itching, swelling of the ganglia or redness of the eyes ", he warns.

As a matter of fact, in Brazil and Latin America, the head, neck, shoulders, and upper extremities, as well as the eyes, are very much involved.

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Ocular Symptoms of Onchocerciasis

The infectologist at Hospital do Servidor Público Estadual (HSPE), Dr. Luciana Galvão, informs that the main clinical manifestations are ocular alterations:

• Acute keratitis (inflammation of the cornea);
• Sclerosing keratitis (chronic inflammation of the cornea and anterior chamber of the eye);
• Uveitis (inflammation of the posterior chamber of the eye);
• Optic atrophy (with optic nerve damage);
• Finally, oncorretinitis.

Therefore, the specialist reminds us that disease can cause partial and transient visual deficit (in cases of early diagnosis and treatment) or even blindness .

Symptoms of river blindness on the skin

The main skin manifestations are subcutaneous nodules (most are not palpable).

"These nodules correspond to the presence of the worms Only 10 to 12 months after the initial infection does the adult female start producing the microfilariae (offspring), which migrate to the subcutaneous tissue and eventually to all other parts of the body", informs Dr. Luciana Galvão.

Which test detects river blindness?

Dr. Luciana Galvão informs that skin biopsy (from the scapular region, iliac crest and calf) is the most effective exam to identify the disease, especially when there is the appearance of nodules or itching.

"The biopsy reveals the presence of motile microfilariae. The Mazzotti skin test, on the other hand, can be used in some circumstances," he comments.

Besides the above mentioned, serology (antibody detection), antigen testing (of the parasite), and polymerase chain reaction (PCR) are some tools, although they are not available in all places in the country: "Only specific reference laboratories perform them", he comments.

Finally, ultrasound of the subcutaneous nodules can be useful to identify the adult worms.

How is the treatment done?

The infectologist consulted informs that the basis is the treatment of the microfilariae (progeny), done with the drug Ivermectin (The treatment should be repeated every 3 to 6 months until the patient is asymptomatic, but the treatment time can last 10 years or more," he says. Wolbachia which lives in symbiosis with the adult worm.

The drug doxycycline, on the other hand, is active against Wolbachia and induces sustained sterility of the adult female worm. The dose is variable, but the duration of use should be at least six weeks.

"Doxycycline cannot be used for treatment in areas of continuous transmission, as new infections would require repeated courses of this medication. In this circumstance, repeated doses of Ivermectin are the best approach. Children will receive an alternative regimen," he mentions.

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How to prevent onchocerciasis?

Unfortunately, there is no vaccine for the prevention of river blindness However, international programs with the presence of the World Health Organization (WHO), the World Bank, and international collaborators operate in hotspot areas.

Thus, the doctor at the Hospital do Servidor Público Estadual (HSPE) informs that the use of aerial larvicide in rivers to control vectors, associated with the distribution of Ivermectin every 6 months, with the goal of covering at least 85% of the local population, are the bases for controlling the disease.

Remembering that transmission active is still present on the border of southern Venezuela and the northwestern Amazon in Brazil, rainforest where Yanomami people live. In this region, quarterly treatment with Ivermectin is used.

In addition, Dr Luciana Galvão comments that the Special Expanded Project for the Elimination of Neglected Tropical Diseases was established in 2016 for control of neglected tropical diseases, including onchocerciasis. The goal includes elimination of filariasis by 2020, and onchocerciasis by 2025.

Source: Dr. Vanessa Infante, infectologist at Hospital Santa Catarina (Paulista); Dr. Luciana Galvão, infectologist at Hospital do Servidor Público Estadual (HSPE).