Onchocerchosis, commonly known as river blindness or gold miners’ disease, is a parasitosis caused by the parasite Onchocerca volvulus, this disease is transmitted by the bite of the fly of the genus Simulium spp., also known as black fly or rubber mosquito, due to its similarity to mosquitoes, which are normally found on the banks of the river.
The main clinical manifestation of this disease is the presence of the parasite in the eyes, resulting in progressive loss of vision, so onchocercosis is also known as river blindness; however, onchocercosis can remain asymptomatic for years, making it difficult to diagnose.
- The life cycle of Onchocerca volvulus occurs in both flies and humans.
- The cycle in humans begins when the insect feeds on blood.
- Releasing infectious larvae into the bloodstream.
- These larvae undergo a maturation process.
- Reproduce and release microfilariae.
- Which spread in the blood and reach various organs.
- Where they develop.
- Give rise to symptoms and begin a new life cycle.
Flies can become infectious when they bite a person who has microfilariae in their blood, because at feeding, they end up ingesting the microfilariae, which in the intestine become infectious and go to the salivary glands, being possible infection of other people during blood feeding.
The release of microfilariae by adult larvae takes about 1 year, i.e. symptoms of onchocercosis do not begin to appear until after 1 year of infection and the severity of symptoms depends on the number of microfilariae.In addition, adult larvae are able to survive in the body between the ages of 10 and 12, with the female able to release around 1000 microfilariae per day, with a lifespan of about 2 years.
The main symptom of onchocerciasis is progressive loss of vision due to the presence of microfilariae in the eyes, which, if left untreated, can lead to blindness. Other characteristic clinical manifestations of the disease are:
In addition, there may be lymphatic lesions, in which microfilariae can reach the lymph nodes near skin lesions and cause damage.
Early diagnosis of onchocerchosis is difficult because the disease can be asymptomatic for years, diagnosis is made through the symptoms of the person, in addition to the tests requested by the doctor that help confirm the diagnosis, such as eye exams and blood tests in which microfilariae are sought among the red blood cells , in addition, the doctor may request an ultrasound, to check the formation of nodules by the parasite, and molecular tests, such as PCR, to identify Onchocerca volvulus.
In addition to these tests, your doctor may order a histopathological exam, biopsying a small piece of skin to identify microfilariae and rule out other conditions, such as adenopathies, lipomas, and sebaceous cysts, for example.
The treatment of onchocercosis is performed with the use of the antiparasitic ivermectin, which is very effective against microfilariae, as it is able to cause death without causing very serious side effects.Learn how to take ivermectin.
Although very effective against microfilariae, ivermectin has no effect on adult larvae and nodules containing adult larvae should be surgically removed.
The best way to prevent Onchocerca volvulus infection is to use repellents and appropriate clothing, especially in areas where the insect is most prevalent and in riverbeds, as well as mosquito control measures, such as the use of biodegradable larvicultes and insecticides, for example.
In addition, it is recommended that people living in endemic areas or people who have remained in these areas be treated with ivermectin once a year or rather annually to prevent onchocerchosis.