Onchocerciasis, or "river blindness", is a parasitic disease caused by microfilariae of worms of the genus Onchocerca, the most well-known of which is Onchocerca volvulus. These parasites are transmitted to humans through the bite of horseflies (symptomatic flies of the genus Simulium), which are found in tropical and subtropical regions. Infection results in a variety of clinical manifestations, including dermatological diseases, as well as eye lesions that can lead to complete blindness. Onchocerciasis is becoming a major public health problem, especially in west and central Africa, as well as in parts of Latin America and the Arabian Peninsula. Due to the high reproduction rate of the worm and its long latency period, onchocerciasis remains a challenge for both patients and health systems.
History of the disease and interesting historical facts
The history of onchocerciasis goes back to ancient times. The first documented case of the disease dates back to the 15th century, when cases of blindness were described in populations in Central Africa. Scientific study of the disease began in the late 19th century, when in 1875, German surgeon Alfred Wunderlich described the life cycle of Onchocerca volvulus. In 1974, a program to control onchocerciasis in West Africa, known as the African River Blindness Control Program, was initiated, which was one of the first examples of large-scale medical interventions at the public health level. Interestingly, treatment with ivermectin was introduced in 1987 and is currently the mainstay of disease control.
Epidemiology
Onchocerciasis is a global public health problem. The World Health Organization estimates that more than 25 million people are at risk of infection, and about 1.15 million suffer from severe forms of the disease. In countries where the disease is most prevalent, such as Nigeria, Somalia, and South Sudan, cases of primitive blindness caused by onchocerciasis have been observed. About 270,000 people suffer from blindness as a result of the infection, and another 500,000 have severe skin lesions. Prevalence differs slightly between men and women, but the risk of infection is increased in groups of people who work outdoors in endemic areas.
Genetic predisposition to this disease
At present, data on genetic predisposition to onchocerciasis are limited. Studies have shown that some human populations living in endemic areas have genetic stability associated with survival in endemic conditions. Specific genes, such as HLA-DRB1 and HLA-DQB1, may influence the immune response to infection. However, there are no clear mutations that confirm predisposition to the disease. Moreover, the presence of some immune response to helminth infections such as onchocerciasis may vary depending on the genetic combination and previous exposure to parasites.
Risk factors for the development of this disease
There are various risk factors for the occurrence of onchocerciasis. They include both biological and ecosocial aspects:
- Economic instability and poverty force people to work in dangerous conditions.
- Contact with fresh water where flies that carry the disease live.
- Lack of access to health care and preventive measures.
- Climatic conditions that promote the reproduction of simulids.
- Level of education and awareness of onchocerciasis prevention measures.
Diagnosis of this disease
Diagnosis of onchocerciasis involves several stages, from clinical examination to laboratory and radiological studies. The main symptoms of the disease include:
- Severe itching of the skin, eczema and skin lesions.
- A gradual deterioration of vision leading to loss of visual acuity and blindness.
- The appearance of tumors under the skin, known as "nostrils" or "onchocomas."
Laboratory tests include:
- Microscopy of skin biopsies to detect microfilariae.
- Serological tests to detect specific antibodies.
Radiological examinations such as ultrasound may help to identify intimate soft tissue changes and pathological processes associated with infection. The differential diagnosis should consider other causes of dermatological and ophthalmological disorders.
Treatment
Treatment of onchocerciasis usually involves a multifaceted approach. The mainstay of treatment is drug therapy with ivermectin. This is a safe and effective drug that kills microfilariae but does not kill adult worms. Surgery may be needed if onchoscomas are present or if there are serious ocular complications. Other treatments, such as steroids to reduce skin inflammation and antipruritics, may also be effective in controlling symptoms.
List of medications used to treat this disease
- Ivermectin.
- Dextromethorphan to reduce skin itching.
- Glucocorticosteroids to control inflammatory reactions.
Disease monitoring
Monitoring the patient's condition and the effectiveness of treatment are of primary importance. Regular checks for microfilariae in the blood are usually recommended, as well as assessing the extent of skin and visual damage. The prognosis for adequate treatment largely depends on timely diagnosis and initiation of therapy. Possible complications include:
- Blindness and other ophthalmological problems.
- Severe dermatological changes such as cyclic skin infections.
Age-related features of the disease
Onchocerciasis can occur at any age, but children and the elderly have specific clinical features. In children, the manifestations may be less pronounced, but the risk of transmission remains high. In elderly patients, the incidence is more severe, which is associated with systemic complications and a lack of immune response.
Questions and Answers
- What causes onchocerciasis? Onchocerciasis is caused by parasitic worms of the genus Onchocerca, transmitted through the bite of the Simulium fly.
- What are the main symptoms of onchocerciasis? The main symptoms include severe itching, skin rashes, and changes in vision, including blindness.
- How is onchocerciasis diagnosed? Diagnosis includes clinical examination, microscopy of skin biopsies and serologic tests.
- Is this how onchocerciasis is treated? The main treatment method is the use of ivermectin; in some cases, surgery is performed.
- What complications may arise during the treatment of onchocerciasis? Possible complications include blindness, skin infections and chronic inflammatory processes.
