Onchocerciasis

Definition

Onchocerciasis, also known as river blindness, is a parasitic disease caused by the filarial worm Onchocerca volvulus. It is a major public health concern in parts of Africa and Latin America, leading to severe skin disease and vision impairment, including permanent blindness.

5 Must Know Facts For Your Next Test

1. Onchocerciasis is endemic in parts of Africa, particularly sub-Saharan Africa, and in limited areas of Latin America.
2. The Onchocerca volvulus parasite is transmitted to humans through the bites of infected blackflies that breed in fast-flowing rivers and streams.
3. Chronic exposure to the parasite can lead to the development of severe skin disease, known as onchodermatitis, and progressive vision loss, including irreversible blindness.
4. Ivermectin is the primary drug used to treat onchocerciasis, as it can effectively kill the larval stages of the Onchocerca volvulus parasite.
5. Mass drug administration programs, involving the regular distribution of ivermectin, have been instrumental in reducing the burden of onchocerciasis in many endemic regions.

Review Questions

• Explain the role of blackflies in the transmission of Onchocerca volvulus, the causative agent of onchocerciasis.
  • Blackflies, particularly those of the genus Simulium, are the primary vectors responsible for transmitting the Onchocerca volvulus parasite to humans. These flies breed in fast-flowing rivers and streams, and when they feed on human blood, they can introduce the infective larval stage of the parasite into the host. The parasite then develops and matures within the human body, leading to the manifestation of the disease known as onchocerciasis or river blindness.
• Describe the pathological effects of chronic onchocerciasis infection on the skin and vision of affected individuals.
  • Chronic exposure to the Onchocerca volvulus parasite can lead to the development of severe skin disease, known as onchodermatitis. This condition is characterized by intense itching, skin discoloration, and the formation of nodules under the skin. Additionally, the presence of the parasite in the eye can cause progressive vision loss, ultimately resulting in irreversible blindness. The death of the adult worms and the release of their antigens can trigger an inflammatory response that damages the cornea and other ocular structures, leading to the development of river blindness.
• Evaluate the role of mass drug administration programs in the global control and elimination of onchocerciasis.
  • Mass drug administration programs, involving the regular distribution of the antiparasitic drug ivermectin, have been instrumental in reducing the burden of onchocerciasis in many endemic regions. Ivermectin is highly effective in killing the larval stages of the Onchocerca volvulus parasite, breaking the cycle of transmission and preventing the development of the disease. These large-scale, coordinated efforts have led to significant reductions in the prevalence of onchocerciasis, and in some areas, have even resulted in the elimination of the disease as a public health problem. The success of these programs highlights the importance of a comprehensive, multifaceted approach to tackling neglected tropical diseases like onchocerciasis on a global scale.

Related terms

Filarial Worms: Filarial worms are a group of parasitic nematodes that can infect humans and animals, causing diseases such as onchocerciasis, lymphatic filariasis, and loiasis.

Blackflies: Blackflies, particularly of the genus Simulium, are the vectors that transmit the Onchocerca volvulus parasite to humans through their bites.

Ivermectin:

Ivermectin is a highly effective antiparasitic drug used to treat onchocerciasis and other helminthic infections by disrupting the nervous system of the parasites.