Onchocerciasis

Why in News ?

The World Health Organization (WHO) has officially declared Niger free of onchocerciasis (river blindness), making it the first country in the WHO African Region to eliminate the disease.
This achievement marks a historic milestone in the fight against neglected tropical diseases (NTDs).

Background: Onchocerciasis, Africa’s Long Battle Against River Blindness

Onchocerciasis has been a major public health challenge across Africa for decades, especially in remote, underserved communities. The disease is transmitted by blackflies breeding near rivers—often where agriculture, fishing, and daily life are concentrated—making eradication difficult.

Global History of Control Efforts

• The disease was first identified in the early 20th century.
• Large-scale control began with:
  • Onchocerciasis Control Programme (OCP) in West Africa (1974–2002),
  • African Programme for Onchocerciasis Control (APOC) (1995–2015),
  • Followed by WHO’s Expanded Special Project for Elimination of NTDs (ESPEN).
• The turning point was the donation of ivermectin (Mectizan) by Merck & Co. (1987) for as long as needed.

Niger’s Elimination Journey

Niger’s elimination is the result of:

• Over 30 years of mass ivermectin distribution
• Continuous entomological surveillance
• Community-led health programmes
• Strong political commitment and WHO technical support

Niger’s success proves that even vector-borne diseases entrenched in rural ecosystems can be eliminated with persistence.

What is Onchocerciasis (River Blindness) ?

Onchocerciasis is a parasitic infection caused by the filarial worm Onchocerca volvulus. It is transmitted to humans by the bite of infected Simulium blackflies, which breed in fast-flowing rivers and streams. Because transmission depends on the blackfly, the disease cannot spread directly from person to person.

Transmission Cycle

1. An infected person has microfilariae (larvae) in their skin.
2. A blackfly bites them and ingests these larvae.
3. Inside the fly, the larvae mature into infectious forms.
4. When the fly bites another human, the parasite enters the body.
5. The worms settle in nodules, reproduce, and release more larvae, causing chronic disease.

This cycle keeps entire communities trapped in infection for generations.

Where is Onchocerciasis Found ?

• Predominantly in sub-Saharan Africa (99% of global cases)
• Limited presence in Brazil and Venezuela
• A major NTD affecting impoverished rural populations

WHO identifies it as one of the most neglected diseases, primarily due to geographic isolation and weak health infrastructure.

Symptoms and Health Impact

• Persistent itchy skin rashes
• Skin thickening and disfigurement ("leopard skin")
• Vision impairment
• Progressive eye damage leading to permanent blindness

It is the second leading infectious cause of blindness worldwide, after trachoma.

Treatment and Elimination Strategy

1. Ivermectin (MDA Programmes)

The cornerstone of treatment is annual or biannual ivermectin, which:

• Kills microfilariae
• Prevents eye damage
• Interrupts transmission

2. Vector Control

Involves spraying to reduce blackfly populations, especially in high-transmission zones.

3. Community-based Distribution

Local volunteers and health workers play a key role in mass drug administration (MDA).

4. Rigorous Surveillance

Countries must demonstrate:

• No new infections
• No vectors transmitting parasites
• Sustained interruption for several years

before WHO certifies elimination.

Why Niger’s Achievement is Significant

• First African nation to eliminate a disease that affects millions across the continent.
• Demonstrates the success of:
  • Long-term public health planning
  • Cross-border coordination
  • Community health leadership
• Sets a model for other African countries still battling the disease.
• Strengthens global confidence that NTD elimination is achievable this century.

WHO considers this a “breakthrough moment for Africa’s NTD roadmap.”