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PubMed This is a summary of 17 peer-reviewed journal articles Updated
Infectious Disease · River Blindness

How to Protect Against Blackflies & River Blindness

At a Glance

To protect against river blindness, prevent daytime bites from blackflies by wearing light-colored, long-sleeved clothing treated with permethrin. Apply EPA-registered insect repellents like DEET, Picaridin, or IR3535 to exposed skin. There is no vaccine, so bite prevention is essential.

In this answer

2 sections

01

Understanding Blackfly Habits

02

Your Two-Part Defense Strategy

Yes, standard insect repellents that contain active ingredients like DEET, Picaridin, or IR3535 are effective against the blackflies that transmit river blindness (onchocerciasis) [1][2]. Because blackflies bite during the day, combining these sprays with protective clothing—such as long pants and sleeves, ideally treated with permethrin—is the most effective way to prevent bites [3][4][5].

While blackflies are found all over the world, the specific ones that carry the river blindness parasite are found almost exclusively in sub-Saharan Africa, with a few small, isolated areas in Latin America and Yemen [6][7][8]. If you are bitten by a blackfly in North America or Europe, you are not at risk for river blindness [9][10].

Understanding Blackfly Habits

To protect yourself effectively, it helps to understand how and when blackflies (the Simulium species) operate:

  • Daytime biters: Unlike some mosquitoes that bite at dusk or overnight, blackflies are active and bite during daylight hours [5].
  • Breeding grounds: They breed and swarm near fast-flowing rivers and streams, which is why the disease is called “river blindness” [11][9].
  • No vaccines or preventive pills: Currently, there are no vaccines or daily medications that anyone can take to prevent the initial infection [3][12]. While there are highly effective medical treatments if you are already infected, preventing the bite is the primary way to stop the parasite from entering your body in the first place.

Why Prevention Matters After Diagnosis

If you have already been diagnosed with river blindness, preventing new bites remains critical. Repeated exposure to infected blackflies in endemic areas is a primary risk factor that can increase the parasite load in your body over time [13]. Furthermore, the parasite is spread when an uninfected fly bites an infected person and then bites someone else [9][11]. Protecting yourself from bites helps break the cycle of transmission to your family and community.

Your Two-Part Defense Strategy

Protecting yourself requires a combination of what you wear and what you apply to your skin.

1. Clothing as a Physical Barrier

Clothing is your first and most reliable layer of defense [5][14].

  • Cover up: Wear long-sleeved shirts, long pants, and closed-toe shoes to minimize exposed skin [5]. Light-colored clothing is recommended, as blackflies are often attracted to dark colors.
  • Tuck it in: Blackflies frequently crawl under loose garments to find exposed skin. Tucking your shirt into your pants, and your pants into your socks, helps eliminate these entry points.
  • Treat your clothes: Clothing and gear treated with permethrin (an insecticide that repels and kills insects on contact) adds a highly effective layer of protection [15][16]. Permethrin is applied to fabrics, not directly to the skin, and can last through multiple washes [17].

2. Bug Sprays for Exposed Skin

For any skin that remains uncovered, use an EPA-registered insect repellent [3][4].

  • Effective ingredients: Look for sprays containing DEET, Picaridin, or IR3535 [1][2]. These are considered the standard for preventing insect bites and are effective against blackflies [1].
  • Proper application: If you are using sunscreen, apply it first, let it dry, and then apply the insect repellent. Reapply the spray as directed by the product label, especially if you are sweating.

Common questions in this guide

Do normal bug sprays work against the blackflies that cause river blindness?
Yes, standard insect repellents containing DEET, Picaridin, or IR3535 are highly effective against the blackflies that transmit river blindness. Apply these to any exposed skin after your sunscreen has dried.
What time of day do blackflies bite?
Unlike many mosquitoes that bite at dusk or overnight, the blackflies that carry river blindness are active and bite primarily during daylight hours.
Is there a vaccine or pill to prevent river blindness?
Currently, there are no vaccines or daily preventative pills available to stop the initial river blindness infection. Preventing blackfly bites is the only way to avoid contracting the disease.
Can I get river blindness from blackflies in North America?
No. While blackflies are common in North America and Europe, the specific flies that carry the river blindness parasite are found almost exclusively in sub-Saharan Africa, with a few isolated areas in Latin America and Yemen.
Why do I need to avoid blackfly bites if I already have river blindness?
Repeated blackfly bites can increase the amount of parasites in your body over time, which may worsen your condition. Preventing bites also stops uninfected flies from picking up the parasite from your blood and spreading it to your family and community.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Are the specific blackfly species in my local area known to carry the river blindness parasite?
  2. 2.If I have already been diagnosed with river blindness, how does my ongoing exposure to blackfly bites impact the effectiveness of my current treatment?
  3. 3.Should my family members also be tested if we all live near a high-risk river area where blackflies are common?
  4. 4.Do any of my current medications or skin conditions interact poorly with DEET or permethrin?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

Related questions

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References

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This page provides educational information on preventing river blindness and blackfly bites. It does not replace professional medical advice, and you should consult a travel medicine specialist before visiting endemic areas.

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