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Onchocerciasis Clinical Presentation

  • Author: Mary D Nettleman, MD, MS; Chief Editor: Mark R Wallace, MD, FACP, FIDSA  more...
Updated: Nov 05, 2015


Symptoms of onchocerciasis reflect the developmental stage of the parasite and the degree of immune response by the host. Clinical manifestations are highly variable.

Symptoms of onchocerciasis do not appear until after the L3 larvae mature into adult worms. On average, symptoms appear between 9 months and 2 years after the initial infecting bite. The interval between acquisition of the parasite and onset of symptoms is sometimes referred to as the prepatent phase.

Once developed, adult worms cluster in subcutaneous nodules (onchocercomata).

Generalized pruritus may occur early in the infection and may be severe. A papular rash known as onchodermatitis may be present. Initially, the rash may be transient, but chronic infection over several years may lead to lichenification, loss of skin elasticity, atrophy, and/or depigmentation.

Itchy eyes, redness, or photophobia may be early symptoms of ocular onchocerciasis. Over years, the scarring progresses to cause visual loss and ultimately blindness. Acute optic neuritis is less common but may also cause blindness.

Weight loss and generalized myalgias may occur.



Skin examination in patients with onchocerciasis may reveal subcutaneous nodules, diffuse onchodermatitis, lymphedema, and/or atrophic changes.

Onchodermatitis consists of raised papules that are intensely pruritic. Vesicles and pustules may also be present. Scratching may cause secondary infection.

In its extreme form, skin atrophy may cause drooping of the inguinal skin, termed hanging groin.

In some cases, the skin is dry and resembles ichthyosis.

Sowda refers to severe pruritus and darkened skin, usually confined to one limb. It is most commonly described in Yemen but also occurs in Africa.

Leopard skin refers to bilateral, symmetric, patchy depigmentation of the shins.

Lymphadenopathy may occur.

Subcutaneous nodules are firm, nontender, and mobile and are several millimeters to centimeters in size. They develop most commonly over bony prominences on the trunk and hip (Africa) or head and shoulders (Americas).

In the eye, the inflammatory response to dying microfilariae and Wolbachia antigens causes punctuate keratitis (snowflake opacities). Advanced cases may result in corneal fibrosis or opacification. Slit-lamp examination may reveal microfilariae in the cornea and anterior chamber. Other ocular manifestations include iridocyclitis, glaucoma, chorioiditis, and optic atrophy.[22]



O volvulus is transmitted by the bite of infected Simulium flies. The fly bites during daylight hours. Simulium flies breed near fast-flowing rivers and streams.

Ocular symptoms are caused by the inflammatory response invoked by the release of Wolbachia antigens when microfilariae die.

Contributor Information and Disclosures

Mary D Nettleman, MD, MS MACP, Professor and Chair, Department of Medicine, Michigan State University College of Human Medicine

Mary D Nettleman, MD, MS is a member of the following medical societies: American College of Physicians, Association of Professors of Medicine, Central Society for Clinical and Translational Research, Infectious Diseases Society of America, Society of General Internal Medicine

Disclosure: Nothing to disclose.


Apoorv Kalra, MD Assistant Professor of Medicine, Michigan State University

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

John W King, MD Professor of Medicine, Chief, Section of Infectious Diseases, Director, Viral Therapeutics Clinics for Hepatitis, Louisiana State University Health Sciences Center; Consultant in Infectious Diseases, Overton Brooks Veterans Affairs Medical Center

John W King, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Federation for Medical Research, Association of Subspecialty Professors, American Society for Microbiology, Infectious Diseases Society of America, Sigma Xi

Disclosure: Nothing to disclose.

Chief Editor

Mark R Wallace, MD, FACP, FIDSA Clinical Professor of Medicine, Florida State University College of Medicine; Clinical Professor of Medicine, University of Central Florida College of Medicine

Mark R Wallace, MD, FACP, FIDSA is a member of the following medical societies: American College of Physicians, American Medical Association, American Society for Microbiology, Infectious Diseases Society of America, International AIDS Society, Florida Infectious Diseases Society

Disclosure: Nothing to disclose.

Additional Contributors

Daniel R Lucey, MD, MPH, MD, MPH 

Daniel R Lucey, MD, MPH, MD, MPH is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians

Disclosure: Nothing to disclose.

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Simulium fly (black fly).
Histopathology of an Onchocerca volvulus nodule. Image courtesy of the CDC and Dr. Mae Melvin.
Simplified life cycle of Onchocerciasis volvulus.
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