Onchocerciasis can have a variety of clinical presentations, which normally appear 9-24 months after the bites of the infected flies. Inflammatory responses to dead or dying microfilaria are responsible for the majority of the clinical manifestations, which can range from the dermatological to the ocular. Approximately 10% of those infected with the disease are completely asymptomatic.
Information on this page was compiled from sources (14) and (28)
Early Symptoms
The first signs that a person has been infected with the O. volvulus parasite include fever, neuralgic pain in joints, and temporary hives on the trunk and face.
Dermatological Symptoms
The two main symptoms of Onchocerciasis that involve the skin are Onchocercal Dermatitis and Onchocercomas.
*Onchoceral Dermatitis is the most common symptom of the disease. The condition can appear anywhere on the body and includes alterations in skin pigment, scratching and itching. The pattern of itching can vary from intermittent to constant depending on the person. A rash consisting of patches of papules can appear on the body at any time and often leads to incessant scratching. In West Africa, this condition is known as craw-craw.
*Oncocercomas are subcutaneous, fibrous nodules where adult worms dwell and breed. These nodules are most easily felt when they form over a bony part of the body. Deep nodules around the groin region can be harder to detect, but finding every nodule is important for appropriate treatment of the disease. Having more nodules does not necessarily indicate a more severe microfilarial load.
-The location of the nodules on the body depends on the place that the fly bites, which varies by region. In the Americas, the nodules are found mostly on the upper body in the head and neck region, in contrast to Africa where the nodules are mostly on the lower body, especially in the groin region.
Murdoch et al developed a standardized classification system for the specific types of symptoms in order to facilitate the collection of data around the world:
*Acute popular onchodermatitis (APOD): A solid, scattered, pruritic papular rash. The diameter of the papules must be at least 1mm. May have vesicles or pustules at the apex and destruction of the skin crease due to edema.
*Chronic Papular Onchodermatitis (CPOD): A scattered, pruritic, hyperpigmented and flat-topped rash with papules that are at least 3mm.
*Lichenified Onchodermatitis (LOD): Raised, pruritic, and hyperpigmented papulonodular plaques associated with lymphadenopathy. The lesions may flow together or have patches of torn-off skin. This condition can occur with APOD or CPOD.
*Atrophy (ATR): Dry and wrinkled skin. Fine wrinkles are revealed by pressing the skin with a finger. This condition is very abnormal in patients under 50 years of age.
*Depigmentation: Some areas of skin have incomplete loss of pigmentation, while others surrounding the hair follicles have normal pigment. If a person has complete loss of pigment in spots or islands, this condition is known as “leopard skin.”
------“Leopard Skin” is most prominent in the older population. It is most often found on the lower extremities, especially below the knee.
*Palpable Oncocercal Nodule: Oncocercomas that are present at bony prominences.
(64)*Lymphadenopathy: Swollen lymph nodes that are 1cm or larger in diameter and may be tender.
*Hanging Groin (HM): Folds of inelastic, atrophic skin, and occasionally enlarged lymph nodes in inguinal areas of both males and females. This degenerative condition can occur on one or both sides and is more common in males than in females. This condition can become extremely severe in elderly patients. The groin and femoral lymph nodes progressively become enlarges and fibrotic, which can lead to obstruction of the lymph nodes.
Ocular Symptoms
Although onchocerciasis is commonly know as River Blindness, the ocular manifestations of the disease actually only occur in about 5% of those affected. These symptoms are severe reactions that occur only after years of having the disease.
-Initially, dead microfilariae in the eye cause inflammation and keratitis.
-If the infection persists over a number of years, sclerosing keratitis, iridocyclitis, and uveitis occur, resulting in permanent visual impairment, glaucoma, or blindness.
-In areas that are endemic with the disease, active optic inflammation is a major cause of blindness.
