Dermatologic Manifestations of Onchocerciasis (River Blindness) Clinical Presentation
- Author: Jason F Okulicz, MD, FACP, FIDSA; Chief Editor: William D James, MD more...
The most important task is determining if patients in endemic areas have been exposed to O volvulus via the black fly vector. Obtain a detailed travel history if onchocerciasis is suspected. Travelers to endemic areas may have a particularly severe form of dermatitis.
Other manifestations of onchocerciasis include weight loss, musculoskeletal pain, inguinal hernias, and systemic embolization of microfilariae.
Many patients in endemic regions have associated the disease with secondary amenorrhea, lactation difficulties, spontaneous abortion, infertility, and sterility. However, these associations have never been proven.
Patients are asymptomatic in about 10% of cases.
Localized inflammatory responses to dead or dying microfilariae are almost entirely responsible for the clinical manifestations of the disease. In a severely infected person, 100,000 or more microfilariae die each day. The earliest symptoms are fever, arthralgia, and transient urticaria involving the trunk and face. Onchocercomas, the most characteristic skin lesions, are often present.
The following is a summary of the clinical classification system for onchocercal dermatitis, which Murdoch et al developed to standardize and facilitate the collection of data worldwide :
Acute papular onchodermatitis (APOD) is characterized by a solid, scattered, pruritic papular rash. The diameter of the papules is at least 1 mm. Vesicles or pustules at the apex may or may not be present. The obliteration of the skin creases due to edema also may or may not be present.
Chronic papular onchodermatitis (CPOD) involves a scattered, pruritic, hyperpigmented, and flat-topped papulomacular rash. The diameter of the papules is at least 3 mm, with or without excoriations.
Lichenified onchodermatitis (LOD) is characterized by raised, discrete, pruritic, and hyperpigmented papulonodular plaques associated with lymphadenopathy. The lesions may be confluent, with or without the presence of excoriations. APOD or CPOD may also be present.
Atrophy (ATR) involves wrinkled and dry skin. Firmly pressing the edge of a finger along the skin reveals additional fine wrinkles. In patients younger than 50 years, ATR is scored as a significant abnormality.
Depigmentation is characterized by areas of incomplete pigment loss, with associated islands or spots of normal pigment surrounding hair follicles. Leopard skin is similar, except that it is characterized by a complete loss of pigment, with islands or spots of normally pigmented skin around the follicles.
Lymphadenopathy is characterized by lymph nodes 1 cm or larger in diameter. They may or may not be tender.
Hanging groin (HG) involves the folds of inelastic, atrophic skin in the inguinal areas. The condition may be unilateral or bilateral, and it may involve enlarged lymph nodes. See the images below.Hanging groin sign. Courtesy of Brooke Army Medical Center teaching file. All images are in the public domain.
Lymphedema (LYM) is characterized by edema of a limb or external genitalia.
Onchocercomas are fibrous, subcutaneous nodules containing adult worms. These nodules are generally located over bony prominences, and they are easily palpable. Deep nodules, commonly located around the pelvis, can be more difficult to detect. The number of palpable nodules is not correlated with the microfilarial load or the severity of disease. Identifying every nodule is important for proper management. In Africa, the nodules are often observed along the iliac crests, ribs, greater trochanters, and ischial tuberosities. Juxta-articular areas, such as the knees (as shown below), elbows, patella, and scalp, may also have nodules.
In the American forms, nodules are fewer and have a greater tendency to be located on the scalp. In patients with scalp nodules, the risk of ocular complications is generally higher than that of patients without scalp nodules. Onchocercomas are less common in the Yemen form of the disease than in other forms.
Onchocercal dermatitis, as shown below, is the most common symptom of the disease. Its initial manifestations, which can occur anywhere on the body, include itching, scratching, and alterations in skin pigmentation. Pruritus may be intermittent and mild, continuous and severe, or absent. A maculopapular rash may appear anywhere on the body at any time. The papules may be small and densely packed or large and separated. The maculopapular rash is often associated with severe pruritus. Excess scratching may lead to bleeding, ulceration, and secondary infection (a condition West Africans call craw-craw).
Sowda, a severe form of dermatitis first described in Yemen, is associated with an active delayed hypersensitivity response. Many patients are travelers or temporary workers in nonendemic areas. These patients have dark, thickened, intensely pruritic skin with papules. The regional lymph nodes are soft, nontender, and enlarged. Sowda is usually localized to a single lower extremity. A less common, more generalized form can involve both lower extremities or other parts of the body. Patients have either focal swelling or a more diffuse LYM. Skin-snips do not usually contain microfilariae. Sowda may also be found in patients in West Africa, Ethiopia, Sudan, Cameroon, Venezuela, and Ecuador.
Leopard skin is a characteristic finding in older patients. Leopard skin involves depigmentation of the pretibial areas of the lower extremities. This pattern is initially seen as discrete depigmented macules, with sparing of the hair follicles. Later, the macules may become confluent, involving a large area of the anterior portion below the knee, as shown below. This pattern can sometimes be seen in the groin or lower abdomen as well.
HG or adenolymphocele is a severe degenerative condition in older individuals. The inguinal and femoral lymph nodes become progressively enlarged and fibrotic, leading to lymphatic obstruction. Concomitantly, progressive destruction of elastic fibers leaves the skin thinned and wrinkled. The atrophied skin tends to hang in apronlike folds under the weight of the accumulating lymphedematous tissue. This condition is more common in men than in women.
Ocular manifestations of onchocerciasis are late, serious reactions that occur in about 5% of affected persons. Infection of the cornea produces punctate keratitis in the areas around dead microfilariae. This condition eventually clears when the inflammation settles. Severe and prolonged infection over a number of years is likely to produce sclerosing keratitis, iridocyclitis, and uveitis. Permanent visual impairment, secondary glaucoma, or blindness is often the result. Posterior segment changes may coexist with anterior segment lesions. The changes are caused by inflammation around microfilariae that invade the retina via the posterior ciliary vessels. Choroidoretinal lesions are common around the optic disk or on the outer portion of the macula. Active optic neuritis is a major cause of blindness in many areas with endemic disease.
In 1875, John O'Neill first observed O volvulus microfilariae in a case of craw-craw, as onchocerciasis is known in West Africa. Almost 50 years later, Blacklock discovered that the vector in Sierra Leone was a Simulium organism. The main vector in most of Africa is S damnosum; in Ethiopia, Uganda, Tanzania, and the Democratic Republic of the Congo, S neavei is common.
The principal vectors in the Americas are S metallicum, S ochraceum, and S exiguum. Some vectors bite humans rather exclusively, whereas others are zoophilic to varying degrees. Animal reservoirs of O volvulus have not been found.
Saint Andre A, Blackwell NM, Hall LR, et al. The role of endosymbiotic Wolbachia bacteria in the pathogenesis of river blindness. Science. 2002 Mar 8. 295(5561):1892-5. [Medline].
Martin-Tellaeche A, Ramirez-Hernandez J, Santos-Preciado JI, Mendez-Galvan J. Onchocerciasis: changes in transmission in Mexico. Ann Trop Med Parasitol. 1998 Apr. 92 Suppl 1:S117-9. [Medline].
Murdoch ME, Hay RJ, Mackenzie CD, Williams JF, Ghalib HW, Cousens S, et al. A clinical classification and grading system of the cutaneous changes in onchocerciasis. Br J Dermatol. 1993 Sep. 129(3):260-9. [Medline].
Stingl P. Onchocerciasis: clinical presentation and host parasite interactions in patients of southern Sudan. Int J Dermatol. 1997 Jan. 36(1):23-8. [Medline].
Stingl P, Ross M, Gibson DW, Ribas J, Connor DH. A diagnostic "patch test" for onchocerciasis using topical diethylcarbamazine. Trans R Soc Trop Med Hyg. 1984. 78(2):254-8. [Medline].
Toe L, Adjami AG, Boatin BA, Back C, Alley ES, Dembele N, et al. Topical application of diethylcarbamazine to detect onchocerciasis recrudescence in west Africa. Trans R Soc Trop Med Hyg. 2000 Sep-Oct. 94(5):519-25. [Medline].
Toe L, Boatin BA, Adjami A, Back C, Merriweather A, Unnasch TR. Detection of Onchocerca volvulus infection by O-150 polymerase chain reaction analysis of skin scratches. J Infect Dis. 1998 Jul. 178(1):282-5. [Medline].
Rodriguez-Perez MA, Dominguez-Vazquez A, Mendez-Galvan J, et al. Antibody detection tests for Onchocerca volvulus: comparison of the sensitivity of a cocktail of recombinant antigens used in the indirect enzyme-linked immunosorbent assay with a rapid-format antibody card test. Trans R Soc Trop Med Hyg. 2003 Sep-Oct. 97(5):539-41. [Medline].
Weil GJ, Steel C, Liftis F, et al. A rapid-format antibody card test for diagnosis of onchocerciasis. J Infect Dis. 2000 Dec. 182(6):1796-9. [Medline].
Ayong LS, Tume CB, Wembe FE, et al. Development and evaluation of an antigen detection dipstick assay for the diagnosis of human onchocerciasis. Trop Med Int Health. 2005 Mar. 10(3):228-33. [Medline].
Baraka OZ, Mahmoud BM, Ali MM, et al. Ivermectin treatment in severe asymmetric reactive onchodermatitis (sowda) in Sudan. Trans R Soc Trop Med Hyg. 1995 May-Jun. 89(3):312-5. [Medline].
Burnham G. Ivermectin treatment of onchocercal skin lesions: observations from a placebo-controlled, double-blind trial in Malawi. Am J Trop Med Hyg. 1995 Mar. 52(3):270-6. [Medline].
Ogbuagu KF, Eneanya CI. A multi-centre study of the effect of Mectizan treatment on onchocercal skin disease: clinical findings. Ann Trop Med Parasitol. 1998 Apr. 92 Suppl 1:S139-45. [Medline].
Pacque M, Elmets C, Dukuly ZD, et al. Improvement in severe onchocercal skin disease after a single dose of ivermectin. Am J Med. 1991 May. 90(5):590-4. [Medline].
Osei-Atweneboana MY, Awadzi K, Attah SK, Boakye DA, Gyapong JO, Prichard RK. Phenotypic evidence of emerging ivermectin resistance in Onchocerca volvulus. PLoS Negl Trop Dis. 2011. 5(3):e998. [Medline].
Debrah AY, Mand S, Marfo-Debrekyei Y, Larbi J, Adjei O, Hoerauf A. Assessment of microfilarial loads in the skin of onchocerciasis patients after treatment with different regimens of doxycycline plus ivermectin. Filaria J. 2006. 5:1. [Medline].
Hoerauf A, Specht S, Marfo-Debrekyei Y, et al. Efficacy of 5-week doxycycline treatment on adult Onchocerca volvulus. Parasitol Res. 2009 Jan. 104(2):437-47. [Medline].
Hoerauf A, Marfo-Debrekyei Y, Buttner M, et al. Effects of 6-week azithromycin treatment on the Wolbachia endobacteria of Onchocerca volvulus. Parasitol Res. 2008 Jul. 103(2):279-86. [Medline].
Specht S, Mand S, Marfo-Debrekyei Y, et al. Efficacy of 2- and 4-week rifampicin treatment on the Wolbachia of Onchocerca volvulus. Parasitol Res. 2008 Nov. 103(6):1303-9. [Medline].
Bah GS, Ward EL, Srivastava A, Trees AJ, Tanya VN, Makepeace BL. Efficacy of three-week oxytetracycline or rifampicin monotherapy compared with a combination regimen against the filarial nematode Onchocerca ochengi. Antimicrob Agents Chemother. 2013 Nov 18. [Medline].
Awadzi K, Opoku NO, Attah SK, et al. The safety and efficacy of amocarzine in African onchocerciasis and the influence of ivermectin on the clinical and parasitological response to treatment. Ann Trop Med Parasitol. 1997 Apr. 91(3):281-96. [Medline].
Hoerauf A, Volkmann L, Hamelmann C, et al. Endosymbiotic bacteria in worms as targets for a novel chemotherapy in filariasis. Lancet. 2000 Apr 8. 355(9211):1242-3. [Medline].
Coffeng LE, Fobi G, Ozoh G, Bissek AC, Nlatté BO, Enyong P, et al. Concurrence of dermatological and ophthalmological morbidity in onchocerciasis. Trans R Soc Trop Med Hyg. 2012 Apr. 106(4):243-51. [Medline].
Vernick W, Turner SE, Burov E, Telang GH. Onchocerciasis presenting with lower extremity, hypopigmented macules. Cutis. 2000 May. 65(5):293-7. [Medline].
Somorin AO. Onchocerciasis. Int J Dermatol. 1983 Apr. 22(3):182-8. [Medline].