Dermatologic Manifestations of Onchocerciasis (River Blindness)
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Onchocerciasis is a common, chronic, multisystemic disease caused by the nematode Onchocerca volvulus. The disease characteristically includes dermatologic (see the image below), lymphatic, ophthalmologic, and systemic manifestations. Human transmission of the disease is caused by a bite from the intermediate host, the black fly (genus Simulium). [1] Black flies breed along waterways, which can vary from small streams to broad rivers. Affected individuals usually live or work within a few kilometers of these sites. Onchocerciasis has long been associated with a high incidence of detrimental effects on socioeconomic development and public health in endemic areas.
Related Medscape articles include the following:
Ophthalmologiic Manifestations of Onchocerciasis
Dermatologic Manifestations of Filariasis
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 the vector to be Simulium in Sierra Leone. The main vector in most of Africa is Simulium damnosum; in Ethiopia, Uganda, Tanzania, and the Democratic Republic of the Congo, Simulium neavei is common. In the Americas, the principal vectors are Simulium metallicum, Simulium ochraceum, and Simulium exiguum. Some vectors bite humans rather exclusively, whereas others are zoophilic to varying degrees. Animal reservoirs of O volvulus have not been found.
When a black fly takes a blood meal from an infected human, they also ingest onchocercal microfilariae in the skin. Surviving microfilariae in the black fly burst through the peritrophic membrane formed by the blood meal, invade the midgut, and advance to the thoracic muscles. The differentiation of these microfilariae into L1 larva begins in muscle within 28 hours after the blood meal. The first molt produces L2 larva within 96 hours, followed by the second molt, which produces L3 larva by day 7. The infective L3 larva migrates to the insect’s head and mouth for future deposition into human skin during the next blood meal.
After L3 larvae are transmitted to human skin, those that survive molt within 1 week to form L4 larva. Their development into male and female forms is completed by 1-3 months. The adult worms reside in the deep dermis and fascial planes. Thick, fibrous, subcutaneous nodules called onchocercomas are formed as the result of the development of scar tissue around the adult worms. These onchocercomas average 3 cm in diameter, and they typically contain 2-3 female adults and 1-2 male adults. The nodules typically are surrounded by eosinophils and lymphocytes that are ready to attack the newly produced microfilariae.
Adult worms isolated in nodules are not directly harmful to the patient. Their progeny, which are released from the nodules, are responsible for most of the damage related to onchocerciasis. Nonetheless, to control the disease, the identification and removal of these onchocercomas is critical. Ivermectin is the most effective agent against microfilariae (see Medical Care). Currently, available agents that are effective against adult worms are toxic. For this reason, surgical removal of the adult worms is important.
Within 10-12 months after the initial infection, adult female worms start producing microfilariae, which have an average lifespan of 6 months to 2 years. The reproductive life of the adult averages 9-11 years. During this time, female worms may release 1300-1900 microfilariae per day. The maximal production of offspring occurs during the first 5 years of the worm’s reproductive life, after which this activity declines in a linear fashion.
The microfilariae released from the nodules easily traverse the skin and connective tissue. The subepidermal lymphatics and the anterior chamber of the eye are the most common migration sites. The microfilariae can also be found in the blood, cerebrospinal fluid, urine, and internal organs. More than 100 million microfilariae may be present in severely affected individuals.
A symbiotic relationship has been demonstrated between Wolbachia bacteria and filarial nematodes, including O volvulus. [2] Wolbachia species are essential for nematode fertility. Embryogenesis in the female worm is disrupted when Wolbachia numbers are depleted. In addition, murine experiments suggest that corneal inflammation secondary to onchocerciasis may be caused by endotoxins produced by Wolbachia. Results from several small trials suggest that clearance of Wolbachia with antibiotic therapy affects transmission and can reduce and prevent onchocerciasis-related blindness.
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.
United States
Onchocerciasis is rare in the United States. All reported cases result from the immigration of individuals from endemic areas.
International
Onchocerciasis is a major public health problem in many parts of the world. The disease is endemic in 37 countries in Africa, Latin America, and Yemen. In 1995, an estimated 123 million people were at risk of contracting the disease according to the World Health Organization Expert Committee on Onchocerciasis. Another 17-18 million people were estimated to be infected.
Approximately 95% of all infected people live in Africa. The disease is most severe along the major rivers in 30 countries across the northern and central areas of the continent. Nigeria, Ethiopia, Cameroon, Uganda, and the Democratic Republic of the Congo have the largest number of infected people.
In Latin America, onchocerciasis can be found in Brazil, Venezuela, Colombia, Ecuador, and Guatemala, as well as in the southern mountainous states of Chiapas and Oaxaca in Mexico. [3]
To the author’s knowledge, no current well-described studies have been performed to determine the frequency of onchocerciasis in specific races.
The disease generally affects more men than women, although sex-related differences may not be apparent until the patient reaches a certain age.
Sex-related differences are more pronounced in high-transmission areas, particularly the savanna.
The overall trend is partially attributed to increased exposures in men, which are related to the occupational risk in farmers, fishermen, and other workers.
The prevalence of onchocerciasis is lowest in individuals aged 0-10 years. Afterward, the prevalence sharply increases, with a peak in individuals aged 20-30 years.
The prognosis for onchocerciasis is good in patients who receive proper therapy before irreversible eye lesions develop. Ivermectin is effective in reducing the skin manifestations of the disease; it thereby reduces morbidity and improves the patient’s quality of life.
In 1995, an estimated 270,000 people were blinded and another 500,000 had severe visual impairment as a result of the disease. A multicountry study showed that more than 30% of the population in endemic areas have onchocercal dermatitis. [4] In a survey of skin disease in 7 endemic sites in 5 African countries, 40-50% of adults reported troublesome itching. Blindness is not associated with excess mortality. However, increasing microfilarial load is associated with mortality in both males and females.
Hendy A, Krüger A, Pfarr K, De Witte J, Kibweja A, Mwingira U, et al. The blackfly vectors and transmission of Onchocerca volvulus in Mahenge, south eastern Tanzania. Acta Trop. 2018 May. 181:50-59. [Medline].
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].
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].
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].
Walker M, Pion SDS, Fang H, Gardon J, Kamgno J, Basáñez MG, et al. Macrofilaricidal Efficacy of Repeated Doses of Ivermectin for the Treatment of River Blindness. Clin Infect Dis. 2017 Nov 29. 65 (12):2026-2034. [Medline]. [Full Text].
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].
Opoku NO, Bakajika DK, Kanza EM, Howard H, Mambandu GL, Nyathirombo A, et al. Single dose moxidectin versus ivermectin for Onchocerca volvulus infection in Ghana, Liberia, and the Democratic Republic of the Congo: a randomised, controlled, double-blind phase 3 trial. Lancet. 2018 Jan 17. [Medline]. [Full Text].
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].
Abegunde AT, Ahuja RM, Okafor NJ. Doxycycline plus ivermectin versus ivermectin alone for treatment of patients with onchocerciasis. Cochrane Database Syst Rev. 2016 Jan 15. CD011146. [Medline]. [Full Text].
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].
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].
Puente S, Ramirez-Olivencia G, Lago M, Subirats M, Perez-Blazquez E, Bru F, et al. Dermatological manifestations in onchocerciasis: A retrospective study of 400 imported cases. Enferm Infecc Microbiol Clin. 2017 Dec 20. [Medline].
Jason F Okulicz, MD, FACP, FIDSA Director, HIV Medical Evaluation Unit, Infectious Disease Service, San Antonio Military Medical Center; Associate Professor of Medicine, F Edward Hebert School of Medicine, Uniformed Services University of the Health Sciences; Clinical Associate Professor of Medicine, University of Texas Health Science Center at San Antonio; Adjunct Clinical Instructor, Feik School of Pharmacy, University of the Incarnate Word
Jason F Okulicz, MD, FACP, FIDSA is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians-American Society of Internal Medicine, Infectious Diseases Society of America
Disclosure: Serve(d) as a speaker or a member of a speakers bureau for: Gilead Sciences.
Dirk M Elston, MD Professor and Chairman, Department of Dermatology and Dermatologic Surgery, Medical University of South Carolina College of Medicine
Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology
Disclosure: Nothing to disclose.
Robert A Schwartz, MD, MPH Professor and Head of Dermatology, Professor of Pathology, Pediatrics, Medicine, and Preventive Medicine and Community Health, Rutgers New Jersey Medical School; Visiting Professor, Rutgers University School of Public Affairs and Administration
Robert A Schwartz, MD, MPH is a member of the following medical societies: Alpha Omega Alpha, New York Academy of Medicine, American Academy of Dermatology, American College of Physicians, Sigma Xi
Disclosure: Nothing to disclose.
David F Butler, MD Former Section Chief of Dermatology, Central Texas Veterans Healthcare System; Professor of Dermatology, Texas A&M University College of Medicine; Founding Chair, Department of Dermatology, Scott and White Clinic
David F Butler, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Society for MOHS Surgery, Association of Military Dermatologists, Phi Beta Kappa
Disclosure: Nothing to disclose.
William D James, MD Paul R Gross Professor of Dermatology, Vice-Chairman, Residency Program Director, Department of Dermatology, University of Pennsylvania School of Medicine
William D James, MD is a member of the following medical societies: American Academy of Dermatology, Society for Investigative Dermatology
Disclosure: Received income in an amount equal to or greater than $250 from: Elsevier; WebMD.
Donald Belsito, MD Professor of Clinical Dermatology, Department of Dermatology, Columbia University Medical Center
Donald Belsito, MD is a member of the following medical societies: New York County Medical Society, Noah Worcester Dermatological Society, Phi Beta Kappa, American Contact Dermatitis Society, Dermatology Foundation, Dermatologic Society of Greater New York, Alpha Omega Alpha, American Academy of Dermatology
Disclosure: Nothing to disclose.
Dermatologic Manifestations of Onchocerciasis (River Blindness)
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