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'''For patient information, click [[Loa loa filariasis (patient information)|here]]'''
{{Loa loa filariasis}}
{{Loa loa filariasis}}
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{{CMG}} {{AE}} {{KD}}
==Overview==
''Loa loa filariasis'' (also ''loiasis,'' ''[[Calabar swellings]]'' and ''African eyeworm'') is a [[skin]] and [[eye]] disease caused by the [[nematode]] [[worm]], [[loa loa filaria]]. Humans contract this disease through the bite of a [[horsefly]]. The [[Deer fly]] and the [[Cordylobia anthropophaga|Mango fly]] are also vectors for Loa loa. The disease can cause red itchy swellings below the skin called "[[Calabar swellings]]". The disease is treated with the drug [[diethylcarbamazine]] (DEC).


Human loiasis geographical distribution is restricted to the [[rain forest]] and [[swamp]] forest areas of [[West Africa]], being especially common in [[Cameroon]] and on the [[Ogowe River]]. Humans are the only known [[natural reservoir]]. It is estimated that 12-13 million humans are infected with the Loa loa larvae.
{{SK}} African eye worm; loaiasis;  loiasis; loaina; filaria loa; filaria lacrimalis; filaria subconjunctivalis; fugitive swellings; microfilaria diurnal


==Life cycle==
==[[Loa loa filariasis overview|Overview]]==


[[Image:L loa LifeCycle.gif|framed|Loa loa life cycle. Source: CDC]]
==[[Loa loa filariasis historical perspective|Historical Perspective]]==


The [[vector (biology)|vector]] for Loa loa filariasis are flies from two [[hematophagy|hematophagous]] species of the genus ''[[Chrysops]]'', ''C. silacea'' and ''C. dimidiata''. During a [[blood]] meal, an infected fly (genus ''Chrysops'', day-biting flies) introduces third-stage filarial [[larva]]e onto the [[skin]] of the human [[Host (biology)|host]], where they penetrate into the bite wound. The larvae develop into adults that commonly reside in [[subcutaneous tissue]]. The female worms measure 40 to 70 mm in length and 0.5 mm in diameter, while the males measure 30 to 34 mm in length and 0.35 to 0.43 mm in diameter.  Adults produce microfilariae measuring 250 to 300 μm by 6 to 8 μm, which are sheathed and have diurnal periodicity.  Microfilariae have been recovered from [[cerebrospinal fluid|spinal fluid]]s, [[urine]], and [[sputum]].  During the day they are found in peripheral blood, but during the noncirculation phase, they are found in the [[lungs]]. The fly ingests microfilariae during a blood meal. After ingestion, the microfilariae lose their sheaths and migrate from the fly's midgut through the [[open circulatory system|hemocoel]] to the thoracic muscles of the [[arthropod]]. There the microfilariae develop into first-stage larvae and subsequently into third-stage infective larvae. The third-stage infective larvae migrate to the fly's [[proboscis]] and can infect another human when the fly takes a blood meal.
==[[Loa loa filariasis pathophysiology|Pathophysiology]]==


==Clinical features==
==[[Loa loa filariasis causes|Causes]]==


[[Lymphatic system|Lymphatic]] [[filariasis]] such as loiasis most often consists of [[asymptomatic]] microfilaremia.  Some patients develop lymphatic dysfunction causing [[lymphedema]]. Episodic [[angioedema]] (Calabar swellings) in the arms and legs, caused by immune reactions are common. When chronic, they can form cyst-like enlargements of the [[connective tissue]] around the sheaths of [[muscle]] [[tendon]]s, becoming very [[pain]]ful when moved. The swellings may last for 1-3 days, and may be accompanied by localized [[urticaria]] (skin eruptions) and [[itch|pruritus]] (itching). Subconjunctival migration of an adult worm to the eyes can also occur frequently, in this is the reason Loa loa is also called the "African eye worm." The passage over the eyeball can be sensed, but it usually takes less than 15 min. Gender incidence of eyeworms have approximately the same frequency, but it tends to increase with age. [[Eosinophilia]] is often prominent in filarial infections. Dead worms may cause chronic [[abscess]]es, which may lead to the formation of [[granulomatosis|granulomatous reaction]]s and [[fibrosis]].
==[[Loa loa filariasis differential diagnosis|Differentiating Loa Loa Filariasis from other Diseases]]==


==Laboratory diagnosis==
==[[Loa loa filariasis epidemiology and demographics|Epidemiology and Demographics]]==


Identification of microfilariae by [[microscope|microscopic]] examination is the most practical [[diagnosis|diagnostic]] procedure. Examination of blood samples will allow identification of microfilariae of Loa loa. It is important to time the blood collection with the known periodicity of the microfilariae. The blood sample can be a thick smear, stained with [[Giemsa]] or [[hematoxylin]] and [[eosin]] (see [[staining (biology)]]). For increased [[sensitivity]], concentration techniques can be used.  These include [[centrifugation]] of the blood sample lyzed in 2% [[formalin]] ([[Knott's technique]]), or [[filtration]] through a [[Nucleopore]] membrane.
==[[Loa loa filariasis risk factors|Risk Factors]]==


[[Antigen]] detection using an [[immunoassay]] for circulating filarial antigens constitutes a useful diagnostic approach, because microfilaremia can be low and variable. Identification of adult worms is possible from tissue samples collected during subcutaneous [[biopsy|biopsies]] or worm removal from the [[eye]]. [[Antibody]] detection is of limited value.  Substantial antigenic cross reactivity exists between filaria and other [[helminth]]s, and a positive serologic test does not distinguish between past and current infection.
==[[Loa loa filariasis natural history, complications and prognosis|Natural History, Complications and Prognosis]]==
==Diagnosis==
[[Loa loa filariasis history and symptoms| History and Symptoms]] | [[Loa loa filariasis physical examination | Physical Examination]] | [[Loa loa filariasis laboratory findings|Laboratory Findings]] | [[Loa loa filariasis other diagnostic studies|Other Diagnostic Studies]]


==Source==
==Treatment==
* [http://www.dpd.cdc.gov/dpdx/HTML/Filariasis.asp?body=Frames/A-F/Filariasis/body_Filariasis_l_loa.htm Loa Loa]. Center for Disease Control and Prevention (CDC). US Government public domain text and images.
[[Loa loa filariasis medical therapy|Medical Therapy]] | [[Loa loa filariasis surgery|Surgery]] | [[Loa loa filariasis primary prevention|Primary Prevention]] | [[Loa loa filariasis cost-effectiveness of therapy|Cost-Effectiveness of Therapy]] | [[Loa loa filariasis future or investigational therapies|Future or Investigational Therapies]]
:* '''Cutaneous filariasis -  Loa loa, onchocercia volvulus'''<ref name="pmid20739055">{{cite journal| author=Taylor MJ, Hoerauf A, Bockarie M| title=Lymphatic filariasis and onchocerciasis. | journal=Lancet | year= 2010 | volume= 376 | issue= 9747 | pages= 1175-85 | pmid=20739055 | doi=10.1016/S0140-6736(10)60586-7 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20739055  }} </ref><ref name="pmid22632644">{{cite journal| author=Knopp S, Steinmann P, Hatz C, Keiser J, Utzinger J| title=Nematode infections: filariases. | journal=Infect Dis Clin North Am | year= 2012 | volume= 26 | issue= 2 | pages= 359-81 | pmid=22632644 | doi=10.1016/j.idc.2012.02.005 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=22632644  }} </ref>
::* Preferred regimen (1): [[Doxycycline]] 150 μg/kg single dose
::* Preferred regimen (2): ([[Doxycycline]] 100 mg PO qd for 6 weeks {{or}} 200 mg PO qd for 4 weeks) {{then}} [[Ivermectin]] after 4-6 months 150 μg/kg single dose
::* Preferred regimen (3): [[Doxycycline]] 200 mg PO qd for 6 weeks {{then}} [[Ivermectin]] after 4-6 months 150 μg/kg single dose


==External links==
==Case Studies==
* Introductory guide to Loiasis at [http://www.stanford.edu/class/humbio103/ParaSites2006/Loiasis/Index.html Loa Loa - The African Eye Worm] By: L. Borg. Stanford University, USA.
[[Loa loa filariasis case study one|Case #1]]
* [http://maven.smith.edu/~sawlab/fgn/pnb/loaloa.html Loa Loa: a cutaneous filarial parasite of humans]. The Filarial Genome Network
* [http://www.soton.ac.uk/~ceb/Diagnosis/Vol10.htm A to Z Guide to Parasitology''. Volume 10. The Blood Nematodes]. By: M. Arcari, A. Baxendine and C. E. Bennett. University of Tehehehe! Southampton, UK.
* [http://www.emedicine.com/med/topic794.htm Filariasis]. eMedicine.
{{Helminthiases}}


==External Links==
* [http://www.cdc.gov/parasites/loiasis/ CDC Fact Sheet]
[[Category:Parasitic diseases]]
[[Category:Parasitic diseases]]
[[Category:Dermatology]]
[[Category:Dermatology]]
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[[Category:Disease]]
[[Category:Disease]]


[[Category:Infectious disease]]
 


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==References==
{{reflist|2}}

Latest revision as of 18:12, 18 September 2017

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Kalsang Dolma, M.B.B.S.[2]

Synonyms and keywords: African eye worm; loaiasis; loiasis; loaina; filaria loa; filaria lacrimalis; filaria subconjunctivalis; fugitive swellings; microfilaria diurnal

Overview

Historical Perspective

Pathophysiology

Causes

Differentiating Loa Loa Filariasis from other Diseases

Epidemiology and Demographics

Risk Factors

Natural History, Complications and Prognosis

Diagnosis

History and Symptoms | Physical Examination | Laboratory Findings | Other Diagnostic Studies

Treatment

Medical Therapy | Surgery | Primary Prevention | Cost-Effectiveness of Therapy | Future or Investigational Therapies

  • Cutaneous filariasis - Loa loa, onchocercia volvulus[1][2]
  • Preferred regimen (1): Doxycycline 150 μg/kg single dose
  • Preferred regimen (2): (Doxycycline 100 mg PO qd for 6 weeks OR 200 mg PO qd for 4 weeks) THEN Ivermectin after 4-6 months 150 μg/kg single dose
  • Preferred regimen (3): Doxycycline 200 mg PO qd for 6 weeks THEN Ivermectin after 4-6 months 150 μg/kg single dose

Case Studies

Case #1

External Links



de:Loiasis

Template:WH Template:WS

References

  1. ↑ Taylor MJ, Hoerauf A, Bockarie M (2010). "Lymphatic filariasis and onchocerciasis". Lancet. 376 (9747): 1175–85. doi:10.1016/S0140-6736(10)60586-7. PMID 20739055.
  2. ↑ Knopp S, Steinmann P, Hatz C, Keiser J, Utzinger J (2012). "Nematode infections: filariases". Infect Dis Clin North Am. 26 (2): 359–81. doi:10.1016/j.idc.2012.02.005. PMID 22632644.
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