User Tools

Site Tools



Related Terms: lymphatic filariasis, lymphedema, leg lymphedema, Calabar swellings, Fugitive swelling, Tropical swelling, Deer fly or Mango fly , Chrysops spp, African eye worm, Loaina, Filaria loa, Filaria lacrimalis, Filaria subconjunctivalis, eye infections, parasitic, microfilaremia, ivermectin, adverse reaction, Nigeria, ribosomal DNA ITS1, PCR-RFLP, ribosomal deoxyribonucleic acid (DNA, Mansonella, onchocerciasis, river blindness, perstans, Loa loa filariasis.

Description and Discussion

Another type of filariasis.” Loaisis or loa loa filariasis is caused by the parasitic worm Loa Loa versus either the Wuchereria bancrofti,or the Brugia malayi. Like mosquitos, they bite animals as blood is their main food. Most of this filariasis occurs in the rain forest of west and central Africa. It actually commonly involves the eyes. But it can first appear on the skin with itchy swelling which is referred to Calabar swellings. These non-tender swellings are genrally found on the limbs and joints.

The first case of Loa loa infection was noted in the Caribbean (Santo Domingo) in 1770. A French surgeon named Mongin tried but failed to remove a worm passing across a woman's eye. A few years later, in 1778, the surgeon François Guyot noted worms in the eyes of West African slaves on a French ship to America; he successfully removed a worm from one man's eye. (1)

The eye worm migrates across the eye (visible) . It lasts less then a week and causes little actual damage to the eye itself. Increased numbers of eosinophils are usually found on blood tests. Persons with long-term infection might develop kidney damage through immune complex deposition, though progression to chronic kidney disease is not common. Other uncommon manifestations include inflammation of the lymph glands, scrotal swellings, and lung infiltrates along with collections of fluid around the lung. Loiasis may also be associated with scarring of heart muscle.

The loa loa parasite georgraphic distribution extends from Benin to southern Sudan and Uganda, It is estimate to afflict somewhere between 3 and 13 million people.

The most at risk group are those who live in the high-canopied rain forests. The insects involved in transmission flies of the genus C. silacea and C. dimidiate (deeflies). and typically bites during the day. Also, with the increasing amount of tourists, travelers into these countries are at risk with the long term visitor being more endangered. A traveler's risk for infection likely will depend on the number of bites received and the number of infected deerflies in the area visited.

The flies introduce third-stage larvae into the skin wound. The developing larvae then commonly reside in the 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 spinal fluids, urine, and sputum. During the day they are found in peripheral blood, but during the noncirculation phase, they are found in the lungs. he fly ingests microfilariae during a blood meal.

After ingestion, the microfilariae lose their sheaths and migrate from the fly's midgut through the 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 (2)


An early diagnoses is difficult as the patient may have low lever of larvae in the blood. The disease is generally diagnosed through four methods.

(1) Identification of the worm after removal from the body (2) Identificatino of the worm in the eye (3) Identification of the larvae in the patients blood, taken from 10AM to 2PM (4) Identification of the antibodies against L. Loa. The identification may not differentiate between an active infection, a past infection or exposure.

The tests for the antibodies include LlSXP-1 recombinant antigen which can be used in both an ELISA and a luciferase immunoprecipitation systems (LIPS) assay.

There is one polymerase chain reaction (PCR) test for loiasis approved for diagnosis in the United Stated.


Leg lymphedema, arm lymphedema, encephalitis (inflammation of the brain tissues); Cerebral edema (fatal cases).

Urticaria, pruritus, and chorioretinitis may also occur.


Treatment includes surgery to remove to worm from the eye or skin. The two antiparasitic agents commonly used in treatment include diethylcarbamazine (DEC), which kills both the larvae and the adult worms and is the treatment of choice, and albendazole, which is thought to kill the adult worms. Diethylcarbamazine (DEC). It is given orally in a dose of 6mg/ kg/day taken 3 times daily for 12 days.

Complications from treatment involves a danger of fetal brain inflammation.

DEC is not typically given to children under 2 years old. Albendazole can be given to children as young as 12 months old, though a reduction in dose may be required.


While there are no vaccines available to prevent people from being infected. Diethylcarbamazine (DEC) 300mg taken once a week is effective at preventing loiasis in long-term travelers to affected areas.

The flies breed in muddy shaded areas, so visitors should avoid thewse. Wearing oa insect repellants containing DEET is important. Finally, wearing long sleeves and long pants during the day (permethrin- treated clothes) can help prevent the insects from biting.

(1) Loa Loa filariasis

(2) Centers for Disease Control and Prevention

*Life cycle image and information courtesy ofDPDx.

Abstracts and Studies

Imported Loa loa filariasis: three cases and a review of cases reported in non-endemic countries in the past 25 years.

July 2012

Antinori S, Schifanella L, Million M, Galimberti L, Ferraris L, Mandia L, Trabucchi G, Cacioppo V, Monaco G, Tosoni A, Brouqui P, Gismondo MR, Giuliani G, Corbellino M.

Corresponding Editor: William Cameron, Ottawa, Canada.


Department of Clinical Sciences L Sacco, Section of Infectious Diseases and Immunopathology, Università degli Studi di Milano, Via GB Grassi, 74, 20157 Milan, Italy.


Keywords Loa loa; African eye worm; Imported filariasis; Calabar swellings; Treatment

OBJECTIVES: The aim of this study was to highlight the increasing chance of Western physicians encountering patients (both immigrants and expatriates/travelers) seeking help for loiasis.

METHODS: We describe three cases of imported loiasis observed at two hospitals in Italy and France, and present a review of all previously published cases in the medical literature in the last 25 years (1986-2011). The search was performed using PubMed and Scopus databases using the terms “Loa loa” AND “loiasis”.

RESULTS: We reviewed 101 cases of imported loiasis of which 61 (60.4%) were reported from Europe and 31 (30.7%) from the USA. Seventy-five percent of infestations were acquired in three countries: Cameroon, Nigeria, and Gabon. Overall, peripheral blood microfilariae were detected in 61.4% of patients, eosinophilia in 82.1%, eye worm migration in 53.5%, and Calabar swellings in 41.6%. However, Calabar swellings and eosinophilia were more common among expatriates/travelers, whereas African immigrants were more likely to have microfilaremia. Eye worm migration was observed in a similar proportion in the two groups. Only 35 patients (including the three described here) underwent clinical follow-up for a median period of 10.5 months (range 1-84 months); clinical relapse occurred in three of these patients and persistence or reappearance of blood microfilaria in another two.

CONCLUSIONS: Due to increasing travel and the migration of people from the endemic countries of West Africa to Europe and the USA, we speculate on the possible emergence of loiasis. Western physicians should be aware of the typical (eye worm migration and Calabar swellings) as well as unusual clinical presentations.


Ocular onchocerciasis: current management and future prospects. 2011

Babalola OE.



Department of Ophthalmological Surgery, Bingham University Teaching Hospital, New Karu, Nassarawa State, Nigeria.


Keywords: onchocerciasis, river blindness, ocular, management

This paper reviews the current management of onchocerciasis and its future prospects. Onchocerciasis is a disease affecting millions of people in Africa, South and Central America, and Yemen. It is spread by the blackfly as a vector and caused by the filarial nematode, Onchocerca volvulus. A serious attempt was made by the Onchocerciasis Control Program between 1975 and 2002 to eliminate the vector in eleven of the endemic countries in West Africa, and with remarkable success. Formerly, the treatment was with diethyl carbamazine for the microfilaria and suramin for the adult worm. These drugs are now known to be toxic and unsuitable for mass distribution.

In particular, they precipitate optic nerve disease. With the discovery of ivermectin, a much safer microfilaricide, and the decision of Merck to distribute the drug free of charge for as long as needed, the strategy of control switched to mass drug administration through community-directed treatment with ivermectin. So far, millions have received this annual or biannual treatment through the African Program for Onchocerciasis Control and the Onchocerciasis Elimination Program for the Americas. However, the problem with ivermectin is that it is a monotherapy microfilaricide which has limited effect on the adult worm, and thus will need to be continued for the life span of the adult worm, which may last up to 15 years.

There are also early reports of resistance. Serious encephalopathy and death may occur when ivermectin is used in subjects heavily infested with loiasis. It seems unlikely that a break in transmission will occur with community-directed treatment with ivermectin in Africa because of population migrations and the highly efficient vector, but in the Americas some countries such as Columbia and the Oaxaca focus in Mexico have reported eradication. Vector control is only now applicable in selected situations, and particularly to control the nuisance value of the blackfly. Trials are ongoing for alternatives to ivermectin. Candidate drugs include moxidectin, a macrofilaricide, doxycycline which targets the Wolbachia endosymbiont, and flubendazole, which shows promise with the newer oral cyclodextrin formulation.


Integrated rapid mapping of onchocerciasis and loiasis in the Democratic Republic of Congo: impact on control strategies.

Sept 2011

Tekle AH, Zoure H, Wanji S, Leak S, Noma M, Remme JH, Amazigo U.


African Program for Onchocerciasis Control, Epidemiology and Vector Elimination, Rue Naba Zombre 1538, Sector 9 Door Number 1473, Ougadougou, Burkina Faso.


Keywords: Onchocerciasis; Loasis; Integrated mapping; CDTi; Sever adverse event

BACKGROUND: Onchocerciasis can be effectively controlled by annual mass treatment with ivermectin in endemic communities. However, in communities that are endemic for loiasis there may be significant risk of severe adverse reactions after ivermectin treatment. Planning of control requires therefore mapping of these two infections using rapid assessment tools developed for each disease. These tools were initially implemented independently till the feasibility of combining them was demonstrated. This paper reports the results of integrated mapping in four epidemiological zones in the Democratic Republic of Congo and its implications on operational decision-making on ivermectin treatment.

METHODS: Rapid assessment surveys were conducted between 2004 and 2005 using both rapid epidemiological mapping of onchocerciasis (REMO) and rapid assessment procedure for loiasis (RAPLOA). The survey results were subjected to a spatial analysis in order to generate for each of the two diseases maps of the estimated prevalence of infection throughout the four zones.

RESULTS: Surveys were undertaken in 788 villages where 25,754 males were examined for palpable onchocercal nodules and 62,407 people were interviewed for history of eye worm. The results showed major differences in the geographic distribution of the two diseases. Loiasis was highly endemic in some areas, where special precautions were required, but not in others where routine ivermectin treatment could proceed.

CONCLUSION: Integrated rapid mapping of onchocerciasis and loiasis reduces both time and cost of surveys and greatly facilitates operational decision-making on ivermectin treatment in areas where loiasis might be co-endemic.


Loa loa filariasis in Italy: review of the literature with a clinical report

Sept 2011

[Article in Italian]

Sgrelli A, De Socio GV, Papili R, D'Annibale ML, Baldelli F.


Struttura Complessa di Malattie Infettive, Ospedale Santa Maria della Misericordia, Universita degli studi di Perugia, Perugia, Italy.


We present the case of an asymptomatic Loa loa disease in a 28-year-old Nigerian man living in Italy for 5 years. The man was admitted to our clinic for an occasional identification of hypereosinophilia (white blood cell count 5440/mmc, eosinophil 42%) and the presence of microfilaria at an hemoscopic evaluation. The diagnosis was made by testing the diurnal peripheral blood that showed a parasitaemia of 7000 microfilia/mL. The patient was treated with ivermectin 12 mg on the first day followed by albendazole 400 mg every 12 hours for 21 days with a reduction but no negativization of the parasitaemia and no collateral effect. Filariasis should be considered in all patients who come from or have stayed in endemic areas or who present alterations in the leukocyte formula, including hypereosinophilia, or some unexplainable allergic disorders. The lab diagnosis can be conducted through a hemoscopic test or directly with the identification of the adult worm, whereas the parasitaemia can be evaluated only through a hemoscopic test. The therapy can be non-conclusive or carried out with difficulty as finding diethylcarbamazine may be a hard task or potentially fatal anaphylactic reactions may occur.

Le Infezioni in Medicina

Rapid molecular assays for specific detection and quantitation of Loa loa microfilaremia.

Aug 2011

Fink DL, Kamgno J, Nutman TB.


Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America. E-mail:


BACKGROUND: Accurate diagnosis of Loa loa infection is essential to the success of mass drug administration efforts to eliminate onchocerciasis and lymphatic filariasis, due to the risk of fatal encephalopathic reactions to ivermectin occurring among highly microfilaremic Loa-infected individuals living in areas co-endemic for multiple filarial species.

METHODOLOGY/PRINCIPAL FINDINGS: From a pool of over 1,800 L. loa microfilaria (mf) expressed sequence tags, 18 candidate L. loa mf-specific PCR targets were identified. Real-time PCR (qPCR) assays were developed for two targets (LLMF72 and LLMF269). The qPCR assays were highly specific for L. loa compared with related filariae and also highly sensitive, with detection limits of 0.1 pg genomic DNA, or 1% of DNA extracted from normal blood spiked with a single L.loa microfilaria. Using various DNA extraction methods with dried blood spots obtained from Cameroonian subjects with parasitologically proven loiasis, the LLMF72 qPCR assay successfully estimated mf burden in 65 of 68 samples (50-96,000 mf/mL by microscopy), including all 12 samples subjected to a simple 10-minute boiling extraction. Additionally, the assay detected low-level microfilaremia among 5 of 16 samples from patients thought to be amicrofilaremic by microscopy.

CONCLUSIONS/SIGNIFICANCE: This novel, rapid, highly sensitive and specific qPCR assay is an important step forward in the laboratory diagnosis of L. loa infection.


The geographic distribution of Loa loa in Africa: results of large-scale implementation of the Rapid Assessment Procedure for Loiasis (RAPLOA).

June 2011

Zouré HG, Wanji S, Noma M, Amazigo UV, Diggle PJ, Tekle AH, Remme JH.


African Programme for Onchocerciasis Control, World Health Organization, Ouagadougou, Burkina Faso.


BACKGROUND: Loiasis is a major obstacle to ivermectin treatment for onchocerciasis control and lymphatic filariasiselimination in central Africa. In communities with a high level of loiasis endemicity, there is a significant risk of severe adverse reactions to ivermectin treatment. Information on the geographic distribution of loiasis in Africa is urgently needed but available information is limited. The African Programme for Onchocerciasis Control (APOC) undertook large scale mapping of loiasis in 11 potentially endemic countries using a rapid assessment procedure for loiasis (RAPLOA) that uses a simple questionnaire on the history of eye worm.

METHODOLOGY/PRINCIPAL FINDINGS: RAPLOA surveys were done in a spatial sample of 4798 villages covering an area of 2500×3000 km centred on the heartland of loiasis in Africa. The surveys showed high risk levels of loiasis in 10 countries where an estimated 14.4 million people live in high risk areas. There was a strong spatial correlation among RAPLOA data, and kriging was used to produce spatially smoothed contour maps of the interpolated prevalence of eye worm and the predictive probability that the prevalence exceeds 40%.

CONCLUSION/SIGNIFICANCE: The contour map of eye worm prevalence provides the first global map of loiasis based on actual survey data. It shows a clear distribution with two zones of hyper endemicity, large areas that are free of loiasis and several borderline or intermediate zones. The surveys detected several previously unknown hyperendemic foci, clarified the distribution of loiasis in the Central African Republic and large parts of the Republic of Congo and the Democratic Republic of Congo for which hardly any information was available, and confirmed known loiasis foci. The new maps of the prevalence of eye worm and the probability that the prevalence exceeds the risk threshold of 40% provide c


Assessment of loiasis and outcomes of ivermectin mass treatment in Ijebu-North, Nigeria.

June 2011

Hassan AA, Akinsanya B, Iyase N, Owagboriaye FO.


Department of Zoology, University of Ibadan, Nigeria.


Keywords: Loa loa; Mansonella perstans; Wuchereria bancrofti; ITS1; PCR–RFLP; Nested-PCR; Differential detection

A total of 286 individuals from 3 selected communities (Areedi-Aje, Ipakodo/Ojokodo, and Ijebu-Igbo) of Ijebu-North, southwestern Nigeria were examined for Loa loa microfilaremia using finger prick blood smear, between December 2008 and March 2009. Rapid assessment procedure for loiasis (RAPLOA) was used to obtain information, from 187 Ijebu-Igbo residents, on adverse reactions experienced from retrospective treatments with ivermectin and history of eye worm. Only 33.9% of the respondents reported having had a history of eye worm while 33.2% had microfilaremia. The demographic factor of gender was not significant determinants of the prevalence (P>0.05) while age was significant (P<0.05). The highest prevalence of eye worm history and microfilaremia were recorded in 61-70 and 15-20 years of age categories, respectively. Ijebu-Igbo had 27.3% eye worm history, 32.1% microfilaremia, and the highest intensity of 140 microfilariae (mf)/ml. Ipakodo area had the highest eye worm history of 54.4% and the highest intensity of 420 mf/ml. Areedi-Aje had the highest occurrence of 45.2% microfilaremia and the highest intensity of 460 mf/ml. Predictably, Areedi-Aje and Ipakodo areas were high risk communities. The low intensity of L. loa infection with an insignificant (2.1%; P>0.05) adverse reactions from 187 subjects involved in the retrospective ivermectin administration confirmed that ivermectin delivery may be considered safe. The community-directed treatment with ivermectin (CDTI) programme was most probably responsible for the low prevalence and intensity.

Korean Journal of Parasitology

Detection and discrimination of Loa loa, Mansonella perstans and Wuchereria bancrofti by PCR-RFLP and nested-PCR of ribosomal DNA ITS1 region.

Jan. 2011

Jiménez M, González LM, Carranza C, Bailo B, Pérez-Ayala A, Muro A, Pérez-Arellano JL, Gárate T.


Servicio de Parasitología, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain.


The ribosomal deoxyribonucleic acid (DNA) internal transcribed spacer region (ITS1) of two filarial nematodes, Loa loa and Mansonella perstans, was amplified and further sequenced to develop an species-specific polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) protocol for the differentiation of both species from Wuchereria bancrofti, three filarial nematodes with blood circulating microfilariae. The ITS1-PCR product digested with the restriction endonuclease Ase I generated an specific diagnostic pattern for each of the three species. Moreover, three new specific nested-PCRs, targeting the ITS1 region, for differential detection of L. loa, M. perstans and W. bancrofti were developed and used when the ITS1-PCR products were insufficient for the Ase I enzymatic digestion. These filarial species-specific molecular protocols were evaluated in forty blood samples from African adult immigrants attending in the Hospital Insular of Gran Canaria, Canarias, Spain.


Analysis of the mdr-1 gene in patients co-infected with Onchocerca volvulus and Loa loa who experienced a post-ivermectin serious adverse event. July 2010

External Links


ICD-10 B74.3

ICD-9 125.2

DiseasesDB 7576

eMedicine derm/888, med/794

MeSH D008118

Diagnostic Images

The agent stimulates the body's immune system to recognize the agent as foreign, destroy it, and “remember” it, so that the immune system can more easily recognize and destroy any of these microorganisms that it later encounters. Vaccines can be prophylactic (example: to prevent or ameliorate the effects of a future infection by any natural or “wild” pathogen), or therapeutic



Related Lymphedema People Pages

Lymphedema People Resources

loiasis.txt · Last modified: 2012/10/16 14:40 (external edit)