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Loiasis

Disease Details

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Description: Loiasis is a parasitic infection caused by the Loa loa filarial worm, transmitted to humans through the bite of an infected deer fly (Chrysops species), leading to symptoms such as recurrent localized angioedema (Calabar swellings), fever, and visible migration of the adult worm under the skin or across the eye.
Type: Loiasis is a parasitic infection caused by the nematode Loa loa. It is not a genetically transmitted disease but rather an infectious disease transmitted through the bite of infected deer flies, specifically of the Chrysops genus.
Signs And Symptoms: A filariasis such as loiasis most often consists of asymptomatic microfilaremia. Some patients can develop lymphatic dysfunction causing lymphedema. Episodic angioedema (Calabar swellings) in the arms and legs, caused by immune reactions, are common. Calabar swellings are 3–10 cm (1.2–3.9 in) in surface area, sometimes erythematous, and not pitting. When chronic, they can form cyst-like enlargements of the connective tissue around the sheaths of muscle tendons, becoming very painful when moved. The swellings may last for one to three days and may be accompanied by localized urticaria (skin eruptions) and pruritus (itching). They reappear at referent locations at irregular time intervals. Subconjunctival migration of an adult worm to the eyes can also occur frequently, and 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 minutes. Eyeworms affect men and women equally, but advanced age is a risk factor. Eosinophilia is often prominent in filarial infections. Dead worms may cause chronic abscesses, which may lead to the formation of granulomatous reactions and fibrosis.In the human host, Loa loa larvae migrate to the subcutaneous tissue, where they mature to adult worms in approximately one year, but sometimes up to four years. Adult worms migrate in the subcutaneous tissues at a speed less than 1 cm/min, mating and producing more microfilariae. The adult worms can live up to 17 years in the human host.
Prognosis: Loiasis, also known as African eye worm, has a variable prognosis depending on the extent and location of the infection. Most individuals with loiasis may remain asymptomatic or experience mild symptoms. However, complications can arise, including Calabar swellings, eye worm migration, and in rare cases, severe systemic issues such as nephropathy or encephalopathy. Effective antiparasitic treatment generally leads to a favorable prognosis, but ongoing exposure in endemic areas can result in repeated infections. Regular medical follow-up is often recommended for managing potential complications.
Onset: The onset of loiasis, also known as African eye worm, can vary. Symptoms typically begin to appear months to years after a person has been bitten by an infected deerfly.
Prevalence: The prevalence of loiasis, a parasitic infection caused by the Loa loa worm, is primarily found in Central and West Africa. It most commonly affects countries such as Cameroon, Gabon, Congo, Nigeria, and the Central African Republic. The prevalence can vary widely within these regions, but in some areas, it can affect up to 70% of the population.
Epidemiology: As of 2009, loiasis is endemic to 11 countries, all in western or central Africa, and an estimated 12–13 million people have the disease. The highest incidence is seen in Cameroon, Republic of the Congo, Democratic Republic of Congo, Central African Republic, Nigeria, Gabon, and Equatorial Guinea. The rates of Loa loa infection are lower but it is still present in and Angola, Benin, Chad and Uganda. The disease was once endemic to the western African countries of Ghana, Guinea, Guinea Bissau, Ivory Coast and Mali but has since disappeared.Throughout Loa loa-endemic regions, infection rates vary from 9 to 70 percent of the population. Areas at high risk of severe adverse reactions to mass treatment (with Ivermectin) are at present determined by the prevalence in a population of >20% microfilaremia, which has been recently shown in eastern Cameroon (2007 study), for example, among other locales in the region.Endemicity is closely linked to the habitats of the two known human loiasis vectors, Chrysops dimidiata and C. silicea.Cases have been reported on occasion in the United States but are restricted to travelers who have returned from endemic regions.In the 1990s, the only method of determining Loa loa intensity was with microscopic examination of standardized blood smears, which is not practical in endemic regions. Because mass diagnostic methods were not available, complications started to surface once mass ivermectin treatment programs started being carried out for onchocerciasis, another filariasis. Ivermectin, a microfilaricidal drug, may be contraindicated in patients who are co-infected with loiasis and have associated high microfilarial loads. The theory is that the killing of massive numbers of microfilaria, some of which may be near the ocular and brain region, can lead to encephalopathy. Indeed, cases of this have been documented so frequently over the last decade that a term has been given for this set of complication: neurologic serious adverse events (SAEs).Advanced diagnostic methods have been developed since the appearance the SAEs, but more specific diagnostic tests that have been or are currently being development (see: Diagnostics) must to be supported and distributed if adequate loiasis surveillance is to be achieved.There is much overlap between the endemicity of the two distinct filariases, which complicates mass treatment programs for onchocerciasis and necessitates the development of greater diagnostics for loiasis.In Central and West Africa, initiatives to control onchocerciasis involve mass treatment with ivermectin. However, these regions typically have high rates of co-infection with both L. loa and O. volvulus, and mass treatment with ivermectin can have SAE. These include hemorrhage of the conjunctiva and retina, heamaturia, and other encephalopathies that are all attributed to the initial L. loa microfilarial load in the patient prior to treatment. Studies have sought to delineate the sequence of events following ivermectin treatment that lead to neurologic SAE and sometimes death, while also trying to understand the mechanisms of adverse reactions to develop more appropriate treatments.In a study looking at mass ivermectin treatment in Cameroon, one of the greatest endemic regions for both onchocerciasis and loiasis, a sequence of events in the clinical manifestation of adverse effects was outlined.It was noted that the patients used in this study had a L. loa microfilarial load of greater than 3,000 per ml of blood.Within 12–24 hours post-ivermectin treatment (D1), individuals complained of fatigue, anorexia, and headache, joint and lumbar pain—a bent forward walk was characteristic during this initial stage accompanied by fever. Stomach pain and diarrhea were also reported in several individuals.By day 2 (D2), many patients experienced confusion, agitation, dysarthria, mutism and incontinence. Some cases of coma were reported as early as D2. The severity of adverse effects increased with higher microfilarial loads. Hemorrhaging of the eye, particularly the retinal and conjunctiva regions, is another common sign associated with SAE of ivermectin treatment in patients with L. loa infections and is observed between D2 and D5 post-treatment. This can be visible for up to 5 weeks following treatment and has increased severity with higher microfilarial loads.Haematuria and proteinuria have also been observed following ivermectin treatment, but this is common when using ivermectin to treat onchocerciasis. The effect is exacerbated when there are high L. loa microfilarial loads however, and microfilariae can be observed in the urine occasionally. Generally, patients recovered from SAE within 6–7 months post-ivermectin treatment; however, when their complications were unmanaged and patients were left bed-ridden, death resulted due to gastrointestinal bleeding, septic shock, and large abscesses.Mechanisms for SAE have been proposed. Though microfilarial load is a major risk factor to post-ivermectin SAE, three main hypotheses have been proposed for the mechanisms.The first mechanism suggests that ivermectin causes immobility in microfilariae, which then obstructs microcirculation in cerebral regions. This is supported by the retinal hemorrhaging seen in some patients, and is possibly responsible for the neurologic SAE reported.The second hypothesis suggests that microfilariae may try to escape drug treatment by migrating to brain capillaries and further into brain tissue; this is supported by pathology reports demonstrating a microfilarial presence in brain tissue post-ivermectin treatment.Lastly, the third hypothesis attributes hypersensitivity and inflammation at the cerebral level to post-ivermectin treatment complications, and perhaps the release of bacteria from L. loa after treatment to SAE. This has been observed with the bacteria Wolbachia that live with O. volvulus.More research into the mechanisms of post-ivermectin treatment SAE is needed to develop drugs that are appropriate for individuals with multiple parasitic infections.One drug that has been proposed for the treatment of onchocerciasis is doxycycline. This drug has been shown to be effective in killing both the adult worm of O. volvulus and Wolbachia, the bacteria believed to play a major role in the onset of onchocerciasis, while having no effect on the microfilariae of L. loa. In a study done at five different co-endemic regions for onchocerciasis and loiasis, doxycycline was shown to be effective in treating over 12,000 individuals infected with both parasites with minimal complications. Drawbacks to using doxycycline include bacterial resistance and patient compliance because of a longer treatment regimen and emergence of doxycycline-resistant Wolbachia. However, in the study over 97% of the patients complied with treatment, so it does pose as a promising treatment for onchocerciasis, while avoiding complications associated with L. loa co-infections.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 Ogooué River. Humans are the only known natural reservoir. It is estimated that over 10 million humans are infected with Loa loa larvae.An area of tremendous concern regarding loiasis is its co-endemicity with onchocerciasis in certain areas of west and central Africa, as mass ivermectin treatment of onchocerciasis can lead to SAEs in patients who have high Loa loa microfilarial densities, or loads. This fact necessitates the development of more specific diagnostics tests for Loa loa so that areas and individuals at a higher risk for neurologic consequences can be identified prior to microfilaricidal treatment. Additionally, the treatment of choice for loiasis, diethylcarbamazine, can lead to serious complications in and of itself when administered in standard doses to patients with high Loa loa microfilarial loads.
Intractability: Loiasis, also known as African Eye Worm infection, is not typically considered intractable. It is caused by the parasitic worm Loa loa and is transmitted through the bite of deerflies. Treatment primarily involves the use of antiparasitic medications such as diethylcarbamazine (DEC) or albendazole, which are generally effective in eliminating the parasite. However, management can be challenging in heavily infected individuals or in those with high levels of microfilariae in the blood, due to potential severe adverse reactions. Nonetheless, with appropriate medical care, loiasis can often be successfully treated.
Disease Severity: Loiasis, also known as African eye worm, is typically considered a mild disease in most cases. Symptoms can include itching, hives, and the visible movement of the worm across the eye or under the skin, which can cause discomfort and anxiety. Severe complications are rare but can occur, such as encephalitis or kidney damage, particularly if the infection is not properly treated. However, most individuals with loiasis do not experience serious or life-threatening symptoms.
Healthcare Professionals: Disease Ontology ID - DOID:13523
Pathophysiology: Loiasis, also known as African eye worm, is caused by the parasitic worm *Loa loa*, which is transmitted to humans through the bite of an infected deer fly or mango fly. The pathophysiology involves the following steps:

1. **Transmission**: During a fly bite, *Loa loa* larvae are deposited onto the skin and enter through the wound created by the bite.
2. **Larval Migration**: The larvae penetrate the subcutaneous tissues and undergo maturation into adult worms over several months.
3. **Adult Worms**: Mature adult worms can live for years in the subcutaneous tissues, causing localized inflammation and the migration of worms, which is the hallmark of the disease.
4. **Calabar Swellings**: These are localized, temporary swellings, often accompanied by itching, which occur as the adult worms migrate under the skin.
5. **Ocular Involvement**: In some cases, the adult worm can migrate to the eye, causing symptoms like eye pain, visible worms in the conjunctiva, and rarely, vision problems.
6. **Immune Response**: The host's immune system responds to the presence of the worms with eosinophilia and elevated IgE levels.

Patients may be asymptomatic or experience episodic symptoms linked to the worm's migration and the body's inflammatory response.
Carrier Status: Loiasis is primarily spread through the bite of an infected deer fly, specifically the species Chrysops. Humans are the main definitive host for the parasitic worm Loa loa, but the fly acts as the vector, not a carrier in the traditional sense. The term "carrier status" in this context typically doesn't apply to non-human vectors like the deer fly. Humans infected with Loa loa harbor the adult worms and can have microfilariae in their bloodstream, which can then be picked up by biting flies, continuing the life cycle.
Mechanism: Loiasis, also known as African eye worm, is caused by the parasitic nematode Loa loa. Here's an overview of its mechanism and molecular mechanisms:

**Mechanism:**
1. **Transmission:** Loa loa is transmitted to humans through the bite of infected deer flies (genus Chrysops).
2. **Lifecycle:** The larvae (microfilariae) enter the human bloodstream after a bite and mature into adult worms in subcutaneous tissues.
3. **Migration:** Adult worms migrate through the subcutaneous tissue and can cross the eye, leading to characteristic manifestations such as "Calabar swelling" (localized angioedema) and visible worms in the conjunctiva.

**Molecular Mechanisms:**
1. **Immune Evasion:** Loa loa has evolved mechanisms to evade the host's immune response. The worms secrete molecules that modulate local immune responses, reducing inflammation and preventing effective immune clearance.
2. **Gene Expression:** Recent studies have provided insights into the genomic and transcriptomic profiles of Loa loa, revealing genes involved in immune modulation, motility, and metabolism. The exact genes and pathways are subjects of ongoing research.
3. **Host Interaction:** Secreted proteins, such as cysteine protease inhibitors, help the parasite degrade host tissue barriers and evade immune responses.

Understanding these mechanisms is crucial for developing effective treatments and diagnostic tools for loiasis.
Treatment: Treatment of loiasis involves chemotherapy or, in some cases, surgical removal of adult worms followed by systemic treatment. The current drug of choice for therapy is diethylcarbamazine (DEC), though ivermectin use while not curative (i.e., it will not kill the adult worms) can substantially reduce the microfilarial load. The recommended dosage of DEC is 8–10 mg/kg/d taken three times daily for 21 days per CDC. The pediatric dose is the same. DEC is effective against microfilariae and somewhat effective against macrofilariae (adult worms). The recommended dosage of ivermectin is 150 µg/kg in patients with a low microfilaria load (with densities less than 8000 mf/mL).In patients with high microfilaria load and/or the possibility of an onchocerciasis coinfection, treatment with DEC and/or ivermectin may be contraindicated or require a substantially lower initial dose, as the rapid microfilaricidal actions of the drugs can provoke encephalopathy. In these cases, initial albendazole administration has proved helpful (and is superior to ivermectin, which can also be risky despite its slower-acting microfilaricidal effects over DEC). The CDC recommended dosage for albendazole is 200 mg taken twice a day for 21 days. Also, in cases where two or more DEC treatments have failed to provide a cure, subsequent albendazole treatment can be administered.Management of Loa loa infection in some instances can involve surgery, though the timeframe during which surgical removal of the worm must be carried out is very short. A detailed surgical strategy to remove an adult worm is as follows (from a real case in New York City). The 2007 procedure to remove an adult worm from a male Gabonian immigrant employed proparacaine and povidone-iodine drops, a wire eyelid speculum, and 0.5 ml 2% lidocaine with epinephrine 1:100,000, injected superiorly. A 2-mm incision was made and the immobile worm was removed with forceps. Gatifloxacin drops and an eye-patch over ointment were utilized post surgery and there were no complications (unfortunately, the patient did not return for DEC therapy to manage the additional worm—and microfilariae—present in his body).
Compassionate Use Treatment: For loiasis, compassionate use treatments, off-label, or experimental treatments may include:

1. **Albendazole:** While not FDA-approved specifically for loiasis, albendazole has been used off-label to reduce microfilariae levels in the blood, making ivermectin treatment safer.

2. **Doxycycline:** This antibiotic targets the endosymbiotic bacteria Wolbachia within the worms, potentially affecting the viability and fertility of Loa loa. Its use is considered experimental.

3. **Alternative Anti-filarial Drugs:** Medications such as flubendazole and other anti-filarial agents are occasionally considered in experimental settings, although their efficacy and safety profiles require further investigation.

Always consult with an infectious disease specialist experienced in treating loiasis for the most appropriate and individualized treatment plan.
Lifestyle Recommendations: ### Lifestyle Recommendations for Loiasis

1. **Avoid Infected Areas**: Loiasis is primarily found in certain regions of West and Central Africa. If you are traveling or living in these areas, take extra precautions.

2. **Insect Repellent**: Use insect repellents containing DEET or picaridin on exposed skin to ward off the deer flies that transmit the disease.

3. **Protective Clothing**: Wear long-sleeved shirts and long pants, especially during the daytime when deer flies are most active.

4. **Insect-Proof Housing**: Use screens and nets, and consider staying in air-conditioned accommodations to reduce the risk of fly bites.

5. **Regular Medical Checkups**: If you live in or have traveled to endemic areas, regular medical checkups can help in early detection and treatment.

6. **Avoid Outdoor Activities During Peak Fly Activity**: Try to reduce time spent outside during peak fly-biting times, usually during mid-morning and late afternoon.

7. **Community Awareness and Education**: Engage in local educational programs to increase awareness about loiasis and its prevention.

Taking these steps can greatly reduce the risk of contracting loiasis.
Medication: Loiasis, also known as African eye worm, is treated with antiparasitic medications. The primary treatments include:

1. **Diethylcarbamazine (DEC)**: It is the drug of choice and is typically given in a course of several weeks. It effectively kills both the adult worms and the microfilariae.

2. **Albendazole**: This may be used in cases where DEC is contraindicated or if there is a high risk of adverse reactions due to heavy microfilariae loads.

3. **Ivermectin**: Generally, it is not used as the primary treatment for loiasis due to the risk of severe adverse reactions caused by the rapid killing of microfilariae in patients with high microfilarial loads.

Patients should be managed by a healthcare provider experienced in treating loiasis, especially since monitoring for adverse effects is essential.
Repurposable Drugs: For loiasis, which is caused by the Loa loa parasitic worm, the repurposable drugs include:

1. **Albendazole**: Primarily an anti-helminthic, it has shown effectiveness in reducing microfilariae levels in some loiasis cases.
2. **Doxycycline**: Commonly used as an antibiotic, it can target the Wolbachia bacteria that symbiotically thrive within filarial parasites, indirectly affecting the Loa loa worms.

"nan" is irrelevant to this context. It's commonly used to represent 'not a number' or missing/undefined values in data, and does not pertain to the treatment of loiasis.
Metabolites: Loiasis, also known as African eye worm, is caused by the parasitic worm Loa loa. Metabolites specifically related to loiasis are not well-documented. Generally, the presence of the worm and immune response may affect certain metabolic pathways. Laboratory diagnosis often involves identification of microfilariae in blood samples rather than specific metabolite detection.
Nutraceuticals: There are no specific nutraceuticals known to prevent or treat loiasis, a parasitic infection caused by the Loa loa worm. Treatment typically involves antiparasitic medications prescribed by a healthcare professional.
Peptides: Loiasis is a parasitic disease caused by the filarial nematode Loa loa, also known as the African eye worm. It is primarily transmitted through the bite of deer flies from the Chrysops genus. The disease is prevalent in West and Central Africa.

- **Peptides**: Research into Loa loa and its interactions with the host immune system has identified several potential peptides that may be involved in immune modulation or may serve as markers for infection. Diagnostic peptides specific to Loa loa antigens have been explored to improve diagnostic accuracy.

- **Nanotechnology**: Innovative approaches using nanotechnology are being explored for the diagnosis and treatment of loiasis. Nanoparticles and nanodevices may be utilized for targeted drug delivery, improving the efficacy and reducing the side effects of antiparasitic treatments. Additionally, nanosensors could potentially enhance the sensitivity and specificity of diagnostic tests for detecting Loa loa infections.