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Questions and Answers
What causes Calabar swellings in patients infected with Loa loa?
Which diagnostic method is typically used to observe the adult Loa loa worm?
What percentage of cases show a positive result in the Complement Fixation Test for Loa loa infection?
Which of the following is NOT a typical cutaneous manifestation of loiasis?
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In which bodily fluid can microfilariae be detected for laboratory confirmation of loiasis?
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Eosinophilia in patients infected with Loa loa typically ranges between what percentage?
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What symptom typically occurs due to adult worms migrating under the conjunctiva?
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What is the common site for Calabar swellings in loiasis patients?
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What is the primary habitat of adult Loa loa worms?
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During which time of day are microfilariae of Loa loa typically present in the blood?
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What type of organism acts as the intermediate host for Loa loa?
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What is the size of adult female Loa loa worms?
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What is the mode of infection for Loa loa in humans?
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What characteristic feature can be observed in microfilariae of Loa loa?
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What is the primary definitive host of Loa loa?
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Which of the following describes the microfilariae of Loa loa?
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Study Notes
Loa Loa (African Eye Worm)
- Loa loa causes loiasis, a disease primarily found in tropical forests of West and Central Africa, including Guinea, Sudan, Nigeria, Zaire, and Cameroon.
Morphology
- Adult Loa loa are smooth, thread-like nematodes; males measure approximately 3 cm x 0.1 mm, while females are around 6 cm x 0.2 mm.
- Microfilariae are embryos released by females, measuring about 250 x 8 µm, lack an alimentary canal, are motile and sheathed, and exhibit a distinctive kinked appearance.
- Microfilariae are most prevalent in the bloodstream during the day, particularly between 10 AM and 2 PM, indicating diurnal periodicity.
Life Cycle
- Adult worms inhabit subcutaneous tissues, migrating sometimes under the conjunctiva, referred to as eye worms.
- Human hosts are definitive hosts; monkeys serve as reservoir hosts, while Chrysops flies (deer flies) act as the vectors.
- Infection occurs when the Chrysops fly bites and transmits the infective filariform larvae into humans.
- Gravid females release microfilariae that enter the bloodstream; microfilariae penetrate the fly's stomach, developing into infective larvae before migrating to the fly’s mouth.
Pathogenesis
- Approximately 12 million people are infected with Loa loa in Tropical Africa.
Clinical Manifestations
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Cutaneous Reactions:
- Urticarial dermatitis results from hypersensitivity to the parasite or its products.
- Calabar (fugitive) swellings are transient, painless swellings occurring near joints or on the head, triggered by allergic reactions to the worms and their antigens.
- These swellings can vary in size and may be potentially dangerous if they occur in the glottis.
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Eye Worm Disease:
- Adult worms can migrate under the conjunctiva, causing temporary inflammation and discomfort without leading to blindness but can form granulomas.
- Symptoms include a creeping sensation, irritation, and proptosis due to orbital edema.
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Other Manifestations:
- Eosinophilia rates of 30-40% are common, whether the worms are alive or dead.
- Serious conditions may arise from CNS invasion, leading to meningoencephalitis with microfilariae in cerebrospinal fluid (CSF).
- Joint-related symptoms can include arthritis and fatigue, with microfilariae detectable in joint fluid.
Diagnosis
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Clinical Diagnosis:
- Direct observation of adult worms under the conjunctiva or nose bridge, and identification of Calabar swellings alongside eosinophilia.
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Laboratory Diagnosis:
- Identification of microfilariae in peripheral blood during daytime via fresh and stained thick smears.
- C.S.F. samples may also detect microfilariae.
- Immunodiagnostic tests, such as Complement Fixation Test (CFT), are positive in 85% of cases.
- Molecular techniques like PCR are also employed.
- Blood tests typically reveal elevated leukocyte counts and eosinophilia (30-40%) alongside elevated serum IgE levels.
Treatment
- Consult a medical professional for specific treatment options available for Loa loa infections.
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Description
This quiz delves into filarial worms, focusing on Loa loa, the African eye worm. It covers its geographical distribution, morphology, and lifecycle, providing insights into its impact on health in tropical regions. Perfect for students studying parasitology or infectious diseases.
