Podcast
Questions and Answers
What is the primary reason Suramin is not the first-line treatment for Onchocerca volvulus infections, despite its efficacy against adult worms?
What is the primary reason Suramin is not the first-line treatment for Onchocerca volvulus infections, despite its efficacy against adult worms?
- Suramin requires a longer treatment duration compared to Ivermectin.
- Suramin exhibits high toxicity, limiting its clinical use despite its efficacy. (correct)
- Suramin is only effective against microfilariae and does not affect adult worms.
- Suramin's mechanism of action is not fully understood, leading to unpredictable outcomes.
Considering the lifecycle of Loa loa, what specific adaptation allows microfilariae to maximize their chances of being ingested by the Chrysops vector?
Considering the lifecycle of Loa loa, what specific adaptation allows microfilariae to maximize their chances of being ingested by the Chrysops vector?
- Microfilariae secrete a chemoattractant that attracts Chrysops flies to the host.
- Microfilariae migrate to the peripheral blood during the day, coinciding with the Chrysops fly's feeding habits. (correct)
- Microfilariae exhibit positive phototaxis, congregating near the skin surface during the day.
- Microfilariae possess a protective coating that allows them to survive in the Chrysops fly's midgut.
If a patient is diagnosed with both loiasis and onchocerciasis, what critical factor must be considered before administering diethylcarbamazine (DEC)?
If a patient is diagnosed with both loiasis and onchocerciasis, what critical factor must be considered before administering diethylcarbamazine (DEC)?
- The patient's liver function, as DEC is hepatotoxic and can exacerbate liver damage.
- The patient's age, as DEC is contraindicated in children under 5 years old.
- The microfilarial load of Onchocerca volvulus, as DEC can cause severe reactions in patients with high levels triggering an inflammatory response known as the Mazzotti reaction. (correct)
- The presence of Calabar swellings, as DEC can worsen these symptoms due to increased immune response.
In areas co-endemic for both Loa loa and Onchocerca volvulus, what is the most significant challenge in implementing mass drug administration (MDA) programs for filarial diseases?
In areas co-endemic for both Loa loa and Onchocerca volvulus, what is the most significant challenge in implementing mass drug administration (MDA) programs for filarial diseases?
How does the migration pattern of Onchocerca volvulus microfilariae differ significantly from that of Loa loa, influencing the diagnosis and clinical presentation of the respective diseases?
How does the migration pattern of Onchocerca volvulus microfilariae differ significantly from that of Loa loa, influencing the diagnosis and clinical presentation of the respective diseases?
Given that adult Onchocerca volvulus worms can survive for 10-15 years within subcutaneous nodules, what is the most effective long-term strategy for managing the disease in highly endemic regions?
Given that adult Onchocerca volvulus worms can survive for 10-15 years within subcutaneous nodules, what is the most effective long-term strategy for managing the disease in highly endemic regions?
What is the most likely outcome if a traveler to West Africa, who has never been exposed to Loa loa, is bitten by an infected Chrysops fly and subsequently develops loiasis?
What is the most likely outcome if a traveler to West Africa, who has never been exposed to Loa loa, is bitten by an infected Chrysops fly and subsequently develops loiasis?
Why is the diagnosis of Onchocerca volvulus typically performed via skin snips rather than blood samples?
Why is the diagnosis of Onchocerca volvulus typically performed via skin snips rather than blood samples?
How does Ivermectin's mechanism of action contribute to the control of onchocerciasis, and what are the implications for its long-term use in endemic regions?
How does Ivermectin's mechanism of action contribute to the control of onchocerciasis, and what are the implications for its long-term use in endemic regions?
What is the most significant challenge in developing a vaccine against Onchocerca volvulus?
What is the most significant challenge in developing a vaccine against Onchocerca volvulus?
Flashcards
Loa loa
Loa loa
A nematode found in Western Africa, transmitted by the day-biting deer fly (Chrysops species).
Calabar swellings
Calabar swellings
Migratory swellings associated with Loa loa infection.
Ocular lesions (Loa loa)
Ocular lesions (Loa loa)
Visual impairment caused by the movement of adult Loa loa worms in the eye.
Diethylcarbamazine (DEC)
Diethylcarbamazine (DEC)
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Onchocerca volvulus
Onchocerca volvulus
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Ivermectin
Ivermectin
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Suramin
Suramin
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Study Notes
- Nematodes are parasites
Loa Loa
- Also called the African eye worm
- Endemic in Western Africa
- Humans are the definitive host
- The vector is the day-biting deer fly (Chrysops species)
- Transmitted through the bite of an infected Chrysops fly
Clinical Symptoms: Loiasis (Loa loa filariasis)
- Calabar swellings (migratory swellings) occur
- Ocular lesions are caused by the movement of adult worms in the eye
Diagnosis
- Microfilarial larvae observed in peripheral blood indicates infection
- Isolation of the adult worm from the eye can confirm infection
Treatment
- Diethylcarbamazine (DEC) is an effective treatment
Loa Loa Life Cycle
- An infected Chrysops fly introduces filarial larvae onto the skin during a blood meal
- Larvae penetrate the bite wound, migrate into subcutaneous tissues, and develop into adult worms
- Adult females measure 40–70 mm long and 0.5 mm in diameter
- Males measure 30–34 mm long and 0.35–0.43 mm in diameter
- Adult worms produce microfilariae that circulate in peripheral blood during the day and migrate to the lungs at night
- Microfilariae measure 250–300 µm long and 6–8 µm wide
- A fly ingests microfilariae during a blood meal
- Microfilariae migrate from the midgut to the hemocoel inside the fly
- They develop into infective third-stage larvae in the thoracic muscles
- Larvae migrate to the fly’s proboscis and can infect another human during the next blood meal
Onchocerca Volvulus
- Also called blinding filaria
- Humans are the definitive host
- Transmitted by the bite of an infected Simulium fly (day-biting black fly)
Treatment
- Ivermectin kills microfilariae
- Suramin kills adult worms (but is highly toxic)
Onchocerca Volvulus Life Cycle
- An infected black fly introduces infective filarial larvae onto human skin during a blood meal
- Larvae penetrate the bite wound and develop into adult filariae in subcutaneous connective tissue nodules
- Adult worms can live for 10–15 years
- Nodules can contain multiple worms
- Female worms continuously produce microfilariae that live for 12–15 months
- Microfilariae migrate through skin and lymphatic tissues rather than circulating in peripheral blood
- A black fly ingests microfilariae during a blood meal
- Microfilariae migrate from the midgut to the hemocoel inside the fly
- They develop into infective third-stage larvae in the thoracic muscles
- Larvae migrate to the fly’s proboscis, allowing transmission to a new human host
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