Onchocerciasis Quiz

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Questions and Answers

What is the main vector responsible for the transmission of Onchocerciasis?

Female black flies of the genus Simulium (correct)

Culex mosquitoes

Male black flies of the genus Simulium

Female Aedes mosquitoes

What is one significant change in the environment affecting the distribution of the vector for Onchocerciasis?

Deforestation in Africa (correct)

Increased rainfall in desert areas

Pollution in rivers

Increased urbanization near rivers

How long can the Onchocerca volvulus worm live in the human body?

Up to 5 years

Up to 15 years (correct)

Up to 10 years

Up to 20 years

Which of the following is NOT a symptom associated with the death of microfilariae in Onchocerciasis?

Nasal congestion (C) Signup and view all the answers

In which continent is Onchocerciasis primarily considered endemic?

Africa (A) Signup and view all the answers

What appearance does skin affected by Onchocerciasis often take on?

Leopard skin appearance (C) Signup and view all the answers

What is the estimated global number of individuals infected with Onchocerciasis?

18 million (D) Signup and view all the answers

What is the primary method of controlling Onchocerciasis in endemic areas?

Community-based ivermectin administration (C) Signup and view all the answers

What is the primary cause of visual disturbances and blindness linked to O. volvulus infection?

Microfilariae invasion in the eye (C) Signup and view all the answers

What is the lifespan of microfilariae found in the body of an infected host?

1-2 years (C) Signup and view all the answers

What is the role of female black flies of the genus Simulium in the transmission of O. volvulus?

They transmit microfilariae through bites (A) Signup and view all the answers

How long after exposure to Simulium bites can a person still transmit the disease?

10-15 years (C) Signup and view all the answers

Which diagnostic method is used to observe microfilariae in the skin?

Skin snips (A) Signup and view all the answers

What is the incubation period before microfilariae are typically found in the skin following an infective bite?

1 year or more (C) Signup and view all the answers

What impact does infection with O. volvulus have on the host's immune system?

It reduces immunity and resistance to other diseases (A) Signup and view all the answers

What activity is primarily responsible for the spread of Onchocerciasis?

Daytime feeding of infected female black flies (D) Signup and view all the answers

What is the main advantage of the 5-DEC Patch Test over other diagnostic methods for onchocerciasis?

It poses a lower risk of systemic reactions. (D) Signup and view all the answers

What is the primary goal of the Onchocerciasis Control Program (OCP)?

To eliminate onchocerciasis as a public health problem. (A) Signup and view all the answers

Which drug is currently the only microfilaricide used as the primary treatment for onchocerciasis?

Ivermectin (D) Signup and view all the answers

What is a significant risk associated with the diagnostic method used for onchocerciasis?

It may provoke severe systemic reactions. (A) Signup and view all the answers

What is one of the side effects of Suramin that requires a test dose?

It has potential toxic effects. (B) Signup and view all the answers

Which method is NOT effective in eliminating transmission of onchocerciasis?

Aerial application of larvicide using helicopters. (B) Signup and view all the answers

What treatment can be added to Ivermectin to lower microfilarial loads in hosts?

Doxycycline (B) Signup and view all the answers

What precaution can individuals in endemic areas take to avoid black fly bites?

Use insect netting. (C) Signup and view all the answers

What is a common factor associated with the transmission of Lymphatic Filariasis?

Poor sanitation and urbanization (C) Signup and view all the answers

Which mosquito species is primarily responsible for the transmission of Wuchereria bancrofti?

Culex mosquito (C) Signup and view all the answers

Which of the following is NOT a disease manifestation associated with Lymphatic Filariasis?

Blindness (B) Signup and view all the answers

What is the typical age range most affected by Lymphatic Filariasis?

6 months to 20-30 years (B) Signup and view all the answers

Which of the following statements about immunity to Lymphatic Filariasis is true?

Immunity can develop after long years of exposure. (B) Signup and view all the answers

What is the primary life cycle stage of Lymphatic Filariasis found in human peripheral blood?

Microfilariae (B) Signup and view all the answers

Which factor is critical for the breeding of the mosquito vector in Lymphatic Filariasis?

Optimum temperature between 20-30°C (A) Signup and view all the answers

Which of the following correctly identifies a vector for Onchocerciasis?

Simulium flies (B) Signup and view all the answers

What is the duration of the clinical incubation period for Lymphatic Filariasis?

8-16 months (A) Signup and view all the answers

Which stage in Lymphatic Filariasis follows the asymptomatic microfilariaemic stage?

Stage of Acute manifestation (B) Signup and view all the answers

What condition is NOT a chronic manifestation associated with Lymphatic Filariasis?

Filarial fever (A) Signup and view all the answers

Which stage is characterized by the absence of microfilariae despite possible exposure to infective larvae?

Asymptomatic amicrofilaraemic stage (B) Signup and view all the answers

What is a primary characteristic of the Stage of Acute manifestation in Lymphatic Filariasis?

Recurrent episodes of inflammation (B) Signup and view all the answers

Which of the following clinical features is associated with chronic manifestations of Lymphatic Filariasis?

Pitting edema (C) Signup and view all the answers

Which term describes the stage with a considerable proportion of asymptomatic individuals despite having circulating microfilariae?

Asymptomatic microfilariaemic stage (A) Signup and view all the answers

What is a common long-term consequence of the chronic (obstructive) lesions caused by Lymphatic Filariasis?

Scrotal elephantiasis (C) Signup and view all the answers

What is a characteristic clinical manifestation of occult filariasis?

Absence of microfilariae (C) Signup and view all the answers

What type of cough is typically associated with occult filariasis?

Paroxysmal cough (B) Signup and view all the answers

Which stage of lymphoedema is characterized by swelling that reverses at night?

Stage I (C) Signup and view all the answers

Which method is considered the ‘Gold Standard’ for diagnosing Wuchereria bancrofti infection?

Immuno Chromatographic Test (A) Signup and view all the answers

What finding is expected on an X-ray in a patient with occult filariasis?

Diffused nodular mottling (A) Signup and view all the answers

In which stage of lymphoedema do skin folds become shallow and nodules may appear?

Stage IV (C) Signup and view all the answers

What is the typical laboratory method used to demonstrate microfilarae in peripheral blood?

Thick blood smear (A) Signup and view all the answers

What is the main symptom related to eosinophilia in occult filariasis?

Adenopathy (A) Signup and view all the answers

Study Notes

Onchocerciasis (River Blindness)

Onchocerciasis is a chronic parasitic disease caused by the filarial worm, Onchocerca volvulus.
It's the leading cause of blindness worldwide.
Transmission occurs through the bites of infected female blackflies of the genus Simulium.
Larvae mature to adult worms in subcutaneous tissue, forming subcutaneous nodules.
Onchocerca volvulus can survive in the human body for up to 15 years.

Epidemiology

Onchocerciasis is endemic in 36 countries across Africa and Latin America.
Countries like Brazil, Colombia, Ecuador, Mexico, Venezuela, and Guatemala have been successfully eliminated through community-based ivermectin administration programs.
The disease is also known as River Blindness due to its high prevalence near rivers with rapid flow.
Well-oxygenated water is crucial for the development of the Simulium blackfly, the disease vector.
The obligatory aquatic stage of the blackfly lasts approximately 10 days.
Adult flies of some species remain localized, while others migrate over long distances.
Deforestation is altering ecosystems and potentially changing blackfly distribution patterns.
Rural agricultural areas in Sub-Saharan Africa are predominantly affected.
Globally, an estimated 18 million people are infected, and 270,000 are blinded by onchocerciasis.

Clinical Picture

Female worms release microfilariae that migrate through the skin, often causing an intense itching rash when they die.
Chronic dermatitis, altered pigmentation, edema, atrophy, loss of skin elasticity, and lymphadenitis can result.
Pigment changes, especially in lower limbs, result in a condition known as "leopard skin".
The worms spread throughout the body. When they die, they trigger a variety of conditions, including intense itching and a strong immune response that can destroy nearby tissue, leading to skin depigmentation.
Onchocerciasis is the world's second leading infectious cause of blindness.
Microfilariae frequently reach the eye, leading to visual disturbance and blindness.
Microfilariae are also found in blood, tears, sputum, and urine in severe infections.

Life Cycle

The adult Onchocerca volvulus parasite releases microfilariae into the bloodstream.
The microfilariae are taken up by female blackflies during a blood meal.
In the blackfly's midgut, L3 larvae develop.
The blackfly bites a new host, releasing the L3 larvae into the bloodstream.
The larvae migrate to subcutaneous tissues where they mature into adult worms.
Microfilariae are ingested by a blackfly during a blood meal. They develop into infective larvae in the blackfly's thorax.
The infective larvae are released into the human bloodstream, starting another round of the cycle.

Prevention & Control

The WHO's Onchocerciasis Control Programme aims to eradicate the disease by eliminating the parasite reservoir.
Larvicides may be applied to rivers and breeding habitats of the black fly using helicopters, but this vector control is limited.
To reduce infection, people should avoid bites by using protective measures. Insecticides, protective clothing (long sleeves and pants), and insect nets are recommended in affected areas.
Ivermectin is available as a mass drug treatment, and a single dose can prevent further transmission for several months.

Lymphatic Filariasis

Lymphatic filariasis is caused by three closely related nematodes: Wuchereria bancrofti, Brugia malayi, and Brugia timori.
These parasites are transmitted by mosquito bites.
The worms reside in lymph vessels; microfilariae circulate in the blood during the night.
Lymphatic filariasis causes significant suffering and disability.
- The disease range from no symptoms to a variety of conditions, including acute-filarial fever, chronic lymphangitis, lymphadenitis, elephantiasis of genitals/legs/arms, tropical pulmonary eosinophilia, filarial arthritis, epididimoorchitis, chyluria, and others.
- The disease manifests differently across individuals.

Diagnosis

Palpating subcutaneous nodules, examining skin biopsies (skin snips), and examining eyes for free-floating intraocular microfilariae are some diagnostic methods.
The DEC provocative test is also used.
Standard methods are used to detect microfilariae in blood samples, such as thick blood smears.
Specialized laboratory techniques include membrane filtration, and immuno-chromatographic tests to detect filarial antigens.

Treatment

Ivermectin is the primary treatment for onchocerciasis.
Ivermectin kills microfilariae reliably and prevents reinfection for a time.
Other drugs like doxycycline and suramin are sometimes used. Suramin targets only adult worms and has largely been replaced by Ivermectin in treatment regimens.
The choice of drug and dosage will be dependent on specific considerations.

Prevention and Control

Mass drug administration with ivermectin is crucial in endemic regions.
Maintaining vector control through environmental measures is necessary to diminish blackfly populations.

Control Programs

The WHO's Onchocerciasis Control Programme focuses on eliminating the parasite reservoir to address onchocerciasis as a public health issue.

Other Important Information

The prevalence of onchocerciasis and lymphatic filariasis are concentrated in particular geographic areas, and factors such as climate, socioeconomic status, and sanitation contribute to their distribution and transmission patterns.

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Description

Test your knowledge on Onchocerciasis, also known as river blindness. This quiz covers key aspects including the vector responsible for transmission, symptoms, and control methods. Dive into the details of this significant public health issue affecting numerous individuals globally.