Covers Dracunculus medinensis, the guinea worm, with its copepod intermediate host, life cycle and blister-driven emergence, then the filarial worms Wuchereria bancrofti, Loa loa and Onchocerca volvulus, each with its disease, vector, microfilarial periodicity and diagnosis. It closes with recap questions and four mnemonics, one for each parasite.
Topic 97 of 105 in the MU Sofia syllabus for Biology (Medicine, Year 1). The free AceMed note covers it in 7 sections, about 1,458 words (10 min of reading), with 21 flashcards.
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Dracunculus medinensis. Filarial worms: Wuchereria bancrofti, Loa loa, Onchocerca volvulus.
Dracunculus medinensis (Guinea Worm)
Wuchereria bancrofti
Loa loa (Eye Worm)
Onchocerca volvulus (River Blindness)
RECAP QUESTIONS
MNEMONICS
Dracunculus medinensis (Guinea Worm)
Disease Caused
Causes a parasitic infection known as dracunculiasis, commonly referred to as guinea worm disease
Geographic Distribution
Historically widespread
Now limited to remote, rural areas in specific African countries
Hosts
Humans are the primary definitive host
Dogs, cats, and some wild animals can also carry the worm
The intermediate host is a tiny aquatic crustacean known as Cyclops, which is a type of copepod
General Characteristics
Adult females can grow up to 70 to 120 centimeters in length
Males are much smaller, with the largest being about 4 centimeters long
Life Cycle and Transmission
Infection happens when a person drinks contaminated water containing copepods that are carrying larvae
People and animals can also become infected by eating aquatic animals that have ingested infected copepods
Inside the body, larvae penetrate the digestive wall and travel to the abdominal cavity
After mating, males die, and females migrate to the skin
Around one year after infection, the female worm creates a painful blister, most often on the lower limbs
When the blister is submerged in water, the worm emerges and releases larvae
The larvae are swallowed by copepods, where they mature over about two weeks
Symptoms and Effects
A painful blister is formed where the worm is about to exit
The worm slowly emerges from the skin and can take several days to be fully removed
The process is extremely painful and debilitating
Without clean care, the wound may become secondarily infected
Though rarely fatal, the disease often renders people unable to work or move normally for weeks
Prevention
There is no vaccine or medicine
Prevention relies on community-level education and water filtration
Filtering drinking water through a cloth has been highly effective in reducing cases
Filarial Worms (General Overview)
These are thread-like parasitic nematodes
They release microscopic larvae called microfilariae
Transmission occurs through biting insects, such as mosquitoes or flies
The adult worms live in human tissues like lymph vessels or subcutaneous layers
The intermediate hosts are always blood-feeding insects
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