Helminths

Dracunculus medinensis

Taxonomy
Common names- Guinea Worm, Medina Worm, Serpent Worm, Dragon Worm

History

Known as a parasite of humans since about 1530 B.C. Guinea worm is thought to be the "fiery serpent" referred to in the Bible. The symbol of a Physician is the "Caduceus". The serpents are believed to represent the Guinea worm. Persian physicians removing the D. medinensis parasite from patient during the 9th century-

Hosts

Definitive: Humans Intermediate: Copepod

Distribution

Except for a few remote villages in the Rajastan desert of India and in Yemen, Guinea worm disease now occurs only in Africa. Infected areas in Africa lie in a band between the Sahara and the equator. Presently, only 9 countries are endemic: Sudan, Ghana, Nigeria, Mali, Togo, Burkina Faso, Ethiopia, Niger, and Ivory Coast. >50% of all cases of Guinea worm disease are reported from southern Sudan.

Morphology

A: Adult D. medinensis worms. (A) The adult female guinea worm is a long, slender worm ranging from 30 to 120 cm in length and from 0.09 to 0.17 cm in width. B: Three mature guinea worms. Note the tiny size of the mature male (mm) compared with the mature female (mf) and especially the markedly elongated and serpiginous, gravid female worm (gf). The gravid female shows an extruded uterus (eu)


Characteristics
usually occurs during drought Everyone is forced to drink from the same stagnant water supplies or pay for well.Three conditions to be met before D. medinensis can complete it’s life cycle.The skin of an infected individual must come in contact with waterThe water must contain the appropriate species of microcrustaceanThe water must be used for drinkingBelieved the parasites feed on blood due to the gut often being filled with dark brown gut material

Life Cycle

Life Cycle

Epidemiology

Dracunculiasis may result in three major disease conditions Emergent adult worms Secondary bacterial infection Nonemergent worms When worms do not emerge they degenerate and release antigens causing fluid filled abscesses or allergenic reactions. If the worms become calcified they can cause inflammation or if they remain in a joint, arthritis. Can cause paraplegia if it worm gets into the central nervous system.

Pathology

None until the female worms cause an allergic reaction by releasing metabolic wastes into host. This occurs at the onset of migration to the skin. a rash accompanied by severe itching nausea vomiting diarrhea dizziness edema Reddish papule-blister (local itching and intense burning). Blister ruptures, becomes abscessed-very painful. Secondary bacterial infections of opening possible. Retreating worm can draw bacteria under skin as well. There may be later symptoms fibrosis of the skin, muscles, tendons and joints (may interfere with locomotion or use of limbs)
Blister
Ruptured Blister

Pathology

Adult in joint  Calcified lesion in soft tissues 

Diagnosis

Diagnosis is made from the local blister, worm or larvae. The outline of the worm under the skin. Some people claim to be able to feel the worm moving towards the surface of the skin. Finding Calcified worms.

Treatment

Drug Therapy—MetronidazoleTo help prevent bacterial infectionsAnti-inflammatory to help reduce swellingTreatment includes the extraction of the adult guinea worm by rolling it a few centimeters per dayUsually takes weeks or months depending on how long the worm is.Exposing area to cold water helps remove worm faster. Preferably by multiple surgical incisions under local anesthesia.Infection does not make a person immune

Control

Filter, boil, or treat water with chlorine to kill intermediate host. Finely-meshed cloth or, better still, a filter made from a 0.15 mm nylon mesh, is all that is needed to filter out the copepods from the drinking water.Avoid bathing or wading in drinking water. Village-based volunteers demonstrating the use of cloth filter on a clay pot to filter drinking water     

Loa Loa

Morphology
Usually found in Africa and India Has a simple body with a head and neck Males are about 20-34 mm long Females are about 20-70 mm long

para-lab by l. wafa menawi

* Loa loa Adult worms move under human skinObserved beneath skin or passing through conjunctiva of eyes (‘eye worms’)Transmitted by horse flies in genus ChrysopsDisease endemic to rain forest regions of West & Central Africa and indiaGenerally mild & painless (chronic) with 10-15 year incubation periodMay cause swellings of skin (Calabar swelling) Microfilariae in human blood

Life cycle

A vector fly bites an infected human host and ingests microfilariase. Microfilariae move to the thoracic muscles of the insect host. Microfilariae develop into first stage larvae, then third stage larvae. Third stage larvae (infective) travel to the proboscis of fly. An infected vector fly bites an uninfected human host and the third stage larvae penetrates the skin and enters human subcutaneous tissue. Larvae mature into adults, who produce microfilariae that have been found in spinal fluid, urine, peripheral blood, and lungs.

para-lab by l. wafa menawi

*

Disease

Loa Loa infect human host by migrating through subcutaneous tissue such as back, chest, groin, scalp and eye. The parasite causes infection wherever they travel, and if they stay local, the host will suffer from local infection known as Calabar Swellings

para-lab by l. wafa menawi

* The standard method for diagnosing active infection is the identification of microfilariae by microscopic examination However, microfilariae circulate nocturnally, making blood collection an issue

The standard method for diagnosing active infection is the identification of microfilariae by microscopic examination However, microfilariae circulate nocturnally, making blood collection an issue Presence of worm in eye Skin swelling (nodules)

para-lab by l. wafa menawi

* A “card test” for parasite antigens requiring only a small amount of blood has been developedDoes not require laboratory equipmentBlood drawn by finger stickUrinalysis, CBC and Comprehensive Chemistries Foot Biopsy: Normal Skin with areas of chronic inflammation

para-lab by l. wafa menawi

* Treatment of filariasis involves two components: Getting rid of the microfilariae in people's blood Maintaining careful hygiene in infected persons to reduce the incidence and severity of secondary (e.g., bacterial) infections. Surgical removal of the worm


* Anti-filariasis medicines commonly used include: Diethylcarbamazine (DEC) reduces microfilariae concentrations kills adult worms Albendazole kills adult worms