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LOA LOA (PATHOGEN – TISSUE NEMATODE) -TANGA MANJULATHA

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Loa loa, the African eye worm, was first noted in the eye of a Negro girl in the West Indies in 1770. In 1895, Argyll‑Robertson described the adult worms that he extracted from the eye of a woman who had resided at Old Calabar in West Africa. The adult worms migrate through the subcutaneous tissues, producing intermittent "Calabar swellings," in addition to migrating beneath the conjunctiva. parasitology loa-loa pathogen tissue nematode.Loa loa is a blood dwelling nematode thatis parasitic in humans. The adult wormwanders through the subcutaneous tissue but is most obvious as it crosses theconjunctiva of the eye hence leading toits common name, the African eye worm. Common Name: Eye WormScientific Name: Loa Loa

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LOA LOA (PATHOGEN –

TISSUE NEMATODE)

-TANGA MANJULATHA

• INTRODUCTION:Loa loa, the African eye worm, was first noted in the eye of a Negro girl in the West Indies in 1770. In 1895, Argyll‑Robertson described the adult worms that he extracted from the eye of a woman who had resided at Old Calabar in West Africa. The adult worms migrate through the subcutaneous tissues, producing intermittent "Calabar swellings," in addition to migrating beneath the conjunctiva.  Approximately 13 million people are infected with L. loa in Central and West Africa.  The vectors are biting flies (Chrysops) (mango or deerflies) and are known as red flies in Africa.

Kingdom: Animalia

Phylum: Nematoda

Class: Chromadorea

Order: Spirurida

Superfamily: Filarioidea

Family: Onchocercidae

Genus: LoaSpecies: L. loa

classification

•Epidemiology:

Loiasis is endemic to the Central and West African rain forests and may infect as many as 13 million people. Disease distribution depends on the vectors, which breed in wet mud at the side of streams under the rain forest canopy. Flies appear to be attracted by the movement of people or vehicles, as well as rising smoke. An excellent example of vector host interactive sites would ‑include rubber plantations with a dense high canopy and human workers. The Chrysops flies are more common in the rainy season, and exposure differences result in higher infection rates in adults rather than children.

•MORPHOLOGY:• Adult: The females measure 50 to 70 by 0.5 mm,

while the males measure 30 to 35 by 0.3 to 0.4 mm.•Microfilariae: The microfilariae frequently are

not detected in the blood until years after the adult worms are noted. The microfilariae have a diurnal periodicity whose peak occurs about midday; the remainder of the time they can be found in pulmonary capillaries. The microfilariae are sheathed and are 250 to 300 μm long. When stained, the body nuclei are continuous to the tip of the tail.

•Life Cycle:Three species involved in the life cycle include the parasite Loa loa, the fly vector, and the human host:• A vector fly bites an infected human host and ingests microfilariae.•Microfilariae move to the fat body 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.

vector

1. Infective Stage:. Third stage larvae2. Vector: the bite of a Deer fly or Mango fly (Chrysops spp), 3.Definitive Host: Human4. Intermediate Host: The American deer fly, Chysops atlanticus

5. Reservoir Host: Dog, monkey.

7.Diagnosis Stage: microfilaria in spinal fluid.

NOTES  

Symptoms and Signs:The Chrysops bite results in erythema,

swelling, and itching, symptoms which can worsen with the presence of infective larvae. 

Many patients with active L. loa infections do not have a microfilaremia.

The most common pathologic sequelae associated with L. loa infections are Calabar or fugitive swellings (angioedema). 

Serious complications due to loiasis have included cardiomyopathy, encephalopathy, nephropathy, and pleural effusions.

Calabar swellings

Diagnosis:• The main methods of diagnosis include

the presence of microfilariae in the blood, the presence of a worm in the eye, and the presence of skin swellings. Surgical removal of the worm can easily be performed.

Treatment:The common treatment for the disease is a use of one of two drugs:

1. diethylcarbamazine (DEC)

2. ivermectin

PREVENTION:Although vector control is one means of prevention,Clearing of growth around houses and use of screens

and protective clothing have all been helpful.   In general, control of loiasis also depends to a great

degree on chemoprophylaxis with DEC.  Although other therapeutic approaches have been

tried, including mebendazole and ivermectin, problems remain with both options.

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