Loa loa

LOA LOA

(African Eye Worm)

ARISHA

IBRAHIM

ROLL NO: 105

3rd YEAR

MBBS

CONTENTS

Introduction History of discovery Morphology Vector/Transmission Epidemiology Life cycle Incubation period Clinical Presentation Diagnosis Treatment Prevention

INTRODUCTION

Loa Loa is a blood dwelling Nematode that is parasitic to human beings.

The adult worm wanders through the subcutaneous tissue but is most obvious as it crosses the conjunctiva of the eye leading to its common name,the African Eye Worm.

Like all round worms it has separate male & female sexes.

Infection with loa loa is called Loiasis.

HISTORY OF DISCOVERY

Loa loa was first

described in 1770 by

a French Surgen,

Mongin,when he

unsuccessfully tried

to excise a worm

from the eye of a

woman in Santa

Domingo.

MORPHOLOGY

Adults worm range in length from 2 to

3.5 cm for males & 5 to 7 cm for

females. Both are not more than 0.5

mm wide.

Contd..

Nuclei as show below ,are found in the

tip of the tail & form a continuous row

without large spacing b/w nuclei

Contd..

Microfliaria are sheathed in a

cuticle.The sheath, however, dose not

stain with Giemsa. Microfilaria have a

diurnal periodicity to their

concentration in the blood stream.

VECTOR/ TRNSMISSION

Humans are infected by the bite of

deer fly(mango fly), chrysops which

deposit infective larvae on the skin .

The larvae enter the bite wound,

wander in the body & develop into

adults .The females release

microfilariae.

EPIDEMIOLOGY

The disease is found only in topical

central & west Africa,the habitat of

the vectors Chrysops.

LIFE CYCLE

1) Mango fly bites human,takes blood meal.Larvae are deposited on skin which enter in the bite wound.

2) Larvae develop into adult worms & wander through subcutaneous tissue.

3) Female release sheathed eggs called Microfilariae travel to the spinal fluid, blood, urine, sputum & lungs.

4) Mango fly bites human, takes blood meal containing microfilariae.

5) Microfilariae shed their sheaths & migrate to thoracic muscle of the fly.

Contd..

6) Microfilariae develop into larvae.

7) Further larval development.Infective

10-12 days after ingestion.

8) Larvae migrates to the fly’s mouth.

LIFE CYCLE

INCUBATION PERIOD

Microfilariae appear in the blood years

after the presence of the adult worm is

evident.

Incubation period 1 year (most typical)

to 10 years.

CLINICAL PRESENTATION

“A Worm Just Crawled Across My Eye!”

Contd..

Calabar Swelling :

A local edema of the subcutaneous

tissue,are caused by an allergic

reaction to dead worms or the metabolic

products of the worms. The swellings

are usually several inches in diameter &

subsides aftera few days to weeks.

They can be tender & painful.They can

occur anywhere on the body but mostly

on forearms & wrists.

COMPLICATIONS

May arise if worm lodges into unusual sites.Scrotal swelling , bowel obstruction ,endocarditis, arthritis, retinopathy, & neuropathy have all been seen in persons infected with loaloa.

Loa lao often increases the number of eosinophils , the immune cell that fights parastic infections, in blood.

Loa loa dose not cause serious long term damage to humans.

DIAGNOSIS

Calabar swelling & the presence of a

worm in the conjunctiva are main

diagnostic methods.

Laboratory test for elevated

eosinophils & C-reactive proteins can

also be formed.

Diagnosis is also made by

visualization of the microfilariae in a

blood smear.But its not reliable

because microfilariae might take years

to appear in the blood.

TREATMENT

Diethylcarbamazine eliminates the microfilariae & may kill adults.

Worms in the eyes reqiuresurgical excision by paralizing the worm with few drops of cocaine (4%).

PREVENTION

Prevention includes

avoiding contact with

the vector by bug

repellant,wearing long

sleeved clothing, &

sleeping in screened

areas. There is no

other known animal

reservoir outside

humans.

REFERENCES

Review of Medical Microbiology and

Immunology by Warren Levinson

Net.

ACKNOWLEDGEMENTS

ALLAH ALMIGHTY

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