Loa loa

1. COLLEGE OF HEALTH SCIENCES
MEDICAL PARASITOLOGY FOR 2ND YEAR PUBLIC
HEALTH STUDENTS
Submit to:-Lencho Girma (MSc in Medical Microbiology)

3. Learning objectives
At the end of this assignment the students will be able to:
 Define loa loa
 Describe the general epidemiological aspects of loa loa
 Discuss the characteristics of loa loa
 Explain the life cycle of loa loa
 Apply the necessary laboratory procedures for the
detection and identification of loa loa

4. Outline
 Introduction
 Morphology
 Vector/Transmission
 Epidemiology
 Life cycle
 Clinical feature
 Diagnosis
 Treatment
 Prevention

5. 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.

6. Loiasis, called African eye worm by most people, is caused by the
parasitic worm Loa loa. It is passed on to humans through the
repeated bites of deerflies (also known as mango flies or mangrove
flies) of the genus Chrysops
Infection with the parasite can also cause repeated episodes of
itchy swellings of the body known as Calabar swellings

7. MORPHOLOGY
Morphological stages :
>Adult worm
>Microfilariae
>Infective stage larvae

8. ADULTWORM
> Thin ,transparent, whitish,
thread like worm
Anterior end tapers to a narrow head
>Surface of the body is covered with
small knobs

9. Male worm
> 30-34mm in length.
>0.35-0.43mm in diameter
>Tail end has spicules
unequal length
Female worm
>40-70mm in length
>0.5mm in diameter
>The vulva opens in the
cervical region

10. MICROFILARIA
> Sheathed with column of nuclei extending from tip of the tail
> 250-300um: length
> Stain : iron haematoxylin
> Diurnal periodicity : peripheral blood during day
time (12-2pm)

11. Epidemiology
 First detected in the eye of the patient in West Indies
in 1770
 Now limited in the forest of West and Central Africa
 Ten countries have areas where there are high rates of
infection
 29 million people who are at risk of getting loaisis in affected
areas of Central and West Africa

12. Pathogenesis
bitten by an infected deerfly of the genus Chrysops.
Deerflies become infected when they eat blood from an
infected person.
Travelers are more likely to become infected if they are in
areas where they are bitten by deerflies for many months,
though occasionally they get infected even if they are in the
area for less than 30 days.

14. Loiasis - Clinical Manifestations
• Asymptomatic
• Non-specific
- urticaria, pruritus, myalgias
• Calabar swellings
• Eyeworm
• Complications
- Endomyocardial fibrosis, renal disease,
encephalopathy, entrapment neuropathy

16. 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.

18. 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.

19. Contd.
6) Microfilariae develop into larvae.
7) Further larval development. Infective
10-12 days after ingestion.
8) Larvae migrates to the fly's mouth.

20. 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 loa
loa.
• 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.

21. Loiasis: Diagnosis
• Definintive diagnosis
- Detection of microfilariae in daytime blood
- ldentification of adult worm in the
subconjunctiva or subcutaneous tissue
- PCR using Loa loa repeat sequence
• Presumptive diagnosis
- Compatible clinical picture + positive
antifilarial antibodies
• Problematic due to geographical, serologic and
clinical overlap with other filarial infections

22. Loiasis: treatment
• Diethylcarbamazine (DEC)
- treatment of choice (8-10 mg/kgid x 21
days)
- mechanism of action unknown
• immune system dependent
macro- and microfilaricidal
- associated with severe side effects in
patients with high levels of circulating
microfilariae
> lvermectine or albendazole is effective in reducing filarial load
• Contraindicated in heavy microfilaremia
Surgical removal of adult worm is rarely done

24. PREVENTON
Mass chemotherapy
• DEC 5mg/kg for 3 days
• Kills microfilariae
Personal protection
• Insect repellent
• Protective clothing
• Avoid visit to endemic areas