loa loa pptx.pptx africa eye worm loiasis

Loa loa

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

2. Learning o b jectives At the end of this a s s ignment the students will be able to: Define l o a l o a Describe the general epidemiological aspects of l o a l o a Discuss the characteristics of l o a l o a Explain the life cycle of l o a l o a Apply the necessary laboratory procedures for the detection and identification of l o a l o a

3. O u t l i n e Introduction Morphology Vector/Transmission Epidemiology Life cycle Clinical f e a t u r e Diagnosis Treatment Prevention

4. 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.

5. 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

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

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

8. 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

9. 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)

10. 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

11. P a t h o g e n e s i s 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.

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

13. 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.

14. 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.

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

16. 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.

17. 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

18. 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

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