Loa-Loa in Microbiology & Parasitology

Loa-Loa in Microbiology & Parasitology

1. Loa-Loa Apalin , Ruth Rendell D. BSN 2A1-3

2. Loa-Loa  the filarial nematode (roundworm) species that causes Loa loa filariasis . It is commonly known as the  "eye worm" . Its geographic distribution includes Africa and India

3. L. loa  is one of three parasitic filarial nematodes that cause subcutaneous filariasis in humans. The two other filarial nematodes are Mansonella streptocerca and  Onchocerca volvulus  (causes river blindness).

4. Maturing larvae and adults of the "eye worm" occupy the subcutaneous layer of the skin – the fat layer – of humans, causing disease.

5. Morphology Loa loa worms have a simple body including a head, body, and tail. Males range from 20mm to 34mm long and 350μm to 430μm wide. Females range from 20mm to 70mm long and are about 425mm wide

6. 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 .

7. Microfilariae develop into first stage larvae, second stage, 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.

8. Larvae mature into adults, who produce microfilariae that have been found in spinal fluid, urine, peripheral blood, and lungs

9. Loa loa filariasis

10. Loa Loa Filiriasis a skin and eye disease caused by the nematode worm ,  loa loa . Humans contract this disease through the bite of a Deer fly or Mango fly ( Chrysops   spp ), the vectors for  Loa loa . 

11. Signs and symptoms The common symptoms include itching and non-painful swelling around the joints . These are called Calabar swellings . These are caused by migration of the worm under the skin. Also, the worm is visible when this migration occurs under the surface of the eye and so the name "Eye Worm".

12. Signs and symptoms There is redness, pain and itching in the eye but does not result in any long term symptoms. The patients may also experience hives, itching, muscle pain and fatigue. Sometimes, it can cause swollen glands and fluid collection around the lungs .

13. Transmission Loa loa  infective larvae (L3) are transmitted to humans by deer fly vectors,  Chrysops silica  and  C. dimidiata . The vectors are blood-sucking and day-biting, and they are found in rainforest-like environments in west and central Africa.

14. Infective larvae (L3) mature to adults (L5) in the subcutaneous tissues of the human host, after which the adult worms—assuming presence of a male and female worm—mate and produce microfilaria. The cycle of infection continues when a non-infected mango or deer fly takes a blood meal from a microfilaremic human host, and this stage of the transmission is possible due to the combination of the diurnal periodicity of microfilaria and the day-biting tendencies of the Chrysops spp .

15. Reservoir Humans are the primary reservoir for  Loa loa . Other minor potential reservoirs have been indicated in various fly biting habit studies: hippopotamus, wild ruminants (e.g., buffalo), rodents, and lizards

16. Diagnosis Identification of microfilariae by microscopic examination is a practical diagnostic procedure. Examination of blood samples will allow identification of microfilariae of Loa loa . It is important to time the blood collection with the known periodicity of the microfilariae. The blood sample can be a thick smear, stained with Giemsa or haematoxylin and eosin

17. Prevention Diethylcarbamazine has been shown as an effective prophylaxis for Loa loa infection No vaccine has been developed for loiasis and there is little report on this possibility.

18. Treatment Treatment of loiasis involves chemotherapy or, in some cases, surgical removal of adult worms followed by systemic treatment.

19. The current drug of choice for therapy is diethylcarbamazine  (DEC) , though ivermectin use is not unwarranted. The recommend dosage of DEC is 6 mg/kg/d taken three times daily for 12 days. The pediatric dose is the same. DEC is effective against microfilariae and somewhat effective against macrofilariae (adult worms)