Loa Loa Nemathelminth Parasite

• Two Nemathelminth parasites include Loa loa and Onchocerca volvulus.

Loa loa

• Also called the African eye worm because it is endemic in Western Africa.
• Humans are the definitive host.
• The vector and intermediate host is the day-biting deer fly (Chrysops species).
• Transmitted through the bite of an infected Chrysops fly.
• Causes loiasis, also known as Loa loa filariasis

Clinical Symptoms of Loa Loa

• Calabar or migratory swellings
• Ocular lesions caused by the movement of adult worms in the eye.

Loa Loa Diagnosis

• Observing microfilarial larvae in peripheral blood
• Isolation of the adult worm from the eye.

Loa Loa Treatment

• Diethylcarbamazine (DEC) effectively treats loiasis.

Loa Loa Life Cycle

• An infected Chrysops fly introduces filarial larvae onto the skin during a blood meal.
• Larvae penetrate the bite wound and migrate into subcutaneous tissues, developing into adult worms.
• Adult females measure 40–70 mm long (0.5 mm in diameter)
• Males measure 30–34 mm long (0.35–0.43 mm in diameter).
• Adult worms produce microfilariae (250–300 µm long, 6–8 µm wide).
• Microfilariae circulate in peripheral blood during the day and migrate to the lungs at night.
• A fly ingests microfilariae during a blood meal.
• Microfilariae migrate from the midgut to the hemocoel and develop into infective third-stage larvae in the thoracic muscles.
• Third-stage larvae migrate to the fly’s proboscis and can infect another human during the next blood meal.

Onchocerca Volvulus

• Also called Blinding filaria.
• Humans are the definitive host.
• Day-biting black flies (Simulium species) are the vector and intermediate host, breeding in fast-flowing rivers.
• Black flies from the genus simulium are the vectors for lower lower filariasis.
• Transmitted by the bite of an infected Simulium fly.
• Causes onchocerciasis, or river blindness

Onchocerca Volvulus Treatment

• Ivermectin kills microfilariae.
• Suramin kills adult worms but is highly toxic.

Onchocerca Volvulus Life Cycle

• During a blood meal, an infected black fly introduces infective filarial larvae onto human skin.
• Larvae penetrate the bite wound and develop into adult filariae in subcutaneous connective tissue nodules.
• Adult worms can live for 10–15 years
• Nodules may contain multiple worms.
• Female worms continuously produce microfilariae for approximately 10-15 years.
• Microfilariae live for 12–15 months and migrate through skin and lymphatic tissues rather than circulating in peripheral blood.
• A black fly ingests microfilariae during a blood meal.
• Inside the fly, microfilariae migrate from the midgut to the hemocoel and develop into infective third-stage larvae in the thoracic muscles.
• These larvae migrate to the fly’s proboscis, allowing transmission to a new human host.

Clinical symptoms of Onchocerca Volvulus

• Subcutaneous nodules, or onchocercoma
• Ocular manifestations
• Can cause blindness

Diagnosing Onchocerca Volvulus

• Observing microfilariae in aspirated material of skin nodule
• Observing microfilariae larvae in conjunctival biopsies