Filarial Worms and Wuchereria Bancrofti

Study Notes

Filarial worms have complex life cycles, requiring an arthropod vector for transmission.
They inhabit lymphatic or subcutaneous tissues.
Female worms produce microfilariae, young worms.
Microfilariae develop into filariform larvae in the arthropod intermediate host.
Humans become infected through bites from infected arthropods.

Causes Wuchereriasis (filariasis), commonly called elephantiasis.
Named after the scientists Wucherer and Bancroft who greatly contributed to the study of the disease.
Parasite of the lymph nodes/lymphatic vessels.
Transmitted by mosquito bites.
Over 100 million people are believed to be infected.
Microfilariae are present in peripheral blood mainly at night (10 PM-2 AM).
The biological reason for this nocturnal periodicity is not fully understood.

Filarial worms are long, hair-like, transparent, thread-like.
Their cuticles are smooth, and their ends taper.
Males and females have distinct sexual differences in size (female larger).
Female worms have a pointed posterior end with an anus; males have genital papillae and two copulatory spicules.
Males and females tend to coil together in lymphatic areas.
The head end is slightly enlarged.

Filariform larvae enter the body through arthropod bites (typically mosquitoes).
The larvae multiply and mature into adult worms in lymphatic tissues, usually lower limbs.
Microfilariae enter the blood during the night (due to vector's biting habits).
Presence of adult worms causes lymphatic blockage and lymphedema (elephantiasis).
Adult worms obstruct lymphatic vessels in the lower limbs and external genitalia, causing those areas to swell and thicken the skin.

W. bancrofti infection is common in sub-Saharan Africa, Southeast Asia, the Pacific islands, and some areas of Latin America.
Other filarial worms (e.g., B. malayi, B. timori) have different geographic distributions.

The microfilariae look like transparent, slender bodies with blunt anterior ends and pointed tails.
They are highly active (can move forward and backwards).
About 250-300 μm long and 6-10 μm thick (microscopic).
Typically found within a sheath which is longer than the embryo
Their life span in the human body is probably about 70 days.

Causes loiasis, also known as African eye worm disease.
Found in West and Central Africa.
Transmitted by deerflies of the Chrysops genus.
Adults reside in subcutaneous tissue, microfilariae are found in the blood.
Periods of increased microfilariae in blood coincide with the feeding patterns of the deerfly vector.

Diagnosis methods using blood smears to identify microfilariae.
Treatments include DEC, ivermectin, and surgical removal or other antiparasitic drugs.
Preventative measures include vector control (mosquitoes, flies, black flies), treating infected populations, and implementing public health measures to control exposure to contaminated water supplies.