Wuchereria bancrofti can be found in the subtropical and tropical areas of the world.These include Central Africa, the Nile Delta, India, Pakistan, Thailand, the Arabian Coast, the Philippines, Japan, Korea and China in the Eastern Hemisphere and Haiti, the Dominican Republic, Costa Rica and the Brazilian coast in the western hemisphere.Mosquito breeding takes place in these areas in contaminated water.It is interesting to note that the indigenous people of endemic areas are more vulnerable to Wuchereria bancrofti than non – indigenous individuals living in these areas.
Morphology of Wuchereria bancrofti
The average length of microfilaria is 240 to 300 μm.A delicate and thin sheath surrounds the body.There are numerous nuclei in the body.The cephalic or anterior end is circular and blunt.The posterior or tail end culminates in a point free of nuclei.This is an important feature that helps to differentiate it from other sheathed microfilariae.
The adult Wuchereria bancrofti worms are white and thread-like. The females are usually larger than the males, 40 to 100 mm and 20 to 40 mm respectively.
Life Cycle of Wuchereria bancrofti
The Culex, Aedes and Anopheles spp of mosquitoes serve as Wuchereria bancrofti ‘s intermediary hosts and vectors. The adult worms reside in the lymph system in the human host, where they lay their microfilariae. They live in the blood and in the lymphs.
Clinical symptoms of Wuchereria bancrofti
Adult patients who were most likely exposed to Wuchereria bancrofti as children may become infected and have no symptoms.Microfilariae are usually recovered from these patients in blood samples.In these samples, eosinophilia can also be noted.Physical examination only reveals enlarged lymph nodes, especially in the groin region of the inguinal area.This type of infection is self – limiting, as adult worms eventually die and there are no signs of microfilariae.A patient can undergo the whole process without even knowing it
Symptomatic Bancroftian Filariasis
A variety of symptoms can occur in patients infected with Wuchereria bancrofti.In general, they develop fever, chills and eosinophilia.The invasion of the parasite can lead to the formation of granulomatous lesions, lymphangitis and lymphadenopathy.There may also be bacterial infections with Streptococcus.Elephantiasis or swelling of the lower limbs, especially of the legs, develop due to a blockage of the lymphatic vessels.Genitals and breasts can also be affected.The death of adult worms can lead to calcification or the formation of abscesses.
Laboratory Diagnosis of Bancroftian Filariasis
An examination of a Giemsa-stained blood for Wuchereria bancrofti microfilariae is the laboratory diagnostic method of choice.A more sensitive method of obtaining microfilariae involves filtering heparinized blood through a special filter known as a nuclepore filter, and then staining and checking the filter contents.The Knott technique can also be used.Light infections can be diagnosed by immersing 1 ml of blood in 10 ml of a 2% formalin solution that lyses the red blood cells.Then a microscopic examination of the stained sediment is carried out.In all of these procedures, the optimal sample is taken at night because this organism generally exhibits nocturnal periodicity.Peak times for sampling are between 21:00 and 4:00 in the morning which correlates with the appearance of its vector, the mosquito.However, subperiodic organisms are sometimes discovered throughout the day.They are more prevalent in the late afternoon.Serological tests, including antigen and antibody detection and PCR assays, have been developed.The sensitivity and specificity of these tests varies widely.With all of these techniques, it is interesting to note that clinical symptoms and patient history are the primary means of diagnosis in endemic areas.
Treatment of Bancroftian Filariasis
Drugs known to be active against Wuchereria bancrofti include diethylcarbamazine (DEC) and ivermectin (Stromectol) when used in combination with albendazole.DEC and ivermectin kill microfilariae.Increased doses are necessary to kill adults.The surgical removal of excess tissue may be suitable for the scrotum, but is rarely successful when performed on the extremities.The use of special boots, known as Unna’s paste boots, as well as elastic bandages and simple elevation, have proven successful in reducing the size of an infected enlarged limb.
Prevention and Control of Bancroftian Filariasis
Prevention and control measures for Wuchereria bancrofti include personal protection when entering known endemic areas, destroying the breeding grounds of mosquitoes, possibly using insecticides and educating the inhabitants of endemic areas.Avoiding mosquito-infested areas is ideal.Mosquito nets and insect repellents are more useful and useful in endemic areas.
Notes of Interest and New Trends
The origin of Wuchereria bancrofti dates back to the second millennium BC.This parasite seems to have spread through people all over the world who have explored and relocated over the years.For example, in Polynesia, early explorers of the 17th and 18th centuries learned about bancroftian filariasis.Around 1930 in Charleston, South Carolina, an epidemic caused by Wuchereria bancrofti died. It is suspected that African slaves sent to Charleston brought the infection to the United States.