Wuchereria bancrofti is also known as Bancroft’s filarial, and the diseases and conditions associated with it are known as Bancroft’s filariasis or elephantiasis. Wuchereria bancrofti is thought to have originated in the second millennium BC. This parasite appears to have spread over time as people traveled around the world exploring and relocating. When early explorers visited Polynesia in the 17th and 18th centuries, they learned about bancroftian filariasias.
In Charleston, South Carolina, an epidemic caused by Wuchereria bancrofti died out around 1930. The infection is thought to have been brought to the United States by African slaves sent to Charleston.
Morphology of Wuchereria bancrofti
The average microfilaria is 240 to 300 m long, with a thin and delicate sheath surrounding the organism. The body contains numerous nuclei. The cephalic or anterior end is blunt and round. The posterior or tail end culminates in a point devoid of nuclei. This is an important feature that distinguishes it from other sheathed microfilariae.
Adults Wuchereria bancrofti
Adult Wuchereria bancrofti worms are white and thread-like in appearance. Females are typically larger than males, measuring 40 to 100 mm versus 20 to 40 mm.
Epidemiology of Wuchereria bancrofti
W. bancrofti can be found in both subtropical and tropical climates. In the Eastern Hemisphere, these include central Africa, the Nile Delta, India, Pakistan, Thailand, the Arabian Sea coast, the Philippines, Japan, Korea, and China, and in the Western Hemisphere, Haiti, the Dominican Republic, Costa Rica, and coastal Brazil. Mosquito breeding occurs in these areas due to contaminated water. It is worth noting that indigenous residents of endemic areas are at a higher risk of contracting W. bancrofti than non-indigenous residents of these areas.
Life Cycle Notes of Wuchereria bancrofti
Mosquitoes such as Culex, Aedes, and Anopheles spp. serve as intermediate hosts and vectors of W. bancrofti. The adult worms live in the lymphatics of the human host, where they lay their microfilariae. Microfilariae are parasites that live in the blood and lymphatics.
Adult patients who were most likely exposed to W. bancrofti as children may become infected but show no symptoms. Microfilariae are commonly found in blood samples taken from these patients. These samples may also show signs of eosinophilia. Physical examination reveals only enlarged lymph nodes, most notably in the inguinal region, or groin. This type of infection is self-limiting because the adult worms die and there are no signs of microfilariae present. A patient may go through the entire procedure without even realizing it.
· Symptomatic Bancroftian Filariasis
Patients infected with W. bancrofti may experience a wide range of symptoms. They typically develop a fever, chills, and eosinophilia. The parasite’s invasion can lead to the formation of granulomatous lesions, lymphangitis, and lymphadenopathy. Streptococcus bacterial infections are also possible. Elephantiasis, or swelling of the lower extremities, particularly the legs, develops as a result of lymphatic obstruction. The genitals and breasts could also be affected. When adult worms die, calcification or the formation of abscesses may occur.
Laboratory Diagnosis of Wuchereria bancrofti
The laboratory diagnostic method of choice for W. bancrofti microfilariae is the examination of fresh Giemsa-stained blood. A more sensitive method for recovering microfilariae involves filtering heparinized blood through a special filter known as a nuclepore filter, staining, and examining the filter contents.
- The Knott method can also be used. Light infections can be detected by immersing 1 mL of blood in 10 mL of a 2% formalin solution, which lyses the red cells.
- The stained sediment is then examined under a microscope. Because this organism has nocturnal periodicity, the optimal sample is collected at night in all of these methods.
- Peak specimen collection hours are between 9:00 p.m. and 4:00 a.m., which corresponds to the appearance of its vector, the mosquito.
- Sub periodic organisms, on the other hand, are occasionally detected throughout the day. They’re more common in the late afternoon. Antigen and antibody detection assays, as well as PCR assays, have been developed as serologic tests.
- These tests’ sensitivity and specificity vary greatly. Despite the availability of all of these techniques, it is worth noting that in endemic areas, clinical symptoms and patient history are the primary means of diagnosis.
Treatment of Wuchereria bancrofti
- Diethylcarbamazine (DEC) and ivermectin (Stromectol) have been shown to be effective against W. bancrofti when used in combination with albendazole.
- Microfilariae are killed by DEC and ivermectin.
- To kill adults, higher doses are required.
- Excess tissue removal surgery may be appropriate for the scrotum, but it 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 all been shown to be effective in reducing the size of an infected enlarged limb.
Prevention and Control of Wuchereria bancrofti
- W. bancrofti prevention and control measures include wearing personal protection when entering known endemic areas, destroying mosquito breeding areas, using insecticides when necessary, and educating residents of endemic areas.
- It is best to avoid mosquito-infested areas.
- In endemic areas, mosquito netting and insect repellants are more practical and useful.
References and Sources
- CLINICAL PARASITOLOGY: A PRACTICAL APPROACH 1997 by Saunders p 224