Main Characteristics of Wuchereria Bancrofti - Research Paper Example

Phylum/family/Genus: Parasitic helminthes/ Nematodes Species: Wuchereria bancrofti Taxonomy Wuchereria Bancrofti belongs to the domain Eukaryota which consists of all life forms with the ability to act or function independently as opposed to the prokaryote kingdom which are unicellular and lack membrane bound nuclei. This domain belongs to the animalia kingdom and the subkingdom bilateria. Bilateria has a mesoderm, endo and also ectoderm (Bilateria). The branch is the protostomia’s within the infra kingdom ecdysozoa. The ecdysozoa is the largest group within the animal kingdom and includes the arthropods and the nematodes (Introduction). Furthermore, members of the bilateria subkingdom are bilaterally symmetrical with a left and right side to their body. Nematoda phyla are members of the super phylum group aschelminthes of the class secernentea; the subclass spiruria and the order spirurida. The suborder is the spirurina. Nematodes are roundworms and one of the most diverse of all animals with over 28,000 having been described, of which 16,000 are parasitic. Secernentea are the main class of nematodes which are characterized by an excretory system and no circulatory or respiratory system (Secernentea). Spiruria, spirurida and spirurina are parasitic nematodes belonging within the superfamily filarioidea of the family filariidae. Filariidae contains a total of six genuses, brugia, filaria, ichthyonema, onchocerca, parafilaria, and the genus wuchereria, the specific name being bancrofti and the scientific name wuchereria bancrofti. Main Characteristics W. bancrofti have eight circumoral papillae forming two circles, an inner and an outer and two lateral amphids, with an unpaired papilla anterior to the cloacal aperature in the male. Only the males contain cuticular striations on the ventral surface which are anterior to the cloacal aperature (Buckley and Singh 127). The distal end of the right spicule is a heavily cuticularised subterminal triangular piece and the female tail has minute cuticular bosses on the left side which are posterior to the anus and there is also one phasmid. Ultrasonography visualization of the filarial worms usually shows them in a nested pattern with the worms viewed as wavy bands (NR De Silva 82). The vector of W. bancrofti is the mosquito culex quinquefasciatus and the parasite is spread through the bite of the mosquito and is carried from person to person in countries that are subtropical and tropical. A male and female W. bancrofti will mate within the lymphatic vessels and the female will create thousands of microfilariae within the bloodstream. They are nocturnal and during periods of sleep will travel in the bloodstream near the surface in peripheral blood vessels. This action allows them to be ingested by night time mosquitos and facilitates their spread. The microfilariae are sheathed and these sheaths are shed once ingested by a mosquito so that the microfilariae can penetrate the mosquitos mid gut and make its way to the thoracic cavity (Wuchereria). After the larvae have matured it will migrate to the mosquito’s proboscis where it will be injected when the mosquito takes a blood meal. Mosquitos act only as intermediate hosts while human beings are the definitive host. Pathogenicity Infection known as lymphatic filariasis, or elephantiasis, results when filiarial worms are transmitted to humans. Infection is most often acquired during childhood and the majority of infections are asymptomatic. It is usual for a person to need multiple exposures to acquire infection. When the nematode blocks the lymphatic’s the body reacts by creating an allergic reaction which includes fever, chills, shaking, sweating, vomiting, headaches and local pain. The affected area will eventually harden and become cracked which allows bacterial infections to develop. Hence, impaired lymphatic flow may develop. The nematode is thought to secrete a protein which stimulates B-cells, but does not activate. Conversely, it desensitizes them to activation signals (Elephantiasis). Fluid becomes unable to drain which causes extensive swelling and often splitting and cracking of the skin. Where lymphedema is present activated T-cells and Natural Killer cells secrete interferon which causes infection and localized clotting. Swelling causes lack of blood flow which can result in gangrene. Poor sanitation along with very dense areas are prime breeding grounds for mosquitos which harbor the bancrofti. Nations which have poor sanitization have a higher degree of secondary infections. A pregnant woman who is infected is three times more likely to have a child who is also infected indicating the antigen likely passes through the fetal circulation in utero. Epidemiology Lymphatic Filiariasis is endemic in 83 countries with 70% of cases being reported in India, Indonesia, Nigeria, and Bangladesh (Lymphatic). More than 120 million people are currently infected with 25 million males suffering from genital swellings and 15 million who suffer from elephantiasis and severe swelling of the leg. Those populations who are at high risk for contracting the disease are primarily poor and most infections are found in rural areas. Poor sanitation and housing quality are also common factors in infections. Communities and housing found near rivers and marshlands are primary vectors for the causative agent of infection. The World Health Organization estimates that less than 1% of transmissions are in urban areas though very little research has been done in this area. A 1988 study completed in Leogane, Haiti, found that an alarming 140 of 421 individuals were infected. This is attributed to the numerous rum distilleries around the periphery of the city (Raccurt). A 1996 study which consisted of one year in several rural villages in South India concluded that infection was strongly age dependent and that there were approximately 97 occurrences per 1000 individuals annually. No seasonal pattern was detected and swelling of the lymph nodes in the inguinal area were the most common symptoms of acute disease (Ramaiah). No W. Bancroft or form of human filariasis is endemic within the United States though it was at one time prevalent in Charleston, South Carolina. The World Health Organization has named lymphatic filariasis as the second leading permanent and long term disability causing disease in the world. Treatment Patients may be asymptomatic and symptoms will often not surface until adolescence or adulthood. Lymphatic filariasis has been described as three acute syndromes: acute ADL, filarial fever and tropical pulmonary eosinophilia. Symptoms will range from febrile and painful lymphadenopathy, cloudy urine, dry cough, wheezing, dyspnea, weight loss, anorexia, and malaise (Wayangankar). Chronic manifestation of bancrofti results most commonly in hydrocele. Microfilariae is usually demonstrated through microscopic detection in the blood through either a capillary stick or venous withdraw. A skin snip test is also used for diagnosis of microfilariae. Patients with coetaneous filariasis may require lymph node biopsy. Patients can be treated on an outpatient basis though treatment does not change the prognosis. Irreversible fibrosis destroys lymphatic tissue and the benefits of treatment or whether treatment will slow the progress of the disease (Wayangankar; Siddharth). Standard treatment of W. bancrofti is an annual mass treatment of ivermectin and albendazole. Higher dosing and increased frequency to twice annually have been proven to result in more sustained microfilariae clearance; this treatment has been shown to cause adverse reactions such as inflammatory reactions. Treatment with doxycycline for a period of three weeks has been shown to induce long-term amicrofilaremia but was ineffective in curative effects (Turner). Supportive care includes hygiene, elevation of affected area, antiseptic creams, comfortable footwear and exercise of the affected limb in order to increase blood flow. Large hydroceles and elephantiasis can also be treated with surgical excision. Fatty foods are restricted and exercise is strongly encouraged. Medication is provided to eradicate the infection, prevent complications and decrease morbidity. Works Cited “Bilateria.” Science. Web. 24 Apr. 2012. . Buckley, J. J. C. and S. N. Singh. “On the Structure of Wuchereria bancrofti Adults from India, with a Note on Male Specimens from British Guiana and Fiji”. Journal of Helminthology, 39 , pp. 127-136. doi:10.1017/S0022149X00020538. “Elephantiasis.” Biology @ Davidson. 2006. Web. 25 Apr. 2012. http://www.bio.davidson.edu/courses/immunology/students/spring2006/heeren/eleph.html “Introduction to the Ecdysozoa.” UCMP. Web. 24 Apr. 2012. . “Lymphatic Filariasis Epidemiology.” Stanford University. Web. 25 Apr. 2012. . Raccurt, CP et al. “Supplemental Content.” National Center for Biotechnology Information. U.S. National Library of Medicine, 1988. Web. 25 Apr. 2012. . Ramaiah, KD, Ramu, Kumar, and Guyatt. “Supplemental Content.” National Center for Biotechnology Information. U.S. National Library of Medicine, 1996. Web. 25 Apr. 2012. . “Secernentea.” (Class). 23 Feb. 2012. Web. 24 Apr. 2012. http://zipcodezoo.com/Key/Animalia/Secernentea_Class.asp Silva, N. R. et al. “Ultrasonographic Visualisation Of Live Wuchereria Bancrofti Adult Worms In Situ.” Ceylon Medical Journal 56.2 (2011): 82-83. CINAHL Plus with Full Text. Web. 25 Apr. 2012. Turner, Joseph et al. “Clinical Infectious Diseases.” A Randomized, Double-Blind Clinical Trial of a 3-Week Course of Doxycycline plus Albendazole and Ivermectin for the Treatment of Wuchereria Bancrofti Infection. June 2006. Web. 25 Apr. 2012. . Wayangankar, Siddharth. “Filariasis Clinical Presentation.” MD LLC. Ed. Burke Cunha. 8 Dec. 2010. Web. 25 Apr. 2012 . Wayangankar, Siddharth. “Filariasis Treatment & Management.” Md LLC. Ed. Burke Cunha. Dec. 2010. Web. 25 Apr. 2012 . “Wuchereria Bancrofti - Lymphatic Filariasis - Elephantiasis.” Parasites In Humans. 2012. Web. 25 Apr. 2012. . Read More