Lymphatic filariasis

Description, Causes and Risk Factors: Abbreviation: LF. Lymphatic filariasis is a serious socioeconomic and public health problem in the world. As on December 2006, the total population at risk for LF was estimated to be 1254 million in 83 endemic countries, of which 64% contributed by Southeast Asia region alone. Lymphatic filariasis is transmitted by mosquitoes which carry infective larvae of the filarial parasites Wuchereria bancrofti (the bancroftian filaria, a species endemic in South Pacific islands, coastal China, India, and Burma, and throughout tropical Africa and northeastern South America (including certain Caribbean islands); transmitted to humans (apparently the only definitive host) by mosquitoes, especially Culex quinquefasciatus and Aedes pseudoscutellaris, but also by several other species of Culex, Aedes, Anopheles, and Mansonia, depending on the specific geographic area; adults are white, 40-100 mm cylindroid, threadlike worms, and the microfilariae are ensheathed, with rounded anterior end and tapered, non-nucleated tail; the adult worms inhabit the larger lymphatic vessels (e.g., in the extremities (especially lower), breasts, spermatic cord, and retroperitoneal tissues) and the sinuses of lymph nodes (e.g., the popliteal, femoral, and inguinal groups, and also the epitrochlear and axillary nodes), where they sometimes cause temporary obstruction to the flow of lymph and slight or moderate degrees of inflammation) or Brugia malayi (the Malayan filaria species, an important agent of human filariasis and elephantiasis in Southeast Asia and Indonesia, transmitted to humans by species of Mansonia and Anopheles mosquitoes; adult parasites cause lymphangitis and lymphadenitis, but there is less involvement of the genital region and lower extremities, and a relatively greater incidence of disease in the upper extremities than with Wuchereria bancrofti infection. Formerly called Wuchereria malayi) from one person to the next. Brugia timori is limited to the Timor Island of Indonesia. The mosquitoes bite infected humans and pick up the microfilariae from the blood. The microfilariae then develop inside the mosquito into the infective larval stage in a process that usually takes seven to 21 days. The larvae then migrate to the mosquitoes' mouth, ready to enter the bloodstream of the next unsuspecting individual the mosquito bites. The larvae migrate from the site of the bite to the lymphatic system, thus completing the life cycle. Symptoms: Typically, lymphatic filariasis does not have clinical symptoms, such as flu-like symptoms, fever, or vomiting. In fact, most people with lymphatic filariasis are unaware they have it. In a small percentage of infected people, lymphedema, or swelling, will occur, typically appearing years after the initial infection. The characteristic swelling can occur in the arms, legs and chest, but also in the genital areas such as the scrotum and penis, where it is very painful. Left untreated, the disease can progress into a hardening and scarring of the tissues of the legs called elephantiasis. This is due to both the buildup of lymph fluid and the impaired ability of the lymph to fight infections, leaving affected people more susceptible to germs and bacteria. By the time people develop elephantiasis, most no longer have active filariae in their body. Symptoms that might indicate severe condition may include:
  • Chills or shaking.
  • Excessive sweating.
  • Headache.
  • High fever (higher than 101 degrees Fahrenheit).
  • Muscle aches and pains.
  • Nausea with or without vomiting.
  • Nonspecific test abnormalities - Eosinophilia up to 3000/mL.
  • Blood examination for detection of microfilariae should be performed in all individuals in whom the diagnosis of filariasis is suspected. Bancroftian and Brugian filariasis tend to show nocturnal periodicity. Blood should be drawn between 10 p.m. and 2 a.m. because the greatest number of microfilariae can be found in blood during this peak biting time of the mosquito vectors. The pattern of periodicity can be reversed by changing the patient's sleep-wake cycle.
  • Antibody tests — Serologic tests for filarial antibodies which detect elevated levels of IgG and IgE are available.
  • Antigen tests — Different methods for detection of antigen in the blood have been attempted using various monoclonal antibodies.
Treatment: The recommended regimen for treatment through mass drug administration (MDA) is a single dose of two medicines given together - albendazole (400 mg) plus either ivermectin (150-200 mcg/kg) in areas where onchocerciasis (river blindness) is also endemic or diethylcarbamazine citrate (DEC) (6 mg/kg) in areas where onchocerciasis is not endemic. These medicines clear microfilariae from the bloodstream and kill most of the adult worms. Mosquito control is another measure that can be used to suppress transmission. Measures such as insecticide-treated nets or indoor residual spraying may help protect populations in endemic regions from infection. Patients with chronic disabilities like elephantiasis, lymphoedema, or hydrocele are advised to maintain rigorous hygiene and take necessary precautions to prevent secondary infection and aggravation of the disease condition. NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.  


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