In an endemic area the largest group of affected individuals in the otherwise healthy young adults and children who in-spite of being clinically asymptomatic, harbour microfilaria in their peripheral blood.
It is important to know that even at this stage of the disease abnormalities of the lymphatic vessels like dilatation appears to be irreversible even after treatment.
Attacks of fever and chills due to ADL are the commonest acute manifestations, which occur in the affected limbs or sometimes involve the genitalia. These episodes may be seen both in the early and late stages of the disease. The affected area is painful, tender, warm, red and swollen. The lymph nodes in the groin and axilla, are frequently inflamed. These acute ADL attacks recur many times a year in patients with filarial swelling, their incidence increasing with the degree of lymphedema.
Secondary infections due to bacteria like streptococci are responsible for these acute episodes. These ADL attacks are responsible for the persistence and progression of the sweliling leading on to elephantiasis not only of the limbs but also of the external genitalia and breasts.
Acute Filarial Lymphangitis: Acute manifestations directly caused by adult worms are usually rare. They are seen when the adult worms are destroyed in the lymphatics either spontaneously or by drugs like diethylcarbamazine. Small tender nodules form at the location of adult worm death either in the scrotum or along the lymphatics. Lymph nodes may become tender. Inflamed large lymphatics may stand out as long tender cords underneath the skin, usually along the sides of chest or the upper arm and axilla associated with restriction of movement of affected limb.
Though transient oedema may occur sometimes, these episodes are not associated with fever, toxemia or evidence of secondary bacterial infections.
They generally subside without any treatment. Lymphoedema and Elephantiasis: The commonest chronic manifestation of lymphatic filariasis is lymphoedema, which on progression leads on to elephantiasis. Even though lower limbs are commonly affected, upper limbs and male genitalia are frequently involved.
In females, rarely the breasts and the external genitalia may also become elephantoid. Repeated ADL episodes responsible for the progression of lymphoedema continue to occur with greater frequency in higher grades of oedema. This is due to the fact that the presence of moisture in the web spaces of the closely apposed swollen toes promotes fungal infections damaging the skin, which in turn favour of infecting organisms. For this reason the frequency of ADL episodes is shown to increase in the rainy season, when people have to wade through water in the lanes.
In brugian filariasis the lymphoedema involves only the legs below the knee and upper limbs below the elbow. Acute ADL episodes are common in affected limbs like in bancroftian filariasis. But genito-urinary lesions are not seen.
Genito-urinary lesions: Hydrocoele is common chronic manifestation of bancroftian filariasis in the males.
Chylocoele, chyluria and chylous ascites rarely occur. Microscopic and rarely macroscopic haematuria is known to occur in people with asymptomatic microfilaraemia. Tropical pulmonary eosinophilia associated with high eosinophil counts in the blood is an occult manifestation of both W.
The recent developments in the diagnosis of lymphatic filariasis are given below, which have heralded changes in the management strategies. Membrane filtration method for microfilaria detection: Venous blood drawn at night and filtered through millepore membrane filters, enables easy detection of microfilaria and to quantify the load of infection. They are usually seen in the early stages of the disease before clinical manifestations develop.
Once lyphoedema develops microfilaria are generally absent in the peripheral blood. The Quantitative Blood Count QBC methods also can be used to identify the microfilaria and to study their morphology in the blood drawn at night.
Though this can be performed quickly, it is no more sensitive than examination of the conventional blood smear. Ultrasonography: Recently, ultrasono-graphy using a 7. Ultrasound has been used to study the effect of drugs on the adult worms and to retrieve them surgically from the dilated scrotal lymphatics.
Ultrasonography is not useful in patients with filarial lymphoedema because living adult worms are generally not present at this stage of the disease.
Similarly ultrasonography has not helped in locating the adult worms of B. Lymphoscintigraphy: The structure and function of the lymphatics of the involved limb can be assessed by lymphoscintigraphy. After injecting radiolabelled albumin or dextran in the web space of the toes, the structural changes are imaged using a gamma camera.
Lymphatic dilatation, dermal back flow and obstruction can be directly demonstrated in the oedematous limbs by this method. Lymphoscintigraphy has shown that even in the early, clinically asymptomatic stage of the disease, there are lymphatic abnormalities in the affected limbs of people harboring microfilaria.
The card test has the advantage that it can be performed on blood sample drawn by finger prick at any time of the day. This test is positive in early stages of the disease when the adult worms are alive and becomes negative once they are dead.
Drugs effective against the filarial parasite: Diethylcarbamazine DEC : This drug is effective against both microfilaria and adult worms.
By ultrasonography it is shown that even single doses of DEC kills the adult worms when they are sensitive to the drug. When they are not sensitive even repeated doses do not have any effect on the adult parasite.
The adverse effects produced by the drug are seen mostly in patients who have microfilaria in their blood and are due to their rapid destruction which is characterized by fever, headache, myalgia, sore throat or cough lasting for 24 to 48 hours.
They are usually mild and self-limiting requiring only symptomatic treatment. Chronic lymphedema, or elephantiasis, is often accompanied by acute episodes of local inflammation of the skin and lymph nodes and vessels.
Some of these episodes are caused by the body's immune response to the parasite. Most of them are due to secondary cutaneous bacterial infections, since the normal defenses have weakened as a result of lymphatic injury. These acute episodes are debilitating, can last weeks, and are the main cause of absenteeism from work among those who have lymphatic filariasis. In individuals with chronic manifestations of the disease, elevation of the affected limb, hygiene, prevention, and timely treatment of skin infections are the measures to be followed.
To interrupt the transmission of filariasis in the Americas, WHO recommends, the annual simultaneous mass administration of two drugs in single dosages diethylcarbamazine and albendazole to all eligible people living in endemic areas, over a period of at least 5 consecutive years, as well as integrated vector control measures.
In a randomized, controlled trial, King and colleagues compared the effectiveness of a single dose of the three-drug regimen with a single dose of the two-drug regimen to clear microfilaremia from the blood of patients infected with W.
They also comparted the three-drug regimen administered once compared with the two-drug regimen administered once a year for 3 years. Between June 11 and Dec. They randomly assigned 60 participants to receive a single dose of the three-drug regimen, 61 to receive a single dose of the two-drug regimen and 61 to receive the two-drug regimen once a year for 3 years.
At 36 months the groups consisted of 54, 52 and 52 participants, respectively. The primary outcome was complete clearance of microfilaremia 36 months after trial initiation. Incomplete or delayed clearance of microfilaremia can contribute to continued transmission.
Disclosure s : King reports no relevant financial disclosures. Through mass drug administration, we have the potential to eliminate the ancient scourge of lymphatic filariasis.
The new report from The New England Journal of Medicine finds that we can accelerate global elimination efforts by moving from a two-drug to a three-drug regimen. It is an important and timely advance. We now need to evaluate the potential impact of the three-drug regimen on additional and coendemic infections, including soil-transmitted helminth infection and possibly some ectoparasitic conditions.
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