THM1) Of the several filarial infections, lymphatic filariasis is the one we see in india. Onchocerciasis and Loa Loa don’t occur here.
THM2) Lymphatic filariasis is caused by 3 filarial nematodes: Wucheraria bancrofti, Brugia malayi and Brugia timori. In India 90% cases are W. bancrofti and 10% B.malayi.
THM3) Two important acute manifestations of filariasis are ADL and ADLA. ADL stands for acute adenolymphangitis and ADLA stands for acute dermatolymphangitis.
THM4) ADL has high fever, tender lymphadenitis, lymphangitis and local oedema. ADL may occur several times per year affecting the lower limbs, genitalia or rarely the upper limbs. Attacks may be uni or bilateral and resolve spontaneously in approx 1 week.
THM5) ADLA as the name suggests has prominent skin changes that look like cellulitis. There is also high fever with chills. ADLA is caused not by filarial worms but probably by secondary bacterial infection in limbs with compromised lymphatics. Antibiotics are hence indicated.
THM6) Recurrent attacks of both ADL and ADLA cause progressive lymphatic damage and obstruction that may lead to chronic lymphoedema and elephantiasis.
THM7) Tropical pulmonary eosinophilia (TPE) is a term used in filariasis for lung hypersensitivity to migrating larvae (microfilariae) of filarial worms. It is commoner in males.TPE presents with cough and wheezing (more at night) that can last for weeks or months. If untreated, TPE can progress to chronic interstitial fibrosis. These patients typically have blood eosinophil count of >2000.
THM8) Simple pulmonary eosinophilia or Loffler’s syndrome is a term used for lung affectation by migrating roundworm or hookworm. The following features clinically differentiate Loffler’s from TPE-
1. H/o passage of worms
2. Low Hb and low MCV s/o blood loss
3. Patients without cough and wheezing
4. Patients with absolute eosinophil count <2000
In these patients with simple pulmonary eosinophilia, use only deworming drugs like albendazole and avoid DEC.
THM9) Wolbachia is the name of an amazing bacterium that indirectly affects humans! It infects insects (eg: mosquitos, flies), mites, spiders and importantly filarial worms. Wolbachia has a symbiotic ‘live-in’ relationship with microfilariae and adultworms! Killing Wolbachia with antibiotics causes death of filariae too.This is why a course of doxycycline (200 mg/day in adults) for 6 to 8 weeks is considered to deplete Wolbachia and indirectly kills both micro and macrofilariae.
THM10) Tests for circulating filarial antigen and antifilarial antibody each cost approx Rs.800/-. Microfilaria can also be seen on smear done at night time. Prefer asking for antigen in patients presenting with suspected acute filariasis. In patients with suspected tropical pulmonary eosinophilia, do the antibodies.
(This article was written in 2014)