Filariasis Lecture Notes 2024-2025 PDF

Filariasis (Elephantiasis) Prepared by: Dr. Ghada Ali 2024-2025 Objectives  By the end of this lecture you should be able to: 1. Describe Filariasis with emphasis on Wuchereria bancrofti, including its cause, sign and symptoms, pathogenesis, epidemiology, diagnosis and treatment....

Filariasis (Elephantiasis) Prepared by: Dr. Ghada Ali 2024-2025 Objectives  By the end of this lecture you should be able to: 1. Describe Filariasis with emphasis on Wuchereria bancrofti, including its cause, sign and symptoms, pathogenesis, epidemiology, diagnosis and treatment. Tissue Nematodes Disease  Wuchereria bancrofti causes filariasis.  Elephantiasis is a striking feature of this disease.  Tropical pulmonary eosinophilia is an immediate hypersensitivity reaction to W. bancrofti in the lung. 3 Life cycle of Wuchereria bancrofti  Definitive hosts: Humans are the only definitive hosts.  Intermediate host: Female mosquito, (especially Culex species).  Infective form: Actively motile third-stage filariform larva is infective to man.  Mode of transmission: Humans get infection by bite of mosquito carrying filariform larva.  Humans are infected when the female mosquito (especially Culex species) deposits infective larvae on the skin while biting. Life cycle of Wuchereria bancrofti  The larvae penetrate the skin, enter a lymph node, and, after 1 year, mature to adults that produce microfilariae.  These circulate in the blood, chiefly at night, and are ingested by biting mosquitoes. Within the mosquito, the microfilariae produce infective larvae that are transferred with the next bite. Pathogenesis & Clinical Findings  Adult worms in the lymph nodes cause inflammation that eventually obstructs the lymphatic vessels, causing edema.  Massive edema of the legs is called Elephantiasis. Wuchereria bancrofti—elephantiasis. Note massive swelling of legs bilaterally. (Courtesy of Jay S. Keystone, MD, FRCPC.)  Early infections are asymptomatic.  Later, fever, lymphangitis, and cellulitis develop.  Gradually, the obstruction leads to edema and fibrosis of the legs and genitalia, especially the scrotum.  Elephantiasis occurs mainly in patients who have been repeatedly infected over a long period. Filarial fever  Another clinical syndrome is known as filarial fever.  This is characterized by acute, self limiting episodes of fever, often in the absence of any obvious lymphangitis or lymphadenopathy.  Because of the lack of associated features, this syndrome is frequently confused with other causes of fever in the tropics, such as malaria Tropical pulmonary eosinophilia  Tropical pulmonary eosinophilia is characterized by coughing and wheezing, especially at night.  These symptoms are caused by microfilariae in the lung that elicit an immediate hypersensitivity reaction characterized by a high IgE concentration and eosinophilia. Epidemiology  This disease occurs in the tropical areas of Africa, Asia, and Latin America. The species of mosquito that acts as the vector varies from area to area. Laboratory Diagnosis  Thick blood smears taken from the patient at night reveal the microfilariae.  Serologic tests are not useful. Treatment  Diethylcarbamazine is effective only against microfilariae; no drug therapy for adult worms is available.  Treatment of patients with Wuchereria infections results in a significant decrease in the number of microfilariae in the patient.  Prevention 1. Prevention involves mosquito control with insecticides. 2. Use of protective clothing 3. Mosquito netting, and repellents. Reference  Levinson, warren. Review of medical microbiology and immunology. 15th ed. The mcgraw-hill companies, 2008. P 482 THANK YOU