Filariasis.

Filariasis is a parasitic disease caused by thread-like worms transmitted by mosquitoes. The most common form, lymphatic filariasis, damages the body's drainage system and can cause severe swelling of the legs, breasts, or genitals over many years. Treatment combines deworming drugs with strict skin hygiene and supportive care.

Filariasis spreads through bites of infected Culex, Anopheles, Mansonia, or Aedes mosquitoes. The mosquito injects infective larvae that migrate to lymphatic vessels, where they mature into adult worms over 6-18 months. It is not contagious between people. Repeated exposure over years is needed to develop chronic disease.

Most people are initially asymptomatic. Early features include episodes of fever with painful lymph node swelling (ADL), mild non-pitting ankle edema, recurrent cellulitis on one leg, or unexplained eosinophilia on routine blood tests. Many cases are detected only by blood tests during community surveys.

Filariasis is the underlying parasitic infection. Elephantiasis is the late, irreversible consequence — gross thickening and disfigurement of an affected limb caused by years of lymphatic damage, recurrent bacterial infection, and fibrosis. Not all filariasis progresses to elephantiasis, especially with early treatment and good hygiene.

Active infection is curable with deworming drugs that kill microfilariae in over 95% of patients and adult worms over 12-24 months when doxycycline is added. Established elephantiasis is not fully reversible, but acute attacks can be reduced by more than 80% with hygiene-based morbidity management.

First-line drugs are diethylcarbamazine (DEC), ivermectin, and albendazole, often combined as a single-dose triple therapy (IDA) in WHO-endorsed mass treatment. Doxycycline 200 mg/day for 4-6 weeks targets the Wolbachia bacteria inside the worm and is uniquely able to kill adult parasites.

The microfilariae of Wuchereria bancrofti and Brugia malayi rise into peripheral blood mainly between 10 p.m. and 2 a.m. to match the biting habits of their mosquito vectors. Blood smears taken at this time have the highest yield. Antigen tests and PCR have removed this limitation.

Yes. Microfilaremia is regularly detected in children as young as 5 years in endemic regions, and chronic lymphedema can begin in adolescence with heavy exposure. Mass drug administration includes school-age children at age-appropriate doses. Doxycycline is avoided under age 8.

Mass drug administration (MDA) is annual treatment of entire endemic populations regardless of symptoms. Standard regimens are DEC + albendazole, or ivermectin + albendazole where onchocerciasis is co-endemic, or triple therapy IDA. Five to seven yearly rounds typically interrupt transmission. Over 100 million people have received MDA in India alone.

Sleep under an insecticide-treated bed net, use mosquito repellents at dusk and dawn, eliminate stagnant water around the home, and participate in annual community deworming campaigns. Travelers to endemic regions for short trips face very low individual risk; long-term residents and workers should use vector-control measures.

Yes. India accounts for roughly 40% of the global lymphatic filariasis burden, with 14 endemic states and around 600 million people at risk. The Government of India National Vector-Borne Disease Control Programme runs annual MDA rounds with IDA in target districts and aims for elimination as a public-health problem by 2027.

Adult Wuchereria bancrofti worms live in the lymphatic vessels around the testis and spermatic cord. Over years they dilate and obstruct these vessels, causing lymph and fluid to accumulate within the tunica vaginalis around the testis. The resulting hydrocele is the most common chronic manifestation of W. bancrofti infection.

Tropical pulmonary eosinophilia (TPE) is a hyperreactive immune response to microfilariae trapped in pulmonary capillaries. It causes nocturnal cough, wheeze, and breathlessness in young adults from endemic regions, with eosinophilia over 3,000/µL and IgE over 1,000 IU/mL. It responds dramatically to DEC.

Brief travel rarely produces overt disease because chronic filariasis requires sustained, repeated exposure. Aid workers, missionaries, military personnel, and long-stay expatriates in endemic regions are at higher risk. Travelers with persistent eosinophilia, fevers, or limb swelling after an endemic stay should be screened with filarial antigen and serology.

The filarial dance sign is the chaotic, flickering motion of adult Wuchereria worms inside dilated lymphatic vessels seen on scrotal or breast ultrasound. It is pathognomonic for active W. bancrofti infection and is used to confirm live adult worms before macrofilaricidal treatment.

Repeated bacterial infection of cracked or fungally infected skin is the main driver of acute attacks and progression to elephantiasis. Twice-daily washing with soap and water, antifungal care between toes, and prompt treatment of any cut or blister reduces ADL frequency by more than 80% in WHO morbidity-management programmes.

Active microfilaremia is associated with chronic anemia and lower birth weight but does not cross the placenta to infect the fetus directly. DEC and albendazole are avoided in pregnancy where possible; deferral to postpartum is preferred. Doxycycline is contraindicated.

No. River blindness (onchocerciasis) is caused by Onchocerca volvulus and transmitted by black flies, not mosquitoes. It produces skin nodules, severe itch, and blindness, with microfilariae in skin rather than blood. DEC is contraindicated in onchocerciasis; ivermectin is the standard treatment.

Microfilariae can return without further treatment if adult worms remain alive in the lymphatics and if re-exposure continues. Annual MDA prevents this. Doxycycline targets adult worms and reduces relapse risk substantially. Travelers without further endemic exposure rarely relapse after cure.

No licensed vaccine exists for human lymphatic filariasis. Several candidate vaccines targeting adult worm and infective-larval antigens are in preclinical or early clinical development, but none is available outside of trials. Control depends on vector management, mass drug administration, and morbidity management.

Repeat blood antigen or microfilarial testing at 6 and 12 months confirms parasitological cure; clinical assessment of limb volume and ADL frequency tracks morbidity. Annual MDA rounds continue at the community level. Travelers without re-exposure usually need no further follow-up after a documented cure.