Etiology of Elephantiasis
Elephantiasis is primarily caused by lymphatic filariasis, a parasitic infection transmitted by mosquitoes, with the vast majority of cases (approximately 90%) caused by Wuchereria bancrofti, and the remainder by Brugia malayi and B. timori. 1
Primary Infectious Causes
Lymphatic Filariasis (Most Common)
Parasitic agents: Wuchereria bancrofti accounts for the majority of lymphatic filariasis cases globally, while Brugia malayi and B. timori cause the remainder 1, 2
Transmission mechanism: The disease is transmitted through the bite of infected mosquitoes, including Aedes spp., Anopheles spp., and Culex spp. 1
Pathophysiology: The filarial worms have a predilection for the lymphatic system, where adult worms cause progressive lymphatic damage 3. Most infections are initially asymptomatic but cause lymphatic damage nevertheless, eventually leading to chronic lymphoedema (previously referred to as elephantiasis) and scrotal oedema/hydrocoele 1
Geographic distribution: W. bancrofti was previously highly prevalent throughout equatorial areas but is now much reduced, remaining endemic in parts of Africa, West Pacific, and Caribbean, with sporadic cases in South America, India, and Southeast Asia 1. B. malayi and B. timori are mainly found in Southeast Asia 1
Prepatent period: W. bancrofti has a prepatent period of 7-8 months, while B. malayi has a 2-month prepatent period 1
Non-Filarial Causes
Podoconiosis (Non-Filarial Elephantiasis)
Etiology: An immune disease caused by heavy metal exposure affecting the lymph vessels, distinct from lymphatic filariasis 4
Exposure mechanism: Predominantly affects barefoot subsistence farmers in areas with red volcanic soil through chronic exposure to irritant soil particles 4
Geographic distribution: Ethiopia has one of the highest numbers of podoconiosis patients, with many people at risk due to red-clay soil exposure 4
Key distinction: Unlike lymphatic filariasis which affects all populations at risk, podoconiosis specifically affects those with chronic barefoot exposure to volcanic soil 4
Elephantiasis Nostras
Etiology: Results from longstanding chronic lymphangitis with various underlying causes including bacterial infections, neoplasia, obesity, and in many cases uncertain etiology 5
Pathophysiology: Chronic lymphedema leads to marked skin changes including hyperkeratosis, ulceration, deep skin folds, and cobblestone appearance 5
Important Clinical Distinctions
It is critical to distinguish lymphatic filariasis from other causes of elephantiasis, as treatment approaches differ fundamentally. 1, 4
- Lymphatic filariasis requires antiparasitic treatment with diethylcarbamazine (DEC) plus doxycycline 1
- Podoconiosis requires prevention through footwear and management of lymphedema 4
- Elephantiasis nostras requires treatment of underlying causes and lymphedema management 5
Human hookworm infection (Ancylostoma duodenale and Necator americanus) should not be confused with elephantiasis, as hookworm causes minimal skin symptoms and proceeds to systemic infection rather than causing lymphatic obstruction 6