Causes Elephantiasis , lymphatic filariasis (LF) 22/08/25

Introduction

Elephantiasis, medically termed lymphatic filariasis (LF), is a debilitating, disfiguring neglected tropical disease. It results from lymphatic system damage caused by parasitic worms, leading to swelling, thickening of skin and tissues (elephantiasis), as well as genital deformities such as hydrocele (WHO 2024) 

Causative Agents and Transmission Cycle

1. Parasitic Worms

LF is caused by infection with thread-like filarial nematodes: Wuchereria bancrofti, Brugia malayi, and Brugia timori (WHO 2024; Wikipedia 2025)  

  • Wuchereria bancrofti is the predominant species, responsible for approximately 90 % of global cases (WHO 2020 Q&A)  

  • Brugia malayi and Brugia timori account for most remaining cases and have more restricted geographic distributions (Wikipedia 2025; PAHO/WHO) 

  • B. malayi, for example, is largely confined to South and Southeast Asia and typically does not lead to genital involvement such as hydrocele, unlike W. bancrofti  

2. Mosquito Vectors and Lifecycle

Transmission occurs via several mosquito genera — primarily Anopheles, Culex, Aedes, and Mansonia — which serve as intermediate hosts (WHO; IAMAT)  

The parasite lifecycle:

  1. Mosquito takes a blood meal from an infected host and ingests microfilariae (immature larvae).

  2. Within 10–20 days, microfilariae mature to infective larvae inside the mosquito.

  3. The mosquito transmits the infective larvae to a human by biting.

  4. Larvae invade the human’s lymphatic system, gradually developing into adult worms over ≈1 year.

  5. Adult females (up to 10 cm long) produce microfilariae continuously for their life span (~5–8 years), which circulate in the bloodstream, especially nocturnally (Wikipedia 2025)  

This ongoing cycle perpetuates community transmission, primarily in tropical and subtropical endemic regions, including parts of Africa, Asia, the Western Pacific, the Caribbean, and South America (WHO; Verywell Health) (World Health Organization, Verywell Health).

Pathophysiology: How Elephantiasis Develops

1. Lymphatic System Damage and Dysfunction

Once adult worms inhabit lymphatic vessels, they cause progressive damage via:

  • Mechanical obstruction by the adult worms themselves.

  • Chronic inflammation and immune responses resulting in vessel dilation, fibrosis, and impaired lymph drainage ( PAHO/WHO; Verywell Health)  

  • Death of worms and antigen release can propagate further inflammation and lymphatic scarring  

2. Lymphoedema and Elephantiasis

Initially, lymphatic impairment leads to lymphoedema — tissue swelling due to fluid accumulation. Repeated inflammatory episodes and secondary infection eventually lead to elephantiasis, where skin and subcutaneous tissues become thickened, fibrotic, hyperkeratotic, and rigid — giving the characteristic "elephant-like" appearance (Verywell Health)  

3. Genital Manifestations

Particularly in W. bancrofti infections, the lymphatic damage often involves the male genital tract, resulting in hydrocele — accumulation of fluid around the testes — and scrotal swelling (Guardian 2024; WHO)  

4. Acute Inflammatory Attacks

Patients may experience recurrent acute episodes of pain, fever, and localized inflammation ("acute attacks") often triggered by secondary bacterial infections, further exacerbating lymphatic damage (WHO 2025; PAHO/WHO)  

5. Other Causes of Elephantiasis (Non-filarial)

Although LF is the primary cause globally, elephantiasis can also occur due to non-infectious causes:

  • Other infections such as leishmaniasis, tuberculosis, lymphogranuloma venereum, or leprosy.

  • Repeated streptococcal infections.

  • Environmental exposures (e.g., silica).

  • Cases with no identifiable cause (idiopathic) (NORD 2019) 

Podoconiosis, a form of non-filarial elephantiasis, arises from a genetically determined inflammatory response to mineral particles in volcanic soils — also leading to lymphatic blockage and limb swelling (Wikipedia 2025)  

Epidemiological Context

LF is endemic in 72 countries, with more than 120 million people infected and over 850 million at risk (WHO; Eisai)  

  • In 2023, around 657 million people lived in areas requiring preventive chemotherapy to interrupt transmission; 51 million were infected, with 36 million suffering chronic manifestations such as lymphoedema or hydrocele (WHO)  

  • The disease disproportionately affects marginalized, poor populations with limited access to effective sanitation, healthcare, and vector control (Guardian 2024)  

Conclusion

Elephantiasis (lymphatic filariasis) arises from chronic obstruction and inflammation of the lymphatic system due to filarial worm infection, primarily Wuchereria bancrofti but also Brugia spp., transmitted by mosquitoes. The pathology includes lymphoedema, elephantiasis, acute attacks, and genital swelling. Non-filarial forms exist but are relatively rare.

References 

  • WHO (2024) Lymphatic filariasis, WHO Fact sheet, 21 Nov. Available at: WHO website (accessed 22 Aug. 2025). (World Health Organization)
  • WHO (2025) Lymphatic filariasis (Elephantiasis), WHO Health Topics. Available at: WHO website (accessed 22 Aug. 2025). (World Health Organization)
  • Verywell Health (2018) An Overview of Elephantiasis. Verywell Health, 11 Sep. (Verywell Health)
  • Guardian (2024) Growth the size of a melon: a scrotum-swelling disease threatening thousands, 25 Oct. (The Guardian)
  • Eisai (2022) Lymphatic Filariasis, Eisai Sustainability. Available at: Eisai.com (accessed 22 Aug. 2025). (eisai.com)
  • IAMAT (2020) Lymphatic Filariasis, IAMAT Travel Health. Available at: Iamat.org (accessed 22 Aug. 2025). (IAMAT-FSIMT)