Introduction

Elephantiasis is a disease which causes various parts of the body – most commonly the limbs, arms and legs – to increase in size. These symptoms arise due to the swelling and hardening of  the tissues, which could lead to a permanent disfigurement of the limbs. Elephantiasis is most commonly caused by lymphatic filariasis (LF), an infection of parasitic filarial worms transmitted through insect bites.¹ The term lymphatic refers to the lymphatic system, a collection of tissues, vessels and organs that is a part of the immune system, while filariasis refers to an infection caused by parasitic nematodes (round worms) that live in the lymphatic vessels of their hosts.

LF is known as a neglected tropical disease (NTD), which is a group of health conditions caused by various pathogens such as viruses, bacteria, parasites, fungi, and toxins. These illnesses can have serious effects on a person's health, social life, and overall well-being. NTDs are mostly found in poor underprivileged communities in tropical regions, although some can be spread over much larger areas.⁴ LF is regularly found in 73 countries across Asia, Africa, and the Americas, impacting around 120 million people across the globe.⁷ 

Causes

LF is transmitted through the bites of blood-feeding mosquitoes that are infected with parasitic nematodes (round worms) of the species Wuchereria bancrofti.⁵

W. bancrofti can live for up to six to eight years in the body, producing millions of immature larvae (microfilariae) which circulate in the blood before maturing into adult worms. When a person is bitten by an infected mosquito, the immature larvae travel through the blood of the mosquito into the skin of its victims. The microfilariae then migrate into the victim’s tissues, where they become adult worms and continue to produce millions of their own immature larvae.⁶ 

Symptoms

Typically, 2 in 3 people with LF do not present any symptoms, although it typically leads to a weakened immune system.⁸ 

However, those who do present symptoms often experience inflammation, lymphedema, hydrocele and edema.¹

Inflammation

Inflammation is the body’s natural protective response against foreign objects and infectious agents such as toxic chemicals or germs. Classic signs of inflammation include heat, pain, redness, swelling and loss of function. This is a normal immune response that works to expel the foreign object, allowing the body to heal.⁹ 

Lymphedema

Lymphedema is swelling caused by disruptions in the lymphatic system, which normally collects excess fluid, proteins, and toxins from tissues and returns them to the bloodstream.

When these disruptions occur, the body starts to build up excess fluid. The lymphatic system begins to swell, affecting the arms, legs and other body parts.

Depending on where lymphedema affects the body, it can restrict daily movements such as walking, getting changed and driving, which might hinder your ability to perform daily tasks.¹⁰ 

Hydrocele

A hydrocele is a fluid-filled sac in the scrotum that causes swelling in those assigned male at birth (AMAB). The scrotum is the skin pouch behind the penis that contains the testicles. Hydroceles can affect one or both sides. Bilateral hydrocele occurs when swelling affects both testicles.

Hydroceles can be concerning because they can develop quickly and lead to swelling in a delicate area. Sometimes, they can be uncomfortable depending on how big they become. A larger hydrocele might make sitting or walking uncomfortable. However, for many people AMAB, a hydrocele does not interfere with daily life.¹¹ 

Edema

Edema refers to swelling that occurs due to fluid trapped in the tissues of the body. Edema is most commonly found in the legs, ankles and feet, but can also affect the face, hands and abdomen, as well as the breasts, vulva, penis and scrotum.¹ Unlike lymphedema, edema is only found in tissues independent of the lymphatic system. 

Similar to lymphedema, edema is characterised by the rapid swelling of one or more body parts. It is often accompanied by tightness or pain. The skin of the affected area may appear stretched and shiny. Edema can also cause difficulty in moving or performing daily activities.¹² 

Due to the similarities between lymphedema, hydrocele and edema, it is important to rule out that the condition was a result of parasitic worms, as these symptoms can manifest as separate conditions on their own for other reasons. Therefore, undergoing extensive diagnostic approaches is important for the patient to receive appropriate care.

Diagnosis

Laboratory Test

Giemsa Stain

Until just a short time ago, diagnosing lymphatic filariasis was very challenging because it required looking for parasites under a microscope in the blood. In many parts of the world, filarial worms exhibit nocturnal periodicity – meaning they are only present in the blood during a narrow time window around midnight, which makes detection even more difficult.⁶

However, with a simple blood test, with the blood sample collected at night time, a thick smear is stained with a Giemsa Stain, which is the gold-standard technique to detect parasites in the blood.¹³

The stain is made up of a mixture of dyes which bind to different cell components based on their acidity and DNA, as blood and parasites are different, it will stain them both in different colours, making the Giemsa stain a very simple and accurate diagnostic technique.¹⁴

Antibody Test

When your body is actively fighting against an infection, it creates unique antibodies to fight off the source of the infection. Antibody tests are used to confirm that your body is producing the antibodies associated with the infection that is being diagnosed.¹⁵

The antibody that is associated the most with LF is IgG4.¹⁶

Polymerase Chain Reaction

Polymerase-Chain Reaction (PCR) tests are precise and very sensitive methods that can find roundworm DNA in human blood samples.¹⁷

A PCR test is a method used to detect genetic material (DNA or RNA). After collecting a sample of body fluid, like your blood, or a swab from a specific area. Scientists use PCR to make many copies of the DNA that was present in the original sample. This process, called amplification, allows scientists to examine the DNA or RNA more easily and in greater detail, making it easy to find roundworm DNA that should not be in your DNA.¹⁸

Imaging

Imaging LF is a useful way to see how the infection affects the body¹⁹. Imaging methods include ultrasound and lymphoscintigraphy.

Ultrasound

Ultrasound is where sound waves are used to scan the structures of soft tissues in the body, which is often why it is used for pregnancy, as it can be non-invasive and harmless to the tissues.²⁰

A common ultrasound technique associated with diagnosing LF is B-mode imaging, which is a black-and-white ultrasound image in two dimensions, showing organs and tissues as different shades of brightness, so any tissues that have swollen can be looked at in greater detail.²¹

Lymphoscintigraphy 

Lymphoscintigraphy is a type of imaging test that uses very small amounts of radioactive material to take detailed pictures of the lymphatic system in the body.²²

This enables easy and accurate assessment of how the lymphatic system is working in patients who are at risk and may have lymphatic problems due to LF.²¹

Prevention & Treatment

Whilst there is no cure for LF, medication is available which can kill many of the worms before they can start maturing and infecting your body, which can also help with symptoms.¹

LF can be prevented by using appropriate measures when you are living or travelling in tropical climates where a filariasis infection is likely. These include: sleeping under a mosquito net, using insect repellent, especially at night and covering up arms and legs are a great way to prevent contracting a filariasis infection.¹