What is Filariasis?
It is a parasitic disorder and globally considered to be a Neglected Tropical Disease- a group of ailments prevalent in poorly developed tropical and subtropical regions. Filariasis is a major health concern in backward countries with the diagnosis being done only at the later stages of the disorder.
This infectious tropical disorder primarily affects three regions of the body, based on which it is classified into the following types:
Picture 1 – Filariasis
The infection originates in the lymphatic system of the body.
As the name suggests, the condition affects the subcutaneous fat tissues of the skin.
Serous cavity filariasis
In this type, the serous glands in the abdomen (that secrete a watery, albuminous fluid called serum) get affected.
This condition is highly indigenous to the tropical and subtropical regions of Asia, Africa, Central and South America, and Pacific Island nations. Approximately 120 million individuals residing in these places are affected by the parasitic nematode, and nearly 1 billion people are at the risk of getting exposed to the infection.
Like any other infection, the parasitic illness also causes fever, chills and uneasiness in the initial stage. However, an affected individual can come to know of the condition only when the other symptoms begin to appear. The clinical presentations vary according to the specific type of the disorder.
The occurrence of Elephantiasis makes this condition a leading cause of permanent sexual and physical disability worldwide. Its damaging effects include:
- Swelling of the arms, legs, ears, breasts and mucous membranes
- Abnormal hardening and thickening of the skin, and the underlying tissues
- Engorged genitals
- Increased vulnerability to infection
- Intense body pain
- Damaged kidneys
Painful swelling occurs in the deeper layers of the skin that lasts for several weeks. Its other symptoms involve:
- Elevated, red, inflamed spots called papules
- Colored and discolored macules
- Joint pain
- Lesions in the colon
- Chronic damage to the retina of the eye
Serous cavity filariasis
The type is generally asymptomatic, but few patients may develop subcutaneous filariasis-like symptoms along with itchy sensations. Development of mild abdominal pain makes the parasitic infection distinguishable from the other two forms.
The disorder is caused by a thread-like nematode or roundworm called Filariae. These nematodes are parasitic in nature and dwell in other organisms for deriving nourishment from them. The blood-feeding arthropods as well as insects such as the flies and mosquitoes are normally the primordial transmitters of the disorder. When these filariae-carrying arthropod or insect vectors feed on the human blood, the parasitic agents get into the body and cause infection. The parasitic worms invade the vital organs after entering the body of a human host. Wuchereria bancrofti, Brugia malayi, and Brugia timori are the parasitic nematodes that attack the lymphatic system. In some cases, the condition is termed bancroftian filariasis, which refers to filarial infection caused by the bancrofti worm. The nematodes that enter the subcutaneous tissues are Onchocerca volvulus, Mansonella streptocerca and Loa Loa. Infection of the serous glands is majorly caused by Mansonella perstans and Mansonella ozzardi.
Filariasis Life cycle
The complicated process begins when the adult female filarial worms viviparously give birth to numerous microfilariae after mating with the male nematodes that rapidly migrate to the dermis. These microfilariae are ingested by the blood-sucking intermediate host, which could be a mosquito, tick, mite or fly, during a normal blood meal. The microfilariae undergo a series of molts inside the vector’s body to develop into infective larvae. When the vector goes for another human blood meal, the disease-causing larvae get transmitted into the subcutaneous layer of the skin. In a span of 1 year, the larvae mature into adult worms after exhibiting the last two stages of molting. In this way, the condition progresses in accordance with the different stages of the nematode’s life cycle and causes an array of distressful symptoms.
A few medical tests that are used for the appropriate diagnosis of the disorder include:
Finger prick test
The invasive method produces a surface wound in the finger to collect a few drops of the venous blood using a capillary tube or a strip of paper. The adherence of the microfilariae to the human cells can be clearly observed when a droplet of blood is stained with Giemsa dye. The test however, needs to be conducted only at specific times of the day as various forms of the filarial worm are carried by either nocturnal or diurnal blood-feeding vectors. The lymphatic form of the condition requires collection of the infected blood only during the night as the vector responsible for causing the disease is a mosquito. The scanty microfilariae of Loa Loa in the blood can be detected only during the day as its vector called deer fly is active only between dawn and dusk. The filarial worms inhabiting the skin cannot be tested with this method.
The microfilariae can be microscopically visualized by placing a small sample of the infected skin in saline water.
The test is exclusively used for detecting the filarial antigens in the blood.
Lymph node aspiration and biopsy
A fine needle is inserted into a swollen lymph node to draw out a certain amount of fluid for culturing. The sample is incubated for a few hours and then examined for microfilariae. The technique can also be used for the removal of lymph node tissues in order to conduct a biopsy of the collected sample.
The medical imaging of the milky fluid called chylous found in the lymph vessels using procedures like CT and MRI, can reveal the presence of motile microfilariae.
The anti-filarial drugs prescribed by most physicians may either involve a combination of albendazole and ivermectin, or a combination of diethylcarbamazine (DEC) and albendazole. These medicines are capable of clearing the microfilariae circulating in the blood, but are ineffective against the adult worms. The drugs can cure the early stages of elephantiasis and prevent further multiplication of the larvae. The swollen area can be washed daily with soap water for temporary relief. Use of anti-bacterial creams over the afflicted areas can keep the secondary bacterial infections at bay and stop the swelling from getting aggravated. The swollen arms or legs can be elevated to improve the lymph flow. Surgical interventions are sometimes needed to treat the lower extremities of the body that have been seriously damaged due to the parasitic infection.
It is highly important to block the transmission of the dreadful disease in regions where the infection is rampant. It is possible to successfully eliminate the filarial infection by using a wide variety of preventive strategies like:
Picture 2 – Filariasis Image
- Use of mosquito bed nets treated with insecticides
- Topical application of insect repellants
- Avoiding disease-prone areas
- Mass annual treatment of the affected patients with anti-filarial drugs
- Frequent application of pesticides to kill the arthropod species and insects
- Proper maintenance of hygiene
Patients with mild symptoms respond well to the treatment. The advanced stages of the disorder are however, not curable. The repercussions of the condition are not life-threatening, but can cause acute pain and lead to severe disfigurement that psychologically affects the sufferers. If the swollen areas are kept free of bacterial or fungal infections then there could be a slight chance for the lymph vessels to re-establish normal circulation of the fluid. Surgical correction of the elephantiasis-affected areas has a satisfactory outlook.
Many communities shun individuals who are disfigured by Filariasis. As this disorder comes with a major social stigma, the affected patients are often rejected by their families or spouses. These severe consequences can only be avoided by preventing the rapid growth of the disorder, especially in tropical and subtropical areas of the world. Proper implementation of sanitary measures and regular use of insecticides can eliminate the root cause of the infection.