Introduction

Filariasis is a disease caused by parasites (Roundworm), with mosquitoes being its vectors. This disease occurs mostly in tropical and subtropical areas such as Africa, Asia and the Caribbean. It can be caused by three types of roundworms, including: Brugia timori, Brugia malayi, and Wuchereria bancrofti. The five species of mosquitoes which are involved in the transmissions include Anopheles, Ades, Culex, Ochlerotatus, and Mansonia.¹ The lifecycle of this disease involves both the mosquito and the human host.

The lymphatic system is part of the circulatory system and plays an important role in the immunity of the body. It comprises the lymph nodes, the lymph, the lymph vessels, etc. This system allows extracellular fluid drainage and can be found in almost all parts of the body.

Pathophysiology

The life cycle of these parasites begins in the mosquitoes. The vector mosquitoes take in the larvae, which then mature to microfilariae during a blood meal from an infected host and transfer to another host through the site of the mosquito bite. The microfilariae move to the lymphatic system of the host, where they cause the disease and perpetuate the cycle.²

The presence of microfilariae in the blood will trigger an immune response, leading to inflammation. Persistent inflammation will lead to acute or chronic damage to the lymphatic system.

Effect on the lymphatic system

Some individuals in endemic places do not show any effect of this disease despite having a high degree of exposure to the parasite. They remain asymptomatic for months or years and test positive for microfilaria.

Lymphatic filariasis affects the body via acute inflammatory responses, chronic lymphatic damage, pathological changes and secondary complications.

Acute inflammatory responses

This is an immediate response to infections in the body. This response can be harmful if not regulated. In lymphatic filariasis, the acute response includes lymphangitis and lymphadenitis. In males, it could also lead to orchitis and epididymitis.

Chronic lymphatic damage

This occurs 10-15 years after the first episode of attack, where there is an obstruction of the lymphatic vessel causing permanent lymphatic damage.

This chronic damage will lead to;

• Lymphedema: This usually affects 30% of the population, frequently affecting the lower extremities ( legs).
• Elephantiasis
• hydrocele
• Chyluria
• Tropical pulmonary eosinophilia (TPE): This occurs as a result of hyper responsiveness of the immune system toward microfilaria in the pulmonary capillaries, which could lead to wheezing, fever, and productive cough³

This disease could also lead to some pathology changes such as:

• Fibrosis of the lymphatic tissues
• Lymphatic vessel dysfunction and dilation.

These pathological changes could then lead to some secondary complications that affect the skin and cause recurrent bacterial infections.

Clinical manifestation

• Fever
• Wheezing, dry cough
• Genital swelling
• Bacterial infection leading to scarred skin
• Shortness of breath 

Diagnosis

• Physical examination: This is done by determining the history to which the individual had been exposed to endemic areas. Clinical evaluation of the Limb is carried out to determine if there is any thickening of the skin as a result of recurrent episodes of fever, chills, back pain, etc
• Microscopic Examination: it involves
• Blood smear of microfilaria: This is usually obtained at night because that is the peak of microfilariae circulation in the blood (10 pm - 2 am). This is important to quantify the microfilaria load⁴
• Antigen detection test: immunochromatographic Test (ICT) and enzyme-linked immunosorbent assay (ELISA) are used in antigen detection
• Ultrasound of the lymphatic vessel is important in visualizing adult worms

Treatment

The treatment involves both pharmacological and preventive measures.

• Pharmacological intervention: This requires the use of drugs such as Diethylcarbamazine(DEC), ivermectin, Doxycycline and Albendazole
• Management of lymphedema:
  • Use of elastic crepe bandage for the wound
  • Always keep the limb elevated at bedtime
  • Regular light  massage and exercise on the affected  limb
  • Heat therapy is also important

Prevention and control

1. Vector control: important to reduce the mosquito population in the environment and the transmission of the disease. Vector control measures include:
   • Use of chemicals
   • Maintenance of septic tanks and sewage
   • Use of mosquito nets and repellants
2. Mass drug administration (MDA): This is also a preventive method because an annual dose of the drug is administered to the individuals living in an endemic region
3. Public Awareness: this involves educating the population of the effect of microfilariae in the blood, preventive measures and personal hygiene⁵

Summary

Filariasis is a disease caused by roundworms, and its transmission occurs via mosquitoes as their vector and the human lymphatic system as their host.

It affects human beings in two episodes with acute and chronic phases presenting with specific clinical manifestations.

The treatment of this disease can be done with drugs and/or surgery, but preventive measures are important for the safety of other individuals living in an endemic area.

FAQs

What is the main cause of filariasis?

Filariasis is caused by parasites ( roundworms): Brugia timori, Brugia malayi, and Wuchereria bancrofti.

Can filariasis be cured?

It can only be managed with drugs and surgery, depending on its severity.

What is the treatment for filaria?

Diethylcarbamazine ( DEC), ivermectin and albendazole.

How can we detect filariasis?

It can be detected in the blood by a blood smear test and a serological examination 

How can we avoid filariasis?

Both by controlling the vector population and ensuring mass drug administration (MDA).

Do mosquitoes cause filariasis?

Mosquitoes are the vector responsible for the transmission of this disease.