Filarioidea

File:Microfilaria of Dirofilaria immitis (Heartworms) Surrounded by Neoplastic Lymphocytes

Filarioidea is a superfamily of parasitic nematodes (roundworms) that are known to cause a group of diseases called filariasis in humans and other animals. These nematodes are transmitted to their hosts through the bites of arthropod vectors, primarily mosquitoes and black flies.

Morphology

Members of the Filarioidea superfamily are characterized by their elongated, thread-like bodies. Adult worms typically reside in the tissues or body cavities of their hosts. The morphology of these nematodes is adapted to their parasitic lifestyle, with features such as a cuticle that protects them from the host's immune system.

Life Cycle

The life cycle of filarial worms involves both a definitive host, where the adult worms reside, and an intermediate host, which is usually an arthropod vector. The cycle begins when a vector bites an infected host, ingesting microfilariae, which are the larval stage of the worm. Inside the vector, the microfilariae develop into infective larvae. When the vector bites another host, the larvae are transmitted and migrate to specific tissues, where they mature into adult worms.

Pathogenesis

Filarial infections can lead to a variety of clinical manifestations, depending on the species involved and the tissues affected. Common diseases caused by filarial worms include:

• Lymphatic filariasis, caused by Wuchereria bancrofti, Brugia malayi, and Brugia timori, which can lead to elephantiasis.
• Onchocerciasis (river blindness), caused by Onchocerca volvulus.
• Loiasis, caused by Loa loa.

Diagnosis

Diagnosis of filarial infections typically involves the detection of microfilariae in blood samples, which may require specific timing due to the nocturnal periodicity of some species. Serological tests and molecular techniques such as PCR are also used to identify infections.

Treatment

Treatment of filarial infections often involves the use of antiparasitic medications such as ivermectin, albendazole, and diethylcarbamazine. These drugs target the microfilariae and, in some cases, the adult worms. Control measures also include vector management and mass drug administration programs.

Epidemiology

Filarial infections are endemic in tropical and subtropical regions, affecting millions of people worldwide. The distribution of these diseases is closely linked to the presence of the vector species and environmental conditions that support their life cycles.

Prevention

Preventive strategies focus on reducing exposure to vectors through the use of insect repellents, bed nets, and vector control programs. Public health initiatives aim to reduce the burden of disease through education and mass drug administration.

Also see

• Nematoda
• Parasitic diseases
• Vector-borne diseases
• Lymphatic system