Brugia malayi

Scientific classification

Kingdom: AnimaliaPhylum: NematodaClass: SecernenteaOrder: SpiruridaFamily: FilariidaeGenus: BrugiaSpecies: B. malayi

Brugia malayi • is a roundworm nematode, one of the three

causative agents of lymphatic filariasis in humans.

• Lymphatic filariasis, also known as elephantiasis, is a condition characterized by swelling of the lower limbs.

• The two other filarial causes of lymphatic filariasis are Wuchereria bancrofti and Brugia timori, which differ from Brugia malayi morphologically, symptomatically, and in geographical extent

Geographical distribution• B. malayi infects 13 million people in south and

southeast Asia and is responsible for nearly 10% of the world’s total cases of lymphatic filariasis

• B. malayi infection is endemic or potentially endemic in 16 countries, where it is most common in southern China and India, but also occurs in Indonesia, Thailand, Vietnam, Malaysia, the Philippines, and South Korea

Morphology• Female adult worms measures between

43-55 mm in length by 130-170 um in width.

• Male adult worms measures between 13-23 mm in length by 70-80 um in width.

Microfilariae• B. malayi microfilariae measures 177-230 um

in length and 5-7 um in width and have a round anterior end and a pointed posterior end.

• The sheath is actually the egg shell, a thin layer that surrounds the egg shell as the microfilariae circulates in the bloodstream.

• The microfilariae retain the sheath until it is digested in the mosquito midgut

Adult

Sections of adult Brugia sp. From a lymph node, stained with hematoxylin and eosin.

Microfilariae

Posterior end of B. malayi microfilariae – note the two distinctive terminal nuclei

Life Cycle• The typical vector for Brugia malayi filariasis

are mosquito species from genera Mansonia and Aedes.

Life cycle

Symptoms • Asymptomatic Phase: Upon initial

infection no symptoms may be present as microfilariae mature.

• B. Malayi is one of the causative agents of lymphatic filariasis, a condition marked by infection and swelling of the lymphatic system.

• The disease is primarily caused by the presence of worms in the lymphatic vessels and the resulting host response.

• Signs of infection are typically consistent with those seen in bancroftian filariasis – fever, lymphadenitis, lymphangitis, lymphedema, and secondary bacterial infection

* Lymphadenitis cause swelling of the lymph nodes that may occur prior to maturation.

* Lymphangitis• Inflammation of the lymphatic vessels

usually after maturation. • The affected lymphatic vessel becomes

distended and tender, and the overlying skin becomes erythemous and hot. Abscess formation and ulceration of the affected lymph nodes occasionally occurs during B. malayi infection

Lymphadenitis

Lymphagitis

*Lymphedema (elephantiasis)• It is the enlargement of the limbs.• Consistent irritation of lymphatic vessels

leading to blockages caused by dead adult worms, inflammatory fibrosis, or granulomatous reactions.

• Elephantiasis resulting from B. malayi infection typically affects the lower extremities of the legs and arms.

* Secondary bacteria infections• lymph node failure caused by extended

overstimulation

Diagnosis• The standard method for diagnosing active

infection is the identification of microfilariae in a blood smear by microscopic examination.

• The microfilariae that cause lymphatic filariasis circulate in the blood at night (called nocturnal periodicity).

• Blood collection should be done at night to coincide with the appearance of the microfilariae, and a thick smear should be made and stained with Giemsa or hematoxylin and eosin.

• Serologic techniques provide an alternative to microscopic detection of microfilariae for the diagnosis of lymphatic filariasis.

• Patients with active filarial infection typically have elevated levels of antifilarial IgG4 in the blood and these can be detected using routine assays.

Treatment• Diethylcarbamazine (DEC)- is the drug of

choice • Doxycycline (200mg/day for 4-6 weeks). • In patients with Elephantiasis, surgical

procedures are required as chemotheraphy cannot reverse the fibrotic changes.

• Levamisole hydrochloride- also been used for the treatment of W. bancrofti, B. malayi and tropical pulmonary eosinophilia.

• Ivermectin- shown great promise in the treatment of filariasis and eosinophic-lung.

Prevention and ControlThe best way to prevent lymphatic filariasis is to

avoid mosquito bites. The mosquitoes that carry the microscopic worms

usually bite between the hours of dusk and dawn. If you live in an area with lymphatic filariasis: • at night– sleep in an air-conditioned room or– sleep under a mosquito net

• between dusk and dawn– wear long sleeves and trousers and– use mosquito repellent on exposed skin.

The end