Brugia malayi - Host Immunity, Prognosis, Epidemiology, Reservoir, Transmission

Host Immunity of Brugia malayi

The host immunity of Brugia malayi involves the suppression of both humoral immunity and cell-mediated immunity. This immunosuppression is seen in all microfilaraemia patients and is specific to filarial antigens.

Cell-mediated immunity

• occurs in chronic filariasis

• are filarial antigen-specific suppression of cell-mediated immunity

• caused by lymphocyte suppressors, suppressive adherent cells, and incompletely defined serum suppressor factors

Humoral immunity

• host humoral immunity suppression occurs in all forms of lymphatic filariasis (except microfilaraemia)

• characterized by hypoalbuminemia, an elevated level of specific antibody responses

• microfilariae and adult Brugia malayi-specific antibodies do not provide immunity against the parasite

• also do not prevent reinfection

• in chronic filariasis, total and specific levels of IgE antibodies are found to be elevated

• although basophils and mast cell levels are slightly elevated, allergic reactions on exposure to filarial antigens do not occur

• in patients with microfilaraemia caused by Brugia malayi, the antibody response is completely absent

On the basis of immunological determinants, clinical filariasis can be of numerous types:

Asymptomatic microfilaraemia

• absence of cell-mediated immunity

• presence of limited specific serum antibodies to both adult Brugia malayi parasites and microfilariae

• hyperresponsive to specific filarial antigens

Lymphatic filariasis

• both host cell-mediated immunity and humoral immunity response are higher than in cases of asymptomatic microfilaraemia

• increased host response in lymphatic filariasis is responsible for the removal of microfilariae from blood and induction of local inflammatory reactions which in turn produce lymphatic damage and obstructive lesions

Endemic normal

In endemic normal patients infected with Brugia malayi, both humoral and cell-mediated immunity is high.

Epidemiology of Brugia malayi

Epidemiological studies of Brugia malayi have shown that nocturnal periodic Brugia malayi is worldwide in distribution than the sub-periodic Brugia malayi.

Nocturnal periodic Brugia malayi is found in SriLanka, Philippines, North Vietnam, China, Japan, South Korea, and Southern Thailand while sub-periodic Brugia malayi is common in Malaysia, Sumatra, Thailand Kalimantan islands of Indonesia.

Reservoir, Source of Brugia malayi

For nocturnal periodic Brugia malayi, man is the only host, and thus humans are the main source and reservoir for the filarial nematode parasite.

For sub-periodic Brugia malayi (also a zoonotic disease), definitive hosts such as humans, leaf monkeys (Presbytis spp.), macaques (Macacca spp.), and cats are the source and reservoir for the filarial nematode parasite.

Transmission of Brugia malayi

Transmission of Brugia malayi occurs through the insect vector i.e. mosquitoes onto a healthy person.

• nocturnal periodic Brugia malayi transmitted by Anopheles and Mansonia mosquitoes

• sub periodic Brugia malayi transmitted by Mansonia and Coquilletcidia

Complications of Brugia malayi

Brugia malayi infection is complicated by secondary bacterial and fungal infections on the overlying skin of elephantiasis (leg or arm).

Prognosis of Brugia malayi

If the filarial nematode parasitic infection is diagnosed and treated early, the prognosis of Brugia malayi is good.

Treatment of Brugia malayi

Drugs of choice for the treatment of Brugia malayi include:

• DEC (diethylcarbamazine) for lymphatic filariasis

  * kills mainly the microfilariae and to some extent the adult Brugia malayi but is not effective against third and fourth-stage larvae

  * also reduces changes to developing chronic filariasis

  * a second course can be repeated to kill adults

  * side effects includes myalgia, headache, chill, arthralgia, fever

  * side effect is due to massive killing of microfilaria

• Ivermectin for onchocerciasis

• levamisole

• mebendazole

• centprazine

Prevention, Control of Brugia malayi

The prevention and control of Brugia malayi infection are based on

• successful treatment of infected individuals

• reduction of transmission by controlling mosquito population especially around housing by eliminating breeding places, spraying oils and chemicals in breeding sites

• using mosquito nets while sleeping, and netted windows in endemic areas

• use of biological control agents such as bacteria (e.g. Bacillus sphaericus strain 1593, Bacillus thuringiensis serotype 11-14), fish (e.g. Poecilia reticulata molliensis)

• wearing protective clothing

• use of mosquito repellants

• chemoprophylaxis