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