Human lymphatic filariasis is mainly caused by Wuchereria bancrofti, Brugia malayi, and Brugia timori. Bancroftian filariasis,
W. bancrofti, is responsible for 90% of lymphatic filariasis and widely distributed throughout the tropics and subtropics.
B. malayi infection is endemic in Asia such as China, Korea, India, Indonesia, Malaysia, Philippines, and Sri Lanka.
B. timori infection occurs in Indonesia (islands of Alor, Flores, and Timor).
A blood smear stained with Giemsa stain reveals infection with microfilariae of W. bancrofti.
Unless picked up by a mosquito female at feeding, the microfilariae will die in infected humans.
Microfilariae of W. bancrofti are in a protective sheath until they penetrate into the mosquito’s thoracic muscles.
Microfilaria of Wuchereria bancrofti collected by filtration with a nucleopore membrane. Giemsa stain, which does not demonstrate the sheath of this sheathed species (hematoxylin stain will stain the sheath lightly). The pores of the membrane are visible.
Blood smear showing sheathed microfilaria of Wuchereria bancrofti
Found in Central Africa
and parts of Asia, Wuchereria Bancrofti is carried by mosquitoes and caused a condition known as elephantiasis. This parasite makes its way to the lymph nodes and brings about grotesque swelling.
(© Sheldan Collins/Corbis.
Reproduced by permission.)
A random group of men infected with human W. bancrofti in southern coastal area of Tanzania. There, the primary vector is Culex pipiens breeding in pit latrines.
Elephantiasis of the left leg of a patient from India, caused by W. bancrofti. The vector in urban filariasis in India is Culex pipiens breeding in highly polluted water. Disfigurement of elephantoid limbs is irreversible. Filariasis is a chronic disease that poses a tremendous economic burden in affected countries.
Lymphadenopathy in filariasis. Lymphedema involving both lower extremities is present in a young man from the Dominican Republic.
Lymphatic filariasis currently affects 120 million people worldwide, and 40 million of these people have serious disease.
Pronounced oedema of the right leg in a woman in Porto Limon, Costa Rica.
Elephantiasis of both legs due to filariasis. Luzon, Philippines.
This image shows 3 patients with advanced stage of infection with Wuchereria bancrofti parasite also called Bancroftian filariasis. Another name for this illness is Elephantiasis
Genital enlargement of filariasis.
A and B. Moderate and marked genital enlargement due to infection with W. bancrofti is shown.
Filariasis presenting with chyluria.
Left: Lymphangiogram showing contrast within the lymphatics passing in a retrograde manner within the kidneys.
Right: Concurent IVP, showing contrast within the renal pelvis and ureters.
The milky urine (right) clears with the addition of chloroform (left). Milky-looking lymph draining from the lower limbs (chyle) passed into the urine as a result of a reverse flow in the kidney, from cortex to pelvis. This reversal is occasioned by proximal lymphatic obstruction higher in the abdomen or thorax.
Microfilaria of Brugia malayi, collected by the Knott (centrifugation) concentration technique, in 2% formalin wet preparation. Note the erythrocyte ghosts (for size comparison) and the clearly visible sheath that extends beyond the anterior and posterior ends of the microfilaria. (There are 4 sheathed species: Wuchereria bancrofti, malayi, timori, and Loa loa.)
Microfilaria of Brugia malayi (thick blood smear; hematoxylin stain). Like Wuchereria bancrofti, this species has a sheath (slightly stained in hematoxylin). In contrast with Wuchereria bancrofti, the microfilariae in this species are more tightly coiled and the nuclear column is more tightly packed, preventing the visualization of individual cells.
Filariasis. Microfilaria of Brugia malayi.
Detail from the microfilaria of Brugia malayi (see image above) showing the tapered tail, with a subterminal and a terminal nuclei (seen as swellings at the level of the arrows), separated by a gap without nuclei. This is characteristic of B. malayi.
This photomicrograph shows the inner body and cephalic space of a Brugia malayi microfilaria in a thick blood smear. B. malayi, a nematode that can inhabit the lymphatics and subcutaneous tissues in humans, is one of the causative agents for lymphatic filariasis. The vectors for this parasite are mosquito species from the genera Mansonia and Aedes.
Loasis. A microfilaria of L. loa in the peripheral blood. The microfilaria measures about 300 µm long.
Microfilariae of Loa loa (right) and Mansonella perstans (left). Patient seen in Cameroon. Thick blood smear stained with hematoxylin. Loa loa is sheathed, with a relatively dense nuclear column; its tail tapers and is frequently coiled, and nuclei extend to the end of the tail. Mansonella perstans is smaller, has no sheath, and has a blunt tail with nuclei extending to the end of the tail.
Loaisis Top: Subcutaneous worm involving the patients ezelid.
Bottom: A few seconds later, the worm has disappeared.
Threadlike adult L.loa migrating in the subconjuctival tissues.
Microfilaria of Mansonella streptocerca from a skin snip. Fixed in 2% formalin and stained with hematoxylin. The microfilaria is unsheathed, has a nearly straight body attitude, the tail is typically coiled into a “shepherd’s crook”, and terminal nuclei extend as a single row to the end of the tail.
Mansonella ozzardi, infectious agent of filariasis.
Tropical pulmonary eosinophilia. A 48-year-old indian male presented with 3 months of cough, sputum, wheeze and dyspnoea: widespread crepitations were audible at presentation. 10,3 x 10 eosinophils were present, and the filarial complement fixation test was positive. His symptoms and eosinophilia resolved after treatment with diethylcarbamazine.
The chest x-ray showing diffuse mottling and increased bronchial marking.