Difference between W.Bancrofti and B.Malayi

The upcoming discussion will update you about the difference between W.Bancrofti and B.Malayi.

Difference # W. Bancrofti:

Adult worms are creamy white, filiform and have cylindrical body with tapering ends. Posterior end of male is sharply curved ventrally bearing two unequal copulatory spicules.

The female has narrow and abruptly pointed tail end.

Microfilariae are 225 to 300 µm long and 10 µm in diameter.

A hyaline sheath projects slightly beyond the extremities of the embryo and this sheath repre­sents the chorionic envelope.

Cuticula is lined by subcuticular cells.

The anterior end is blunt bearing a distinct cepha­lic space which is devoid of nuclei. A nerve ring is seen near the anterior end, behind which at some distance is excretory pore. Near the posterior end is the anal spot. These areas are also devoid of nuclei. But the rest of the body contains nuclei of cells which are used as definite land marks for the identification of this species.

Habitat:

Adult worms are found in the lymphatic vessels and lymph nodes of man only.

Zoonotic connexions:

Not zoonotic.

Distribution:

They are largely confined to the tropical and subtropical parts of South China, India, japan, Pacific Islands, West Indies, West and Central Africa and South America. In India it is distributed along the Sea coast, Rajasthan, U.P., Punjab, Delhi and along the bank of big rivers.

Life history: In mosquito:

Larval development of microfilaria in the mosquito varies from 10 to 20 days or more, depending however on the atmos­pheric temperature, humidity and also to a certain extent on the species of the mosquito. Ingested microfilaria discards sheath, penetrates the gut wall within an hour or two and migrates to the thoracic muscles. In the thoracic muscles the microfilariae rest and begin to grow.

1st stage:

Sausage-shaped larva measures 125-250 µm in length and 20-30 µm in diameter. It bears a short tail with spike and a rudimentary digestive tract.

2nd stage:

The 2nd stage larva undergoes moulting for two times and grows to the size 225-330 µmx 15-30 µm.

3rd stage:

On the 10th or 11th day the metamor­phosis becomes complete. In the 3rd the tail atro­phies to a mere stump and the digestive system, body cavity and genital organs are fully deve­loped. Subterminal caudal papillae are three in number. The 3rd stage larva measures 1,500-2,000 µm in length by 18-23 µn in breadth.

Mosquito vector:

Culex pipiens (usually) and Aedes polynesiensis.

In man:

Third stage larva gets dropped on the skin near the site of puncture. This larval stage pene­trates skin, reaches the lymphatic channel, settles down at some spots (inguinal, scrotal or abdomi­nal lymphatics) and begins to grow into adult form. It becomes sexually matured between 5 to 18 months.

The male fertilizes the female and the gravid female gives birth to microfilariae, which ulti­mately reach peripheral circulation to be taken up by the mosquito vector.

Periodicity:

Microfilariae appear in peripheral blood only during the night usually between 10 p.m. and 4 a.m. At other time, microfilariae remain in deeper parts of circulation in body organs as in the case of Culex pipiens.

Difference # B. Malayi:

Male is more or less similar.

Female is indistinguishable from that of W. ban­crofti.

Microfilariae are about 230µm long and 6 µm in diameter.

Sheathed and with kinks in surface unlike W. ban­crofti has a smooth surface.

The cephalic space is longer. Double styles are present at the anterior end. The nuclei are blurred, hence counting is difficult. Tail end is not free from nuclei. There are two discrete nuclei—one at the extreme tip of the tail and the other is found midway between the tip and the posterior column of nuclei.

Adult worm is found in the lymphatic system like W. bancrofti.

Similar micofilariae found in man, monkeys, the civet cat and the cat in India and Malaysia. Presbytes monkeys may be the reservoir. The periodic form occurs in India, Sri Lanka, Thailand, Malaysia, Korea and Japan but the sub-periodic form occurs in the east coast of Malaysia, Thailand and the Philippines.

Larval development in mosquito is completed within 6-8 days.

Details of development are same as that of W. ban­crofti, except that the caudal papillae of the third stage in the mosquito are two in number.

3rd stage larva enters into the proboscis of mos­quito by 6-8 days. This is the infective stage.

  Anopheles barbirostris, Mansonia annulifera, M. indi- ana, M. uniformis.

  In man the life stages are similar as that of W. ban­crofti.

Microfilariae appear in peripheral blood at night time in the case of Anopheles barbirostris.