Wuchereria bancroft and schistosoma mansoni

Wuchereria bancrofti

Distribution

Wuchereria bancrofti are common in tropical and subtropical regions such as Nepal india china south America etc.

Habit and habitat:

It is a digenetic parasite. It completed its life cycle in a man and culex facing mosquito in the human body it is found in the lymph node.

Morphology

Adult worms are long hair likes, transparent and filiform in shape. Seres are separate sexual dimorphism is seen in Wuchereria Bancroft male is about 4cm in length, the tail is ventrally curved and contains two spicules female is 8 to 10 cm in length. Its tail is narrow and pointed males and females remain coiled together and can separate with very diffusivity. The life span of adult worm is about 5 to 10 years. The female is viviparous. It releases a number of first stage larva called Microfilaria larva.

• Microfilaria larva of Wuchereria Bancroft
• Microfilaria is the first larval stage of Wuchereria Bancroft
• It is surrounded by the delicate cuticular sheath. It is long and cylindrical with a striated cuticle.
• It has rudiments of various structures such as an oesophagus, nerve ring, excretory bladder, sub-cuticular cell or epidermis and somatic cells.
• It lives either in lymph or migrates into blood capillaries.
• It shows day and night periodicity. It appears in peripheral blood circulation at night and in some other organs at day.

Lifecycle

Wuchereria Bancroft is digenetic

Primary host-man

Secondary host-culex fatigue mosquito

Development of Microfilaria in mosquito

Microfilaria is the infective stage to the mosquito. When a mosquito bite an infected person microfilaria are ingested along with blood by mosquito then microfilaria reach to the stomach of mosquito. The ingested microfilaria penetrate the stomach wall and migrate into the thoracic muscles, where they moult 3 times.

In the first moult, they become sausage shape, in second moult it becomes elongated form and in final or third moult they become long slender. This third infective larva is an infective stage to human host.

Development of adult worms inside human host

When an infected mosquito bites a healthy person the 3^rd stage infective larva are deposited on the skin near the wound later, the larva enters the wound on their own they migrate through the subcutaneous tissue to the lymphatic vessels in about one year. The worm develops into mature adults and soon after copulation they release microfilaria larva.

Wuchereria Bancroft causes the disease known as Barancoftin filariasis in humans. This disease is known by another name elephantiasis.The adult worm blocks the passage of lymph nodes and lymphatic ducts. This results in the accumulation of lymph and numerous swelling and development of fibrous tissues. The adult worms tend to prefer the lymph nodes that drain the lower abdominal cavity and legs. So elephantiasis is often marked by gross disfigurations of the genitalia and legs.

Pathogenesis

Wuchereria Bancroft causes a diseases wuchereriasis or elephantiasis. Symptoms are

• The affected part becomes enlarged producing a solidity.
• Filarial fever is another common symptoms . This occurs repeatedly at intervals of weeks or months with high fever

Treatment

Infection may be reduced or eliminated by administering Hetrazan and compounds of Antimony and Arsenic. Bancroftian filariasis is diagnosed most often by demonstrating microfilaria in a blood smear.

Prophylaxis

1. Destroy of vector culex
2. Make environment clean
3. Avoid the bite of mosquito by using insect repellent or using the net.

Schistosoma Mansoni

Distribution

It is common in various parts of Africa, South America etc.

Habitat and habitat

It is digenetic in nature. It completes its lifecycle in man and freshwater snail host in man host. It is found in the mesenteric vein rectum etc.

Morphology

Schistosomiasis separate sexes. The female is larger than male. The male measures about 8 to 16 mm in length whereas the female is usually 15 to 20 mm in length in both sexes, small another large sucker, the abdomen is present. The lateral close to the oval sucker, another large sucker the acetabulum is present. The lateral margin of mail is folded ventrally to form a gynophobic canal in which the female is lodged. During their life span, theSchistosomesremain in a couple.

Eggs: Eggs is the infective stage to secondary host. Freshwater snail. A gravid worm may pass 300 eggs are oval in shape.The egg consists of fully ciliated embryo known as miracidium.

Cercaria Larva :Cercaria larva is the infective stage to man. Cercaria larva has two parts body and the forked tail. The body is covered with minute spine and consists of oral, ventral suckers tail is long of forked.

It is a digenetic parasite

Primary host-man

Secondary host-freshwater snail

Infection to snail host: The egg of Schistosoma Mansoni are passed along with faeces of infected man in the water. The egg cone in contact with the water release Miracidium. This miracidium gets mature in the water and they actively swim in search of snail host when they find snail host. They penetrate the soft tissue of Snail and reach into the Liver. Miracidium transforms into the tubular sporocysts.the cell of sporocysts again multiplies to form the second generation of sporocysts. After several weeks the sporocysts give rise to final larva known as forked tailed cercaria larva. Cercariae larva active until they come in contact with the human host.

Infection to human host

When human take the bath in the infected water, the cercaria larva penetrates the skin directly on penetrating. They cast off their tails and transformed rapidly into the schistosomula stage. This stage reaches to the liver and feed upon portal blood and develops into adult form then they lay eggs which are passed out through faeces and some cycle is replaced.

Lifecycle:

Pathogenesis:

Schistosoma Mansoni causes a disease schistosomiasis Symptoms are:

Systosomal dysentery which causes the abdominal pain and bloody diarrhea.

Inflammation occurs in the skin due to penetration of larva.

Prophylaxis

• Avoid swimming , bathing and washing in the infected water.
• Proper disposal of sewage
• Destruction of snail
• Maintain sanitation.

References:

Arvind, Keshari K. and Kamal K Adhikari. A Textbook of Biology. Vidyarthi Pustak Bhander.

Michael J.Pleczar JR, Chan E.C.S. and Noel R. Krieg. Microbiology. Tata Mc GrawHill, 1993.

Powar. and Daginawala. General Microbiology.

Rangaswami and Bagyaraj D.J. Agricultural Microbiology.