Nematoda:Nematoda:

The nematode belong to the Class NeThe nematode belong to the Class Nematodamatoda , Parasitic nematodes that infParasitic nematodes that infect humans have about l0 species, inclect humans have about l0 species, including Ascaris lumbricoides , hookworuding Ascaris lumbricoides , hookworm , filarial and Trichinella spiralis.m , filarial and Trichinella spiralis.

Structure of the adult :Structure of the adult :

1.Nematodes are generally elongate, cylindrical, and tapered at both ends.

2. The basic body design is a tube within a tube, male are also usually smaller than females.

Structure of egg : Eggs of parasitic nematodes ordinarily con

sist of three layers :• A) Embryo member: consist of lipid prote

in;• B) Chitonous layer : consist of chitonous a

nd protein, and Process the function of resisting the mechanic pression,

• C) Lipid layer/ascaroside : consist of lipid protein and ascaroside, and process the function of regulating.

The character of life cycle:

1 、 The basic process of development :egg, larva and adult. (growth occurs with molting )

2.The type of life cycle:2.The type of life cycle:

（ 1 ） Some parasitic nematodes have simple life cycle, consisting of egg, larva, and adult worm, these nematodes are considered as direct development type of nematodes or soil-transmission nematodes, such as hookworm.

（ 1 ） Some parasitic nematodes have simple life cycle, consisting of egg, larva, and adult worm, these nematodes are considered as direct development type of nematodes or soil-transmission nematodes, such as hookworm.

(2) Some parasitic nematodes need intermediate host to complete the life cycle, these nematodes are called vector transmission nematodes or bio-source nematodes , such as filaria .

Ascaris Lumbricoides

Ascaris is the most common and largest nematode parasite of humans, infecting an estimated 1.47 billion individuals. Pathology can result from pneumonia caused by the worm's migration through the

lungs, blocking of the gastrointestinal track or the bile or pancreatic duct. Ascaris lumbricoides is physical

ly indistinguishable from Ascaris suum.

size:

20~35cm×3~6mm

15~31cm×2~4mm

Adult :

Morphology

adultadult

2.Head :

lipslips

toothtooth

lipslips

toothtooth

The tail of male : The tail of male : spiculesspicules

spiculesspicules

3 、 reproductive system3 、 reproductive system

Protein membranceProtein membrance

shellshell

EmbryoEmbryo cell

gapgap

Fertilized eggFertilized egg

Egg

fertilized egg

fertilizedfertilized eggegg

Yolk granuleYolk granule

unfertilizedunfertilized eggegg

Embryonated eggEmbryonated egg

larvaelarvae

Life cycle:

Larvae must migrate to lungs:Larvae must migrate to lungs:

Small Small intestineintestine

Heart Heart bronchusbronchus

tracheatrachea throatthroatstomachstomach

Moult twiceMoult twice

1w1wswallowedswallowed

Penetrate intestinal

wallliver lung

Small Small intestineintestine

3 . The female parasite is highly prolific .

1. have a direct lifecycle, with no intermediate hosts .

2. Larvae must migrate to lungs.

The character of life cycle ：The character of life cycle ：

Pathogenesis and clinical manifestations:Pathogenesis and clinical manifestations:

Larvae:Larvae:

1 、 Loeffer’s syndrome:

large numbers of larvae are migrating through the lungs simultaneously .this may give rise to a severe haemorrhagic pneumonia.

lead to breathing difficulties, fever etc.

2、 larvae may migrate to other organ:brain,liver,kidney

and thyroid gland etc.

Adult :Adult :

1. Intaking nutrients and negatively affectthe absorption:

2.Allergy: urticaria ,itch and angioneurotic edema

3.Complication of ascariasis:

1)mechanical blockage of the intestine:

2)migrate to the bile duct , migrate to the

appendix , or through the intestinal

Wall:

Ascaris （ left 1 、 2 、3 ）

Ascaris in bile ductAscaris in bile duct

Ascaris block the intestineAscaris block the intestine

Ascaris through the intestinal wallAscaris through the intestinal wall

Ascariasis patient

Diagnosis: Diagnosis:

1.Microscopic exam :egg1.Microscopic exam :egg

2. Chest radiographs for Loffler's syndrome :

EpidemiologyEpidemiology

Distribution: Ascaris lumbricoides is widely distributed in tropical and subtropical areas, especially in the developing countries of S. America where poor hygiene and inadequate sanitation facilities prevail., Africa and Asia. It is estimated that there are more than 1 billion infections at any given time.

Ascaris lumbricoides is widely distributed in tropical and subtropical areas, especially in the developing countries of S. America where poor hygiene and inadequate sanitation facilities prevail., Africa and Asia. It is estimated that there are more than 1 billion infections at any given time.

Distribution of china

Epidemiologic factors:

（ 1 ） The life cycle of ascaris involves no intermediate host. A female worm has a high reproductive capacity of 26 million eggs, and an average daily output 200,000:

（ 2 ） the egg process the strong ability to resist environmental conditions:

The promiscuous defecation or night soil used for fertilization provides the source of soil and vegetable contamination. Domestic animals such as fowls and dogs may act as mechanical carriers of the ova.

(3) Human feces is used as fertilizer:

ProphylaxisProphylaxis

1.Good sanitation :a.Wash hands with soap and water after using the toilet and before handling food. especially when traveling in developing countries. b.Wash and peel all raw vegetables and fruits before eating. Avoid food that may be contaminated with feces.c. Clean, sanitary toilet facilities must be provided .

1.Good sanitation :a.Wash hands with soap and water after using the toilet and before handling food. especially when traveling in developing countries. b.Wash and peel all raw vegetables and fruits before eating. Avoid food that may be contaminated with feces.c. Clean, sanitary toilet facilities must be provided .

2.The drugs of choice for treatment :

albendazole, mebendazole, pyrantel pamoate and Fructus guisgualis tab. of Melis toosendan etc.

Trichuris trichiura

(Whipworms)

Morphology:

adult of whipworms in intestine

2 、 Egg :

Life cycle:Like that of ascaris lumbricoides:

1. Site of inhabitation:cecum

2. Larvae may not migrate to lungs

Pathogenesis and clinical manifestations:

when the worm burden exceeds 100 worms . It causes chronic hemorrhage/bleeding resulting in anaemia. In addition there are often secondary bacterial infections which result in colitis, proctitis and in rare cases, can result in the prolapse of the rectum.

Rectal prolapse

Diagnosis ,epidemiology and prophylaxis:

Like that of ascaris lumbricoides

Distribution of whipworms in china

Enterobius Vermicularis

(The human pinworms)

Morphology

1 、 Adult

Bulbed oesophgus

anterior end

anterior end

2 、 Egg

eggshell

larvae

Egg

Pathogenesis and clinical manifestations

1. perianal pruritus(especially at night):

2. pinworms migrate through the genital tract of females to the peritoneal cavity .

• 1.Microscopic identification of egg:

• 2. found adult worm in the perianal area :

Laboratory Diagnosis:

Eggs are found in feces in only about 5% of cases

The worm has a cosmopolitan distribution. Enterobiasis is more common in urban than in rural areas. and is more common in children (escpecially in

nursery or kindergarden)

Mode of infection:

Epidemiology

1 、 hand-to mouth transmission :

2 、 Inhalation of air borne egg in dust:

3 、 retroinfection through the anus:

Epidemic factor:

1.The parasite have simple life cycle:2.The egg can prevent injury of surrounding:3.The children have bad sanitation :

Distribution of age

1 、 good sanitation ：

2 、 The drug of choice ： albendazole

menbendazole

Prophylaxis: