Hymenolepis nana（微小膜壳绦虫）

• 短膜壳绦虫• Adult parasite in intestine of mouse

and man, cause hymenolepiasis nana （微小膜壳绦虫病）

I. Morphology

Adult mature segment

gravid segment

scolex

• Egg

II. Life history

1. Direct infect and develop

gravid segment swallowed hexacanth penetrates

eggs by man （六钩蚴） in intestinal

(in faeces) villus

re-enters the

cysticercoid adult

lumen of the

digestive tract

2. Auto-infect

gravid segment direct hexacanth

egg hatching

(in intestine) cysticercoid

（似囊尾蚴）

adult

3. Development by intermediate host

gravid segment swallowed by hexacanth

egg intermediate host (in fleas blood

(in faeces) eg. Fleas canal)

cysticercoid swallowed adult

(in fleas blood by man (in intestine

tract) of man)

Notes:

1. Infective stage: egg, cysticercoid

2. Infective method: by eatting

3. Intermediate host: fleas （印鼠客蚤、致痒蚤、犬栉首蚤） and me

alworms （面粉甲虫）

III. Pathogenicity

• Mechanical injure （机械性损伤） by sucker, hook

• Poisonous action （毒性作用） by secreting of worm

IV. Diagnosis

• Faeces examination for eggs and gravid segment

V. Epidemiology

1. Geographical distribution : cosmopolitan

2. Man infected by swallowing the egg from food, finger, water contaminated or by swallowing intermediate host contain cysticercoid

auto-infect when immunosuppression

3. Rat and mice are very important reservoir

VI. Prevention and treatment

• Treat the patient

• Improve the food and environment sanitation

• Extinguish rat

Echinococcus granulosus（细粒棘球绦虫）

Character:1. Adult lie attached to the mucous membrane of

the small intestine of final host

2. Eggs in faeces of final hosts are infective to man and to herbivorous （草食性动物） hosts

3. The larval form is a hydatid cyst which is common in many species of herbivorous animals ’s liver and lungs

I. Morphological characters

• Adult: very small, have a head and 3 segments

• Egg: indistinguishable from the Taenia eggs

Hydatid cyst

II. Life history adult

protoscolex final host

egg

hydatid cyst

intermediate host

onchosphere ingested

circulation by man

hydatid cyst onchosphere

Notes:

1. Infective stage to man is egg;

2. The intermediate host are herbivorous (sheep, cattle ect.) and man;

3. The final host is carnivores (dog, wolves ect.);

4. Hydatid cyst can be found in liver (69.9%), lung (19.3%), abdomen canal (3%), brain (0.4%), spleen (0.4%), kidney (0.3%) and other organs of man.

III. Pathogenicity

• This depends on the location and the number of hydatid cyst. The early stage of infection is asymptomatic.

• As the cyst enlarges, symptoms of a space-occupying lesion develop.

Symptoms：

1. Local compression and stimulation symptom

2. Nodules

3. Allergic reactions and sometimes anaphylactic shock may occur if the cyst raptures.

4. Secondary infect

IV. Diagnosis

• X-ray, B ultrasonic, CT, autopsy, immunological test

• Note: diagnostic puncture of a hydatid cyst is a very dangerous

V. Epidemiology

1. Geographical distribution: cosmopolitan

2. Epidemic factors:

(1) egg contaminated to environment;

(2) close contact between man, domestic animal and environment;

(3) internal organs of sick animal are fed to dog or discarded everywhere.

VI. Prevention and Treatment

• Treat the patient

• Health conduct and education

• Regular vermifugal （驱虫） treatment to domestic animal

• Strength management to massacre （屠宰） of cattle and sheep, strength quarantine （检疫） of hygiene.

Echinococcus multilocularis（多房棘球绦虫）

Notes:

1. Adult, not in man, but in foxes, wolves and less commonly in cats and dogs. The worms lie attached to the mucous membrane of the small intestine as in the case of E. granulosus.

2. The eggs are indistinguishable from those of E. granulosus. They are passed in the faeces of the final host, either free or in the gravid segment, and are infective to small rodents.

3. The larval form, the alveolar hydatid cyst （泡球蚴） , is found in a number of small rodents, and in man.

4. Man becomes infected by eating raw fruit or vegetables contaminated by the faeces of infected final hosts, or by handling them.

5. The lesion of alveolar hydatid cyst like a slow-growing malignant tumour, with poorly defined margins and it may extend into blood vessels and become dispersed into distant parts of the body. Over 90% of these cysts occur in the liver.