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Hookworms. Associated prof. Tian. Background. 1. Hookworms are the voracious blood feeders of the nematode world Hookworms parasitize more than 900 million people worldwide. 2. Ancylostomiasis is second only to ascariasis in infections by parasitic worms.

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Hookworms

Associated prof. Tian


Background

1. Hookworms are thevoracious blood feedersof the nematode world

Hookworms parasitize more than 900 million people worldwide.

2. Ancylostomiasis is second only to ascariasis in infections by parasitic worms.


3. There are two species of hookworms of medical importance

Ancylostoma duodenale: - Africa, India, China and South East Asia (Asia hookworms)

Necator americanus: - First reported in Brazil, then Texas, but since found in Africa, India and South East Asia.

(American hookworms)


Morphology

Adult:

The adult parasites are small cylindrical worms, 0.5 - 1.5cm long (Ancylostoma duodenale being slightly larger than Necator americanus ).

A.duodenale

N. americanus


Curved teeth

buccal capsule(mouth capsule)

The anterior end of the parasites are formed into a buccal capsule

Ancylostoma duodenale


cutting plates

(semilunar)

Necator

americanus



(umbrella-shaped bursa) characteristic

Copulatory bursa of male of A.duodenale


Copulatory bursa of male characteristic of N.americanus


Comparison of Hookworms characteristic

N. americanesA.duodenale

Size (lenth) about 10 mm slight larger

Shape “ S ” “ C ”

buccal capsule a pair of two pair of

cutting plates curved teeth


Eggs: characteristic

shell

Morula(4-8cell)

Size 57-76 µm by 35-47 µm 

Oval or ellipsoidal shape Thin shell, colorless. The eggs usually contain 4-8 cells in feces


A: characteristic Hookworm egg, advanced cleavage (iodine).B: Embryonated hookworm egg.


adult characteristic

Are passed in the stool

Life cycles

warm moist shaded soil

Rhabditiform larvae

egg

Intestinallumen

hatching 24-48h,

Contact host and penetrate the skin into the body

5-8days

adult

Filariform larvae

Migrant by lungs


The route of larvae migrant characteristic

Skin lungs trachea

Oesophagus stomach intestine


Life Cycle characteristic


Soil polluted with human excreta is commonly responsible for exposure to infection with human hookworms

Individuals become infected, usually by walking bare footed across contaminated soil


Penetration of the intact skin by filariform larvae of hookworm, on coming in contact with fecal polluted soil.


A hookworm, on coming in contact with fecal polluted soil., B: Hookworm rhabditiform larva (wet preparation).

A, B: Hookworm filariform larva (wet preparation).


A hookworm, on coming in contact with fecal polluted soil., B, C: Hookworm filariform larva (A and B, wet preparations; C, iodine). Larva tail is depicted in Figures B and C.


Pathogenesis and clinical manifestation hookworm, on coming in contact with fecal polluted soil.

  • Cutaneous or invasive phase:

  • by hookworm larvae

  • Dermatitis(ground itch):

  • irritation and itching



(2) Pulmonary phase: photographby hookworm larvae

Local haemorrhaging, pneumonitis

Symptoms in respiratory system

cause a cough and a sore throat.


(3) Intestinal phase: photographBy adult worm

A)the intestinal mucosa are damaged

B)Anemia:

Protein and iron in-take is insufficient

Blood loss

Hypochromic microcytic anemia


Blood loss photograph

a)Ingestion of the blood by the worm

b)Seepage of the blood around the site of attachment of the worm

c)Oozing of the blood from the burrowed site previously attached by the worm

d)Anticoagulants


This is a photograph of the hookworm's appearance against the lining of the intestine (intestinal mucosa).


Clinical features of hookworm disease the lining of the intestine (intestinal mucosa).

Site

Symptoms

Pathogenesis

Dermal

Local erythema, macules, papules (ground itch)

Cutaneous invasion and subcutaneous migration of larva

Pulmonary

Bronchitis, pneumonitis and, sometimes, eosinophilia

Migration of larvae through lung, bronchi, and trachea

Gastro- intestinal

Anorexia, epigastric pain and gastro-intestinal hemorrhage

Attachment of adult worms and injury to upper intestinal mucosa

Hematologic

Iron deficiency, anemia, hypoproteinemia, edema, cardiac failure

Intestinal blood loss


Diagnosis the lining of the intestine (intestinal mucosa).

Laboratory diagnosis

It includes parasitic diagnosis and immunodiagnosis

l) Microscopy Direct smear examination of feces is adequate to detect moderate or severe infections.


2) Concentration Concentration of stool by formalin-ether or simple salt floatation stool is essential to detect light hookworm infection.

3) Third-stage larvae in the fecal culture


Epidemiology or simple

Distribution

Hookworm diseases is widely epidemic parasitic disease in the world. Hookworm distribute these areas between northern latitude 45○ to southern latitude 30○. A.duodenale is chiefly found in tropic areas and subtropic areas, N.americanus is commonly found in warm zone.




Reservoir, source and transimission or simple

of infection

Human is the only reservoir of infection

Human feces is the only source of infection


Prevention and control or simple

l ) Sanitary disposal of human feces;

2) Treatment of infected persons;

3) Health education with improved use of sanitary latrines and use of foot wears


Treatment of hookworm infection consists of or simple

a) treatment of worm infection by anthelmintics such as mebendazole;

b)treatment of anemia.



Trichinosis is related to the quality of pork and consumption of poorly cooked meat. Autopsy surveys indicate about 2 percent of the population is infected.


female consumption of poorly cooked meat. Autopsy surveys indicate about 2 percent of the population is infected.

Morphology

Adult worm The adult worms are very small and slender with slightly tapered anterior ends, white and just to the naked eye. female 2.2 mm in length, males 1.2 mm;

male


male consumption of poorly cooked meat. Autopsy surveys indicate about 2 percent of the population is infected.

papilla


pharynx consumption of poorly cooked meat. Autopsy surveys indicate about 2 percent of the population is infected.

female

Its pharynx is one third or half of worm body long, and posterior part of pharynx consists of a column of cells called of stichocytes.

juveniles


Cyst (larvae) consumption of poorly cooked meat. Autopsy surveys indicate about 2 percent of the population is infected.

The cyst are found in skeletal muscle commonly, its size is about 0.25~0.5


Larvae in Muscle Section consumption of poorly cooked meat. Autopsy surveys indicate about 2 percent of the population is infected.

Larvae in Muscle Press


Larvae of consumption of poorly cooked meat. Autopsy surveys indicate about 2 percent of the population is infected. Trichinella, freed from their cysts, typically coiled; length: 0.8 to 1.0 mm.


Trichinella spiralis: consumption of poorly cooked meat. Autopsy surveys indicate about 2 percent of the population is infected. Electron microscopy


Life cycles consumption of poorly cooked meat. Autopsy surveys indicate about 2 percent of the population is infected.

Into skeletal via bloodstream

dischargeing

adult

cycst

larvae

( 1 month)

Intestine of the humans、pigs、rats、cats、dogs

Swallowed by

another host

adult

larvae


cyst consumption of poorly cooked meat. Autopsy surveys indicate about 2 percent of the population is infected.

cyst

adult

lavae


Trichinellosis is acquired by ingesting meat containing cysts (encysted larvae) of Trichinella.

After exposure to gastric acid and pepsin, the larvae are released

from the cysts and invade the small bowel mucosa where they develop into adult worms

(life span in the small bowel: 4 weeks).


After 1 week, the females release larvae cysts (encysted larvae) of

that migrate to the striated muscles where they encyst


Life Cycle cysts (encysted larvae) of

< Infection occurs by ingesting encysted larvae in undercooked meat.

< Larvae penetrate the intestinal wall and move to muscle tissue where they encyst in individual cells (nurse cells).  Active muscles, such as the diaphragm and tongue, often have the greatest numbers of larvae.

< Adults attach to the intestinal mucosa and being to release larvae in one week.  The adults live for about 4 weeks and may release more than 1000 larvae.


Pathogenesis and clinical manifestation cysts (encysted larvae) of

The process of pathological change can be divided three phases.

1)Invade phase : intestinal inflammation

intestinal inflammation

For invading of larvae and adult worms, the wall of intestine is damaged

Gastrointestinal signs


2) Migratory phase : toxic and allergic cysts (encysted larvae) of

severe systemic disease

allergic phenomena such as edema, pneumonitis, and pleural transudate

3) Encystation of the larvae and tissue

repair formation of cyst


clinical manifestation cysts (encysted larvae) of (Symptoms)

Infection with Trichinella spiralis may be asymptomatic, especially in light infections.  Adults in the intestine may cause diarrhea, abdominal pain, and vomiting.  Larvae moving into the tissues may cause facial swelling, fever, muscle pain, splinter hemorrages (under fingernails) or rashes.

Heavy infections may lead to heart problems or central nervous system involvement.  Large numbers of larvae in other muscles may lead to soreness and weakness which often lessens over time.


Diagnosis cysts (encysted larvae) of

  • clinical manifestations with a history of ingesting meat that may contain larvae;

  • immunodiagnosis;

  • muscle biopsy.

  • The definitive diagnosis is made by demonstration of free or encapsulated Trichinella larvae in the skeletal muscles obtained either in biopsy or at autopsy.


Epidemiology cysts (encysted larvae) of


Trichinella spiralis cysts (encysted larvae) of (T-1) (green) is the most common member of the genus. The world distribution as depicted is almost certainly an under-representation


Prevention and control cysts (encysted larvae) of

avoidance of eating raw or undercooked pork and meat of other wild animals; and avoidance of feeding raw garbage to pigs will prevent transmission of infection to man.