عين النسر
المدير العام
رقم العضوية : 1
 عدد المساهمات : 2247
نقاط : 15980
تاريخ التسجيل : 25/02/2010
 |  موضوع: البوم لبويضات ال Ancylostoma  السبت 10 أبريل - 14:35:22 | |
| Ancylostoma Hookworm
eggs
The eggs of
Ancylostoma and Necator cannot be differentiated
microscopically. The eggs are thin-shelled, colorless and measure
60-75 µm by 35-40 µm.  |  | | A | B |
A, B: Hookworm eggs
in unstained wet mounts, taken at 400× magnification.  |  |
C |
D | C,
D: Hookworm eggs in unstained wet mounts.  |  |
E |
Hookworm
rhabditiform larva. [/size] Rhabditiform (L1) larvae that hatch from
eggs are 250-300 µm long and approximately 15-20 µm wide. They
have a long buccal canal and an inconspicuous genital primordium.
Rhabditiform larvae are usually not found in stool, but may be found
there is a delay in processing the stool specimen. If larvae are
seen in stool, they must be differentiated from the L1 larvae of
Stronyloides stercoralis.
 |
 | | A | B | A,
B: Hookworm rhabditiform larva (wet preparation). Hookworm
filariform larva.Infective,
third-stage (L3), filariform larvae are 500-600 µm long. They have
a pointed tail and a striated sheath. These L3 are found in the
environment and infect the human host by penetration of the skin.
 |
 | | A | B | A, B: Filariform (L3)
hookworm larvae.
 |
 |
C |
D | C: Filariform (L3) hookworm
larva in a wet mount.
D: Close-up of the posterior end of a filariform (L3)
hookworm larva.Life
cycles of hookworms.
Eggs are passed in the stool
 , and under favorable conditions (moisture, warmth, shade),
larvae hatch in 1 to 2 days. The released rhabditiform larvae grow in the feces and/or the soil
 ,
and after 5 to 10 days (and two molts) they become filariform (third-stage) larvae that are infective
 .
These infective larvae can survive 3 to 4 weeks in favorable environmental
conditions. On contact with the human host, the larvae penetrate the
skin and are carried through the blood vessels
to the heart and then to the lungs. They penetrate into the pulmonary
alveoli, ascend the bronchial tree to the pharynx, and are swallowed
 .
The larvae reach the small intestine, where they reside and mature into
adults. Adult worms live in the lumen of the small intestine, where they attach to the intestinal wall with resultant
blood loss by the host
 .
Most adult worms are eliminated in 1 to 2 years, but the longevity may reach several years.
Some A. duodenale larvae, following penetration of the host skin, can
become dormant (in the intestine or muscle). In addition, infection by
A. duodenale may probably also occur by the oral and transmammary
route. N. americanus,
however, requires a transpulmonary migration phase. Cutaneous larval migrans (also known as creeping eruption) is a zoonotic infection with hookworm species that do not use humans as a definitive host, the most common being A. braziliense and A. caninum. The normal definitive hosts for these species are dogs and cats. The cycle in the definitive host is very similar to the cycle for the human species. Eggs are passed in the stool , and under favorable conditions (moisture, warmth, shade), larvae hatch in 1 to 2 days. The released rhabditiform larvae grow in the feces and/or the soil , and after 5 to 10 days (and two molts) they become filariform (third-stage) larvae that are infective . These infective larvae can survive 3 to 4 weeks in favorable environmental conditions. On contact with the animal host , the larvae penetrate the skin and are carried through the blood vessels to the heart and then to the lungs. They penetrate into the pulmonary alveoli, ascend the bronchial tree to the pharynx, and are swallowed. The larvae reach the small intestine, where they reside and mature into adults. Adult worms live in the lumen of the small intestine, where they attach to the intestinal wall. Some larvae become arrested in the tissues, and serve as source of infection for pups via transmammary (and possibly transplacental) routes . Humans may also become infected when filariform larvae penetrate the skin  . With most species, the larvae cannot mature further in the human host, and migrate aimlessly within the epidermis, sometimes as much as several centimeters a day. Some larvae may persist in deeper tissue after finishing their skin migration. [/size][/center] | |
|
Tiger
مشرف عالم الحيوان
رقم العضوية : 11
عدد المساهمات : 374
نقاط : 11227
تاريخ التسجيل : 07/03/2010
| | موضوع: رد: البوم لبويضات ال Ancylostoma الإثنين 29 نوفمبر - 18:29:30 | |
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