Nematoda Ascarids

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Information about Nematoda Ascarids
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Published on November 19, 2007

Author: Isab

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Phylum Nematoda - Chapter 22:  Phylum Nematoda - Chapter 22 Nematodes or roundworms are among the most abundant animals on earth - over 500,000 species have been described. Majority of nematodes are free-living in every conceivable habitat. free-living species are commonly microscopic in size importance? ____________________________ Phylum Nematoda :  Phylum Nematoda Two groups of nematodes are parasitic:   (1) ___________________________________ - cause diseases of medical and veterinary importance - attract the attention of parasitologists   (2) ___________________________________ - may destroy plants resulting in economic losses - attract the attention of plant pathologists Characteristics of the Phylum Nematoda:  Characteristics of the Phylum Nematoda 1. Body is non-segmented, elongate, and circular in cross-section (i.e. the name "roundworms"). 2. Body wall consists of: a) outermost noncellular ______________________________ b) underlying ___________________________ that secretes the cuticle is a cellular syncytium with nuclei lying in 4 thickenings Characteristics of the Phylum Nematoda:  Characteristics of the Phylum Nematoda c) ____________________________________ lies below the hypodermis contractile and noncontractile regions are present   no circular muscle is present; worm cannot shorten or lengthen movement is due to undulating motion caused by contraction of the longitudinal muscles Characteristics of the Phylum Nematoda:  Characteristics of the Phylum Nematoda 3. _____________________________________ is body cavity beneath the musculature.  - cavity is called a "pseudocoelom" as it is not lined internally with ______________________________  - pseudocoelom is filled with a fluid called pseudocoelomic fluid - reproductive organs are suspended within the pseudocoelom Characteristics of the Phylum Nematoda:  Characteristics of the Phylum Nematoda Pseudocoelomic fluid has two functions: (1) serves as _________________________________________ giving the body rigidity (2) serves as ________________________________________ transporting materials from cell to cell   Characteristics of the Phylum Nematoda:  Characteristics of the Phylum Nematoda 4. Digestive tract is complete.   Mouth pharynx esophagus intestine anus   Intestine possesses well-developed microvilli for absorption. Food - ___________________________________ ___________________________________ Little digestion occurs within the nematode intestine; it is dependent upon the host to digest food into an absorbable form. Characteristics of the Phylum Nematoda:  Characteristics of the Phylum Nematoda 5. Nervous system consists of a circumesophageal nerve ring and 2 or 4 longitudinal nerve trunks extending the length of the nematode. Seen only with special staining Characteristics of the Phylum Nematoda:  Characteristics of the Phylum Nematoda 6. Excretory system is primitive and consists of 1 or 2 _____________________________ and excretory ducts Excretory pore is anterior. No flame cells are present. Characteristics of the Phylum Nematoda:  Characteristics of the Phylum Nematoda 7. Nematodes are _______________________ Reproductive system consists of tubular organs lying in the pseudocoelom. MALE nematodes are generally smaller in size. Posterior end is often curved due to presence of ____________________________________+. Male system is a single tubule. Inner end is _________________________ ___________________________ ___________________________ ____________________________ supported by spicules   Characteristics of the Phylum Nematoda:  Characteristics of the Phylum Nematoda FEMALE nematodes are larger in size. The female reproductive organs are doubled. 2 threadlike ______________________ 2 _________________________ 2 _________________________ single ______________________ _________________________ (female opening)   Characteristics of the Phylum Nematoda:  Characteristics of the Phylum Nematoda In both the male and female systems, the tubular organs are continuous and increase in diameter as they extend to the genital opening. When viewed in cross-section, the organs are histologically distinct. Male Female Characteristics of the Phylum Nematoda:  Characteristics of the Phylum Nematoda 8. Nematode development is similar in all nematodes.  Consists of 4 larval (=juvenile) stages between the egg and adult. Each stage is separated by a molt of the cuticle.   M1 M2 M3 M4 Egg L1 L2 L3 L4 Adult Larval stages may be passed within the egg, free-living in soil, parasitic in an intermediate host, or parasitic in definitive host. Ascarid Nematodes – Chapter 26:  Ascarid Nematodes – Chapter 26 Ascaris lumbricoides Common parasite of humans. Disease is called ______________________________ Cosmopolitan in distribution.  - flourishes in warm, moist climates where the eggs may remain viable in warm soil for many years.  - use of ___________________________ to fertilize vegetables is common source of infection.  - Children are most likely to become infected by ingesting eggs by eating dirt or placing soiled fingers or toys into the mouth. Ascaris lumbricoides:  Ascaris lumbricoides Human is the only definitive host of this parasite. In the U.S. infections are most common in _________________________________ Parasite is endemic in Wisconsin - prevalence is low - 1.3% in 1976 and 0.5% in 1987. Ascaris lumbricoides:  Ascaris lumbricoides ADULTS are the largest nematode parasites of humans. Males are ______________ inches in length and 1/8 inch in diameter. posterior end is curved due to presence of spicules. Females are ______________ inches in length and 1/4 inch in diameter. Ascaris lumbricoides:  Ascaris lumbricoides Anterior end is composed of ___________________ which surround the mouth. Ascaris lumbricoides:  Ascaris lumbricoides EGGS are __________________________________________ _____________________________________________. Eggs are unembryonated when passed in the feces. Embryonation occurs in the soil.   Unembryonated egg in feces Embryonated egg in soil Life Cycle of Ascaris lumbricoides:  Life Cycle of Ascaris lumbricoides 1. Adult males and females live in _______________________ 2. Female releases 200,000 eggs/day which are passed in the feces. 3. Eggs embryonate in warm, moist shady soil and __________________stages are passed within the egg. Life Cycle of Ascaris lumbricoides:  Life Cycle of Ascaris lumbricoides 4. ____________________ is the infective stage and is ingested by a human. 5. L2 hatches from egg in the duodenum, penetrates the duodenum, enters the circulation, travels through the heart, and reaches the ____________________ via the pulmonary circulation.  6. In the lungs, the L2 molts twice to the L4 stage. Life Cycle of Ascaris lumbricoides:  Life Cycle of Ascaris lumbricoides 7. L4 break into the alveoli, move up the respiratory tree to the pharynx, and __________________________   8. L4 move into the _________________________where they molt to the adult stage. Become mature in 2 months.   Migratory phase (time from ingestion of the L2 in egg until L4 reach the small intestine) is about 25 days.     Life Cycle of Ascaris lumbricoides:  Life Cycle of Ascaris lumbricoides Adults typically live a year. Why is there this migratory phase?     Pathology of Ascaris lumbricoides:  Pathology of Ascaris lumbricoides Adults cause: (1) _________________________ (due to toxemia from Ascaris waste products) (2) __________________________(due to loss of monosaccharides and amino acids absorbed by the worms) (3)__________________________________by large numbers of tangled worms (may be fatal). Pathology of Ascaris lumbricoides:  Pathology of Ascaris lumbricoides Larvae cause problems in the lungs when they break through the lung capillaries to enter the respiratory tree. (1) small hemorrhages are produced causing plasma to enter alveoli resulting in ________________________ (2) inflammatory response to this damage occurs and __________________ _________________________________________ resulting in pneumonia-like symptoms The more eggs ingested, the more migrating larvae, the greater the pathology.   larva Inflammatory cells Ascaris lumbricoides:  Ascaris lumbricoides DIAGNOSIS - ID eggs in feces Eggs have thick, rough outer shell. Size: There is no diagnostic method for migrating larvae. TREATMENT -     Ascaris suum:  Ascaris suum ___________________________ is the single greatest cause of economic loss in the swine industry. Adults of A. suum are nearly identical to A. lumbricoides in morphology (differences are visible only with scanning EM). Parasitologists believe that a single species of Ascaris infected both humans and pigs at one time but has now evolved into two separate species - one infecting humans and one infecting pigs.       Ascaris suum:  Ascaris suum LIFE CYCLE, PATHOLOGY, DIAGNOSIS, AND TREATMENT of A. suum is identical to that of A. lumbricoides except that pigs are the only hosts.     Larval migration in lungs Egg with L2 infective stage Adults in small intestine Unembryonatedd eggs in feces (identical to A. lumbricoides) Ascaris suum:  Ascaris suum Question? Can Ascaris suum develop into adults in humans? Difficult to find a volunteer for this experiment but we did find out an unusual way.   Ascaris suum:  Ascaris suum   Ascaris suum:  Ascaris suum   What did we find out from infections in these “volunteers’? 1. If eggs of A. suum are ingested by a human, the ___________ larvae will hatch from the egg and undergo _______________________________. 2. The migration is abnormal and greater pathology occurs in the human lungs resulting in severe ____________________. A near-fatal pneumonia occurred in the roommates 3. Adults? _____________________________________ Toxocara canis and Toxocara cati:  Toxocara canis and Toxocara cati Common ascarids in the ___________________________________________________ Prevalence in dogs and cats is estimated to be 20 to 100%. These parasites are enzootic in Wisconsin dogs and cats.   Adults are much smaller than Ascaris. - males are about ____ inches in length - females are _____________inches in length Toxocara canis Life Cycle:  Toxocara canis Life Cycle 4 aspects to the life cycle: 1. Normal cycle in the dog Dogs are infected by ingestion of ________________________ Larvae undergo migration through _____________ and are swallowed Reach adulthood in dog _________________________ 1. Normal cycle in dog Toxocara canis Life Cycle:  Toxocara canis Life Cycle 2. Addition of a paratenic host (mouse) If a mouse ingests an infective egg, the _______________ hatches and migrates to many internal organs. It develops no further. If mouse is eaten by a dog, the L2 penetrates the dog’s intestine and undergoes normal migration.   1. Normal cycle in dog 2. Paratenic host Toxocara canis Life Cycle:  Toxocara canis Life Cycle 3. Transplantal transmission If a bitch becomes infected, the migrating L2 can cross the placenta to infect the fetal puppies. When the puppies are born, they are already infected with adult worms. Prevalence rates in puppies can reach 100% because of the efficiency of transplacental transmission. 3. Transplacental transmission Toxocara canis Life Cycle:  Toxocara canis Life Cycle 4. Human infection Human infections of Toxocara cause _______________________ _______________________ This disease results when eggs with L2 are accidentally ingested by humans. 4. Human infection Toxocara canis Life Cycle:  Toxocara canis Life Cycle L2 hatch in the human small intestine, penetrate the intestine, and enter the circulation. L2 are carried throughout the visceral organs where they wander randomly - hence, the name "visceral larva migrans". further development? ___________________________ ___________________________ 4. Human infection Toxocara canis Life Cycle:  Toxocara canis Life Cycle Eventually, the human immune system recognizes the parasite, encapsulates it with ______________________________, and the L2 is killed.   Pathology of Visceral Larva Migrans:  Pathology of Visceral Larva Migrans PATHOLOGY - dependent upon which organs are invaded by the L2 ______________________ is commonly invaded - hepatomegaly & cirrhosis may occur __________________________ invasion results in a severe tissue reaction that can result in death 3. _____________________________may be invaded - scar tissue deposition in the retina can result in blindness   Scar tissue in retina L2 in retina Slide39:  Tragically, most human cases involve children due to their close association with pets.   Diagnosis and Treatment of Toxocara in Dogs & Cats:  Diagnosis and Treatment of Toxocara in Dogs & Cats DIAGNOSIS: Adults in dog - Identify egg in feces Diagnostic features – ____________________________ ____________________________ ____________________________ TREATMENT - Diagnosis and Treatment of Human Visceral Larva Migrans:  Diagnosis and Treatment of Human Visceral Larva Migrans DIAGNOSIS: Larvae in human are very difficult to ID - only way is to ____________________________________ ____________________________________________   TREATMENT - _____________________________has recently been reported to be successful. Prevention of Human Infection:  Prevention of Human Infection 1. _______________________________________________ 2. _______________________________________________ many cities have enacted "pooper scooper" laws that require owners to clean up after their pets especially important in parks where pet owners take animals for walks and children are playing 3. ________________________________________________ Baylisascaris procyonis:  Baylisascaris procyonis Raccoon ascarid - common parasite in the small intestine of raccoons This parasite has recently been found to cause ________________________________________________ in HUMANS   Baylisascaris procyonis:  Baylisascaris procyonis Raccoons are infected by ingestion of ____________________________ Larvae undergo migration through the __________________________, are swallowed, and reach adulthood in raccoon __________________________ . Egg with L2 Human Infections of Baylisascaris procyonis:  Human Infections of Baylisascaris procyonis Result from the accidental ingestion of eggs with L2 L2 hatch in small intestine, penetrate intestine, and enter circulation L2 have preference for invading the ___________________________________ where they cause a severe tissue reaction - often fatal.   Human Infections of Baylisascaris procyonis:  Human Infections of Baylisascaris procyonis Four human fatalities - in Pennsylvania (1983), Illinois (1985), and two in 2002 in Minnesota occurred in children who had associations with raccoons. Human Infections of Baylisascaris procyonis:  Human Infections of Baylisascaris procyonis This parasite is a POTENTIAL HEALTH HAZARD IN WISCONSIN Wisconsin DNR survey indicated that 51% of our raccoons are infected. Highest prevalence is in the southern half of the state. Juvenile raccoons have heavy infections What might this suggest? Human Infections of Baylisascaris procyonis:  Human Infections of Baylisascaris procyonis Having a young raccoon as a pet could be a fatal mistake! Raccoon hunters and trappers should be aware of this dangerous parasite. Anisakis spp.:  Anisakis spp. Anisakis is parasitic in the stomach and small intestine of ______________ ____________________________________________________________. ____________________________are 1st intermediate hosts of this parasite.  Many species of __________________________serve as 2nd intermediate hosts of these ascarids - Pacific salmon, Atlantic cod, haddock, herring, & mackeral Egg with L2 L2 in copepod or krill L3 in marine fish Anisakis spp.:  Anisakis spp. Egg with L2 L2 in copepod or krill L3 in marine fish If marine fish containing Anisakis L3 are eaten in raw or poorly cooked fish (i.e. sushi, cerviche, etc.), HUMANS CAN SERVE AS ACCIDENTAL HOSTS. Disease is called ________________________________________   Human ingests raw fish Anisakis spp.:  Anisakis spp. Portion of Anisakis L3 from marine fish - L3 are 1 inch long Pathology of Anisakis in humans:  Pathology of Anisakis in humans PATHOLOGY: 1. Larval Anisakis (an L3) burrows into the wall of the stomach or small intestine - _______________________is produced around larva   - causes _________________________________ 2. Larva eventually dies (humans are abnormal hosts) resulting in a _______________________________________________ to the dead worm - this response mimics an ulcer or acute apppendicitis   - fatalities have occurred. Human Cases of Anisakis spp.:  Human Cases of Anisakis spp. U.S. has ~12 cases/year - mostly in west coast and Hawaii  Japan has about 1,000 cases/year DIAGNOSIS and TREATMENT - find L3 by ______________________________ and remove it PREVENTION - Enterobius vermicularis - Chap. 27:  Enterobius vermicularis - Chap. 27 ____________________________________ - Humans are the only host of this parasite. Cosmopolitan distribution - common in temperate and tropical climates. In Wisconsin? Enterobius vermicularis :  Enterobius vermicularis Almost anybody can become infected with this parasite. No social class is exempt. These parasites soon become "family affairs". Once one person, usually a child becomes infected, other family members will undoubtedly also become infected.   Adults of Enterobius vermicularis :  Adults of Enterobius vermicularis Adults live in the _______________________________________________ (ileum, cecum, appendix, and colon). They feed on bacteria and dead intestinal cells - they do not invade tissue. Pinworms are recognized by 2 structures: 1. ____________________________- winglike extensions of the cuticle at the anterior end   2. _______________________________- muscular bulb at end of esophagus Adults of Enterobius vermicularis :  Adults of Enterobius vermicularis Males: _______________________________________________________ ______________________________________________________________ Females: ______________________________________________________ ______________________________________________________________ ______________________________________________________________   female male Adults of Enterobius vermicularis :  Adults of Enterobius vermicularis Female showing esophageal bulb & cephalic alae Male with curved posterior end Life Cycle of Enterobius vermicularis :  Life Cycle of Enterobius vermicularis 1. Adults copulate in the human digestive tract. Male dies after copulation. 2. Female migrates at night to the perianal folds of the anus and deposits eggs (commonly over 10,000) in the skin of the ____________________. Female dies after all eggs have been laid. Life Cycle of Enterobius vermicularis :  Life Cycle of Enterobius vermicularis 3. Eggs contain L1 larvae when laid, but within 6 hours larvae molt twice in the egg to the ______ stage. 4. ____________________ are infective and when ingested by a human, the L3 hatch in the small intestine. 5. L3 molt twice to the adult stage as the worms move into ileum and large intestine. Life Cycle of Enterobius vermicularis :  Life Cycle of Enterobius vermicularis METHODS OF HUMAN INFECTION: 1. Infective eggs may be transmitted _____________ ______________________________________________ Deposition of eggs by the female causes _______________________ 2. Bed clothing and bedding are contaminated with infective eggs and ingested. 3. _____________________ - eggs are inhaled and ingested. Life Cycle of Enterobius vermicularis :  Life Cycle of Enterobius vermicularis METHODS OF HUMAN INFECTION cont: 4. Infective eggs can become ______________________ (sweeping in a bedroom) and can be inhaled and swallowed. 5. _____________________ - if the perianal region is not cleaned for some time, infective eggs may hatch and the L3 wander into the large intestine and molt to adults. Pathology of Enterobius vermicularis :  Pathology of Enterobius vermicularis 1. Pinworms are generally considered to be harmless as they do not invade any tissue. They may cause ___________________ __________________________________________________. 2. They do cause irritation of the anal region resulting __________________________________________________. Secondary bacterial infection in areas scratched raw may occur. 3. Pinworms also cause ______________________________ - mental anguish and embarrassment of parents whose kids have "worms" - this often leads to frantic efforts to eliminate the parasite and its eggs. Diagnosis of Enterobius vermicularis :  Diagnosis of Enterobius vermicularis DIAGNOSIS - ______________________is commonly used. Use of double-stick tape on a tongue depresser. This is pressed against the perianal folds where eggs will stick to the tape. Tape is then stuck onto a microscope slide and examined for eggs.   Diagnosis of Enterobius vermicularis :  Diagnosis of Enterobius vermicularis DIAGNOSIS - Eggs are distinct. Treatment of Enterobius vermicularis:  Treatment of Enterobius vermicularis TREATMENT - pinworms are easily killed with drugs - _________________________________________________ To prevent re-infection, treat the whole family. Wash all bed clothes and bedding in hot water to kill infective eggs.  

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