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
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
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
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 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 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
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 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 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 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 FEMALE nematodes are larger in size. The female reproductive organs are doubled. 2 threadlike ______________________ 2 _________________________ 2 _________________________ single ______________________ _________________________ (female opening)
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 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. M 1 M 2 M 3 M 4 Egg L 1 L 2 L 3 L 4 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 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 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.
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 Anterior end is composed of ___________________ which surround the mouth.
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 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 4. ____________________ is the infective stage and is ingested by a human. 5. L 3 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 L 3 molts to the L 4 stage.
Life Cycle of Ascaris lumbricoides 7. L 4 break into the alveoli, move up the respiratory tree to the pharynx, and __________________________ 8. L 4 move into the _________________________where they molt to the adult stage. Become mature in 2 months. Migratory phase (time from ingestion of the L 3 in egg until L 4 reach the small intestine) is about 25 days.
Life Cycle of Ascaris lumbricoides Adults typically live a year. Why is there this migratory phase?
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 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 DIAGNOSIS - ID eggs in feces Eggs have thick, rough outer shell. Size: There is no diagnostic method for migrating larvae.
Treatment of Ascaris lumbricoides TREATMENT - drug called _____________________________ is effective against adults. No drug treatment is available against migrating larvae.
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 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 L 3 infective stage Adults in small intestine Unembryonatedd eggs in feces (identical to A. lumbricoides)
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 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 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 4 aspects to the life cycle: 1. Normal cycle in the dog Dogs are infected by ingestion of ______________________ Larvae undergo migration through the ___________and are swallowed Reach adulthood in dog _______________________ 1. Normal cycle in dog L 3 L 3
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 ________ penetrates the dog’s intestine and undergoes normal migration. L 3 L 3 L 3 1. Normal cycle in dog 2. Paratenic host
3. Transplantal transmission If a bitch becomes infected, the migrating L 3 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 L 3 L 3 L 3
Toxocara canis Life Cycle 4. Human infection L 3 L 3 L 3 L 3 L 3 4. Human infection Human infections of Toxocara cause ______________________________________________ This disease results when eggs with L 3 are accidentally ingested by humans.
Toxocara canis Life Cycle 4. Human infection L 3 L 3 L 3 L 3 L 3 L 3 hatch in the human small intestine, penetrate the intestine, and enter the circulation. L 3 are carried throughout the visceral organs where they wander randomly - hence, the name "visceral larva migrans". further development? ___________________________ ___________________________
Toxocara canis Life Cycle Eventually, the human immune system recognizes the parasite, encapsulates it with ______________________________, and the L 3 is killed.
Pathology of Visceral Larva Migrans
PATHOLOGY - dependent upon which organs are invaded by the L 3
______________________ 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 L 3 in retina
Tragically, most human cases involve children due to their close association with pets.
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: Larvae in human are very difficult to ID - only way is to ____________________________________ ____________________________________________ TREATMENT - _____________________________has recently been reported to be successful.
Baylisascaris procyonis Raccoon ascarid - common parasite in the small intestine of raccoons This parasite has recently been found to cause ________________________________________________ in HUMANS
Baylisascaris procyonis Raccoons are infected by ingestion of ____________________________ Larvae undergo migration through the __________________________, are swallowed, and reach adulthood in raccoon __________________________ . Egg with L 3
Human Infections of Baylisascaris procyonis Result from the accidental ingestion of eggs with L 3 L 3 hatch in small intestine, penetrate intestine, and enter circulation L 3 have preference for invading the ___________________________________ where they cause a severe tissue reaction - often fatal. Egg with L 3
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 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 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 is parasitic in the stomach and small intestine of ______________ ____________________________________________________________. ____________________________are 1 st intermediate hosts of this parasite. Many species of __________________________serve as 2 nd intermediate hosts of these ascarids - Pacific salmon, Atlantic cod, haddock, herring, & mackeral Egg with L 2 L 2 in copepod or krill L 3 in marine fish
Anisakis spp. Egg with L 2 L 2 in copepod or krill L 3 in marine fish If marine fish containing Anisakis L 3 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 L 3 from marine fish are about 1 inch long. L 3 normally occur in the fish intestine but migrate to the musculature when the fish __________________________ and warm up during transportation.
Pathology of Anisakis in humans PATHOLOGY: 1. Larval Anisakis (an L 3 ) 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. U.S. has ~12 cases/year - mostly in west coast and Hawaii Japan has about 1,000 cases/year DIAGNOSIS and TREATMENT - find L 3 by ______________________________ and remove it PREVENTION -
Enterobius vermicularis - Chap. 27 ____________________________________ - Humans are the only host of this parasite. Cosmopolitan distribution - common in temperate and tropical climates. In Wisconsin?
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 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 Males: _______________________________________________________ ______________________________________________________________ Females: ______________________________________________________ ______________________________________________________________ ______________________________________________________________ female male
Adults of Enterobius vermicularis Female showing esophageal bulb & cephalic alae Male with curved posterior end
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 3. Eggs contain L 1 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 L 3 hatch in the small intestine. 5. L 3 molt twice to the adult stage as the worms move into ileum and large intestine.
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 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 L 3 wander into the large intestine and molt to adults.
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 - ______________________ 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 - Eggs are distinct.
football-shaped with one side flattened
eggshell is smooth
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.