CLS Exam 4 (1 of 2)

Females are bigger than male

Mucosa of the small intestine

In the intestine

Rhabditiform juveniles

Out with feces

Direct or indirect

Larvae become free living adult male and female worms in the soil

Worms lay eggs that produce more rhabditiform larvae

Becomes filariform larvae

Filariform larvae

Penetrate the host's skin

Carried by the blood to the lungs where it breaks out into the alveoli

The juveniles become parthenogenetic females

Get coughed up, swallowed, and then live in the mucosa of the small intestine

Begins to produce larvae, some of which live indirectly

Rhabditiform larvae immediately becomes filariform and repenetrates the gut without having an outside lifecycle

Direct lifecycle of S stercoralis

Autoinfection

Development of a small filariform larvae in the gut of the host

Larvae penetrate the wall of the lower ileum or colon or the skin of the perianal region

Enter the circulation again, up to the lungs, and back down to the small intestine, thus repeating the cycle

1. Asymptomatic
2. Dermatitis
3. Chest burning, wheezing, coughing
4. Pneumonia-like symptoms (Loffler's syndrome)
5. intestine invasion, leading to burning, tissue damage, sepsis, and ulcers
6. Edema due to obstruction and loss of peristaltic contractions

Swelling, itching, larva currents, and mild hemorrhage at the site where the skin has been penetrated

Chest may feel as if it is burning, and wheezing and coughing may result

Strongyloides stercoralis

Locating JUVENILE LARVAE, either rhabditiform or filariform to confirm presence of parasite

Can be difficult because of the varying juvenile parasite load on a daily basis

ELISA available but can cross-react weigh other filariasis parasites, schistosomes, and Ascaris lumbricoides

Hard to distinguish between active cases and historical cases using ELISA since antibodies can persist for some time

Necator Americans (New World)
Ancylostoma duodenum (Old World)

In the small intestine of the definitive host

Into the two, four, or several cell stage by the time the eggs are passed with feces

Eggs require warmth, shade, and moisture for continued development

Juveniles hatch out of the eggs that are now int he soil and then feed on fecal matter

Juvenile molts and becomes a second stage juvenile

Must molt to the third stage juvenile before it is infective to the definitive host

In the upper few millimeters of soil

They can be killed quickly by freezing or desiccation; therefore necessary for the worm to live in warm, moist tropical places

Worms move to the surface, extending themselves like a snake, wave back and forth

Burrow into it! (Usually through the hands, feet, or bottom)

Carried to the heart and then to lungs, breaking out into alveoli

They are carried by ciliary action up the respiratory tree and swallowed

They attach to the mucosa, grow and molt into the fourth stage and then fifth stage (adult)

5 weeks

1. Number of worms present
2. Nutritional condition of infected person

1. Anemia (depends on # of worms and nutritional stage of host)
2. ground itch
3. Pneumonitis

Sucks more blood

When the worm penetrates the skin other bacteria can cause infection resulting in ground itch

During pulmonary phase of the cycle when the worm breaks out into the alveoli, there can be pneumonitis in severe infections

Finding the eggs in the stool (cant tell which hookworm)

Need adult worm;
N americanus has 2 broad cutting plates in its mouth that latches onto the mucosa of the SI
A duodenale has 2 powerful ventral teeth

Invasive juvenile hookworms of species / strains normally maturing in animals other than humans

Juveniles manage to penetrate the skin f humans but are incapable of successfully completing migration to the intestine

Yes, but before they are killed by immune, they can result in complications of the skin

Cats, dogs, and other domestic animals are most likely to come in contact with people

After entering top layers of epithelium, the juveniles are usually incapable of penetrating further so they begin wandering around under the skin

As they tunnel through the skin, they leave a red, itchy wound that usually becomes infected by bacteria

Weeks or months

Thiabendazole (treatment of choice)

Adult female give birth to larvae (usually the legs and feet of host are infected)

Uterus of female (looking like loop) bursts through the skin and frees many juvenile worms

Juveniles cause an intense immune reaction that causes a blister on the host's skin

Blister ruptures forming an exact for the young worms, which trickle out onto the surface of the skin

Blister hurts so host seeks cool water in which to bathe the infected leg or foot

Access to water; must enter water to survive

Cyclopoid crustacean

In intestine of crustacean: juveniles penetrate into the gut where they develop into third stage juvenile

Crustacean must be swallowed by definitive human host

Person drinks contaminated water

Juvenile worms penetrate the duodenum, pierce the abdominal muscles, and then enter subcutaneous connective tissue

Subcutaneous connective tissue

Male and female mate, male dies

Migrates to the skin of the extremities like legs and feet

10 to 14 months

When the host again finds water to bathe the infected foot / leg

Worms need stagnant foul water in order to thrive because it depends on the crustacean to complete lifecycle
running water / freshwater lakes are NOT usually the habitats of parasites

Stagnant pond water

Most often during drought conditions when water sources are drying up;
common in desert areas where many people rely on ONE water source

Africa and India

1. Emergence of adult worm
2. Secondary bacterial infection
3. Non emergent worms

Powerful allergic reaction caused by the female worm as she migrates underneath the skin

Nausea, diarrhea, dizziness, and local edema (Swelling)
blister develops where the female worm is located

The allergic reactions subside, tiny hole remains where the worm pokes out

Serious complications develop if bacteria is introduced under the skin by worm

In parts of Africa, it is the most common entry of tetanus spores

Worms that fail to reach the skin that cause complications in deeper tissues of the body

When worm dies, it is calcified by the host and chronic arthritis can be the result if the worm is in or alongside joint

Leads to neurological problems

Heart and urogenital system

Worms that degenerate can also release a powerful antigenic substance

Abscesses and arthritis

Itchy red papule that rapidly becomes a blister

Appearance of itchy red papule that rapidly becomes a blister

When blister ruptures, juveniles can be obtained by placing cold water on wound

Placing cold water on the wound

Mounting juveniles (from ruptured blister) and view active movement under low-power microscope

Pulling out guinea worms by winding them on a stick

Cold water applied to worm causes her to expel more juvenile worms and moves her body further out of the wound

5 cm of her body

3 weeks

If metronidazole or similar medication is used in conjunction of pulling out process;
pulled out with minimal effort if someone is on medication

By placing cheesecloth over a container and filtering out the crustacean in the water

In major lymphatic ducts of humans, tightly coiled into modular masses

Live larvae known as MICROFILARIAE

MICROFILARIAE are enveloped in a membrane called a sheath

Sheath can be used to help identify the species of worm

Microfilariae are released into surrounding lymph by female

They are swept into the blood through the thoracic duct

Microfilariae display PERIODICITY in the peripheral blood

They can be found at certain times of day in peripheral blood;
at other times, they disappear from peripheral blood

Between 10 pm and 2 am

Because night-feeding mosquitoes are the primary vectors of this worm

Night-feeding mosquitoes

Mosquito feeds on human host and ingests the worm

They lose their sheath and penetrate the gut and go to the thoracic muscles of the mosquito

Become FILARIFORM juvenile

Migrate to mosquito's proboscis sheath from which they escape when mosquito feeds

Enter the skin through the wound made by the mosquito

Migrate to lymphatics, settle in larger lymph vessels where they mature

Inflammatory and immune responses of individual host

1. Incubation phase
2. Acute / inflammatory stage
3. Obstructive phase

Time between infection and the appearance of microfilariae in the blood

Usually symptomless;
there may be lymphatic inflammation with mild fever and malaise

Occurs when female worm reaches maturity and starts releasing microfilariae

Intense lymphatic inflammation occurs, usually in the lower half of the body, with chills, fever, and toxemia

Infected lymphatic is swollen and painful and overlying skin may be red

Attack usually subsides after a few days but can recur

Inguinal lymphadenitis, or hit is, inflammation of spermatic chord, elephantoid fever

Inflammation of the lymph nodes in inguinal region

Inflammation of testicles

Acute febrile episodes;
rigors, sweating, high fever

Lymph varices, lymph scrotum, chyluria and elephantiasis

Varicose lymph ducts which is caused when lymph return is obstructed;
lymph 'piles up' and dilates the affected duct

Lymph gets into the urine

Chyluria

Scarred and becomes infiltrated with fibrous connective tissue

Occurs after REPEATED attacks of acute lymphatic inflammation

Tissue becomes fibrous and there is thickening of the skin

In men, organs most common is scrotum, legs, and arms;
in women, legs and arms sometimes vulva and breasts

1. Finding microfilariae in stained blood smear
2. Using immunoassays finding anti-filariasis IgG4 in the serum

When elephantiasis occurs, it is more restricted to LEGS and the genitalia are not affected

Finding microfilariae in the blood; sheath has nuclei in it while W bancrofti does not

Adult worms locate under skin where they become encapsulated by host reactions

Prominent nodule appears

Geographical area

Infections are below the waist

infections are above the waist

Remain in the skin where they can be ingested by the black fly intermediate host (of Simulium spp.)

Black fly of Simulium spp

Flies become infected when they take a blood meal from someone who has the disease

First stage juvenile migrates from the intestinal tract of the fly to thoracic muscles

Molts twice to the infective filariform stage

Filariform juvenile moves to fly's labia and can infect a new host when the insect next feeds

Mature worms appear in the skin in less than a year

Simulium spp live their larval stages in only clear, fast running water

Adult flies survive where there is high humidity and stream side vegetation

Makes it impossible to live and farm due to infestation of flies

Adult worms and the microfilariae

Adult is least pathogenic; causes growth of subcutaneous nodules

Pelvic area, spine, chest, and knees

Microfilariae in the skin can cause a severe dermatitis

Intense itching which may lead to secondary bacterial infection; accompanied by depigmentation of skin

Discoloration and cracking of the skin;
skin loses it elasticity and appear prematurely aged

Can cause elephantiasis like symptoms in genitals

Blindness

Microfilariae invade the cornea which causes inflammation of sclera, or whites of the eye

Followed by an invasion of fibrous tissue which severely impairs vision; retina may be damaged along with optic nerve

Demonstration of the microfilariae in a skin snipping

Nematode (roundworm)

Parasitic nematode that has a direct lifecycle (completes all stages of development in one host)

Encapsulated as a small cystic structure within the infected host

Humans become infected when they eat improperly cooked pork or trichinella infected meat

Larvae are released from the muscle cell and migrate to the intestine

Burrow into the intestinal mucosa, mature, and reproduce

female trichinella worms live for about 6 week sand produce many larvae

Larvae can then gain access to the circulation and migrate around the body of the host

Can cause fever and pain brought upon by the host inflammatory response

Because humans are not eaten by another animal which would continue the lifecycle

Trichinosis

Nematode has a tendency to seek out tissue that is highly oxygenated

Diaphragm, chest muscle, tongue, and heart;
can cause myocarditis and encephalitis

Myocarditis (may kill pt)

1. Sylvatic trichinosis
2. Urban trichinosis

Occurs between wild carnivores and their prey or carrion

Bears, badgers, foxes, and even walruses are commonly heavily infected

Occurs between pigs, rats, and humans

When pig eats a rat that is infected it becomes infected itself;
humans become involved in eating undercooked pork

Based on detection of antibodies to excretory / secretory antigen using EIA testing

IgG ab can be detected 12-60 days spots infection

Amount of infective larvae consumed

In the 2nd or 3rd month post-infection and then decline

10+ years

Needs at least 2 serum specimens must be drawn and tested weeks apart to demonstrate seroconversion on pts whose initial results were negative or weakly positive

Allow molecular identification of Trichinella spp or genotype