Med Micro Helminths Unit Review

Characteristics of Helminths

- Multicellular eukaryotic heterotrophs
- May possess circulatory, nervous, reproductive, excretory, and digestive systems
- can be monoecious or dioecious

dioecious

2 distinct sexes (each worm only has one sex)

monoecious

hermaphroditic, worm contains both male and female reproductive organs

What are the 2 phyla of Helminths?

- Platyhelminthes (flatworms)
- Nematodes (roundworms)

What are the 2 classes of flatworms?

- Trematodes (flukes)
- Cestodes (tapeworms)

Characteristics of flatworms:

- Typically hermaphroditic (monoecious)
- Protostome (single opening)
- Flattened bodies that are leaf like or long and ribbon like
- Bilaterally symmetrical
- Lack digestive tract and specialized respiratory or circulatory structures

Characteristics of nematodes (roundworms):

- Typically dioecious
- Have complete digestive system (mouth and anus)
- Commonly found in the circulatory and lymphatic system

Characteristics of trematodes (flukes):

- Members of this class will typically target a specific tissue in the host
- Flat and unsegmented
- Leaf like appearance
- Typically have multiple larval stages and hosts
- Monoecious
- Attach to host tissue via oral and ventral suckers

Characteristics of cestodes (tapeworms):

- primarily target the intestines
- Long, flat and segmented
- Monoecious
- Has proglottids
- Mature proglottids detach and pass with feces, allowing eggs to be transmitted to other hosts
- No digestive system, gets nutrients via absorption
- Scolex (head) has hooks and sucks that aids in attachment

What are proglottids?

segment of tapeworms (cestodes) that contain both male and female reproductive organs

What infection is caused by Enterobius vermicularis?

enterobiasis (pinworm)

Life cycle of enterobiasis (pinworm):

1. eggs consumed
2. eggs mature into larvae
3. larvae develop into adult worms in 4. the small intestine
5. male and female reproduce
6. female travels to perianal region at night and lays eggs

characteristics of enterobiasis (pinworm):

-nematode
-dioecious
-females are larger than male
-male reproductive organ: spicule (curled end)
-at risk: children
-size of a grain of rice or staple

symptoms of enterobiasis (pinworm):

-itchy and inflamed rectum
-irritability, insomnia

transmission of enterobiasis (pinworm):

-direct contact
-self infection: when eggs are swallowed or inhaled via fingers, contaminated clothing etc.

diagnosis and treatment of enterobiasis (pinworm):

D: scotch tape test
T: Albenza or pyrantel pamoate

Life cycle of hookworm:

eggs passed through stool and becomes rhabditiform larvae

rhabditiform larvae developed into filariform larvae (infective)

upon human contact, filariform larvae penetrate skin and travel through blood to heart and lungs

larvae are coughed up and swallowed → enter the small intestine and mature into adult worms

What infection is caused by nectar americanus?

hookworm

characteristics of hookworm:

-nematode
-dioecious
-Adult mouth has hooks and cutting/biting plates that allows it to attach to intestines
-at risk: children in low/middle income areas; rural
-size and millimeters and centimeters

symptoms of hookworms:

-itching and localized rash at site where filariform penetrated skin

-severe: ab pain, diarrhea, weight loss, anemia, pneumonitis (lung infection)

-in children: stunted growth, malnutrition and development of learning disabilities

transmission of hookworms:

-direct contact
-walking barefoot, touching soil with bare hands, swallowing bits of contaminated soil

diagnosis and treatment of hookworm:

D: stool sample
T: Albenza or Vermox

What infection does schistosoma cause?

schistosomiasis

characteristics of schistosoma

-trematode
-dioecious

-adult male: wide, and has fold (gynecophoric groove), uses oral suckers to attach to host

-adult female: thin and long; lives in the gynecophoric groove of male where it continuously fertilizes and lays eggs

-egg: lateral spine that aids in motility

-cercariae: larvae stage, has forked tail to aid in motility

-Size in millimeters

life cycle of schistosoma

Eggs released from infected humans via feces or urine

eggs hatch into free swimming larvae (miracidia) that infect snails

miracidium reproduce in snail, forming cercariae, which penetrates human skin

cercariae migrate into blood vessels and travel to lungs, heart and eventually liver

cercariae develop into adult worms in the liver

symptoms of schistosoma

- may be asymptomatic

- Early: itchiness at sight of penetration, fever, chills, cough, muscle aches

- major: damage to liver, intestine, or bladder, distended abdomen, migration to brain/spinal cord → seizures, paralysis, inflammation of spine

transmission of schistosoma

-direct contact
-contact fresh water that contains snails that carry the parasite and can release cercariae into the water

diagnosis and treatment of schistosoma

D: stool/urine sample
T: Praziquantel → only kills adult worms

What infection does Taenia saginata & solium cause:

tapeworm

characteristics of tapeworm

-cestode
-monoecious
-cysticerci: larvae stage
-scolex (head) attached to intestinal walls via suckers
-saginata → beef, larger
-solium → pork, shorter
-Size in several meters

life cycle of tapeworm

Upon ingestion, cysticerci are digested except for the scolex, which attaches to the intestinal walls

scolex produce proglottids (reproductive segments with both testes and ovaries) and body continues to grow

proglottid detach from worm and migrate to anus, passed through stool

in animals: eggs hatch into oncospheres in animals intestines → penetrate intestinal wall → migrate to muscle where they develop into cysticerci

symptoms of tapeworm

- Mild abdominal symptoms (upset stomach, ab pain, loss of appetite, weight loss)

- cysticercosis: infection caused by the ingestion of pork tapeworms eggs rather than cysticerci; If migration to muscles, brain, or eyes occur blurred vision and blindness is possible

- neurocysticercosis: cysticerci in brain/spinal cord; seizures and headaches

transmission of tapeworm

- food and water borne
- ingestion of undercooked meat containing cysticerci

diagnosis and treatment of tapeworm

D: stool sample

what infection does Ascaris lumbricoides cause?

- Ascariasis
- ascaris pneumonia

characteristics of Ascaris lumbricoides

-nematode
-dioecious
-adult males are smaller than females

-adult males have spicules
-Eggs have scalloped edges (mammillations)

-Size in inches and feet
-One of the most common infections in the world
-at risk: children; use of human feces as fertilizer and poor sanitation systems

life cycle of Ascaris lumbricoides

Infective eggs are swallowed and hatch into larvae in small intestine

larvae penetrate the intestinal walls and eventually enter the systemic circulation

larvae traveled through blood into the heart and then the capillaries of the lungs

larvae are coughed up and swallowed and eventually return to the small intestine were they mature into adult worms

symptoms of Ascaris lumbricoides

- Usually asymptomatic
- mild: abdominal discomfort

- severe: ab pain, intestinal blockage, perforations (internal bleeding), pneumonia; migration of adult worms could cause appendicitis or nasopharyngeal expulsion

transmission of Ascaris lumbricoides

- Food and waterborne
- ingestion of food or water that has been contaminated with infective eggs

diagnosis and treatment of Ascaris lumbricoides

D: stool sample
T: surgery in severe cases; Albenza or Pyrantel Pamoate

What infection is caused by Trichinella spiralis?

Trichinellosis (whipworm)

Life cycle of Trichinella spiralis (whipworm)

1. after consumption encapsulated cysts are broken open during digestion to release infective larvae

2. Once within the host intestinal tract the infective larvae embeds into gut mucosa where they mature into adult worms

3. Female worms lay larvae as eggs hatch in their uterus

4. Larvae exit gut wall and enter the blood system to travel to different muscles (eyes, tongue, chewing muscles)

5. larvae grows within muscle and a covering develops causing a cyst ← once cyst the larvae cannot move

characteristics of Trichinella spiralis (whipworm)

- Nematode
- dioecious
- very broad range of reservoirs (pigs, rats, bears Etc)
- Adult worms found in GI tract; larvae and muscles
- have cuticles and ridges for protection

symptoms of Trichinella spiralis (whipworm)

Early stage - gastrointestinal issues (nausea diarrhea, vomiting)

Classical stage -
- invasion of larvae to muscle leads to weakness, twitching, issues using large motor muscles
- inflammation of eyes,
- issues with chewing, swallowing
- difficulties with respiration & CNS and cardiac problems

transmission of Trichinella spiralis (whipworm)

- Foodborne
- ingestion of raw and undercooked meat infected with trichinella
- most common through consumption pork

diagnosis and treatment of Trichinella spiralis (whipworm)

D- Antibody test, muscle biopsy
T- prompt treatment necessary; once larvae form in skeletal muscles treatment is not as effective

What infection is caused by Dracunculus medinensis?

Guinea worm disease

Life cycle of Dracunculus medinensis (Guinea Worm Disease)

1. Initiated by drinking water containing copepods ( water fleas)

2. when copepods are ingested, they are digested but the dracunculus larvae penetrates the stomach and intestinal walls to enter the abdominal cavity

3. Larvae mature into adult worms and reproduce

4. male worms die and female worms migrate towards the skin surface of the led or foot

5. painful blisters occur that eventually rupture at site

characteristics of Dracunculus medinensis (Guinea Worm Disease)

- Nematode
- dioecious
- There is hope that this can be the first helminthic infection to be eradicated

symptoms of Dracunculus medinensis (Guinea Worm Disease)

- pre-blisters --\> fever, pain, blister formation in legs ( burning sensation), difficulty walking
- post-rupture of blisters --\> worms cut through flesh out of the body

transmission of Dracunculus medinensis (Guinea Worm Disease)

- Waterborne
- ingesting water contaminated with copepods (water fleas)

diagnosis and treatment of Dracunculus medinensis (Guinea Worm Disease)

- T- coiling the worm around a small stick as it is expelled from the body
- topical antibiotics apply to prevent secondary infections at the open wound where the worm is exiting the body

What infection is caused by lymphatic filariasis?

Elephantiasis

Life cycle of lymphatic filariasis (elephantiasis)

life cycle of Wuchereria bancrofti --\>
1. Infections are initiated by the bite of mosquitoes containing filarial larvae

2. Larvae migrate into the lymphatic vessels and mature into adult worms

3. adult worms mate and females release millions of microfilariae into the blood, which can be ingested by the mosquito repeating the cycle

characteristics of lymphatic filariasis (elephantiasis)

- Three main species --\> Wuchereria bancrofti, Brugia malayi, and Brugia timori
- Nematode
- Common and tropical and subtropical areas

symptoms of lymphatic filariasis (elephantiasis)

- Mostly asymptomatic
- small percent develop lymphedema (blockage of lymphatic vessels cause the accumulation of large amounts of lymphatic fluid in the limbs resulting in swelling)

- secondary infections, pain, fever, chills
- hardening and thickening of skin --\> elephantiasis
- other sensitive areas to swelling are penis in males and breasts in females

transmission of lymphatic filariasis (elephantiasis)

- arthropod borne
- bite of mosquitoes carrying filarial larvae

diagnosis and treatment of lymphatic filariasis (elephantiasis)

D- Blood samples
T- antifungal drug to eliminate microfilaria ( has limited impact on adult worms)

What infection is caused by Onchocerca volvulus?

Onchocerciasis (river blindness)

Life cycle of Onchocerca volvulus (rive blindness)

1. bite of infected black fly introduces microfilariae into body

2. Microfilariae mature into adult worms in the skin

3. Female worms migrate to subcutaneous tissues and become encapsulated by a fibrous cell (nodules)

4. males migrate to these nodules to fertilize the females and females produce millions of microfilariae

5. Microfilariae migrate away from adult worms through blood and lymphatic fluid and can be found in skin, lymph vessels, blood, urine, CSF, internal organs (especially eyes)

characteristics of Onchocerca volvulus (rive blindness)

- Nematode
- dioecious
- Found mainly in West and sub-Saharan Africa

symptoms of Onchocerca volvulus (rive blindness)

- Based on host immune responses to the adult worm and the microfilariae (mostly dead or dying)
- Dermatologic: nodules, intense itching, skin depigmentation and discoloration (" leopard skin" appearance), cracking of skin and loss of skin elasticity
- Inflammation of eyes → clouding of cornea → blindness if left untreated

transmission of Onchocerca volvulus (rive blindness)

- Arthropod borne
- bite of infected black fly

diagnosis and treatment of Onchocerca volvulus (rive blindness)

D- eye exams, nodules, skin snip ( shaving, biopsy)
T- Ivermectin (can kill microfilaria but not adult worms); might need for 10-15 years for adult worms to complete their life cycle