Parasitology 4091 EXAM 1

what is parasitology?

the study of parasites

what is symbiosis?

living together; special relationship between two species which is necessary for the survival for at least one of those species

what are the different forms of symbiosis?

mutualism

commensalism

parasitism

what is mutualism?

both species in the relationship benefit (+,+)

ie: termite and flagellated protozoa in its intestines

what is commensalism?

one organism in the relationship lives at the expense of the other but doesn't cause any harm (+, 0)

ie: shark and pilot fish - the pilot fish uses the shark for protection and scraps of food

what is parasitism?

one organism in the relationship benefits greatly and the other is harmed (+, -)

ie: parasite and host

what does infest mean?

lives exterior (lice, fleas, etc.)

what does infect mean?

lives within/inside

what is pathology?

tissue damage; can be a range from little to no pathology to severe pathology

what is the relationship like between a parasite and the host the longer the relationship lasts?

the longer the relationship between the parasite and the host has existed the less harm the parasite does to the host

if it is a long relationship it can be seen more as commensalism and may not really cause any pathology

what is a facultative parasite?

opportunistic parasite; free-living life cycle or a parasitic life cycle (two ways of life)

doesn't have to be parasitic

if the environment becomes harsh it can change from a free-living life cycle to parasitic

what is an obligatory parasite?

parasite completely dependent for at least part of its life cycle on a host; obligated to the parasitic lifestyle

what is an endoparasite?

parasite that lives inside a host (causes an infection)

what is an exoparasite?

parasite that lives outside/on the host (cause an infestation)

what is a definitive host?

where the parasite attains sexual maturity and reproduction takes place

the definitive host is usually the infective host in which it can be spread

usually the offspring from this stage infect the intermediate host

what is an intermediate host?

a temporary host necessary for the completion of the life cycle

usually has a larval or dependent stage

from the developmental stage it can reach the infective stage and then infect the definitive host (snails are an intermediate host)

what is a transfer host?

not necessary for the lifecycle but it helps the parasite (ie: fly - transferring a parasite from feces to food)

bringing something to you that you would not seek out

what is a vector host?

intermediate or definitive host that transmits the parasite or it transmits the disease (ie: mosquito, flies, bugs, etc.)

malaria: the mosquito would be a definitive host

what is a reservoir host?

holds the parasite or it keeps the parasite in an environment

animal serves as a source of infection so you can completely eradicate the parasite from human infection but it can always come back because of a reservoir host

what does exposure mean in the biological incubation period?

you are in the presence of an infection or infectious agent

what does colonization mean in the biological incubation period?

where the organism moves from exposure to colonization in your body or on your skin; broken through natural defense factors (doesn't have to lead to infection)

what does infection mean in the biological incubation period?

where you have the agent in or on your body and you have signs and symptoms

what are signs in the biological incubation period?

something that is measurable (quantitative; temp, pulse, etc.)

what are symptoms in the biological incubation period?

some type of qualitative measurement (pain, not feeling well, etc.)

what is the incubation period?

timespan; time period between the exposure and signs/symptoms

what is the latency period?

time period between the infection and being infectious

infection vs. disease

infection has signs and symptoms

disease has pathology (some type of tissue damage or tissue change)

what are some general parasite effects on hosts?

utilization of hosts as food

destruction of hosts tissues

traumatic damage

obstruction of lumens

penetration of host tissue

what are two different types of parasites that result in destruction of the hosts tissue?

blood feeders

lytic necrosis

what are blood feeder parasites?

they're after the fluid part of the blood (protein, amino acids, carbohydrates, etc.)

what is an example of a blood feeder parasite?

hookworm

what is a lytic necrosis parasite?

dissolves tissue; takes in solid tissue and enzymatically dissolves/liquifies it and takes it in

what is an example of a lytic necrosis parasite?

Entamoeba histolytica

what results in traumatic tissue damage?

internal larval migrations

give an example of an internal larval migration

hookworm;

eggs in feces/soil --> eggs hatch (larval stages) --> Filiaform larvae (infective stage) --> get on the skin & penetrate (1) skin usually through feet (lesion on skin) --> enters (2) circulation (rupture of blood vessel) --> travel to the (3) lungs (rupture of capillaries) --> migrate up the respiratory track in which you will then swallow and they will move to the (4) small intestine (where you are going to have adult worms) --> adults will give off eggs that go to the feces and repeats

what parasite can cause obstruction of the lumen?

Ascaris lumbricoides (giant round worm)

instead of utilizing the host as food it consumes the food in the intestines that we ingest

how can Ascaris lumbricoides obstruct the lumen?

it swims against peristaltic action (can only move forward)

it can go into the bile duct and pancreatic duct (which is the same diameter) and block them

you can also have a population of them in your intestines and if there is a change in the environment (pH, temp., antibiotics, etc.) that isn't favorable they will ball up and block the entire intestinal tract

sometimes they can break the intestinal wall and get into the peritoneal cavity which may cause an infection

what parasite can penetrate the host tissue?

Entamoeba histolytica

it can lyse through the entire wall of the large intestine and you get peritonitis and possible infection

what does parasite density and distribution depend upon?

flora (plant life)

fauna (animal life)

water (influences flora and fauna)

you'll have a lot of habitat for animals and those animals are intermediate hosts or vectors

what is the parasite biotic potential?

parasites of hyper-reproductivity

parasites life cycles are very complex, meaning not a lot of them make it through, so they need to be able to have a lot of offspring in order to survive

explain the life cycle of Entamoeba histolytica

very high biotic potential Trophozoite (division) --> cyst (resilient) (nuclear division occurs - more nuclei form (4)) --> if ingested the cyst breaks open and you have 4 trophozoites --> then they mature and you have 4 cysts (nuclear division occurs again (4 each)) --> then you have 16 trophozoites

explain the life cycle of Amoeba proteus

simple reproductive life cylce (doesn't have high biotic potential)

divides evenly each time

1 --> 2 --> 4 --> 8 --> 16

what are the different divisions of helminths?

nematodes (roundworm)

cestodes (tapeworms)

trematodes (flukes/flatworm)

what are the different divisions of protozoan?

amoeba

ciliates

flagellates

sporozoites

what are three intestinal nematodes that are infective in the egg stage?

Enterobius vermicularis (pinworm)

Trichuris trichura (whipworm)

Ascaris lumbricoides (giant roundworm)

what is the normal life cycle of a Enterobius vermicularis?

eggs ingested --> larvae hatch in the small intestine --> migrate to colon where the mature --> adults migrate out of anus at night --> adults lay eggs on perineum --> eggs embryonate on perineum --> eggs contaminate fingers --> eggs ingested

what are three abnormal life cycles of Enterobius vermicularis?

female reproductive tract

appendix

retroinfection

explain the abnormal life cycle of Enterobius vermicularis in regards to the female reproductive tract

worms migrate to the vagina --> uterus --> fallopian tubes

when the female ruptures (lays eggs) in the fallopian tubes there is a lot of foreign material located in the fallopian tubes

inflammation is going to occur --> infiltration of WBCs --> scar tissue forms

as more scar tissue forms, the lumen of the fallopian tube will start to narrow - this blocks the egg from getting to the uterus leading to infertility

explain the abnormal life cycle of Enterobius vermicularis in regards to the appendix

they can migrate to the appendix and which they get stuck and start to cause damage which leads to a bacterial infection

tissue damage will then occur which will cause inflammation (appendicitis) so the appendix has to be removed

explain the abnormal life cycle of Enterobius vermicularis in regards to retroinfection

the female worm comes out of the perianal opening but decides to go back to the large intestine -- so the eggs get released and hatch in the large intestine rather than going through the oral cavity

this can result in a high/large infection

explain the eipdemiology of Enterobius vermicularis?

group infections (when one person gets it they all get pinworm)

kindergarten to 3rd grade

direct and indirect transmission

more infections in colder climates

explain direct transmission of Enterobius vermicularis

anus to hand (fomite - inaminate object that is the egg carrier) to mouth

explain the indirect transmission of Enterobius vermicularis

airborne eggs (parents making the bed of their children)

what is the pathology/clinical manifestion of Enterobius vermicularis in the large intestine?

attachment damage only in the area where the worm is; this is going to lead to irritation caused by feeding of the adult worm and this feeding causes necrosis of the area

all of these things are going to cause inflammation

what is the pathology/clinical manifestation of Enterobius vermicularis in regards to toxic metabolites?

worms release waste product; these toxic metabolites are solubilized in the water and reabsorbed - kids tend to exhibit nervousness, insomnia, irritability, and convulsions

what is the pathology/clinical manifestation of Enterobius vermicularis in the perianal area?

from scratching a lot a child can develop benign tumors (scar tissue)

what is the pathology/clinical manifestation of Enterobius vermicularis in the appendix?

appendicitis - removal of appendix

what is the pathology/clinical manifestation of Enterobius vermicularis in the vagina/fallopian tubes?

infertility

how can you diagnose Enterobius vermicularis?

anal swab with a q-tip

scotch tape test

preserve worms in alcohol, vinegar, vodka, or gin

how can you treat Enterobius vermicularis?

albendazole - decrease the glucose uptake of worms

what are ways to prevent Enterobius vermicularis?

personal hygiene

mass chemotherapy - treat everybody (everyone in daycare)

detergent

sunlight/UV light

what is the life cycle of Trichuris trichura?

embryonated eggs ingested --> larvae hatch in small intestine --> adult worms located in cecum --> unembryonated eggs passed in feces --> 2-cell stage --> advanced cleavaged --> embryonated eggs ingested

what is the epidemiology of Trichuris trichura?

warm and moist areas (southeastern US and parts of Asia)

rural areas (farming)

associated with nights soil (where you use human waste/feces to put on crops as fertilizer)

primary school aged children

why does Trichuris trichura need warm and moist areas?

warm causes it to become embryonated and moist areas is so that the egg doesn't dry out and viable for a longer period of time

what is the difference between prevalence and incidence?

prevalence includes old and new cases (ALL people infected) while incidence is only new cases of the infection

in order to ensure the Trichuris trichura is not located in nights soil, what must you do?

compost it and ensure that the soil dries out (sterlizing itself) so that way whipworm is not there

what is the pathology/clinical manifestion of Trichuris trichura in the large intestine?

they attach to the gut wall and feed on the gut wall

they sew themselves into the gut wall (with the thin portion of their body) - here they carve out and feed its way into the wall of the large intestine

the large portion of the worm is out in the lumen where the females are fertilized and eggs are released

what does an infection of Trichuris trichura result in?

tissue injury = inflammation

secondary bacterial infection

hemorrhage

pain

loss of appetite

what does a heavy infection of Trichuris trichura result in?

anemia (resulting from hemorrhage)

dysentery (blood in stool)

fever (infection where worms are sewn into intestine)

rectal prolapse (because of the feeling of needing to go to the bathroom constantly)

how can you diagnose Trichuris trichura?

eggs in your stool

fecal smear

proctoscopic exam

colonoscopy

eggs barrel shaped with plugs on the end

what is the treatment of Trichuris trichura?

mebendzole - blocks the uptake of glucose

how can you prevent Trichuris trichura?

sanitary disposal of feces/night soil

personal hygiene

what is the life cycle of Ascaris lumbricoides?

eggs are ingested and will hatch in the small intestine in which it will penetrate the small capillaries getting into circulation until they get to the lungs

their diameter is about the same as alveoli sacs there - once there they will molt their cuticle (about 4 times total) and molting fluid will be released (which is highly allergenic to most people) and an allergic reaction will occur

after the molting process is complete and they are an adult they will make there way back up the trachea in which you will swallow and reside the rest of their life (typically) in the small intestine

what is unique about the eggs of Ascaris lumbricoides?

they are very resistant to the environment (desiccation and drying out) because they have a thick wall which allows them to survive for a few weeks without being ingested

what is the epidemiology like of Ascaris lumbricoides?

very common infection

warm/moist environments (southeastern US, central and south America, Asia - especially China)

what is the pathology and clinical manifestations of Ascaris lumbricoides in the lungs?

petechial hemorrhage will occur (small pinpoint hmorrhages in a blood vessel/capillary) - if there is enough larvae and enough cells/fluid is coming out it will lead to sero-cellular exudate

cough

allergic reaction to the molting fluid - can be life threatening (anaphylaxis) and cause asthma like symptoms (breathe in but not out)

what is the pathology and clinical manifestations of Ascaris lumbricoides in the small intestines?

they reside in the lumen of the gut so there is no pathology/tissue damage

they swim against peristaltic movement

what are some abnormal/dangerous outcomes of Ascaris lumbricoides?

intestinal obstruction: large infection and environment changes

appendicitis: worms gets into the appendix and causes an infection

abnormal migrations to the pancreatic duct, bile duct, esophagus, mouth, ears, and nose

trachea and lungs

gut penetration: worm could push its way through the intestinal wall and into the peritoneal cavity in which a secondary infection will occur

how do you diagnose Ascaris lumbricoides?

eggs in stool

fecal smear (female produces a lot of eggs so it will be visible)

clinical signs and symptoms (abnormal migrations, appendicitis, intestinal obstruction, gut penetration, etc.)

what is the treatment for Ascaris lumbricoides?

albendazole (prevents glucose uptake)

what is the prevention for Ascaris lumbricoides?

sanitation/night soil disposal

wash food

personal hygiene

what are four intestinal nematodes that are infective in the larval stages?

Necator americanus (hookworm)

Ancylostoma duodenale (hookworm)

Trichinella spiralis (pork worm)

Stronglyoides stericoralis (thread worm) (just know species in general)

what are characteristics of Necator americanus?

american killer

new world

produces less eggs than Ancylostoma duodenale

semi-lunar cutting plates

started in Africa and was brought over during slavery

what are characteristics of Ancylostoma duodenale?

old world

produces more eggs than Necator americanus

fangs or teeth

started in Europe and went to Asia on the silk road/trade route

what are physical characteristics of hookworms?

the male worm has something on the back called a bursa (like hooks) that they use to hold onto the female

what is the special about the pathology of hookworm like?

it doesn't cause a lot of mortality (death) but it is going to cause a lot of morbidity

a lot of the morbidity is due to anemia because they are blood feeders

what is the life cycle of hookworm?

it can live from 3-5 weeks before penetrating the skin a human and live on blades of grass waiting to attach to someone

it is typically going to penetrate the skin (foot) at a hair follicle and enter the circulation until it gets the lungs

once it gets to the lungs you will cough it up and swallow in which it will move to the small intestine

once in the small intestine it is going to hook onto portions of the wall and take in all the fluid - it will continue the process throughout the small intestine

what is the epidemiology of hookworm?

tropics and subtropics

some mixing of the different types of hookworms due to population migrations

temperature and rainfall are important

all ages are susceptible

where is most of the pathology and damage going to occur with hookworm?

intestines

what is the pathology and clinical manifestations of hookworm on the skin?

papule (hard red bump) --> vesicle (fluid reservoir under skin) --> lesion (breaking open of vesicle)

puritis - extreme itching which can lead to secondary bacterial infections and rash

edema

erythema

repeated infections can cause an allergic reaction - hypersensitivity - "ground itch"

what is the pathology and clinical manifestations of hookworm through larval migrations?

skin --> circulation --> lungs --> intestine

circulation: larvae enter circulation in skin and "break out" of blood vessel capillaries in lungs

lungs: petechial hemorrhages; small pinpoint lesions; bleeding of the lungs

what is the pathology and clinical manifestations of hookworm in the intestines?

they are going to take in a portion of the intestine and take in all of the fluid - eventually that area will get dry and it will release and reattach at another area (attachment/reattachment damage)

petechial hemorrhages

increase in worms = increase in blood loss

anemia = iron deficiency occurs = "pica" - the urge to eat dirt

for individuals who have had it their entire life they have mental and physical stunting (cardiac problems - enlargement of the heart)

how can you diagnose hookworm?

eggs in stool

what is the treatment for hookworm?

albendazole/mebendazole - preventing glucose uptake

reinfection is up to 80% after 36 months

education - explaining the life cycle

how can you prevent hookworm?

sanitation and proper disposal of feces

proper treatment of night soil

personal hygiene

shoes (Rockefeller foundation)

education

what are two cutaneous larval migrans/migrations?

"creeping eruption"

Ancylostoma canium (dog)

Ancylostoma braziliensis (cat)

what is the lifecyle like of Ancylostoma canium/braziliensis?

pets are a source of eggs

filariform larvae are going to penetrate the skin and migrate subcutaneously

they don't leave the skin - life cycle remains subcutaneous

parasites cannot complete their life cycle since they are in the wrong host

what is the pathology and clinical manifestations of Ancylostoma canium/braziliensis?

tissue damage where the parasite is moving around - as it moves metabolites are released so inflammation is going

the real reaction occurs because of your body's reaction to the larva

early lesion - edema and inflammation

late lesion - puritis, scab forms, crusty covering

how can you diagnose Ancylostoma canium/braziliensis?

observation

what is the treatment for Ancylostoma canium/braziliensis?

thiabendazole cream