parasitology lect exam 1

Parasitology

the study of a parasite and its relationship to its host (under symbiosis)

Symbiosis

the living together/ close union of two dissimilar organisms

What are the types of symbiosis?

Mutualism, commensalism, parasitism

Mutualism

(+, +) both organism’s benefit

Commensalism

(+,0) one organism benefits the other is unaffected

Parasitism

(+, -) one organism benefits and the host is harmed

What are the types of hosts?

Definitive,intermediate, transfer, vector, reservoir

Definitive host

supports the adult or sexually reproductive stage of a parasite necessary for parasite survival and life cycle completion

Intermediate host

supports the immature/ non-sexual reproductive forms of a parasite; may be asexual reproduction. Stage is necessary for parasite survival/ life cycle

completion. (Not all parasites have intermediate host)

Transfer host

can move or relocate parasite stages from one location another – most often reproductive stages such as eggs. Insects such as flies and cockroaches are good transfer host

Vector host

acts as a definitive / intermediate host for a parasite, and transfers the parasite to the next host. Example) mosquito in transmitting malaria and flies in transferring African sleeping sickness

Reservoir host

serves as a source of infection and potential reinfection of humans, and as a

means of sustaining a parasite within a population and ecosystem.

What are the types of host

parasite relationships? Exposure, colonization, infection, sign, symptom, incubation period, and latency

Exposure

being in contact with an infectious organism

Colonization

the presence of an infectious agent (bacteria) on / in a body surface (like on the skin, mouth, intestines or airway) without causing infection in the person

Infection

 the invasion and growth of infectious agents, germs on / in the body

Sign

a sign is any objective evidence of a disease that can be observed by others (for example a skin rash, lump, fever, pulse, blood pressure) – quantitative

Symptom

a symptom is subjective evidence of a disease, that is, apparent only to the patient (for example back pain or fatigue) - qualitative

Incubation Period

the time between exposure to an infection and the appearance of the first signs and symptoms

Latency

the time from infection to infectiousness or being able to pass the infection

What is the difference between infection and disease?

Infection- occurs when infectious agents that may cause disease enter the bsy via invasion and begin to multiply. 

Disease- occurs when the cells in the body are damaged due to the infection and are characterized by symptoms of illness/ pathological features.

What factors influence disease and pathogenicity?

 Infectivity, invasiveness, and pathogenicity

Infectivity

 ability of an organism to establish an infection

Invasiveness

 ability of an organism to spread to adjacent or distant tissues

Pathogenicity

 ability to produce substances that damage tissues, e.g., toxins

What are the different effects caused to hosts from parasites?

Utilization of host as food, and destruction of host tissues via feeding.

What is an example of a blood feeder?

Hookworms 250μl of blood per day causing destruction of host tissue

What is an example of hyper-reproductivity?

High rate of reproduction and is protected by a cyst that protects nuclei during rapid reproduction

Entamoeba histolytica

(induces tissue lysis  in the body), which has a rapid reproduction rate

Types of helminths?

Nematodes (roundworms),  Cestodes (tapeworms), Trematodes (flukes)

Where are hookworm (nematodes) found?

In the intestinal tract

What are the (nematodes) that can be located in blood and tissue?

Dracunculus medinensis (more pathogenic than intestinal parasites because they are in blood and tissues)

Cestodes (scientific)

Tapeworms (common) a type of helminth

What are the types of cestodes/ tapeworms found in tissues

 Taenia sp, Cystercercus cellulosae

What is the common name for trematodes?

Flukes

What is an example of a Trematode ( fluke) found in the intestinal tract?

Fasciolopsis buski

What is an example of a Trematode (Fluke) found in blood and tissue?

Schistosoma sp

Example of a parasitic protozoa?

Amoeba (sarcodina), Ciliates (Ciliata), Flagellates (Mastogophora), Sporozoans (Sporozoa)

What is an example of a Amoeba (sarcodina) in the intestinal tract and tissues?

Entamoeba histolytica

WHat is an example of Ciliates (Ciliata) found in the intestinal tract?

Balantidium coli

What is an example of Flagellates (Mastogophora)in the intestinal graft?

Giardia sp

What is an example of Flagellates (Mastogophora) in blood and tissues?

Trypanosoma gambiensis

What is an example of Sporozoans (Sporozoa) in blood and tissues?

Plasmodium sp. Causes malaria

What are some common nematodes that cause infection at the egg stage?

• Enterobius vermicularis – Pinworm (Intestinal life little worm)

• Trichuris trichura – Whipworm (Hairtail)

• Ascaris lumbricoides – Giant Roundworm

Enterobius vermicularis life cycle

 Pinworm normal life cycle includes (eggs ingested)-> larvae hatch in the small intestine-> they migrate to the colon where the adults mature-> the adults deposite the eggs on the perienum-> the eggs embryonate on the perienum (anus) and contaminate fingers to be ingested again. This mainly affects young children

What is the pinworm (Enterobius vermicularis) abnormal life cycle?

Migration from perianal area to Vagina Uterus Fallopian tubes and can make their way to the appendix

Abnormal symptoms of pinworms- 

• Vaginitis (Abnormal Life Cycle)- Migration to Vagina Migration to Fallopian Tubes Salpingitis Scarring of Fallopian Tubes

• Toxic metabolites- Nervousness Insomnia Irritability Convulsions
  
  

transmission of pinworms?

• Direct – Anus to mouth via fingers

• Indirect – Airborne eggs or fomites (inanimate objects that transmit eggs, example doorknob

Symptoms of pinworms-

• Large Intestines – Colon / Rectal area. Attachment Irritation Inflammation Pinpoint Necrosis

• Perianal Area - Area immediately surrounding anal opening Itching Scratching Bacterial    Infection Benign Tumors

• Appendicitis- Migration to appendix Irritation Bacterial Infection Inflammation

How are pinworms usually treated?

Mebendazole (Emverm) – blocks glucose uptake, affects metabolism, paralysis, expulsion treated once a day and is repeated in 3 weeks due to leftover eggs

Trichuris trichura – Whipworm (Hairtail)

a type of nematode which is infective at the egg stage has a typical life cycle by eggs ingested via mouth, the larvae hatch in the small intestine and travel to the large intestine (attach to the mucosa to feed on tissue) where the male and female Whipworms reproduce more eggs and travel to the rectum excreted through stool and the life cycle continues(prefer moist areas) can  also be treated with mebendazole. (barrel shaped eggs) can be found in the stool.

Ascaris lumbricoides

Giant Roundworm a nematode that causes infection at the egg stage(females larger than males),  has a typical life cycle by embryonated eggs ingested (have thick shell for protection) mos likely from contaminated soil,  and the larvae hatch in the small intestine and penetrate small capillaries in the small intestine giving them access to the circulatory system and where they break out in the lungs because there are fine capillaries in the lungs. When the larvae get to the lungs they break through the delicate capillaries to the alveolar sacs and migrate to the tracheal system and go up the bronchial tree and when the individual coughs, they are reswallowed and migrate to the small intestine for maturation where the adults reproduce and the cycle continues.

What are clinical manifestations of Ascaris lumbricoides?

 Typically treated with albendazole

(Lungs)- Petechial hemorrhage, Sero-cellular exudate, Cough, Allergic reactions to molting fluid. 

(Small Intestine)- Resides in lumen of gut – no pathology / no tissue invasion,  Swims against peristaltic movement of gut,  Feeds on intestinal contents (food you ingest not you), can cause intestinal obstructions, appendicitis, and can have complications from abnormal migrations

Typical anatomy of these nematodes?

 Males have curled tails and females are more straight

What types of nematodes are infectious at the Larval stage?

• Hookworm

o Necator americanus ( new world)

o Ancylostoma duodenal (old world\)

• Cutaneous Larval Migrans

o Ancylostoma canium- in dogs

o Ancylostoma brasiliensis- in cats

• Tricinella spiralis

• Strongyloides stercoralis

Neactor americanus:

type of (new world spread due to slave trade ) hookworm nematode infective at the larval stage

• American killer

• New World hookworm

• Female produces 5,000 to 10,000 eggs per day

• mouth: Lunar cutting plates

Ancylostoma duodenale:

 type of (old world silk road)hookworm nematode infective at the larval stage

• Crooked mouth

• Old World hookworm

• Female produces 10,000 to 20,000 eggs per day

• mouth: Fangs or teeth

What is  the typical lifecycle of the Neactor americanus, Ancylostoma duodenale hookworms?

The eggs enter the soil and hatch. The larvae emerge as rod-shaped rhabditiform larvae (chunky) where they revert to Filariform larvae (longer/thinner) where they enter the skin via the foot. The larvae move through the bloodstream to the lungs where they are coughed up and swallowed where the infection occurs in the small intestine (disrupt mucosal tissue to feed on blood) where adults mature (males have bursa, females larger) and reproduce more eggs.

Typical pathology of a Neactor americanus, Ancylostoma duodenale hookworm infection?

Larval Penetration - Skin (in order) 

o Papule, Vesicle,  Lesion,  Puritis - itching, Edema - swelling, Erythema - redness, Repeated infections can cause allergic reactions – hypersensitivity– “Ground itch

Circulation – Lungs – Intestine , o Circulation – Larvae

enter circulation in skin and “break out” of blood vessel capillaries

in lungs, o Lungs – Petechial hemorrhage, larvae coughed and swallowed can migrate to the small intestines

What is the general life cycle of Cutaneous Larva Migrans Infection with larval stages of Ancylostoma canium (dog) or Ancylostoma braziliensis (cat) hookworms?

Pets are source of eggs; filariform larvae penetrate skin and migrate subcutaneously. Parasites cannot complete their life cycle since they are in the wrong host (same life cycle as ascaris (Neactor and Ancylostoma in humans)

What are “creeping eruptions”?

Skin damage caused by the migration  of filariform larvae

What is the typical life cycle of  Trichinella spiralis (pork worm) an infectious nematode at athe larval stage?

 Ingesting the undercooked pork that has encysted larva in the striated muscle. This happens when the pig eats a rat and ingests the larva and then could infect humans when we eat them. Or can come from eating (omnivorous) wild animals.  Then the larvae are released in the small intestine and the male and female worms mate and give off live larvae where they penetrate the mucosa and enter the circulation and break into striated skeletal muscle forming cysts and lie dormant for years and are infective. The parasite multiplies in the host!!!

What muscles typically attract Trichinella spiralis (pork worm)?

Eye muscles, Diaphragm, Larynx ,Tongue, Intercostal, Biceps/Triceps/Pectorals

What is known as the great imitator and why?

Trichinella spiralis (pork worm) because it can cause nausea, vomiting, diarrhea, fever, and adults mature 1-10 days after ingestion and can cause necrosis,and panmucosal inflammation after 72 hrs and peaks after 8 days due to immune response from the body. The inflammation in the body removes the worms after 14 days from the small intestine. (stage 1). In (stage 2) 7-14 days the larvae migrate to the muscles in large numbers and can cause hemorrhages under the fingernails, swelling around the eyes, and a high number of eosinophils. In (stage 3) 3 weeks post infection – Larval encystment, Myositis – muscle inflammation,  Myalgia – muscle pain, Degeneration of muscle fibers. Then in (stage 4) the larvae in the striated muscle calcify and the symptoms dissolve. 

imitates the flu or food poisoning (hardest to diagnose)

stage 1- expulsion

stage 2- eosinophilia

stage 3- larval encystment

stage 4- larval calcification

What is the process of panmucosal inflammation in the small intestine?

 T. spiralis burrows in mucosa feeding and releases metabolites and larvae = foreign materials  Causes inflammation - infiltration of WBCs into intestinal tissues  Inflammation influences worms to

move to fresh tissue  Process repeats until worms run out of small intestine

Is this self cure expulsion beneficial to the host or the parasite?

Beneficial for both

What is the Strongyloides stercoralis (Thread worm) that is a nematode that is infective at the larval stage and what is its life cycle?

It has a complex life cycle broken down into the Direct, Indirect cycles, and Internal and external autoinfection.

Life Cycle – S. stericoralis in humans?

Rhabditiform larvae in the diagnostic stage from the intestine are excreted through stool. Then they can develop into the filariform larva which can directly infect humans or they develop into free living adult worms. They reproduce and make fertilized eggs where the Rhabditiform larvae hatch from the eggs and mature into the infective filariform larva. These filariform larva penetrate intact skin and enter the circulatory system where they are transported to the lungs and when the person coughs they are swallowed and make their way to the small intestine. The small intestine is where adult maturation happens. Then the adult female worms in the intestine deposit eggs in the intestinal mucosa where they hatch and the rhabitiform larvae are excreted again in stool where the cycle continues. 

Life Cycle – S. stericoralis (AUTOINFECTION) in humans?

Once the individual has the eggs deposited in their intestinal mucosa, instead of the larva being excreted in stool, the rhabditiform larvae can become infective filariform larva in the large intestine and penetrate the intestinal mucose making their way back into the circulatory system to the lungs to be swallowed where adults mature in the small intestine where the cycle can continue.

S. westeri can infect humans and S. stercoralis can infect horses!

New parasite – has a broad range of host – human worm is indistinguishable from infections in dogs, cats, horses all of which are possible reservoirs. Has a free-living cycle, multiple hosts, and high degree of pathology. In the intestine this can caise cavitation, dysentery, fluid/blood loss, mucosal sloughing, and bacterial infection. (NO EXPULSION CAN HAPPEN) during the autoinfection life cycle which can increase pathology!! 

What is the typical pathology of thread worms?

Can cause papules, vesicles, leasions on the skin, and petechial hemorrhaging of the lungs.

Blood and tissue parasites cause more pathology than

lumen dwelling parasites they are typically long and thin

T/F

True

What are the types of tissue nematodes?

Non-filarial worms:

• Dracunculus medinensis

Filarial (filamentous) worms – Live in the lymphatics or subcutaneous tissues

• Wucheria bancrofti

• Loa loa

• Onchocerca volvulus

What is the life cycle of Dracunculus medinensis – Guinea Worm, Fiery Serpent a type of tissue nematode?

 A human drinks unfiltered water containing copepods with L3 larvae. The larvae are released when the copepods die where the larvae penetrate the host stomach and intestinal wall for maturation and reproduction. Then the fertilized female worms migrate to the surface of the skin causing blistering 1 year after infection when the individual makes contact with water and discharges the (L1) larvae where they are released outside the body into water. Then the L1 larvae in water are consumed by copepods where the larvae undergo two molts in the copepod to become L3 infective larvae.

What is a common source of  Dracunculus medinensis – Guinea Worm?

Step wells that contain copepods. 

What is the pathology of   Dracunculus medinensis – Guinea Worm?

A lesion on the foot/ ankle, damaged knee joints, secondary bacterial infection, 

What is a type of filarial worm?

Wuchereria bancrofti –

Bancroft’s Filariasis or Elephantiasis

Wuchereria bancrofti – Bancroft’s Filariasis or Elephantiasis life cycle?

When the mosquito bites a person the proboscis has an anticlotting material and an anesthetic where the microfilaria come out in the saliva into the body from te puncture wound. They go into circulation and into the lymphatic system where the male and female worms mature. They mate and give off sheathed larvae that migrate to lymph and blood channels. Then if a mosquito bites a person it takes those larvae shed the sheath, and become L1, and L3 larvae and migrate to the mosquito head/ proboscis to become infective again to humans. (adult worms reside in lymphatic channels

What are the typical hosts of Wuchereria bancrofti – Bancroft’s Filariasis or Elephantiasis?

The intermediate hosts can be Mosquito vector – Culex, Anopheles, Aedes.

What is the pathology of Wuchereria bancrofti – Bancroft’s Filariasis or Elephantiasis?

70% are asymptomatic, adult worms cause no blockages, but minor swelling

25% acute filariassis, adult worms cause peri-endo lymphatic inflammation scarring, and lymphatic lumen narrowing

5% chronic filariasis:. Mainly cause by repeated infections, blockage of lymphatic circulation, hypersensitivity to worm allergens, severe periendolymphatic inflammation and scarring. 

What is the life cycle of Loa loa -eye worm, from the Chrysops sp – Deer Fly?

The Chrysops deer fly bites and transfers the larvae into the wound where the larvae become adults in the subcutaneous tissue then the adults mate and give off sheathed microfilaria found int spinal fluid where the fly bites an infected person the larvae are taken up and become L1, L3 larvae in the fly and become infective again where the cycle continues.

What is the pathology presented by Loa loa eye worm?

Worms move freely in subcutaneous tissue and can wander across the eye, they are attracted to warmth. They can form subcutaneous modules of entwined worms, and can cause calabar swelling.

What is the life cycle of Onchocerca volvulus – River blindness?

Caused by the vector Simuliun

Damnosum (blackfly) that bite and release larva into the subcutaneous tissues where the adults mature and produce (Unsheathed) microfilaria in the tissue wher the fly bites again and takes the larvae wher they go from L1 to L3 and migrate to flys proboscis to be infective to humans.

What is the pathology of   Onchocerca volvulus?

Can cause benign tumors of collection of worms. This can be in the groin area, eye, head. Migration of microfilaria larvae causes detached skin where it loses its elasticity and circulation. Can migrate across the cornea causing scarring 

exp) Hanging groin

What bacteria lives in the   Onchocerca volvulus?

Wolbachia bacteria which is endosymbiotic to the worm. This is why treating someone with ivermectin and an antibiotic can remove these worms.