Micro Block 5 - Parasites Flashcards
Symbiosis
Two organisms of different species living together
Commensalism
Symbiotic relationship in which one organism is benefited and the other is neither benefited nor harmed
Mutualism
Symbiotic relationship in which both organisms are benefited
Facultative parasite
Normally free living organism, but may become an opportunistic parasite
Obligate parasite
Cannot survive in a free living state.
Incidental parasite
Establishes itself in a host in which it does not normally live (dog flea bites a human).
Endoparasite
A parasite living inside the host
Worm
Ectoparasite
A parasite living on the external
surface of the host
Mite
Definitive host
The host that harbors the adult or sexually reproducing stages of a parasite
Intermediate host
That host which harbors the immature, larval, or asexually reproducing forms of a parasite
Reservoir host
A host which replaces man in the life cycle of the parasite
Paratenic host
A host that serves as a transport host in which the parasitic forms undergo no development, but passes on to the final host
Autoinfection
A reinfection in which the host is its own source of infection from a source already present in the body
Which is a better environment for a trophozoite parasite?
Formed Stool
Loose Stool
Loose
Remains on or within the epidermis or subcutaneous tissues
Penetrates to other host organs or tissues
What route of infection does this describe?
Active Penetration
Through host tissues, skin or mucous membranes
Ex: Swimmers itch, mosquito bite
Entamoeba histolytica
can be transmitted how?
Fecal to oral and Sexually (Venereal)
[intenstinal protozoan]
Characteristics of protozoan taxonomy
- reproduce = binary fission
- facultative anaerobes
4 protist groups of human parasites
Opisthokonta
(protists as well as fungi and animals)
Amoebozoa •Excavata•SAR
What are the 7 intestinal protozoans?
Entamoeba histolytica
Giardia duodenalis/intestinalis
Dientamoeba fragilis
Neobalantidium coli
Cystoisospora belli
Cryptosporidium spp.
Cyclospora spp.
a cyst containing a zygote formed by a parasitic protozoan such as the malaria parasite
Oocyst
The only urogenital protozoa
Trichomonas vaginalis
Sexually TxM (Venereal)
Blood and Tissue Protozoa (7)
Naegleria and Acanthamoeba spp. Plasmodium spp. Babesia spp Toxoplasma gondii Leishmania spp. Trypanosoma cruzi T. brucei
Metazoan animalia parasites
- Helminths (“worms”)
* Arthropods (crabs, insects, ticks, and others).
Helminth Characteristics
- Complex multicellular organisms that are elongated and bilaterally symmetric.
- Often helminths possess elaborate attachment structures, such as hooks, suckers, teeth, or plates.
Two groups of helminths in humans
Nematoda and the Platyhelminthes.
clade consists of the flatworms, which have flattened bodies that are leaflike or resemble ribbon segments
Platyhelminthes.
Platyhelminthes. can be divided into
trematodes and cestodes.
The four major categories of arthropods of interest in human medicine are;
- Myriapoda(centipedes and millipedes).
- Crustaceans-Several are intermediate hosts in life cycles of various intestinal or blood and tissue helminths.
- Chelicerata- Mites, ticks, spiders, and scorpions
- Hexapoda.mosquitoes, flies, midges, fleas, lice, bugs, wasps, and ants.
Protozoan Food uptake
Pinocytosis,
Phagocytosis of soluble or particulate,
Ingestion through cytostome,
Diffusion.
Helminth Food uptake
Ingest host tissue/fluids
Absorption
Helminth energy conservation
primarily anaerobic, although the larval forms may require oxygen.
What species infect via ingestion
Giardia spp., Entamoeba histolytica, Cryptosporidium spp., cestodes, nematodes
What species infect via Arthropod bite
Malaria, Babesia spp., filaria, Leishmania spp., trypanosomes
What species infect via Transplacental penetration
Toxoplasma gondii
What species infect via Organism-directed penetration
Hookworm, Strongyloides spp., schistosomes
Attachment of the parasitic life cycle is based on what three things?
Mouthparts
Adhesins
Receptors
Interference Mechanism :
Antigenic variation
Variation of surface antigens within the host
Interference Mechanism :
Molecular mimicry
Microbial antigens mimicking host antigens, leading to poor antibody response
Interference Mechanism :
Concealment of antigenic site (masking)
Acquisition of coating of host molecules
Interference Mechanism :
Intracellular location
(3)
Inhibition of phagolysosomal fusion
Escape from phagosome into cytoplasm, with subsequent replication
Failure to display microbial antigen on host cell surface
Interference Mechanism :
Immunosuppression
(2)
Suppression of parasite-specific B-cell and T-cell responses
Degradation of immunoglobulins
What medications interfere with examining specimens
(a) Antacids
(b) Antidiarrheal compounds
(c) Mineral oil
(d) Antibiotics
What does water do to trophozoites?
Urine?
- Destroy them
- Immobilize them
One of the most important factors affecting the diagnosis of infections
Age of a stool specimen:
Should be examined within 30 minutes from time of passage (type of specimen where trophozoites may be found)
Liquid and diarrheic specimens:
Examined within one hour of passage
Soft specimens:
Formed specimens:
Can be delayed for several hours. If longer they should be preserved.
Fecal specimens may be stored at what temperature?
4 degrees C but not frozen
•Used to detect parasites, protozoa and helminths, in the upper part if the small intestine•Do not eat 12 hours prior to testing•The end of the string is taped to your cheek or neck
Enterotest-String Test
Pinworm Prep- Scotch Tape Prep
•This method gives best recovery of eggs if used before defecation, bathing or dressing in the morning•Firmly press the sticky side of tape to the skin around the folds of the anus
Do not use cloudy tape
Enteric Parasite panelsFor Giardia, Cryptosporidium, and Entamoeba require what kind of tests?
Nucleic acid testing
Specimens fro testing
•CSF•Skin scrapings•Biopsy•Serum•Bone marrow
Eosinophil characteristics
1-3% of peripheral blood
Bilobed nucleus
Cytoplasmic granules
Ways Eosinp. kill
1) Chemotaxis
2) Receptors
3) Phagocytosis
4) Granules
•It is best to collect multiple parasite specimens on the same patient on the same day.•True•False
True
Cestode characteristics
Flat, ribbon shaped
•All are hermaphrodites•
No digestive system
The head of cestodes is called
Scolex
•Individual segments are called ____________•A chain of proglottids is called a _________
Proglottids
strobili
Medically important cestodes
Taenia solium
Taenia saginata
Diphyllobothrium latum
Echinococcus granulosus
E. multilocularis
Hymenolepis nana
H. diminuta
Dipylidium caninum
Taenia solium
Africa, India, Southeast Asia
Eating undercooked pork
Indigestion, diarrhea
Diagnose T. Solium
stool exam
Cysticercosis
Involves infection of people with the larval stage of T. solium (the cysticercus), which normally infects pigs
Eating T. solium eggs
Diagnose Cysticercosis
imaging of calcified cysticerci, visualize after excision, CT/MRI. Serology
Taenia saginata
Worldwide, including the US•
Cause: Eating undercooked beef/limit exposure to human waste
ague abdominal pains, chronic indigestion, and hunger pains
Diagnose Taenia saginata
stool exam
Diphyllobothrium latum (fish tapeworm)
Large tapeworms (20 to 30 feet long)
Worldwide
Ingestion of this sparganum in raw or insufficiently cooked fish initiates infection.
Wider than they are long (≈8 by 4 mm), have a central uterine structure resembling a rosette,
What are fish tapeworm eggs like?
Eggs have an operculum and a knob on the shell at the bottom
How does fish tapeworm end up. in the fish?
In 2-4 weeks, the coracidium exits the operculum and is eaten by crustaceans and develops into a procercoid larval form.
The crustacean harboring the larval stage is then eaten by a fish, and the infectious plerocercoid, or sparganum larvae, develop in the musculature of the fish.
(The larval forms of several tapeworms closely related to D. latum (most often Spirometra species) )
Sparganosis
Sparganosis
Most prevalent Asia. Cold water lakes
Cause: drinking pond or ditch water that contains crustaceans (copepods) that carry a larval tapeworm. Eating raw tadpoles, frog, snake
Subcutaneous sites; painful inflammatory tissue reactions. In the eye, painful, with periorbital edema, possible corneal ulcers and ocular involvement
How do you diagnose Sparganosis
Surgical removal and sample looks like tapeworm.
Echinococcus granulosus
global,correlated with raising sheep
Cause: Human infection follows ingestion of contaminated water or vegetation, as well as hand-to-mouth transmission of canine feces carrying the infective eggs.
Slow growing (5-20 years). Pressure from cyst often first sign. Location dependent.
How do you diagnose Echinococcus granulosus
Imaging. Aspiration might confirm diagnosis, but high risk of anaphylaxis/dissemination. Serology, especially for hepatic cysts
Echinococcus multilocularis
Canada, Soviet Union, Japan
Adult tapeworms are primarily found in foxes and wolves,
Rodent intermediate hosts
Eggs hatch in and penetrate the intestinal tract to become oncospheres which enter the circulation and usually go to the liver and lungs but also possibly in the brain.
What can be mistaken for carcinoma and why
Echinococcus multilocularis
No protoscolices
Hymenolepis nana
Worldwide, North America
dwarf tapeworm
NO intermediate host
Poor hygiene, auto-reinfection
How do you diagnose Hymenolepis nana
Stool examination of H. nana egg with its six-hooked embryo and polar filaments.
Hymenolepis diminuta
Worldwide
primarily a tapeworm of rats and mice, but it is also found in humans.
The scolex lacks hooklets, and the egg is larger and bile stained and has no polar filaments.
How do you diagnose Hymenolepis diminuta
A characteristic bile-stained egg that lacks polar filaments
Dipylidium caninum
Worldwide children dogs / cats
Primarily a parasite of dogs and cats or direct swallowing the infected flea leads to intestinal infection.
Anal pruritus due to active migration of the motile proglottids.
rarely see free eggs
Diagnose Dipylidium caninum
Egg packets (microscopic)/ visible proglottids may be in feces
Two types of muscular suckers for trematodes
- oral type (beginning of an incomplete digestive system)
* ventral, which is an organ of attachment.
The only exception to trematodes being hermaphrodites
Schistosomes have cylindric bodies and separate male and female worms exist.
No operculum
Flukes require _______ ______ _____ ________ as the first intermediate hosts for the completion of their life cycles
mollusks (snails and clams)
What are the 5 medically signficant trematodes?
Fasciolopsis buski
Fasciola hepatica
Clonorchis (Opisthorchis) sinensis
Paragonimus westermani
Schistosoma species
Fasciolopsis buski (giant intestinal fluke).
Needs an appropriate snail host. China, Vietnam, Thailand, parts of Indonesia, Malaysia, and India.
the LARGEST, most PREVALENT, and most important intestinal fluke
Humans ingest the metacercaria encysted larva which develops into immature flukes in the duodenum.
The adult fluke attaches to the mucosa of the small intestine and undergoes self-fertilization.
Diagnose Fasciolopsis buski
Large, golden, bile-stained eggs with an operculum on the top
Fasciola hepatica sheep liver fluke
Australia, China, Egypt, Bolivia, Peru, and many other Latin American countries.
A parasite of herbivores (particularly sheep and cattle) and humans.
The larval flukes migrate through the liver parenchyma and enter the bile ducts to become adult worms
Some worms invade the liver to produce necrotic foci referred to as liver rot.
Diagnose Fasciola hepatica
Eggs in bile are diagnostic. Serlogy/ELISA
*hard to tell the difference between this and F. Buski
Clonorchis sinensis Chinese liver fluke
China, Japan, Korea, and Vietnam, Asian refugees
life cycle involves two intermediate hosts.
eggs are eaten by the snail, where reproduction begins
uncooked freshwater fish take up the cercariae encyst where it develop into infective metacercariae.
Diagnose Clonorchis sinensis
Distinctive eggs from stool. Repeat stool or duodenal aspirates may be necessary.
Eosinophilia elevated alkaline phosphatase
Paragonimus westermani Lung fluke
Asia, Africa, and Latin America. Southest Asian Refugees
from egg to snail to infective metacercaria.
The infective stage occurs in a second intermediate host: the muscles and gills of freshwater crabs and crayfish.
Adult worms reside in the lungs and produce eggs that are liberated from ruptured bronchioles and appear in sputum or, when swallowed, in feces
Diagnose Paragonimus westermani
Sputum and feces reveals golden brown, operculated eggs. Pleural effusions, when present, should be examined for eggs. Chest radiographs often show infiltrates, nodular cysts, and pleural effusion
Schistosomes
Tropical areas
•Male/female•No operculum•Obligate intravascular parasite
They develop in the portal vein, pair up and migrate to their final locations
The eggs hatch quickly on reaching fresh water to release motile miracidia. The miracidia then invade the appropriate snail host, where they develop into thousands of infectious cercariae. The free-swimming cercariae are released into the water, where they are immediately infectious for humans and other mammals.
Katayama syndrome
S. mansoni
Africa, Saudi Arabia, and Madagascar.
resides in the small branches of the inferior mesenteric vein near the lower colon.
oval, possess a sharp lateral spine,
Needs a suitable snail host. Swimming where they live
S. Japonicum(Oriental blood fluke)
China, the Philippines, and on the island of Sulawesi, Indonesia.
resides in branches of the superior mesenteric vein around the small intestine and in the inferior mesenteric vessels.
almost spheric, and possess a tiny spine
Needs a suitable snail host. Swimming where they live
Schistosoma Haematobium
Nile Valley and in many other parts of Africa,
blood fluke that develops in the liver and migrates to the vesical, prostatic, and uterine plexuses of the venous circulation, occasionally the portal bloodstream
Large eggs with a sharp terminal spine
Cercarial Dermatitis “swimmer ’ s itch”)
The natural hosts are birds and other shore-feeding animals from freshwater lakes
The intense pruritus and urticaria from this skin penetration may lead to secondary bacterial infection from scratching the sites of infection.
