Final exam Flashcards
Myxozoa
Myxobolus - causative agent of Whirling disease
infection of cartilage in the nervous system impairs neurological function. Hooked spore is either ingested by the fish by the fish eating the annelid OR the hooked spore in the environment pentrates the skin of the fish.
The action plan for whirling disease containment was:
Education - educating the public how to prevent the spread (ie. thoroughly clean boats bw different bodies of water)
Mitigation to prevent spread - testing for whirling disease in fisheries - quarantine until tested negative
Precautions to reduce spread - thoroughly cleaning and drying anything that comes into contact with one body of water before introducing it to another body of water. Properly dispose of all fish parts.
Echinostoma
Classical Trematode Example
Requires water. 2 intermediate hosts required. Humans (and dogs, rodents, etc) serve as the DH and they are infected by eating an infected secondary IH (raw frog, fish, clams). The excyst in the DH, develop in adults, and produce eggs that are released in the feces. Feces then contaminate the water and lifecycle recontinues.
Causes intestinal upset.
Schistosoma
Trematode
Humans can get schistosomiasis by getting penetrated by schistosome larvae in water. These flukes infect the liver and consume whole blood when travelling through the blood stream.
Diagnostic stage: eggs in feces or urine
Infective stage: cercariae in the water penetrate human skin (no metacercariae stage)
Water is required for this life cycle
Dicrocoelium
This is a terrestrial parasite that infects ruminants and can infect humans.
The eggs are released in the feces of the DH, are eaten by the mollusc intermediate host, cercariae develop within (and have multiplied) and are released from the snail in a slime ball. Ants will then eat the slime and cercariae. Metacercariae will form within the ant and some metacercariae will change the behaviour of the ant host, making it more likely to get grazed upon by ruminants. In the ruminant or human, larvae will excyst and develop into adults. Eggs released in the feces of the DH.
Pathology: Liver/bile duct
Echinococcus
Platyhelminth - Cestode - Tape worm
All stages are transmitted via the food chain. Humans can get echinococcus by the accidental ingestion of echinococcus eggs.
Eggs in feces of DH, consumed by rodents, sheep, goats, humans etc, oncosphere hatched from the egg, hydatid cysts form in the liver/lung (fatal), dog/canid ingests the cysts when they eat their prey, tapeworm develops in the DH and eggs are produced in the feces. The eggs are highly resistant and can remain viable on land for extended periods of time.
Taenia
Eggs/gravid proglottids produced in the feces of the DH, in the environment, pigs/cows/fish eat vegetation contaminated with eggs/gravid proglottids. oncosphere hatches from the egg, migrates to muscle, develop into cystercerci. Human/ carnivore eats undercooked/raw meat and gets a tapeworm in the intestine.
Really important to fully cook meat. Humans can also be infected by accidentally eating the eggs. Here, they would develop cysticercosis - significant pathology can be caused here.
Dracunculus
Tissue-dwelling. Nematode -aka guinea worm.
L1 larvae are released from the skin of humans (or dogs) and are ingested by copepods. Larvae develop from L1-L3 within the copepod. Humans can either get infected by drinking water contaminated with infected copepods or by eating a paratenic host (undercooked or raw fish, frogs) that houses L3 larvae within copepods. Adults develop in the DH and the female migrates to the surface of the skin - larvae cause blistering and are released into the water.
Requires water!
Trichinella
Nematode transmitted via the food chain (no free-living stages). This parasite enters a muscle cell (intracellular) and changes it to a nurse cell that protects and nurtures it.
Humans get by ingesting (undercooked) infected meat (pig/polar bear, bear). In this meat, there are larvae encysted within the striated muscle of the meal. Upon ingestion, the larvae are released from the cysts and invade the intestinal mucosa where they develop into adults. The females than produce larvae which migrate the striated muscle to encyst. This cycle repeats with the current host is eaten by another host.
Pathology: intestinal upset, fatigue, weakness. fever
Does not need water!
Ascaris
Gut-dwelling, non-blood feeding nematode with highly resistant eggs (soil transmitted).
Definitive host (human/pig) ingests eggs accidentally (contaminated fruit, not washing hands etc), larvae hatch and migrate to lungs, coughed up and swallowed, develop into adults in the intestine, eggs released in the feces.
Pathology - intestinal upset maybe. not severe unless there is severe infection
Does not require water!
Heligmosomoides polygyrus
Gut-dwelling, non-blood feeding nemotode
Rodents are the DH. Accidentally ingest L3 infective larvae. L3-L4- Adult inside the intestine (mucosa/lumen) - adults curl up and hold onto the villi in the duodenum. Eggs produced in the feces. Eggs - L1- L2-L3 occurs in the environment.
Does not require water!
Haemonchus contortus
Blood-feeding, gut dwelling nematode. L3 larvae are consumed by ruminants in the pasteure. Develop in L4 and Adult in the abomasum. They hangout in the intestine, but they use a lancet-like structure to pierce through the gut wall and access the blood supply. Eggs passed in the feces of the ruminants. Egg - L1 - L2 - L3 occurs in the feces/soil.
This can cause extreme problems on the farm and anti-parasitic resistance is becoming a huge problem. Cause anemia in ruminants (cow/sheep) and can cause death if the infection is severe.
Ancylostoma
Gut-dwelling, blood-feeding nematode
Human hookworm. L3 larvae penetrate the skin of humans. They then migrate to the lungs (L3-L4) - coughed up and swallowed. Develop into adults in the gut. The adults hook onto the gut wall and feed on the blood. Eggs are released in the feces.
Can cause anemia, and is especially severe when combined with malaria.
All of the gut-dwelling nematode infections are diagnosed by taking a fecal sample
Wucheria bancrofti
Filarial nematode - vector transmitted. Causative agent of elephantiasis
Mosquito takes a blood meal and injects L3 infective larvae into the human host. The larvae migrate into lymphatics and develop into adults. Adults produce microfilariae that block up lymphatic vessels and cause tissue swelling and inflammation. The microfilariae migrate into the peripheral blood only at night when they are most likely to encounter mosquitos vectors. Mosquito takes a blood meal and ingests microfilariae. They develop into L3 within the mosquito.
Onchocerca
Filarial nematode that uses blackfly vector.
Black fly takes a blood meal and injects L3 larvae into the human host. Larvae travel into the subcutaneous tissues where they develop into adults. Adults produce unsheathed larvae which migrate into skin, urine, lymphatics, blood stream. Black fly takes blood meal and ingests microfilariae. Microfilariae develop into L3 infective larvae within the black fly.
Can cause intense skin rashes.
Onchocerca infection is the causative agent of river blindness. The microfilariae can migrate into vessels surrounding the eyes. Ivermectin has been particularly effective in the fight against onchocerca. However, anti-parasitic resistance is an ever-evolving issue.
Plasmodium
Apicomplexan Protozoan. Causative agent of malaria.
Mosquito takes a blood meal and injects sporozoites into the blood stream of a human. Sporozoites infect the liver and become schizonts with hypnozoites. Schizont ruptures and merozoites are released into the blood stream - invade red blood cells and develop into trophozoites. Trophozoites can then either become schizonts are they can become gametocytes. Gametocytes are ingested by the mosquito when it takes a blood meal. Microgamete enters macrogamete and oocyst forms - Sporozoites form within the oocyst - oocyst ruptures and releases the sporozoites. The sporozoites get introduced into the human with the mosquito takes its next blood meal.
Cause anemia, fever, intestinal upset. Cause a lot of deaths.
Toxoplasma
Apicomplexan protozoan. Infected feline (DH) has fecal oocysts present in the feces. Rodents/birds/any mammalian IH will ingest the cysts by ingested contaminated water, plant material or soil. Oocysts develop into tachyzoites (fast replicating parasites) which then transform into bradyzoites (slow replicating cysts) present in the neural and muscular tissues. These cysts are consumed when the feline DH consumes the IH. The cysts present in the rodent brains can cause altered behaviour - they rodents will actually seek out their predators, making it more likely that they will get consumed.
Causative agent of toxoplasmosis.
Pathology. This parasite is generally not causative of any symptoms in its slow replicating form. It can remain in the body in this form for long periods of time. However, if the person becomes immunosuppressed, it can return the the fast-replicating state.
More harmful for pregnant and immunocompromised idvls
Cryptosporidium
Apicomplexan, protozoan
Infects mammals and produces a tiny, resistant cyst which can contaminate water supplies.
A thick-walled oocyst is ingested by the host (accidentally) ie. contaminated water at a park or contaminated food. Excystation in host - sporozoites infect epithelial cells of the lung and the gut. Asexual multiplication occurs and then micro and macrogametes are eventually formed that eventually forms the oocyst. The oocysts then sporulate. The oocysts can be thin or thick-walled. Thin = autoinfection. Thick = environment
Cryptosporidiosis can be quite debilitating. Cause severe diarrhea, dehydration, vomiting. Can cause death if there is no medical intervention. Transmission most commonly occurs in public water that is contaminated. Doesn’t require water but uses it. Infects calves as well.
Transmission is aided by moistness/water and high density of hosts
Entamoeba
Protozoan - Amoeba
Most common in areas of low sanitation
Can be inert but can also cause insane ulcers
Mature cysts are ingested by humans> excystation> trophozoites result - they live in the gut lumen and multiply. Trophozoites then encyst and are released in the feces of the host.
Humans get by accidentally ingesting the cysts (water-borne)
Pathology - severe ulcers in the gut - lead to entamoeba entering the blood, can cause death. Causative agent of amebiasis
Leishmania
Vector-transmitted - sandfly
Sandfly takes a blood meal and introduces promastigotes into the human. Promastigotes are phagocytised by macrophages and they then turn into amastigotes. Amastigotes multiply within cells of various tissues. Sandfly takes a blood meal and ingests macrophages infected with amastigotes. Within the sandfly, the amastigotes develop into promastigotes. Sandfly takes another blood meal and infects promastigotes into the human again. Can lead to anemia and even death
Infect the immune cells of mammals. Several types of leishmania - most common is the skin one - causes skin sores.
Trypanosoma brucei
Trypanosoma - Protozoan (flagellate)
Causative agent of African sleeping sickness. Vector = tsetse fly. Tsetse takes a blood meal from a human and injects metacyclic trypomastigotes into human. They then transform into blood stream trypomastigotes in the blood stream and migrate around the body - multiply in the blood and migrate to other fluids. Tsetse fly takes a blood meal.
T. brucei infection eventually leads to infection of the nervous system and brain and is always fatal if it is not treated
Trypanosomes swim freely in the blood, absorbing molecular constituents
Trypanosoma cruzi
Vector = triatomine bug. Causative agent of Chagas’ disease.
Triatomine takes a blood meal, then passed metacyclic trypomastigotes in feces and into the bite wound. Metacyclic trypomastigotes then infect cells around that site and transform into amastigotes
Amastigotes than multiply within cells. They then transform into trypomastigotes, burst out of the cell into the blood stream. These can than go on to infect more cells. Triatomine bug takes a meal and ingests trypomastigotes. Become epimastigotes and then metacyclic trypomastigotes. Triatomine bug takes a blood meal.
Eventually leads to the invasion of the heart and the GI tissues. Can be fatal.
Trypanosomes swim freely in the blood, absorbing molecular constituents
Giardia
Protozoan - flagellate, possess sucking discs.
Causative agent of giardiasis.
Humans accidentally ingest cysts. This can be from the contamination of water, fruit, vegetables, etc. Cysts release trophozoites following excystation in the gut. The replicate in the gut where they can be attached to the host or just float. They feed off lumen contents. They can end up covering a fair amount of the intestine and therefore cause absorption problems. ie. cause dehydration, weightloss, diarrhea. They can then encyst in the colon and exit the body in the stool. Only cysts survive in the environment (not trophozoites)
Cysts can survive in soil or in cold water. ie. Water is not required.
Ticks
Female gets fertilized and lays eggs. Larva hatches from the egg. Larva molts to a nymph. After several molts, nymph becomes an adult
Have flattened bodies that allow them to deter being groomed off but have legs designed to allow them to grasp their host
Dermacenter and Ixodes. Infect mammals and can cause quite sufficient blood loss. They ingest blood from multiple different animals/hosts throughout their lifeycle and therefore make great vectors for diseases like lime disease and Rocky Mountain spotted fever. After they leave a host, they molt to the next stage in their life cycle.
Mites
Female gets fertilized and lays eggs. Larva hatches from the egg. Larva molts to a nymph. After several molts, nymph becomes an adult
Sarcoptes - Causative agent of human scabies. These burrow in the superficial part of the skin and create scabbing. Adults can be transferred from human to human. Eggs are laid in pouches within the skin
Psoroptes - causative agent of psoroptic mange - prevalent disease in cattle, horses, sheep - leads to large economic losses.
Lice
Often highly specific for a certain type of hair. They move by host to host via crawling.
They feed on blood and tissue fluids. Not usually very severe pathology but can get itchy and then infected if scratched. They are easily transmitted from host to host and therefore make good disease vectors (typhus and relapsing fever)
It is the adults that get transmitted from human to human. They can lay eggs on the host (diagnostic stage)
fleas
Legs are well-developed and allows them to jump from host to host. Mouth parts designed for feeding and sucking.
Pulex - Can be a vector of the plague in some parts of the world. Infects many types of mammals
Eggs (laid in host bedding, environment) - larvae - pupae - adult
Adults feed on blood.
fleas can act as parasites, intermediate hosts, and/or vectors,
What is a mechanical vector?
A mechanical vector is a vector that transports a parasite, but the parasite does not use the vector as a host
Not-essential
What is a mechanical vector?
A mechanical vector is a vector that transports a parasite, but the parasite does not use the vector as a host
Not-essential, TRANSPORT
What is a biological vector?
A vector that is essential to the life cycle of a parasite. Organism in which the parasite develops and uses to get to its next host.
