Parasites Quiz 2

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Questions and Answers

What is the specific pathology associated with Fasciola hepatica infection?

Gallbladder calcification

Pipestem liver (correct)

Liver necrosis

Kidney failure

Which diagnostic method can be used to confirm a Fasciola hepatica infection in humans?

Blood culture

Bone marrow biopsy

Fecal antigen test (correct)

Skin biopsy

What is the primary symptom of an individual infected with Fasciola hepatica?

Joint pain

Bottle jaw (correct)

Blurred vision

Shortness of breath

In which part of the body does the metacercaria of Fasciola hepatica develop into an adult fluke?

Liver Signup and view all the answers

Which animal is NOT listed as a definitive host (DH) for Alaria Americana?

Lynx Signup and view all the answers

What is the stage in the life cycle of a trematode that is free-swimming and can encyst itself to become metacercaria?

Cercaria Signup and view all the answers

What is the defining characteristic of the Monogenea class within the Platyhelminthes phylum?

They lack an anus and use flame cells for waste removal Signup and view all the answers

Which of the following is an example of a Monogenean parasite that is not dependent on hooks for attachment?

Udenella spp. Signup and view all the answers

What is the primary way that Monogenean parasites obtain nutrients from their fish hosts?

They feed on the external epithelial cells of the fish Signup and view all the answers

What is the typical size range of Monogenean parasites?

2-3 cm Signup and view all the answers

Which of the following is a characteristic of the Gyrodactylus genus of Monogenean parasites?

They are viviparous, giving birth to live young Signup and view all the answers

What is the primary way that Monogenean parasites are transmitted between fish hosts?

They have a direct life cycle, reproducing within a single host Signup and view all the answers

Which of the following statements about vectors (ectoparasites) is correct?

Mosquitoes can transmit heartworms, which are parasitic roundworms. Signup and view all the answers

Which of the following statements about trematodes (digenean flukes) is incorrect?

They have a direct life cycle and do not require an intermediate host. Signup and view all the answers

What is the common name for the trematode Fasciola hepatica?

Both (a) and (b) Signup and view all the answers

Which of the following statements about trematode eggs is correct?

They are operculate, meaning they have a cap or lid for larva exit. Signup and view all the answers

Which of the following statements about trematodes is correct?

Their definitive hosts are typically predatory fish or sometimes birds. Signup and view all the answers

Which term describes a relationship where one organism benefits and the other is neither harmed nor benefited?

Commensalism Signup and view all the answers

What is the term used to describe a temporary host that is not required for the parasite's development but is used for transportation?

Paratenic Host Signup and view all the answers

In the life cycle of Toxoplasma gondii, which stage is responsible for the acute infection?

Tachyzoite Signup and view all the answers

Which term describes a parasite that lives outside the host's body?

Ectoparasite Signup and view all the answers

In the life cycle of Dirofilaria immitis (heartworm), which host is responsible for transmitting the larvae to the definitive host?

Mosquito Signup and view all the answers

What is the term used to describe the preferred site within the host that is optimal for the parasite's survival and avoidance of the host's immune system?

Predilection Site Signup and view all the answers

In the life cycle of Leucochloridium paradoxum, what is the role of the snail's eye tentacles?

To attract birds (definitive host) to eat the snail Signup and view all the answers

What is the term used to describe a state of arrested development in a parasite until environmental conditions improve?

Hypobiosis Signup and view all the answers

Which term is used to describe a parasite's presence in the host without causing disease?

-iasis Signup and view all the answers

What is the term used to describe a life cycle where the parasite only requires one host to complete its development?

Direct Life Cycle Signup and view all the answers

What is the size of Fasciola hepatica, the Trematode parasites?

4 cm Signup and view all the answers

Which of the following is NOT a location where the adult stage of the Trematode parasites can be found?

Skin Signup and view all the answers

What is the name of the condition caused by the cercarial stage of the parasite when it infects humans?

Swimmer's itch Signup and view all the answers

Which of the following is the intermediate host for the parasites in Phylum Acanthocephala?

Invertebrates Signup and view all the answers

Study Notes

Vectors (Ectoparasites)

Fleas and ticks are vectors that carry pathogens within their salivary glands, which are transmitted through bites.
Examples of vectors include:
- Ticks, which transmit Ehrlichia (Rickettsial bacteria genus) and Anaplasma phagocytophilum (bacteria that infect WBCs).
- Mosquitoes, which transmit heartworms (parasitic roundworms).
- Arachnids, including ticks and mites.
- Insects, including fleas (wingless flies), lice, and flies.

Trematodes

General information:
- Trematodes, also known as digeneans or digenean flukes, are endoparasites within the phylum Platyhelminthes.
- They have oral and ventral suckers, are dorso-ventrally flattened (leaf-like), and lack an anus.
- They use flame cells for waste elimination.
- They are hermaphroditic, but can cross-reproduce.
- They have no direct life cycle, but almost always use gastropods (snails) as intermediate hosts.
Examples:
- Fasciola hepatica, also known as the "common liver fluke" or "sheep liver fluke", is not zoonotic and is caused by a human-specific species found in Iceland.
- Deer ticks transmit Ehrlichia and Anaplasma phagocytophilum.

Monogenea Class (Phylum Platyhelminthes)

General information:
- Monogenea are ectoparasitic flatworms that lack a true body cavity or coelom.
- They live on the fins, skin, and gills of fish, and on the eyes of exotic animals like hippos, frogs, and reptiles.
- They have a simple digestive system with a mouth, pharynx, and intestines, but lack an anus and use flame cells for waste elimination.
- They are hermaphrodites that mostly produce eggs, but can be viviparous.
- They have poorly developed suckers and use hooks.
- They have a direct life cycle and are a problem in cage culture fish.
Examples:
- Udenella spp is the only monogenean that lacks hooks, and lives on copepods that live on fish, to get food from the fish (ectocommensal/hitchhiker relationship with copepods).
- Gyrodactylus is viviparous and very deadly, able to have multiple generations of parasites within one host.
- Benedenia seriolae infects amberjack fish and feeds on their external epithelial cells.

Fasciola hepatica

General information:
- Pathology: pipestem liver and chronic infection.
- Symptoms: anemia, bottle jaw.
- Diagnosis: fecal antigen test or fecal sedimentation in combination with symptoms.
- Size: 4cm, can be zoonotic.
Life cycle:
- Metacercaria (larval stage) burrows through the intestinal lining and perineal cavity.
- It then migrates through the intestines and liver through bile ducts, where it develops into an adult fluke.
- Intermediate host: freshwater snails in the family Lymnaeidae.
- Final host: ruminants.

Trematode Life Cycle

Simple life cycle:
1. Adult is within the final host (definitive host).
2. Egg is dropped into the environment and develops into a miracidium.
3. Intermediate host ingests the miracidium, which develops into a redia and then into a cercaria.
4. It is released into the environment as a metacercaria.
5. Final host eats the metacercaria from the environment.
6. Within the final host, it develops into an immature adult and then an adult.

Alaria Americana

Life cycle:
1. Cercariae penetrate the 2nd intermediate host, where they become infective metacercariae.
2. This is ingested by the paratenic host or definitive host (dog).
3. Within the definitive host, it develops in the lungs and then lives in the intestines.
- This trematode is specific to North America and commonly infects carnivorous mammals.
- It requires an intermediate host, and sometimes a paratenic host, which can be a coyote, skunk, dog, lynx, fox, bobcat, or marten.

Trematode Life Stages

Miracidium: penetrates snail/gastropod (intermediate host).
Rediae: developmental stage in the intermediate host.
Cercaria: free-swimming stage with flagella and can encyst itself to become a metacercaria.
Metacercaria: can be present in the 2nd intermediate host, paratenic host, or the environment.
Adults: typically found in the rumen/intestines, lungs, blood, or liver (bile ducts) and cause an inflammatory response.

Acanthocephala Phylum

General information:
- Acanthocephala, also known as thorny-headed worms, lack a mouth and digestive system.
- They absorb nutrients from the host's digested gut contents via their integument (skin).
- Size: 10cm.
- Sister group to rotifers (freshwater zooplankton).
- Intermediate host: invertebrates (always).
- Adults live in the digestive tract (small intestines) and are not typically pathogenic.
- Always have a complex life cycle and a broad spectrum of hosts.
Diagnosis: eggs in feces (sometimes sub-clinical).
Example: at RUSVM, cystacanths were found encysted within the muscle of mongoose and scrotum of monkeys.

Parasites

General information:
- Parasite: an organism that gets some or all of its food from the host, at the host's expense.
- Only the parasite benefits.
Epibiosis (phoresis):
- Two organisms that are nutritionally independent of each other have a facultative relationship together.
- Epibiont: smaller organism using another for transport.
- Basibiont: larger organism that carried the epibiont.
Commensalism:
- Small symbiont eats for/benefits from larger symbiont, which is neither harmed nor benefited.
- Example: flagellate eating unwanted bacteria off of fish.

Helminths

General information:
- Helminth: a general term used to describe worm-like parasites.
- Can be used to describe multiple unrelated phyla.
- Those that sexually reproduce tend to have longer life cycles.

Hosts

Intermediate host (IH): temporary host that is required for parasite development.
Paratenic (transport) host (PH): temporary host that is not required for parasite development and is typically just used for transportation.
Definitive host (DH): organism where the parasite reaches sexual maturity.
Final host: organism where the parasite reaches sexual maturity.
Aberrant (abnormal) host: infected organism that is not typically a host for that parasite, resulting in slow or incomplete parasite development.
Dead-end (incidental) host: intermediate host that is unable to transmit the parasite to the definitive host.

Toxoplasma gondii

Life cycle:
1. Sporogony (oocysts) within feces.
2. Intermediate host (human, mouse, mammal, or bird) ingests this.
3. Develops into tachyzoite (rapidly replicating stage that causes acute infection) or bradyzoite (slowly replicating stage that is a dormant cyst and causes chronic infection) within the intermediate host.
4. Cat (definitive host/final host) ingests either form via eating the intermediate host, and tachyzoite can turn into bradyzoite or vice versa while within the cat.

Nematode Lungworm

Life cycle:
1. Larva within cat (definitive host) feces is eaten by snail/slug (intermediate host).
2. Bird (paratenic host) eats the snail/slug.
3. Cat eats the bird, and the larva develops into an adult within the lungs and lays eggs.
4. Eggs turn into larvae and enter the cat's intestines, where they are defecated into the environment.

Parasite Life Cycles

Direct life cycle:
- AKA: simple life cycle.
- Parasite only has one host (the definitive host) to complete its life cycle, and only sexual reproduction happens within the definitive host.
- Life cycle only involves the definitive host and the environment.
- Host can be specific or broad spectrum.
- Example: nematodes within ruminants, and Toxocara canis within dogs.
Indirect life cycle:
- AKA: complex life cycle.
- Involved two or more hosts to complete their life cycle.
- Host can be specific or broad spectrum.
- Example: Dirofilaria immitis (heartworm) which requires a mosquito as the intermediate host and dogs as the definitive host.

Leucochloridium paradoxum

Life cycle:

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Monogeneans, Trematodes, Acanthocephala Parasitology terminology