Lecture 1

Question 1

What are the four types of symbiotic relationships?

Answer 1

Phoresis

Mutualism

Commensalism

Parasitism

Question 2

What is phoresis?

Answer 2

One organism being carried by another.

No physiologic dependency between the two species.

Example: bacteria being carried on the legs of a fly

Question 3

What is a mutualism?

Answer 3

Two organisms benefiting one another.

Both organisms are physiologically dependent on one another.

Example: rumen microbiome

Question 4

What is a commensalism?

Answer 4

One organism benefits from the relationship, while the other is neutrally affected.

Example: Cows and cattle egrets. The cow kicks up insects, from which the egret benefits. The cow is not affected by the presence of the egrets.

Question 5

Define parasitism

Answer 5

One organism lives in or on another. The parasite typically harms the host.

Question 6

How would you define an organism that must live a parasitic lifestyle or perish?

Answer 6

Obligate parasite

Question 7

How would you describe an organism that is an opportunistic parasite and can live without the host?

Answer 7

Facultative parasite

Question 8

Name the 3 major classes of “traditional” parasites

Answer 8

Protozoa

Helminths

Arthropods

Question 9

What is the term for the entry and multiplication of an infectious agent within the body of a host?

Answer 9

Infection

Endoparasites cause infections

Question 10

What is the term for an infectious agent reproduces on the surface or exterior of host tissues?

Answer 10

Infestation

Ectoparasites cause infestations

Question 11

What is an accidental parasite?

Answer 11

Infects an animal that is not its natural host.

Usually develops in a manner similar to that in its natural host.

For example, a human can be accidentally infected with heartworm.

Question 12

What is an aberrant parasite?

Answer 12

A parasite that has wandered to the wrong place in the host.

Can occur in the natural host, but usually occurs in an animal that is not the natural host.

Question 13

This heartworm is in the eye of a dog. How would you describe this parasite?

Answer 13

Aberrant parasite

Question 14

Define pseudoparasite

Answer 14

Any object or organism that is mistaken for a parasite.

Examples: Pollen grains, fungal spores, free-living nematodes.

Question 15

What is a spurious parasite?

Answer 15

Parasites that pass through the GI tract of non-host species and are mistaken for parasites of the non-host.

Example: Eimeria cysts normally infect large herbivores. When accidentally ingested by a dog, they will pass in the feces without infecting the dog. When found in the feces, they can be mistaken for a parasite of the dog.

Question 16

You find a free-living nematode in a stool sample. How would you describe this organism?

Answer 16

Pseudoparasite

Question 17

What characteristics define the definitive host in a parasite life cycle?

Answer 17

The host in which the parasite reaches maturity and, if applicable, reproduces. Typically a vertebrate.

For example, dogs are the definitive hosts of heartworms.

Question 18

What characteristics define a secondary host in a parasitic life cycle?

Answer 18

A host in which the parasite undergoes its larval or developmental stages.

Parasites may undergo metamorphosis in intermediate hosts. If reproducing in intermediate hosts, parasites usually do so asexually.

Question 19

Define paratenic host

Answer 19

A host in which a parasite remains viable, but does not undergo any further development.

Not essential for the completion of the life cycle.

Question 20

A tapeworm species uses fish as an intermediate host and mammals as a primary host. On occasion, a smaller fish can be consumed by a larger fish, which can in turn be consumed by a mammal and still cause infection. In this instance, how would you define the larger fish?

Answer 20

Paratenic host

Question 21

The malaria parasite Plasmodium falciparum undergoes asexual reproduction in the erythrocytes of its human hosts and sexual reproduction in the gut of its mosquito hosts. In this case, which is the definitive host and which is the intermediate host?

Answer 21

Mosquito is the definitive host

Human is the intermediate host

Question 22

What is a direct parasitic life cycle?

Answer 22

Parasite requires a definitive host, but does not require an intermediate host.

The parasite infects new definitive hosts through the environment.

Question 23

The nematode Trichostrongylus is a parasite of cattle. It matures in the gut of cattle, where it releases eggs that are passed in the feces. These eggs can be consumed by other cattle, causing new infections. What kind of life cycle is this?

Answer 23

Direct life cycle

Question 24

Define indirect life cycle.

Answer 24

The parasite requires at least one intermediate host in addition to its definitive host to complete its life cycle.

Question 25

The trematodes (flukes) must always infect a snail before they can infect the host in which they reproduce sexually. What kind of life cycle is this?

Answer 25

Indirect life cycle

Question 26

Define incubation period

Answer 26

The interval of time between the entry of an infectious organism into a host and the first appearance of clinical signs of disease in the host.

Usually shorter than the pre-patent period, but can be longer.

Question 27

Define the pre-patent period of infection

Answer 27

The time interval between entry of an infectious organism into a host and the first time we can detect the organism in the host.

Question 28

Define the patent period of infection.

Answer 28

The point at which we can demonstrate the detection of an infectious agent.

Question 29

A puppy acquires a new parasite, which begins to develop in its body. After a week, the puppy begins to have bloody diarrhea, so the owners take her to the vet. The vet does a fecal float, but does not detect any parasites. A week later, the owners return to the vet whereupon the vet detects eggs in the puppy’s stool. The owners opt not to treat. 6 weeks after the initial infection, the puppy’s symptoms resolve and parasites are no longer detected.

What are the incubation, pre-patent, and patent periods of this parasitic infection?

Answer 29

Incubation period: 1 week

-one week span from initial infection to when symptoms first appeared

Pre-patent period: 2 weeks

-two week span from initial infection to the point where the parasite could be detected

Patent period: 5 weeks

-five week span from when symptoms began to when symptoms resolved

Question 30

What is the difference between presumptive and definitive parasitism diagnoses?

Answer 30

For a presumptive parasitism diagnosis, we make a diagnosis based on factors other than physical detection of a parasite.

For a definitive parasitism diagnosis, we make a diagnosis based on detection of the parasite through direct (e.g. eggs) or indirect (e.g. an ELISA) methods.

Question 31

The symptoms of hookworm in puppies are well-known, and puppies often get this kind of infection. A puppy presents to you with symptoms of hookworm infection, and you decide to treat the infection based on the symptoms alone. What kind of parasitic diagnosis did you just make?

Answer 31

Presumptive

Question 32

Define ante-mortem vs. post-mortem diagnosis of parasitism

Answer 32

Ante-mortem diagnosis requires demonstration of a parasite in host tissues of a live animal.

I mean, duh.

Question 33

What is sub-clinical parasitism?

Answer 33

Parasites cause infection without causing clinical signs.

Can still reduce host productivity.

Question 34

What is clinical parasitism?

Answer 34

Parasites cause overt clinical disease

Question 35

What factors of parasitic infection affect the amount of damage done to the host?

Answer 35

Virulence and strain of parasite

Number of infective dose

Route of infection

Rate of acquisition of infection

Ability to multiply in host

Predilection site in host

Question 36

True or false:

Parasites can serve as vectors for other pathogens

Answer 36

TRUE

For example, helminths can harbor pathogenic bacteria.

Question 37

Define premunition

Answer 37

A state of resistance to re-infection that develops after an acute infection becomes chronic.

Note: premunition persists only as long as the infecting organsims remain in the body.

Question 38

List all of the veterinary parasites that have been eradicated.

Answer 38

None, suckas.

Question 39

Name an important method for controlling parasitic infections on a large scale.

Answer 39

Identify the weakest link in the parasite’s life cycle and attack it.

Sanitation

Vector control

Treatment of infected hosts

Question 40

Greg gets a parasite, but seems to be immune to further parasitic infection whilst the parasites are still in his gut. What is the name for this phenomenon?

Answer 40

Premunition

Question 41

Identify the binomial nomenclature that has been written correctly.

1) Homo Sapiens
2) Homo sapiens
3) Homo Sapiens
4) Homo Sapiens
5) Homo sapiens

Answer 41

2) Homo sapiens and 5) Homo sapiens

are correct. The generic (genus) name should always be capitalized, while the specific (species) name is always in lower case. When typing, italicize the name. When writing, underline the name.

Question 42

What kind of life cycle is pictured here (direct or indirect)?

Answer 42

Direct

Notice how there is no intermediate host in this life cycle.