Life Cycles

Question 1

what can knowing the life cycle help with?

Answer 1

-diagnose disease & ID parasite
-predict what pathogenic changes may occur
-optimize treatment to improve control
-develop environmental control programs
-reduce cross-species (including zoonotic) infections

Question 2

Define definitive (primary, principal, final) host

Answer 2

host in which the adult or sexually reproductive, stages of the parasite occur

Question 3

Define intermediate (secondary) host

Answer 3

host required for parasite development but in which the parasite does not become sexually mature

Question 4

Define paratenic (transport) host

Answer 4

host in which parasite does not undergo any required development but in which it remains alive & infective to another host

Question 5

what is included in a direct life cycle?

Answer 5

definitive host and no intermediate host

Question 6

define monoxenous parasite

Answer 6

parasites with direct life cycles

Question 7

what types of parasites are monoxenous?

Answer 7

nematodes and protozoa

Question 8

when might be the infective stage in a direct life cycle?

Answer 8

resting stage or active stage

Question 9

what are the modes of transmission of a resting stage in the direct life cycle?

Answer 9

ingestion

Question 10

what are the modes of transmission of the active stage in the direct life cycle?

Answer 10

ingestion, penetration of skin, direct contact

Question 11

what are two parasites with direct life cycles?

Answer 11

Ascaris suum and Hyastrongylus rubidus

Question 12

what is included in a indirect life cycle?

Answer 12

requires an intermediate host

Question 13

what type of life cycles do heteroxenous parasites have?

Answer 13

indirect life cycle

Question 14

what are some heteroxenous parasites?

Answer 14

trematodes, most tapeworms, and many parasitic nematodes, and protozoa

Question 15

when might be the infective stage in an indirect life cycle?

Answer 15

resting stage
active stage

Question 16

what are the modes of transmission in the resting stage of the indirect life cycle?

Answer 16

transmission via ingestion

Question 17

what are the modes of transmission in the active stage of the indirect life cycle?

Answer 17

penetration of skin, via vector

Question 18

what are two parasites with indirect lifecycles?

Answer 18

Spirurid nematode
Dirofilaria immitis

Question 19

Are paratenic hosts required for completion of parasites life cycle?

Answer 19

Not required, facilitates transmission to definitive host

Question 20

what is the paratenic host for Stephanurus dentatus (swine kidney worm)?

Answer 20

earthworm - carries infective larvae

Question 21

what are the 4 modes of transmission with Stephanurus dentatus?

Answer 21

-ingestion of free infective larvae
-ingestion of earthworm (paratenic host) carrying infective larvae
-penetration of skin by infective larvae
-transplacental transmission

Question 22

what ectoparasites serves as parasites and vectors?

Answer 22

arthropod ectoparasites

Question 23

what are the two main life cycles for ectoparasites?

Answer 23

-holometabolous (complete) metamorphosis
-hemimetabolous (incomplette, simple) metamorphosis

Question 24

Describe the holometabolous (complete) metamorphosis

Answer 24

egg -> larva -> pupa -> adult

Question 25

Describe the hemimetabolous (incomplete, simple) metamorphosis

Answer 25

egg -> larva -> nymph -> adult egg -> nymph -> adult

Question 26

what type of metamorphosis has larval that is morphological different from the adult?

Answer 26

holometabolous (complete) metamorphosis

Question 27

what type of metamorphosis has larval that is morphological similar to the adult?

Answer 27

hemimetabolous (incomplete, simple) metamorphosis

Question 28

what type of metamorphosis do fleas and dipterans have?

Answer 28

holometabolous

Question 29

what type of metamorphosis do tick, mites, and lice have?

Answer 29

hemimetabolous

Question 30

what type of metamorphosis is this?

Answer 30

hemimetabolous

Question 31

what type of metamorphosis is this?

Answer 31

holometabolous

Question 32

what is the mode of transmission of Dirofilaria immitis

Answer 32

vectored by moquitoes

Question 33

what is the infective stage of Dirofilaria immitis

Answer 33

third-stage larva, L3

Question 34

How does Dirofilaria immitis get from the mosquito into the host?

Answer 34

L3 migrates through mosquito bite wound

Question 35

What is the predilection site of the adult for Dirofilaria immitis?

Answer 35

pulmonary arteries, right ventricle

Question 36

what is the route to the predilection site for Dirofilaria immitis?

Answer 36

venous circulation (from subcutis and abdominal/thoracic muscles)

Question 37

what is the mode of exit of Dirofilaria immitis?

Answer 37

blood ingested by mosquito

Question 38

what is the exiting/diagnostic stage of Dirofilaria immitis?

Answer 38

Microfilaria in blood

Question 39

where is A. suum located in the pig throughout its life?

Answer 39

larva in lung tissue larva in large intestinal wall and liver (migrate up to lungs) larva in small intestine (prepatent week 6-8)

Question 40

what pathogen might have caused this?

Answer 40

A. suum

Question 41

Define prepatent period

Answer 41

time between infection of a definitive host and the appearance of stage exiting host

Question 42

how is the prepatent period controlled with A. suum?

Answer 42

control through deworming

Question 43

what is this a technique for?

Answer 43

collection of soil or vegetation samples to locate the different stages of the parasite external to host

Question 44

what can locating the different stages of the parasite external to the host help with?

Answer 44

epidemiology, environmental assessment, and control

Question 45

what environmental conditions that contribute to promoting development/survival of stage?

Answer 45

temperature, humidity, shade, etc.

Question 46

How does knowing the time required for development of stages and longevity of stages help with for parasite external to the host?

Answer 46

epidemiology, control ex. knowing what egg looks like that is infective vs non-infective

Question 47

what parasite mostly develops and reproduces in only 1 host species?

Answer 47

lice

Question 48

what parasite mostly develops and reproduces in more than 1 host species but are restricted to a genus or family of hosts?

Answer 48

most coccidia

Question 49

what is a parasite that develops and reproduces in more than 1 family or order of hosts?

Answer 49

Trichonstrongylus axei

Question 50

what are the definitive and intermediate hosts for Toxoplasma gondii - toxoplasmosis?

Answer 50

definitive hosts - felids intermediate hosts - mammals and birds

Question 51

what are the definitive and intermediate hosts for Schistosoma japonicum - schistosomiasis?

Answer 51

definitive hosts - rodents, carnivora, ungulates, primates, and other mammals intermediate hosts - snails in genus Oncomelania

Question 52

what are the definitive and intermediate hosts for Plasmodium reichenowi - malaria?

Answer 52

definitive hosts - mosquitoes in genus Anopheles intermediate hosts - chimpanzees

Question 53

what are the two main lifecycles for endoparasites?

Answer 53

direct and indirect