26. Arthropods (fleas, part 2)

Question 1

do fleas have wings?

Answer 1

no

Question 2

what shape are fleas?

Answer 2

oval

Question 3

what is specially adapted in fleas?

Answer 3

the hind legs to enable them to jump long distances

Question 4

what is morphologically different about a fleas head?

Answer 4

it is disproportionally small

Question 5

how many species of fleas exist?

Answer 5

over 2000

Question 6

in which direction are fleas bodies compressed? why is this helpful?

Answer 6

laterally, so they may move through the feathers and hairs on the hosts body

Question 7

what are fleas mouthparts adapted for?

Answer 7

piercing skin and sucking blood

Question 8

what do fleas require?

Answer 8

a blood meal

Question 9

what color are fleas?

Answer 9

light to deep brown in color

Question 10

why are fleas of clinical significance to humans?

Answer 10

because they are vectors for many other diseases

Question 11

what kind of infections do fleas transmit to humans and other animals?

Answer 11

• bacterial
• viral
• protozoan
• helminth

Question 12

what are examples of the bacterial infections transmitted by fleas?

Answer 12

Fleas have helped cause epidemics by transmitting the bubonic plague between rodents and humans by carrying Yersinia pestis bacteria

Question 13

what are examples of the protozoan infections transmitted by fleas?

Answer 13

Trypanosome protozoans such as those of the subgenus Herpetosoma, use a variety of flea species as vectors

Question 14

what are examples of the helminth infections transmitted by fleas?

Answer 14

fleas are intermediate hosts for tapeworms, including the cestodes Hymenolepis and Dipylidium

Question 15

what are the life cycle steps of fleas?

Answer 15

• eggs
• larvae
• pupae
• adults

Question 16

who sheds the flea eggs into the environment? (male/female)

Answer 16

the female

Question 17

do fleas multiply rapidly or slowly?

Answer 17

rapidly

Question 18

what are the four main species of fleas that infest humans?

Answer 18

• Cat flea (Ctenocephalides felis)
• Dog flea (Ctenocephalides canis)
• Human flea (Pulex irritans)
• Oriental rat flea (Xenopsylla cheopis)

Question 19

why are Ctenocephalides spp. of medical importance?

Answer 19

they are vectors of rickettsial diseases - example Rickettsia typhi

Question 20

what are the three groups that Rickettsia is classified into?

Answer 20

• spotted fever
• typhus
• scrub typhus

Question 21

what can Ctenocephalides spp. serve as an intermediate host for?

Answer 21

tape worms, including Hymenolepis and Dipyladum

Question 22

what are morphological characteristics of Ctenocephalides felis?

Answer 22

Similar to the dog flea, except:

1. head is elongated,
2. front comb (ctenidia) is almost as long as the rest of the combs.

Question 23

what are morphological characteristics of Ctenocephalides canis?

Answer 23

Similar to the cat flea, except:

1. head is strongly rounded,
2. front comb (ctenidia) is half the size of the rest of the combs.

Question 24

which species does the Pulex irritans infect?

Answer 24

humans

Question 25

what is different about the head of the Pulex irritans flea of humans?

Answer 25

Head without ctenidia (i.e. comb structures).

Front head smoothly rounded.

Question 26

is Pulex irritans an efficient vector of flea-borne diseases?

Answer 26

no, this species is not an efficient vector of any flea‐borne diseases, but its bite can cause allergic reactions due to salivary proteins

Question 27

what is the vector of Yersinia pestis (bubonic plague)?

Answer 27

Xenopsylla cheopis

Question 28

in North America, what us the cycle of plague?

Answer 28

Xenopsylla cheopis and prairie dogs

Question 29

what is a form of typhus transmitted by Xenopsylla cheopis?

Answer 29

Murine typhus, also called endemic typhus

Question 30

what organism is Murine typhus in contrast to? what is that transmitted by?

Answer 30

epidemic typhus, which is transmitted by lice

Question 31

what is the rat flea?

Answer 31

Xenopsylla cheopis

Question 32

what is characteristic about the head of the rat flea?

Answer 32

Head without ctenidia (i.e. comb structures)

Front head rounded

Question 33

how can the itching assiciated with flea bites be treated?

Answer 33

with anti-itch creams, such as antihistamines or hydrocortisone

Question 34

what is critical to flea survival?

Answer 34

humidity

Question 35

why is humidity key to flea survival?

Answer 35

eggs need relative humidity of at least 70–75% to hatch, and larvae need at least 50% humidity to survive

Question 36

what temperatures are characteristic for flea life?

Answer 36

• fleas thrive at higher temperatures, but need 21°to 32°C to survive.
• lower temperatures slow down or completely interrupt the flea life cycle

Question 37

what would interrupt the flea life cycle?

Answer 37

Using dehumidifiers with air conditioning and vacuuming will interrupt the flea life cycle