Module 9c Mosquitoes Part 1

Question 1

mosquitoes characteristics

Answer 1

most important arthropod affecting human health

worldwide distribution

Question 2

mosquito taxonomy

Answer 2

Family Culicidae
Subfamily Anophelinae (Genus Anopheles)
Subfamily Culicinae (Genera Culex, Aedes, Psorophora, Mansonia)

Question 3

mosquito anatomy

Answer 3

slender, small, hairy
forward-pointing proboscis
presence of scales on body

Question 4

mosquito antennae

Answer 4

well developed
large pedicle (Johnston's sensory organ)
sexually dimorphic (males: bushy to find mate)

Question 5

mosquito mouthparts

Answer 5

proboscis forward-pointing (but males don’t feed on blood because they can’t pierce skin)

labium: sheath for fascicle, folds backwards during feeding
fascicle: labrum (food canal) and 5 stylets

Question 6

mosquito saliva

Answer 6

• salivary gland in thorax not head
• salivary channel: hypo pharynx - salivary duct - glands
• saliva contains anticoagulants, antihaemostatic enzymes (promotes bleeding), and anesthetic substances (reduces bite pain)

Question 7

blood feeding and reproductive cycle of mosquitoes

Answer 7

• females only mate once and store sperm in spermatheca
• anautogenous (need blood meal)
• gonotrophic cycle: blood fead, egg maturation, then oviposition (mating not part of cycle because only done once)

Question 8

mosquito adult biology and behavior

Answer 8

various strategies:

• day/night, diurnal, nocturnal, or crepuscular (twilight)
• endophagic vs exophagic (willingness to enter house)

Question 9

subfamily Anophelinae anatomy

Answer 9

• proboscis and abdomen in straight line at rest
• light and dark scales in blocks
• maxillary palpi as long as proboscis
• eggs laid singly, possess floats
• larvae never have siphon, lie parallel to water

Question 10

subfamily Culicinae anatomy

Answer 10

• proboscis/abdomen have angle at rest
• scales are all the same color or not in blocks
• maxillary palpi are much shorter than proboscis
• eggs laid singly or in egg rafts, never w/ floats
• larvae have siphon, lie at angle to water surface

Question 11

immature stages of mosquitoes

Answer 11

aquatic stages (lentic: stagnant)

• eggs laid on water or below vegetation
• larvae (X4) wigglers
• pupa (or tumblers) air trumpets

Question 12

subfamily Anophelinae characteristics

Answer 12

contains 3 genera but only Anopheles is of medical importance (vectors Filariasis/elephantiasis, malaria)
mostly crepuscular or nocturnal
either exo- or endophagic

Question 13

subfamily Culicinae characteristics

Answer 13

33 genera (but Culex*, Aedes*, Psorophora, Mansonia are most important)
can be major nuisances

Question 14

types of responses to mosquito bites

Answer 14

1. immediate: wheal and flare (type 1 hypersensitivity)
2. delayed: type IV hypers., cellular immune response
3. secondary infection

Question 15

Lymphatic filariasis / elephantiasis

Answer 15

parasite: filarial nematodes (Wuchereria bancrofti*, Brugia malayi, Brugia timori)
vector: Anopheles spp
est. 900 million at risk

Question 16

lymphatic filariasis transmission cycle

Answer 16

1. microfilaria ingested with blood meal
2. migrates from stomach - body cavity - thorax - head - down labium to proboscis
3. when feeding again, L3 nematodes rupture mosquito mouthparts and crawl onto skin of new host
4. enter bloodstream/lymphatic system
   (has nothing to do with saliva)

Question 17

acute lymphatic filariasis

Answer 17

localized swelling, pain, and fever associated with affected lymph nodes with adult nematodes

Question 18

chronic lymphatic filariasis

Answer 18

Elephantiasis (due to years of buildup)
accumulation of lymphatic fluid in limbs or genitalia
skin becomes “elephant-like”

Question 19

prevention and control of lymphatic filariasis

Answer 19

minimize exposure to mosquitoes

treatment:
- DEC drug - effective against microfilaria and adults
- ivermectin - effect against microfilaria only (person continues to have symptoms because of presence of adults)

Question 20

dog heartworm

Answer 20

parasite: Dirofilaria immitis
vector: any mosquito
transmission cycle: L3 nematodes erupt proboscis and land on skin then enter thru wound, travels to right ventricle