Mosquitoes continued

Announcements

Speakers for today: Chris Gibson (malaria) and Sarah Stephan (dengue)

On Deck: Natalie Popham

Quiz Next Tuesday – Covers chapters 12, 13 & 14 (Biting Midges, Black Flies, Mosquitoes)

#3 Culex pipiens/restuans

• Northern house mosquito• Most likely to transmit WNV• Feeds at night on birds, humans

#4 Ochlerotatus japonicus

• Asian bush mosquito• Currently invading state• Begins biting mid-morning, lower extremities

#5 Ochlerotatus triseriatus

• Eastern treehole mosquito• Vector of La Cross encephalitis• Feeds at dusk on small mammals, humans to lesser extent

#6 Anopheles punctipennis

• Mottled-wing Anopheles• Aggressive nuisance biter• Feeds during the day/dusk in shady/forested areas

#7 Anopheles quadrimaculatus/crucians

• Common malaria mosquito (quadrimac.)• Vector of dog heartworm• Feeds during day/dusk in shady/forested areas

#8 Ochlerotatus trivittatus

• Three-striped mosquito• Aggressive nuisance biter, especially when hot, after rain• Particularly prevalent in flooded woodlands• Feeds during the day, dusk

#9 Psorophora ciliata/howardii

• Gallinipper• Ouch!!• Feeds during the day, at night

#10 Culex erraticus

• Weak flier, feeds mostly on forest animals• May feed on humans when present

Generic Mosquito Life Cycle

• Larvae are wigglers

• Pupae are tumblers (quite active)

• Both breath air

• Eggs are laid on the surface of water in rafts (Culex) or singly (Anopheles) or near water (Aedes)

Most breath atmospheric air via a siphon

Mosquito Diet

• Most Larvae feed on algae but a few are predaceous and feed on other mosquito larvae

• Only females are blood sucking

• Males and females feed on nectar and other plant juices

After Emergence …

• Day 1 – Rest on nearest available moist/shady spot. Vertical surfaces.

• Day 2 – Carbohydrate feeding

• Day 2/3 – First blood meal

• Next Day – First egg clutch

• After egg clutch, more carbohydrate & blood meals

• Typical adult lives 7 – 10 days

Mosquitoes and Disease• Malaria• Nematodes (Filariasis)• Viruses with Hemorrhagic Forms

– Yellow Fever– Dengue– Rift Valley Fever

• Encephalitis (Encephalomyelitis) Viruses– Western Equine Encephalitis (WEE)– Eastern Equine Encephalitis (EEE_– St. Louis Encephalitis (SLE)– Venezuelan Equine Encephalitis (VEE)– West Nile Virus (WNV)– La Crosse Encephalitis (LCE)– Japanese Encephalitis Virus (JEV)

Malaria

• “mala” “aria” – bad air• One of the most widespread human disease

– Approximately 700 million current have the disease– Roughly ¼ of humans are currently at risk– 9th leading cause of death among humans in the world (MAP)– 4th leading cause of death among children <5 world wide

(WHO, 2005), 3 times that of accident/injuries– Number 1 cause of death among children in the tropics.– 1 – 3 million people die from malaria each year (NAID, 2009),

mostly children– 90% of cases are in Sub-Saharan Africa. Other hard-hit areas

are: India, Brazil, Sri Lanka, Afghanistan, Vietnam and Colombia.

Malaria is transmitted by Anopheles mosquitoes

• The principal genus in the Anophelinae

• The other Subfamily are the Culicinae

• Species can be distinguished by eye very easily based on how the larvae float, how the adults rest, how the adult head appears

Anopheles vs. Culicine mosquitoes – Adult Resting Behavior

Anopheles Adult

Culicine Adult

Anopheles vs. Culicine mosquitoes – Larval Resting Behavior

Anopheles larva at rest

Culicine larva at rest

Anopheles vs. Culicine mosquitoes – Head Shape

Anopheles Mouth Parts

Culicine Mouth Parts

Malaria Parasite

• Protozoa in the genus Plasmodium. 5 spp, Each causes its own form of malaria, each is transmitted by its own mosquito complex

• Fevers that they cause are classified by their recurrent frequency (AKA paroxysms)– Quotidian: Recurrent fever every 24 hours– Tertian: Every 48 hours– Quartan: Every 72 hours

P. falciparum

• Causes “Malignant tertian malaria”– tertian malaria is a recurrent

fever (paroxysm) every 2 days• Most dangerous form of

malaria• 90% of cases and deaths

world wide.• Global in distribution (see

MAP)• Closest known relative is a

chimpanzee malaria, transferred to humans as recently as 5,000 years ago

P. vivax

• Causes “Benign Tertian Malaria”

• 2nd most common

• Rarely fatal

• Mostly in Asia & Latin America

Mature P. vivax schizont

P. malariae

• Causes “Quartan Malaria”– Paroxysm every 3 days– Persists for a very long

time, life-time is common– Almost never fatal

• World wide distribution• Can be misdiagnosed

with P. knowlesi

P. ovale

• Causes a benign tertian malaria similar to P. vivax but with a long-lived recurrent form similar to P. malariae.

• Mostly limited to W. Africa but is spreading.

Plasmodium ovale trophozoite

P. knowlesi

• Causes a Quotidian Fever– Paroxysm every 24 hours

• Non-relapsing, case mortality ~2%• First found in a human in 1965, Malaysia.• Second case in 1971• Has been growing rapidly since 2004• Now accounts for up to 70% of cases in

Malaysia, neighboring countries reporting cases