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