1. Last of the Mosquitoes Announcements Speaking Today???
On Deck for Next Tuesday: Sean Allen, Lauren Torbett
About the Quiz …
Read Chapter 16 for next Tuesday, Chapter 17 for next Thursday

2. Yellow Fever Historically second only to malaria but now lags dengue.
Potential for catastrophic outbreaks persists.
Like Dengue, a Flavivirus
Called “Yellow Fever” because of the jaundice that it often creates
First arbovirus (arthropod borne virus) associated with human disease.
Carlos Finlay, Cuban physician, first suggested the connection between mosquitoes and yellow fever
Walter Reed conducted human experiments with US soldier volunteers to confirm the connection.
Reed’s discovery enabled the US to complete the Panama Canal where the French could not.

3. Principal Endemic Zones
Note: Yellow fever has never been reported in Asia

4. Population here will double between 2009 & 2020

5. Three cycles Endemic (Sylvatic) Intermediate Epidemic (Urban)
Cycles in arboreal monkeys
Mosquitoes are not common ground level
Loggers encounter infected mosquitoes
Transmission: monkey – mosquito – human is one way
Produces sporadic cases
Intermediate
Monkey – human and back
Mostly African savannah
Most common form of outbreak in Africa
Epidemic (Urban)
Loggers enter a town with container breeding mosquitoes (esp. Ae. aegypti)
Mosquitoes acquire the virus
human – mosquito – human cycle established.

6. Symptoms Increasing Viremia 3 – 6 days post-infection
Initial flue-like symptoms: fever and chills, severe headache, back pain, general muscle aches, nausea, fatigue, and weakness
1-2 day remission
“Toxic phase”- flu-like symptoms return, with abdominal pain (from hepatic involvement).
Hepatic coagulopathy produces jaundice and numerous hemorrhagic symptoms:
Hematemesis (black vomit)
Epistaxis (nose bleed)
Gum bleeding
Petechial and purpuric hemorrhages (bruising).
Late stage (“malignant”) hypotension, shock, metabolic acidosis, acute tubular necrosis, myocardial dysfunction, and cardiac arrhythmia.
Terminal stage - Confusion, seizures, coma, death from cardiac failure
Survivors of the hepatic phase often have secondary bacterial infections and kidney failure.
Weakness/fatigue may last months in survivors.

7. Encephalitis Encephalitis – an acute inflammation of the brain
Encephalomyelitis - When both the brain and spinal cord are involved
Encephalomyelitis often follows viral encephalitis and so is often referred to as “post-infection encephalitis”
Separate from but may occur with meningitis
Can be either bacterial (including protozooan) or viral
Among the viral forms, arboviruses are the most common (other common forms are HIV secondary, rabies, herpes simplex)

8. Arboviral Encephalitis
Most arboviruses can cause encephalitis
All important mosquito viruses can cause encephalitis
Only some of these have encephalitis as a primary symptom
Survivors of the initial encephalitis proceed to encephalomyelitis hence the name for the mosquito viruses.

9. Mosquito Encephalomyelitis Viruses in North America
Togoviridae (all Alphaviruses) – Bird viruses
EEE (most pathogenic to humans)
WEE
VEE
Flaviviridae (JE complex) – Bird viruses
West Nile
SLE
Bunyaviridae – Chipmunk/Squirrel viruses
LaCrosse

10. MOSQUITO SURVEILLANCE PROGRAMS
Used for Anticipated Health Threats
Mosquito surveillance programs detect:
When each species is present
When each life stage is present
Disease risk
Conducted by public health agencies
May be combined with disease surveillance programs

11. Two kinds of surveillance
Mosquito population monitoring
Eggs
Larvae
Adults
Impact Assessment
Disease risk
Economic impact
Most economic assessments are veterinary

12. Population Monitoring: Eggs
Oviposition Traps (see example)
For container breeders
Sod/Soil/Debris Sampling
Requires a means of separating eggs from sample (see machine on right)
Gravid Traps (see example)
Culex/Coquillettidia egg rafts can usually be found

13. Larval Sampling – Main sampling tool is the larval dipper
Important note: This tool does NOT indicate absolute populations as commonly used but is a relative measure. Typically used for presence/absence sampling.

14. Different techniques are used with different habitats/species
Shallow Skim- Anopheles
Partial submersion- Around emergent vegetation,
Complete submersion- For quick diving species such as some Aedes and Psorophora,
Dipper as a background- woodland pools, for early season species.
"Flow in" method- Shallow water with debris.
Scraping- Sampling from submerged clumps of vegetation.
Simple scoop- Most common, especially for Culex.
Salt marsh- Standard Protocol for potholes with vegetation.

15. Sampling Adults Males – Not interested in them
Blood questing females – Light/CO2 traps
Gravid females – Gravid traps
General – Resting Boxes (Culeseta & Anopheles)
Non-attraction traps – sample at random

16. CDC - Light/CO2 Baited Trap
Can use gas, dry ice, or chemical sachet
Generally overnight
May be used with light
Some differentiate by time

17. Other Traps for Blood Questers
Mosquito magnet used as a sampling tool
Sonic trap mimics the sound of a dog’s heartbeat

18. Gravid Traps Generally left overnight
The type of water affects trap catch
Very susceptible to rainfall
May also find eggs on/near water

19. Impact Assessment Biting Rate Disease Risk Human Bait Animal Bait
Prevalence in Mosquito Population
Prevalence in Host Population

20. Human Landing/Biting Rate
Fixed time interval
Sample at same time of day
Standardized human
Widely restricted

21. Sentinel Animals
More commonly used as an early warning for disease risk

22. Landing Rates & Impact Human Nuisance – Must know two things:
Number of bites people are willing to tolerate
Bite rate that results in action
Disease risk – Must know the proportion of bites that result in new infections

23. Final Thoughts on Mosquito Population Sampling
All commonly used methods are relative – None give absolute estimates.
Different species are sampled at different rates for each technique.
Generally, must pre-define which species in the mosquito complex is the target of a sampling program then select the appropriate technique(s).

24. Determining Disease Prevalence in Mosquito Populations
Sort into pools

25. Many diseases have simple strip tests available (tend to be around 70% accurate, but their cheap & easy).

26. This one costs $60 & does 20 tests

27. More accurate and sophisticated techniques are available
Most are based on an amplification procedure.
Such procedures require facilities with appropriate containment as well as specialized equipment & training.
Cost prohibitive in many management programs (typically $20 – 25/test).