Precip and EEE
April 18, 2010

Due to the recent deluge in parts (or all) of the Northeast, EEE should make a strong showing this year. It is known that moisture is needed to sustain the vectors that carry the virus and with the substantial amount that has fallen over the past several months, vectors will have an increased selection on where they might reside. With the significant increase over the average rainfall for this time of year and the unseasonably warm temps early on, I would venture to say that EEE will make a significant showing this year. Since 2003, average precipitation amounts for NH have been around 55.87″ with on average 30 animal EEE occurrences per year (humans included). That’s almost one EEE occurrence per 2″ of precipitation. However, this year has seen record setting precipitation in the first quarter of the year alone. Southern NH, especially Rockingham county, was hard hit with Epping, Greenland, and Portsmouth exceeding 14″ of precip in March alone. Of course, this area of the State is the primary hotspot for EEE any way.

As we can see, we’re dealing with the potential for increased occurrence for EEE this year due to increased precipitation. It’s important to realize that the environment can be a great predictor of disease, especially for those that are spread by animals such as mosquitoes and birds because their livelihood heavily depends on it. In my opinion, prediction and prevention, using environmental data, is the best way to combat these diseases; to know and understand the world around you puts you in control to decide whats best for you and that’s the way it should be.

Sustaining EEE-Environmental Conditions
March 21, 2010

As it turns out, weather and climate affect the transmission cycle of Eastern Equine Encephalitis (EEE). There must be specific environmental conditions present to sustain the disease and, as these conditions are present, we notice that cases of EEE spike.

The weather and climate of New Hampshire is some of the most dynamic in the world (Keim, 2004). In a calendar year, temperatures range from sub-zero to near triple digits. Precipitation in the form of snowfall and rainfall also occur in varying amounts across the state. Land elevation also plays a role in both temperature and precipitation as higher elevations experience lower temps and windward areas greater amounts of precipitation (Rainshadow Effect). Despite elevation, summers in New Hampshire are not unlike those in Miami or Atlanta as the warm, humid air mass can extend from southern Florida to New England. However, this is not the case during the winter as the polar front from Canada doesn’t normally extend too far down the east coast. (Keim, 2004).

Environmental factors conducive to EEE have the ability to linger across multiple seasons in New Hampshire. Mosquitoes that transmit EEE can survive in temperatures between 55.4-95 degrees Fahrenheit, but need significant rainfall to promote their longevity and provide habitat (Sellers, 1980; Thompson and Connor, 2001). In New Hampshire, these conditions can last from late spring to early fall (May-September).

Research by the Centers for Disease Control have noted that EEE is transmitted most commonly adjacent to freshwater hardwood swamps. Some research has noted that vegetation, such as the Papyrus Plant, has contributed to lower mosquito densities, specifically in swamps in highland Africa (McCrae, 1983). (Of course, the Papyrus research was done to support ways to combat Malaria. But both Malaria and EEE have striking similarities-both vector-borne diseases-and since Malaria research has been evolving for an extended timeframe, it is only the progression of science to compare both diseases and use methods which have worked in the fight against Malaria for the fight against EEE). EEE vectors are also known to originate in tall grass, wooded areas, and man-made items such as old tires and gutters.

As urbanization has spread in rural areas of New Hampshire there is growing concern of increased EEE incidence. As humans spread into natural vector habitats there must be a new plan to prevent EEE. Current methods of deterring EEE cannot be exclusively depended upon.

Keim, B. 2004. A Climate Primer for New England, Airmap.  Retrieved from:

McCrae, A.W.R. 1983. Oviposition by African Malaria Vector Mosquitoes. I. Temporal Activity Patterns of Caged, Wild-Caught, Freshwater Anopheles gambiae Giles Sensu Lato.  Annals of Tropical Medicine and Hygiene, 77: 615-625.

Sellers, R.F. 1980. Weather, Host and Vector: Their Interplay in the Spread of Insect-Borne Animal Virus Diseases.  The Journal of Hygiene, Vol.85, No.1, pp.65-102.

Thompson, M.C., and Connor, S.J. 2001. A Framework for Research in Africa: Malaria Early Warning Systems.  Roll Back Malaria Cabinet Project, World Health Organization.

EEE Transmission Cycle
March 13, 2010

After an unusually busy week, today’s thoughts are on the EEE Transmission Cycle. Here’s my first question to you: Where does EEE originate? There’s been much misinformation given as to where EEE begins its life cycle. This is partly because its name-Eastern Equine Encephalitis-describes the disease as being of “Equine” or horses. Another major reason is because there is confusion between the two main players or “vectors” in the transmission cycle of EEE.

According to Dr. Alan T. Eaton (UNH), EEE is “a mosquito spread disease of birds, that sometimes is transmitted (via mosquito bite) to horses and people.” In other words, birds contain EEE and are bitten by mosquitoes who then bite horses or humans to pass the EEE along. So in technical speak, it’s the primary/host vector (birds) to bridge vector (mosquito) to dead end host (humans or horses etc). Horses and humans are referred to as dead end hosts because when an infected horse or human is bitten by a mosquito there is no chance of EEE being passed on in reverse. The reason for this is because the concentration of EEE in a horse or human is far less than in a smaller animal such as a bird.

However, it must be made known that not every specie of mosquito carries or transmits EEE. There are some mosquitoes that only bite birds and which sustain the circle of the EEE disease life (primary vector to bridge vector to primary vector etc etc). Furthermore, there are those mosquitoes that bite both birds and humans and are the ones we are most concerned about. In all, according to Eaton, there are about 47 species of mosquitoes that live right here in NH, some transmit EEE and some don’t.

As we know, EEE is a deadly virus, and symptoms can range from mild flu-like to inflammation of the brain, coma, or death. And most who acquire the disease have lingering neurological effects. This is a serious disease and should be treated as such.

Next time we’ll have a look at the geography of the disease (my specialty) and how it can be used to create a system of knowing when EEE and its vectors are present.


Eastern Equine Encephalitis Could Return to New Hampshire this Summer                                                                                  Alan T. Eaton, PhD, UNH Cooperative Extension Entomology Specialist

March 7, 2010

This is the first of what is hoped to be many entries which may give further insight into the world of vector-borne disease. Diseases such as Malaria, West Nile virus, and Eastern Equine Encephalitis (EEE), among others, are of this category. The main concentration of this blog will be on EEE since it is relevant to my location in New Hampshire and I have completed a master’s thesis on it describing the nature of the disease. Since EEE usually affects the human population in specific times of the year spring, summer and early fall, people generally tend to take the stance “out of sight, out of mind”. This stance, of course, will provide little effectiveness in the fight between human/disease vector co-existance.

What i plan to do with this blog is to provide insight into the world of EEE so that those who read it become aware of what EEE is and how it is sustained in various eco-systems. New Hampshire will be used as my study area since I know it well and has an existing endemic, or native, EEE precedent.