Accidental Hosts: Humans and Lyme Disease

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Connecticut has the fifth most cases of Lyme disease in America and the second most in New England. Dr. Neeta Connally Connally, professor of biology at Western Connecticut State Universtity, is an expert on tick-borne, or vector-borne, diseases. She is a member of the American Society for Microbiology and has a research lab dedicated to studying the epidemiology of these diseases.  Connally gave a lecture on lyme disease prevention at the university late last year and offered insight into the science of Lyme disease as well as how to prevent infection.

 

Vector-borne diseases are fall into five different categories: viral diseases– such as Colorado Tick Fever, rickettsial diseases – such as the spotted fevers, parasitic diseases – such as babesiosis, toxin diseases – such as tick paralysis, and finally bacterial diseases – such as Lyme.

 

Lyme disease became a nationally notifiable disease in 1991, meaning that cases of it must be reported to governmental authorities by law. In the United States, Lyme ranks as number ten on the list of notifiable diseases, but Connally explained that cases of it are also widely under-reported. The Eastern and Central Northern U.S. are at the most risk for Lyme because these are the sections with the most forests. 90 percent of Lyme-infected ticks are found either in the woods or at the border between woods and meadows, which is where small animals and deer, the two primary hosts for ticks, generally live.

 

 

Humans are the accidental hosts. They will feed off of us, but only if they end up on us by mistake, which is apparently quite often.

 

 

Connally made a point to differentiate between the three types of hosts: reservoir hosts, reproductive hosts, and accidental hosts. Reservoir hosts are almost always birds or small mammals, the most common being the white-footed mouse. This type of host allows Lyme disease to be spread from one tick to another, because when an infected tick feeds on a reservoir host, it infects the bloodstream of the host, thereby infecting the next tick that feeds there.

 

Reproductive hosts include animals whose immune systems can flush itself of the infection, so it cannot be spread from one tick to the next. The sole purpose of these hosts is to provide female ticks with a meal, which then allows the female to lay her batch of up to 30,000 eggs. Only female ticks feed off of blood, and the primary reproductive host for ticks is the white-tailed deer.

 

Humans are the accidental hosts. They will feed off of us, but only if they end up on us by mistake, which is apparently quite often.

The majority of Lyme infections in humans occur in the summer and fall between the months of August and October. Children under ten and adults over sixty are the most susceptible to infection. Symptoms can appear anywhere between three and 30 days of infection, and can include a bulls-eye rash at the location of the bite along with feelings of extreme fatigue.  Oral antibiotics can be taken to treat Lyme in its early stages, but antibiotics must be administered intravenously in later stages of infection. There is currently no effective vaccination for Lyme.

 

But Connally explained that there are numerous ways to avoid being infected in the first place. The first type of prevention measures is landscape modification: putting up fences at the edge of the woods in your back yard so that tick-carrying deer cannot enter, choosing deer-resistant plants, or placing a dry barrier between the woods and your yard so that ticks, who need a humid environment to survive, will be discouraged from entering the yard on their own accord.

 

The second type of prevention is personal prevention: methods such as spraying yourself with insect repellents, showering after being outside, performing tick checks on yourself when you come inside, and wearing long pants and long sleeves. Wearing light colors also helps, because it will be easier to see ticks if they crawl onto your clothing. The third type of prevention, chemical prevention, involves treating your entire yard with an area-wide acaricide to kill any ticks.

 

 

People who bathed within two hours of being outside and checked for ticks within 36 hours of being outside had the most success in avoiding infection. Yards treated with pesticides had 62 percent fewer ticks, but this actually made no decrease in rate of human infection.

 

 

Lastly, Connelly discussed community interventions, which can be controversial. These interventions usually involve deer management, which essentially means hunting off excess deer in an area to decrease the risk of disease.

 

“There are so many ways to prevent Lyme disease that it can be overwhelming,” acknowledged Connally, who then went on to explain that studies were done in Connecticut for this very reason: to find out which methods of prevention are the most effective.   Connally described two studies that she participated in – a case study, where researchers interviewed people about their prevention techniques over the telephone, and a cohort study, where participating households had their yards sprayed with either a pesticide or water, but were not told which. The case study revealed that people who bathed within two hours of being outside and checked for ticks within 36 hours of being outside had the most success in avoiding infection. The cohort study showed that yards treated with pesticides had 62 percent fewer ticks, but this actually made no decrease in rate of human infection.<

 

Connally said that the next experiment taking place in Connecticut will be a bait box intervention study, where researchers will try to gauge the effect of pesticide-treated bait boxes. These boxes will lure mice in with food, and then treat them with pesticides that will kill any ticks that they are carrying.

 

“What will happen with this? I don’t know,” Connally admitted, “Stay tuned.”

 

 

This article was originally published in The Echo.

 

The Echo is the student-run publication of Western Connecticut State University whose aim is to inform and enlighten the university community. The Echo’s goal is to establish and maintain an atmosphere of free and responsible journalism in an engaging and entertaining format. Anything published in The Echo in no way represents the opinion of the university or it’s faculty and administration.

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