Posts tagged ‘Are Humans The Only Ones Who Get Lyme Disease?’

August 7, 2014

Can those pesky house mice spread Lyme Disease?

Various types of mice.

Various types of mice.

You may have read stories before on this blog talking about the link between ticks, Lyme Disease and white-footed mice. These stories may have peaked your curiosity about other species of rodents, especially pesky house mice that like to take up residence in our homes. Since we are entering into the peak season for nymph ticks, and very soon,  into the fall when the weather will be growing cooler and house mice will be looking for places to stay warm, now is a great time to become familiar with tick/mouse activity!

White-footed mice do exceptionally well in the habitat of the Northeast US and other similar places because of the urbanization of old farmland.  Open woodlots and brushy areas make ideal living conditions for white-footed mice and ticks.

Although Lyme Disease is not as prevalent in some US states, other tick-borne diseases are.  Tularemia, Rocky Mountain Spotted Fever and other infections are often prevalent in places Lyme Disease is not.  Shrews, voles, rabbits, chipmunks and other small rodents will fill a similar role as white-footed mice in these regions when available.

Notice this white-footed mouse is covered with nymph ticks

Notice this white-footed mouse is covered with nymph ticks.

When an adult female tick needs to lay her eggs, she looks for a location that will have a temperature warm enough in winter to allow her eggs to survive.  White-footed mice build nests in burrows, stumps, brush piles, buildings and in the abandoned nests of other small animals and birds.  These nests provide concealment for them from predators and warmth in the winter.

When an adult female tick lays her eggs in the nest of a white-footed mouse, she is providing both protection and a good start for the next generation.  When hatched into larvae in the spring and early summer, these ticks will take their first blood meal from the closest available small animal, which is usually the white-footed mouse.  Tick larvae are not infected with Lyme Disease when born.  Their first chance to be infected is when they take their first blood meal from the mice.  As these larvae ticks grow and need a second blood meal to grow into their third life stage as nymph ticks, the mice will often serve as hosts to that meal also.

Studies show that 80-90% of all white-footed mice are infected with the Lyme bacteria.  When you consider the number of larvae and nymph ticks that take their blood meal from white-footed mice, you can easily see why the infection rate is so high.  Ticks will often have to bite more than one host for a blood meal in order to get an adequate supply of blood, so they can grow into their next life cycle stage.  If one larvae or nymph tick is infected with Lyme Disease, the infection will usually be transmitted to any of the mice they bite.  Ticks that bite an infected mouse have a very high likelihood of becoming infected themselves and further transmitting the disease.  As ticks become larger, they need larger mammals and birds for their blood meal.  This is how Lyme Disease is transmitted to raccoons, foxes, opossums, birds, and other small mammals.  Deer serve as hosts for adult ticks because of their size allows them to have enough blood to provide many adult ticks their blood meal to lay eggs.

House Mice in a loaf of bread

House Mice nesting in a loaf of bread.

For mice that do not frequent open woodlots and brushy areas, there is little chance of them being exposed to ticks.  No contact with ticks means no Lyme infection.  This is the primary reason that Lyme Disease is rare or non-existent in mice that seek shelter and warmth in your home.  As these or any mice spend time in your yard and in tick habitat, it’s possible they can become infected, if bitten by an infected tick.  House mice have not been studied to determine if they contract Lyme Disease in certain situations; but there is no reason to think they would be immune.  It’s likely they are not a vector for Lyme Disease because they simply don’t spend as much time in tick habitat as other rodents.

As you can see, the circumstances that lead to Lyme Disease are diverse and complex.  With so many vectors, hosts and reservoirs responsible for the disease, researchers are a long way off from knowing how the disease continues to spread. Rather than wait for science to provide a solution, there are effective solutions now such as barrier sprays and tick tube implementation for your yard. Contact Mosquito Squad of West Montgomery now to discuss our tick barrier spray and tick tube program that will protect your yard all season long.

Susan Levi, Owner Mosquito Squad of West Montgomery.

Susan Levi, Owner Mosquito Squad of West Montgomery.

Learn more about protecting yourself and your family from the risks of tick-borne illnesses such as Lyme Disease in your backyard! Sign up today • (301) 444-5566 • email:westmontco@mosquitosquad.com

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July 24, 2014

Are Humans The Only Ones Who Get Lyme Disease?

Mosquito Squad of West Montgomery wants to keep you informed about Lyme Disease

Mosquito Squad of West Montgomery wants to keep you informed about Lyme Disease!

You may know that ticks get the Lyme bacteria, Borrelia Burgdorferi, from the white-footed mouse and then pass it on to us.  However, do the mice themselves get Lyme Disease?  Do they get sick?  What about all the other animals that ticks bite, like chipmunks, squirrels, raccoons, foxes, coyotes, birds and the like? The list of animals that ticks bite is a long one.  In order to make sense of the research, we need to break down this list.  It is easier to understand how Lyme Disease exists in wildlife by talking about small, medium and large animals, and birds.  The size of the animal seems to make more of a difference than the specie when discussing how Lyme Disease affects wildlife.

All size deer ticks can transmit disease.

All size deer ticks can transmit disease.

How is Lyme Disease transmitted? Before discussing how Lyme is transmitted, we need to define two terms.  The first is the term, host.  A host is, as you would expect, someone who serves someone something.  In the tick’s case, the host is the animal or bird who serves them their blood meal after the tick bites them.  A tick needs a blood meal in each of the three stages of its life cycle, larvae, nymph and adult in order to grow and move onto the next stage. The second term we need to define is reservoir.  Since ticks aren’t born with Lyme Disease, they need to get the bacteria from somewhere.  The term reservoir refers to where the bacteria are present.  Many animals can be reservoirs for the Lyme bacteria, Borrelia Burgdorferi.  Some reservoirs have an abundance of bacteria in their blood.  In other animal reservoirs, there may be very few Borrelia Burgdorferi bacteria.  An animal with a large number of bacteria in their blood are referred to as a competent reservoir.  This means they have enough bacteria to infect any ticks that bite them.  Other animal reservoirs can be incompetent reservoirs, meaning they have so few bacteria present they will not infect the tick when it bites them.

Small animals White-footed mice, chipmunks, rats, squirrels, moles, voles and certain species of birds are competent reservoirs.  These animals are often infected with Lyme Disease, as well as Anaplasmosis and Babesiosis.  These small animals are the ones most responsible for transmitting Lyme Disease to larvae and nymph ticks.  Since larvae and nymph ticks are often in the dens and burrows of these animals, they are often the young tick’s first blood meal.  The small ticks in this life stage do not need a lot of blood for their first meal.  Adult ticks need a larger animal for their larger blood meal. Although studies show these small animals are often infected with Lyme bacteria, there has been little to no research into how the disease affects them.  Whether they get a rash or sick from the bacteria is unknown.  One study that looked into the mortality of white-footed mice and showed 93% of them succumbed to predators, primarily weasels.  Only one mouse death in the study was attributable to Borrelia Burgdorferi bacteria.  From this study, we can hypothesize that most or all of these small animals can succumb to the infection, but it is not common. Is the lifecycle of the white-footed mouse so short or predation so high, that Lyme Disease doesn’t have a chance to take more of them?  We simply don’t know. Many studies have shown that birds are often infected with Lyme Disease and are responsible for its geographical spread.  One NIH study found, “ticks have detrimental effects on their avian hosts even under natural infestation conditions…and may also present symptoms of infection, though these may be subtle.”  Birds do seem to be affected physically by the Lyme bacteria; however, it is not acute or obvious.  Lizards may also become infected with Lyme Disease but are incompetent reservoirs.

Medium size animals Raccoons, groundhogs, rabbits, beavers, opossums, foxes, bobcats and coyotes rarely serve as reservoirs for Lyme Disease.  Scientists also do not find many ticks on them when sampled.  That doesn’t mean they don’t transmit other diseases.  Rabbits transmit tularemia, rarely Lyme Disease.  Beavers, like rabbits, transmit tularemia but are not identified with helping to transmit Lyme Disease.  Groundhogs transmit bronchopneumonia and hepatitis B primarily.  Squirrels transmit tick fever and their fleas can transmit plague.  Coyotes are incompetent reservoirs of Lyme Disease.  Foxes are also incompetent reservoirs of Lyme Disease. Foxes provide a benefit when it comes to Lyme Disease because they are predators of white-footed mice reducing their numbers. Even when the Lyme bacteria are found in these medium size animals, the bacteria present is minimal, making these animals incompetent reservoirs.  No research has been done on how or why the Borrelia Burgdorferi bacteria present in them is so low.  Whether some of these animals have less exposure to ticks carrying Lyme, or whether their immune system is prepared to prevent a significant infection, is not known.  Some scientists and studies have hypothesized that these animals may have a “primitive immune system” but no scientific definition exists for that term.  No studies exist to confirm or deny it.

https://mosquitosquadmaryland.files.wordpress.com/2014/07/egg-mass-produced-by-lone-star-tick.jpg

Egg mass produced by tick.

Large size animals The only wild large size animal in the tick lifecycle is the deer family. White tail Deer as well as other members of the deer family, including elk, moose and caribou are the blood meal host often chosen by adult ticks.  First, several thousand ticks can attach to deer because of their size.  This number of ticks makes it easy for males to locates the female ticks as ticks use deer to find a mate much like a local “pick-up” joint.  A female tick will use a deer to consume a large blood meal, in order to lay a clutch of 2,000 to 18,000 eggs.  Elk and moose carry dog ticks in the West, which are often infected with Ehrlichiosis and can be transmitted to humans.  With the introduction of elk and moose in the Eastern US, no one knows the effect they may have in Lyme Disease and Ehrlichiosis transmission. All deer are incompetent reservoirs with low levels of Lyme bacteria in their blood, despite the number of ticks that bite them.  Once again, scientists attribute the deer’s immunity to a primitive immune system or an ability to flush the bacteria from their blood. Based on numerous research papers, it is clear that the animals most responsible for transmitting Lyme Disease are small ones, especially white-footed mice, voles and other rodents.  Research studies show that voles become important in the transmission of Lyme bacteria mostly in areas where few white-footed mice exist.  Medium size and larger animals and birds spread the disease further geographically that any of the smaller animals because of their territorial ranges and their effectiveness in giving infected ticks a ride to new locations.

Susan Levi, Owner Mosquito Squad of West Montgomery.

Susan Levi, Owner Mosquito Squad of West Montgomery.

Tracing the epidemiology of Lyme Disease is complex, as you can see.  With so many vectors, hosts and reservoirs responsible for the disease, researchers are a long way off from knowing how the disease continues to spread. Rather than wait for science to provide a solution, there are effective solutions now such as barrier sprays for your yard. Contact Mosquito Squad of West Montgomery now to discuss our tick barrier spray and tick tube program that will protect your yard all season long.

Learn more about protecting yourself and your family from the risks of tick-borne illnesses such as Lyme Disease in your backyard! Sign up today • (301) 444-5566 • email:westmontco@mosquitosquad.com