Ticks: A summer survival guide

Tick nymphs
Blacklegged tick nymphs crawl around in a test tube at an entomology lab on the University of Minnesota's St. Paul campus. The ticks, whose movements were sped up in the editing process, are commonly referred to as deer ticks.
Animation by Jeffrey Thompson | MPR News

This time of year, Minnesotans are very ready to shed some winter layers and get outdoors.

But it's also the same time of year that ticks are very ready to find hosts.

Here's what you need to know about ticks and the diseases they carry.

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Where am I most likely to be bitten by a tick?

In Minnesota, blacklegged ticks (also known as deer ticks) are the ones that carry disease. And the range of this tick is spreading, thanks in part to climate change.

Blacklegged ticks live on the ground and prefer "edge habitat," which is where habitat changes from forest to brushy growth. They thrive in undergrowth and forests made up of young trees.

When it's time for a tick to find a host, it will often climb up a blade of grass. Ticks can smell approaching humans, and will attach to you if you happen to brush up against it.

When am I most likely to be bitten by a tick?

Ticks are most active on warm, humid days. The peak season for ticks is May through mid-July.

A blacklegged tick has a life cycle of two years. Adult ticks spend four to five weeks laying thousands of eggs each spring. After about a month, the eggs hatch. Ticks need what scientists refer to as a "blood meal" in order to molt to each new life stage: larva to nymph to adult.

Ticks can live for up to a year without feeding (they will be dormant during the cold winter months), and it takes them four to six weeks to digest their blood meals. Larvae, nymphs and adult females all feed on blood.

Ticks and a penny
The three stages of the blacklegged tick - an adult female, a nymph and larva - as compared to a penny at a University of Minnesota lab.
Jeffrey Thompson | MPR News

How do ticks transmit disease?

The most common tick-borne diseases in Minnesota are Lyme disease (1,200 to 1,400 cases each year) and human anaplasmosis (600 to 700 cases). Lyme and anaplasmosis are caused by bacteria that can infect a tick as it feeds on other mammals. These bacteria don't affect ticks negatively, but they do make humans sick.

When a tick first attaches to its host, it will spend about three days preparing the site, spitting in saliva and sucking out tissue. The host's immune system doesn't want the tick there, but the tick's saliva has substances in it that interfere with the host's immune response, cutting down on inflammation and itching.

While the tick is attached and prepping, its saliva erodes the host's blood vessels. When the site is ready, the tick will take what's called "the big sip" — and its size will increase considerably in just one day. It is during this feeding when bacteria is most likely to be transmitted.

If you are able to remove the tick during those first few days before "the big sip," it's unlikely — though still possible — that the tick will transmit bacteria to you.

What are the symptoms?

Symptoms of human anaplasmosis and Lyme disease include:

• Rashes (a bull's-eye rash indicates Lyme disease)
• Fevers
• Headaches or body aches
• Chills
• Fatigue
• Nausea

More on the symptoms.

How can I protect myself from disease?

• Avoid areas where ticks are active.
• If you can't avoid those areas, wear long-sleeved shirts with pants, and tuck your pants into your socks.
• Use repellent containing permethrin or DEET.
• Check yourself frequently for ticks and remove them promptly when you find them.