Babesiosis is an infection caused by a parasite that belongs to a family of parasites called Babesia. There are over 100 Babesia species but only a few can infect humans.

It can spread to people from a tick bite from an infected blacklegged tick. The tick usually needs to be attached and feeding on a person’s blood for at least 24 hours to pass the parasite onto them.

Less commonly, the parasite that causes babesiosis can be spread through getting a blood transfusion or organ transplant from a donor who has Babesiosis. In rare cases, pregnant women who are infected may also spread Babesiosis to their baby during pregnancy/delivery.

Symptoms usually begin to show up within one to four weeks after getting bitten by an infected tick or one to nine weeks (and up to six months) after getting a blood transfusion with infected blood.

Most people who get Babesiosis do not have symptoms, however, people who do get symptoms may have:

  • Fever
  • Chills/sweats
  • Headaches
  • Body aches
  • Loss of appetite or feeling less hungry than usual
  • Nausea
  • Low energy or feeling more tired than usual

Some people may develop a more serious condition that affects their red blood cells. Symptoms of this include feeling more tired than usual, yellowing of the eyes and/or skin (jaundice), and dark urine.

In some cases, Babesiosis infections can last for weeks to months.

People who live in, work in, travel to, or visit areas that are at-risk for blacklegged ticks have a higher risk of getting Babesiosis.

Babesiosis can be serious and dangerous in people who:

  • Have a high parasite level
  • Have a low hemoglobin level (a component in red blood cells)
  • Don’t have a spleen or reduced spleen function
  • Have a weakened immune system (due to illnesses like cancer, AIDS, transplants or certain medications)
  • Have serious health conditions (e.g., a chronic liver or kidney disease)
  • Are a newborn that was born prematurely
  • Are over 50 years of age

If you think you might be sick with Babesiosis, speak to your health care provider about assessment and treatment options.

The best way to prevent Babesiosis is to avoid tick bites.

How to avoid tick bites:

  • Wear long pants and long sleeves.
  • Light coloured clothing may make ticks easier to spot.
  • Apply insect repellent approved by Health Canada (Personal Insect repellents –, following the manufacturer’s instructions
  • Walk closer to the centre of trails avoiding brushy areas that may extend out on the trail edges.
  • After spending time outdoors in wooded or bushy areas, shower to remove ticks before they become attached.
  • Carefully check your full body and head for attached ticks.
  • If you find a tick on your body, remove it as soon as possible.
  • Remember to also check your children and pets for ticks.

Babesiosis is diagnosed by a blood test to check if you have the parasite or have been exposed to it.

People who are sick with symptoms can usually get treated with a combination of antibiotics and medication used to treat parasites. If you don’t have symptoms, you may not need treatment. Speak to your health care provider for an assessment and treatment options.