A new study says up to 70 per cent of Canadians who travel abroad, especially to developing countries, return with some sort of illness -- and many of those cases are preventable.

The study, published in the journal Open Medicine, looked at 4,365 travellers. 

Researchers documented a wide array of diseases they brought back, including malaria, typhoid fever, tuberculosis, hepatitis B, hepatitis C and parasitic roundworm.

Dr. Andrea K. Boggild, an infectious diseases specialist at Toronto General Hospital, said treatment, recovery and observation can go on for much longer than expected.

“We see syndromes called post-infectious irritable bowel and post-infectious fatigue that can last weeks or months even after the infection has cleared by the immune system,” she said. 

After a vacation and honeymoon trip to Bolivia with his wife, traveller Andrew Higgins returned to Canada covered in insect bites.

One of those bites started to grow.

“It was just like a crater in my skin; a perfect circle that just sunk in a couple millimeters into my skin,” he told CTV News. “From there it started to grow and it probably got to be just a bit larger than a toonie before it started to recede.”

After weeks of research and numerous doctors, Higgins finally saw a tropical disease specialist at Toronto General Hospital. The diagnosis was cutaneous leishmaniasis, a skin infection caused by sandfly bites.

“She said we needed to get on treatment right away.”

Higgins was told if he didn’t get treated intravenously with heavy antibiotics, the infection could spread to the rest of his body. But recovery would be a long and complicated process.

“I actually didn’t make it through the entire treatment because my kidneys started to react quite poorly,” Higgins said.

Higgins has now moved on to the antifungal treatment fluconazole. “I am taking 500 milligrams a day and I have been since December,” he said.

Higgins made sure to visit a medical clinic before his trip, and took medications to prevent malaria. But he may not have been as diligent about avoiding insect bites.

Doctors are strongly recommending travellers seek pre-travel medical consultation at least six weeks in advance of a trip. But about two thirds of the patients in the study had not asked a doctor for advice before travelling.

Higgins has been told by doctors he must watch for any symptoms that might be early indicators of the return of the infection.

“I need to basically be monitoring myself for the rest of my life,” he said.

With a report from CTV's medical specialist Avis Favaro and producer Elizabeth St. Philip