Case History: Tick induces malaria-like symptoms
Tuesday, 23 October, 2012, 12:00am
Case History: Tick induces malaria-like symptoms
Roland Lee was an energetic man who travelled between Hong Kong, Shenzhen and New York running his business. So when 61-year-old Lee (whose name has been changed for reasons of patient confidentiality) started to feel increasingly fatigued, he was not sure what to make of it.
The bouts of fatigue grew worse, sapping not only his energy but his appetite, leaving him feeling constantly weak. He then developed a low-grade fever as his symptoms dragged on for two months.
During one of his business trips to Shenzhen, he sought treatment at a hospital, but doctors were baffled by his symptoms and could not pin down a diagnosis. He was given antibiotics, but little more was done.
He was feeling extremely unwell while in Hong Kong in June, so he checked himself into the North District Hospital. Immediately after admission, his temperature rose to 39 degrees Celsius, his blood pressure plunged, and Lee went into shock. He was taken to intensive care where doctors fought to stabilise him while trying to figure out his ailment.
Tests showed that Lee's liver function was impaired. He was also severely anaemic - there were not enough red blood cells circulating in his body - and his haemoglobin levels were extremely low.
Where a healthy male should have 12 to 13 grams per decilitre of haemoglobin, Lee only had six grams per decilitre.
As haemoglobin carries oxygen, this meant that Lee's body was being starved of oxygen, which explained his severe fatigue and weakness.
Lee's symptoms were strongly suggestive of malaria. Doctors sent his blood to be tested for this and found that many of his red blood cells were infected by parasites - these red blood cells are thus called parasitised blood cells.
They appear to have ring forms inside, which is a typical presentation of a strain of malaria parasite called Plasmodium falciparum. It is the most dangerous form of malaria, and can cause high rates of complications and fatality.
When 5 per cent of red blood cells are invaded by parasites, doctors already consider it to be a severe case of malaria. But Lee had a whopping 15 per cent of parasitised red blood cells.
The affected red blood cells also become deformed - in the case of P. falciparum infection, they tend to be larger or smaller than normal. When these cells pass through the spleen, the organ will destroy them. When a large number of red blood cells are being destroyed, it results in haemolytic anaemia.
The likely diagnosis of malaria prompted doctors to transfer Lee to the Infectious Disease Centre in Princess Margaret Hospital, where specialist Dr Jacky Chan Man-chun was called in.
Lee was given blood transfusions and antibiotics to help support his embattled body. Chan also started Lee on two types of first-line malaria medication while other tests were performed to confirm the diagnosis.
Although malaria was the likely culprit of Lee's condition, several factors did not add up. Chan says while the blood smear showed that the parasitised red blood cells were deformed, there were more varied deformations than in typical P. falciparum infection.
Moreover, given Lee's travel history, none of the places he visited were known for malaria infections. But as Chan had spent time in New York City, another parasite became a suspect. Babesia is a type of parasite that can cause very similar symptoms to malaria but is transmitted by ticks.
It also infects the blood, causing haemolysis, anaemia, weakness and fever. Once it invades red blood cells, the parasite will ingest all the nutrients in the cell and cause its deformation and subsequent destruction by the spleen.
But babesia is extremely rare in Hong Kong. If Lee was infected, he would only have been the second case ever reported in the territory. However, babesia infections are not uncommon in the US. Although there are more than 100 species of babesia, only a few are known to have an effect on humans, the most common being Babesia microti and Babesia divergens.
Because of the similarities in symptoms between malaria and babesiosis (illness caused by the babesia parasite), babesiosis is frequently misdiagnosed as malaria. Chan needed to confirm if Lee truly suffered from malaria, so the laboratories used a rapid diagnostic test to check for malaria antigens. But two different tests came back negative. Next, tests were used to check for malaria DNA and babesia DNA. Only the babesia DNA test came back positive.
With a confirmed babesiosis diagnosis, Chan switched to first-line medication to treat it. Although Lee was stable enough to be moved out of the ICU to the general isolation ward after two days, he had to remain in hospital for another three weeks while his body took time to restore his levels of red blood cells and haemoglobin.
Lee later mentioned that he had a pampered pet dog in New York. Chan suspects that the dog picked up a carrier tick in the basement, and the tick infected Lee while the dog snuggled in his bed.
Lee has since recovered fully. He has also engaged a professional cleaning crew to thoroughly clean his New York apartment.
Chan says babesia is a common parasite found in the US and in Europe. He advises the public to be on guard for any unusual symptoms following insect bites while travelling
