Sunday, 1 June 2014
The two unknown tick diseases that are killing many Chinese
Two virtually unknown tick born rickettsial diseases have become a serious threat to human health in China, health authorities have warned. In just a few years the diseases caused by tick-borne A. phagocytophilum and E. chaffeensis have become common in rural areas and cause disease including multiple organ failure and death, according to Dr Zhang Lijun and colleagues at the Department of Rickettsiology, National Institute for Communicable Disease Control and Prevention, Beijing.
In a new paper they report that the first cases of human granulocytic anaplasmosis (HGA) occurred in Anhui Province in 2006 and then in Shandong. They said human granulocytic anaplasmosis is a serious disease in which about half of patients are hospitalised, 40% of patients have multiple organ dysfunction syndrome, and the fatality rate can be as high as 8%. However, they suspected that in China infections with the two rickettsial diseases were often not recognised, and were misdiagnosed as hemorrhagic fever with renal syndrome (HFRS).
In their own study they analysed 7,322 serum samples from farmers and found that 10-15% farmers had been exposed and were at substantially increased risk of the diseases. A second analysis of 819 blood samples from urban residents from showed that 4-12% of urban residents had been exposed and were also at high risk of the tick-borne diseases. Worryingly, the infections were carried by a wide range of ticks, not just one species, and the ticks were found on many domestic animals and livestock including dogs, goats, sheep, cattle, horses, rabbits and rodents.
"In China, the free-range feeding of animals is a major part of livestock production, in contrast to livestock production in modern developed countries. Animals roam hills for feeding during daylight and return at sundown. In such a situation, animals can return with many ticks from wild fields. Moreover, most farm families own two to three dogs for guarding their animals and belongings, and these dogs also roam freely in and out of yards. Therefore, it is not surprise that contacting with domestic animals is regarded as a main exposure risk," they noted in Biomed Research International
The researchers concluded that the wide distribution of the tick-borne infections and their serious nature meant that their transmission and risk factors "urgently needed to be further investigated."
[Editor's Note: The risk of tick borne diseases in China is not insignificant: a US student became paralysed after being bitten by a tick during a school trip to China and was awarded $42 million in damages against her school in a US court last year]