By Jessica Hamzelou
azvan Cornel Constantin / Alamy
Tick-borne diseases are on the rise in the US – but programmes to monitor the spread of ticks and the pathogens they carry are underfunded and patchy, according to a survey of professionals working in the area. The findings are “disconcerting”, says Emily Mader at Cornell University in New York, who led the work.
In 2018, ticks were responsible for 47,743 reported cases of human disease in the US, according to the US Centers for Disease Control and Prevention. Lyme disease is the most common – and in fact is the most common vector-borne disease in the US. “But there are many others that are less well known,” says Mader.
Some ticks can carry the Powassan virus, for example, which can cause encephalitis. “It has a high fatality rate,” says Mader. “Those that do survive often have long-term issues because it attacks the nervous system.”
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Mader and her colleagues surveyed 140 people working in the US on the control of vector-borne diseases, including academics and people at local, county and state public health and vector-control agencies. All participants were asked about their tick surveillance and control programmes, including how the prevalence of ticks is assessed, how ticks are screened for disease-causing pathogens and any difficulties teams encountered in undertaking these programmes.
Three-quarters of respondents said they had a programme to detect the presence of ticks, but only 26 per cent reported having an initiative to test ticks for potentially harmful pathogens. And only 12 per cent reported having a tick control programme in place.
“Unfortunately, it’s a pretty patchy system across the country,” says Mader. “There’s no uniform approach to doing tick surveillance.” When asked, those who completed the survey “universally said they need more funding”, she says.
“The fact that we don’t know what pathogens are at what level in what ticks is worrisome,” says Dina Fonseca at Rutgers, the State University of New Jersey. Without routine surveillance, we won’t know which pathogens are responsible for human diseases or how to best advise people to protect themselves.
“Different species of ticks act at different times of the day, in different places and you come into contact with them in different circumstances,” says Fonseca. “The guidelines are different for different species.”
Consistently funded tick surveillance plays a vital role in detecting new outbreaks of ticks and potential diseases. “One hotspot we found in 2017 let us know that there was an invasive tick in the country,” says Mader. After a woman found herself covered in ticks on her sheep farm, she went to her local mosquito control office. When the team performed genetic tests on the tick, they found it was native to Asia. The tick can reproduce asexually, so a single female can produce 3000 more ticks, quickly leading to an infestation, says Mader. “It has [since] been detected in 12 states.”
“If you don’t have that data, you can’t warn the public. You can’t tell them about the risk,” she says.
Journal reference: Journal of Medical Entomology, DOI: 10.1093/jme/tjaa094
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