A bug that causes a rare form of relapsing fever has been identified in a tick collected in Ireland for the first time.

The bug, a strain of Borrelia bacteria, was identified in a tick collected in Portumna, Co Galway.

The Borrelia miyamotoi pathogen, first identified in ticks from Japan in 1995, is distantly related to the bacteria that cause Lyme disease.

The initial symptom of the illness is usually a red skin rash but if left untreated, further symptoms can follow including a fever, muscle pain, joint swelling and temporary paralysis of the facial muscles.

The find is reported in a study published in the Plos One scientific journal by a team of Irish scientists, including researchers from University College Dublin and University College Cork.

They say their research shows ticks in Ireland are infected by a diversity of disease-carrying Borrelia bacteria. The results also show Borrelia-infected ticks exist in the southeast, an area hitherto not considered to be significantly tick-infested and hence not considered an area of risk to humans from Lyme disease.

Infected ticks

Five per cent of ticks collected for the study were found to be carrying infectious Borrelia, with rates varying from 2 per cent in Killarney, Co Kerry, to 12 per cent in Portumna. All of the sampling sites, which also included Glenveagh, Co Donegal, Glendalough, Co Wicklow and Clifden, Co Galway, collected ticks infected with some form of Borrelia.

The HSE estimates there are about 100 to 200 cases of Lyme disease a year but patient groups and some doctors say this is too low. The new study appears to indicate some ticks could be transmitting another disease, which has similar symptoms to Lyme disease.

“It is likely if ticks have relapsing fever Borrelia, they are biting humans, and maybe we are ‘missing’ patients because no one is aware of relapsing fever in Ireland, and the current test does not pick up anyone with relapsing fever borreliosis,” said Prof Jack Lambert, one of the authors of the study.

High fever

Tick-borne relapsing fever is characterised by a high fever that lasts for a few days, goes away for a week, and then comes back. Though rare, the disease is found in western states of the US and in parts of Spain.

The disease normally goes away of itself, but severe cases are treated with antibiotics.

Health authorities say the best way to prevent infection from a tick bite is to take precautions when outdoors, such as wearing long trousers and tucking trouser legs into socks, and using tick repellents.