Know your ticks: Ornithodoros hermsi (no common name)

Ornithodoros hermsi ticks are something of a mystery. Although first identified in 1935 and thought to be the cause of tick-borne relapsing fever in British Columbia, they have proven elusive and, as a result, very little research has been conducted on them in this country.

What we do know is that this soft-bodied, night-feeding tick typically remains attached to its host for less than half an hour. Unlike blacklegged ticks, which feed once in order to transition from one life stage to the next, nymphal and adult Ornithodoros hermsi ticks are known to feed multiple times before transitioning. Since these bites mostly occur while their victims are asleep, they are sometimes misattributed to bed bugs.

Ornithodoros hermsi ticks feed mostly on small mammals including bats but Canadian researchers believe that birds may also play an important role in maintaining and dispersing these ticks in BC. Because they tend to hang out in burrows, caves, or beneath abandoned or uninhabited buildings during the day, coming out at night to feed before returning once again to their daytime haunts, it's characteristic that people infected with relapsing tick fever have recently spent time sleeping in tents, cabins, cottages or summer homes.

These ticks are known to live for up to 10 years and can go for months or even years between blood meals. They can also pass the bacteria responsible for tick-borne relapsing fever on to the next generation through their eggs.

Life cycle of Ornithodoros hermsi. Image courtesy of CDC.

Ornithodoros hermsi ticks have been found at many places in the mountainous regions of the BC Interior -- they tend to prefer altitudes of between 450 and 550 metres -- and are suspected to be the cause of relapsing tick fever in that province. However, it must be noted that this suspicion is based largely on findings out of the western US where Ornithodoros hermsi ticks have been recorded from Washington down to California. A direct connection between relapsing tick fever and Ornithodoros hermsi ticks has yet been proven in BC.

Relapsing tick fever is only found in BC and fewer than 20 cases have been recorded since the illness was first identified in 1933, likely due to relapsing tick fever being misdiagnosed as Lyme disease.

Diseases carried: Tick-borne relapsing tick fever (TBRF).

Where found: Mountainous regions of southern BC.

Photo courtesy of CDC.