Saturday, November 2, 2013

New Species of Lyme Bacterium in California


A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases

Date: Wed 30 Oct 2013
Source: San Ramon Patch [edited]

Fall and winter bring on young active ticks, and with that the risk of
disease, according to a newsletter released by the Contra Costa
Mosquito and Vector Control District. "In addition to spreading Lyme
disease, researchers now say ticks are also responsible for
transmitting a previously unknown disease that is related to Rocky
Mounted spotted fever," the release stated. The new bacterium was
recorded in 4 human cases statewide, with 2 of those cases in Contra
Costa County.

The newsletter reads:

"The _Rickettsia philipii_ bacterium is transmitted by the Pacific
Coast tick (_Dermacentor occidentalis_), which is one of the 3 primary
ticks that can be found across California. So far scientists have
found ticks infected with this new bacterium in at least 8 California

"While a small percentage of adult Pacific Coast ticks have tested positive for the disease thus far, researchers find that young nymphs
are testing positive as well. This makes prevention very important
because these young ticks are very small and very difficult to see.
Symptoms can include fever, headache, fatigue, and what appears to be
a blackened scab at the site of a tick bite.

"In addition to the discovery of this new form of spotted fever,
California researchers also confirm that the western black-legged tick
(_Ixodes pacificus_), which is the primary tick responsible for
spreading Lyme disease in California, is also capable of transmitting
a newly recognized type of tickborne relapsing fever caused by the
bacterium _Borrelia miyamotoi_. The symptoms of this illness include a
fever that comes and goes, as well as headache and muscle aches.

"As of the writing of this article, there have not been any reports of
humans infected with _Borrelia miyamotoi_ in California, but
scientists say the fact that a tick that already exists in California
is capable of transmitting this disease makes it more important than
ever for outdoor enthusiasts to take the risk of tickborne illness
very seriously.

"Using a tick repellent, wearing light-colored long sleeve clothing
that is carefully tucked in at the waist and socks, and doing a tick
check after exposure to wooded or grassy areas are all important ways
to prevent tick bites and reduce the risk of tickborne illness. Pet
owners should consider using a veterinarian-approved flea and tick
product on pets that roam outdoors because it can reduce the chance a
pet might bring an infected tick home. Pet owners should also perform
tick checks on pets as another way to reduce disease risk within a

"Prevention is the key to reducing risk from tickborne diseases. In
Contra Costa County, only about 2 percent of ticks are infected with
Lyme disease. With such low risk of disease, there is no guarantee
that a person who is bitten by an infected tick will also become

"Various studies indicate that the tick must feed on a person for 2-24
hours before any disease-causing bacterium can be transferred. That is
why prevention is so important. While tickborne disease may be
unlikely in our county, learn to recognize the symptoms and consult
your doctor if they appear after a tick bite.

"Anyone who finds a tick on a person should remove the tick by pulling
gently, but firmly, with tweezers placed as close to the surface of
the skin as possible. The Contra Costa Mosquito & Vector Control
District does provide a free tick identification service for county
residents, but does not test ticks for disease, as such tests cannot
determine whether or not the tick has actually transmitted the

"The District can provide a list of commercial laboratories that
citizens may contact for tick testing should they be bitten by a tick;
however at this time there are no current tests available for the
newest tickborne disease caused by _R. philipii_ bacterium."

[Byline: Jane McInnis]

Communicated by:
ProMED-mail from HealthMap Alerts

[The following in reference to spotted fever caused by _Rickettsia
philipii_ is extracted from the Monterey County, California health
department journal Vida Sana, dated 23 Aug 2013, available at

"_Rickettsia philipii_ (formerly known as _Rickettsia_ 364D) is an
emerging human tickborne disease in California. In 2008, the 1st human
case was identified in a resident of Lake County, California. By the
end of 2012, 10 cases had been confirmed among residents of Lake,
Contra Costa, Monterey, Orange, and Santa Clara counties. There have
been 2 cases reported among Monterey County residents, one confirmed
and one suspected.

"_R. philipii_ is a member of the spotted fever group _Rickettsia_
(SFGR). Symptoms of _R. philipii_ rickettsiosis include fever, rash,
eschar, headache, myalgia, anemia, thrombocytopenia, and/or hepatic
transaminase elevation. The eschar is usually an isolated ulcer with
raised erythematous margins and a black core (see photo at the end of
this update [at the URL above]). It is often surrounded by generalized
edema and erythema. Symptoms develop 3 to 14 days after exposure at
the site of a known or presumed tick bite.

"_R. philipii_ is transmitted by Pacific Coast ticks (_Dermacentor
occidentalis_, see photo at the end of this update [at the URL
above]). _R. philipii_ has been detected in ticks collected from
Alameda, Contra Costa, Lake, Los Angeles, Mendocino, Monterey, Orange,
Riverside, San Bernardino, San Mateo, Santa Clara, Shasta, and Ventura
counties. Adult Pacific Coast ticks are active January through June
and can be found in dry, grassy areas. Nymphal ticks are active May
through August and likely live in leaf litter and wood products. Both
adults and nymphs are thought to transmit _R. philipii_ to humans.
Tick attachment time prior to transmitting _R. philipii_ is likely
between 2 and 20 hours, which is shorter than seen with Western black
legged ticks and Lyme disease (greater than 24 hours).

"Treat suspected cases of _R. philipii_ rickettsiosis appropriately.
Doxycycline is the 1st line treatment for adults and children of all
  • Adults: 100 mg po q 12 hours
  • Children under 45 kg [99 lb]: 2.2 mg/kg body weight po bid
"Patients should be treated for at least 3 days after the fever
subsides and until there is evidence of clinical improvement. Standard
duration of treatment is 7-14 days. Do not delay treatment while
awaiting laboratory confirmation. Treatment decisions should be based
on epidemiologic and clinical evidence."

See also, CDC report "Other Tick-borne Spotted Fever Rickettsial
Infections" available at <>.

Maps of California can be seen at <> and

Contra Costa County, with a population of about 1 million in 2010, is
a suburban county in the San Francisco Bay Area of the US state of
California that is bounded on the south and west by Alameda County; on
the northwest by San Francisco Bay; on the north by San Pablo Bay and
Suisun Bay; and on the east by the San Joaquin River

A picture of _Dermacentor occidentalis_ (Pacific Coast tick) is
available at

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