Tickborne diseases found in Montana

Rocky Mountain Spotted Fever (RMSF) – testing performed in-house: RMSF is usually identified by clinical diagnosis prior to antibody development. It is an acute illness where the patient presents for healthcare with signs and symptoms that can be severe.
The CDC has an excellent RMSF Training Module: Clinical Diagnosis and Treatment for Healthcare Providers.
MTPHL will test acute serum samples (collected 1-2 weeks from start of illness) and convalescent serum samples (collected 2-10 weeks later). Paired sera are required to establish diagnosis (4-fold increase in titer).
Single acute serum specimens collected 60 days past date of onset will not be tested.

Colorado Tick Fever (CTF) – testing performed at CDC: Acute phase serum specimens (collected < 14 days from symptom onset) or CSF (if suspected CNS involvement) can be tested by RT-PCR for viral RNA as antibody production is delayed until 14-21 days after onset of symptoms.

Convalescent serum (≥ 14 days after symptom onset) can be used for antibody testing.

If possible, acute and convalescent sera should be collected at least 2 weeks apart, with the convalescent sample collected at least 3 weeks after symptom onset.
Diagnosis is based on a seroconversion or a 4-fold rise in antibody titers using a plaque reduction neutralization test (PRNT). Colorado Tick Fever Virus Pocket Guide
Specimens should be submitted to MTPHL and will then be referred to the CDC Arbovirus Diagnostic Laboratory. Final test reports may not be available for at least 3 weeks after specimen receipt at CDC.

Tickborne Relapsing Fever (TBRF) – testing performed at CDC: The causative agent for TBRF is Borrelia hermsii, which is found in Montana. The following links may be useful for providers in clinical diagnosis based on patient presentation of disease Be Aware of Tick-Borne Relapsing Fever and Relapsing Fever Information for Clinicians.
Sera from patients with TBRF may cross-react and yield false-positive results for Lyme disease because of similar proteins between the causative organisms. A diagnosis of TBRF should be considered for patients with positive Lyme disease serology who have not been in areas endemic for Lyme disease.
Borrelia molecular detection can be performed on serum samples collected within 21 days of symptom onset and preferably before or within one day of treatment. Sera taken in the convalescent period (≥ 21 days after symptom onset) may be tested by EIA although early antibiotic treatment may limit the antibody response.

Tularemia – testing performed in-house: Tularemia is caused by the organism Francisella tularensis and can be difficult to diagnose. Naturally occurring infections of Tularemia have been reported from all states except Hawaii and is known to be transmitted by tick or deer fly bites.
Patients with acute illness should be managed based on clinical suspicion as antibodies are often not detectable until 2-3 weeks after symptom onset.
Laboratory diagnosis is made by seroconversion from negative to positive antibodies in paired sera. A negative serologic test collected too soon after illness onset does not exclude the diagnosis of tularemia. Paired sera are required to establish diagnosis (4-fold increase in titer).
The acute serum should be collected within 7 days of onset followed by a convalescent serum collected 2-3 weeks later.
MTPHL will hold acute serum samples until a convalescent serum is received. If a convalescent serum is not received after 4 weeks, the acute serum will be turned out as Test Not Performed.
Both IgM and IgG antibodies may remain detectable for several years following resolution of disease.
Because cross-reacting antibodies occur, a Brucella test is performed along with every Tularemia test.

Tickborne disease found in the United States

Many other tickborne diseases found across the United States may be diagnosed based on the patient’s travel history. Information can be found at Tickborne Diseases of the United States | Tick-borne Diseases | Ticks | CDC and A Reference Manual for Healthcare Providers
Lyme Disease – Borrelia burgdorferi: Although not endemic in Montana, Lyme disease testing is performed at the Montana Public Health Laboratory using the modified two-tier test (MTTT) strategy. If the patient has not traveled outside of Montana, a diagnosis of TBRF should be considered for patients with positive Lyme disease serology.

World-wide travel -associated tickborne infections can be found at Tickborne Diseases Abroad | Tick-borne Diseases | Ticks | CDC

Montana Public Health Laboratory offers Tick ID. Please submit the tick in a sterile container and use test code Misc Tick.