Tick-borne infections that predominate in the U.S. include: Lyme disease (Borrelia burgdorferi) Human monocytic ehrlichiosis (Ehrlichia chaffeensis) Human granulocytic anaplasmosis (Anaplasma phagocytophilum) Rocky Mountain spotted fever (Rickettsia rickettsii) Tularemia (Francisella tularensis) Babesiosis (Babesia microti) Relapsing Fever (Borrelia hermsii, B. parkeri, B. turicatae; louse borne relapsing fever due to B. recurrentis) Colorado tick fever (Coltivirus)

Tick Vectors Hard Ticks Ixodes Amblyomma Dermacentor Rhipicephalus Soft Ticks Ornithodorus http://www.lymenet.org/

Rocky Mountain Spotted Fever Originally described in the 1800’s in Western U.S. but currently more prevalent in the South Atlantic region Caused by Rickettsia rickettsii The number of cases is increasing with the most cases ever reported in the U.S. occurring in 2004. The ecology of rickettsial infection is also changing R. rickettsii has been detected in species of ticks (R. sanguineous; GA and AZ) not previously considered vectors of the infection and in non-typical areas of the U.S. (Arizona) R. parkeri recently implicated in case of human infection in U.S.

RMSF - Ecology D. variabilis D. andersoni Vector D. variabilis (dog tick) in East D. andersoni (Rocky Mtn. wood tick) in the West Adult ticks responsible for transmission Rhipicephalus sanguineus (common brown dog tick) = newly described vector (NEJM. 2005) transovarial and transstadial transmission. Small mammals = as a reservoir for infection of ticks D. andersoni www.cdc.gov

Distribution and Number of Cases of RMSF 1514 reported cases in 2004 Distribution and Number of Cases of RMSF 1514 reported cases in 2004. NC accounted for 35% of cases www.cdc.gov.libproxy.lib.unc.edu/mmwr/preview/mmwrhtml/rr5504a1.htm www.cdc.gov Incidence highest in male children (5-9 years) Highest incidence in SE/South Central U.S 90% of cases in April through September

R. rickettsii Member of the spotted fever group (SFG) SFG also includes the human pathogens: R. akari, R. parkeri, R. felis as well as 5 other species Gram negative obligate intracellular coccobacillus (0.7 – 2.0 x 0.3 – 0.5 um) Infects all organs of the tick (salivary glands – horizontal transmission, ovaries – transovarial transmission) Transmitted to humans during feeding via saliva

Diagnosis – Direct Detection Culture not routine DFA staining of skin biopsy provides earliest laboratory diagnosis. Positive before serologic tests but not everyone gets a rash. 70% sensitive, but lower if receiving antibiotic therapy (must perform within 48 hours of therapy). Not routinely available. PCR Most sensitive method for early diagnosis. Performed on skin biopsy. Available at CDC Immunoperoxidase stain www.cdc.gov

Diagnosis - Serology Antibody detectable 7 – 9 days after onset. IFA = gold standard (94–100% sensitive, ~100% specific) Diagnostic titer is >/= 1:64 Antibody persists for years therefore testing of acute and convalescent sera in parallel recommended LA = rapid serologic test (71–94% sensitive and 96–99% specific) Detects primarily IgM Diagnostic titer is >/=1:128 Titers decline to non-detectable within a few months Positive result suggests recent infection Anti-human IgG-FITC Patient IgG R. rickettsii

Human Ehrlichioses Includes 3 recently described infections Human Monocytic Ehrlichiosis (HME) Human Granulocytic Anaplasmosis (HGA; formerly HE) E. ewingii ehrlichiosis Subclinical to fatal infection, typically - febrile syndrome with headache, myalgias and malaise Transmitted by several species of hard tick

HME Transmission Vector = A. americanum (lone star tick) nymph and adult Ticks may be co-infected with E. ewingii or B. lonestari Incidence Southcentral and southeastern states 482 cases reported between 1997 and 2001 (0.7/million) More common in adults, median age 50 years 70–80% of patients recall tick bite 70% of cases occur in May - July www.cdc.gov.libproxy.lib.unc.edu/mmwr/preview/mmwrhtml/rr5504a1.htm

E. chaffeensis Non-motile, gram negative, obligate intracellular bacteria Replicate in cytoplasm of white blood cells - monocytes Form intracytoplasmic morulae containing up to 50 organisms Inhibit phagosome-lysosome fusion

HME-Diagnosis Direct Detection Serology Blood smear = insensitive Culture not routine PCR = 80 –87% sensitive during acute disease on whole blood samples. Amplification from other fluids is of unknown sensitivity. Available via Referral testing at Mayo medical laboratories Detects E. Chaffeensis, E. ewingii and A. phagocytophilum Serology IFA with E. chaffeensis antigen (94-100% sens with paired samples) Confirmed case = seroconversion/4x change in IgG titer on acute and convalescent sera collected 2 to 3 week apart IgM testing sensitivity not well defined. Probable case = IgG >1:64 and compatible disease Ab often not detectable during 1st 7 days of illness Cross reactions with E. ewingii

Human Granulocytic Anaplasmosis HGA first described in 1994 as a severe acute febrile illness in individuals from the upper midwest Similar to HME clinically but organisms present in PMNs rather than monocytes Caused by Anaplasma phagocytophilum Infection is treatable with appropriate therapy however, delay in diagnosis and treatment may be associated with significant morbidity/mortality

HGA Vectors I. scapularis, I pacificus, I. spinipalpis and I. ricinus Nymphal ticks most likely to bite humans (small size) Coinfection with A. phagocytophilum and B. burgdorferi and/or Babesia microti is not uncommon Epidemiology Most cases of HGA reported in upper Midwest and Northeast Peak in April through August - coincides with activity of nymphal Ixodes ticks Disease primarily diagnosed in older individuals (median age = 51 years) www.cdc.gov

HGA - Diagnosis Direct Detection Wright or Giemsa stained blood smear 20 – 80% sensitive at presentation. Usually, less than 0.1% of PMNs infected Disappear from blood after 24 – 72 hours of treatment PCR Most sensitive method for acute infection – 60 to >90% Available via referral testing at Mayo labs Culture - not routinely available Serology Antibody detectable by 2 weeks of onset therefore not always useful for diagnosis of acute infection (30 – 60% sensitive, 70 – 95% during convalescence (1:64 cutoff). Most sensitive method after acute infection Confirmed case = seroconversion/4x change in IgG titer on acute and convalescent sera collected 2 to 3 week apart Probable = compatible illness with positive IgG on single sample

E. Ewingii Ehrlichiosis E. ewingii = gram negative, intracellular bacterium found in neutrophils of dogs and infected humans First reported in 1999 Transmitted by A. americanum in SE U.S. Few cases identified, disease more likely in immunosuppressed hosts Clinical manifestations similar to HME but usually milder Molecular diagnosis typically used; serologic tests can not differentiate between E. ewingii and E. chaffeensis

Borrelia burgdorferi Fastidious, microaerophilic spirochete 0.2 x 30um, linear chromosome + 9 circular and 12 linear plasmids Slow growing (12-24 hour doubling time), cultured in liquid medium 3 pathogenic species B. burgdorferi– U.S. B. afzelii – Europe and Asia B. garinii – Europe and Asia

Lyme Disease - Ecology Vectors I. scapularis, I. pacificus, I. ricinus Nymphal stage = predominant vector for human infection Other species infected but not common human biters Reservoirs White-footed mouse important for infection of larvae (no transovarial transmission) White tail deer important in the tick life cycle. Transstadial transmission occurs Human disease corresponds to distribution of tick vector, except in the SE www.cdc.gov www.cdc.gov www-bml.ucdavis.edu/.../Ixodespacificus.jpg

Lyme Disease Epidemiology Most commonly reported arthropod-borne disease in North America and Europe Most cases of in NE and upper midwest Approximately 20,000 cases reported annually Most infections occur in May – July Most frequent in boys age 5-19 and persons >30 years old www.cdc.gov

Lyme Disease – Diagnosis Based clinical findings, exposure risk, laboratory studies © DermAtlas; http://www.DermAtlas.org ©2008 UpToDate®

Lyme Disease - Diagnosis Direct Detection Culture not commonly used PCR available - Most sensitive in leading edge of skin lesion, joint fluid, CSF Serology 2 tiered algorithm Screen with polyvalent ELISA. C6 ELISA Confirm positives/equivocals by Western Blot. IgG and IgM blots available. Do not perform IgM blot after 4 weeks due to false positives. IgM: 2 of p24, 39, 41 IgG: 5 of p18, 21, 28, 30, 39, 41, 45, 58, 66, 93 Most patients have strong Ab response after 1 month. CSF may be positive in acute neuroborreliosis, less sensitive in chronic neuroborreliosis. Assess CSF/serum index

Issues with Lyme Serology Standardization False positives Other borrelial infections and spirochetal diseases, viral illness, autoimmune disease, cross-reactions due to intestinal commensals and gram negative UTI pathogens 5% of normal population will test positive by ELISA Low sensitivity in early disease Up to 6 – 8 week seronegative window Serology 20 –30% sensitive during EM, 70-80% on repeat Co-infection with B. microti or A. phagocytophilum may occur The vast majority of patients with early disseminated and late Lyme disease are seropositive Late neurologic disease (peripheral neuropathy) not associated with CSF antibody Test result for people without objective signs of lyme disease or a lack of exposure to endemic areas are of low predictive value. Vaccine recipients may give positive ELISA and some reactivity on WB for several years

Southern Tick-Associated Rash Illness EM-like rash associated with bite of A. americanum B. lonestari found in 1 – 3% of ticks SE and S central U.S. Doesn’t appear to crossreact serologically with B. burgdorferi