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Phylogenetic Analysis of Francisella tularensis Group A.II Isolates from 5 Patients with Tularemia, Arizona, USA, 2015–2017

Year: 2019

Type: article

Abstract: We examined 5 tularemia cases in Arizona, USA, during 2015-2017.All were caused by Francisella tularensis group A.II. Genetically similar isolates were found across large spatial and temporal distances, suggesting that group A.II strains are dispersed across long distances by wind and exhibit low replication rates in the environment.F rancisella tularensis, a Tier 1 select agent (1), has 3 subspecies: tularensis (type A), holarctica (type B), and mediasiatica (Appendix 1 Figure, https://wwwnc.cdc.gov/EID/article/25/5/18-0363-App1.pdf).In humans, disease is caused by type A and type B. Type B is found throughout the Northern Hemisphere, type A only in North America, and mediasiatica only in central Asia (2).Type A is divided into 2 distinct subgroups, A.I and A.II (Appendix 1 Figure), that have little geographic overlap (3,4).A.II is found primarily in the mountainous region of western North America (3,4) and A.I throughout the central eastern regions and along the West Coast (3-5).Observational human data and limited experimental mouse data suggest A.II is less virulent than A.I but potentially more virulent than type B (6,7).Here, we describe 5 patients in Arizona, USA, during 2015-2017 with cases of tularemia (1 fatal), all caused by A.II (Appendix 2, https://wwwnc.cdc.gov/EID/article/25/5/18-0363-App2.xlsx). The StudyCase-patient 1 was a 57-year-old previously healthy man who sought treatment July 12, 2015, for chills and an acute onset of fever >40°C.Five days before symptom onset, while camping at the northern rim of Grand Canyon National Park, he noted a small wound at the lateral aspect of his left elbow consistent with an insect bite.Cellulitis with regional lymphadenopathy developed on his left forearm, extending to the left axillary region.After surgical irrigation, debridement of the wound (August 8), and oral doxycycline treatment upon discharge, the patient fully recovered.Case-patient 2 was a 55-year-old previously healthy woman who sought treatment on July 20, 2015, for sore throat and an acute onset of fever >40°C.She reported no outdoor activity except being in a Coconino County park 4 days before symptom onset.Despite receiving treatment with amoxicillin, her fever persisted; she returned 4 days later with myalgia, fatigue, headaches, and emesis.Her therapy was switched to sulfamethoxazole/trimethoprim, amoxicillin/clavulanate, and ceftriaxone.A 2-day hospitalization revealed left axillary lymphadenopathy with associated cellulitis in her left chest wall and breast.Her fever resolved with intravenous ceftriaxone and gentamicin.She received oral doxycycline upon discharge and fully recovered.Case-patient 3 was a 73-year-old Coconino County woman with previous health conditions.She sought treatment in the summer of 2016 and died several days later (Appendix 2 Table).Details about this case-patient are presented elsewhere (8).Case-patient 4 was a 24-year-old previously healthy woman from Navajo County who sought treatment in November 2016.A cat bite was the suspected source of infection, but the cat was euthanized without testing.Severe Phylogenetic Analysis of Francisella tularensisGroup A.II Isolates from 5 Patients with Tularemia, Arizona, USA,

Source: Emerging infectious diseases

DOI: 10.3201/eid2505.180363