Biology:Ehrlichia chaffeensis
| Ehrlichia chaffeensis | |
|---|---|
Scientific classification 
| |
| Domain: | Bacteria |
| Phylum: | Pseudomonadota |
| Class: | Alphaproteobacteria |
| Order: | Rickettsiales |
| Family: | Ehrlichiaceae |
| Genus: | Ehrlichia |
| Species: | E. chaffeensis
|
| Binomial name | |
| Ehrlichia chaffeensis Anderson et al. 1992
| |
Ehrlichia chaffeensis is an obligate intracellular,[1] Gram-negative species of Rickettsiales bacteria.[2] It is a zoonotic pathogen transmitted to humans by the lone star tick (Amblyomma americanum).[3] It is the causative agent of human monocytic ehrlichiosis.[4]
Human monocytic ehrlichiosis caused by E. chaffeensis is known to spread through tick infection primarily in the Southern, South-central and Mid-Atlantic regions of the United States.[5] In recent years, the lone star tick has expanded its range along the East Coast to New England, putting more humans at risk for tick-borne infections.[6]
It is named for Fort Chaffee, where the bacterium was first discovered in blood samples of infected patients.[2]
Transmission cycle
E. chaffeensis is maintained in nature through a complex zoonotic relationship. The white-tailed deer (Odocoileus virginianus) is known to be the main competent reservoir for E. chaffeensis[1] and the lone star tick (Amblyomma americanum) is the principal vector for human transmission.[3] Some evidence shows that other organisms may serve as reservoirs for the bacteria such as domestic goats, domestic dogs, raccoons,[1] and coyotes.[5]
E. chaffeensis can be transmitted to uninfected tick larvae when feeding on the blood from an infected host.[7] The infection is then maintained and can be transmitted to a reservoir organism or humans at the nymphal stage. Adult ticks can maintain the infection or be infected from feeding on the blood of an infected reservoir organism and may also pass E. chaffeensis to humans or other uninfected reservoir organisms.[1] Transovarial transmission is not known to occur, so eggs and unfed larvae are not believed to be infected.[7]
Experimental studies in the related species Ehrlichia japonica have suggested that the conserved effector TRP120 promotes sustained bacteremia needed for efficient tick acquisition, providing a possible molecular explanation for maintenance of the tick–mammal transmission cycle in Ehrlichia.[8]
Pathogenesis
E. chaffeensis causes human monocytic ehrlichiosis and is known to infect monocytes.[1] It has also been known to infect other cell types such as lymphocytes, atypical lymphocytes, myelocytes, and neutrophils, but monocytes appear to best harbor the infection.[1]
E. chaffeensis has also been shown to infect canines both naturally[6] and artificially.[9] Symptoms in canine infections are hard to differentiate between E. chaffeensis infection and E. canis, which is the species of Ehrlichia that most commonly affects canines.[9]
Signs and symptoms
Patients display early symptoms within 1 to 2 weeks after tick infection. Early symptoms include fever, headache,[10] malaise, low-back pain, or gastrointestinal symptoms.[3] Some patients may also have myalgias or arthralgias, and an estimated 10–40% of patients may develop coughing, pharyngitis, diarrhea, vomiting, abdominal pain, and changes in mental status.[1]
Diagnosis or detection
A variety of procedures have been used to detect E. chaffeensis in humans and reservoir organisms. Most commonly, serologic testing and PCR amplification are used.[1][3]
Treatment
E. chaffeensis is susceptible to tetracyclines.[11] Doxycycline is the treatment of choice for suspected human monocytotropic ehrlichiosis in adults and children of all ages, and treatment should be started as soon as the disease is suspected rather than delayed pending laboratory confirmation.[12] Patients are typically treated for at least 5 to 7 days and until 72 hours after fever has resolved with evidence of clinical improvement.[13]
See also
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Ganguly, S (2008). "Tick-borne ehrlichiosis infection in human beings". Journal of Vector Borne Diseases 45 (4): 273–280. PMID 19248653. http://www.mrcindia.org/journal/issues/454273.pdf.
- ↑ 2.0 2.1 Ehrlichia+chaffeensis at the US National Library of Medicine Medical Subject Headings (MeSH)
- ↑ 3.0 3.1 3.2 3.3 Allan, B. F. (2012). "Blood meal analysis to identify reservoir hosts for amblyomma americanum ticks". Emerging Infectious Diseases 16 (3): 433–440. doi:10.3201/eid1603.090911. PMID 20202418.
- ↑ "Human monocytic ehrlichiosis in children". Pediatr. Infect. Dis. J. 26 (6): 475–9. June 2007. doi:10.1097/INF.0b013e318042b66c. PMID 17529862.
- ↑ 5.0 5.1 Barker, R. W. (2000). "Naturally occurring ehrlichia chaffeensis infection in coyotes from oklahoma". Emerging Infectious Diseases 6 (5): 477–80. doi:10.3201/eid0605.000505. PMID 10998377.
- ↑ 6.0 6.1 Little, S. E. (2007, January). New developments in managing vector-borne diseases. Retrieved from http://www.iknowledgenow.com/tocnavc2007smallanimal.cfm
- ↑ 7.0 7.1 Long, S. W. (2003). "Evaluation of transovarial transmission and transmissibility of Ehrlichia chaffeensis (Rickettsiales: Anaplasmataceae) in Amblyomma americanum (Acari: Ixodidae)". Journal of Medical Entomology 40 (6): 1000–1004. doi:10.1603/0022-2585-40.6.1000. PMID 14765684.
- ↑ Zhang, Tsian; Chien, Rory C.; Budachetri, Khemraj; Lin, Mingqun; Boyaka, Prosper; Huang, Weiyan; Rikihisa, Yasuko (2024). "Ehrlichia effector TRP120 manipulates bacteremia to facilitate tick acquisition". mBio 15 (4): e00476-24. doi:10.1128/mbio.00476-24. PMID 38501870.
- ↑ 9.0 9.1 Baneth, G. (2010). Ehrlichia and anaplasma infections. Paper presented at World small animal veterinary congress. Retrieved from http://www.ivis.org/proceedings/wsava/2010/d12.pdf
- ↑ Baddour, L.M. (3 August 2011). "Newly discovered ehrlichia species implicated in human infection". New England Journal of Medicine Group, Massachusetts Medical Society. https://www.jwatch.org/id201108030000002/2011/08/03/newly-discovered-ehrlichia-species-implicated.
- ↑ Paddock, Christopher D.; Childs, James E. (2003). "Ehrlichia chaffeensis: a prototypical emerging pathogen". Clinical Microbiology Reviews 16 (1): 37–64. doi:10.1128/CMR.16.1.37-64.2003. PMID 12525424.
- ↑ Biggs, Holly M.; Behravesh, Casey Barton; Bradley, Kristy K.; Dahlgren, F. Scott; Drexler, Nausheen A.; Dumler, J. Stephen; Folk, Sarah M.; Kato, Carol Y. et al. (2016). "Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis — United States". MMWR Recommendations and Reports 65 (2): 1–44. doi:10.15585/mmwr.rr6502a1. PMID 27172113.
- ↑ "Clinical Care of Ehrlichiosis". 15 May 2024. https://www.cdc.gov/ehrlichiosis/hcp/clinical-care/index.html.
Wikidata ☰ Q5348629 entry
 |  |
