Ehrlichia chaffeensis

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Anaplasmataceae
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Alpha Proteobacteria
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chaffeensis

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]

Rickettsiales Order of bacteria

The Rickettsiales, informally called rickettsias, are an order of small Alphaproteobacteria that are endosymbionts of eukaryotic cells. Some are notable pathogens, including Rickettsia, which causes a variety of diseases in humans, and Ehrlichia, which causes diseases in livestock. Another genus of well-known Rickettsiales are the Wolbachia, which infect approximately two-thirds of all arthropods and nearly all filarial nematodes. Genetic studies support the endosymbiotic theory according to which mitochondria and related organelles developed from members of this group.

Bacteria A domain of prokaryotes – single celled organisms without a nucleus

Bacteria are a type of biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep portions of Earth's crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, and only about half of the bacterial phyla have species that can be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology.

<i>Amblyomma americanum</i> species of arachnid

Amblyomma americanum, also known as the lone star tick, the northeastern water tick, or the turkey tick, is a type of tick indigenous to much of the eastern United States and Mexico, that bites painlessly and commonly goes unnoticed, remaining attached to its host for as long as seven days until it is fully engorged with blood. It is a member of the phylum Arthropoda, class Arachnida. The adult lone star tick is sexually dimorphic, named for a silvery-white, star-shaped spot or "lone star" present near the center of the posterior portion of the adult female shield (scutum); adult males conversely have varied white streaks or spots around the margins of their shields.

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Genetic studies support the endosymbiotic theory that a subset of these organisms evolved to live inside mammalian cells as mitochondria to provide cellular energy to the cells in return for protection and sustenance. ATP production in the rickettsia is biochemically identical to that in mammalian mitochondria.

Human monocytic ehrlichiosis caused by E. chaffeensis is known to spread through tick infection primarily in the southern, southcentral and mid-Atlantic regions of the United States. [5] In recent years the lone star tick has expanded its range up the East Coast to New England, putting more humans at risk for tick-borne infections. [6]

It is named for Fort Chaffee where the bacteria 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] There is some evidence that other organisms may serve as reservoirs for the bacteria such as domestic goats, domestic dogs, raccoons, [1] and coyotes. [5]

White-tailed deer species of mammal

The white-tailed deer, also known as the whitetail or Virginia deer, is a medium-sized deer native to the United States, Canada, Mexico, Central America, and South America as far south as Peru and Bolivia. It has also been introduced to New Zealand, Cuba, Jamaica, Hispaniola, Puerto Rico, the Bahamas, the Lesser Antilles, and some countries in Europe, such as Finland, the Czech Republic, Romania and Serbia. In the Americas, it is the most widely distributed wild ungulate.

E. chaffeensis can be transmitted to non-infected 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 non-infected reservoir organisms. [1] Transovarial transmission is not known to occur so eggs and unfed larvae are not believed to be infected. [7]

Pathogenesis

Ehrlichia chaffeensis Echaff.jpg
Ehrlichia chaffeensis

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. [8] Symptoms in canine infections are hard to differentiate between E. chaffeensis infection and Ehrlichia canis, which is the species of Ehrlichia that most commonly affects canines. [8]

Signs and symptoms

Patients display early symptoms within 1 to 2 weeks after tick infection. Early symptoms include fever, headache, [9] malaise, low-back pain, or gastrointestinal symptoms. [3] Some patients may also have myalgias, 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. [1] Doxycycline treatment is suggested for any patients presenting symptoms of an Ehrlichia infection during the appropriate season and potential tick exposure. [9]

See also

Related Research Articles

Ehrlichiosis (; also known as canine rickettsiosis, canine hemorrhagic fever, canine typhus, tracker dog disease, and tropical canine pancytopenia is a tick-borne disease of dogs usually caused by the organism Ehrlichia canis. Ehrlichia canis is the pathogen of animals. Humans can become infected by E. canis and other species after tick exposure. German Shepherd Dogs are thought to be susceptible to a particularly severe form of the disease, other breeds generally have milder clinical signs. Cats can also be infected.

Tick-borne diseases, which afflict humans and other animals, are caused by infectious agents transmitted by tick bites. Tick-borne illnesses are caused by infection with a variety of pathogens, including rickettsia and other types of bacteria, viruses, and protozoa. Because individual ticks can harbor more than one disease-causing agent, patients can be infected with more than one pathogen at the same time, compounding the difficulty in diagnosis and treatment. As of 2016, 16 tick-borne diseases of humans are known.

<i>Bartonella</i> genus of bacteria

Bartonella is a genus of Gram-negative bacteria. It is the only genus in the family Bartonellaceae. Facultative intracellular parasites, Bartonella species can infect healthy people, but are considered especially important as opportunistic pathogens. Bartonella species are transmitted by vectors such as ticks, fleas, sand flies, and mosquitoes. At least eight Bartonella species or subspecies are known to infect humans.

<i>Dermacentor variabilis</i> species of arachnid

Dermacentor variabilis, also known as the American dog tick or wood tick, is a species of tick that is known to carry bacteria responsible for several diseases in humans, including Rocky Mountain spotted fever and tularemia. It is one of the most well-known hard ticks. Diseases are spread when it sucks blood from the host, which could take several days for the host to experience some symptoms.

<i>Babesia</i> genus of protozoan parasites

Babesia, also called Nuttallia, is an Apicomplexan parasite that infects red blood cells, transmitted by ticks. Originally discovered by the Romanian bacteriologist Victor Babeș, over 100 species of Babesia have since been identified.

A canine vector-borne disease (CVBD) is one of "a group of globally distributed and rapidly spreading illnesses that are caused by a range of pathogens transmitted by arthropods including ticks, fleas, mosquitoes and phlebotomine sandflies." CVBDs are important in the fields of veterinary medicine, animal welfare, and public health. Some CVBDs are of zoonotic concern.

<i>Anaplasma phagocytophilum</i> species of bacterium

Anaplasma phagocytophilum is a Gram-negative bacterium that is unusual in its tropism to neutrophils. It causes anaplasmosis in sheep and cattle, also known as tick-borne fever and pasture fever, and also causes the zoonotic disease human granulocytic anaplasmosis.

Ehrlichiosis is a tickborne bacterial infection, caused by bacteria of the family Anaplasmataceae, genera Ehrlichia and Anaplasma. These obligate intracellular bacteria infect and kill white blood cells.

Ehrlichia is a genus of rickettsiales bacteria that is transmitted to vertebrates by ticks. These bacteria cause the Ehrlichiosis infection, which is considered zoonotic, because the main reservoirs for the disease are animals.

Heartwater is a tick-borne rickettsial disease of domestic and wild ruminants. It is caused by Ehrlichia ruminantium - an intracellular gram-negative coccal bacterium. The disease is spread by bont ticks, which are members of the genus Amblyomma. Affected mammals include cattle, sheep, goats, antelope, and buffalo, but the disease has the biggest economic impact on cattle production in affected areas. The disease's name is derived from the fact that fluid can collect around the heart or in the lungs of infected animals.

Southern tick-associated rash illness

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Human granulocytic anaplasmosis human disease

Human granulocytic anaplasmosis (HGA) is a tick-borne, infectious disease caused by Anaplasma phagocytophilum, an obligate intracellular bacterium that is typically transmitted to humans by ticks of the Ixodes ricinus species complex, including Ixodes scapularis and Ixodes pacificus in North America. These ticks also transmit Lyme disease and other tick-borne diseases.

Human monocytotropic ehrlichiosis human disease

Human monocytotropic ehrlichiosis (HME) is a form of ehrlichiosis associated with Ehrlichia chaffeensis. This bacterium is an obligate intracellular pathogen affecting monocytes and macrophages.

Ehrlichiosis ewingii infection is an infectious disease caused by an intracellular bacteria, Ehrlichia ewingii. The infection is transmitted to humans by the tick, Amblyomma americanum. This tick can also transmit Ehrlichia chaffeensis, the bacteria that causes human monocytic ehrlichiosis (HME).

African tick bite fever spotted fever that has material basis in Rickettsia africae, which is transmitted by ticks

African tick bite fever (ATBF) is a bacterial infection spread by the bite of a tick. Symptoms may include fever, headache, muscles pains, and a rash. At the site of the bite there is typically a red skin sore with a dark center. Onset usually occur 4–10 days after the bite. Complications are rare, however may include joint inflammation. Some people do not develop symptoms.

Ehrlichia canis is an obligate, intracellular bacterium that acts as the causative agent of Ehrlichiosis, a disease most commonly affecting canine species. This pathogen is present throughout the United States, South America, Asia, and Africa. First defined in 1935, E. canis emerged in the United States in 1963 and its presence has since been found in all 48 contiguous United States. Reported primarily in dogs, E. canis has also been documented in felines and humans where it is transferred most commonly via Rhipicephalus sanguineus, the brown dog tick.

Ehrlichia Wisconsin HM543746 is an unnamed tick bacterium that spread through Minnesota and Wisconsin in 2009 and is similar to Ehrlichia muris.

The Heartland virus (HRTV) is a tick-borne phlebovirus of the Bhanja virus serocomplex discovered in 2009. The Lone Star Tick transmits the virus to people when feeding on blood. As of 2017, only five Midwestern United States have reported 20 human infections, namely Arkansas, Indiana, Missouri, Oklahoma, and Tennessee; symptoms resemble those of two other tick-borne infections ehrlichiosis and anaplasmosis. The reservoir host is unknown, but deer, raccoon, coyotes, and moose in 13 different states have antibody titers against the virus.

References

  1. 1 2 3 4 5 6 7 8 9 Ganguly, S (2008). "Tick-borne ehrlichiosis infection in human beings" (PDF). Journal of Vector Borne Diseases. 45 (4): 273–280.
  2. 1 2 Ehrlichia+chaffeensis at the US National Library of Medicine Medical Subject Headings (MeSH)
  3. 1 2 3 4 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. PMC   3322017 . PMID   20202418.
  4. Schutze GE, Buckingham SC, Marshall GS, et al. (June 2007). "Human monocytic ehrlichiosis in children". Pediatr. Infect. Dis. J. 26 (6): 475–9. doi:10.1097/INF.0b013e318042b66c. PMID   17529862.
  5. 1 2 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. PMC   2627953 . PMID   10998377.
  6. 1 2 Little, S. E. (2007, January). New developments in managing vector-borne diseases. Retrieved from http://www.iknowledgenow.com/tocnavc2007smallanimal.cfm
  7. 1 2 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.
  8. 1 2 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
  9. 1 2 Baddour, L. M. (2011). Newly discovered ehrlichia species implicated in human infection. Journal Watch Infectious Diseases