A Brief History of the Major Rickettsioses in the Asia-Australia-Pacific Region: A Capstone Review for the Special Issue of .

The rickettsioses of the "Far East" or Asia-Australia-Pacific region include but are not limited to endemic typhus, scrub typhus, and more recently, tick typhus or spotted fever. These diseases embody the diversity of rickettsial disease worldwide and allow us to interconnect the various contributions to this special issue of Tropical Medicine and Infectious Disease. The impact of rickettsial diseases-particularly of scrub typhus-was substantial during the wars and "police actions" of the last 80 years.

Origins, Importance and Genetic Stability of the Prototype Strains Gilliam, Karp and Kato of .

Scrub typhus, a chigger-borne febrile illness, occurs primarily in countries of the Asia-Pacific rim and islands of the Western Pacific. The etiologic agent is the obligate intracellular rickettsial bacterium . Research on has relied on the availability of several prototype strains, which were isolated from human cases of scrub typhus in the 1940s and 1950s.

A Review of Scrub Typhus (Orientia tsutsugamushi and Related Organisms): Then, Now, and Tomorrow.

Scrub typhus and the rickettsial diseases represent some of the oldest recognized vector-transmitted diseases, fraught with a rich historical aspect, particularly as applied to military/wartime situations. The vectors of were once thought to be confined to an area designated as the Tsutsugamushi Triangle. However, recent reports of scrub typhus caused by species other than well beyond the limits of the Tsutsugamushi Triangle have triggered concerns about the worldwide presence of scrub typhus.

The Historical Case for and the Future Study of Antibiotic-Resistant Scrub Typhus.

Scrub typhus is an acute, and sometimes fatal, human febrile illness, typically successfully treated using chloramphenicol or one of the tetracyclines. Over the past several years, descriptions of strains of with reduced susceptibility to antibiotics have appeared. Because case-fatality ratios approached 50% during the pre-antibiotic era, antibiotic-resistant scrub typhus is concerning.

A Spatiotemporal Database to Track Human Scrub Typhus Using the VectorMap Application.

Scrub typhus is a potentially fatal mite-borne febrile illness, primarily of the Asia-Pacific Rim. With an endemic area greater than 13 million km2 and millions of people at risk, scrub typhus remains an underreported, often misdiagnosed febrile illness. A comprehensive, updatable map of the true distribution of cases has been lacking, and therefore the true risk of disease within the very large endemic area remains unknown.

The prevalence of rickettsial and ehrlichial organisms in Amblyomma americanum ticks collected from Ohio and surrounding areas between 2000 and 2010.

The lone star tick, Amblyomma americanum, feeds upon a variety of hosts and is a known vector of several human pathogens. In Ohio, populations of A. americanum have been expanding their range and increasing in abundance and distribution, thereby elevating the public health concerns regarding bites from this species.

Endemic scrub typhus-like illness, Chile.

We report a case of scrub typhus in a 54-year-old man who was bitten by several terrestrial leeches during a trip to Chiloé Island in southern Chile in 2006. A molecular sample, identified as related to Orientia tsutsugamushi based on the sequence of the16S rRNA gene, was obtained from a biopsy specimen of the eschar on the patient's leg. Serologic analysis showed immunoglobulin G conversion against O.

Genotypic identification of Acanthamoeba sp. isolates associated with an outbreak of acanthamoeba keratitis.

Purpose: To determine whether increased rates of Acanthamoeba keratitis (AK) are due to changes in municipal water treatment or to emergence of a more pathogenic strain of Acanthamoeba.

Methods: Previous sequence analysis of the 18S ribosomal DNA of Acanthamoeba isolates resulted in the identification of 15 different genotypic classes. These analyses indicate that AK cases are associated predominantly ( approximately 97%) with a single genotype (designated T4) of Acanthamoeba and rarely with other genotypes (eg, T3 and T11).

Scrub typhus: the geographic distribution of phenotypic and genotypic variants of Orientia tsutsugamushi.

Orientia tsutsugamushi is the etiological agent of scrub typhus, an acute, mite-borne, febrile illness that occurs in the Asia-Pacific region. Historically, strain characterization used serological analysis and revealed dramatic antigenic diversity. Eyeing a recommendation of potential vaccine candidates for broad protection, we review geographic diversity and serological and DNA prevalences.

Geographic distribution and genetic diversity of the Ehrlichia sp. from Panola Mountain in Amblyomma americanum.

Background: A novel Ehrlichia, closely related to Ehrlichia ruminantium, was recently discovered from Panola Mountain State Park, GA, USA. We conducted a study to determine if this agent was recently introduced into the United States.

Methods: We developed a sensitive PCR assay based on the conserved gltA (citrate synthase) gene and tested DNA samples extracted from 1964 field-collected and 1835 human-biting Amblyomma americanum from 23 eastern states of the USA.

Infections caused by pathogenic free-living amebas (Balamuthia mandrillaris and Acanthamoeba sp.) in horses.

This article describes amebic infections in 4 horses: granulomatous amebic encephalitis caused by Balamuthia mandrillaris and Acanthamoeba culbertsoni and systemic infections caused by Acanthamoeba sp. The former infection occurred in 1 of 4 horses spontaneously without any underlying conditions; the latter amebic infection was perhaps "opportunistic" considering the visceral involvement by this protozoan in association with Aspergillus sp. and/or Escherichia coli and Pseudomonas sp.

Fatal granulomatous Acanthamoeba encephalitis mimicking a stroke, diagnosed by correlation of results of sequential magnetic resonance imaging, biopsy, in vitro culture, immunofluorescence analysis, and molecular analysis.

Amebic infections involving the central nervous system are rare and difficult to diagnose. Magnetic resonance imaging (MRI) at timed intervals may be helpful, where scans reveal enhancing lesions and increased signal. We report a unique case of granulomatous amebic encephalitis that was proven pathologically with progressive radiological findings on MRI.

History of U.S. military contributions to the study of rickettsial diseases.

Rickettsial diseases have affected the military throughout history. Efforts such as those of the Joint U.S.

Identification and distribution of Acanthamoeba species genotypes associated with nonkeratitis infections.

Acanthamoeba is a free-living protozoan genus found in a wide variety of natural habitats, including water, soil, and air. Pathogenic isolates of Acanthamoeba are medically relevant as the causative agent of sight- threatening Acanthamoeba keratitis (AK), serious infections of other organs, and fatal granulomatous amebic encephalitis. Previous work employing DNA sequences of nuclear and mitochondrial small-subunit rRNA genes (SSU rRNA genes) determined the genotypic diversity of Acanthamoeba and found that many named species of Acanthamoeba are associated with particular genotypes.

Molecular and physiological evaluation of subtropical environmental isolates of Acanthamoeba spp., causal agent of Acanthamoeba keratitis.

Previous molecular examination of Acanthamoeba spp. has resulted in the determination of distinct genotypes in this genus (designated T1-T12, T14). Genotype T4 has been responsible for the majority of cases of Acanthamoeba keratitis.

Serologic evidence of infection with ehrlichiae and spotted fever group rickettsiae among residents of Gag Island, Indonesia.

The causative agents of scrub and murine typhus are considered endemic to Indonesia. However, the presence of spotted fever group rickettsiae and ehrlichiae have not been previously described in this country. During an investigation of arthropod-borne diseases on Gag Island, located northwest of the island of New Guinea in eastern Indonesia, the prevalence of antibody to the etiologic agents of monocytic ehrlichiosis, spotted fever rickettsiosis, and scrub and murine typhus were determined.

Evidence of Rickettsia typhi and the potential for murine typhus in Jayapura, Irian Jaya, Indonesia.

Murine typhus (etiologic agent: Rickettsia typhi) is endemic to Indonesia, especially on the highly populated island of Java. A survey of rodents from Irian Jaya, the eastern-most province of Indonesia, indicated striking geographic variation in risk factors associated with murine typhus. Murid rodents (n = 112) collected from two villages in the Arso district of northeastern Irian Jaya, were found to be free of ectoparasites normally associated with transmission of R.

The past and present threat of rickettsial diseases to military medicine and international public health.

Morbidity and mortality caused by rickettsioses have had a major influence on military activities and public health for >2000 years. The threat posed by the rickettsioses is reviewed, focusing on the impact and epidemiology of those that have adversely influenced wartime operations and the current challenges posed by these diseases. With their uneven worldwide distribution, the discovery of drug-refractory strains of Orientia tsutsugamushi, the increased threat of their use in acts of bioterrorism, frequent deployment of troops to regions of endemicity, and exposures due to increased humanitarian missions, these diseases continue to be a threat to military personnel in the field.