Scrub Typhus Outbreak in Chonburi Province, Central Thailand, 2013.

Investigation of a scrub typhus outbreak in Thailand during September 2013 found that 9.1% of Thai soldiers and 11.1% of residents living in areas surrounding training sites had antibodies against the causative agent, Orientia tsutsugamushi. Sequence analysis of O. tsutsugamushi from rodents and chiggers identified 7 genogroups and 3 genotypes.

Scrub typhus outbreak, northern Thailand, 2006-2007.

During a scrub typhus outbreak investigation in Thailand, 4 isolates of O. tsutsugamushi were obtained and established in culture. Phylogenetic analysis based on the 56-kDa type-specific antigen gene demonstrated that the isolates fell into 4 genetic clusters, 3 of which had been previously reported and 1 that represents a new genotype.

C-terminal polymorphism of Plasmodium falciparium merozoite surface protein-1 (MSP-1) from Tak Province, Thailand.

This study was undertaken to ascertain the extent of polymorphism in the C-terminal region of Plasmodium falciparum merozoite surface protein (MSP-1) from 119 malaria patients in Tak Province on the western border of Thailand, who were admitted to the Bangkok Hospital for Tropical Diseases, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand. P. falciparum infection was confirmed by microscopic examination of peripheral blood smears. Clinical manifestations were categorized into 2 groups: uncomplicated (94 cases) and complicated/severe (25 cases). A 1,040 basepair fragment of P. falciparum MSP-1 gene was compared with MSP-1 of reference strains retrieved from GenBank. The consensus sequences of MSP-1 block 16 showed it belonged to MAD20 genotype, which is the major allele of falciparum malaria from the western border of Thailand. MSP-1 block 16 amino acid fragment could be separated into 2 groups: similar and dissimilar to reference sequence. Four variations in MSP-1 block 16 were -1494K, D1510G, D1556N, and K1696I. MSP-1 block 16 diversity is not significantly associated with clinical manifestation although MAD 20 genotype is the predominant genotype in this area. The genetic data of MSP1 gene of faciparum malaria isolated from western Thai border contribute to the existing genetic database of Thai P. falciparum strain.

Efficacy of plant essential oils for the repellents against chiggers (Leptotrombidium imphalum) vector of scrub typhus.

Scrub typhus caused by the Orientia tsutsugamushi. Rodents, particularly rats, serve as principal reservoir hosts. Infection in man is transmitted by the, chigger bite. Repellents provide an effective agent of protecting individuals from chigger. In the present study 6 plant essential oils were tested for evaluation of their repellent activity against the chigger, Leptotrombidium imphalum. The results showed that Clove oil was significantly more effective than others with ED50 and EC50 of 0.420 mg and 2.3%, followed by Zingiber oil (8.458 mg and 42.3%), Vetiver oil (19.582 mg and 97.9%), Turmeric oil (24.343 mg and 121.7%), Orange oil (27.310 mg and 136.6%) and Boesenbergia oil (30.486 mg and 152.4%). These results suggested that Clove oil was the most efficient repellent against chigger which is the vector for scrub typhus.

Genotype diversity and distribution of Orientia tsutsugamushi causing scrub typhus in Thailand.

Scrub typhus, caused by antigenically disparate isolates of Orientia tsutsugamushi, is a widely distributed mite-borne human disease in the Asia Pacific region. Information regarding the heterogeneity of the immunodominant 56-kDa type-specific antigen (TSA) gene is crucial for the design and evaluation of scrub typhus-specific diagnostic assays and vaccines. Using indirect immunofluorescence assays (IFA) and PCR assays, O. tsutsugamushi was detected samples from rodents and patients with fever of unknown origin obtained from six provinces of Thailand during 2004 to 2007. Sequences were determined for a fragment of the 56-kDa TSA gene, and the relationship between these sequences and those previously determined were assessed. The phylogenetic analyses of partial 56-kDa TSA gene sequences demonstrated wide diversity and distribution of O. tsutsugamushi genotypes in Thailand. Furthermore, the genetic diversity grouped the scrub typhus agents into two commonly and five infrequently found genotypes within six provinces of Thailand. The two most commonly found genotypes of O. tsutsugamushi described in this study do not associate with the prototype strains that are widely used for the design and evaluation of diagnostic assays and vaccine candidates. Thus, these new genotypes should be considered for future scrub typhus assay and vaccine development.

Department of Defense influenza and other respiratory disease surveillance during the 2009 pandemic.

The Armed Forces Health Surveillance Center's Division of Global Emerging Infections Surveillance and Response System (AFHSC-GEIS) supports and oversees surveillance for emerging infectious diseases, including respiratory diseases, of importance to the U.S. Department of Defense (DoD). AFHSC-GEIS accomplishes this mission by providing funding and oversight to a global network of partners for respiratory disease surveillance. This report details the system's surveillance activities during 2009, with a focus on efforts in responding to the novel H1N1 Influenza A (A/H1N1) pandemic and contributions to global public health. Active surveillance networks established by AFHSC-GEIS partners resulted in the initial detection of novel A/H1N1 influenza in the U.S. and several other countries, and viruses isolated from these activities were used as seed strains for the 2009 pandemic influenza vaccine. Partners also provided diagnostic laboratory training and capacity building to host nations to assist with the novel A/H1N1 pandemic global response, adapted a Food and Drug Administration-approved assay for use on a ruggedized polymerase chain reaction platform for diagnosing novel A/H1N1 in remote settings, and provided estimates of seasonal vaccine effectiveness against novel A/H1N1 illness. Regular reporting of the system's worldwide surveillance findings to the global public health community enabled leaders to make informed decisions on disease mitigation measures and controls for the 2009 A/H1N1 influenza pandemic. AFHSC-GEIS's support of a global network contributes to DoD's force health protection, while supporting global public health.

Plasmodium falciparum phenotypic and genotypic resistance profile during the emergence of Piperaquine resistance in Northeastern Thailand.

Malaria remains a public health problem in Thailand, especially along its borders where highly mobile populations can contribute to persistent transmission. This study aimed to determine resistant genotypes and phenotypes of 112 Plasmodium falciparum isolates from patients along the Thai-Cambodia border during 2013-2015. The majority of parasites harbored a pfmdr1-Y184F mutation. A single pfmdr1 copy number had CVIET haplotype of amino acids 72-76 of pfcrt and no pfcytb mutations. All isolates had a single pfk13 point mutation (R539T, R539I, or C580Y), and increased % survival in the ring-stage survival assay (except for R539I). Multiple copies of pfpm2 and pfcrt-F145I were detected in 2014 (12.8%) and increased to 30.4% in 2015. Parasites containing either multiple pfpm2 copies with and without pfcrt-F145I or a single pfpm2 copy with pfcrt-F145I exhibited elevated IC90 values of piperaquine. Collectively, the emergence of these resistance patterns in Thailand near Cambodia border mirrored the reports of dihydroartemisinin-piperaquine treatment failures in the adjacent province of Cambodia, Oddar Meanchey, suggesting a migration of parasites across the border. As malaria elimination efforts ramp up in Southeast Asia, host nations militaries and other groups in border regions need to coordinate the proposed interventions.

Development of multiplex PCR for neglected infectious diseases.

Scrub typhus, murine typhus, and leptospirosis are widely neglected infectious diseases caused by Orientia tsutsugamushi, Rickettsia typhi, and pathogenic Leptospira spp., respectively. Patients usually present with non-specific symptoms and therefore are commonly diagnosed with acute undifferentiated febrile illness. Consequently, patients face delayed treatment and increased mortality. Antibody-based serological test currently used as gold standard has limitations due to insufficient antibody titers, especially in the early phase of infection. In this study, we aimed to develop multiplex PCR to combine 3 primer pairs that target specific genes encoding 56-kDa TSA of O. tsutsugamushi, 17-kDa antigen of R. typhi, and LipL32 of L. Interrogans and evaluate its performance in comparison to the standard serological tests. Using EDTA blood samples of known patients, the sensitivity and specificity of our multiplex PCR was 100% and 70%, respectively. In addition, the assay was able to diagnose the co-infection of scrub typhus and leptospirosis. The assay may be useful in identifying causative agents during the early phase of these diseases, enabling prompt and appropriate treatment.

The importance of militaries from developing countries in global infectious disease surveillance.

Military forces from developing countries have become increasingly important as facilitators of their government's foreign policy, taking part in peacekeeping operations, military exercises and humanitarian relief missions. Deployment of these forces presents both challenges and opportunities for infectious disease surveillance and control. Troop movements may cause or extend epidemics by introducing novel agents to susceptible populations. Conversely, military units with disease surveillance and response capabilities can extend those capabilities to civilian populations not served by civilian public health programmes, such as those in remote or post-disaster settings. In Peru and Thailand, military health organizations in partnership with the military of the United States use their laboratory, epidemiological, communications and logistical resources to support civilian ministry of health efforts. As their role in international affairs expands, surveillance capabilities of militaries from developing countries should be enhanced, perhaps through partnerships with militaries from high-income countries. Military-to-military and military-to-civilian partnerships, with the support of national and international civilian health organizations, could also greatly strengthen global infectious disease surveillance, particularly in remote and post-disaster areas where military forces are present.

The development of HIV research laboratories in the Royal Thai Army Medical Department.

The development of HIV research laboratories at the Armed Forces Research Institute of Medical Sciences (AFRIMS), Royal Thai Army Medical Department in supporting of HIV-1 vaccine trials in Thailand was implemented in 1991. The collaboration between AFRIMS, Royal Thai Army Medical Department, and the US Military HIV Research Program with the ultimate goal to conduct the HIV-1 vaccine trial phase III. The HIV serology lab was set up for surveillance program in military recruits. Then, there was a need to strengthen more on the existing laboratories by training personnel to cope with the confidentiality of the lab results, specimen processing and data management which are critical. Later on, the necessary laboratory for measuring of vaccine immunogenicity was developed, such as lymphoproliferation assay. Additionally, a molecular biology lab was also developed. The HIV research laboratory management must include an ability to deal with some problems, such as late specimen receiving, fluctuating of power supply, technical staffs maintained. Good laboratory practices and safety must be strictly implemented. Communication network among facilities also played an important role in HIV laboratory strengthening at AFRIMS.

Dot-ELISA Rapid Test Using Recombinant 56-kDa Protein Antigens for Serodiagnosis of Scrub Typhus.

We developed a rapid dot-enzyme-linked immunosorbent assay (dot-ELISA) using the combination of recombinant 56-kDa protein antigens that exhibited broad reactivity with serum antibodies against the four most prevalent strains (Karp, Kato, Gilliam, and TA763) of Orientia tsutsugamushi. The assay is rapid (30 minutes), and can be done at room temperature, and results can be read by the naked eye. Only a simple shaker is required to wash the membrane. Sera from 338 patients suspected of being ill with scrub typhus from rural hospitals around Thailand were tested using this dot-ELISA. Seventy-five (22.2%) patients were found to be positive. The sensitivity and specificity of dot-ELISA were determined using the indirect immunofluorescent assay (IFA) test as the gold standard, with the cutoff titer of immunoglobulin peroxidase conjugate M (IgM)/G (IgG) greater than 1:400/1:400. The dot-ELISA had a sensitivity of 98.5%, a specificity of 96.3%, a positive predictive value of 86.7%, and a negative predictive value of 99.6% for the acute-phase specimens. The results indicate that dot-ELISA rapid test using recombinant 56-kDa protein antigen was comparable with the IFA test and may be very useful for the diagnosis of scrub typhus in rural hospitals, where IFA is not available.

Subcellular localization of rickettsial invasion protein, InvA.

To understand further the molecular basis of rickettsial host cell invasion, Rickettsia prowazekii invasion gene homolog (invA) has been characterized. Our previous experiments have shown that InvA is an Ap5A pyrophosphatase, a member of the Nudix hydrolase family, which is up-regulated during the internalization, early growth phase, and exit steps during rickettsial mammalian cell infection. In addition to the molecular characterization, subcellular localization of InvA was investigated. InvA-specific antibodies were raised in mice and used for immunoelectron microscopy. The generated antibodies were shown to recognize InvA and by immunogold labeling showed InvA in the cytoplasm of rickettsiae. A cytoplasmic location for InvA would allow for a rapid response to any internal substance and efficient functioning in hydrolysis of toxic metabolic by-products that are accumulated in the rickettsial cytoplasm during host cell invasion. Protecting bacteria from a hazardous environment could enhance their viability and allow them to remain metabolically active, which is a necessary step for the rickettsial obligate intracellular lifestyle.

Fighting the good fight: the role of militaries in malaria elimination in Southeast Asia.

Despite significant progress in malaria control in the Greater Mekong Subregion (GMS), malaria is still endemic, with more than 30 million people infected annually. Important gaps remain in case management, service delivery, prevention, and vector control, particularly in hard-to-reach mobile populations. Rapidly evolving drug resistance has created a new urgency to move aggressively toward elimination. However, no clear and cost-effective strategy has been identified. Although GMS militaries are under-recognized as a malaria transmission reservoir, they are an important focal point for elimination activities, given their high mobility, frequent malaria exposure, and potential for asymptomatic carriage. At the same time, military organizational capacity and proximity to other mobile populations could facilitate elimination efforts if relevant political barriers could be overcome. Here, we review considerations for military involvement in regional malaria elimination efforts.

Rickettsia, Ehrlichia, Anaplasma, and Bartonella in ticks and fleas from dogs and cats in Bangkok.

Flea and tick specimens (5-10 fleas or ticks) on dogs and cats from various sites in Bangkok were tested by polymerase chain reaction and DNA sequencing to detect DNA of bacteria Rickettsia (gltA and 17 kDa genes), Anaplasmataceae (16S rRNA gene), and Bartonella (pap31 and its genes). We confirmed that Rickettsia sp. related to Rickettsia felis was detected in 66 of 98 (67.4%) flea specimens from dogs, whereas 8 Bartonella henselae and 2 Bartonella clarridgeiae were detected in 10 of 54 (18.5%) flea specimens from cats. Further, this work provides the first evidence of 10 Ehrlichia canis (3.3%), 7 Anaplasma platys (2.3%), and 2 Wolbachia spp. (0.66%) in 304 Rhipicephalus sanguineus tick specimens in Thailand.

Isolation and characterization of Orientia tsutsugamushi from rodents captured following a scrub typhus outbreak at a military training base, Bothong district, Chonburi province, central Thailand.

Orientia tsutsugamushi, an obligate intracellular Gram-negative bacterium, is the causative agent of scrub typhus, a vector-borne disease transmitted by infected chiggers (trombiculid mite larvae). In 2002, an outbreak of scrub typhus occurred among Royal Thai Army troops during the annual field training at a military base in Bothong district, Chonburi province, central Thailand. This report describes the outbreak investigation including its transmission cycle. Results showed that 33.9% of 174 trained troops had scrub typhus-like signs and symptoms and 9.8% of those were positive for O. tsutsugamushi-specific antibodies by indirect fluorescence antibody assay. One hundred thirty-five rodents were captured from this training area, 43% of them had antibodies against O. tsutsugamushi. Six new O. tsutsugamushi isolates were obtained from captured rodent tissues and successfully established in cell culture. Phylogenetic studies showed that these six isolates were either unique or related to a native genotype of previously described isolates from Thailand.

Isolation and propagation of the Ap-Variant 1 strain of Anaplasma phagocytophilum in a tick cell line.

The first tissue culture isolates of the unique Anaplasma phagocytophilum strain, Ap-Variant 1, were obtained in the Ixodes scapularis tick-derived cell line ISE6. Two isolates were from goat blood samples: one from a goat infected with I. scapularis ticks from Rhode Island and a second from a goat infected by serial passage of blood from the first infected goat. Eight isolates were made directly from I. scapularis ticks collected from white-tailed deer in Minnesota and represent the first isolations of an Anaplasma species directly from ticks. Each of the 10 isolates had a 16S rRNA gene sequence identical to that previously described for Ap-Variant 1, but differences within the ank gene were found that suggest natural variation. Prevalence of Anaplasma in the Minnesota ticks was 63.9%; 23 of 36 ticks tested by PCR were positive. Six of the tick-derived isolates were obtained from a set of 18 PCR-positive ticks, for a 33.3% isolation success rate. The conservation of host tropism among the Rhode Island and Minnesota isolates of Ap-Variant 1 was examined by use of experimental infections of mice and a goat. A Minnesota tick-derived isolate (MN-61-2) was used to inoculate naïve animals, and this isolate was able to infect a goat but unable to infect each of five mice, confirming that the Minnesota isolates have the same host tropism as Ap-Variant 1 from the northeastern United States. Light and electron microscopy of the Ap-Variant 1 isolate MN-61-2 in ISE6 cells showed cytoplasmic inclusions characteristic of A. phagocytophilum with pleomorphic bacteria in membrane-bound vacuoles and both electron-dense and electron-lucent forms.

The importance of militaries from developing countries in global infectious disease surveillance.

Military forces from developing countries have become increasingly important as facilitators of their government's foreign policy, taking part in peacekeeping operations, military exercises and humanitarian relief missions. Deployment of these forces presents both challenges and opportunities for infectious disease surveillance and control. Troop movements may cause or extend epidemics by introducing novel agents to susceptible populations. Conversely, military units with disease surveillance and response capabilities can extend those capabilities to civilian populations not served by civilian public health programmes, such as those in remote or post-disaster settings. In Peru and Thailand, military health organizations in partnership with the military of the United States use their laboratory, epidemiological, communications and logistical resources to support civilian ministry of health efforts. As their role in international affairs expands, surveillance capabilities of militaries from developing countries should be enhanced, perhaps through partnerships with militaries from high-income countries. Military-to-military and military-to-civilian partnerships, with the support of national and international civilian health organizations, could also greatly strengthen global infectious disease surveillance, particularly in remote and post-disaster areas where military forces are present.

The Rickettsia prowazekii invasion gene homolog (invA) encodes a Nudix hydrolase active on adenosine (5')-pentaphospho-(5')-adenosine.

The genomic sequence of Rickettsia prowazekii, the obligate intracellular bacterium responsible for epidemic typhus, reveals an uncharacterized invasion gene homolog (invA). The deduced protein of 18,752 Da contains a Nudix signature, the specific motif found in the Nudix hydrolase family. To characterize the function of InvA, the gene was cloned and overexpressed in Escherichia coli. The expressed protein was purified to near homogeneity and subsequently tested for its enzymatic activity against a series of nucleoside diphosphate derivatives. The purified InvA exhibits hydrolytic activity toward dinucleoside oligophosphates (Np(n)N; n > or = 5), a group of cellular signaling molecules. At optimal pH 8.5, the enzyme actively degrades adenosine (5')-pentaphospho-(5')-adenosine into ATP and ADP with a K(m) of 0.1 mM and k(cat) of 1.9 s(-1). Guanosine (5')-pentaphospho-(5')-guanosine and adenosine-(5')-hexaphospho (5')-adenosine are also substrates. Similar to other Nudix hydrolases, InvA requires a divalent metal cation, Mg(2+) or Zn(2+), for optimal activity. These data suggest that the rickettsial invasion protein likely plays a role in controlling the concentration of stress-induced dinucleoside oligophosphates following bacterial invasion.

Transcriptional analysis of Rickettsia prowazekii invasion gene homolog (invA) during host cell infection.

An invasion gene homolog, invA, of Rickettsia prowazekii has recently been identified to encode a member of the Nudix hydrolase subfamily which acts specifically on dinucleoside oligophosphates (Np(n)N; n >/= 5), a group of cellular signaling molecules known as alarmones. InvA is thought to enhance intracellular survival by regulating stress-induced toxic nucleotide levels during rickettsial infection. To further characterize the physiological function of InvA, the gene expression pattern during various stages of rickettsial intracellular growth was investigated. Using semiquantitative reverse transcription-PCR (RT-PCR) and real-time fluorescent probe-based quantitative RT-PCR, a differential expression profile of invA during rickettsial host cell infection was examined. The invA transcript temporarily increased during the early period of infection. Expression of rickettsial groEL, a molecular indicator of cellular stresses, was also shown to be upregulated during the early period of infection. Furthermore, invA was cotranscribed in a polycistronic message with rrp, a gene encoding the response regulator protein homolog, which is a part of a two-component signal transduction system. These results support our earlier findings that under such stress conditions dinucleoside oligophosphate pyrophosphatase may function as a buffer, enhancing rickettsial survival within the cytoplasm of a eukaryotic cell. The expression of rickettsial dinucleoside oligophosphate pyrophosphatase may be regulated by a part of the two-component signal transduction system similar to that described for response regulators in other bacterial systems.