Epidemic Typhus Research Articles

Scrub typhus, a disease with increasing threat in Guangdong, China.

There has been a rapid increase in the number of scrub typhus cases in Guangdong Province, China. For this reason, an epidemiologic study was conducted to understand the characteristics of scrub typhus epidemics in Guangdong. From 2006 to 2013, the incidence of human cases increased from 0.4321 to 3.5917 per 100,000 with a bimodal peak in human cases typically occurring between May and November. To detect the prevalence of Orientia tsutsugamushi among suspected human cases and rodents, we performed ELISA tests of IgM/IgG and nested PCR tests on 59 whole blood samples from the suspected cases and 112 spleen samples from the rodents. Suspected cases tested positive for anti-O. tsutsugamushi IgM and IgG 66.1% (39/59) and 50.8% (30/59) of the time, respectively. Additionally, 20.3% (12/59) of blood samples and 13.4% (15/112) of spleen samples were positive for PCR. Phylogenetic analysis revealed that there were four definable clusters among the 27 nucleotide sequences of the 56-kDa antigen genes: 44.4% Karp (12/27), 25.9% Kato (7/27), 22.2% Gilliam (6/27) and 7.4% TA763 (2/27). We concluded many suspected cases may result in diagnostic errors; therefore, it is necessary to perform laboratory tests on suspected cases in hospitals. The high infection rate of O. tsutsugamushi among the limited rodents tested suggested that further rodent sampling throughout the province is necessary to further define high-risk areas. Furthermore, the multiple co-circulating genotypes of O. tsutsugamushi play a key role in the pervasiveness of scrub typhus in the Guangdong area.

DR AVRAM JOZEF VINAVER (1862-1915) - PIONEER OF RADIOLOGY IN SERBIA.

Dr Abraham Joseph Vinaver (1862-1915), a Jew from Poland, was a pioneer of radiology in Serbia. He graduated from the Faculty of Medicine in Warsaw (1887), but lived and worked in abac (the Kingdom of Serbia) since 1890. Dr Abraham Joseph Vinarev - Career Development. He procured the first X-ray machine and developed radiological service in Sabac five years after the discovery of X-rays. These were the beginnings of radiology in Serbia. He introduced the application of artesian wells. Dr Abraham Joseph Vinarev - a Participant at the First Congress of Serbian Physicians and Naturalists, Belgrade 1904. "The diagnostic importance of X-rays in lung disease, especially in initial tuberculosis" and "Five Years of Treatment by X-Ray Machines" were the first works in the field of radiology in Serbia by this author. Dr Abraham Joseph Vinaver - Reserve Medical Officer in the Serbian Army. During the Balkan Wars, he was a volunteer with the rank of major engaged in military corps and he participated in the First World War as well. He died of malaria in 1915 in Gevgelija. "Dr Avram Vinaver"- Stanislav Vinarev. His dedication to work during the typhus epidemics was put into verses of a poem by his son Stanislav Vinarev. Dr Avram Vinaver Joseph was a noble man with a great heart, who selflessly sacrificed himself for the Serbian people and Serbia. He gave his contribution to the development of health services in Serbia, both in peacetime and wartime conditions. Dr Abraham Joseph Vinaver laid the foundations for today's radiology in Serbia.

Ehrlichia chaffeensis proliferation begins with NtrY/NtrX and PutA/GlnA upregulation and CtrA degradation induced by proline and glutamine uptake.

ABSTRACTHow the obligatory intracellular bacterium Ehrlichia chaffeensis begins to replicate upon entry into human monocytes is poorly understood. Here, we examined the potential role of amino acids in initiating intracellular replication. PutA converts proline to glutamate, and GlnA converts glutamate to glutamine. E. chaffeensis PutA and GlnA complemented Escherichia coli putA and glnA mutants. Methionine sulfoximine, a glutamine synthetase inhibitor, inhibited E. chaffeensis GlnA activity and E. chaffeensis infection of human cells. Incubation of E. chaffeensis with human cells rapidly induced putA and glnA expression that peaked at 24 h postincubation. E. chaffeensis took up proline and glutamine but not glutamate. Pretreatment of E. chaffeensis with a proline transporter inhibitor (protamine), a glutamine transporter inhibitor (histidine), or proline analogs inhibited E. chaffeensis infection, whereas pretreatment with proline or glutamine enhanced infection and upregulated putA and glnA faster than no treatment or glutamate pretreatment. The temporal response of putA and glnA expression was similar to that of NtrY and NtrX, a two-component system, and electrophoretic mobility shift assays showed specific binding of recombinant E. chaffeensis NtrX (rNtrX) to the promoter regions of E. chaffeensis putA and glnA. Furthermore, rNtrX transactivated E. chaffeensis putA and glnA promoter-lacZ fusions in E. coli. Growth-promoting activities of proline and glutamine were also accompanied by rapid degradation of the DNA-binding protein CtrA. Our results suggest that proline and glutamine uptake regulates putA and glnA expression through NtrY/NtrX and facilitates degradation of CtrA to initiate a new cycle of E. chaffeensis growth.

Inactivation of SAM-methyltransferase is the mechanism of attenuation of a historic louse borne typhus vaccine strain.

Louse borne typhus (also called epidemic typhus) was one of man's major scourges, and epidemics of the disease can be reignited when social, economic, or political systems are disrupted. The fear of a bioterrorist attack using the etiologic agent of typhus, Rickettsia prowazekii, was a reality. An attenuated typhus vaccine, R. prowazekii Madrid E strain, was observed to revert to virulence as demonstrated by isolation of the virulent revertant Evir strain from animals which were inoculated with Madrid E strain. The mechanism of the mutation in R. prowazekii that affects the virulence of the vaccine was not known. We sequenced the genome of the virulent revertant Evir strain and compared its genome sequence with the genome sequences of its parental strain, Madrid E. We found that only a single nucleotide in the entire genome was different between the vaccine strain Madrid E and its virulent revertant strain Evir. The mutation is a single nucleotide insertion in the methyltransferase gene (also known as PR028) in the vaccine strain that inactivated the gene. We also confirmed that the vaccine strain E did not cause fever in guinea pigs and the virulent revertant strain Evir caused fever in guinea pigs. We concluded that a single nucleotide insertion in the methyltransferase gene of R. prowazekii attenuated the R. prowazekii vaccine strain E. This suggested that an irreversible insertion or deletion mutation in the methyl transferase gene of R. prowazekii is required for Madrid E to be considered a safe vaccine.

Las zonas andinas de patología de phlebotomus

En las vertientes occidentales del centro y norte, y en algunos valles interandinos, en una faja de sierra entre los 800 y 300 metros de altura se encuentra dos enfermedades trasmitidas por Phlebotomus, la Verruga peruana y la Uta. El paludismo de los valles bajos sube hasta los 1800 metros en las vertientes occidentales y a más altura en los valles interandinos. El tifus exantemático epidémico de las partes altas de la sierra baja hasta alturas no determinadas todavía, sin llegar al desierto costanero.

The first clinical pharmacology unit in the world was probably founded in Vienna in 1911

The history of clinical pharmacology as a standalone medical field is a topic that comes up rather often at various clinical pharmacology symposia, perhaps because the recent discussion about its future [1,2] needs to be rooted in the past. While clinical pharmacology as a concept, in the guise of material medica, is centuries old [3], the term clinical pharmacology itself is rather young coming with the advent of synthetic and purified drugs at the beginning of the 20th century. Early partial progress in understanding the mechanisms of action allowed experimental pharmacology to translate its findings into clinical practice. The next leap in the development of clinical pharmacology came with the arrival of new drug groups (e.g. antibiotics, antihypertensives, cytostatics, psychoactive drugs) and the ability to measure drugs concentrations thanks to progress in analytical methods after World War II [4]. In one his papers on this topic, Aronson [3] places the origins of the term clinical pharmacology to 1914 in the English translation of the German textbook by Meyer & Gottlieb [5]. While the boom in clinical pharmacology with many standalone departments came after World War II, the first pioneering clinical pharmacology department applying knowledge gained by experimental pharmacology in clinical practice already existed before World War I. In contrast to departments founded in the second half of the 20th century which took on the multiple roles of clinical pharmacology as we know it today (pharmacokinetics, clinical trials and drug development, pharmacoepidemiology and drug safety, economics, etc.), the original departments were motivated by the sole goal of applying the recent findings of experimental pharmacology in clinical practice, and thus replacing the former purely empiric approach with a more scientific one. Until recently, we were convinced that the first physician to practice clinical pharmacology by applying knowledge acquired by experimental pharmacology in clinical practice was Professor Dr Emil Starkenstein (1884–1942) [6,7]. As a young associate professor (docent) of pharmacology at the German medical faculty of the German part of Charles University in Prague, at the time of World War I (1914–1918), Starkenstein served as a commander of the Army infectious disease hospital in Radom in Poland (Kommandant des k.u.k. Epidemiespitals in Radom), where he applied his knowledge of anti-inflammatory effects of Atophan (cinchophen) gained from his experimental work [8,9] to treat successfully epidemic typhus, reducing mortality to 2.5% from 16% [10,11]. In a similar fashion, he applied theoretical knowledge of the adsorption effects of carbo animalis in the treatment of dysentery and cholera [9]. On March 16 1918, Starkenstein presented a lecture titled Klinische Pharmakologie – Theorie und Praxis am Krankenbette (Clinical Pharmacology – Theory and practice at the patient's bedside) at a meeting of Austrian army physicians (‘Feldartzliche Abend’) in Lublin (Poland). In the same year, the full text of the lecture was published in the journal Therapie der Gegenwart [12]. Recently we came across publications by Dr Hans Januschke [13,14] that place the origins of both the term clinical pharmacology and the first pharmacology unit even earlier to 1911.

Rapid increase of scrub typhus: an epidemiology and spatial-temporal cluster analysis in Guangzhou City, Southern China, 2006-2012.

BackgroundScrub typhus has been increasingly reported in Southern China, and public health authorities are concerned about its increased incidence. Additionally, little evidence is available on the epidemiology of scrub typhus in Southern China. This study aims to analyze the epidemiological and geographic features of ST in Guangzhou City, Southern China, to guide the future prevention efforts.MethodsScrub typhus surveillance data in Guangzhou City during 2006–2012 were obtained from the Chinese National Communicable Disease Surveillance Network. We first conducted a descriptive analysis to analyze the epidemiological features of scrub typhus. Then we used space-time scan statistic based on a discrete Poisson model to detect and evaluate high-risk spatial-temporal clusters of scrub typhus.ResultsThere were 4,001 cases of scrub typhus in Guangzhou City during the study period. The incidence of scrub typhus increased from 3.29 per 100,000 in 2006 to 9.85 per 100,000 in 2012. A summer peak was observed in June and July with a second peak in September and October except year 2009 and 2011. The majority of the cases (71.4%) were among persons aged ≥40 years, and female incidence was higher than male incidence in persons ≥50 years. In the space-time analysis, high-risk clusters were concentrated in rural areas in Guangzhou City. Over the past 7 years, Haizhu District, an urban area, was found to be a high-risk cluster for the first time in 2012.ConclusionThe resurgence of scrub typhus epidemics in Guangzhou population in 2012 necessitates more effective measures for minimizing future epidemics. Consideration of high-risk population and historical spatial-temporal clusters may help prevent scrub typhus. The risk of scrub typhus in urban areas should not be neglected and needs more attention from public health authorities.

Drought and Epidemic Typhus, Central Mexico, 1655–1918

Epidemic typhus is an infectious disease caused by the bacterium Rickettsia prowazekii and transmitted by body lice (Pediculus humanus corporis). This disease occurs where conditions are crowded and unsanitary. This disease accompanied war, famine, and poverty for centuries. Historical and proxy climate data indicate that drought was a major factor in the development of typhus epidemics in Mexico during 1655–1918. Evidence was found for 22 large typhus epidemics in central Mexico, and tree-ring chronologies were used to reconstruct moisture levels over central Mexico for the past 500 years. Below-average tree growth, reconstructed drought, and low crop yields occurred during 19 of these 22 typhus epidemics. Historical documents describe how drought created large numbers of environmental refugees that fled the famine-stricken countryside for food relief in towns. These refugees often ended up in improvised shelters in which crowding encouraged conditions necessary for spread of typhus.

Nursing typhus victims in the Second World War, 1942-1944: a discussion paper

This article explores the care British nurses provided to victims of typhus during the Second World War. Typhus is associated with poverty and overcrowding. During wars in the pre-antibiotic era, civilians were particularly susceptible to epidemics, which military governments feared would spread to their troops. This discussion paper draws on archival data from three typhus epidemics in the Second World War to examine the expert work of British nurses in caring for victims during these potential public health disasters. The published sources for the paper include material from nursing and medical journals published between 1940-1947. Archival sources come from the National Archives in Kew, the Wellcome Library and the Army Medical Services Museum, between 1943-1945. Of particular interest is the correspondence with Dame Katharine Jones from nurses on active service overseas. Whilst epidemics of typhus are now rare, nurses in the present day may be required to care for the public in environments of extreme poverty and overcrowding, where life-threatening infectious diseases are prevalent. This article has demonstrated that it is possible for expert and compassionate nursing to alleviate suffering and prevent death, even when medical technologies are unavailable. Expert and compassionate care, adequate nutrition and hydration and attention to hygiene needs are crucial when there are limited pharmacological treatments and medical technologies available to treat infectious diseases. The appreciation of this could have implications for nurses working in current global conflicts.

The Biology and Taxonomy of Head and Body Lice—Implications for Louse-Borne Disease Prevention

Sucking lice (Phthiraptera: Anoplura) are obligate blood-feeding ectoparasites of placental mammals including humans. Worldwide, more than 550 species have been described and many are specific to a particular host species of mammal [1]. Three taxa uniquely parasitize humans: the head louse, body louse, and crab (pubic) louse. The body louse, in particular, has epidemiological importance because it is a vector of the causative agents of three important human diseases: epidemic typhus, trench fever, and louse-borne relapsing fever. Since the advent of antibiotics and more effective body louse control measures in the 1940s, these diseases have markedly diminished in incidence. However, due to 1) increasing pediculicide resistance in human lice, 2) reemergence of body louse populations in some geographic areas and demographic groups, 3) persistent head louse infestations, and 4) recent detection of body louse-borne pathogens in head lice, lice and louse-borne diseases are an emerging problem worldwide. This mini-review is focused on human body and head lice including their biological relationship to each other and its epidemiological relevance, the status and treatment of human louse-borne diseases, and current approaches to prevention and control of human louse infestations.

Discovery of a Protective Rickettsia prowazekii Antigen Recognized by CD8+ T Cells, RP884, Using an In Vivo Screening Platform

Rickettsia prowazekii has been tested for biological warfare due to the high mortality that it produces after aerosol transmission of very low numbers of rickettsiae. Epidemic typhus, the infection caused by these obligately intracellular bacteria, continues to be a threat because it is difficult to diagnose due to initial non-specific symptoms and the lack of commercial diagnostic tests that are sensitive and specific during the initial clinical presentation. A vaccine to prevent epidemic typhus would constitute an effective deterrent to the weaponization of R. prowazekii; however, an effective and safe vaccine is not currently available. Due to the cytoplasmic niche of Rickettsia, CD8+ T-cells are critical effectors of immunity; however, the identification of antigens recognized by these cells has not been systematically addressed. To help close this gap, we designed an antigen discovery strategy that uses cell-based vaccination with antigen presenting cells expressing microbe's proteins targeted to the MHC class I presentation pathway. We report the use of this method to discover a protective T-cell rickettsial antigen, RP884, among a test subset of rickettsial proteins.

Recent Molecular Insights into Rickettsial Pathogenesis and Immunity

Human infections with arthropod-borne Rickettsia species remain a major global health issue, causing significant morbidity and mortality. Epidemic typhus due to Rickettsia prowazekii has an established reputation as the 'scourge of armies', and as a major determinant of significant 'historical turning points'. No suitable vaccines for human use are currently available to prevent rickettsial diseases. The unique lifestyle features of rickettsiae include obligate intracellular parasitism, intracytoplasmic niche within the host cell, predilection for infection of microvascular endothelium in mammalian hosts, association with arthropods and the tendency for genomic reduction. The fundamental research in the field of Rickettsiology has witnessed significant recent progress in the areas of pathogen adhesion/invasion and host immune responses, as well as the genomics, proteomics, metabolomics, phylogenetics, motility and molecular manipulation of important rickettsial pathogens. The focus of this review article is to capture a snapshot of the latest developments pertaining to the mechanisms of rickettsial pathogenesis and immunity.

Bringing Culture to the Uncultured: Coxiella burnetii and Lessons for Obligate Intracellular Bacterial Pathogens

Human diseases caused by obligate intracellular bacterial pathogens result in significant morbidity and mortality. Obligate intracellular bacteria that replicate in the cytoplasm of host endothelial cells include Rickettsia prowazekii, Rickettsia rickettsii, and Orientia tsutsugamushi (etiologic agents of epidemic typhus, Rocky Mountain spotted fever, and scrub typhus, respectively). Residing in specialized vacuolar compartments are Anaplasma phagocyophilum and Ehrlichia chaffensis (agents of febrile illnesses that have tropisms for neutrophils and monocytes, respectively) and Chlamydia trachomatis, which targets mucosal epithelia and causes blinding trachoma and sexually transmitted diseases. Coxiella burnetii preferentially colonizes mononuclear phagocytes during natural infection where it inhabits a specialized vacuole with properties of a phagolysosome [1]. The pathogen causes a debilitating influenza-like illness in humans called Q (query) fever, a disease that has received recent notoriety due to a large outbreak in the Netherlands [2]. The absolute reliance of obligates on a eucaryotic host cell for growth imposes significant experimental constraints, not the least of which is difficulty in establishing pathogen genetic systems. However, C. burnetii was recently liberated from its host cell by a medium that supports axenic (host cell–free) growth. Here, we provide a brief overview of the systematic approach used in C. burnetii media development and discuss how insight gained from this success could facilitate development of axenic media for other obligate intracellular bacterial pathogens.

Human Pediculosis : A Critical Health Problem and What about Nursing Policy ?

Lice infestation on the human body (also known as pediculosis) is very common. Cases number in the hundreds of millions worldwide. Three distinct presentations of lice infection exist and each is caused by a unique parasite. Head lice (Pediculus humanus capitis) is by far and away the most common infestation and favors no particular socioeconomic group. A genetically close "cousin," Pediculus humanus corporis, is responsible for body lice and is more commonly associated with poverty, overcrowding, and poor hygiene. Pubic lice (crabs) are caused by Pthirus pubis and is transmitted by intimate and/or sexual contact. No doubt, human lice infestation is an increasing problem worldwide, Apart from being an irritating and a shaming human ecto-parasite, they transmit serious infectious diseases; epidemic or classical typhus, epidemic relapsing fever as well as Trench fever. Eradication of lice infestation prevents transmission of infectious diseases. People who live and work in close proximity to louse-infested individuals may secondarily acquire lice even if they regularly wash their clothes and have good hygiene. Thus, all louse-infested persons and workers in close contact with such persons should periodically inspected and use long-acting safe insecticides. Human lice can be treated with agents such as DDT, malathion, and lindane, but reports of resistance to one or more of them have recently appeared. Pyrethroid permethrin when applied as a dust or spray to clothing or bedding is highly effective against lice and is the delousing agent of choice. Fabric treated with permethrin retains toxicity to lice even after 20 washings, thereby offering significant long-term passive protection against epidemic typhus. Itching may continue even after all lice are destroyed. This happens because of a lingering allergic reactionto their bites. Over-the-counter cortisone (corticosteroid) creams or calamine lotion may help.

Genome Sequencing of Four Strains of Rickettsia prowazekii, the Causative Agent of Epidemic Typhus, Including One Flying Squirrel Isolate

Rickettsia prowazekii is a notable intracellular pathogen, the agent of epidemic typhus, and a potential biothreat agent. We present here whole-genome sequence data for four strains of R. prowazekii, including one from a flying squirrel.

The activation of vivax malaria hypnozoites by infectious diseases

The periodicity of vivax malaria relapses may be explained by the activation of latent hypnozoites acquired from a previous malarial infection. The activation stimulus could be the febrile illness associated with acute malaria or a different febrile infection. We review historical records to examine the association between relapses of Plasmodium vivax and febrile infectious diseases. In data from British soldiers in Palestine, epidemic falciparum malaria triggered a smaller epidemic of P vivax relapses only in those who had been extensively exposed to malaria previously. Relapses did not follow pandemic influenza infection. Evidence from three simultaneous typhoid and malaria epidemics suggest that typhoid fever might activate P vivax hypnozoites. Some data lend support to the notion that vivax malaria relapse followed febrile illness caused by relapsing fever, trench fever, epidemic typhus, and Malta fever (brucellosis). These observations suggest that systemic parasitic and bacterial infections, but not viral infections, can activate P vivax hypnozoites. Specific components of the host's acute febrile inflammatory response, and not fever alone, are probably important factors in the provocation of a relapse of vivax malaria.

Palaeopathology and genes: Investigating the genetics of infectious diseases in excavated human skeletal remains and mummies from past populations

The aim of this paper is to review the use of genetics in palaeomicrobiology, and to highlight the importance of understanding past diseases. Palaeomicrobiology is the study of disease pathogens in skeletal and mummified remains from archaeological contexts. It has revolutionarised our understanding of health in the past by enabling a deeper knowledge of the origins and evolution of many diseases that have shaped us as a species. Bacterial diseases explored include tuberculosis, leprosy, bubonic plague, typhoid, syphilis, endemic and epidemic typhus, trench fever, and Helicobacter pylori. Viral diseases discussed include influenza, hepatitis B, human papilloma virus (HPV), human T-cell lymphotrophic virus (HTLV-1) and human immunodeficiency virus (HIV). Parasitic diseases investigated include malaria, leishmaniasis, Chagas' disease, roundworm, whipworm, pinworm, Chinese liver fluke, fleas and lice. Through a better understanding of disease origins and their evolution, we can place into context how many infectious diseases are changing over time, and so help us estimate how they may change in the future.

Dual Mechanisms of Metabolite Acquisition by the Obligate Intracytosolic Pathogen Rickettsia prowazekii Reveal Novel Aspects of Triose Phosphate Transport

Rickettsia prowazekii is an obligate intracytosolic pathogen and the causative agent of epidemic typhus fever in humans. As an evolutionary model of intracellular pathogenesis, rickettsiae are notorious for their use of transport systems that parasitize eukaryotic host cell biochemical pathways. Rickettsial transport systems for substrates found only in eukaryotic cell cytoplasm are uncommon among free-living microorganisms and often possess distinctive mechanisms. We previously reported that R. prowazekii acquires triose phosphates for phospholipid biosynthesis via the coordinated activities of a novel dihydroxyacetone phosphate transport system and an sn-glycerol-3-phosphate dehydrogenase (K. M. Frohlich et al., J. Bacteriol. 192:4281-4288, 2010). In the present study, we have determined that R. prowazekii utilizes a second, independent triose phosphate acquisition pathway whereby sn-glycerol-3-phosphate is directly transported and incorporated into phospholipids. Herein we describe the sn-glycerol-3-phosphate and dihydroxyacetone phosphate transport systems in isolated R. prowazekii with respect to kinetics, energy coupling, transport mechanisms, and substrate specificity. These data suggest the existence of multiple rickettsial triose phosphate transport systems. Furthermore, the R. prowazekii dihydroxyacetone phosphate transport systems displayed unexpected mechanistic properties compared to well-characterized triose phosphate transport systems from plant plastids. Questions regarding possible roles for dual-substrate acquisition pathways as metabolic virulence factors in the context of a pathogen undergoing reductive evolution are discussed.

Identification of novel arthropod vector G protein-coupled receptors.

BackgroundThe control of vector-borne diseases, such as malaria, dengue fever, and typhus fever is often achieved with the use of insecticides. Unfortunately, insecticide resistance is becoming common among different vector species. There are currently no chemical alternatives to these insecticides because new human-safe classes of molecules have yet to be brought to the vector-control market. The identification of novel targets offer opportunities for rational design of new chemistries to control vector populations. One target family, G protein-coupled receptors (GPCRs), has remained relatively under explored in terms of insecticide development.MethodsA novel classifier, Ensemble*, for vector GPCRs was developed. Ensemble* was validated and compared to existing classifiers using a set of all known GPCRs from Aedes aegypti, Anopheles gambiae, Apis Mellifera, Drosophila melanogaster, Homo sapiens, and Pediculus humanus. Predictions for unidentified sequences from Ae. aegypti, An. gambiae, and Pe. humanus were validated. Quantitative RT-PCR expression analysis was performed on previously-known and newly discovered Ae. aegypti GPCR genes.ResultsWe present a new analysis of GPCRs in the genomes of Ae, aegypti, a vector of dengue fever, An. gambiae, a primary vector of Plasmodium falciparum that causes malaria, and Pe. humanus, a vector of epidemic typhus fever, using a novel GPCR classifier, Ensemble*, designed for insect vector species. We identified 30 additional putative GPCRs, 19 of which we validated. Expression of the newly discovered Ae. aegypti GPCR genes was confirmed via quantitative RT-PCR.ConclusionA novel GPCR classifier for insect vectors, Ensemble*, was developed and GPCR predictions were validated. Ensemble* and the validation pipeline were applied to the genomes of three insect vectors (Ae. aegypti, An. gambiae, and Pe. humanus), resulting in the identification of 52 GPCRs not previously identified, of which 11 are predicted GPCRs, and 19 are predicted and confirmed GPCRs.

Is the Head Louse, Pediculus humanus capitis Vector of Human Diseases?

Head lice are hematophagous ectoparasitic insects, specific to humans and spending their entire life on their host. Humans are parasitized by two species of lice: The human louse, Pediculus humanus, which appears in two ecotypes, the head louse, Pediculus humanus capitis and the body louse, Pediculus humanus humanus. The second species is the pubic louse, Pthirus pubis. Infestation with lice can cause dermatitis and pruritus and sometimes secondary infections and lymphadenopathy. Since the early years of the 20 th century, it has been known that body lice are vectors of three pathogenic bacteria: a) Rickettsia prowazekii, the agent of epidemic typhus; b) Borrelia recurrentis, the agent of louseborne relapsing fever; and c) Bartonella quintana, the agent of trench fever. Lately, body lice were also shown to be vectors of Acinobacter baumannii, an aerobic Gram-negative bacterium, which is resistant to most antibiotics [1]. As opposed to body lice, the vectorial ability of head lice remains quite controversial. 39 head lice were fed on a rabbit that had been injected intravenously with a virulent strain of R. prowazekii [2]. Five days after infection, 16 of them were still alive and were allowed to feed on a human volunteer. Between days 5 and 9, 13 head lice were dead or moribund and all of them were positive by IF for R. prowazekii. The three surviving head lice were also positive. Head and body lice collected from homeless people in San Francisco, California (USA) were tested for B. quintana. It was found that 33.3% of body lice-infested persons and 25% of head lice-infested persons had lice infected with B. quintana strain Fuller [3]. B. quintana was found in 7% of head lice and in 18% of body lice isolated from naturally infested individuals in Ethiopia [4]. In head and body lice collected from 30 Nepalese children (including 11 cases of double infestation), B. quintana DNA sequences were detected in both head and body lice from two children as well as in body lice derived from two additional children [5]. In addition, the DNA of this pathogen was also detected in head louse eggs collected from a homeless man in Ethiopia [6]. Although head lice can be readily infected with R. prowazekii and B. quintana and later disseminate these virulent organisms in their feces, thus having the potential to be vectors of these pathogens under optimal epidemiologic conditions, e.g. during outbreaks of epidemic typhus, no reports can be found that in the absence of body lice, head lice could act as vectors under field conditions. In experimental work conducted with head and body lice, the humoral immune response of both lice, following bacterial challenge was examined and it was shown that both exhibited an increased immune response to Staphylococcus aureus but little to Escherichia coli. However, head lice exhibited a significantly higher phagocytotic activity against E. coli than body lice, suggesting that the reduced phagocytotic activity in body lice could be responsible, in part, for their increased vector competence [7]. It is concluded that head lice are poor biological vectors of human diseases and accordingly of little relevance from the epidemiologic point of view of these diseases.