Showing papers in "Vector-borne and Zoonotic Diseases in 2010"

Sterile-Insect Methods for Control of Mosquito-Borne Diseases: An Analysis

Abstract: Effective vector control, and more specifically mosquito control, is a complex and difficult problem, as illustrated by the continuing prevalence (and spread) of mosquito-transmitted diseases. The sterile insect technique and similar methods control certain agricultural insect pest populations in a species-specific, environmentally sound, and effective manner; there is increased interest in applying this approach to vector control. Such an approach, like all others in use and development, is not a one-size-fits-all solution, and will be more appropriate in some situations than others. In addition, the proposed release of pest insects, and more so genetically modified pest insects, is bound to raise questions in the general public and the scientific community as to such a method's efficacy, safety, and sustainability. This article attempts to address these concerns and indicate where sterile-insect methods are likely to be useful for vector control.

Comparative role of Aedes albopictus and Aedes aegypti in the emergence of Dengue and Chikungunya in central Africa.

Abstract: Since its discovery in Nigeria in 1991, Aedes albopictus has invaded much of Central Africa, a region where Ae. aegypti also occurs. To assess the relationship between the invasion by Ae. albopictus and the recent emergence of dengue virus (DENV) and chikungunya virus (CHIKV), we undertook vector competence experiments on populations collected from Cameroon and conducted field investigations during concurrent epidemics of DENV and CHIKV in Gabon. Overall, infection and dissemination rates were not significantly different between Ae. albopictus and Ae. aegypti when exposed to titers of 10(8.1) mosquito infectious dose 50/mL and 10(7.5) plaque forming units/mL of DENV type 2 and CHIKV, respectively. Field investigations showed that Ae. albopictus readily bit man, was abundant, and outnumbered Ae. aegypti to a large extent in Gabon, particularly in suburban environments. Nevertheless, Ae. aegypti was predominant in the more urbanized central parts of Libreville. In this city, CHIKV and DENV were detected only in Ae. albopictus. These data strongly suggest that Ae. albopictus acted as the major vector of both viruses in Libreville in 2007, impacting on the epidemiology of DENV and CHIKV in this area.

Blood-Feeding Behavior of Aedes albopictus, a Vector of Chikungunya on La Réunion

Abstract: Chikungunya virus (CHIKV) has long been considered to be transmitted to humans by the human-biting mosquito Aedes aegypti, especially in Africa. However, the recent outbreak of CHIKV involved another vector, Aedes albopictus, and serological data in the literature suggest that several species of domestic or human-related vertebrates can be contaminated by this virus. However, the role of Ae. albopictus mosquitoes as potential enzootic vectors for CHIKV has not yet been evaluated. Here we investigate Ae. albopictus feeding and resting behaviors in an area where a CHIKV epidemic recently occurred, which means deciphering host-seeking and feeding behaviors on several vertebrate species, measuring endophagous/exophagous (activity), endophilic/exophilic (resting) behaviors and its diel (24 h, day/night) biting activity. Ae. albopictus was found to have bimodal daily feeding activities and was found to have exophagic (89%) and exophilic (87%) behaviors. Ae. albopictus showed an opportunistic feeding behavior on a wide range of hosts (from cold-blooded to warm-blooded animals), supporting that it can be implicated in various vertebrate-virus pathosystems. However, with equal availability of one of the four vertebrate hosts (calf, chicken, dog, and goat) proposed against human, Ae. albopictus significantly preferred human, supporting earlier data about its high degree of anthropophily. Multiple blood feeding was also reported in every combination (animal/human) offered to Ae. albopictus, enlightening the higher risks to spread an arbovirus to human population because of interrupted feeding. Such catholic behavior suggests that Ae. albopictus may act as a bridge vector for zoonotic viruses. Further epidemiological implications of this issue are discussed.

Larval Environmental Temperature and the Susceptibility of Aedes albopictus Skuse (Diptera: Culicidae) to Chikungunya Virus

Abstract: A key feature in the recent widespread epidemic of the mosquito-borne alphavirus chikungunya virus (CHIKV) was the important role of Aedes albopictus, formerly regarded as a secondary vector, compared to the presumed primary vector Aedes aegypti. Ae. albopictus, a container-inhabiting mosquito, is an invasive species that occurs over a wide geographic range spanning tropical and temperate latitudes. In this study we examine the effects of a broad range of larval rearing temperatures on CHIKV infection, dissemination, and viral titer in Florida F(1) Ae. albopictus. Adults from larvae reared at 18 degrees C, 24 degrees C, and 32 degrees C differed significantly in size, development time, and CHIKV infection rate. Adult females with the largest body size were produced from the coolest temperature, took the longest to mature, and six times more likely to be infected with CHIKV than females reared at 32 degrees C. There was also a significant effect of rearing temperature on viral dissemination, resulting in an increase in population dissemination at the coolest temperature. This study indicates that climate factors, such as temperature, experienced at the larval stage, can influence the competence of adult females to vector arboviruses.

A Longitudinal Study of the Prevalence of Nipah Virus in Pteropus lylei Bats in Thailand: Evidence for Seasonal Preference in Disease Transmission

Abstract: After 12 serial Nipah virus outbreaks in humans since 1998, it has been noted that all except the initial event in Malaysia occurred during the first 5 months of the year. Increasingly higher morbidity and mortality have been observed in subsequent outbreaks in India and Bangladesh. This may have been related to different virus strains and transmission capability from bat to human without the need for an amplifying host and direct human-to-human transmission. A survey of virus strains in Pteropus lylei and seasonal preference for spillover of these viruses was completed in seven provinces of Central Thailand between May 2005 and June 2007. Nipah virus RNA sequences, which belonged to those of the Malaysian and Bangladesh strains, were detected in the urine of these bats, with the Bangladesh strain being dominant. Highest recovery of Nipah virus RNA was observed in May. Of two provincial sites where monthly surveys were done, the Bangladesh strain was almost exclusively detected during April to Ju...

Enzootic plague reduces black-footed ferret (Mustela nigripes) survival in Montana.

Abstract: Black-footed ferrets (Mustela nigripes) require extensive prairie dog colonies (Cynomys spp.) to provide habitat and prey. Epizootic plague kills both prairie dogs and ferrets and is a major factor limiting recovery of the highly endangered ferret. In addition to epizootics, we hypothesized that enzootic plague, that is, presence of disease-causing Yersinia pestis without any noticeable prairie dog die off, may also affect ferret survival. We reduced risk of plague on portions of two ferret reintroduction areas by conducting flea control for 3 years. Beginning in 2004, about half of the ferrets residing on dusted and nondusted colonies were vaccinated against plague with an experimental vaccine (F1-V fusion protein). We evaluated 6-month reencounter rates (percentage of animals observed at the end of an interval that were known alive at the beginning of the interval), an index to survival, for ferrets in four treatment groups involving all combinations of vaccination and flea control. For captive-reared ferrets (115 individuals observed across 156 time intervals), reencounter rates were higher for vaccinates (0.44) than for nonvaccinates (0.23, p = 0.044) on colonies without flea control, but vaccination had no detectable effect on colonies with flea control (vaccinates = 0.41, nonvaccinates = 0.42, p = 0.754). Flea control resulted in higher reencounter rates for nonvaccinates (p = 0.026), but not for vaccinates (p = 0.508). The enhancement of survival due to vaccination or flea control supports the hypothesis that enzootic plague reduces ferret survival, even when there was no noticeable decline in prairie dog abundance. The collective effects of vaccination and flea control compel a conclusion that fleas are required for maintenance, and probably transmission, of plague at enzootic levels. Other studies have demonstrated similar effects of flea control on several species of prairie dogs and, when combined with this study, suggest that the effects of enzootic plague are widespread. Finally, we demonstrated that the experimental F1-V fusion protein vaccine provides protection to ferrets in the wild.

Host-feeding patterns of Aedes albopictus (Diptera: Culicidae) in urban and rural contexts within Rome province, Italy.

Abstract: Knowledge of the frequency of contact between a mosquito species and its different hosts is essential to understand the role of each vector species in the transmission of diseases to human...

Hantaviruses and their hosts in Europe: reservoirs here and there, but not everywhere?

Abstract: Five hantaviruses are known to circulate among rodents in Europe, and at least two among insectivores. Four (Dobrava, Saaremaa, Seoul, and Puumala [PUUV] viruses) are clearly associated with hemorrhagic fever with renal syndrome (HFRS). PUUV, the most common etiological agent of HFRS in Europe, is carried by the bank vole (Myodes glareolus), one of the most widespread and abundant mammal species in Europe. This host–virus system is among hantaviruses also the most studied one in Europe. However, HFRS incidence varies throughout the continent. The spatial as well as temporal variation in the occurrence of HFRS is linked to geographic differences in the population dynamics of the reservoir rodents in different biomes of Europe. While rodent abundance may follow mast seeding events in many parts of temperate Europe, in northern (N) Europe multiannual cycles in population density exist as the result of the interaction between rodent populations and specialist predator populations in a delayed density...

Effects of Temperature and Rainfall on the Activity and Dynamics of Host-Seeking Aedes albopictus Females in Northern Italy

Abstract: The Asian tiger mosquito, Aedes albopictus, has colonized nearly all the regions of Italy as well as other areas of Europe. During the summer of 2007 the tiger mosquito was responsible for an outbreak of Chikungunya in Italy, when this virus was brought in by a tourist of Indian origin returning from an endemic area. To increase the knowledge of tiger mosquito population dynamics, a survey was carried out from April to November 2008 in the municipalities of Arco and Riva del Garda (northern Italy) through a Biogents Sentinel™ (BG)-trap sampling. In particular, the aim of the study was to evaluate the influence of temperature and rainfall on the activity and dynamics of A. albopictus host-seeking females. The seasonal emergence of host-seeking females was strongly influenced by the minimum temperature, and a lower threshold of 13°C was identified. In addition, the threshold for the end of adult activity was found at a minimum temperature of 9°C. Host-seeking female abundance was positively affected by the accumulated temperatures over the period 3 and 4 weeks before the sampling week, possibly as a consequence of the positive effect of accumulated temperatures on larval density. Instead, accumulated precipitation over 1-4 weeks before sampling was negatively correlated with host-seeking female abundance. Finally, the activity of host-seeking females, estimated by the weekly increment in female abundance, was positively affected by the total abundance of females and by mean weekly temperatures. Our study provides useful information for predicting the dynamics of host-seeking Ae. albopictus females in northern Italy and for designing control strategies for preventing arbovirus outbreaks in areas colonized by Ae. albopictus.

Vector Control Improves Survival of Three Species of Prairie Dogs (Cynomys) in Areas Considered Enzootic for Plague

Abstract: Plague causes periodic epizootics that decimate populations of prairie dogs (PDs) (Cynomys), but the means by which the causative bacterium (Yersinia pestis) persists between epizootics are poorly understood. Plague epizootics in PDs might arise as the result of introductions of Y. pestis from sources outside PD colonies. However, it remains possible that plague persists in PDs during interepizootic periods and is transmitted at low rates among highly susceptible individuals within and between their colonies. If this is true, application of vector control to reduce flea numbers might reduce mortality among PDs. To test whether vector control enhances PD survival in the absence of obvious plague epizootics, we reduced the numbers of fleas (vectors for Y. pestis) 96-98% (1 month posttreatment) on 15 areas involving three species of PDs (Cynomys leucurus, Cynomys parvidens in Utah, and Cynomys ludovicianus in Montana) during 2000-2004 using deltamethrin dust delivered into burrows as a pulicide. Even during years without epizootic plague, PD survival rates at dusted sites were 31-45% higher for adults and 2-34% higher for juveniles compared to survival rates at nondusted sites. Y. pestis was cultured from 49 of the 851 flea pools tested (6882 total fleas) and antibodies against Y. pestis were identified in serum samples from 40 of 2631 PDs. Although other explanations are possible, including transmission of other potentially fatal pathogens by fleas, ticks, or other ectoparasites, our results suggest that plague might be maintained indefinitely in PD populations in the absence of free epizootics and widespread mortality among these animals. If PDs and their fleas support enzootic cycles of plague transmission, there would be important implications for the conservation of these animals and other species.

Assessment of polymicrobial infections in ticks in New York state.

Abstract: Ixodes scapularis ticks are clinically important hematophagous vectors. A single tick bite can lead to a polymicrobial infection. We determined the prevalence of polymicrobial infection with Borrelia burgdorferi, Anaplasma phagocytophilum, Babesia microti, Borrelia miyamotoi, and Powassan virus in 286 adult ticks from the two counties in New York State where Lyme disease is endemic, utilizing a MassTag multiplex polymerase chain reaction assay. Seventy-one percent of the ticks harbored at least one organism; 30% had a polymicrobial infection. Infections with three microbes were detected in 5% of the ticks. One tick was infected with four organisms. Our results show that coinfection is a frequent occurrence in ticks in the two counties surveyed.

Seroprevalence of Trypanosoma cruzi Among Eleven Potential Reservoir Species from Six States Across the Southern United States

Abstract: Trypanosoma cruzi, the causative agent of Chagas' disease, is a substantial public health concern in Latin America. Although rare in humans and domestic animals in the United States, T. cruzi is commonly detected in some wildlife species, most commonly raccoons (Procyon lotor) and Virginia opossums (Didelphis virginiana). To increase our understanding of the reservoir host species range and geographic distribution, 11 species of mammals from six states spanning the known range of T. cruzi (Arizona, California, Florida, Georgia, Missouri, and Virginia) were tested for antibodies to T. cruzi using indirect immunofluorescent antibody testing. In addition, culture isolation attempts were conducted on a limited number of animals from Georgia and Florida. Evidence of T. cruzi was found in every state except California; however, low numbers of known reservoirs were tested in California. In general, the highest seroprevalence rates were found in raccoons (0-68%) and opossums (17-52%), but antibodies to T. cruzi were also detected in small numbers of striped skunks (Mephitis mephitis) from Arizona and Georgia, bobcats (Lynx rufus) from Georgia, two coyotes (Canis latrans) from Georgia and Virginia, and a ringtail (Bassariscus astutus) from Arizona. Culture-based prevalence rates for raccoons were significantly greater than those for opossums; however, seroprevalences of raccoons and opossums from several geographic locations in Georgia and Florida were not different, indicating that exposure rates of these two species are similar within these areas. For both raccoons and opossums, seroprevalence was significantly higher in females than in males. No difference was detected in seroprevalence between adults and juveniles and between animals caught in urban and rural locations. Our results indicate that T. cruzi prevalence varies by host species, host characteristics, and geographic region and provides data to guide future studies on the natural history of T. cruzi in the United States.

Molecular Detection of Rickettsia amblyommii in Amblyomma americanum Parasitizing Humans

Abstract: A quantitative real-time polymerase chain reaction assay to detect and quantify a portion of the outer membrane protein B gene (ompB) of Rickettsia amblyommii was employed to assess the threat of R. amblyommii exposure to humans parasitized by Amblyomma americanum (the lone star tick). A total of 72 pools of lone star ticks removed from humans were acquired from two collections and used in this study: 44 pools of A. americanum submitted to the Department of Defense Human Tick Test Kit Program in 2003 collected from 220 individuals from 14 states, and 28 pools of A. americanum representing 120 ticks obtained from boy scouts and adult leaders at the Boy Scouts of America National Jamboree held at Fort A.P. Hill, Virginia, in 2005. Of the 72 lone star tick pools representing 340 lone star ticks, 58 pools (80.5%) were positive for R. amblyommii. In addition, individual A. americanum ticks parasitizing humans collected as part of the Department of Defense Human Tick Test Kit Program in 2002 and 2003 from 17 states were evaluated. It was found that 244 of 367 (66.5%) individual A. americanum ticks tested positive for the presence of R. amblyommii DNA. These results clearly show that lone star ticks parasitizing humans are highly infected with R. amblyommii, which may potentiate rickettsial infection of and possibly disease in humans.

Circulation of group 2 coronaviruses in a bat species common to urban areas in Western Europe.

Abstract: Fecal samples of 211 bats representing 13 different bat species from 31 locations in the Netherlands were analyzed for the presence of coronaviruses (CoV) using a genus-wide reverse transcription (RT)-polymerase chain reaction. CoVs are known for their high potential for interspecies transmission, including zoonotic transmission with bats as reservoir hosts. For the first time, a group 2 CoV was found in a bat, Pipistrellus pipistrellus, in Europe. This is of particular interest for public health as the reservoir host is a species that is common to urban areas in most of Europe and notorious for its close interactions with humans. Four verspertilionid bat species were found to excrete group 1 CoVs, viz. Myotis daubentonii, M. dasycneme, P. pipistrellus, and Nyctalus noctula. The last species is a newly identified reservoir. The overall prevalence was 16.9% and positive bats were found at multiple widespread locations. The circulating group 1 CoV lineages were rather species associated than location associated.

West Nile virus lineage 2 as a cause of zoonotic neurological disease in humans and horses in southern Africa.

Abstract: West Nile virus (WNV) is widely distributed in South Africa, but since a few cases of neurological disease have been reported from this region, endemic lineage 2 strains were postulated to be of low virulence Several cases of nonfatal encephalitis in humans as well as fatal cases in a foal, dog, and ostrich chicks have, however, been associated with lineage 2 WNV in South Africa The pathogenesis of lineage 2 WNV strains was investigated using mouse neuroinvasive experiments, gene expression experiments, and genome sequence comparisons which indicated that lineage 2 strains that are highly pathogenic exist To determine whether cases of WNV were being missed in South Africa, horses with fever and neurological disease were investigated Several cases of WNV were identified, all associated with severe neurological disease, 85% of which had to be euthanized or died All cases positive by RT-PCR were shown to belong to lineage 2 WNV by DNA sequencing and phylogenetic analysis Two cases of occupational infection were investigated, including a case of zoonotic transmission to a veterinarian who performed an autopsy on one of the horses as well as a laboratory infection after a needle stick injury with a neuroinvasive lineage 2 strain Both resulted in neurological disease Cytokine expression was investigated in the second case to assess the immunopathogenesis of WNV Collectively, these studies suggest that lineage 2 WNV may be significantly under estimated as a cause of neurological disease in South Africa

Vector competence of Australian mosquitoes for chikungunya virus.

Abstract: Chikungunya virus (CHIKV) is a globally emerging arbovirus responsible for unprecedented outbreaks in the western Indian Ocean, the Indian subcontinent and Italy. To assess the receptivity of Australia to CHIKV, we exposed 10 Australian mosquito species to a 2006 strain of CHIKV isolated from a viremic traveler from Mauritius. In susceptibility trials, the infectious dose required to infect 50% of the mosquitoes was 10(0.6) cell culture infectious dose (CCID)(50)/mosquito for Aedes procax, 10(1.7) CCID(50)/mosquito for Aedes albopictus, 10(2.1) CCID(50)/mosquito for Aedes vigilax, and 10(2.6) CCID(50)/mosquito for Aedes aegypti and Aedes notoscriptus. When exposed to blood meals containing between 10(3.5) and 10(4.1) CCID(50)/mosquito of CHIKV, infection rates in these five species, plus Coquillettidia linealis, were >or=81%. Subsequent transmission rates ranged between 20% for Ae. notoscriptus and 76% for Ae. vigilax. In contrast, Culex spp. were poor laboratory vectors, with infection and dissemination rates

Integration of a Tick-Borne Encephalitis Virus and Borrelia burgdorferi sensu lato into Mountain Ecosystems, Following a Shift in the Altitudinal Limit of Distribution of Their Vector, Ixodes ricinus (Krkonoše Mountains, Czech Republic)

Abstract: The altitudinal shift in the limit of Ixodes ricinus occurrence above the previously established altitude of 750 m above sea level has been monitored over the long-term (2002–2008) in the ...

Evaluation of Nonstructural 1 Antigen Assays for the Diagnosis and Surveillance of Dengue in Singapore

Abstract: Early and accurate diagnosis of dengue is imperative for disease surveillance, which helps in the control of dengue in endemic countries. In this study, we evaluated the performance of three commercially available dengue nonstructural 1 (NS1) antigen assays (Bio-Rad Platelia™ Dengue NS1 Antigen ELISA, PanBio Dengue Early ELISA, and Bio-Rad Dengue NS1 Antigen Strip test) and compared them with reverse-transcription polymerase chain reaction (RT-PCR) and other commercially available serological assays for the diagnosis of dengue. The analysis showed RT-PCR to be the most sensitive and specific (100%) diagnostic method during the first 3 days of fever. The overall sensitivity of dengue NS1 antigen assays within the same period was 81.7%, indicating their potential role as a cost-effective and convenient alternative method to RT-PCR for the diagnosis of dengue fever in a primary healthcare setting. However, reduced sensitivity in detecting secondary dengue infections was one of the drawbacks of dengue NS1 antigen assays. Nonetheless, it remains a useful assay for the early detection of dengue and hence could play an important role in routine surveillance efforts to control dengue outbreaks in Singapore.

Prevalence of five pathogenic agents in questing Ixodes ricinus ticks from western France.

Abstract: In Europe, Ixodes ricinus ticks are vectors of many emerging pathogens, including Borrelia burgdorferi sensu lato (sl), Anaplasma phagocytophilum, spotted fever group Rickettsia sp., Babesia sp., and very likely Bartonella sp. In this study, we looked for the presence of DNA of these microorganisms in 572 ticks from two forests in the west of France. DNA extraction and polymerase chain reaction (PCR) amplification were performed on individual nymphal, male, and female I. ricinus ticks. Amplification from 1 tick among the 572 samples (0.2%) resulted in PCR products with Bartonella-specific primers. Sequence analysis of the amplified fragment did not lead to species identification. Two ticks (0.3%) carried A. phagocytophilum–specific DNA. Eight ticks (1.4%) were positive with spotted fever group Rickettsia–specific primers, and all PCR fragments were related to Rickettsia helvetica. Thirty-five ticks (6.1%) were positive with B. burgdorferi sl–specific primers; the sequences were all related to Bor...

Arboviral Survey of Mosquitoes in Two Northern Italian Regions in 2007 and 2008

Abstract: Recently, Italy-particularly the Emilia-Romagna region-was the location of consecutive outbreaks of human diseases caused by the arboviruses chikungunya virus and West Nile virus The two outbreaks, spread by different species of mosquitoes, were not related, but pointed out the lack of an arboviral surveillance program in this region Beginning in 2007 entomological surveillance was initiated in the Emilia-Romagna region, and in 2008 the program was improved and extended at Lombardia region Using CO(2)-baited traps, 65,292 mosquitoes were collected; pooled by date of collection, location, and species; macerated manually; and tested by reverse transcription (RT)-polymerase chain reaction for the presence of alphaviruses, orthobunyaviruses, and flaviviruses Amplicons were sequenced and employed for identification of viral RNA by basic local alignment search tool search in GenBank Results of these assays showed (1) the presence of West Nile virus in two pools of Culex pipiens mosquitoes, (2) the presence of RNA of two orthobunyaviruses, Tahyna virus in a pool of Ochlerotatus caspius mosquitoes and Batai virus in a pool of Anopheles maculipennis mosquitoes, and (3) the presence of flavivirus RNAs in pools of Oc caspius, Aedes albopictus, and Aedes vexans mosquitoes; the sequences of these amplicons were most closely related to flaviviruses that have been detected only in mosquitoes and had no recognized vertebrate host (Aedes flavivirus, Culex flavivirus, and Kamiti River virus)

Phylogeographic structure and evolutionary history of Sindbis virus

Abstract: Sindbis (SIN) virus, Alphavirus, is a mosquito-borne and bird-associated virus with large geographic distribution in the Old World. We investigated the genetic diversity of 59 SIN strains after limited sequencing of their E2 glycoprotein genes. The SIN strains showed maximal diversity of 22.2% at the amino acid (aa) level, and formed five tentative genotypes. The SIN-I genotype included strains from Europe and Africa. Strains from Australia and East Asia formed SIN-II and SIN-III with about 12% and 15% aa divergence from SIN-I. The only isolate from New Zealand was distinct, and constitutes the SIN-V genotype. Isolates from Azerbaijan and China formed genotype SIN-IV with 15.6%-19.1% aa divergence from SIN-I to III and SIN-V. Phylogenetic analyses indicated that Aura virus was present before the recombinant alphavirus lineage arose. This is consistent with a South American origin of the SIN complex, and argue for a spread in North America before reaching Asia and Australia, followed by westward radiation into Africa and Europe. High levels of sequence identities were observed for geographic regions belonging to the same north-south axis, whereas the east-west genetic exchange appears to be limited. The observed phylogeographic structure was confirmed by distinct aa patterns within two-thirds of the structural protein-coding region of SIN virus strains from Saudi Arabia, Asia, and Australia. The present geography of the five SIN genotypes and subclusters within SIN-I correlate with major bird migration patterns.

Bacterial Pathogens in Ixodid Ticks from a Piedmont County in North Carolina: Prevalence of Rickettsial Organisms

Abstract: In North Carolina, reported human cases of tick-borne illness, specifically Rocky Mountain spotted fever, have escalated over the past decade. To determine the relative abundance of vectors and to estimate the risk of acquiring a tick-borne illness in peri-residential landscapes, ticks were collected in Chatham County, a typical Piedmont county and, samples of the ticks were tested for infection with selected bacterial pathogens using real-time quantitative polymerase chain reaction assays. Ticks (n = 3746) were collected by flagging vegetation at 26 sites from April to July 2006. The predominant questing tick was Amblyomma americanum (98.5%) with significantly fewer Dermacentor variabilis (1.0%) and Ixodes scapularis (0.5%) collected. Spotted fever group (SFG) rickettsiae were detected in 68.2% of 1590 A. americanum with 56.4% of the molecular isolates identified as Rickettsia amblyommii, an informally named member of the SFG rickettsiae. Comparatively, smaller numbers of A. americanum contained...

Geographical distribution and surveillance of Crimean-Congo hemorrhagic fever in Iran.

Abstract: Crimean-Congo hemorrhagic fever (CCHF) is viral hemorrhagic fever caused by CCHF virus, which belongs to the family Bunyaviridae and the genus Nairovirus. The virus is transmitted to humans via contact with blood and tissue from infected livestock, a tick bite, or contact with an infected person. Since 2000, we have shown the disease to be prevalent in 23 out of 30 provinces of Iran. Among those, Sistan-va-Baluchistan, Isfahan, Fars, Tehran, Khorasan, and Khuzestan demonstrated the highest infection, respectively. Notably, Sistan-va-Baluchistan province, southeast of Iran, has the highest prevalence of CCHF, and has shown to be present since at least 2000. Phylogenetic study of the CCHF virus genome isolated from Iranian patients showed a close relationship with the CCHF Matin strain (Pakistan). Our epidemiological data in the last decade have implied that the severity and fatality rate of the disease has ranged variably in different provinces of Iran. More pathogenesis and phylogenetic studies s...

Landscape predictors of tick-borne encephalitis in Latvia: land cover, land use, and land ownership.

Abstract: Although the presence of tick-borne encephalitis (TBE) virus circulating in tick populations depends on large-scale patterns of climate, and the local density of infected ticks depends on the abundance of mammalian hosts, the risk of human infection depends on the access and use by human populations of tick-infested habitats, particularly forests, at the landscape level. We investigated the incidence of reported TBE cases in rural parishes (i.e., municipalities) in Latvia. The following major characteristics of parishes were considered: whether their environment is suitable for tick and tick-host populations (depending on land cover); whether the local human population is likely to enter the forest on a regular base (depending on land use); and whether the spatial distributions of these two aspects are likely to intersect, through access rules (as a function of land ownership). The results indicated that all three aspects are important in explaining and predicting the spatial distribution of TBE cases in the rural areas of Latvia. The concept of landscape is here given new depth by consideration of its physical structure, its use by human populations, and its accessibility as modulated by ownership.

First report of natural infection in cats with Leishmania infantum in Iran.

Abstract: Visceral leishmaniasis (VL), caused by Leishmania infantum, is an endemic zoonosis in Iran In recent years, Leishmania infection in cats has been reported in several countries where leishmaniasis is present The aim of this study was to survey Leishmania infection in cats and to detect its causative agents in VL endemic areas in Iran Forty stray cats were captured from two areas where VL is endemic, Fars and East Azerbaijan provinces Infection with Leishmania was evaluated by parasitological and molecular methods Leishmania parasites were detected in 4 out of 40 cats (10%) The parasite was isolated from the spleen of three and the liver of one cat and mass cultivated in the culture medium Molecular and isoenzyme characterization revealed that the parasites isolated from the four cats were all L infantum Considering the high rate of feline Leishmania infection in this study, it may be suggested that cats have an epidemiological role in areas where VL is endemic in Iran

Assessment of a novel real-time pan-flavivirus RT-polymerase chain reaction.

Abstract: Outbreaks of West Nile virus (WNV) have occurred intermittently in regions around the Mediterranean coast, and the virus may have become established in Northern Italy and Romania, with rep...

Ecology of hantaviruses and their hosts in North America.

Abstract: Since the 1993 discovery of a highly pathogenic hantavirus associated with the North American deer mouse (Peromyscus maniculatus), intensive ecological studies have led to many advances in our understanding of the natural history of New World hantaviruses as it relates to human disease. Seventeen named hantaviruses have been identified in North America. Field and laboratory studies of Sin Nombre and other hantaviruses have delineated host associations, geographical distributions, mechanisms of transmission, temporal infection dynamics of these viruses in host populations, and environmental factors that influence these dynamics. Using data from these studies, preliminary predictive models of the risk of hantavirus infection to humans have been developed. Improved models using satellite-derived data are under development. Multidisciplinary collaboration, integration of field and laboratory studies, and establishment and maintenance of long-term monitoring studies will be critical to continued advan...

Experimental infection of young adult European breed sheep with Rift Valley fever virus field isolates.

Abstract: The increasing interest in Rift Valley fever virus (RVFV) and its potential impact on naive animal populations deserve revisiting experimental reproduction of RVFV infection, particularly in those animal breeds for which no data about their susceptibility to RVFV infection have ever been recorded. In this study we show the susceptibility of 9–10 weeks old European sheep (Ripollesa breed) to RVFV infection, showing a mild, subacute form of disease. Four different viral isolates efficiently replicated in vivo after subcutaneous experimental inoculation, and consistent viral loads in blood and virus shedding (variable in length depending on the RVFV isolate used) were detected, showing horizontal transmission to a noninfected, sentinel lamb. RVFV infection caused transient pyrexia in adult lambs and no other clinical symptoms were observed, with the exception of corneal opacity (“blue eye”) found in 3 out of 16 subcutaneously inoculated sheep. In conclusion, adult sheep from this European breed are ...

Serological Prevalence of Hepatitis E Virus in Domestic Animals and Diversity of Genotype 4 Hepatitis E Virus in China

Abstract: Pigs have been confirmed to be reservoirs of some genotypes of hepatitis E virus (HEV), and other nonhuman species are also likely infected with the virus. To assess the prevalence of HEV infection in domestic animals in China, 3579 serum samples, including 1967 swine, 700 goat, and 912 cattle sera, were collected from 26 provinces across the country and tested for HEV antibodies and antigen using enzyme immunoassays. The results showed that 82.2% of the swine samples, but only 10.4% and 28.2% of cattle and goat sera, were anti-HEV positive respectively. The prevalence of anti-HEV antibody in animals varied from province to province, ranging from 10.9% to 100% in pigs, 0% to 48% in goats, and 0% to 92.9% in cattle. About 1.9% of pigs, 1.6% of goats, and 0.8% of cattle tested in the study were positive for HEV antigen. Some samples, including all HEV antigen-positive samples, were tested for HEV-specific RNA using reverse transcription polymerase chain reaction. Fifteen swine samples, but none from the goats or cattle, were found to be HEV RNA positive. Sequence and phylogenetic analyses classified all the swine HEV isolates into HEV genotype 4, which was further divided into four subgroups. This study demonstrated that HEV infection is widespread in domestic animals, particularly pigs, in China. The HEV genotype infecting pigs in China was genotype 4. However, the isolates displayed considerable genetic diversity.

Detection of Flaviviruses and Orthobunyaviruses in Mosquitoes in the Yucatan Peninsula of Mexico in 2008

Abstract: A total of 191,244 mosquitoes from 24 species were collected in the Yucatan Peninsula of Mexico from January to December 2008, and tested for the presence of cytopathic virus by virus isolation in Vero cells. Eighteen virus isolates were obtained, all of which were orthobunyaviruses. These were identified by reverse transcription-polymerase chain reaction (RT-PCR) and nucleotide sequencing as Cache Valley virus (n=17) and South River virus (n=1). A subset (n=20,124) of Culex quinquefasciatus collected throughout the year was further tested by RT-PCR using flavivirus-specific primers. Flavivirus RNA was present in this mosquito species year-round. The overall flavivirus minimal infection rate, expressed as the number of positive mosquito pools per 1000 mosquitoes tested, was 7.7 and the monthly flavivirus minimal infection rates ranged from 4.3 to 16.6. Approximately one-third of the RT-PCR products were sequenced and all corresponded to Culex flavivirus, a recently discovered insect-specific flavivirus.