Using epidemiological survey data to infer geographic distributions of leishmaniasis vector species

An important aspect of tropical medicine is analysis of geographic aspects of risk of disease transmission, which for lack of detailed public health data must often be reduced to an understanding of the distributions of critical species such as vectors and reservoirs. We examine the applicability of a new technique, ecological niche modeling, to the challenge of understanding distributions of such species based on municipalities in the state of São Paulo in which a group of 5 Lutzomyia sandfly species have been recorded. The technique, when tested based on independent occurrence data, yielded highly significant predictions of species' distributions; minimum sample sizes for effective predictions were around 40 municipalities.

Evaluation of diagnostic tests for Wuchereria bancrofti infection in Brazilian schoolchildren

Introduction Since the launch of the Global Programme to Eliminate Lymphatic Filariasis, more than 70% of the endemic countries have implemented mass drug administration (MDA) to interrupt disease transmission. The monitoring of filarial infection in sentinel populations, particularly schoolchildren, is recommended to assess the impact of MDA. A key issue is choosing the appropriate tools for these initial assessments (to define the best intervention) and for monitoring transmission. Methods This study compared the pre-MDA performance of five diagnostic methods, namely, thick film test, Knott's technique, filtration, Og4C3-ELISA, and the AD12-ICT card test, in schoolchildren from Brazil. Venous and capillary blood samples were collected between 11 pm and 1 am. The microfilarial loads were analyzed with a negative binomial regression, and the prevalence and associated 95% confidence intervals were estimated for all methods. The accuracies of the AD12-ICT card and Og4C3-ELISA tests were assessed against the combination of parasitological test results. Results A total of 805 schoolchildren were examined. The overall and stratified prevalence by age group and gender detected by Og4C3-ELISA and AD12-ICT were markedly higher than the prevalence estimated by the parasitological methods. The sensitivity of the AD12-ICT card and Og4C3-ELISA tests was approximately 100%, and the positive likelihood ratios were above 6. The specificity of the Og4C3-ELISA was higher than that of the AD12-ICT at different prevalence levels. Conclusions The ICT card test should be the recommended tool for monitoring school-age populations living in areas with ongoing or completed MDA.

The neotropical biting midges related to Culicoides paraensis (Diptera: Ceratopogonidae)

Culicoides paraensis (Goeldi), a common and widespread American bloodsucking midge that has been incriminated in the transmission of Mansonellosis and Oropouche Fever of humans in South America, is redescribed and figured. All published records are listed and new distribution is based on examination of extensive collections from throughout its range. Three closely related species of the subgenus Haematomyidium that have been confused with C. paraensis are briefly redescribed and figured, and a key is presented for their identification.

Epidemiology and control of malaria and other arthropod born diseases

Malaria and other arthropod born diseases remain a serious public health problem affecting the lives and health of certain social groups when the two basic strategies to control fail due to : (1) the lack of effective chemoprophylaxis/chemotherapy or the rapid development of drug resistance of the infectious agents and (2) the ineffectiveness of pesticides or the arthropod vectors develop resistance to them. These situations enhances the need for the design and implementation of other alternatives for sustainable health programmes. The application of the epidemiological methods is essential not only for analyzing the relevant data for the understanding of the biological characteristics of the infectious agents, their reservoirs and vectors and the methods for their control, but also for the assessment of the human behaviour, the environmental, social and economic factors involved in disease transmission and the capacity of the health systems to implement interventions for both changes in human behaviour and environmental management to purpose guaranteed prevention and control of malaria and other arthropod born diseases with efficiency, efficacy and equity. This paper discuss the evolution of the malaria arthropod diseases programmes in the American Region and the perspectives for their integration into health promotion programs and emphasis is made in the need to establish solid basis in the decision-making process for the selection of intervention strategies to remove the risk factors determining the probability to get sick or die from ABDs. The implications of the general planning and the polices to be adopted in an area should be analyzed in the light of programme feasibility at the local level, in the multisectoral context specific social groups and taking in consideration the principles of stratification and equity

Development of a vaccine strategy against human and bovine schistosomiasis: background and update

Schistosomiasis is a chronic and debilitating parasitic disease that affects over 200 million people throughout the world and causes about 500,000 deaths annually. Two specific characteristics of schistosome infection are of primordial importance to the development of a vaccine: schistosomes do not multiply within the tissues of their definitive hosts (unlike protozoan parasites) and a partial non-sterilizing immunity can have a marked effect on the incidence of pathology and on disease transmission. Since viable eggs are the cause of disease pathology, a reduction in worm fecundity whether or not accompanied by a reduction in parasite burden is a sufficient goal for vaccine induced immunity. We originally showed that IgE antibodies played in experimental models a pivotal role for the development of protective immunity. These laboratory findings have been now confirmed in human populations. Following the molecular cloning and expression of a protein 28 kDa protein of Schistosoma mansoni and its identification as a glutathion S-transferase, immunization experiments have been undertaken in several animal species (rats, mice, baboons). Together with a significant reduction in parasite burden, vaccination with Sm28 GST was recently shown to reduce significantly parasite fecundity and egg viability leading to a decrease in liver pathology. Whereas IgE antibodies were shown to be correlated with protection against infection, IgA antibodies have been identified as one of the factors affecting egg laying and viability. In human populations, a close association was found between IgA antibody production to Sm28 GST and the decrease of egg output. The use of appropriate monoclonal antibody probes has allowed the demonstration that the inhibition of parasite fecundity following immunization was related to the inhibition of enzymatic activity of the molecule. Epitope mapping of Sm28 GST has indicated the prominent role of the N and C terminal domains. Immunization with the corresponding synthetic peptides was followed by a decrease of 70% of parasite fecundity and egg viability. As a preliminary step towards phase I human trials, vaccination experiments have been performed in cattle, a natural model for Schistosoma bovis. Vaccination of calves with the S. bovis GST has led to a reduction of ever 80% of egg output and tissue egg count. Significant levels of protection were also observed in goats after immunization with the recombinant S. bovis GST. Increasing evidence of the participation of IgA antibodies in protective immunity has prompted us toward the development of mucosal immunization. Preliminary results indicate that significant levels of protection can be achieved following oral immunization with live attenuated vectors or liposomes. These studies seem to represent a promising approach towards the future development of a vaccine strategy against one of major human parasitic diseases.

Potential exposure to hepatitis C virus through accidental blood contact in interventional radiology.

PURPOSE: To quantify the prevalence of accidental blood exposure (ABE) among interventional radiologists and contrast that with the prevalence of patients with hepatitis C virus (HCV) undergoing interventional radiology procedures. MATERIALS AND METHODS: A multicenter epidemiologic study was conducted in radiology wards in France. The risk of ABE to radiologists was assessed based on personal interviews that determined the frequency and type of ABE and the use of standard protective barriers. Patients who underwent invasive procedures underwent prospective sampling for HCV serologic analysis. HCV viremia was measured in patients who tested positive for HCV. RESULTS: Of the 77 radiologists who participated in 11 interventional radiology wards, 44% reported at least one incident of mucous membrane blood exposure and 52% reported at least one percutaneous injury since the beginning of their occupational activity. Compliance with standard precautions was poor, especially for the use of protective clothes and safety material. Overall, 91 of 944 treated patients (9.7%) tested positive for HCV during the study period, of whom 90.1% had positive viremia results, demonstrating a high potential for contamination through blood contacts. CONCLUSIONS: The probability of HCV transmission from contact with contaminated blood after percutaneous injury ranged from 0.013 to 0.030; the high frequency of accidental blood exposure and high percentage of patients with HCV could generate a risk of exposure to HCV for radiologists who perform invasive procedures with frequent blood contact. The need to reinforce compliance with standard hygiene precautions is becoming crucial for medical and technical personnel working in these wards.

Microhabitat preferences of Biomphalaria pfeifferi and Lymnaea natalensis in a natural and a man-made habitat in Southeastern Tanzania

Schistosoma mansoni is an important human parasitic disease which is widespread throughout Africa. As Biomphalaria pfeifferi snails act as intermediate host, knowledge of their population ecology is an essential prerequisite towards understanding disease transmission. We conducted a field study and assessed the density and microhabitat preferences of B.pfeifferi in a natural habitat which was a residual pool of a river. Repeated removal collecting revealed a density of 26.6 [95% confidence interval (CI): 24.9-28.3] snails/m2. B.pfeifferi showed microhabitat preferences for shallow water (depths: 0-4cm). They were found most abundantly close to the shoreline (distances: 0-40cm), and preferred either plant detritus or bedrock as substratum. Lymnaea natalensis, a snail which may act as a host for human Fasciola gigantica, also occurred in this habitat with a density of 34.0 (95% CI: 24.7-43.3) snails/m2, and preferred significantly different microhabitats when compared to B.pfeifferi. Microhabitat selection by these snail species was also investigated in a man-made habitat nearby, which consisted of a flat layer of concrete fixed on the riverbed, covered by algae. Here, B.pfeifferi showed no preference for locations close to the shoreline, probably because the habitat had a uniform depth. We conclude that repeated removal collecting in shallow habitats provides reliable estimates of snail densities and that habitat changes through constructions may create favourable microhabitats and contribute to additional disease transmission.

Microsporidiosis of Tachinaephagus zealandicus Ashmead (Hymenoptera: Encyrtidae)

An undescribed microsporidium was found infecting Tachinaephagus zealandicus, a gregarious parasitoid that attacks third instar larvae of muscoid flies. Spores were present in all body regions and in all stages of development. Infected adults contained an average of 3.75 x 10(5) spores, and the pathogen was vertically transmitted to progeny. Infected female adults were fed either rifampicin or albendazole mixed with honey to determine the effectiveness of these drugs in preventing vertical transmission. After eight days of feeding on rifampicin the parasitoids produced progeny of which only 37% were infected. In contrast, albendazole-treated and untreated females produced progeny that were 97% and 100% infected, respectively. Healthy and infected colonies were established and studies were conducted to determine the mechanisms of transmission. It was observed that the efficiency of vertical (maternal) transmission was 96.3%. Uninfected parasitoid immatures also became infected when they shared superparasitized hosts with infected immatures. The method of transmission within superparasitized hosts is not known.

Re-infestation of houses by Triatoma dimidiata after intra-domicile insecticide application in the Yucatán peninsula, Mexico

In most countries, Chagas disease transmission control remains based on domestic insecticide application. We thus evaluated the efficacy of intra-domicile cyfluthrin spraying for the control of Triatoma dimidiata, the only Chagas disease vector in the Yucatán peninsula, Mexico, and monitored potential re-infestation every 15 days for up to 9 months. We found that there was a re-infestation of houses by adult bugs starting 4 months after insecticide application, possibly from sylvatic/peridomicile areas. This points out the need to take into account the potential dispersal of sylvatic/peridomestic adult bugs into the domiciles as well as continuity action for an effective vector control.

Genome-wide re-sequencing of multidrug-resistant Mycobacterium leprae Airaku-3.

Genotyping and molecular characterization of drug resistance mechanisms in Mycobacterium leprae enables disease transmission and drug resistance trends to be monitored. In the present study, we performed genome-wide analysis of Airaku-3, a multidrug-resistant strain with an unknown mechanism of resistance to rifampicin. We identified 12 unique non-synonymous single-nucleotide polymorphisms (SNPs) including two in the transporter-encoding ctpC and ctpI genes. In addition, two SNPs were found that improve the resolution of SNP-based genotyping, particularly for Venezuelan and South East Asian strains of M. leprae.

Cheap, rapid and efficient DNA extraction method to perform multilocus microsatellite genotyping on all Schistosoma mansoni stages

Schistosomes are endoparasites causing a serious human disease called schistosomiasis. The quantification of parasite genetic diversity is an essential component to understand the schistosomiasis epidemiology and disease transmission patterns. In this paper, we propose a novel assay for a rapid, low costly and efficient DNA extraction method of egg, larval and adult stages of Schistosoma mansoni. One euro makes possible to perform 60,000 DNA extraction reactions at top speed (only 15 min of incubation and 5 handling steps).

Granada Virus: a Natural Phlebovirus Reassortant of the Sandfly Fever Naples Serocomplex with Low Seroprevalence in Humans

A new member of the phlebovirus genus, tentatively named Granada virus, was detected in sandflies collected in Spain. By showing the presence of specific neutralizing antibodies in human serum collected in Granada, we show that Granada virus infects humans. The analysis of the complete genome of Granada virus revealed that this agent is likely to be a natural reassortant of the recently described Massilia virus (donor of the long and short segments) with ayet unidentified phlebovirus (donor of the medium segment)

Wild Triatoma infestans, a potential threat that needs to be monitored

The current persistence of Triatoma infestans, and therefore of Chagas disease transmission, in the Andean valleys of Bolivia and the Gran Chaco (precisely where wild populations of the vector are widespread), indicates a possible relationship between these two occurrences. This paper provides an overview of the current knowledge regarding wild T. infestans in Bolivia. The different morphs of the wild vector, their known distributions and some traits of their biology and ecology are presented. Particularly interesting is the considerable behavioural and chromatic plasticity that is displayed by wild T. infestans. According to the biogeographic region, different morphs of the vector occur in rupicolous habitats (common form and Mataral morph in Andean wild T. infestans) or arboreal ones ("dark morph" populations from the Chaco). The high genetic variability found at the microgeographical scale in Andean wild T. infestans favours the hypothesis that the Andes were the centre of origin and dispersal of T. infestans throughout South America. The relevant question regarding the origin of domestic populations is also addressed. Finally, current considerations of the epidemiological significance of wild T. infestans are discussed in the context of recent discoveries. Even if several observations support the epidemiological risk represented by wild T. infestans, the climatic and environmental conditions of their distribution areas would not favour the continued flow of triatomines between sylvatic refuges and domestic environments.

Toscana virus in Spain

Toscana virus (TOSV, Phlebovirus, family Bunyaviridae) infection is one of the most prevalent arboviruses in Spain. Within the objectives of a multidisciplinary network, a study on the epidemiology of TOSV was conducted in Granada, in southern Spain. The overall seroprevalence rate was 24.9%, significantly increasing with age. TOSV was detected in 3 of 103 sandfly pools by viral culture or reverse transcription-polymerase chain reaction from a region of the L gene. Nucleotide sequence homology was 99%-100% in TOSV from vectors and patients and 80%-81% compared to the Italian strain ISS Phl.3. Sequencing of the N gene of TOSV isolates from patients and vectors indicated 87%-88% and 100% homology at the nucleotide and amino acid levels, respectively, compared to the Italian strain. These findings demonstrate the circulation of at least 2 different lineages of TOSV in the Mediterranean basin, the Italian lineage and the Spanish lineage.