Comparison of the Kato-Katz and Helmintex methods for the diagnosis of schistosomiasis in a low-intensity transmission focus in Bandeirantes, Paraná, southern Brazil

The diagnosis of schistosomiasis is problematic in low-intensity transmission areas because parasitological methods lack sensitivity and molecular methods are neither widely available nor extensively validated. Helmintex is a method for isolating eggs from large faecal samples. We report preliminary results of a comparative evaluation of the Helmintex and Kato-Katz (KK) methods for the diagnosis of schistosomiasis in a low-intensity transmission area in Bandeirantes, Paraná, southern Brazil. Eggs were detected by both methods in seven patients, whereas only Helmintex yielded positive results in four individuals. The results confirm the previously demonstrated higher sensitivity of the Helmintex method compared with the KK method.

Vector control intervention towards interruption of transmission of Chagas disease by Rhodnius prolixus, main vector in Guatemala

In Guatemala, the Ministry of Health (MoH) began a vector control project with Japanese cooperation in 2000 to reduce the risk of Chagas disease infection. Rhodnius prolixus is one of the principal vectors and is targeted for elimination. The control method consisted of extensive residual insecticide spraying campaigns, followed by community-based surveillance with selective respraying. Interventions in nine endemic departments identified 317 villages with R. prolixus of 4,417 villages surveyed. Two cycles of residual insecticide spraying covered over 98% of the houses in the identified villages. Fourteen villages reinfestated were all resprayed. Between 2000-2003 and 2008, the number of infested villages decreased from 317 to two and the house infestation rate reduced from 0.86% to 0.0036%. Seroprevalence rates in 2004-2005, when compared with an earlier study in 1998, showed a significant decline from 5.3% to 1.3% among schoolchildren in endemic areas. The total operational cost was US$ 921,815, where the cost ratio between preparatory, attack and surveillance phases was approximately 2:12:1. In 2008, Guatemala was certified for interruption of Chagas disease transmission by R. prolixus. What facilitated the process was existing knowledge in vector control and notable commitment by the MoH, as well as political, managerial and technical support by external stakeholders.

Leprosy frequency in the world, 1999-2010

In 1991, the World Health Organization (WHO) committed to reducing the prevalence of leprosy to below 1 in 10,000 inhabitants by 2000. Significant improvements in leprosy control have occurred, but leprosy remains a public health problem in many countries due to its high incidence and rate of transmission. This paper reviews data published by the WHO in the years 2000, 2005 and 2010. These data sets included 148 countries or territories that reported to the WHO at least once. Only four countries reported higher prevalence rates in 2010 than in 2000 and eight reported higher case detection rate (CDR) in 2009 than in 1999. Prevalence rate reductions were greater for the first five-year period examined, while CDR reductions were greater in the second five-year period. Thirty-six countries and territories reported at least one prevalence value higher than 1 per 10,000 inhabitants and 32 reported at least one CDR value higher than 9 per 100,000 inhabitants. A total of 39 countries fit at least one of these criteria and all were located in tropical regions.

Historic aspects of human susceptibility to leprosy and the risk of conjugal transmission

Estimates of genetic susceptibility to leprosy were made in the past from observational reports in familial settings using descriptive epidemiologic data. Risk of conjugal transmission of leprosy (from one spouse to another) has been estimated between 1-10% and is thought to occur in 3-5% of spouses exposed to untreated lepromatous disease in the partner. Risk of secondary transmission is presumed higher in other family members than for the conjugal partner. This belief has become dogma to many leprologists who may no longer know the basis for this estimation. This article reviews the historic epidemiologic descriptions of risk for leprosy transmission in married couples compared to other family members. Although uncommon, conjugal leprosy occurs and at higher rates in populations with traditional familial intermarriage and consanguinity.

Unveiling healthy carriers and subclinical infections among household contacts of leprosy patients who play potential roles in the disease chain of transmission

Leprosy transmission still occurs despite the availability of highly effective treatment. The next step towards successfully eliminating leprosy is interrupting the chain of transmission of the aetiological agent, Mycobacterium leprae. In this investigation, we provide evidence that household contacts (HHCs) of leprosy patients might not only have subclinical infections, but may also be actively involved in bacilli transmission. We studied 444 patients and 1,352 contacts using anti-phenolic glycolipid-I (PGL-I) serology and quantitative polymerase chain reaction (qPCR) to test for M. leprae DNA in nasal swabs. We classified the patients according to the clinical form of their disease and the contacts according to the characteristics of their index case. Overall, 63.3% and 34.2% of patients tested positive by ELISA and PCR, respectively. For HHCs, 13.3% had a positive ELISA test result and 4.7% had a positive PCR test result. The presence of circulating anti-PGL-I among healthy contacts (with or without a positive PCR test result from nasal swabs) was considered to indicate a subclinical infection. DNA detected in nasal swabs also indicates the presence of bacilli at the site of transmission and bacterial entrance. We suggest that the concomitant use of both assays may allow us to detect subclinical infection in HHCs and to identify possible bacilli carriers who may transmit and disseminate disease in endemic regions. Chemoprophylaxis of these contacts is suggested.

Risk for Pneumocystis carinii transmission among patients with pneumonia: a molecular epidemiology study.

We report a molecular typing and epidemiologic analysis of Pneumocystis carinii pneumonia (PCP) cases diagnosed in our geographic area from 1990 to 2000. Our analysis suggests that transmission from patients with active PCP to susceptible persons caused only a few, if any, PCP cases in our setting.

Certifying the interruption of Chagas disease transmission by native vectors: cui bono?

Certifying the absence of Chagas disease transmission by native vectors lacks scientific grounds and weakens long-term control-surveillance systems to the detriment of people living under risk conditions. Instead, a regular "certification of good practice" (including vector control-surveillance, case detection/patient care and blood safety) could help achieve sustained disease control.

Influenza A virus infection of healthy piglets in an abattoir in Brazil: animal-human interface and risk for interspecies transmission

Asymptomatic influenza virus infections in pigs are frequent and the lack of measures for controlling viral spread facilitates the circulation of different virus strains between pigs. The goal of this study was to demonstrate the circulation of influenza A virus strains among asymptomatic piglets in an abattoir in Brazil and discuss the potential public health impacts. Tracheal samples (n = 330) were collected from asymptomatic animals by a veterinarian that also performed visual lung tissue examinations. No slaughtered animals presented with any noticeable macroscopic signs of influenza infection following examination of lung tissues. Samples were then analysed by reverse transcription-polymerase chain reaction that resulted in the identification of 30 (9%) influenza A positive samples. The presence of asymptomatic pig infections suggested that these animals could facilitate virus dissemination and act as a source of infection for the herd, thereby enabling the emergence of influenza outbreaks associated with significant economic losses. Furthermore, the continuous exposure of the farm and abattoir workers to the virus increases the risk for interspecies transmission. Monitoring measures of swine influenza virus infections and vaccination and monitoring of employees for influenza infection should also be considered. In addition regulatory agencies should consider the public health ramifications regarding the potential zoonotic viral transmission between humans and pigs.

Etude du respect des mesures de prévention de la transmission verticale du virus de l'hépatite B chez les enfants nés dans les maternités des hôpitaux publics du canton de Vaud

Actuellement, en Suisse, environ 1% des femmes en âge de procréer ont une hépatite B chronique(8). En l'absence de mesures de prévention, le risque de transmission du virus de l'hépatite B, de la mère à son enfant, est estimé à 40%(3,4,5) lors de l'accouchement. Ce risque s'étend bien au-delà de la période péri¬natale. Les enfants infectés dans ces circonstances ont une probabilité de 90% de développer une infection chronique(5,7) et un quart meurent prématurément de cirrhose ou d'hépatocarcinome(2). L'Office fédéral de la santé publique recommande d'effectuer un dépistage anténatal de l'antigène HBsAg lors de toute grossesse(1) et d'effectuer une vaccination passive et active chez tous les enfants naissant d'une mère avec une hépatite B chronique. Cette prophylaxie doit être effectuée comme suit : immunoglobuline spécifique et lere dose de vaccin dans les 12 heures suivant la naissance (en maternité) ; 2eme dose de vaccin à 1 mois, 3eme dose de vaccin à 6 mois et contrôle de la réponse immune entre le 7eme et le 12eme mois (par le médecin traitant). Cette étude vise à évaluer la compliance du système de soins envers ces recommandations qui exigent l'intervention des maternités et des médecins traitants et qui s'étalent dans le temps. Pour ce faire, un recensement rétrospectif des enfants nés de mère avec une hépatite B chronique, en 2005 et 2006 dans 4 maternités vaudoises, a été effectué. Les mesures appliquées par les maternités, les informations transmises aux médecins traitants et les mesures appliquées par ces derniers ont été évaluées. Sur un total de 10'412 parturientes testées, 70 présentent une infection chronique et 51 acceptent le recrutement dans l'étude (représentant un collectif de 54 enfants). En maternité, l'immunisation active et passive est effectuée chez tous les enfants. L'évidence qu'elle est effectuée dans les 12 heures suivant la naissance est fournie dans 61% des cas (mais dans 100% des dossiers dans lequel ce renseignement est consigné). La nécessité de poursuivre la vaccination n'est mentionné au médecin traitant que dans 15% des cas, et dans seulement 11% des cas les modalités du calendrier vaccinal sont précisées. La recommandation d'effectuer un contrôle sérologique n'apparaît dans aucun document de transmission. Chez les médecins traitants, la 2eme dose de vaccin est administrée à 100% des enfants, mais seulement dans 15% des cas dans les délais recommandés. La 3eme dose de vaccination est administrée à 98% des enfants, mais seulement dans 43% des cas dans les délais recommandés. La sérologie de contrôle n'est effectuée que chez 24% des enfants, et seulement dans 7% des cas dans les délais recommandés. Les maternités appliquent les mesures de prophylaxie dans le délai imparti, tout au moins quand l'heure d'intervention est indiquée. Les médecins traitants sont rarement informés de la nécessité de compléter la vaccination et jamais des modalités ni de la nécessité d'effectuer un contrôle sérologique. L'application des mesures de prévention par les médecins traitants est non conforme aux recommandations. Nous émettons l'hypothèse que cet état reflète la carence d'information de la part des maternités et nous proposons que celles-ci utilisent un document de transmission standardisé qui indique précisément aux médecins traitants ce qui reste à faire, et quand, en matière de prévention de l'hépatite B chez le nouveau-né/nourrisson.

Medium access control messaging scheme for cognitive radio networks

Los sistemas de radio cognitivos son una solución a la deficiente distribución del espectro inalámbrico de frecuencias. Usando acceso dinámico al medio, los usuarios secundarios pueden comunicarse en canales de frecuencia disponibles, mientras los usuarios asignados no están usando dichos canales. Un buen sistema de mensajería de control es necesario para que los usuarios secundarios no interfieran con los usuarios primarios en las redes de radio cognitivas. Para redes en donde los usuarios son heterogéneos en frecuencia, es decir, no poseen los mismos canales de frecuencia para comunicarse, el grupo de canales utilizado para transmitir información de control debe elegirse cuidadosamente. Por esta razón, en esta tesis se estudian las ideas básicas de los esquemas de mensajería de control usados en las redes de radio cognitivas y se presenta un esquema adecuado para un control adecuado para usuarios heterogéneos en canales de frecuencia. Para ello, primero se presenta una nueva taxonomía para clasificar las estrategias de mensajería de control, identificando las principales características que debe cumplir un esquema de control para sistemas heterogéneos en frecuencia. Luego, se revisan diversas técnicas matemáticas para escoger el mínimo número de canales por los cuales se transmite la información de control. Después, se introduce un modelo de un esquema de mensajería de control que use el mínimo número de canales y que utilice las características de los sistemas heterogéneos en frecuencia. Por último, se comparan diversos esquemas de mensajería de control en términos de la eficiencia de transmisión.

The identification of two Trypanosoma cruzi I genotypes from domestic and sylvatic transmission cycles in Colombia based on a single polymerase chain reaction amplification of the spliced-leader intergenic region

A single polymerase chain reaction (PCR) reaction targeting the spliced-leader intergenic region of Trypanosoma cruzi I was standardised by amplifying a 231 bp fragment in domestic (TcIDOM) strains or clones and 450 and 550 bp fragments in sylvatic strains or clones. This reaction was validated using 44 blind coded samples and 184 non-coded T. cruzi I clones isolated from sylvatic triatomines and the correspondence between the amplified fragments and their domestic or sylvatic origin was determined. Six of the nine strains isolated from acute cases suspected of oral infection had the sylvatic T. cruzi I profile. These results confirmed that the sylvatic T. cruzi I genotype is linked to cases of oral Chagas disease in Colombia. We therefore propose the use of this novel PCR reaction in strains or clones previously characterised as T. cruziI to distinguish TcIDOMfrom sylvatic genotypes in studies of transmission dynamics, including the verification of population selection within hosts or detection of the frequency of mixed infections by both T. cruzi I genotypes in Colombia.

Incidence and transmission patterns of tuberculosis among indigenous populations in Brazil

Approximately 10% of the Brazilian indigenous population lives in the state of Mato Grosso do Sul (MS), where a large number of new cases of tuberculosis (TB) are reported. This study was conducted to assess TB occurrence, transmission and the utility of TB diagnosis based on the Ogawa-Kudoh (O-K) culture method in this remote population. The incidence of TB was estimated by a retrospective review of the surveillance data maintained by the Notifiable Diseases Surveillance System for the study region. The TB transmission pattern among indigenous people was assessed by genotyping Mycobacterium tuberculosis isolates using the IS 6110restriction fragment length polymorphism (RFLP) technique. Of the 3,093 cases identified from 1999-2001, 610 (~20%) were indigenous patients (average incidence: 377/100,000/year). The use of the O-K culture method increased the number of diagnosed cases by 34.1%. Of the genotyped isolates from 52 indigenous patients, 33 (63.5%) belonged to cluster RFLP patterns, indicating recently transmitted TB. These results demonstrate high, on-going TB transmission rates among the indigenous people of MS and indicate that new efforts are needed to disrupt these current transmissions.

Interruption of vector transmission by native vectors and “the art of the possible”

In a recent article in the Reader’s Opinion, advantages and disadvantages of the certification processes of interrupted Chagas disease transmission (American trypanosomiasis) by native vector were discussed. Such concept, accepted by those authors for the case of endemic situations with introduced vectors, has been built on a long and laborious process by endemic countries and Subregional Initiatives for Prevention, Control and Treatment of Chagas, with Technical Secretariat of the Pan American Health Organization/World Health Organization, to create a horizon target and goal to concentrate priorities and resource allocation and actions. With varying degrees of sucess, which are not replaceable for a certificate of good practice, has allowed during 23 years to safeguard the effective control of transmission of Trypanosoma cruzi not to hundreds of thousands, but millions of people at risk conditions, truly “the art of the possible.”