Interrupting Chagas disease transmission in Venezuela

The interruption of vectorial transmission of Chagas disease in Venezuela is attributed to the combined effects of ongoing entomoepidemiological surveillance, ongoing house spraying with residual insecticides and the concurrent building and modification of rural houses in endemic areas during almost five decades. The original endemic areas which totaled 750,000 km², have been reduced to 365,000 km². During 1958-1968, initial entomological evaluations carried out showed that the house infestation index ranged between 60-80%, the house infection index at 8-11% and a house density index of 30-50 triatomine bugs per house. By 1990-98, these indexes were further reduced to 1.6-4.0%, 0.01-0.6% and 3-4 bugs per house respectively. The overall rural population seroprevalence has declined from 44.5% (95% C.I.: 43.4-45.3%) to 9.2% (95% C.I.: 9.0-9.4%) for successive grouped periods from 1958 to 1998. The annual blood donor prevalence is firmly established below 1%. The population at risk of infection has been estimated to be less than four million. Given that prevalence rates are stable and appropriate for public health programmes, consideration has been given to potential biases that may distort results such as: a) geographical differences in illness or longevity of patients; b) variations in levels of ascertainment; c) variations in diagnostic criteria; and d) variations in population structure, mainly due to appreciable population migration. The endemic areas with continuous transmission are now mainly confined to piedmonts, as well as patchy foci in higher mountainous ranges, where the exclusive vector is Rhodnius prolixus. There is also an unstable area, of which landscapes are made up of grasslands with scattered broad-leaved evergreen trees and costal plains, where transmission is very low and occasional outbreaks are reported.

Sexual transmission of hepatitis C virus

In order to contribute to a better understanding of the forms of acquisition of hepatitis C virus (HCV) in Brazil, with special emphasis on sexual transmission, we determined the presence of HCV infection in regular partners and in non-sexual home communicants of blood donors seen at Fundação Pró-Sangue Hemocentro de São Paulo from January 1992 to July 1996. Of 154 blood donors with HCV infection (index cases), 111 had had regular partners for at least 6 months. Sixty-eight of 111 partners were evaluated for HCV infection. Of these, 8 (11.76%) were considered to have current or previous HCV infection; a history of sexually transmissible diseases and index cases with a positive HCV-RNA test were more prevalent among partners with HCV infection. Of the 68 index cases whose partners were studied, 56 had non-sexual home communicants. Of the total of 81 home communicants, 66 accepted to be evaluated for HCV infection. None of them was HCV-positive, suggesting that the high prevalence of HCV infection among partners may be attributed at least partially to sexual transmission.

Pasteurization of human milk to prevent transmission of Chagas disease

Although admittedly transmission of Trypanosoma cruzi infection through breastfeeding is a rare event, it involves serious risks. To test the effectiveness of pasteurization in preventing this mode of infection, three sets of samples of human milk were tested: a - contaminated with T. cruzi and pasteurized; b - contaminated with T. cruzi and non-pasteurized; c - non-contaminated and pasteurized. Samples from all sets were orally and intraperitoneally administered to 90 BALB/c mice. The animals inoculated with contaminated, non-pasteurized samples, got the infection. Controls and the animals inoculated with contaminated and pasteurized milk were not infected. The hypothesis was accepted that pasteurization inactivates T. cruzi trypomastigotes.

Chagasic megaesophagus and megacolon diagnosed in childhood and probably caused by vertical transmission

Reports on children presenting symptoms compatible with the chronic phase of Chagas disease are sporadic. We report a case of a 7-year-old boy who had megaesophagus and megacolon, both of them a consequence of the trypanosomiasis. The etiology was established by means of laboratory and histological features. Based on epidemiological data, the authors concluded that vertical transmission was the most probable route of acquisition. This diagnosis should be considered in children presenting similar complaints, even those living away from endemic areas.

Experimental infection and horizontal transmission of Bartonella henselae in domestic cats

In order to study B. henselae transmission among cats, five young cats were kept in confinement for two years, one of them being inoculated by SC route with B. henselae (10(5) UFC). Only occasional contact among cats occurred but the presence of fleas was observed in all animals throughout the period. Blood culture for isolation of bacteria, PCR-HSP and FTSZ (gender specific), and BH-PCR (species-specific), as well as indirect immunofluorescence method for anti-B. henselae antibodies were performed to confirm the infection of the inoculated cat as well as the other naive cats. Considering the inoculated animal, B. henselae was first isolated by blood culture two months after inoculation, bacteremia last for four months, the specific antibodies being detected by IFI during the entire period. All contacting animals presented with bacteremia 6 months after experimental inoculation but IFI did not detect seroconversion in these animals. All the isolates from these cats were characterized as Bartonella (HSP and FTSZ-PCR), henselae (BH-PCR). However, DNA of B. henselae could not be amplified directly from peripheral blood by the PCR protocols used. Isolation of bacteria by blood culture was the most efficient method to diagnose infection compared to PCR or IFI. The role of fleas in the epidemiology of B. henselae infection in cats is discussed.

Natural infection of Deroceras laeve (Mollusca: gastropoda) with metastrongylid larvae in a transmission focus of abdominal angiostrongyliasis

Angiostrongylus costaricensis is a nematode parasitic of rodents. Man may become infected by ingestion of the third stage larvae produced within the intermediate hosts, usually slugs from the family Veronicellidae. An epidemiological study carried out in a locality in southern Brazil (western Santa Catarina State) where these slugs are a crop pest and an important vector for A. costaricensis has documented for the first time the natural infection of Deroceras laeve with metastrongylid larvae. This small limacid slug is frequently found amid the folds of vegetable leaves and may be inadvertently ingested. Therefore D. laeve may have an important role in transmission of A. costaricensis to man.

No evidence of vertical transmission of HTLV-I in bottle-fed children

The most frequent pathway of vertical transmission of HTLV-I is breast-feeding, however bottle fed children may also become infected in a frequency varying from 4 to 14%. In these children the most probable routes of infection are transplacental or contamination in the birth canal. Forty-one bottle-fed children of HTLV-I seropositive mothers in ages varying from three to 39 months (average age of 11 months) were submitted to nested polymerase chain reaction analysis (pol and tax genes). 81.5% of the children were born by an elective cesarean section. No case of infection was detected. The absence of HTLV-I infection in these cases indicates that transmission by transplacental route may be very infrequent.

Characterization of Pinus spp. needles by gas chromatography and mass spectrometry: Application to plant-insect interactions

Dissertação apresentada para obtenção do Grau de Doutor em Ciências do Ambiente pela Universidade Nova de Lisboa, Faculdade de Ciências e Tecn

Oral transmission of Chagas disease: importance of Trypanosoma cruzi biodeme in the intragastric experimental infection

Oral transmission of Trypanosoma cruzi has been suspected when epidemic episodes of acute infection were observed in areas devoid of domiciled insect vectors. Considering that the distribution of T. cruzi biodemes differs in sylvatic and domestic cycles, results of studies on biodemes can be of interest regarding oral transmission. The infectivity of T. cruzi strains of different biodemes was tested in mice subjected to infection by the digestive route (gavage). Swiss mice were infected either with the Peruvian strain (Biodeme Type I, Z2b) or the Colombian strain (Biodeme Type III, Z1, or T. cruzi I); for control, intraperitoneal inoculation was performed in a group of mice. The Colombian strain revealed a similar high infectivity and pathogenicity when either route of infection was used. However, the Peruvian strain showed contrasting levels of infectivity and pathogenicity, being high by intraperitoneal inoculation and low when the gastric route was used. The higher infectivity of the Colombian strain (Biodeme Type III) by gastric inoculation is in keeping with its role in the epidemic episodes of acute Chagas disease registered in the literature, since strains belonging to Biodeme III are most often found in sylvatic hosts.

Electrospun Polyaniline-Reduced Graphene Oxide Composite Nanofibers Based High Sensitive Ammonia Gas Sensor

Ammonia is an important gas in many power plants and industrial processes so its detection is of extreme importance in environmental monitoring and process control due to its high toxicity. Ammonia’s threshold limit is 25 ppm and the exposure time limit is 8 h, however exposure to 35 ppm is only secure for 10 min. In this work a brief introduction to ammonia aspects are presented, like its physical and chemical properties, the dangers in its manipulation, its ways of production and its sources. The application areas in which ammonia gas detection is important and needed are also referred: environmental gas analysis (e.g. intense farming), automotive-, chemical- and medical industries. In order to monitor ammonia gas in these different areas there are some requirements that must be attended. These requirements determine the choice of sensor and, therefore, several types of sensors with different characteristics were developed, like metal oxides, surface acoustic wave-, catalytic-, and optical sensors, indirect gas analyzers, and conducting polymers. All the sensors types are described, but more attention will be given to polyaniline (PANI), particularly to its characteristics, syntheses, chemical doping processes, deposition methods, transduction modes, and its adhesion to inorganic materials. Besides this, short descriptions of PANI nanostructures, the use of electrospinning in the formation of nanofibers/microfibers, and graphene and its characteristics are included. The created sensor is an instrument that tries to achieve a goal of the medical community in the control of the breath’s ammonia levels being an easy and non-invasive method for diagnostic of kidney malfunction and/or gastric ulcers. For that the device should be capable to detect different levels of ammonia gas concentrations. So, in the present work an ammonia gas sensor was developed using a conductive polymer composite which was immobilized on a carbon transducer surface. The experiments were targeted to ammonia measurements at ppb level. Ammonia gas measurements were carried out in the concentration range from 1 ppb to 500 ppb. A commercial substrate was used; screen-printed carbon electrodes. After adequate surface pre-treatment of the substrate, its electrodes were covered by a nanofibrous polymeric composite. The conducting polyaniline doped with sulfuric acid (H2SO4) was blended with reduced graphene oxide (RGO) obtained by wet chemical synthesis. This composite formed the basis for the formation of nanofibers by electrospinning. Nanofibers will increase the sensitivity of the sensing material. The electrospun PANI-RGO fibers were placed on the substrate and then dried at ambient temperature. Amperometric measurements were performed at different ammonia gas concentrations (1 to 500 ppb). The I-V characteristics were registered and some interfering gases were studied (NO2, ethanol, and acetone). The gas samples were prepared in a custom setup and were diluted with dry nitrogen gas. Electrospun nanofibers of PANI-RGO composite demonstrated an enhancement in NH3 gas detection when comparing with only electrospun PANI nanofibers. Was visible higher range of resistance at concentrations from 1 to 500 ppb. It was also observed that the sensor had stable, reproducible and recoverable properties. Moreover, it had better response and recovery times. The new sensing material of the developed sensor demonstrated to be a good candidate for ammonia gas determination.

Microwave treatment of human milk to prevent transmission of Chagas disease

It is recognized that breast feeding is an alternative means of transmission of Chagas disease. However, thermal treatment of milk can prevent this occurrence. As domestic microwave ovens are becoming commonplace, the efficacy of microwave thermal treatment in inactivating Trypanosoma cruzi trypomastigotes in human milk was tested. Human milk samples infected with T. cruzi trypomastigotes (Y strain) from laboratory-infected mice, were heated to 63 °C in a domestic microwave oven (2 450 MHz, 700 W). Microscopical and serological examinations demonstrated that none of the animals inoculated orally or intraperitoneally with infected milk which had been treated, got the infection, while those inoculated with untreated, infected milk, became infected. It was concluded that the simple treatment prescribed, which can easily be done at home, was effective in inactivating T. cruzi trypomastigotes contained in human milk.