Typhoid fever infection - Antibiotic resistance and vaccination strategies: A narrative review.

Typhoid fever is a bacterial infection caused by the Gram-negative bacterium Salmonella enterica subspecies enterica serovar Typhi (S. Typhi), prevalent in many low- and middle-income countries. In high-income territories, typhoid fever is predominantly travel-related, consequent to travel in typhoid-endemic regions; however, data show that the level of typhoid vaccination in travellers is low. Successful management of typhoid fever using antibiotics is becoming increasingly difficult due to drug resistance; emerging resistance has spread geographically due to factors such as increasing travel connectivity, affecting those in endemic regions and travellers alike. This review provides an overview of: the epidemiology and diagnosis of typhoid fever; the emergence of drug-resistant typhoid strains in the endemic setting; drug resistance observed in travellers; vaccines currently available to prevent typhoid fever; vaccine recommendations for people living in typhoid-endemic regions; strategies for the introduction of typhoid vaccines and stakeholders in vaccination programmes; and travel recommendations for a selection of destinations with a medium or high incidence of typhoid fever.

Clinical Study on the Melarsoprol-Related Encephalopathic Syndrome: Risk Factors and HLA Association.

Melarsoprol administration for the treatment of late-stage human African trypanosomiasis (HAT) is associated with the development of an unpredictable and badly characterized encephalopathic syndrome (ES), probably of immune origin, that kills approximately 50% of those affected. We investigated the characteristics and clinical risk factors for ES, as well as the association between the Human Leukocyte Antigen (HLA) complex and the risk for ES in a case-control study. Late-stage Gambiense HAT patients treated with melarsoprol and developing ES (69 cases) were compared to patients not suffering from the syndrome (207 controls). Patients were enrolled in six HAT treatment centres in Angola and in the Democratic Republic of Congo. Standardized clinical data was obtained from all participants before melarsoprol was initiated. Class I (HLA-A, HLA-B, HLA-Cw) and II (HLA-DR) alleles were determined by PCR-SSOP methods in 62 ES cases and 189 controls. The principal ES pattern consisted in convulsions followed by a coma, whereas ES with exclusively mental changes was not observed. Oedema, bone pain, apathy, and a depressed humour were associated with a higher risk of ES, while abdominal pain, coma, respiratory distress, and a Babinski sign were associated with higher ES-associated mortality. Haplotype C*14/B*15 was associated with an elevated risk for ES (OR: 6.64; p-value: 0.008). Haplotypes A*23/C*14, A*23/B*15 and DR*07/B*58 also showed a weaker association with ES. This result supports the hypothesis that a genetically determined peculiar type of immune response confers susceptibility for ES.

Infection by Intestinal Parasites, Stunting and Anemia in School-Aged Children from Southern Angola.

INTRODUCTION: Intestinal parasites are responsible for morbidity in children worldwide, especially in low income countries. In the present study we determine the prevalence of intestinal parasites and explore its association with anemia and stunting in school-aged children. METHODS: A cross-sectional study was conducted from September to October 2010 enrolling 328 children attending the primary school in Lubango, the second largest city after the capital Luanda. Stool samples were collected for parasite detection through microscopy and molecular identification of Entamoeba histolytica and Entamoeba dispar. Stunting was assessed using the z-scores of height for age and hemoglobin concentration was determined using a portable hemoglobin analyzing system. RESULTS: The global prevalence of pathogenic intestinal parasites was 44.2%, the most common being Ascaris lumbricoides (22.0%), Giardia lamblia (20.1%) and Hymenolepis nana (8.8%). Molecular detection revealed that 13.1% of the children carried E. dispar and 0.3% were infected with E. histolytica. The prevalence of stunting (mild to severe) was 41.5%. Stunting was more frequent in older children (p = 0.006, OR = 1.886), while anemia was more frequent in younger children (p = 0.005, OR = 2.210). The prevalence of anemia was 21.6%, and we found a significant association with infection by H. nana (p = 0.031, OR = 2.449). CONCLUSIONS: This is one of the few published studies reporting intestinal parasites infection, nutritional status and anemia in children from Angola. Furthermore, the present work highlights the importance of regular intestinal parasites screening in children.

Direct Detection by the Xpert MTB/RIF Assay and Characterization of Multi and Poly Drug-Resistant Tuberculosis in Guinea-Bissau, West Africa.

BACKGROUND: This study aimed to evaluate the usefulness of the Xpert MTB/RIF assay for the rapid direct detection of M. tuberculosis complex (MTBC) strains and rifampicin resistance associated mutations in a resource-limited setting such as Guinea-Bissau and its implications in the management of tuberculosis (TB) and drug resistant tuberculosis, complementing the scarce information on resistance and genotypic diversity of MTBC strains in this West African country. METHODS AND RESULTS: This cross-sectional prospective study included 100 consecutive TB patients with positive acid-fast smears at two months of anti-tuberculosis treatment or in a re-treatment situation, between May and December 2012. Resistance to rifampicin was detected using the GeneXpert system and the Xpert MTB/RIF assay. MTBC isolates obtained with the BACTEC MGIT 960 system were tested for susceptibility to first- and second-line anti-tuberculosis drugs. Overall, the prevalence of multidrug-resistant tuberculosis (MDR-TB) was found to be 9 cases. Of these, 67% (6 patients) of confirmed MDR-TB cases had no past history of TB treatment and 33% (3 patients) were previously treated cases. Extensively drug-resistant TB was not found. Molecular typing of the MDR-TB strains revealed recent transmission patterns of imported MDR strains. CONCLUSIONS: The Xpert MTB/RIF assay was reliable for the detection of rifampicin resistant MTBC strains directly from sputum samples of patients undergoing first-line treatment for two months, being more trustworthy than the simple presence of acid-fast bacilli in the smear. Its implementation is technically simple, does not require specialized laboratory infrastructures and is suitable for resource-limited settings when a regular source of electricity and maintenance is available as well as financial and operation sustainability is guaranteed by the health authorities. A high prevalence of MDR-TB among patients at risk of MDR-TB after two months of first-line treatment was found, in support of the WHO recommendations for its use in the management of this risk group.

Giardia duodenalis and soil-transmitted helminths infections in children in São Tomé and Príncipe: do we think Giardia when addressing parasite control?

Giardia duodenalis prevalence is commonly as high as soil-transmitted helminths (STH), nevertheless is not considered for large-scale chemotherapy through mass drug administration (MDA) due to its short incubation period and frequent reinfections, its control being associated to improving access to water and sanitation. A study enrolling 444 children attending preschools was conducted in May 2011 during a deworming campaign. Faecal samples were obtained and analysed through microscopy of wet mounting and after Kato-Katz and formol-ether concentration techniques. The majority of children were infected with at least one pathogenic parasite (86.7%, 385 of 444). Ascaris lumbricoides and Trichuris trichiura (56.3%, 250 of 444 and 52.5%, 233 of 444, respectively) were the most frequent parasites followed by G. duodenalis infecting 41.7% (185 of 444) of the children. The present work aimed at obtaining updated information concerning intestinal parasite infections in children attending preschools in São Tomé and Príncipe and to contribute for the adequate management of the enteric infections.

Angola's 2013 dengue outbreak: clinical, laboratory and molecular analyses of cases from four Portuguese institutions.

INTRODUCTION: Dengue virus (DENV) is the arbovirus with the widest impact on human health. In Africa in general, and in Angola in particular, the epidemiology and public health impact of DENV is far from clear. However, rapid population growth, unplanned urbanization, increased international travel, and the presence of virus major vector (Aedes aegypti) in the country suggest that DENV transmission may occur. METHODOLOGY: In parallel to the occurrence of a dengue outbreak affecting the capital of Angola, between March and July 2013 four Portuguese institutions diagnosed dengue infection in 146 individuals returning to Portugal. Clinical presentation, laboratory findings, and molecular analyses of partial viral genomic segments were performed. RESULTS: The mean age of the individuals included in this study was 42 years old, the majority being men of Portuguese nationality, reporting various lengths of stay in Angola. Fever was the most reported clinical sign, being frequently associated (61.0%) with myalgia and headache. Hematological values, including hematocrit, white-blood cell and platelets counts, correlated with the absence of severe or complicated cases, or coagulation disorders. No deaths were observed. Viral NS1 was detected in 56.2% of the samples, and all NS1 negative cases had anti-dengue IgM antibodies. RT-PCR indicated the presence of DENV1, which was confirmed by phylogenetic analysis of 25 partial NS5 viral sequences. CONCLUSION: The DENV cases analyzed conformed to classical and uncomplicated dengue, caused by the suggested exclusive circulation of a genetically homogeneous DENV1 of genotype III, apparently with a single origin.

Molecular and Clinical Characterization of Giardia duodenalis Infection in Preschool Children from Lisbon, Portugal.

Giardia duodenalis is the most prevalent intestinal protozoan infection especially in children. In Portugal scarce data are available relative to this infection in preschoolers. The present study was conducted from April to July 2009 in public preschools in Lisbon enrolling 316 children. Stool examination was performed through microscopy. Molecular analysis was conducted in all positive samples for G. duodenalis in order to determine the assemblage and subassemblage of this parasite. Eight of the preschoolers studied children (2.5%, 8/316) were infected with G. duodenalis. Additionally the brother of one of the infected children was also infected. Genotyping analysis targeting ssu-rRNA and ß -giardin loci revealed six infections with assemblage A and 3 with assemblage B. Sub-assemblage determination was possible in four of the samples, with three A2 and one A3. The limited number of cases precluded an association of a determined symptom with an assemblage. The data presented here show the relevance of considering G. duodenalis analysis in children with intestinal complaints even in developed countries.

Prevalence and Level of Antibodies Anti-Plasmodium spp. in Travellers with Clinical History of Imported Malaria.

In this study, we show that 40.29% of travellers with a possible history of malaria exposure were positive for anti-Plasmodium spp. antibodies, while these individuals were negative by microscopy. The antibody test described here is useful to elucidate malaria exposure in microscopy-negative travellers from endemic countries.

Trypanosoma brucei: immunisation with plasmid DNA encoding invariant surface glycoprotein gene is able to induce partial protection in experimental African trypanosomiasis.

Trypanosoma brucei is the etiological agent responsible for African trypanosomiasis, an infectious pathology which represents a serious problem of public health and economic losses in Sub-Saharan Africa. As one of the foremost neglected illnesses, few resources have been available for the development of vaccines or new drugs, in spite of the current therapeutical drugs showing little efficiency and high toxicity. Hence, it is obviously important to widen effective therapeutics and preventive strategies against African trypanosomiasis. In this work, we use the DNA vaccine model to evaluate immunisation effectiveness in mice challenged with Trypanosoma brucei brucei. We demonstrate that Balb/C mice immunised intramuscularly with a single dose of a DNA plasmid encoding a bloodstream-stage specific invariant surface glycoprotein (ISG) are partially protected from a lethal dose of T. b. brucei. Interestingly, the surviving animals show high levels of IgG2a anti-trypanosoma antibodies, suggesting that the Th1 response profile seems important for the induced mechanisms of immune protection.

Partial biochemical characterization of a metalloproteinase from the bloodstream forms of Trypanosoma brucei brucei parasites.

Metalloproteinases (MMP) belong to the family of cation dependent endopeptidases that degrade matrices at physiological pH and to cleave extracellular matrix proteins. They play an important role in diverse physiological and pathological processes; not only there diverse types of MMP differ in structure and functionally, but also their enzymatic activity is regulated at multiple levels. Trying to shed some light over the processes that govern the pathology of African Trypanosomiasis, the aim of the present study was to examine the proteolytic activity of the crude trypanosome protein extract obtained from the bloodstream forms of Trypanosoma brucei brucei parasites. We hereby report the partial biochemical characterization of a neutral Trypanosoma brucei-metalloproteinase that displays marked proteolytic activities on gelatin and casein, with a molecular mass of approximately 40 kDa, whose activity is strongly dependent of pH and temperature. Furthermore, we show that this activity can be inhibited by classical MMP inhibitors such as EDTA, EGTA, phenantroline, and also by tetracycline and derivatives. This study has a relevant role in the search for new therapeutical targets, for the use of metalloproteinases inhibitors as treatment strategies, or as enhancement to trypanocidal drugs used in the treatment of the disease.

DNA vaccines: a rational design against parasitic diseases.

Parasitic diseases are one of the most devastating causes of morbidity and mortality worldwide. Although immunization against these infections would be an ideal solution, the development of effective vaccines has been hampered by specific challenges posed by parasitic pathogens. Plasmid-based DNA vaccines may prove to be promising immunization tools in this area because vectors can be designed to integrate several antigens from different stages of the parasite life cycle or different subspecies; vaccines, formulations and immunization protocols can be tuned to match the immune response that offers protective immunity; and DNA vaccination is an affordable platform for developing countries. Partial and full protective immunity have been reported following DNA vaccination against the most significant parasitic diseases in the world.

Molecular identification of T. brucei s.l. in tsetse flies after long-term permanence in field traps.

BACKGROUND: Tsetse flies (Glossina spp.) are responsible for the transmission of trypanosomes, agents of animal and Human African Trypanosomiasis (HAT). These diseases are associated with considerable animal and human economical loss, morbidity and mortality. The correct identification of trypanosomes species infecting tsetse flies is crucial for adequate control measures. Identification presently requires technically difficult, cumbersome and expensive on-site fly dissection. To obviate this difficulty we explored the possibility of correctly identifying trypanosomes in tsetse collected, under field conditions, only for number determination. METHODOLOGY: Tsetse flies, that remained exposed for weeks in field traps in the Vista Alegre HAT focus in Angola, were obtained. The flies were not dissected on site and were stored at room temperature for months. DNA extraction using the whole tsetse bodies and PCR analysis were performed in 73 randomly chosen flies. RESULTS: Despite the extensive degradation of the tsetse, DNA extraction was conducted successfully in 62 out of the 73 flies. PCR analysis detected the presence of T. brucei s.l DNA in 3.2 % of the tsetse. CONCLUSIONS: This approach could be cost-effective and suitable for vector related HAT control activities in the context of countries where entomological trained personnel is missing and financial resources are limited.

Trans-sialidase from Trypanosoma brucei as a potential target for DNA vaccine development against African trypanosomiasis.

African trypanosomiasis (AT), also known as sleeping sickness in humans and Nagana in animals, is a disease caused by the protozoan parasite Trypanosoma brucei. AT is an extremely debilitating disease in human, cattle, and wild animals, and the treatment is difficult with frequent relapses. This work shows that BALB-c mice immunized intramuscularly with a single dose (100 microg) of a plasmid DNA encoding the 5'-terminal region of the trans-sialidase (nTSA) gene of T. brucei brucei are able to produce IgG antibodies that bind to the bloodstream form of T. brucei-protein extract and recognize the recombinant nTSA protein, expressed in Escherichia coli. Furthermore, this DNA vaccination process was able to protect 60% of mice submitted to a challenge assay with the infective form of T. brucei brucei parasites. These results demonstrate that a DNA vaccine coding for trans-sialidase from T. brucei is potentially useful in the prophylaxis of AT.

An alternative approach to detect Trypanosoma in Glossina (Diptera, Glossinidae) without dissection.

BACKGROUND: Determining if a tsetse fly is infected by trypanosomes and thus potentially able to transmit trypanosome-related human and animal diseases is an extremely laborious and time-consuming task to perform, especially under field conditions. In this study we tested a possible alternative approach that uses the entire insect vector for DNA extraction and PCR analysis to detect and identify Trypanosoma spp. in field collected tsetse flies. METHODOLOGY: DNA extraction was performed using a method originally developed for tick DNA extraction followed by PCR detection and identification of Trypanosoma spp. RESULTS: Two out of 62 flies captured in Equatorial Guinea carried DNA of T. brucei s.l. and Trypanosoma vivax. T. congolense forest, T. congolense savannah and T. congolense Kilifi were not detected. CONCLUSIONS: The approach we employed allowed the molecular detection and species identification of trypanosomes using the whole vector body for DNA extraction. Although the approach does not give direct information on tsetse infectivity, it provides valuable information about trypanosome species circulating in a tsetse fly vector population. The method allows an effective processing of a large number of field captured tsetse in a central laboratory.

Sexually transmitted infections in an African migrant population in Portugal: a base-line study.

BACKGROUND: For geographical and recent historic reasons, Portugal is a gateway and home for immigration from sub-Saharan countries. Misconceptions related to these populations often lead to consider them as high-frequency clusters for dissemination of sexually transmitted infections (STIs). Epidemiological evidence-based data is needed to elucidate these issues and baseline prevalence studies are the starting point for this. METHODOLOGY: A prospective study was conducted in 220 African migrants (171 men and 49 women), recently arrived in Portugal, at the time of their first consultation. The presence of STIs was evaluated using a clinical syndromic approach and biological confirmation for gonorrhoea, Chlamydia trachomatis genital infection, syphilis, Hepatitis B and Human Immunodeficiency Virus (HIV) infection. RESULTS: Global prevalence of the targeted infections were 1.8% for gonorrhoea, 0 % for Chlamydia infection, 4.1% for Syphilis, 5.9% for HBsAg presence and 7.3% for HIV infection. Globally, 16.4% of the studied persons had at least one sexually transmitted infection. CONCLUSIONS: We concluded that prevalence rates encountered in this population is similar to that of non-migrant Portuguese populations with a high risk for sexually transmitted diseases. Therefore migration from sub-Saharan Africa doesn't seem to constitute a particularly critical isolated factor for public health risk of STIs in the community.

Pharmacists and travel advice for tropics in Lisbon (Portugal).

BACKGROUND: In Portugal, little is known about the quality of advice given to international travelers by pharmacists. The aim of this study was to determine pharmacists' training, experience, and interest in travel medicine and to assess the technical quality of the information given. METHODS: We sent a postal questionnaire to all pharmacies in the Lisbon area. The technical director or another graduate pharmacist was asked to complete the questionnaire. RESULTS: A total of 251 pharmacists participated in the study. Most of them (93.2%) did not have any training in travel medicine, and most of them expressed a wish to be informed and/or updated on this subject. The number of advised travelers was low. The use of repellent, protective clothes, and mosquito bed nets was the most frequent advice on protection against mosquito bites. From a subgroup of 170 pharmacists, 43.5% indicated mefloquine and 44.1% indicated chloroquine as malaria chemoprophylaxis to African countries. A significant association existed between the variables "to indicate mefloquine" and "seeks to be informed/updated on travel medicine." Those who indicated chloroquine tended to like travel medicine less. Concerning diarrhea prevention and treatment, the consumption of bottled and/or treated water and the administration of antibiotics during the episode were the most reported advice. Concerning vaccination against yellow fever, only 8 of 91 pharmacists correctly indicated all Portuguese-speaking countries with and without the risk of this disease. CONCLUSIONS: Studied pharmacists need training in travel medicine. Travel advice was incomplete and/or incorrect and must be improved.

Quality assessment in a travel clinic: a study of travelers' knowledge about malaria.

BACKGROUND: Quality in health care delivery is considered essential and should be expected for all who deliver health care. We were not able to identify in Portugal any previous studies that assessed the quality of travel medicine consultations. The aims of this study was to assess the impact of travel health advice on travelers' knowledge and the quality of the outcome of the travel consultations at the Institute of Hygiene and Tropical Medicine, Portugal. METHOD: We selected the quasi-experimental model "separate-sample pretest-posttest design." Two random samples were obtained (control and experimental groups). An anonymous self-administered questionnaire was applied during the second half of 2002, until we had received about 200 questionnaires for each group. The questions assessed travelers' knowledge of malaria, its transmission, prevention, and clinical features. RESULTS: There was a significant improvement of travelers' knowledge in the postconsultation group, with 98.5% of individuals understanding that malaria is transmitted by mosquito bite (p= 0.005), 91.5% that malaria may be prevented by appropriate prophylactic medication (p= 0.007), and 93% knowing that malaria is prevented by avoiding mosquito bites (p= 0.003). However, almost half of the postconsultation group did not realize that there was no vaccine available for preventing malaria (p < 0.001) or that avoiding unsafe food and drink did not prevent malaria (p= 0.006). About 53% gave correct answers about malaria incubation periods (p < 0.001), and 91.1% were able to identify the initial symptoms of malaria (p < 0.001). CONCLUSIONS: Travel medicine consultations increase the knowledge base of travelers but do not achieve 100% correct answers. Our results suggest that during a travel health consultation, critical information is assimilated about the prevention of malaria, but myths and misunderstandings that are held by travelers are not completely dispelled.