Distribution of sibling species of Anopheles culicifacies s.l. and Anopheles fluviatilis s.l. and their vectorial capacity in eight different malaria endemic districts of Orissa, India

The study was undertaken in eight endemic districts of Orissa, India, to find the members of the species complexes of Anopheles culicifacies and Anopheles fluviatilis and their distribution patterns. The study area included six forested districts (Keonjhar, Angul, Dhenkanal, Ganjam, Nayagarh and Khurda) and two non-forested coastal districts (Puri and Jagatsingpur) studied over a period of two years (June 2007-May 2009). An. culicifacies A, B, C and D and An. fluviatilis S and T sibling species were reported. The prevalence of An. culicifacies A ranged from 4.2-8.41%, B from 54.96-76.92%, C from 23.08-33.62% and D from 1.85-5.94% (D was reported for the first time in Orissa, except for occurrences in the Khurda and Nayagarh districts). The anthropophilic indices (AI) were 3.2-4.8%, 0.5-1.7%, 0.7-1.37% and 0.91-1.35% for A, B, C and D, respectively, whereas the sporozoite rates (SR) were 0.49-0.54%, 0%, 0.28-0.37% and 0.41-0.46% for A, B, C and D, respectively. An. fluviatilis showed a similarly varied distribution pattern in which S was predominant (84.3% overall); its AI and SR values ranged from 60.7-90.4% and 1.2-2.32%, respectively. The study observed that the co-existence of potential vector sibling species of An. culicifacies (A, C and D) and An. fluviatilis S (> 50%) was responsible for the high endemicity of malaria in forested districts such as Dhenkanal, Keonjhar, Angul, Ganjam, Nayagarh and Khurda (> 5% slide positivity rate). Thus, the epidemiological scenario for malaria is dependent on the distribution of the vector sibling species and their vectorial capacity.

Rotavirus A genotype G1P[8]: a novel method to distinguish wild-type strains from the Rotarix® vaccine strain

Rotaviruses are important enteric pathogens for humans and animals. Group A rotaviruses (RV-A) are the most common agents of severe gastroenteritis in infants and young children and vaccination is the most effective method to reduce RV-A-associated diseases. G1P[8], the most prevalent RV-A genotype worldwide, is included in the RV-A vaccine Rotarix®. The discrimination between wild-type G1P[8] and vaccine G1P[8] strains is an important topic in the study of RV-A epidemiology to manage outbreaks and to define control measures for vaccinated children. In this study, we developed a novel method to segregate the wild-type and vaccine strains using restriction endonucleases. The dsRNA from the Rotarix® vaccine was sequenced and the NSP3 gene was selected as the target gene. The vaccine strain has a restriction pattern that is different than that of wild-type RV-A G1P[8] isolates after digestion with the restriction endonuclease BspHI. This pattern could be used as a marker for the differentiation of wild-type G1P[8] strains from the vaccine strain.

Presence of maternal anti-HBs antibodies does not influence hepatitis B vaccine response in Brazilian neonates

Recently, it was suggested that maternal hepatitis B surface antigen antibodies (anti-HBs) acquired transplacentally could play a negative role in newborn infants' immune response to the hepatitis B vaccine. We compared the hepatitis B virus (HBV) vaccine response in infants born to mothers previously vaccinated against HBV (n = 91) to infants born to mothers who were not previously vaccinated (n = 221). All newborn infants received three intramuscular doses (10 μg) of HBV vaccine (Butang®) at 0,1 and six months. The first dose was administered at the maternity hospital within 12 h of birth. The geometric mean titres of anti-HBs were not different among newborn infants born to mothers who were anti-HBs-negative (492.7 mIU/mL) and anti-HBs-positive (578.7 mIU/mL) (p = 0.38). Eight infants did not respond to the HBV vaccine. Of them, six were born to anti-HBs-negative mothers and two were born to mothers with anti-HBs titres less than 50 mlU/mL. Despite the mother's anti-HBs-positive status, our data show a good immunogenicity of the Brazilian HBV recombinant vaccine in neonates.

Malaria seroprevalence in blood bank donors from endemic and non-endemic areas of Venezuela

In Venezuela, a total of 363,466 malaria cases were reported between 1999-2009. Several states are experiencing malaria epidemics, increasing the risk of vector and possibly transfusion transmission. We investigated the risk of transfusion transmission in blood banks from endemic and non-endemic areas of Venezuela by examining blood donations for evidence of malaria infection. For this, commercial kits were used to detect both malaria-specific antibodies (all species) and malaria antigen (Plasmodium falciparum only) in samples from Venezuelan blood donors (n = 762). All samples were further studied by microscopy and polymerase chain reaction (PCR). The antibody results showed that P. falciparum-infected patients had a lower sample/cut-off ratio than Plasmodium vivax-infected patients. Conversely, a higher ratio for antigen was observed among all P. falciparum-infected individuals. Sensitivity and specificity were higher for malarial antigens (100 and 99.8%) than for antibodies (82.2 and 97.4%). Antibody-positive donors were observed in Caracas, Ciudad Bolívar, Puerto Ayacucho and Cumaná, with prevalences of 1.02, 1.60, 3.23 and 3.63%, respectively. No PCR-positive samples were observed among the donors. However, our results show significant levels of seropositivity in blood donors, suggesting that more effective measures are required to ensure that transfusion transmission does not occur.

Acute diarrhoea in a community cohort of children who received an oral rotavirus vaccine in Northeast Brazil

Rotavirus is an important cause of childhood diarrhoea. A monovalent rotavirus vaccine (Rotarix®) was introduced into the Immunization Program of Brazil in 2006. In this study, we describe the incidence and burden of disease of rotavirus diarrhoea in two cohorts of children (vaccinated and unvaccinated). We followed two groups of 250 children under one year old, who were enrolled in December 2006 from a low-income residential area in Northeast Brazil. The children were monitored every two weeks for two years. Stool samples from children with diarrhoea were examined for the presence of rotavirus. Rotaviruses were genotyped using real time-polymerase chain reaction. The mean numbers of all-cause diarrhoea episodes/child (adjusted for age) in the first year were 0.87 and 0.84, in vaccinated and unvaccinated children, respectively. During the second year, the number of episodes/child decreased to 0.52 and 0.42. Only 16 (4.9%) of 330 stool samples were rotavirus-positive (10 vaccinated and 6 unvaccinated children) and only P[4]G2 rotaviruses were identified. All-cause diarrhoea episodes were more severe in unvaccinated children in the first year of age (p < 0.05), while vaccinated children had more severe episodes 18 months after vaccination. Rotavirus diarrhoea incidence was very low in both groups.

Monitoring the circulation of rotavirus among children after the introduction of the RotarixTM vaccine in Goiânia, Brazil

The epidemiological features of rotavirus A (RVA) infection differ between children from developing and developed countries which could result in differences in vaccine efficacy around the world. To evaluate the impact of RotarixTM on RVA prevalence, we monitored RVA genotypes circulating in Goiânia by monitoring virus in faecal samples from children that had or had not been previously vaccinated. From February-November of 2008, 220 faecal samples were collected from children in seven day-care centres. RVA detection was performed by two methodologies and the results were confirmed by polyacrylamide gel electrophoresis. From the 220 samples, eight were RVA-positive (3.6%) and five were from children that had received either one or two doses of the vaccine. All positive samples were collected from children with diarrhoea during August and September. Genotyping of the RVA characterised five of the viral samples as genotype G2P[4] and one as G8P[4], suggesting that G2P[4] was the predominant circulating genotype in Goiânia during the study. The fact that vaccinated children were also infected by RVA suggests that the vaccine does not fully protect against infection by the G2[P4] RVA genotype.

Malaria diagnosis from pooled blood samples: comparative analysis of real-time PCR, nested PCR and immunoassay as a platform for the molecular and serological diagnosis of malaria on a large-scale

Malaria diagnoses has traditionally been made using thick blood smears, but more sensitive and faster techniques are required to process large numbers of samples in clinical and epidemiological studies and in blood donor screening. Here, we evaluated molecular and serological tools to build a screening platform for pooled samples aimed at reducing both the time and the cost of these diagnoses. Positive and negative samples were analysed in individual and pooled experiments using real-time polymerase chain reaction (PCR), nested PCR and an immunochromatographic test. For the individual tests, 46/49 samples were positive by real-time PCR, 46/49 were positive by nested PCR and 32/46 were positive by immunochromatographic test. For the assays performed using pooled samples, 13/15 samples were positive by real-time PCR and nested PCR and 11/15 were positive by immunochromatographic test. These molecular methods demonstrated sensitivity and specificity for both the individual and pooled samples. Due to the advantages of the real-time PCR, such as the fast processing and the closed system, this method should be indicated as the first choice for use in large-scale diagnosis and the nested PCR should be used for species differentiation. However, additional field isolates should be tested to confirm the results achieved using cultured parasites and the serological test should only be adopted as a complementary method for malaria diagnosis.

Reduction in morbidity and mortality from childhood diarrhoeal disease after species A rotavirus vaccine introduction in Latin America : a review

Countries in Latin America were among the first to implement routine vaccination against species A rotavirus (RVA). We evaluate data from Latin America on reductions in gastroenteritis and RVA disease burden following the introduction of RVA vaccine. Published literature was reviewed to identify case-control studies of vaccine effectiveness and population-based studies examining longitudinal trends of diarrhoeal disease reduction after RVA vaccine introduction in Latin American countries. RVA vaccine effectiveness and impact on gastroenteritis mortality and hospitalization rates and RVA hospitalization rates are described. Among middle-income Latin American countries with published data (Mexico, Brazil, El Salvador and Panama), RVA vaccine contributed to a gastroenteritis-associated mortality reduction of 22-41%, a gastroenteritis-associated hospitalization reduction of 17-51% and a RVA hospitalization reduction of 59-81% among children younger than five years of age. In Brazil and El Salvador, case-control studies demonstrated that a full RVA vaccination schedule was 76-85% effective against RVA hospitalization; a lower effectiveness of 46% was seen in Nicaragua, the only low-income country with available data. A growing body of literature offers convincing evidence of "real world" vaccine program successes in Latin American settings, which may be expanded as more countries in the region include RVA vaccine in their immunization programs.

Molecular evidence for a single taxon, Anopheles nuneztovari s.l., from two endemic malaria regions in Colombia

To elucidate the Anopheles nuneztovari s.l. taxonomic status at a microgeographic level in four malaria endemic localities from Antioquia and Córdoba, Colombia, fragments of the cytochrome oxidase subunit I (COI) and the white gene were used. The COI analysis showed low genetic differentiation with fixation index (F ST) levels between -0.02-0.137 and Nm values between 3-∞, indicating the presence of high gene flow among An. nuneztovari s.l. populations from the four localities. The COI network showed a single most common haplotype, type 1 (n = 55), present in all localities, as the likely ancestral haplotype. Analysis of the white gene showed that An. nuneztovari s.l. populations from both departments grouped with haplotypes 19 and 20, which are part of lineage 3 reported previously. The results of the present study suggest that An. nuneztovari s.l. is a single taxon in the area of the present study.

Recent advances in the study of avian malaria: an overview with an emphasis on the distribution of Plasmodium spp in Brazil

Avian malaria parasites (Plasmodium) have a worldwide distribution except for Antarctica. They are transmitted exclusively by mosquito vectors (Diptera: Culicidae) and are of particular interest to health care research due to their phylogenetic relationship with human plasmodia and their ability to cause avian malaria, which is frequently lethal in non-adapted avian hosts. However, different features of avian Plasmodium spp, including their taxonomy and aspects of their life-history traits, need to be examined in more detail. Over the last 10 years, ecologists, evolutionary biologists and wildlife researchers have recognized the importance of studying avian malaria parasites and other related haemosporidians, which are the largest group of the order Haemosporida by number of species. These studies have included understanding the ecological, behavioral and evolutionary aspects that arise in this wildlife host-parasite system. Molecular tools have provided new and exiting opportunities for such research. This review discusses several emerging topics related to the current research of avian Plasmodium spp and some related avian haemosporidians. We also summarize some important discoveries in this field and emphasize the value of using both polymerase chain reaction-based and microscopy-based methods in parallel for wildlife studies. We will focus on the genus Plasmodium, with an emphasis on the distribution and pathogenicity of these parasites in wild birds in Brazil.

Antibodies against the Plasmodium falciparum glutamate-rich protein from naturally exposed individuals living in a Brazilian malaria-endemic area can inhibit in vitro parasite growth

The glutamate-rich protein (GLURP) is an exoantigen expressed in all stages of the Plasmodium falciparum life cycle in humans. Anti-GLURP antibodies can inhibit parasite growth in the presence of monocytes via antibody-dependent cellular inhibition (ADCI), and a major parasite-inhibitory region has been found in the N-terminal R0 region of the protein. Herein, we describe the antiplasmodial activity of anti-GLURP antibodies present in the sera from individuals naturally exposed to malaria in a Brazilian malaria-endemic area. The anti-R0 antibodies showed a potent inhibitory effect on the growth of P. falciparum in vitro, both in the presence (ADCI) and absence (GI) of monocytes. The inhibitory effect on parasite growth was comparable to the effect of IgGs purified from pooled sera from hyperimmune African individuals. Interestingly, in the ADCI test, higher levels of tumour necrosis factor alpha (TNF-α) were observed in the supernatant from cultures with higher parasitemias. Our data suggest that the antibody response induced by GLURP-R0 in naturally exposed individuals may have an important role in controlling parasitemia because these antibodies are able to inhibit the in vitro growth of P. falciparum with or without the cooperation from monocytes. Our results also indicate that TNF-α may not be relevant for the inhibitory effect on P. falciparum in vitro growth.

Thrombocytopenia in malaria: who cares?

Despite not being a criterion for severe malaria, thrombocytopenia is one of the most common complications of both Plasmodium vivax and Plasmodium falciparum malaria. In a systematic review of the literature, platelet counts under 150,000/mm³ ranged from 24-94% in patients with acute malaria and this frequency was not different between the two major species that affected humans. Minor bleeding is mentioned in case reports of patients with P. vivax infection and may be explained by medullary compensation with the release of mega platelets in the peripheral circulation by megakaryocytes, thus maintaining a good primary haemostasis. The speculated mechanisms leading to thrombocytopenia are: coagulation disturbances, splenomegaly, bone marrow alterations, antibody-mediated platelet destruction, oxidative stress and the role of platelets as cofactors in triggering severe malaria. Data from experimental models are presented and, despite not being rare, there is no clear recommendation on the adequate management of this haematological complication. In most cases, a conservative approach is adopted and platelet counts usually revert to normal ranges a few days after efficacious antimalarial treatment. More studies are needed to specifically clarify if thrombocytopenia is the cause or consequence of the clinical disease spectrum.

Biomarkers for susceptibility to infection and disease severity in human malaria

Malaria remains a major infectious disease that affects millions of people. Once infected with Plasmodium parasites, a host can develop a broad range of clinical presentations, which result from complex interactions between factors derived from the host, the parasite and the environment. Intense research has focused on the identification of reliable predictors for exposure, susceptibility to infection and the development of severe complications during malaria. Although most promising markers are based on the current understanding of malaria immunopathogenesis, some are also focused more broadly on mechanisms of tissue damage and inflammation. Taken together, these markers can help optimise therapeutic strategies and reduce disease burden. Here, we review the recent advances in the identification of malarial biomarkers, focusing on those related to parasite exposure and disease susceptibility. We also discuss priorities for research in biomarkers for severe malaria.

Malaria-related anaemia: a Latin American perspective

Malaria is the most important parasitic disease worldwide, responsible for an estimated 225 million clinical cases each year. It mainly affects children, pregnant women and non-immune adults who frequently die victims of cerebral manifestations and anaemia. Although the contribution of the American continent to the global malaria burden is only around 1.2 million clinical cases annually, there are 170 million inhabitants living at risk of malaria transmission in this region. On the African continent, where Plasmodium falciparum is the most prevalent human malaria parasite, anaemia is responsible for about half of the malaria-related deaths. Conversely, in Latin America (LA), malaria-related anaemia appears to be uncommon, though there is a limited knowledge about its real prevalence. This may be partially explained by several factors, including that the overall malaria burden in LA is significantly lower than that of Africa, that Plasmodium vivax, the predominant Plasmodium species in the region, appears to display a different clinical spectrus and most likely because better health services in LA prevent the development of severe malaria cases. With the aim of contributing to the understanding of the real importance of malaria-related anaemia in LA, we discuss here a revision of the available literature on the subject and the usefulness of experimental animal models, including New World monkeys, particularly for the study of the mechanisms involved in the pathogenesis of malaria.

The prospect of eliminating malaria transmission in some regions of Brazil

This paper discusses malaria epidemiology and control in Brazil as well as the prospect of interrupting transmission in some areas of the country. The concepts of receptivity and vulnerability of an area to malaria transmission are analysed to predict where elimination might occur in a near future. Outside of the Amazon Region and in the oriental states of the Amazon, such as Tocantins, Maranhão and Mato Grosso, it is likely that malaria transmission can be eliminated with the development and sustained use of a good surveillance system.