Immune responses to malaria blood stage infection are in general defective, with the need for long-term exposure to the parasite to achieve immunity, and with the development of immunopathology states such as cerebral malaria in many cases. One of the potential reasons for the difficulty in developing protective immunity is the poor development of memory responses. In this paper, the potential association of cellular reactivity in lymphoid organs (spleen, lymph nodes and Peyer's patches) with immunity and pathology was evaluated during Plasmodium berghei ANKA infection in CBA mice.

Background: Severe anaemia is a common complication ofPlasmodium falciparummalaria in hyperendemic regions. Premature elimination of non-parasitized red blood cells (nRBC) has been considered as one mechanism involved in the genesis of severe malaria anaemia. It has been reported that apoptosis can occur in RBC and, consequently, this cell death process could contribute to anaemia. This study was performed to evaluate the susceptibility of nRBC to apoptosis in a malaria anaemia murine model.Methods: Balb/c mice were intraperitonially inoculated with 1 × 10⁶P. yoelii17XL parasitized RBC (pRBC) and, then, parasitaemia and anaemia were monitored. Apoptosis in both pRBC and nRBC was assessed during early and late phases of infection by flow cytometry using Syto 16 and annexin V-PE double staining and forward scatter measurement.Results: As expected, experimental infection of Balb/c mice withPlasmodium yoelii17XL parasites was characterized by progressive increase of parasitaemia and acute anaemia, leading to death. Flow cytometry analysis showed that a number of pRBC was in the apoptotic process. It was noteworthy that the increase of nRBC apoptosis levels occurred in the late phase of infection, when anaemia degree was notably accentuated, while no significant alteration was observed in the early phase.Conclusion: The increased levels of nRBC apoptosis herein firstly reported, in malaria infection could represent a putative mechanism worsening the severity of malarial anaemia.

Background: Endemic malaria is present in all 15 municipalities of Roraima state, Brazilian Amazonia. Knowledge of epidemiological data of specific populations can guide health policies to formulate effective strategies for integrated control of health-disease care. This study aims to ascertain when, where and who fell ill with malaria in Roraima state from 2010 to 2020. Methods: This descriptive study was based on statistical secondary surveillance data through the analysis of relationships underlying numbers of cases, hospitalizations and deaths using the Malaria Epidemiological Surveillance Information System, Mortality Information System and Hospitalization Information System. Results: From 2010 to 2020, there were 138,504 autochthonous cases, 26,158 Venezuelan imported cases, 3765 hospitalizations, and 77 deaths from malaria reported in Roraima. Annual parasitic incidence and the number of hospitalizations showed impressive changes over the period, but without significantly correlating with number of deaths. The proportion of Plasmodium falciparum infections had significant shifts throughout this study. Malaria prevalence in indigenous and mining areas has been increasing since 2014. Conclusion: The presence of miners in indigenous areas is a reality that has been contributing to the increase of malaria cases in Roraima. The need to implement health policies that also meet this contingent is reinforced.

Background: Effective treatment remains a mainstay of malaria control, but it is unfortunately strongly compromised by drug resistance, particularly in Plasmodium falciparum, the most important human malaria parasite. Although P. falciparum chemoresistance is well recognized all over the world, limited data are available on the distribution and prevalence of pfcrt and pfmdr1 haplotypes that mediate resistance to commonly used drugs and that show distinct geographic differences. Methods: Plasmodium falciparum-infected blood samples collected in 2007 at four municipalities of Luanda, Angola, were genotyped using PCR and direct DNA sequencing. Single nucleotide polymorphisms in the P. falciparum pfcrt and pfmdr1 genes were assessed and haplotype prevalences were determined. Results and Discussion: The most prevalent pfcrt haplotype was S _tctVMNT (representing amino acids at codons 72-76). This result was unexpected, since the S _tctVMNT haplotype has previously been seen mainly in parasites from South America and India. The CVIET, CVMNT and CVI NT drug-resistance haplotypes were also found, and one previously undescribed haplotype (CVMDT) was detected. Regarding pfmdr1, the most prevalent haplotype was Y EYSNVD (representing amino acids at codons 86, 130, 184, 1034, 1042, 1109 and 1246). Wild haplotypes for pfcrt and pfmdr1 were uncommon; 3% of field isolates harbored wild type pfcrt (CVMNK), whereas 21% had wild type pfmdr1 (NEYSNVD). The observed predominance of the S _tctVMNT haplotype in Angola could be a result of frequent travel between Brazil and Angola citizens in the context of selective pressure of heavy CQ use. Conclusions: The high prevalence of the pfcrt S VMNT haplotype and the pfmdr1 86Y mutation confirm high-level chloroquine resistance and might suggest reduced efficacy of amodiaquine in Angola. Further studies must be encouraged to examine the in vitro sensitivity of pfcrt S VMNT parasites to artesunate and amodiaquine for better conclusive data.

Although malaria cases have substantially decreased in Southeast Brazil, a significant increase in the number of Plasmodium vivax-like autochthonous human cases has been reported in remote areas of the Atlantic Forest in the past few decades in Rio de Janeiro (RJ) state, including an outbreak during 2015–2016. The singular clinical and epidemiological aspects in several human cases, and collectively with molecular and genetic data, revealed that they were due to the non-human primate (NHP) parasite Plasmodium simium; however, the understanding of the autochthonous malarial epidemiology in Southeast Brazil can only be acquired by assessing the circulation of NHP Plasmodium in the foci and determining its hosts. A large sampling effort was carried out in the Atlantic forest of RJ and its bordering states (Minas Gerais, São Paulo, Espírito Santo) for collecting and examining free-living NHPs. Blood and/or viscera were analyzed for Plasmodium infections via molecular and microscopic techniques. In total, 146 NHPs of six species, from 30 counties in four states, were tested, of which majority were collected from RJ. Howler monkeys (Alouatta clamitans) were the only species found infected. In RJ, 26% of these monkeys tested positive, of which 17% were found to be infected with P. simium. Importantly, specific single nucleotide polymorphisms–the only available genetic markers that differentiate P. simium from P. vivax–were detected in all P. simium infected A. clamitans despite their geographical origin of malarial foci. Interestingly, 71% of P. simium infected NHPs were from the coastal slope of a mountain chain (Serra do Mar), where majority of the human cases were found. Plasmodium brasilianum/malariae was initially detected in 14% and 25% free-living howler monkeys in RJ and in the Espírito Santo (ES) state, respectively. Moreover, the malarial pigment was detected in the spleen fragments of 50% of a subsample comprising dead howler monkeys in both RJ and ES. All NHPs were negative for Plasmodium falciparum. Our data indicate that howler monkeys act as the main reservoir for the Atlantic forest human malarial parasites in RJ and other sites in Southeast Brazil and reinforce its zoonotic characteristics. The present work comprises an unprecedented capture effort and large-scale field survey of Plasmodium species in non-human primates (NHPs) in RJ, a state recording three-decade history of autochthonous human cases of benign tertian malaria lacking epidemiological clarification of their origin. This is the first study to describe the infection rates by Plasmodium spp. in free-living NHPs in RJ, thereby matching the spatial distribution of P. simium in NHP with that of the local human cases of benign tertian malaria occurring due to this parasite. This study confirmed howler monkeys as the only reservoir of this zoonotic malarial parasite in RJ and reported that specific single nucleotide polymorphisms were present in all P. simium infected howler monkeys, despite their geographical origin of malarial foci. Moreover, this is the first study to record P. brasilianum/malariae in free-living NHPs from RJ, and to illustrate their widespread distribution in this state. Collectively, these findings help us in evaluating the simian malaria parasites in the Atlantic Forests and in assessing the zoonotic characteristics of autochthonous human malaria in Rio de Janeiro, thus providing assistance in acclimatizing surveillance and control.