Naturally acquired immunity to Plasmodium pitheci in Bornean orangutans (Pongo pygmaeus)

Naturally acquired immunity to the different types of malaria in humans occurs in areas of endemic transmission and results in asymptomatic infection of peripheral blood. The current study examined the possibility of naturally acquired immunity in Bornean orangutans, Pongo pygmaeus, exposed to endemic Plasmodium pitheci malaria. A total of 2140 peripheral blood samples were collected between January 2017 and December 2022 from a cohort of 135 orangutans housed at a natural forested Rescue and Rehabilitation Centre in West Kalimantan, Indonesia. Each individual was observed for an average of 4.3 years during the study period. Blood samples were examined by microscopy and polymerase chain reaction for the presence of plasmodial parasites. Infection rates and parasitaemia levels were measured among age groups and all 20 documented clinical malaria cases were reviewed to estimate the incidence of illness and risk ratios among age groups. A case group of all 17 individuals that had experienced clinical malaria and a control group of 34 individuals having an event of >2000 parasites μL−1 blood but with no outward or clinical sign of illness were studied. Immature orangutans had higher-grade and more frequent parasitaemia events, but mature individuals were more likely to suffer from clinical malaria than juveniles. The case orangutans having patent clinical malaria were 256 times more likely to have had no parasitaemia event in the prior year relative to asymptomatic control orangutans. The findings are consistent with rapidly acquired immunity to P. pitheci illness among orangutans that wanes without re-exposure to the pathogen.

RNAscope in situ hybridization reveals microvascular sequestration of Plasmodium relictum pSGS1 blood stages but absence of exo-erythrocytic dormant stages during latent infection of Serinus canaria

BACKGROUND

Birds chronically infected with avian malaria parasites often show relapses of parasitaemia after latent stages marked by absence of parasites in the peripheral circulation. These relapses are assumed to result from the activation of dormant exo-erythrocytic stages produced during secondary (post-erythrocytic) merogony of avian Plasmodium spp. Yet, there is no morphological proof of persistent or dormant tissue stages in the avian host during latent infections. This study investigated persistence of Plasmodium relictum pSGS1 in birds with latent infections during winter, with the goal to detect presumed persisting tissue stages using a highly sensitive RNAscope® in situ hybridization technology.

METHODS

Fourteen domestic canaries were infected with P. relictum pSGS1 by blood-inoculation in spring, and blood films examined during the first 4 months post infection, and during winter and spring of the following year. After parasitaemia was no longer detectable, half of the birds were dissected, and tissue samples investigated for persisting tissue stages using RNAscope ISH and histology. The remaining birds were blood-checked and dissected after re-appearance of parasitaemia, and their tissues equally examined.

RESULTS

Systematic examination of tissues showed no exo-erythrocytic stages in birds exhibiting latent infections by blood-film microscopy, indicating absence of dormant tissue stages in P. relictum pSGS1-infected canaries. Instead, RNAscope ISH revealed rare P. relictum blood stages in capillaries of various tissues and organs, demonstrating persistence of the parasites in the microvasculature. Birds examined after re-appearance of parasitemia showed higher numbers of P. relictum blood stages in both capillaries and larger blood vessels, indicating replication during early spring and re-appearance in the peripheral circulation.

CONCLUSIONS

The findings suggest that persistence of P. relictum pSGS1 during latent infection is mediated by continuous low-level erythrocytic merogony and possibly tissue sequestration of infected blood cells. Re-appearance of parasitaemia in spring seems to result from increased erythrocytic merogony, therefore representing recrudescence and not relapse in blood-inoculated canaries. Further, the study highlights strengths and limitations of the RNAscope ISH technology for the detection of rare parasite stages in tissues, providing directions for future research on persistence and tissue sequestration of avian malaria and related haemosporidian parasites.

Mercury bioaccumulation and Hepatozoon spp. infections in two syntopic watersnakes in South Carolina

Mercury (Hg) is a ubiquitous environmental contaminant known to bioaccumulate in biota and biomagnify in food webs. Parasites occur in nearly every ecosystem and often interact in complex ways with other stressors that their hosts experience. Hepatozoon spp. are intraerythrocytic parasites common in snakes. The Florida green watersnake (Nerodia floridana) and the banded watersnake (Nerodia fasciata) occur syntopically in certain aquatic habitats in the Southeastern United States. The purpose of this study was to investigate relationships among total mercury (THg) concentrations, body size, species, habitat type and prevalence and parasitemia of Hepatozoon spp. infections in snakes. In the present study, we sampled N. floridana and N. fasciata from former nuclear cooling reservoirs and isolated wetlands of the Savannah River Site in South Carolina. We used snake tail clips to quantify THg and collected blood samples for hemoparasite counts. Our results indicate a significant, positive relationship between THg and snake body size in N. floridana and N. fasciata in both habitats. Average THg was significantly higher for N. fasciata compared to N. floridana in bays (0.22 ± 0.02 and 0.08 ± 0.006 mg/kg, respectively; p < 0.01), but not in reservoirs (0.17 ± 0.02 and 0.17 ± 0.03 mg/kg, respectively; p = 0.29). Sex did not appear to be related to THg concentration or Hepatozoon spp. infections in either species. We found no association between Hg and Hepatozoon spp. prevalence or parasitemia; however, our results suggest that species and habitat type play a role in susceptibility to Hepatozoon spp. infection.

Q586B2 is a crucial virulence factor during the early stages of Trypanosoma brucei infection that is conserved amongst trypanosomatids

Human African trypanosomiasis or sleeping sickness, caused by the protozoan parasite Trypanosoma brucei, is characterized by the manipulation of the host's immune response to ensure parasite invasion and persistence. Uncovering key molecules that support parasite establishment is a prerequisite to interfere with this process. We identified Q586B2 as a T. brucei protein that induces IL-10 in myeloid cells, which promotes parasite infection invasiveness. Q586B2 is expressed during all T. brucei life stages and is conserved in all Trypanosomatidae. Deleting the Q586B2-encoding Tb927.6.4140 gene in T. brucei results in a decreased peak parasitemia and prolonged survival, without affecting parasite fitness in vitro, yet promoting short stumpy differentiation in vivo. Accordingly, neutralization of Q586B2 with newly generated nanobodies could hamper myeloid-derived IL-10 production and reduce parasitemia. In addition, immunization with Q586B2 delays mortality upon a challenge with various trypanosomes, including Trypanosoma cruzi. Collectively, we uncovered a conserved protein playing an important regulatory role in Trypanosomatid infection establishment.

Multiple myeloma and Chagas disease: qPCR as a marker for preemptive antiparasitic therapy: a case reports series and review

Multiple myeloma (MM) associated with Chagas disease is rarely described. This disease and its therapy suppress T cell and macrophage functions and increase regulatory T cell function, allowing the increase of parasitemia and the risk of Chagas Disease Reactivation (CDR). We aimed to analyze the role of conventional (cPCR) and quantitative Polymerase Chain Reaction (qPCR) for prospective monitoring of T. cruzi parasitemia, searching for markers of preemptive antiparasitic therapy in MM patients with Chagas disease. Moreover, we investigated the incidence and management of hematological diseases and CDR both inside and outside the transplant setting in the MEDLINE database. We found 293 studies and included 31 of them. Around 1.9-2.0% of patients with Chagas disease were reported in patients undergoing Stem Cell Transplantation. One case of CDR was described in eight cases of MM and Chagas disease. We monitored nine MM and Chagas disease patients, seven under Autologous Stem Cell Transplantation (ASCT), during 44.56±32.10 months (mean±SD) using parasitological methods, cPCR, and qPCR. From these patients, three had parasitemia. In the first, up to 256 par Eq/mL were detected, starting from 28 months after ASCT. The second patient dropped out and died soon after the detection of 161.0 par Eq/mL. The third patient had a positive blood culture. Benznidazole induced fast negativity in two cases; followed by notably lower levels in one of them. Increased T. cruzi parasitemia was related to the severity of the underlying disease. We recommend parasitemia monitoring by qPCR for early introduction of preemptive antiparasitic therapy to avoid CDR.

Quantitative PCR as a marker for preemptive therapy and its role in therapeutic control in Trypanosoma cruzi/HIV coinfection

BACKGROUND

Trypanosoma cruzi and HIV coinfection can evolve with depression of cellular immunity and increased parasitemia. We applied quantitative PCR (qPCR) as a marker for preemptive antiparasitic treatment to avoid fatal Chagas disease reactivation and analyzed the outcome of treated cases.

METHODOLOGY

This mixed cross-sectional and longitudinal study included 171 Chagas disease patients, 60 coinfected with HIV. Of these 60 patients, ten showed Chagas disease reactivation, confirmed by parasites identified in the blood, cerebrospinal fluid, or tissues, 12 exhibited high parasitemia without reactivation, and 38 had low parasitemia and no reactivation.

RESULTS

We showed, for the first time, the success of the timely introduction of benznidazole in the non-reactivated group with high levels of parasitemia detected by qPCR and the absence of parasites in reactivated cases with at least 58 days of benznidazole. All HIV+ patients with or without reactivation had a 4.0-5.1 higher chance of having parasitemia than HIV seronegative cases. A positive correlation was found between parasites and viral loads. Remarkably, treated T. cruzi/HIV-coinfected patients had 77.3% conversion from positive to negative parasitemia compared to 19.1% of untreated patients. Additionally, untreated patients showed ~13.6 times higher Odds Ratio of having positive parasitemia in the follow-up period compared with treated patients. Treated and untreated patients showed no differences regarding the evolution of Chagas disease. The main factors associated with all-cause mortality were higher parasitemia, lower CD4 counts/μL, higher viral load, and absence of antiretroviral therapy.

CONCLUSION

We recommend qPCR prospective monitoring of T. cruzi parasitemia in HIV+ coinfected patients and point out the value of pre-emptive therapy for those with high parasitemia. In parallel, early antiretroviral therapy introduction is advisable, aiming at viral load control, immune response restoration, and increasing survival. We also suggest an early antiparasitic treatment for all coinfected patients, followed by effectiveness analysis alongside antiretroviral therapy.

Linking avian malaria parasitemia estimates from quantitative PCR and microscopy reveals new infection patterns in Hawai'i

Plasmodium parasites infect thousands of species and provide an exceptional system for studying host-pathogen dynamics, especially for multi-host pathogens. However, understanding these interactions requires an accurate assay of infection. Assessing Plasmodium infections using microscopy on blood smears often misses infections with low parasitemias (the fractions of cells infected), and biases in malaria prevalence estimates will differ among hosts that differ in mean parasitemias. We examined Plasmodium relictum infection and parasitemia using both microscopy of blood smears and quantitative polymerase chain reaction (qPCR) on 299 samples from multiple bird species in Hawai'i and fit models to predict parasitemias from qPCR cycle threshold (Ct) values. We used these models to quantify the extent to which microscopy underestimated infection prevalence and to more accurately estimate infection patterns for each species for a large historical study done by microscopy. We found that most qPCR-positive wild-caught birds in Hawaii had low parasitemias (Ct scores ≥35), which were rarely detected by microscopy. The fraction of infections missed by microscopy differed substantially among eight species due to differences in species' parasitemia levels. Infection prevalence was likely 4-5-fold higher than previous microscopy estimates for three introduced species, including Zosterops japonicus, Hawaii's most abundant forest bird, which had low average parasitemias. In contrast, prevalence was likely only 1.5-2.3-fold higher than previous estimates for Himatione sanguinea and Chlorodrepanis virens, two native species with high average parasitemias. Our results indicate that relative patterns of infection among species differ substantially from those observed in previous microscopy studies, and that differences depend on variation in parasitemias among species. Although microscopy of blood smears is useful for estimating the frequency of different Plasmodium stages and host attributes, more sensitive quantitative methods, including qPCR, are needed to accurately estimate and compare infection prevalence among host species.

Malaria Infection in Patients with Sickle Cell Disease in Nigeria: Association with Markers of Hyposplenism

Malaria is considered an important cause of morbidity and mortality among people living with sickle cell disease (SCD). This has partly been attributed to the loss of splenic function that occurs early in the disease process. We conducted a cross-sectional study and determined the frequency of malaria infection among SCD patients and explored the association with spleen's presence on ultrasonography and spleen function assessed using the frequency of Howell-Jolly bodies (HJBs). A total of 395 participants consisting of 119 acutely-ill SCD patients, 168 steady-state SCD controls, and 108 healthy non-SCD controls were studied. The prevalence of Plasmodium falciparum parasitemia was 51.3% in acutely-ill SCD patients, 31.7% in steady-state SCD controls, and 11.0% in the healthy non-SCD controls; however, the mean parasite density was significantly higher in the non-SCD controls compared to both SCD groups (p = 0.0001). Among the acutely-ill SCD patients, the prevalence of clinical malaria and severe malaria anemia were highest in children <5 years of age. The prevalence of parasitemia (p = 0.540) and parasite density (p = 0.975) showed no association with spleen presence or absence on ultrasonography. Similarly, the frequency of HJB red cells was not associated with the presence of parasitemia (p = 0.183). Our study highlights the frequency and role of malaria infection in acutely-ill SCD patients, especially in those younger than five years. Although we have found no evidence of an increased risk of malaria parasitemia or parasite density with markers of hyposplenism, the role played by an underlying immunity to malaria among SCD patients in malaria-endemic region is not clear and needs further studies.

Changes in hypothalamic-pituitary-adrenal axis function, immunity, and glucose during acute Plasmodium relictum infection in house sparrows (Passer domesticus)

Hosts of the same species vary in physiological responses to the same parasite, and some groups of individuals can disproportionately affect disease dynamics; however, the underlying pathophysiology of host-parasite interactions is poorly understood in wildlife. We tested the hypothesis that the hypothalamic-pituitary-adrenal (HPA) axis mediates host resistance and tolerance to avian malaria during the acute phase of infection by evaluating whether individual variation in circulating glucocorticoids predicted resistance to avian malaria in a songbird. We experimentally inoculated wild-caught house sparrows (Passer domesticus) with naturally sourced Plasmodium relictum and quantified baseline and restraint-induced circulating corticosterone, negative feedback ability, cellular and humoral immune function, and baseline and restraint-induced glycemia, prior to and during acute malaria infection. During peak parasitemia, we also evaluated the expression of several liver cytokines that are established pathological hallmarks of malaria in mammals: two pro-inflammatory (IFN-γ and TNF-α) and two anti-inflammatory (IL-10 and TGF-β). Although most of the host metrics we evaluated were not correlated with host resistance or tolerance to avian malaria, this experiment revealed novel relationships between malarial parasites and the avian immune system that further our understanding of the pathology of malaria infection in birds. Specifically, we found that: (1) TNF-α liver expression was positively correlated with parasitemia; (2) sparrows exhibited an anti-inflammatory profile during malaria infection; and (3) IFN-γ and circulating glucose were associated with several immune parameters, but only in infected sparrows. We also found that, during the acute phase of infection, sparrows increased the strength of corticosterone negative feedback at the level of the pituitary. In the context of our results, we discuss future methodological considerations and aspects of host physiology that may confer resistance to avian malaria, which can help inform conservation and rehabilitation strategies for avifauna at risk.

Differential recovery ability from infections by two blood parasite genera in males of a Mediterranean lacertid lizard after an experimental translocation

Different blood parasites can co-infect natural populations of lizards. However, our knowledge of the host's ability to recover from them (i.e., significantly reduce parasitemia levels) is scarce. This has interest from an ecological immunology perspective. Herein, we investigate the host recovery ability in males of the lizard Psammodromus algirus infected by parasite genera Schellackia and Karyolysus. The role of lizard hosts is dissimilar in the life cycle of these two parasites, and thus different immune control of the infections is expected by the vertebrate host. As Schellackia performs both sexual and asexual reproduction cycles in lizards, we expect a better immune control by its vertebrate hosts. On the contrary, Karyolysus performs sexual reproductive cycles in vectors, hence we expect lower immune control by the lizards. We carried out a reciprocal translocation experiment during the lizards' mating season to evaluate both parasitemia and leukocyte profiles in male lizards, being one of the sampling plots close to a road with moderate traffic. These circumstances provide a combination of extrinsic (environmental stress) and intrinsic factors (reproductive vs. immune trade-offs) that may influence host's recovery ability. We recaptured 33% of the lizards, with a similar proportion in control and translocated groups. Karyolysus infected 92.3% and Schellackia 38.5% of these lizards. Hosts demonstrated ability to significantly reduce parasitemia of Schellackia but not of Karyolysus. This suggests, in line with our predictions, a differential immune relationship of lizards with these parasites, at time that supports that parasites with different phylogenetic origins should be analyzed separately in investigations of their effects on hosts. Furthermore, lizards close to the road underwent a stronger upregulation of lymphocytes and monocytes when translocated far from the road, suggesting a putative greater exposure to pathogens in the latter area.

[Investigation of the Efficacy of Cinnamaldehyde, Cannabidiol and Eravacycline in a Malaria Model]

In this study, it was aimed to investigate the antimalarial activity of cinnamaldehyde (CIN) and cannabidiol (CBD) which have shown various biological activities such as potent antimicrobial activity and eravacycline (ERA), a new generation tetracycline derivative, in an in vivo malaria model. The cytotoxic activities of the active substances were determined by the MTT method against L929 mouse fibroblasts and their antimalarial activity were determined by the four-day test in an in vivo mouse model. In this study, five groups were formed: the CIN group, the CBD group, the ERA group, the chloroquine group (CQ) and the untreated group (TAG). 2.5 x 107 parasites/mL of P.berghei-infected erythrocyte suspension was administered IP to all mice. The determined doses of active substances were given to the mice by oral gavage in accordance with the four-day test and the parasitemia status in the mice was controlled for 21 days with smear preparations made from the blood taken from the tail end of the mice. The IC50 values, which express the cytotoxic activity values of the active substances were determined as 27.55 μg/mL, 16.40 μM and 48.82 μg/mL for CIN, CBD and ERA, respectively. The mean parasitemia rate in untreated mice was 33% on day nine and all mice died on day 11. On the ninth day, when compared with the TAG group, no parasites were observed in the CIN group, while the average parasitemia was 0.08% in the CBD group and 17.8% in the ERA group. Compared to the mice in the TAG group, the life expectancy of the other groups was prolonged by eight days in the CIN group, 12 days in the CBD group and eight days in the ERA group. It has been determined that all three active subtances tested in this study suppressed the development of Plasmodium parasites in an in vivo mouse model and prolonged the life span of the mice. It is thought that the strong antimalarial activity of CIN and CBD shown in the study and the possible positive effect of ERA on the clinical course can be improved by combining them with the existing and potential antimalarial molecules.

Antiplasmodial Activity Evaluation of a Bestatin-Related Aminopeptidase Inhibitor, Phebestin

The increasing burden and spread of resistant malaria parasites remains an immense burden to public health. These factors have driven the demand to search for a new therapeutic agent. From our screening, phebestin stood out with nanomolar efficacy against Plasmodium falciparum 3D7. Phebestin was initially identified as an aminopeptidase N inhibitor. Phebestin inhibited the in vitro multiplication of the P. falciparum 3D7 (chloroquine-sensitive) and K1 (chloroquine-resistant) strains at IC50 values of 157.90 ± 6.26 nM and 268.17 ± 67.59 nM, respectively. Furthermore, phebestin exhibited no cytotoxic against human foreskin fibroblast cells at 2.5 mM. In the stage-specific assay, phebestin inhibited all parasite stages at 100 and 10-fold its IC50 concentration. Using 72-h in vitro exposure of phebestin at concentrations of 1 μM on P. falciparum 3D7 distorted the parasite morphology, showed dying signs, shrank, and prevented reinvasion of RBCs, even after the compound was washed from the culture. An in silico study found that phebestin binds to P. falciparum M1 alanyl aminopeptidase (PfM1AAP) and M17 leucyl aminopeptidase (PfM17LAP), as observed for bestatin. In vivo evaluation using P. yoelii 17XNL-infected mice with administrations of 20 mg/kg phebestin, once daily for 7 days, resulted in significantly lower parasitemia peaks in the phebestin-treated group (19.53%) than in the untreated group (29.55%). At the same dose and treatment, P. berghei ANKA-infected mice showed reduced parasitemia levels and improved survival compared to untreated mice. These results indicate that phebestin is a promising candidate for development as a potential therapeutic agent against malaria.

Neurologic Complications of Babesiosis, United States, 2011-2021

Babesiosis is a globally distributed parasitic infection caused by intraerythrocytic protozoa. The full spectrum of neurologic symptoms, the underlying neuropathophysiology, and neurologic risk factors are poorly understood. Our study sought to describe the type and frequency of neurologic complications of babesiosis in a group of hospitalized patients and assess risk factors that might predispose patients to neurologic complications. We reviewed medical records of adult patients who were admitted to Yale-New Haven Hospital, New Haven, Connecticut, USA, during January 2011-October 2021 with laboratory-confirmed babesiosis. More than half of the 163 patients experienced >1 neurologic symptoms during their hospital admissions. The most frequent symptoms were headache, confusion/delirium, and impaired consciousness. Neurologic symptoms were associated with high-grade parasitemia, renal failure, and history of diabetes mellitus. Clinicians working in endemic areas should recognize the range of symptoms associated with babesiosis, including neurologic.

Trypanosoma cruzi: Does the intake of nanoencapsulated benznidazole control acute infections?

Chagas Disease (CD) affects around eight million people worldwide. It is considered a neglected disease that presents few treatment options with efficacy only in the acute phase. Nanoparticles have many positive qualities for treating parasite infections and may be effectively and widely employed in clinical medicine. This research aimed to evaluate the nanoencapsulated benznidazole treatment in animals experimentally infected with Trypanosoma cruzi. To analyze the treatment efficacy, we evaluated survival during thirty days, parasitemia, genotoxicity, and heart and liver histopathology. Thirty-five female Swiss mice were organized into seven groups characterizing a dose curve: A - Negative control (uninfected animals), B - Positive control (infected animals), C - Benznidazole (BNZ) 100 mg/kg (infected animals), D - 5 mg/kg Benznidazole nanocapsules (NBNZ) (infected animals), E - 10 mg/kg Benznidazole nanocapsules (infected animals), F - 15 mg/kg Benznidazole nanocapsules (infected animals), G - 20 mg/kg Benznidazole nanocapsules (infected animals). The animals were infected with the Y strain of T. cruzi intraperitoneally. The treatment was administered for eight days by oral gavage. It was possible to observe that the treatment with the highest NBNZ dose presented efficacy similar to the standard benznidazole drug. The 20 mg/kg NBNZ dose was able to reduce parasitemia, increase survival, and drastically reduce heart and liver tissue damage compared to the 100 mg/kg BNZ dose. Moreover, it showed a lower DNA damage index than the BNZ treatment. In conclusion, the nanoencapsulation of BNZ promotes an improvement in parasite proliferation control with a five times smaller dose relative to the standard dose of free BNZ, thus demonstrating to be a potential innovative therapy for CD.

Transmission efficiency of Plasmodium vivax at low parasitaemia

BACKGROUND

Plasmodium vivax is responsible for much of malaria outside Africa. Although most P. vivax infections in endemic areas are asymptomatic and have low parasite densities, they are considered a potentially important source of transmission. Several studies have demonstrated that asymptomatic P. vivax carriers can transmit the parasite to mosquitoes, but the efficiency has not been well quantified. The aim of this study is to determine the relationship between parasite density and mosquito infectivity, particularly at low parasitaemia.

METHODS

Membrane feeding assays were performed using serial dilutions of P. vivax-infected blood to define the relationship between parasitaemia and mosquito infectivity.

RESULTS

The infection rate (oocyst prevalence) and intensity (oocyst load) were positively correlated with the parasite density in the blood. There was a broad case-to-case variation in parasite infectivity. The geometric mean parasite density yielding a 10% mosquito infection rate was 33 (CI 95 9-120) parasites/µl or 4 (CI 95 1-17) gametocytes/µl. The geometric mean parasite density yielding a 50% mosquito infection rate was 146 (CI 95 36-586) parasites/µl or 13 (CI 95 3-49) gametocytes/µl.

CONCLUSION

This study quantified the ability of P. vivax to infect Anopheles dirus at over a broad range of parasite densities. It provides important information about parasite infectivity at low parasitaemia common among asymptomatic P. vivax carriers.

Human Trypanosoma cruzi chronic infection leads to individual level steady-state parasitemia: Implications for drug-trial optimization in Chagas disease

Currently available drugs against Trypanosoma cruzi infection, which causes 12000 deaths annually, have limitations in their efficacy, safety and tolerability. The evaluation of therapeutic responses to available and new compounds is based on parasite detection in the bloodstream but remains challenging because a substantial proportion of infected individuals have undetectable parasitemia even when using diagnostic tools with the highest accuracy. We characterize parasite dynamics which might impact drug efficacy assessments in chronic Chagas by analyzing pre- and post-treatment quantitative-PCR data obtained from blood samples collected regularly over a year. We show that parasitemia remains at a steady-state independently of the diagnostic sensitivity. This steady-state can be probabilistically quantified and robustly predicted at an individual level. Furthermore, individuals can be assigned to categories with distinct parasitological status, allowing a more detailed evaluation of the efficacy outcomes and adjustment for potential biases. Our analysis improves understanding of parasite dynamics and provides a novel background for optimizing future drug efficacy trials in Chagas disease. Trial Registration: original trial registered with ClinicalTrials.gov, number NCT01489228.

Prevalence and associated risk factors of malaria among febrile under-five children visiting health facilities in Ziquala district, Northeast Ethiopia: A multicenter cross-sectional study

BACKGROUND

Malaria is among the leading causes of mortality and morbidity among under five children in developing countries. Ethiopia has set targets for controlling and eliminating malaria through at-risk group interventions. However, the disease remains a serious public health concern in endemic areas like in Wollo, Northeast Ethiopia. Therefore, this study aimed to determine malaria prevalence, risk factors and parasite density among under five children in Ziquala district.

METHOD

A facility-based cross-sectional study was conducted in Ziquala hospital, and Tsitsika, Mishra and Hamusit health centers in Ziquala district, Northeast Ethiopia, from January 2022 to April 2022. The study enrolled a total of 633 under five children using a systematic sampling technique. A capillary blood sample was collected from each child to prepared thin and thick blood smears. Smears were then stained with 10% Giemsa and examined under light microscope. A pretested structured questionnaire was used to collect on socio-demographic data, parental/caregiver knowledge, and malaria determining factors. Bivariable and multivariable logistic regression analysis was done to identify factors associated with malaria.

RESULT

The overall prevalence of malaria among children visiting Ziquala district health institutions was 24.6% (156/633). Plasmodium falciparum, P. vivax, and mixed infection (both species) accounted for 57.1%, 38.5%, and 4.5% of the cases, respectively. Regarding to parasite load, moderate parasitemia was the most common, followed by low and high parasitemia with the proportion of 53.8%, 31.4% and 14.7% parasite density, respectively. Malaria infection was linked to irregular utilization of insecticide-treated bed nets (AOR = 5.042; 95% CI: 2.321-10.949), staying outside at night (AOR = 2.109; 95% CI: 1.066-4.173), and parents not receiving malaria health education in the past six months (AOR = 4.858; 95% CI: 2.371-9.956).

CONCLUSION

Malaria was prevalent among children under the age of five enrolled in the study. The local government should focus on regular insecticide treated net utilization, reducing the risk of mosquito bites while sleeping outdoors at night and increasing public understanding of malaria prevention and control through health education would also help to minimize the burden of malaria.

Monocyte epigenetics and innate immunity to malaria: yet another level of complexity?

Children under the age of 5 years living in areas of moderate to high malaria transmission are highly susceptible to clinical malaria with fever that prompts treatment of blood stage infection with anti-malarial drugs. In contrast, older school age children frequently experience subclinical malaria, i.e. chronic Plasmodium falciparum parasitemia without fever or other clinical symptoms. The role of innate immune cells in regulating inflammation at a level that is sufficient to control the parasite biomass, while at the same time maintaining a disease-tolerant clinical phenotype, i.e., subclinical malaria, is not well understood. Recent studies suggest that host epigenetic mechanisms underlie the innate immune homeostasis associated with subclinical malaria. This Current Opinion article presents evidence supporting the notion that modifications of the host monocyte/macrophage epigenome regulate innate immune functions pertinent to subclinical malaria.

Testosterone induces sexual dimorphism during infection with Plasmodium berghei ANKA

Malaria is the most lethal parasitic disease worldwide; men exhibit higher mortality and more severe symptomatology than women; however, in most studies of immune response in malaria, sex is not considered a variable. Sex hormones 17β-oestradiol and testosterone are responsible for the main physiological differences between sexes. When interacting with their receptors on different immune cells, they modify the expression of genes that modulate cell proliferation, differentiation, and synthesis of cytokines. The immunosuppressive activity of testosterone is well accepted; however, its participation in the sexual dimorphism of the immune response to malaria has not been studied. In this work, we analysed whether altering the concentration of testosterone, through increasing the concentration of this hormone for exogenous administration for three weeks, or gonadectomy before infection with Plasmodium berghei ANKA affects different cells of the immune response necessary for parasite clearance. We also assessed the concentration of pro-and anti-inflammatory cytokines in male and female CBA/Ca mice infected or not with the parasite. Our results show that testosterone changes affect females more than males, resulting in sex-associated patterns. Testosterone administration increased parasitaemia in intact males while reducing it in intact females leading to a dimorphic pattern. In addition, gonadectomy increased parasitaemia in both sexes. Moreover, testosterone administration prevented both weight loss caused by the infection in females and hypothermia in gonadectomized mice of both sexes. Boosting testosterone concentration increased CD3+ and CD8+ populations but decreased the B220+ cells exclusively in females. Additionally, testosterone reduced IFN-γ concentration and increased IL-6 levels only in females, while in males, testosterone increased the number of NK cells. Finally, gonadectomy decreased TNF-α concentration in both sexes. Our results demonstrate that testosterone induces different patterns depending on sex and testosterone concentration. The results of this work contribute to understanding the impact of modifying testosterone concentration on the immune response specific against Plasmodium and the participation of this hormone in sexual dimorphism in malaria.

Longitudinal impact of asymptomatic malaria/HIV-1 co-infection on Plasmodium falciparum gametocyte transcript expression and transmission to Anopheles mosquitoes

Despite significant developments towards malaria reduction, parasite transmission in the common context of HIV-1 co-infection and treatment for one or both infections has not been fully characterized. This is particularly important given that HIV-1 and malaria chemotherapies have the potential to alter gametocyte burden and mosquito infectivity. In this study, we examined 782 blood samples collected from a longitudinal cohort of 300 volunteers with asymptomatic parasitemia seeking HIV testing or treatment in the endemic region of Kisumu, Kenya, to define the impacts of HIV-1-malaria co-infection, antiretroviral therapy (ART) plus trimethoprim-sulfamethoxazole (TS) and the antimalarials artemether/lumefantrine (AL) on Plasmodium falciparum gametocyte transcript prevalence and parasite transmission to the African malaria mosquito Anopheles gambiae. Volunteers were assigned to three distinct HIV-1 groups: HIV-1 positive on treatment, HIV-1 positive newly diagnosed, and HIV-1 negative. Volunteers were monitored monthly over the course of six months. Using our highly sensitive digital droplet PCR (ddPCR) assay of three gametocyte specific transcript markers, we detected gametocyte transcripts in 51.1% of 18S positive volunteers across all study groups and time points. After correcting for multiple comparisons, the factors of HIV-1 status, time, CD4+ T-cell levels and hematocrit were not predictive of gametocyte prevalence or transmission. However, among those volunteers who were newly diagnosed with HIV-1 and malaria positive by rapid diagnostic test (RDT) at enrollment, the initiation of ART/TS and AL treatment was associated with a significant reduction in gametocyte transcript prevalence in the subsequent month when compared to HIV-1 negative volunteers treated with AL. To assess gametocyte transmissibility, volunteer blood samples were used in standard membrane feeding assays (SFMA) with laboratory-reared A. gambiae, with evidence of transmission confirmed by at least one of 25 dissected mosquitoes per sample positive for at least one midgut oocyst. HIV-1 status, CD4+ T-cell levels and hematocrit were not significantly associated with successful transmission to A. gambiae. Analysis of SMFA blood samples revealed that 50% of transmission-positive blood samples failed to test positive by Plasmodium-specific 18S ribosomal RNA quantitative PCR (qPCR) and 35% failed to test positive for any gametocyte specific transcript marker by droplet digital (ddPCR), documenting that transmission occurred in the absence of molecular parasite/gametocyte detection. Overall, these findings highlight the complexity of HIV-1 malaria co-infection and the need to further define the unpredictable role of asymptomatic parasitemia in transmission to mosquitoes.

Biological characteristics of the Trypanosoma cruzi Arequipa strain make it a good model for Chagas disease drug discovery

Trypanosoma cruzi, the causative agent of Chagas disease (CD), is a genuine parasite with tremendous genetic diversity and a complex life cycle. Scientists have studied this disease for more than 100 years, and CD drug discovery has been a mainstay due to the absence of an effective treatment. Technical advances in several areas have contributed to a better understanding of the complex biology and life cycle of this parasite, with the aim of designing the ideal profile of both drug and therapeutic options to treat CD. Here, we present the T. cruzi Arequipa strain (MHOM/Pe/2011/Arequipa) as an interesting model for CD drug discovery. We characterized acute-phase parasitaemia and chronic-phase tropism in BALB/c mice and determined the in vitro and in vivo benznidazole susceptibility profile of the different morphological forms of this strain. The tropism of this strain makes it an interesting model for the screening of new compounds with a potential anti-Chagas profile for the treatment of this disease.

Action mechanisms of metallic compounds on Plasmodium spp

BACKGROUND

Malaria is a parasitic disease with the highest morbidity and mortality worldwide. Unfortunately, during the last decades, the causal agent, Plasmodium spp., has developed resistance to chloroquine and artemisinin. For this reason, metallic compounds have been proposed as an optional treatment since they have shown a potential antimalarial effect with diverse action mechanisms in the parasite and the host.

OBJECTIVE

To show the possible targets of metallic compounds in Plasmodium spp.

CONCLUSION

The metallic compounds are an option attractive to treatment for the malaria, for its low cost and its great activity to reduce parasitemia; however is necessary more studies principally in vivo in order to know the interactions that it can have in an experimental model.

Low-Dose Subcutaneous or Intravenous Monoclonal Antibody to Prevent Malaria

BACKGROUND

New approaches for the prevention and elimination of malaria, a leading cause of illness and death among infants and young children globally, are needed.

METHODS

We conducted a phase 1 clinical trial to assess the safety and pharmacokinetics of L9LS, a next-generation antimalarial monoclonal antibody, and its protective efficacy against controlled human malaria infection in healthy adults who had never had malaria or received a vaccine for malaria. The participants received L9LS either intravenously or subcutaneously at a dose of 1 mg, 5 mg, or 20 mg per kilogram of body weight. Within 2 to 6 weeks after the administration of L9LS, both the participants who received L9LS and the control participants underwent controlled human malaria infection in which they were exposed to mosquitoes carrying Plasmodium falciparum (3D7 strain).

RESULTS

No safety concerns were identified. L9LS had an estimated half-life of 56 days, and it had dose linearity, with the highest mean (±SD) maximum serum concentration (C_max) of 914.2±146.5 μg per milliliter observed in participants who had received 20 mg per kilogram intravenously and the lowest mean C_max of 41.5±4.7 μg per milliliter observed in those who had received 1 mg per kilogram intravenously; the mean C_max was 164.8±31.1 in the participants who had received 5 mg per kilogram intravenously and 68.9±22.3 in those who had received 5 mg per kilogram subcutaneously. A total of 17 L9LS recipients and 6 control participants underwent controlled human malaria infection. Of the 17 participants who received a single dose of L9LS, 15 (88%) were protected after controlled human malaria infection. Parasitemia did not develop in any of the participants who received 5 or 20 mg per kilogram of intravenous L9LS. Parasitemia developed in 1 of 5 participants who received 1 mg per kilogram intravenously, 1 of 5 participants who received 5 mg per kilogram subcutaneously, and all 6 control participants through 21 days after the controlled human malaria infection. Protection conferred by L9LS was seen at serum concentrations as low as 9.2 μg per milliliter.

CONCLUSIONS

In this small trial, L9LS administered intravenously or subcutaneously protected recipients against malaria after controlled infection, without evident safety concerns. (Funded by the National Institute of Allergy and Infectious Diseases; VRC 614 ClinicalTrials.gov number, NCT05019729.).

Investigation of Intestinal and Blood Parasites in People Returning to Turkey with a History of Traveling Abroad During the Pandemic

OBJECTIVE

To investigate intestinal and blood parasites in people who have a history of traveling abroad during the Coronavirus disease-2019 pandemic and returning to Turkey.

METHODS

In this study, 104 patients with gastrointestinal system and/or fever complaints who had traveled abroad during the pandemic period and returned to Turkey were included. Parasitic agents were investigated by taking blood and stool samples from the patients. Additionally, urine samples were obtained from patients with hematuria or dysuria with the suspicion of schistosomiasis. A direct microscopic examination, the Crypto-Giardia immunochromatographic test, and ELISA methods were used in the examination of the stool samples. In order to detect Plasmodium species, blood samples were examined by preparing both the rapid diagnostic test and thick drop and thin smear preparations.

RESULTS

One or more parasite species were detected in 38 (38.5%) of 104 patients included in the study. While intestinal parasites were detected in 16 (32%) of 50 patients who traveled to Iran and 16 (33.3%) of 48 patients who traveled to Northern Iraq, blood parasites were not found. Schistosoma mansoni was detected in all 5 of the patients with a history of traveling to Sudan. Plasmodium falciparum was detected in 1 patient who traveled to the African continent.

CONCLUSION

It is vital to take precautions to prevent parasitic diseases, such as malaria and schistosomiasis, during travels to African countries. During travels to neighboring countries of Turkey, such as Northern Iraq and Iran, hygiene should be paid attention to, so as to prevent contracting intestinal parasitic diseases. In addition, it was concluded that people who plan to travel abroad should have information about the endemic parasitic diseases of the country that they are going to.

The monoterpene 1,8-cineole prevents cerebral edema in a murine model of severe malaria

1,8-Cineole is a naturally occurring compound found in essential oils of different plants and has well-known anti-inflammatory and antimicrobial activities. In the present work, we aimed to investigate its potential antimalarial effect, using the following experimental models: (1) the erythrocytic cycle of Plasmodium falciparum; (2) an adhesion assay using brain microvascular endothelial cells; and (3) an experimental cerebral malaria animal model induced by Plasmodium berghei ANKA infection in susceptible mice. Using the erythrocytic cycle of Plasmodium falciparum, we characterized the schizonticidal effect of 1,8-cineole. This compound decreased parasitemia in a dose-dependent manner with a half maximal inhibitory concentration of 1045.53 ± 63.30 μM. The inhibitory effect of 972 μM 1,8-cineole was irreversible and independent of parasitemia. Moreover, 1,8-cineole reduced the progression of intracellular development of the parasite over 2 cycles, inducing important morphological changes. Ultrastructure analysis revealed a massive loss of integrity of endomembranes and hemozoin crystals in infected erythrocytes treated with 1,8-cineole. The monoterpene reduced the adhesion index of infected erythrocytes to brain microvascular endothelial cells by 60%. Using the experimental cerebral malaria model, treatment of infected mice for 6 consecutive days with 100 mg/kg/day 1,8-cineole reduced cerebral edema with a 50% reduction in parasitemia. Our data suggest a potential antimalarial effect of 1,8-cineole with an impact on the parasite erythrocytic cycle and severe disease.

A portable brightfield and fluorescence microscope toward automated malarial parasitemia quantification in thin blood smears

Malaria is often most endemic in remote regions where diagnostic microscopy services are unavailable. In such regions, the use of rapid diagnostic tests fails to quantify parasitemia measurements which reflect the concentration of Plasmodium parasites in the bloodstream. Thus, novel diagnostic and monitoring technologies capable of providing such information could improve the quality of treatment, monitoring, and eradication efforts. A low-cost, portable microscope for gathering quantitative parasitemia data from fluorescently stained thin blood smears is presented. The system employs bimodal imaging using components optimized for cost savings, system robustness, and optical performance. The microscope is novel for its use of monochromatic visible illumination paired with a long working distance singlet aspheric objective lens that can image both traditionally mounted and cartridge-based blood smears. Eight dilutions of red blood cells containing laboratory cultured wild-type P. falciparum were used to create thin smears which were stained with SYBR Green-1 fluorescent dye. Two subsequent images are captured for each field-of-view, with brightfield images providing cell counts and fluorescence images providing parasite localization data. Results indicate the successful resolution of sub-micron sized parasites, and parasitemia measurements from the prototype microscope display linear correlation with measurements from a benchtop microscope with a limit of detection of 0.18 parasites per 100 red blood cells.

4-nitrobenzoylcoumarin potentiates the antiparasitic, anti-inflammatory and cardioprotective effects of benznidazole in a murine model of acute Trypanosoma cruzi infection

The anti-inflammatory and cardioprotective potential of coumarin metabolites in infectious myocarditis remains overlooked. Thus, the impact of the synthetic 4-nitrobenzoylcoumarin (4NB) alone and combined with benznidazole (Bz) in a murine model of Trypanosoma cruzi-induced acute myocarditis was investigated. Swiss mice infected with T. cruzi were randomized in 8 groups: uninfected, infected untreated or treated with 50 and 100 mg/kg 4NB or Bz alone and combined. Treatments were administered by gavage for 20 days. Cytokines (IL-2, IL-6, IL-10, IL-17, TNFα, and IFN-γ), immunoglobulin reactivity index (total IgG, IgG1, IgG2a and IgG2b), atrial natriuretic peptide (ANP), parasitemia, serum transaminases, heart and liver cellularity were analyzed. T. cruzi infection induced blood parasitism, heart and liver inflammation, upregulated all cytokines, IgG reactivity index, ANP and transaminase levels, determining 43% mortality in untreated mice. Transaminase levels, mean parasitemia, heart inflammation and ANP were reduced in 4NB-treated mice, reaching a 100% survival rate. Total survival (100%) was also obtained in all combinations of Bz and 4NB, which were effective in reducing blood parasitism, transaminases, cytokines and ANP levels, IgG reactivity index, liver and heart interstitial cellularity compared to 50 mg/kg Bz. Our findings indicated that 4NB alone and combined with Bz was well tolerated, showing no evidence of hepatotoxicity. Mainly in combination, these drugs exerted protective effects against T. cruzi-induced acute myocarditis by attenuating blood parasitism, systemic and heart inflammation. Thus, combinations based on 4NB and Bz are potentially relevant to develop new and more effective drug regimens for the treatment of T. cruzi-induced myocarditis.

Malaria Parasitaemia and its Associated Factors among Febrile Children in a Tertiary Hospital in Southwest Nigeria

BACKGROUND

Malaria is a parasitic disease of public health concern especially among children because of their vulnerability. Objective: The study sought to evaluate the prevalence and severity of malaria and to assess the factors associated with malaria parasitaemia among children.

METHODS

This was a hospital-based cross-sectional observation study. We enrolled 303 children aged 6 to 59 months who presented with fever. A structured questionnaire was used to obtain the demographic characteristics, determinant factors and the use of malaria preventive measures. Microscopic examination of blood film for malaria parasite was done. Data were analysed using SPSS version 23.0. The Pearson's Chi-square was used to determine the association between selected socio-demographic variables, clinical characteristics of participants and presence of malaria parasitaemia. A p-value less than 0.05 was considered significant.

RESULTS

The mean ± SD age was 24.36 ± 16.63 months, 183 (60.4%) were male. Two hundred and thirteen (70.3%) participants tested positive for Plasmodium falciparum. Severe malaria accounted for 21.1% of all malaria cases. Severe anaemia (37.8%) and cerebral malaria (24.4%) were the common complications observed. Malaria was significantly associated with increasing age (p = 0.007). Children who slept regularly under LLIN and those using insecticidal spray were more likely to be protected from developing malaria (p = 0.002, p = 0.001, respectively). The socioeconomic status, maternal education, family size and knowledge of LLIN were not associated with the development of malaria (p= 0.901, 0.136, 0.413, 0.166, respectively).

CONCLUSION

The prevalence of malaria is high; there is a need to increase the coverage of IRS, together with LLINs to reduce the transmission and burden of malaria, particularly among the susceptible population.

Heavy Malaria Parasitaemia in Young Nigerian Infants: Prevalence, Determinants and Implication for the Health System

BACKGROUND

Infants who are aged six months and below are often protected from malaria and usually present with light parasitaemia when infected. However, complications following heavy malaria parasitaemia in this age group are being increasingly reported. This study set out to determine the prevalence, determinants and the public health implications of heavy malaria parasitaemia in young infants (aged one to six months) at the Wesley Guild Hospital, Ilesa (a unit of the Obafemi Awolowo University Teaching Hospitals Complex).

METHODS

Ill infants aged one to six months in out-patient and in-patient care were recruited over an 11-month period. Clinical examinations and blood film for malaria parasite were done for all the study participants. Heavy parasitaemia was defined as > 5000 parasites/µl. Clinical predictors of heavy parasitaemia were determined.

RESULTS

Heavy parasitaemia was observed in 16(23.9%) of the sixty-seven participants with malaria infection. Presence of fever at presentation (p=0.007), excessive crying (p=0.003) and pallor (p=0.001) were associated with heavy malaria parasitaemia. However, pallor (OR = 20.653; 95%CI 2.091-203.958; p=0.010) was the only independent predictor of heavy parasitaemia among the young infants.

CONCLUSION

About one-in-four ill young infants with malaria had heavy parasitaemia, which was predicted by pallor. Hence, the presence of pallor and factors related to low parental socio-economic status should increase the suspicion of heavy malaria parasitaemia in ill young infants in malaria endemic settings.

Over-dispersed Trypanosoma cruzi parasite load in sylvatic and domestic mammals and humans from northeastern Argentina

BACKGROUND

The distribution of parasite load across hosts may modify the transmission dynamics of infectious diseases. Chagas disease is caused by a multi-host protozoan, Trypanosoma cruzi, but the association between host parasitemia and infectiousness to the vector has not been studied in sylvatic mammalian hosts. We quantified T. cruzi parasite load in sylvatic mammals, modeled the association of the parasite load with infectiousness to the vector and compared these results with previous ones for local domestic hosts.

METHODS

The bloodstream parasite load in each of 28 naturally infected sylvatic mammals from six species captured in northern Argentina was assessed by quantitative PCR, and its association with infectiousness to the triatomine Triatoma infestans was evaluated, as determined by natural or artificial xenodiagnosis. These results were compared with our previous results for 88 humans, 70 dogs and 13 cats, and the degree of parasite over-dispersion was quantified and non-linear models fitted to data on host infectiousness and bloodstream parasite load.

RESULTS

The parasite loads of Didelphis albiventris (white-eared opossum) and Dasypus novemcinctus (nine-banded armadillo) were directly and significantly associated with infectiousness of the host and were up to 190-fold higher than those in domestic hosts. Parasite load was aggregated across host species, as measured by the negative binomial parameter, k, and found to be substantially higher in white-eared opossums, cats, dogs and nine-banded armadillos (range: k = 0.3-0.5) than in humans (k = 5.1). The distribution of bloodstream parasite load closely followed the "80-20 rule" in every host species examined. However, the 20% of human hosts, domestic mammals or sylvatic mammals exhibiting the highest parasite load accounted for 49, 25 and 33% of the infected triatomines, respectively.

CONCLUSIONS

Our results support the use of bloodstream parasite load as a proxy of reservoir host competence and individual transmissibility. The over-dispersed distribution of T. cruzi bloodstream load implies the existence of a fraction of highly infectious hosts that could be targeted to improve vector-borne transmission control efforts toward interruption transmission. Combined strategies that decrease the parasitemia and/or host-vector contact with these hosts would disproportionally contribute to T. cruzi transmission control.

E3 ubiquitin ligase RNF123-deficient mice exhibit reduced parasitemia and mortality in rodent malaria (Plasmodium yoelii 17XL) infection

Increased levels of several human ubiquitin ligases, including ring finger protein 123 (RNF123), in red blood cells with Plasmodium falciparum infection, have been reported. RNF123 is an E3 ubiquitin ligase that is highly expressed in erythroid cells. However, the function of the RNF123 gene and the relationship between the RNF123 gene and malarial parasite has not been clarified in vivo. In this study, we generated RNF123-deficient mice using the CRISPR/Cas9 system, and analyzed malaria susceptibility and erythrocyte morphology. The levels of parasitemia 5 days post-infection and mortality 21 days post-infection with the lethal type of rodent malaria (Plasmodium yoelii 17XL) in RNF123-deficient mice was significantly lower than that in wild-type mice. In contrast, red blood cell morphology in RNF123-deficient mice was almost normal. These results suggest that erythrocytic RNF123 plays a role in susceptibility to rodent malaria infection, but does not play a role in erythrocyte morphology.

Identification and Enumeration of Plasmodium falciparum Parasites by Light Microscopy

Estimating malaria parasite density is important for patient care and management in rural and urban health centers in endemic areas. Here, we describe methodologically the protocols and methods to identify and enumerate Plasmodium falciparum parasites from infected blood using light microscopy. We provide step-by-step protocols and evaluate any possible drawbacks that may limit the methods and prospects of using light microscopy in diagnosing malaria.

Clinical recovery of Macaca fascicularis infected with Plasmodium knowlesi

BACKGROUND

Kra monkeys (Macaca fascicularis), a natural host of Plasmodium knowlesi, control parasitaemia caused by this parasite species and escape death without treatment. Knowledge of the disease progression and resilience in kra monkeys will aid the effective use of this species to study mechanisms of resilience to malaria. This longitudinal study aimed to define clinical, physiological and pathological changes in kra monkeys infected with P. knowlesi, which could explain their resilient phenotype.

METHODS

Kra monkeys (n = 15, male, young adults) were infected intravenously with cryopreserved P. knowlesi sporozoites and the resulting parasitaemias were monitored daily. Complete blood counts, reticulocyte counts, blood chemistry and physiological telemetry data (n = 7) were acquired as described prior to infection to establish baseline values and then daily after inoculation for up to 50 days. Bone marrow aspirates, plasma samples, and 22 tissue samples were collected at specific time points to evaluate longitudinal clinical, physiological and pathological effects of P. knowlesi infections during acute and chronic infections.

RESULTS

As expected, the kra monkeys controlled acute infections and remained with low-level, persistent parasitaemias without anti-malarial intervention. Unexpectedly, early in the infection, fevers developed, which ultimately returned to baseline, as well as mild to moderate thrombocytopenia, and moderate to severe anaemia. Mathematical modelling and the reticulocyte production index indicated that the anaemia was largely due to the removal of uninfected erythrocytes and not impaired production of erythrocytes. Mild tissue damage was observed, and tissue parasite load was associated with tissue damage even though parasite accumulation in the tissues was generally low.

CONCLUSIONS

Kra monkeys experimentally infected with P. knowlesi sporozoites presented with multiple clinical signs of malaria that varied in severity among individuals. Overall, the animals shared common mechanisms of resilience characterized by controlling parasitaemia 3-5 days after patency, and controlling fever, coupled with physiological and bone marrow responses to compensate for anaemia. Together, these responses likely minimized tissue damage while supporting the establishment of chronic infections, which may be important for transmission in natural endemic settings. These results provide new foundational insights into malaria pathogenesis and resilience in kra monkeys, which may improve understanding of human infections.

In vivo antimalarial activity of a probiotic bacterium Lactobacillus sakei isolated from traditionally fermented milk in BALB/c mice infected with Plasmodium berghei ANKA

ETHNOPHARMACOLOGICAL RELEVANCE

Milk production, processing and consumption are integral part of traditional practices in Fulani tribe of Cameroon. It has been observed that Fulani are resistant to malaria. Dairy products traditionally processed by Fulani are intensively used in the ritual treatment of malarial, inflammations and behavioural disorders. Many studies have demonstrated that fermented milk is a rich source of probiotic bacteria. However, the antimalarial activity of probiotics isolated from this natural source has not been experimentally tested.

AIM OF THE STUDY

Hence, this study was therefore aimed at evaluating the antimalarial activity of a probiotic bacterium Lactobacillus sakei isolated from traditionally fermented milk in mice infected with chloroquine sensitive Plasmodium berghei ANKA.

MATERIALS AND METHODS

The probiotic bacterium was isolated from the Cameroonian Mborro Fulani's traditionally fermented milk and identified using the 16S r RNA gene sequencing. The schizontocidal activity of Lactobacillus sakei on established malaria infection was evaluated. Eighty-four healthy young adult Balb/c mice infected with Plasmodium berghei parasite were randomly divided into two sets of seven group of six mice each, and were given three different doses of Lactobacillus sakei, chloroquine and sulfadoxine/pyrimethamine for seven and fourteen days respectively. The level of parasitaemia, body temperature, survival time and haematological parameters were evaluated.

RESULTS

The parasite growth inhibition was observed to increase with increasing dose of probiotic bacterium with maximum suppression being 100 % at dose 3 on day 20. Also, the probiotic bacterium significantly prevented body weight loss and was associated with body temperature reduction and prevented (p<0.05) a decrease in haematological parameters compared to that untreated malaria infected mice.

CONCLUSION

The results obtained suggest that Lactobacillus sakei is a probiotic bacterium with antimalarial activity in mice infected with chloroquine sensitive Plasmodium berghei.

Prevalence, density and predictors of malaria parasitaemia among ill young Nigerian infants

INTRODUCTION

infants in the first six months of life are relatively protected from malaria. Emerging reports from endemic regions however are showing increasing malaria susceptibility in this age group. This study set out to determine the prevalence, parasite density and predictive factors for malaria parasitaemia in ill young infants at the Wesley Guild Hospital (WGH), Ilesa, Nigeria.

METHODS

ill infants aged one to six months were consecutively recruited over an 11-month period in a hospital based cross-sectional study. History of illness, sociodemographic and perinatal history were obtained; clinical examination and results of venous blood for thick and thin film malaria parasite examinations were recorded and analyzed.

RESULTS

the mean (SD) age of the 350 infants was 3.4 (1.6) months with male: female (M: F) of 1.2: 1. The prevalence of malaria parasitaemia (all plasmodium falciparum) was 19.1% while parasite density ranged from 24.0 to 400,000 parasites/µl, median (IQR) 900 (250-4,588)/µl. Sixteen (4.6%) had heavy malaria parasitaemia (>5000/µl). Low social class (OR=2.457; 95%CI 1.404-4.300; p=0.002), suboptimal antenatal care (OR=2.226; 95%CI 1.096-4.522; p=0.027), low birth weight infants (OR=4.818; 95%CI 2.317-10.018; p=<0.001) and injudicious use of haematinics (OR=3.192; 95%CI1.731-5.886; p=<0.001) were predictors of malaria parasitaemia among the infants.

CONCLUSION

one-in-five ill young infants had malaria parasitaemia with heavy parasitaemia in 23.8% of infected infants. Malaria parasitaemia was associated with modifiable factors, high index of suspicion in endemic region and optimal maternal and child care services may assist to reduce the burden of malaria in this age group.

Fibronectin degradation as biomarker for Trypanosoma cruzi infection and treatment monitoring in mice

Biomarkers (coming from host or parasite) to monitor Chagas disease (CD) progression as well as the therapeutic response in chronic CD are critically needed, since seronegativization, which may be considered the best indicator of therapeutic cure, takes several years to be observed in adults. Several molecules have been suggested as biomarkers for CD, however, they have to be validated. Taking advantage of mouse models of Trypanosoma cruzi infection, we investigated changes in the degradation profile of fibronectin in plasma. The degradation profile of fibronectin was different in the acute phase compared to the chronic phase of the infection. Fibronectin fragments of approximately 150, 100, 40 and 30 kDa were identified. Furthermore, those degradation profiles correlated with acute parasitaemia as well as with cardiac parasite burden and tissue damage during the infection. The usefulness of fibronectin degradation as a biomarker for therapeutic response following drug treatment and immunotherapeutic vaccination also was evaluated and a decreased fibronectin degradation profile was observed upon benznidazole or a vaccine candidate treatment.

Mouse experiments demonstrate differential pathogenicity and virulence of Trypanosoma brucei rhodesiense strains

Trypanosoma brucei rhodesiense is the causative agent for Rhodesian human African trypanosomiasis. The disease is considered acute, but varying clinical outcomes including chronic infections have been observed. The basis for these different clinical manifestations is thought to be associated with a combination of parasite and host factors. In the current study, Trypanosoma brucei rhodesiense strains responsible for varying infection outcomes were sought using mouse model. Clinical rHAT parasite isolates were subjected to PCR tests to confirm presence of the serum resistance associated (SRA) gene. Thereafter, four T. b. rhodesiense isolates were subjected to a comparative pathogenicity study using female Swiss white mice; the parasite strains were compared on the basis of parasitaemia, host survival time, clinical and postmortem biomarkers of infection severity. Isolates identified to cause acute and chronic disease were compared for establishment in insect vector, tsetse fly. The mouse survival time was significantly different (Log-rankp = 0.0001). With mice infected with strain KETRI 3801 exhibiting the shortest survival time (20 days) as compared to those infected with KETRI 3928 that, as controls, survived past the 60 days study period. In addition, development of anaemia was rapid in KETRI 3801 and least in KETRI 3928 infections, and followed the magnitude of survival time. Notably, hepatosplenomegaly was pronounced with longer survival. Mouse weight and feed intake reduced (KETRI 3801 > KETRI 2636 > EATRO 1762) except in KETRI 3928 infections which remained similar to controls. Comparatively, acute to chronic infection outcomes is in the order of KETRI 3801 > KETRI 2636 > EATRO 1762 > KETRI 3928, indicative of predominant role of strain dependent factors. Further, KETRI 3928 strain established better in tsetse as compared to KETRI 3801, suggesting that transmission of strains causing chronic infections could be common. In sum, we have identified Trypanosoma brucei rhodesiense strains that cause acute and chronic infections in mice, that will be valuable in investigating pathogen - host interactions responsible for varying disease outcomes and transmission in African trypanosomiasis.

Recombinase polymerase amplification with lateral flow strip for detecting Babesia microti infections

Babesia microti is one of the most important pathogens causing humans and rodents babesiosis-an emerging tick-borne disease that occurs worldwide. At present, the gold standard for the detection of Babesia is the microscopic examination of blood smears, but this diagnostic test has several limitations. The recombinase polymerase amplification with lateral flow (LF-RPA) assay targeting the mitochondrial cytochrome oxidase subunit I (cox I) gene of B. microti was developed in this study. The LF-RPA can be performed within 10-30 min, at a wide range of temperatures between 25 and 45 °C, which is much faster and easier to perform than conventional PCR. The results showed that the LF-RAP can detect 0.25 parasites/μl blood, which is 40 times more sensitive than the conventional PCR based on the V4 variable region of 18S rRNA. Specificity assay showed no cross-reactions with DNAs of related apicomplexan parasites and their host. The applicability of the LF-RPA method was further evaluated using two clinical human samples and six experimental mice samples, with seven samples were positively detected, while only three of them were defined as positive by conventional PCR. These results present the developed LF-RPA as a new simple, specific, sensitive, rapid and convenient method for diagnosing infection with B. microti. This novel assay was the potential to be used in field applications and large-scale sample screening.

Diatretol, an α, α'-dioxo-diketopiperazine, is a potent in vitro and in vivo antimalarial

A fungal metabolite, diatretol, has shown to be a promising antimalarial agent. Diatretol displayed potent in vitro antiparasitic activity against the Plasmodium falciparum K1 strain, with an IC50 value of 378 ng ml-1, as well as in vivo efficacy in a Plasmodium berghei-infected mice model, with ca. 50% inhibition at 30 mg/kg (p.o.).

Glucose-6-phosphate dehydrogenase activity in individuals with and without malaria: Analysis of clinical trial, cross-sectional and case-control data from Bangladesh

BACKGROUND

Glucose-6-phosphate dehydrogenase (G6PD) activity is dependent upon G6PD genotype and age of the red blood cell (RBC) population, with younger RBCs having higher activity. Peripheral parasitemia with Plasmodium spp. induces hemolysis, replacing older RBCs with younger cells with higher G6PD activity. This study aimed to assess whether G6PD activity varies between individuals with and without malaria or a history of malaria.

METHODS AND FINDINGS

Individuals living in the Chittagong Hill Tracts of Bangladesh were enrolled into 3 complementary studies: (i) a prospective, single-arm clinical efficacy trial of patients (n = 175) with uncomplicated malaria done between 2014 and 2015, (ii) a cross-sectional survey done between 2015 and 2016 (n = 999), and (iii) a matched case-control study of aparasitemic individuals with and without a history of malaria done in 2020 (n = 506). G6PD activity was compared between individuals with and without malaria diagnosed by microscopy, rapid diagnostic test (RDT), or polymerase chain reaction (PCR), and in aparasitemic participants with and without a history of malaria. In the cross-sectional survey and clinical trial, 15.5% (182/1,174) of participants had peripheral parasitemia detected by microscopy or RDT, 3.1% (36/1,174) were positive by PCR only, and 81.4% (956/1,174) were aparasitemic. Aparasitemic individuals had significantly lower G6PD activity (median 6.9 U/g Hb, IQR 5.2-8.6) than those with peripheral parasitemia detected by microscopy or RDT (7.9 U/g Hb, IQR 6.6-9.8, p < 0.001), but G6PD activity similar to those with parasitemia detected by PCR alone (submicroscopic parasitemia) (6.1 U/g Hb, IQR 4.8-8.6, p = 0.312). In total, 7.7% (14/182) of patients with malaria had G6PD activity < 70% compared to 25.0% (248/992) of participants with submicroscopic or no parasitemia (odds ratio [OR] 0.25, 95% CI 0.14-0.44, p < 0.001). In the case-control study, the median G6PD activity was 10.3 U/g Hb (IQR 8.8-12.2) in 253 patients with a history of malaria and 10.2 U/g Hb (IQR 8.7-11.8) in 253 individuals without a history of malaria (p = 0.323). The proportion of individuals with G6PD activity < 70% was 11.5% (29/253) in the cases and 15.4% (39/253) in the controls (OR 0.7, 95% CI 0.41-1.23, p = 0.192). Limitations of the study included the non-contemporaneous nature of the clinical trial and cross-sectional survey.

CONCLUSIONS

Patients with acute malaria had significantly higher G6PD activity than individuals without malaria, and this could not be accounted for by a protective effect of G6PD deficiency. G6PD-deficient patients with malaria may have higher than expected G6PD enzyme activity and an attenuated risk of primaquine-induced hemolysis compared to the risk when not infected.

Intervention of standardized ethanol leaf extract of Annickia polycarpa, (DC.) Setten and Maas ex I.M. Turner. (Annonaceae), in Plasmodium berghei infested mice produced anti-malaria action and normalized gross hematological indices

ETHNOPHARMACOLOGICAL RELEVANCE

Malaria is a global public health burden due to large number of annual infections and casualties caused by its hematological complications. The bark of Annickia polycarpa is an effective anti-malaria agent in African traditional medicine. However, there is no standardization parameters for A. polycarpa. The anti-malaria properties of its leaf are also not known.

AIM OF THE STUDY

To standardize the ethanol leaf extract of A. polycarpa (APLE) and investigate its anti-malaria properties and the effect of its treatment on hematological indices in Plasmodium berghei infected mice in the Rane's test.

MATERIALS AND METHODS

Malaria was induced by inoculating female ICR mice with 1.0 × 107P. berghei-infected RBCs in 0.2 mL (i.p.) of blood. Treatment was commenced 3 days later with APLE 50, 200, 400 mg/kg p.o., Quinine 30 mg/kg i.m. (Standard drug) or sterile water (Negative control) once daily per group for 4 successive days. Anti-malarial activity and gross malaria indices such as hyperparasitemia, mean change in body weight and mean survival time (MST) were determined for each group. Changes in white blood cells (WBCs), red blood cells (RBCs), platelets (PLT) counts, hemoglobin (HGB) concentration, hematocrit (HCT) and mean corpuscular volume (MCV) were also measured in the healthy mice before infection as baseline and on day 3 and 8 after inoculation using complete blood count. Standardization was achieved by UHPLC-MS chemical fingerprint analysis and quantitative phytochemical tests.

RESULTS

APLE, standardized to its total alkaloids, phenolics and saponin contents, produced significant (P < 0.05) dose-dependent clearance of mean hyperparasitemia of 22.78 ± 0.93% with the minimum parasitemia level of 2.01 ± 0.25% achieved at 400 mg/kg p.o. on day 8. Quinine 30 mg/kg i.m. achieved a minimum parasitemia level of 6.15 ± 0.92%. Moreover, APLE (50-400 mg/kg p.o.) evoked very significant anti-malaria activity of 89.22-95.50%. Anti-malaria activity of Quinine 30 mg/kg i.m. was 86.22%. APLE also inverse dose-dependently promotes weight gain with the effect being significant (P < 0.05) at 50 mg/kg p.o. Moreover, APLE dose-dependently increased the MST of malaria infested mice with 100% survival at 400 mg/kg p.o. Quinine 30 mg/kg i.m. also produce 100% survival rate but did not promote (P > 0.05) weight gain. Hematological studies revealed the development of leukocytopenia, erythrocytosis, microcytic anemia and thrombocytopenia in the malaria infected mice which were reverted with the treatment of APLE 50-400 mg/kg p.o. or Quinine 30 mg/kg i.m. but persisted in the negative control. The UHPLC-MS fingerprint analysis of APLE led to identification of one oxoaporphine and two aporphine alkaloids (1-3). Alkaloids 1 and 3 are being reported in this plant for the first time.

CONCLUSION

These results indicate that APLE possessed significant anti-malaria, immunomodulatory, erythropoietic and hematinic actions against malaria infection. APLE also has the ability to revoke deleterious physiological alteration produced by malaria and hence, promote clinical cure. These properties of APLE are due to its constituents especially, aporphine and oxoaporphine alkaloids.

In vitro and in vivo antiplasmodial activity of hydroethanolic bark extract of Bridelia atroviridis müll. Arg. (Euphorbiaceae) and lc-ms-based phytochemical analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Malaria is a life-threatening health problem worldwide and treatment remains a major challenge. Natural products from medicinal plants are credible sources for better anti-malarial drugs.

AIM OF THE STUDY

This study aimed at assessing the in vitro and in vivo antiplasmodial activities of the hydroethanolic extract of Bridelia atroviridis bark.

MATERIALS AND METHODS

The phytochemical characterization of Bridelia atroviridis extract was carried out by High-Performance Liquid Chromatography-Mass spectrometry (HPLC-MS). The cytotoxicity test on Vero cells was carried out using the resazurin-based assay while the in vitro antiplasmodial activity was determined on Plasmodium falciparum (Dd2 strain, chloroquine resistant) using the SYBR green I-based fluorescence assay. The in vivo assay was performed on Plasmodium berghei-infected rats daily treated for 5 days with distilled water (10 mL/kg) for malaria control, 25 mg/kg of chloroquine sulfate for positive control and 50, 100 and 200 mg/kg of B. atroviridis extract for the three test groups. Parasitaemia was daily monitored using 10% giemsa-staining thin blood smears. At the end of the treatment, animals were sacrificed, blood was collected for hematological and biochemical analysis while organs were removed for biochemical and histopathological analyses.

RESULTS

The HPLC-MS analysis data of B. atroviridis revealed the presence of bridelionoside D, isomyricitrin, corilagin, myricetin and 5 others compounds not yet identified. Bridelia atroviridis exhibited good in vitro antiplasmodial activity with the IC₅₀ evaluated at 8.08 μg/mL and low cytotoxicity with the median cytotoxic concentration (CC₅₀) higher than 100 μg/mL. B. atroviridis extract significantly reduced the parasitemia (p < 0.05) with an effective dose-50 (ED-50) of 89 mg/kg. B. atroviridis also prevented anemia, leukocytosis and liver and kidneys impairment by decrease of transaminases, ALP, creatinine, uric acid, and triglycerides concentrations. As well, B. atroviridis extract decreased some pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) levels and significantly improved the anti-inflammatory status (P < 0.01) of infected animals marked by a decrease of IL-10 concentration. These results were further confirmed by the improved of antioxidant status and the quasi-normal microarchitecture of the liver, kidneys and spleen in test groups. Overall, the hydroethanolic bark extract of Bridelia atroviridis demonstrated antimalarial property and justified its use in traditional medicine to manage malaria disease.

Antrocaryon micraster (A. Chev. And Guillaumin) stem bark extract demonstrated anti-malaria action and normalized hematological indices in Plasmodium berghei infested mice in the Rane's test

ETHNOPHARMACOLOGICAL RELEVANCE

Malaria is caused by infection with some species of Plasmodium parasite which leads to adverse alterations in physical and hematological features of infected persons and ultimately results in death. Antrocaryon micraster is used to treat malaria in Ghanaian traditional medicine. However, there is no scientific validation of its anti-malaria properties. The plant does not also have any chemical fingerprint or standardization parameters.

AIM OF THE STUDY

This study sought to evaluate the anti-malaria activity of standardized A. micraster stem bark extract (AMSBE) and its effect on mean survival time (MST) and body weight reduction of Plasmodiumberghei infested mice. And to study the effect of treatment of AMSBE on hematological indices of the P. berghei infested mice in order to partly elucidate its anti-malarial mechanism of action.

MATERIALS AND METHODS

Malaria was induced in female ICR mice by infecting them with 0.2 mL of blood (i.p.) containing 1.0 × 10⁷P. berghei-infested RBCs from a donor mouse and leaving them without treatment for 3 days. AMSBE or Lonart (standard control) was then orally administered at 50, 200 and 400 mg/kg or 10 mg/kg once daily for 4 consecutive days. The untreated control received sterile water. Malaria parasitemia reduction, anti-malarial activity, mean change in body weight and MST of the parasitized mice were evaluated. Furthermore, changes in white blood cells (WBCs), red blood cells (RBCs), platelets count, hemoglobin (HGB), hematocrit (HCT) and mean corpuscular volume (MCV) were also determined in the healthy animals before infection as baseline and on days 3, 5 and 8 after infection by employing complete blood count. Standardization of AMSBE was achieved by quantification of its constituents and chemical fingerprint analysis using UHPLC-MS.

RESULTS

Administration of AMSBE, standardized to 41.51% saponins and 234.960 ± 0.026 mg/g of GAE phenolics, produced significant (P < 0.05) reduction of parasitemia development, maximum anti-malaria activity of 46.01% (comparable to 32.53% produced by Lonart) and significantly (P < 0.05) increased body weight and MST of P. berghei infected mice compared to the untreated control. Moreover, there were significant (P > 0.05) elevation in WBCs, RBCs, HGB, HCT and platelets in the parasitized-AMSBE (especially at 400 mg/kg p.o.) treated mice compared to their baseline values. Whereas, the non-treated parasitized control recorded significant reduction (P < 0.05) in all the above-mentioned parameters compared to its baseline values. The UHPLC-MS fingerprint of AMSBE revealed four compounds with their retention times, percentage composition in their chromatograms and m/z of the molecular ions and fragments in the spectra.

CONCLUSIONS

These results show that A. micraster stem bark possessed significant anti-malaria effect and also has the ability to abolish body weight loss, leucopenia, anemia and thrombocytopenia in P. berghei infected mice leading to prolonged life span. The UHPLC-MS fingerprint developed for AMSBE can be used for rapid authentication and standardization of A. micraster specimens and herbal preparations produced from its hydroethanolic stem bark extract to ensure consistent biological activity. The results justify A. micraster's use as anti-malaria agent.

Antibody Responses to Crude Gametocyte Extract Predict Plasmodium falciparum Gametocyte Carriage in Kenya

Background

Malaria caused by Plasmodium falciparum remains a serious global public health challenge especially in Africa. Interventions that aim to reduce malaria transmission by targeting the gametocyte reservoir are key to malaria elimination and/or eradication. However, factors that are associated with gametocyte carriage have not been fully explored. Consequently, identifying predictors of the infectious reservoir is fundamental in the elimination campaign.

Methods

We cultured P. falciparum NF54 gametocytes (to stage V) and prepared crude gametocyte extract. Samples from a total of 687 participants (aged 6 months to 67 years) representing two cross-sectional study cohorts in Kilifi, Kenya were used to assess IgG antibody responses by ELISA. We also analyzed IgG antibody responses to the blood-stage antigen AMA1 as a marker of asexual parasite exposure. Gametocytemia and asexual parasitemia data quantified by microscopy and molecular detection (QT-NASBA) were used to determine the relationship with antibody responses, season, age, and transmission setting. Multivariable logistic regression models were used to study the association between antibody responses and gametocyte carriage. The predictive power of the models was tested using the receiver operating characteristic (ROC) curve.

Results

Multivariable logistic regression analysis showed that IgG antibody response to crude gametocyte extract predicted both microscopic (OR=1.81 95% CI: 1.06-3.07, p=0.028) and molecular (OR=1.91, 95% CI: 1.11-3.29, p=0.019) P. falciparum gametocyte carriage. Antibody responses to AMA1 were also associated with both microscopic (OR=1.61 95% CI: 1.08-2.42, p=0.020) and molecular (OR=3.73 95% CI: 2.03-6.74, p<0.001) gametocytemia. ROC analysis showed that molecular (AUC=0.897, 95% CI: 0.868-0.926) and microscopic (AUC=0.812, 95% CI: 0.758-0.865) multivariable models adjusted for gametocyte extract showed very high predictive power. Molecular (AUC=0.917, 95% CI: 0.891-0.943) and microscopic (AUC=0.806, 95% CI: 0.755-0.858) multivariable models adjusted for AMA1 were equally highly predictive.

Conclusion

In our study, it appears that IgG responses to crude gametocyte extract are not an independent predictor of gametocyte carriage after adjusting for AMA1 responses but may predict gametocyte carriage as a proxy marker of exposure to parasites. Serological responses to AMA1 or to gametocyte extract may facilitate identification of individuals within populations who contribute to malaria transmission and support implementation of transmission-blocking interventions.

17β-Estradiol Is Involved in the Sexual Dimorphism of the Immune Response to Malaria

Malaria is the leading cause of parasitic infection-related death globally. Additionally, malaria-associated mortality is higher in men than in women, and this sexual dimorphism reflects differences in innate and adaptive immune responses that are influenced by sex hormones. Normally, females develop more robust immune responses against parasites than males. However, most clinical and laboratory studies related to the immune response to malaria do not consider sex as a variable, and relatively few studies have compared the sex-dependent role of 17β-estradiol in this process. In this study, we decreased in vivo the levels of 17β-estradiol by gonadectomy or administered 17β-estradiol to intact or gonadectomized male and female CBA/Ca mice infected with Plasmodium berghei ANKA. Subsequently, we assessed the effects of 17β-estradiol on parasite load; the percentages of different immune cells in the spleen; the plasma levels of antibodies and pro- and anti-inflammatory cytokines; and the mRNA expression levels of cytokine-encoding genes in the brain. The results showed that the administration of 17β-estradiol increased parasitemia and decreased body weight in intact female mice. Moreover, intact females exhibited higher levels of CD8⁺ T cells and lower levels of NK1.1⁺ cells than their male counterparts under the same condition. Gonadectomy increased IFN-γ and decreased TNF-α concentrations only in intact female mice. Additionally, IL-10 levels were higher in intact females than in their male counterparts. Finally, the mRNA expression levels of cytokines coding genes in the brain showed a dimorphic pattern, i.e., gonadectomy upregulated Tnf, Il1b, and Il10 expression in males but not in females. Our findings explain the sexual dimorphism in the immune response to malaria, at least in part, and suggest potential sex-dependent implications for the efficacy of vaccines or drugs targeting malaria.

An Experimental Human Blood-Stage Model for Studying Plasmodium malariae Infection

BACKGROUND

Plasmodium malariae is considered a minor malaria parasite, although its global disease burden is underappreciated. The aim of this study was to develop an induced blood-stage malaria (IBSM) model of P. malariae to study parasite biology, diagnostic assays, and treatment.

METHODS

This clinical trial involved 2 healthy subjects who were intravenously inoculated with cryopreserved P. malariae-infected erythrocytes. Subjects were treated with artemether-lumefantrine after development of clinical symptoms. Prior to antimalarial therapy, mosquito-feeding assays were performed to investigate transmission, and blood samples were collected for rapid diagnostic testing and parasite transcription profiling. Serial blood samples were collected for biomarker analysis.

RESULTS

Both subjects experienced symptoms and signs typical of early malaria. Parasitemia was detected 7 days after inoculation, and parasite concentrations increased until antimalarial treatment was initiated 25 and 21 days after inoculation for subjects 1 and 2 respectively (peak parasitemia levels, 174 182 and 50 291 parasites/mL, respectively). The parasite clearance half-life following artemether-lumefantrine treatment was 6.7 hours. Mosquito transmission was observed for 1 subject, while in vivo parasite transcription and biomarkers were successfully profiled.

CONCLUSIONS

An IBSM model of P. malariae has been successfully developed and may be used to study the biology of, diagnostic testing for, and treatment of this neglected malaria species.

CLINICAL TRIALS REGISTRATION

ACTRN12617000048381.

Increased malaria parasitaemia among adults living with HIV who have discontinued cotrimoxazole prophylaxis in Kitgum district, Uganda

Background

Although WHO recommends cotrimoxazole (CTX) discontinuation among HIV patients who have undergone immune recovery and are living in areas of low prevalence of malaria, some countries including Uganda recommend CTX discontinuation despite having a high malaria burden. We estimated the prevalence and factors associated with malaria parasitaemia among adults living with HIV attending hospital outpatient clinic before and after discontinuation of CTX prophylaxis.

Methods

Between March and April 2019, 599 participants aged 18 years and above, and attending Kitgum hospital HIV clinic in Uganda were enrolled in a cross study. A standardized questionnaire was administered and physical examination conducted. A finger-prick blood sample was collected for identification of malaria parasites by microscopy. The prevalence of parasitaemia was estimated and compared among participants on and those who had discontinued CTX prophylaxis, and factors associated with malaria parasitaemia assessed.

Results

Of the enrolled participants, 27 (4.5%) had malaria parasites and 452 (75.5%) had stopped CTX prophylaxis. Prevalence of malaria parasitaemia was significantly higher in participants who had stopped CTX prophylaxis (5.5% versus 1.4% p = 0.03) and increased with increasing duration since the discontinuation of prophylaxis. Compared to participants taking CTX, those who discontinued prophylaxis for 3–5 months and >5 months were more likely to have malaria parasites (adjusted prevalence ratio (aPR) = 1.64, 95% CI 0.37–7.29, p = 0.51, and aPR = 6.06, 95% CI 1.34–27.3, P = 0.02). Low CD4 count (< 250cells/mm³) was also associated with increased risk of having parasites (aPR = 4.31, 95% CI 2.13–8.73, p <0.001).

Conclusion

People from malaria endemic settings living with HIV have a higher prevalence of malaria parasitaemia following discontinuation of CTX compared to those still on prophylaxis. The risk increased with increasing duration since discontinuation of the prophylaxis. HIV patients should not discontinue CTX prophylaxis in areas of Uganda where the burden of malaria remains high. Other proven malaria control interventions may also be encouraged in HIV patients following discontinuation of CTX prophylaxis.

Histopathological changes in the gastrointestinal tract and systemic alterations triggered by experimental oral infection with Trypanosoma cruzi

Chagas disease, caused by the protozoan Trypanosoma cruzi, is endemic in almost all countries of Latin America. In Brazil, oral infection is becoming the most important mechanism of transmission of the disease in several regions of the country. The gastrointestinal tract is the gateway for the parasite through this route of infection, however, little is known about the involvement of these organs related to oral route. In this sense, the present study evaluated the impact of oral infection on the digestive tract in mice infected by Berenice-78 (Be-78) T. cruzi strain, in comparison with the intraperitoneal route of infection. In this work, the intraperitoneal route group showed a peak of parasitemia similar to the oral route group, however the mortality rate among the orally infected animals was higher when compared to intraperitoneal route. By analyzing the frequency of blood cell populations, differences were mainly observed in CD4⁺ T lymphocytes, and not in CD8^+, presenting an earlier reduction in the number of CD4⁺ T cells, which persisted for a longer period, in the animals of the oral group when compared with the intraperitoneal group. Animals infected by oral route presented a higher tissue parasitism and inflammatory infiltrate in stomach, duodenum and colon on the 28th day after infection. Therefore, these data suggest that oral infection has a different profile of parasitological and immune responses compared to intraperitoneal route, being the oral route more virulent and with greater tissue parasitism in organs of the gastrointestinal tract evaluated during the acute phase.

The clinical spectrum of severe childhood malaria in Eastern Uganda

BACKGROUND

Few recent descriptions of severe childhood malaria have been published from high-transmission regions. In the current study, the clinical epidemiology of severe malaria in Mbale, Eastern Uganda, is described, where the entomological inoculation rate exceeds 100 infective bites per year.

METHODS

A prospective descriptive study was conducted to determine the prevalence, clinical spectrum and outcome of severe Plasmodium falciparum malaria at Mbale Regional Referral Hospital in Eastern Uganda. All children aged 2 months-12 years who presented on Mondays to Fridays between 8.00 am and 5.00 pm from 5th May 2011 until 30th April 2012 were screened for parasitaemia. Clinical and laboratory data were then collected from all P. falciparum positive children with features of WHO-defined severe malaria by use of a standardized proforma.

RESULTS

A total of 10 208 children were screened of which 6582 (64%) had a positive blood film. Of these children, 662 (10%) had clinical features of severe malaria and were consented for the current study. Respiratory distress was the most common severity feature (554; 83.7%), while 365/585 (62.4%) had hyperparasitaemia, 177/662 (26.7%) had clinical jaundice, 169 (25.5%) had severe anaemia, 134/660 (20.2%) had hyperlactataemia (lactate ≥ 5 mmol/L), 93 (14.0%) had passed dark red or black urine, 52 (7.9%) had impaired consciousness and 49/662 (7.4%) had hypoxaemia (oxygen saturations < 90%). In-hospital mortality was 63/662 (9.5%) overall but was higher in children with either cerebral malaria (33.3%) or severe anaemia (19.5%). Factors that were independently associated with mortality on multivariate analysis included severe anaemia [odds ratio (OR) 5.36; 2.16-1.32; P = 0.0002], hyperlactataemia (OR 3.66; 1.72-7.80; P = 0.001), hypoxaemia (OR) 3.64 (95% CI 1.39-9.52; P = 0.008), and hepatomegaly (OR 2.29; 1.29-4.06; P = 0.004). No independent association was found between mortality and either coma or hyperparasitaemia.

CONCLUSIONS

Severe childhood malaria remains common in Eastern Uganda where it continues to be associated with high mortality. An unusually high proportion of children with severe malaria had jaundice or gave a history of having recently passed dark red or black urine, an issue worthy of further investigation.