Geophagy (Soil-eating) in relation to Anemia and Helminth infection among HIV-infected pregnant women in Tanzania

Geophagy, the regular and deliberate consumption of soil, is prevalent among pregnant women in sub-Saharan Africa. We examined the associations of geophagy with anemia and helminth infection among 971 human immunodeficiency virus (HIV)-positive pregnant women in Tanzania. About 29% of pregnant women regularly consumed soil. Occupation, marital status, and gestational age were associated with geophagy. Ascaris lumbricoides infection was associated with the prevalence of geophagy (adjusted-prevalence ratio 1.81; 95% confidence interval [CI] = 1.37-2.40); however, hookworm, Trichuris trichiura, and Strongyloides stercoralis showed no association. Anemia and red blood cell characteristics suggestive of iron deficiency were strongly correlated with geophagy at baseline. In longitudinal analyses, we found evidence suggesting that soil consumption may be associated with an increased risk of anemia (adjusted-relative risk 1.16; 95% CI = 0.98-1.36) and a lower hemoglobin concentration (adjusted-mean difference -3.8 g/L; 95% CI [-7.3, -0.4]). Pregnant women should be informed about the potential risks associated with soil consumption.

Arginine, nitric oxide, carbon monoxide, and endothelial function in severe malaria

PURPOSE OF REVIEW

Parasiticidal therapy of severe falciparum malaria improves outcome, but up to 30% of these patients die despite best therapy. Nitric oxide is protective against severe disease, and both nitric oxide and arginine (the substrate for nitric oxide synthase) are low in clinical malaria. Parasitized red blood cell interactions with endothelium are important in the pathophysiology of malaria. This review describes new information regarding nitric oxide, arginine, carbon monoxide, and endothelial function in malaria.

RECENT FINDINGS

Low arginine, low nitric oxide production, and endothelial dysfunction are common in severe malaria. The degree of hypoargininemia and endothelial dysfunction (measured by reactive hyperemia-peripheral artery tonometry) is proportional to parasite burden and severity of illness. Plasma arginase (an enzyme that catabolizes arginine) is elevated in severe malaria. Administering arginine intravenously reverses hypoargininemia and endothelial dysfunction. The cause(s) of hypoargininemia in malaria is unknown. Carbon monoxide (which shares certain functional properties with nitric oxide) protects against cerebral malaria in mice.

SUMMARY

Replenishment of arginine and restoration of nitric oxide production in clinical malaria should diminish parasitized red blood cells adherence to endothelium and reduce the sequelae of these interactions (e.g. cerebral malaria). Arginine therapy given in addition to conventional antimalaria treatment may prove to be beneficial in severe malaria.

Hookworm-related anaemia among pregnant women: a systematic review

Background and Objectives

Hookworm infection is among the major causes of anaemia in poor communities, but its importance in causing maternal anaemia is poorly understood, and this has hampered effective lobbying for the inclusion of anthelmintic treatment in maternal health packages. We sought to review existing evidence on the role of hookworm as a risk factor for anaemia among pregnant women. We also estimate the number of hookworm infections in pregnant women in sub-Saharan Africa (SSA).

Methods

Structured searches using MEDLINE and EMBASE as well as manual searches of reference lists were conducted, and unpublished data were obtained by contacting authors. Papers were independently reviewed by two authors, and relevant data were extracted. We compared haemoglobin concentration (Hb) according to intensity of hookworm infection and calculated standardised mean differences and 95% confidence intervals. To estimate the number of pregnant women, we used population surfaces and a spatial model of hookworm prevalence.

Findings

One hundred and five reports were screened and 19 were eligible for inclusion: 13 cross-sectional studies, 2 randomised controlled trials, 2 non-randomised treatment trials and 2 observational studies. Comparing uninfected women and women lightly (1–1,999 eggs/gram [epg]) infected with hookworm, the standardised mean difference (SMD) was −0.24 (95% CI: −0.36 to −0.13). The SMD between women heavily (4000+ epg) infected and those lightly infected was −0.57 (95% CI: −0.87 to −0.26). All identified intervention studies showed a benefit of deworming for maternal or child health, but since a variety of outcomes measures were employed, quantitative evaluation was not possible. We estimate that 37.7 million women of reproductive age in SSA are infected with hookworm in 2005 and that approximately 6.9 million pregnant women are infected.

Conclusions

Evidence indicates that increasing hookworm infection intensity is associated with lower haemoglobin levels in pregnant women in poor countries. There are insufficient data to quantify the benefits of deworming, and further studies are warranted. Given that between a quarter and a third of pregnant women in SSA are infected with hookworm and at risk of preventable hookworm-related anaemia, efforts should be made to increase the coverage of anthelmintic treatment among pregnant women.

Anaemia affects large numbers of pregnant women in developing countries and increases their risk of dying during pregnancy and delivering low birth weight babies, who in turn are at increased risk of dying. Human hookworm infection has long been recognized among the major causes of anaemia in poor communities, but understanding of the benefits of the management of hookworm infection in pregnancy has lagged behind the other major causes of maternal anaemia. Low coverage of anthelmintic treatment in maternal health programmes in many countries has been the result. After systematically reviewing the available literature we observed that increasing hookworm infection intensity is associated with lower haemoglobin levels in pregnant women. We also estimate that between a quarter and a third of pregnant women in sub-Saharan Africa are infected with hookworm and at risk of preventable hookworm-related anaemia. However, all identified intervention studies showed a benefit of deworming for maternal or child health and we argue that increased efforts should be made to increase the coverage of anthelmintic treatment among pregnant women.

Role of iron homeostasis in trypanosomiasis-associated anemia

Anemia is a well-established infection-associated immunopathological feature of trypanosomiasis and the degree of the anemia is a reliable indicator of the severity of infection. Since infections with trypanosomes triggers a strong cytokine production and a type I immune response, the trypanosome-elicited anemia may be type I cytokine driven. This type of anemia termed anemia of chronic disease is characterized by an imbalance between erythrophagocytosis and erythropoiesis that is linked to a perturbed iron homeostasis including altered iron recycling by macrophages and iron sequestration. To further unravel the mechanisms underlying trypanosome-elicited anemia the expression profile of genes involved in erythrophagocytosis, uptake of iron-containing complexes and iron homeostasis was performed during the acute and chronic phase of experimental Trypanosoma brucei infections in a murine model. The results suggest that liver-associated erythrophagocytosis mediated by cytokine-activated macrophages (M1 cells) is the most likely main initiating event of aggressive anemia during the acute phase of infection. Persistence of strong type I cytokine production during the chronic phase of infection leads to hyper-activated M1 cells and a more progressive anemia. RT-PCR analysis of liver tissue demonstrates a strong increase of cell surface receptors involved in uptake of RBC and iron-containing compounds. For genes involved in iron processing we found an increase of ferroportin-1 (FPN-1), transferrin (Tf) and ceruloplasmin (CP) only in the acute phase, suggesting that export of iron is hampered in the chronic phase of infection. Our results suggest that in the chronic phase of trypanosomiasis, the iron-processing pathway is skewed towards iron sequestration, as evidenced by increased ferritin expression, while enhanced uptake of RBC/iron-containing compounds is maintained.

Host control of malaria infections: constraints on immune and erythropoeitic response kinetics

The two main agents of human malaria, Plasmodium vivax and Plasmodium falciparum, can induce severe anemia and provoke strong, complex immune reactions. Which dynamical behaviors of host immune and erythropoietic responses would foster control of infection, and which would lead to runaway parasitemia and/or severe anemia? To answer these questions, we developed differential equation models of interacting parasite and red blood cell (RBC) populations modulated by host immune and erythropoietic responses. The model immune responses incorporate both a rapidly responding innate component and a slower-responding, long-term antibody component, with several parasite developmental stages considered as targets for each type of immune response. We found that simulated infections with the highest parasitemia tended to be those with ineffective innate immunity even if antibodies were present. We also compared infections with dyserythropoiesis (reduced RBC production during infection) to those with compensatory erythropoiesis (boosted RBC production) or a fixed basal RBC production rate. Dyserythropoiesis tended to reduce parasitemia slightly but at a cost to the host of aggravating anemia. On the other hand, compensatory erythropoiesis tended to reduce the severity of anemia but with enhanced parasitemia if the innate response was ineffective. For both parasite species, sharp transitions between the schizont and the merozoite stages of development (i.e., with standard deviation in intra-RBC development time <or=2.4 h) were associated with lower parasitemia and less severe anemia. Thus tight synchronization in asexual parasite development might help control parasitemia. Finally, our simulations suggest that P. vivax can induce severe anemia as readily as P. falciparum for the same type of immune response, though P. vivax attacks a much smaller subset of RBCs. Since most P. vivax infections are nonlethal (if debilitating) clinically, this suggests that P. falciparum adaptations for countering or evading immune responses are more effective than those of P. vivax.

Similar cytokine responses and degrees of anemia in patients with Plasmodium falciparum and Plasmodium vivax infections in the Brazilian Amazon region

The mechanisms of malarial anemia induction are poorly understood, but cytokines and autoantibodies are considered to play important roles. This work aimed at evaluating the degree of anemia and the plasmatic profile of the cytokines tumor necrosis factor alpha (TNF-alpha), gamma interferon (IFN-gamma), interleukin-12 (IL-12), migration inhibitory factor (MIF), and IL-10 and the monocyte chemotactic protein-1 (MCP-1) chemokine, as well as evaluating the presence of antibodies directed to components of the normal erythrocyte membrane and to cardiolipin in individuals with malaria from the Brazilian Amazon. No difference was observed in the frequency of anemia between patients infected by Plasmodium vivax and those infected by Plasmodium falciparum, and there was no relationship between the levels of parasitemia and the manifestations of anemia in P. vivax and P. falciparum patients. Significant increases in the concentrations of TNF-alpha, IFN-gamma, MIF, and MCP-1 were observed in patients with P. falciparum and P. vivax malaria, whereas the concentrations of IL-10 was increased only in patients with P. vivax infection. Higher concentrations of IL-12 and IL-10 were observed in the P. falciparum anemic patients, while for TNF-alpha this profile was observed in the nonanemic ones. P. vivax-infected and P. falciparum-infected patients with positive immunoglobulin M (IgM) or IgM and IgG responses, respectively, against blood-stage forms of the parasites had significantly lower hemoglobin levels than did those with negative responses. There was no correlation between the presence of anti-erythrocyte and anti-cardiolipin antibodies and the presence or intensity of the anemia. Our data suggest that in areas of low endemicity and unstable transmission of malaria, P. vivax and P. falciparum infections present similar characteristics in terms of the induction of anemia and cytokine responses.

[Anaemia, iron index status and acute phase proteins in malaria (Abidjan, Côte d'Ivoire)]

Clinical signs of malaria are the combined expression of several biological mechanisms. During this parasite infection, anaemia can be the consequence of several different pathogenic mechanisms. It can be an acute haemolytic anaemia due to a mechanical and immune action of the parasite or an inflammation. Besides, in Africa malaria matches with iron deficiency area. So, malarial anaemia in tropical area can be a characteristic of iron deficiency The purpose of this survey was to define the features of malarial anaemia and elucidate the link of all biological processes involved. A black population living in tropical urban areas, with fever and diagnosed Plasmodium-infection was assessed. Parasitaemia, haemoglobin, hematocrit, average corpuscular volume and average corpuscular haemoglobin were determined. For each patient, iron index status and acute phase protein were assessed with the plasmatic iron, ferritin, haptoglobin, transferrin and C-reactive protein. Regardless of gender and age, the characteristics of malarial anaemia are microcythaemia and hypochromia. Anaemia occurs as frequently as parasitaemia is high. When parasitaemia is low anaemia gets a haemolytic feature. When parasitaemia is high, anaemia gets haemolytic and inflammatory features. Anaemia occurs more often with a good iron index status.

In-hospital morbidity and mortality due to severe malarial anemia in western Kenya

Severe malarial anemia (SMA) is a leading cause of pediatric morbidity, hospitalization, and mortality in sub-Saharan Africa, and yet its contribution to malaria-specific mortality is not well documented. We retrospectively reviewed the clinical records of 1,116 children < 5 years of age admitted to Siaya district hospital, western Kenya, to assess the contribution of SMA to overall in-hospital mortality. Of 1,116 admissions, 86% were under 3 years, 83% had malaria parasitemia, 86% were anemic, 21% were severely anemic, and 20% were transfused. Severe anemia was associated with parasitemia in 85% of the admissions and contributed to 53% of malaria-related deaths. Overall, 83 (7.5%) children died; 66% of those deaths were malaria-related, 12% had severe anemia, and 89% were under 3 years. Transfusion did not lower mortality rates. In areas of high malaria transmission, children below 3 years are a high-risk group for malaria, anemia, blood transfusion, and mortality.

Epidemiology of plasmodium-helminth co-infection in Africa: populations at risk, potential impact on anemia, and prospects for combining control

Human co-infection with Plasmodium falciparum and helminths is ubiquitous throughout Africa, although its public health significance remains a topic for which there are many unknowns. In this review, we adopted an empirical approach to studying the geography and epidemiology of co-infection and associations between patterns of co-infection and hemoglobin in different age groups. Analysis highlights the extensive geographic overlap between P. falciparum and the major human helminth infections in Africa, with the population at coincident risk of infection greatest for hookworm. Age infection profiles indicate that school-age children are at the highest risk of co-infection, and re-analysis of existing data suggests that co-infection with P. falciparum and hookworm has an additive impact on hemoglobin, exacerbating anemia-related malarial disease burden. We suggest that both school-age children and pregnant women--groups which have the highest risk of anemia--would benefit from an integrated approach to malaria and helminth control.

The effect of HIV on morbidity and mortality in children with severe malarial anaemia

BACKGROUND

Malaria and HIV are common causes of mortality in sub-Saharan Africa. The effect of HIV infection on morbidity and mortality in children with severe malarial anaemia was assessed.

METHODS

Children <5 years old were followed as part of a prospective cohort study to assess the transfusion-associated transmission of blood-borne pathogens at Mulago Hospital, Kampala, Uganda. All children were hospitalized with a diagnosis of severe malarial anaemia requiring blood transfusion. Survival to different time points post-transfusion was compared between HIV-infected and uninfected children. Generalized estimating equations were used to analyse repeated measurement outcomes of morbidity, adjusting for confounders.

FINDINGS

Of 847 children, 78 (9.2%) were HIV-infected. Median follow-up time was 162 days (inter-quartile range: 111, 169). HIV-infected children were more likely to die within 7 days (Hazard ratio [HR] = 2.86, 95% Confidence interval [CI] 1.30-6.29, P = 0.009) and within 28 days (HR = 3.70, 95% CI 1.91-7.17, P < 0.001) of an episode of severe malarial anaemia, and were more likely to die in the 6 months post-transfusion (HR = 5.70, 95% CI 3.54-9.16, P < 0.001) compared to HIV-uninfected children. HIV-infected children had more frequent re-admissions due to malaria within 28 days (Incidence rate ratio (IRR) = 3.74, 95% CI 1.41-9.90, P = 0.008) and within 6 months (IRR = 2.66, 95% CI 1.17 - 6.07, P = 0.02) post-transfusion than HIV-uninfected children.

CONCLUSION

HIV-infected children with severe malarial anaemia suffered higher all-cause mortality and malaria-related mortality than HIV-uninfected children. Children with HIV and malaria should receive aggressive treatment and further evaluation of their HIV disease, particularly with regard to cotrimoxazole prophylaxis and antiretroviral therapy.

Effects of malaria heme products on red blood cell deformability

In falciparum malaria, the deformability of the entire erythrocyte population is reduced in proportion to disease severity, and this compromises microcirculatory blood flow through vessels partially obstructed by cytoadherent parasitized erythrocytes. The cause of rigidity of uninfected erythrocytes in not known but could be mediated by malaria heme products. In this study, we show that red blood cell deformability (RBC-D), measured by laser-assisted optical rotational cell analyzer, decreased in a dose-dependent manner after incubation with hemin and hydrogen peroxide but not with hemoglobin or beta-hematin. Hemin also reduced mean red cell volume. Albumin decreased and N-acetylcysteine (NAC) both prevented and reversed rigidity induced by hemin. Hemin-induced oxidative damage of the membrane seems to be a more important contributor to pathology than cell shrinkage because the antioxidant NAC restored RBC-D but not red blood cell volume. The findings suggest novel approaches to the treatment of potentially lethal malaria.

Anemia and antibodies to the 19-kDa fragment of MSP1 during Plasmodium falciparum infection in Aotus monkeys

To determine whether antibodies to the 19-kDa fragment of merozoite surface protein 1 (MSP1(19)) help to control blood-stage Plasmodium falciparum infection, we performed a rechallenge experiment of previously infected Aotus monkeys. Monkeys previously exposed to the FVO strain of P. falciparum that did or did not develop high antibody titers to MSP1(19) and malaria-naïve monkeys were challenged with erythrocytes infected with the same strain. Prepatent periods were prolonged in previously infected monkeys compared with malaria-naïve monkeys. Previously infected monkeys with preexisting anti-MSP1(19) antibodies showed low peak parasitemias that cleared spontaneously. Previously infected monkeys that had no or low levels of pre-existing anti-MSP1(19) antibodies also showed low peak parasitemias, but because of low hematocrits, all of these animals required treatment with mefloquine. All previously malaria-naïve animals were treated because of high parasitemias. The results of this study suggest that antibody to the 19-kDa carboxy-terminal fragment of MSP1 plays a role in preventing the development of anemia, an important complication often associated with malaria.

Maternal anaemia as an indicator for monitoring malaria control in pregnancy in sub-Saharan Africa

DESIGN

Malarial anaemia is a major problem in many developing countries and often occurs more frequently in first pregnancies, as primigravidae are more susceptible to Plasmodium falciparum malaria and are at excess risk of malarial anaemia.

OBJECTIVE AND METHODS

To analyse the excess risk of anaemia in primigravidae as a potential indicator of malaria control and exposure in pregnant women living in sub-Saharan Africa. The sensitivity, specificity and predictive values for anaemia in first compared with later pregnancies are calculated for 27 studies from malarious and 7 studies from nonmalarious areas.

SETTING

Surveys of pregnancy anaemia reported for highly malarious and nonmalarious areas.

RESULTS

In malarious areas, the weighted odds ratio for excess anaemia (haemoglobin [Hb] <11 g/dl) in primigravidae compared with multigravidae for all studies was 1.34 (95% CI 1.14-1.58). At an Hb cutoff below 8 g/dl, the weighted odds ratio was 1.79 (95% CI 1.52-2.10). In nonmalarious areas, there was no increased risk of anaemia in primigravidae with Hb below 11 g/dl (OR 0.80; 95% CI 0.63-1.90) or below 8 g/dl (OR 0.82, 95% CI 0.51-1.28).

CONCLUSIONS

In view of the consistency of results across highly malarious areas compared with nonmalarious areas, maternal anaemia has the potential to be used for surveillance of malaria control in pregnancy. Based on the analysis, an anaemia nomogram is developed for use as a surveillance indicator in malarious areas in sub-Saharan Africa.

Natural regulatory (CD4+CD25+FOXP+) T cells control the production of pro-inflammatory cytokines during Plasmodium chabaudi adami infection and do not contribute to immune evasion

Different functions have been attributed to natural regulatory CD4+CD25+FOXP+ (Treg) cells during malaria infection. Herein, we assessed the role for Treg cells during infections with lethal (DS) and non-lethal (DK) Plasmodium chabaudi adami parasites, comparing the levels of parasitemia, inflammation and anaemia. Independent of parasite virulence, the population of splenic Treg cells expanded during infection, and the absolute numbers of activated CD69+ Treg cells were higher in DS-infected mice. In vivo depletion of CD25+ T cells, which eliminated 80% of CD4+FOXP3+CD25+ T cells and 60-70% of CD4+FOXP3+ T cells, significantly decreased the number of CD69+ Treg cells in mice with lethal malaria. As a result, higher parasite burden and morbidity were measured in the latter, whereas the kinetics of infection with non-lethal parasites remained unaffected. In the absence of Treg cells, parasite-specific IFN-gamma responses by CD4+ T cells increased significantly, both in mice with lethal and non-lethal infections, whereas IL-2 production was only stimulated in mice with non-lethal malaria. Following the depletion of CD25+ T cells, the production of IL-10 by CD90(-) cells was also enhanced in infected mice. Interestingly, a potent induction of TNF-alpha and IFN-gamma production by CD4+ and CD90(-) lymphocytes was measured in DS-infected mice, which also suffered severe anaemia earlier than non-depleted infected controls. Taken together, our data suggest that the expansion and activation of natural Treg cells represent a counter-regulatory response to the overwhelming inflammation associated with lethal P.c. adami. This response to infection involves TH1 lymphocytes as well as cells from the innate immune system.

Recombinant human IFN-alpha inhibits cerebral malaria and reduces parasite burden in mice

Most C57BL/6 mice infected i.p. with Plasmodium berghei ANKA (PbA) die between 7 and 14 days with neurologic signs, and the remainder die later (>15 days) with severe anemia. Daily i.p. injections of a recombinant human IFN-alpha (active on mouse cells) prevented death by cerebral malaria (87% deaths in the control mice vs 6% in IFN-alpha-treated mice). The mechanisms of this IFN-alpha protective effect were multiple. IFN-alpha-treated, PbA-infected mice showed 1) a marked decrease in the number of PbA parasites in the blood mediated by IFN-gamma, 2) less sequestered parasites in cerebral vessels, 3) reduced up-regulation of ICAM-1 expression in brain endothelial cells, 4) milder rise of blood levels of TNF, 5) increased levels of IFN-gamma in the blood resulting from an increased production by splenic CD8+ T cells, and 6) fewer leukocytes (especially CD8+ T cells) sequestered in cerebral vessels. On the other hand, IFN-alpha treatment did not affect the marked anemia observed in PbA-infected mice. Survival time in IFN-alpha-treated mice was further increased by performing three blood transfusions over consecutive days.

Associations between mild-to-moderate anaemia in pregnancy and helminth, malaria and HIV infection in Entebbe, Uganda

It is suggested that helminths, particularly hookworm and schistosomiasis, may be important causes of anaemia in pregnancy. We assessed the associations between mild-to-moderate anaemia (haemoglobin >8.0 g/dl and <11.2 g/dl) and helminths, malaria and HIV among 2507 otherwise healthy pregnant women at enrolment to a trial of deworming in pregnancy in Entebbe, Uganda. The prevalence of anaemia was 39.7%. The prevalence of hookworm was 44.5%, Mansonella perstans 21.3%, Schistosoma mansoni 18.3%, Strongyloides 12.3%, Trichuris 9.1%, Ascaris 2.3%, asymptomatic Plasmodium falciparum parasitaemia 10.9% and HIV 11.9%. Anaemia showed little association with the presence of any helminth, but showed a strong association with malaria (adjusted odds ratio (AOR) 3.22, 95% CI 2.43–4.26) and HIV (AOR 2.46, 95% CI 1.90–3.19). There was a weak association between anaemia and increasing hookworm infection intensity. Thus, although highly prevalent, helminths showed little association with mild-to-moderate anaemia in this population, but HIV and malaria both showed a strong association. This result may relate to relatively good nutrition and low helminth infection intensity. These findings are pertinent to estimating the disease burden of helminths and other infections in pregnancy. [Clinical Trial No. ISRCTN32849447]

Intermittent preventive treatment of malaria in pregnancy: a community-based delivery system and its effect on parasitemia, anemia and low birth weight in Uganda

OBJECTIVE

The main objective of the study was to assess the impact of a community-based delivery system of intermittent preventive treatment (IPT) for malaria in pregnancy with sulfadoxine-pyrimethamine (SP) on access, parasitemia, anemia and low birth weight as primary outcome measures.

METHODS

A study was designed to test the community-based delivery system of IPT through traditional birth attendants (TBAs), drug-shop vendors (DSVs), community reproductive health workers (CRHWs) and adolescent peer mobilizers (APMs), and to compare these with IPT at health units in an area of high malaria transmission - Mukono District, Uganda.

RESULTS

Two thousand seven hundred and eighty-five pregnant women participated in the study. The majority of the women (92.4%) at the community-based approaches received their first dose of IPT during their second trimester compared to 76.1% at health units (p<0.0001). At both health units and the community-based approaches, IPT increased mean hemoglobin by 6.7% (p<0.0001) for all parities and by 10.2% among primigravidae. IPT reduced the prevalence of severe anemia from 5.7% to 3.1% (p<0.04). The prevalence of parasitemia was reduced from 24.5% to 16.1% (p<0.001), and parasite density reduced significantly (p<0.02) after the first dose and remained stable with the second dose. Overall the proportion of low birth weight was 6.3% (8.3% at health units versus 6.0% at the community-based approaches, p<0.03) highlighting the importance of access and adherence to IPT. This intervention was acceptable to 89.6% of the women at the community-based approaches intending to use IPT in the future, while 48.1% of them had recommended it to other women.

CONCLUSIONS

The community-based approaches increased access and adherence to IPT with an effect on anemia, severe anemia, parasitemia and low birth weight. However the reduced effect of IPT on parasitemia points to drug resistance with SP and this requires further evaluation; research into the identification of other more efficacious drugs for malaria prevention in pregnancy is also required.

Dynamics of anemia progression and recovery in Babesia bigemina infection is unrelated to initiating parasite burden

To be informative, immunization-and-challenge experiments in support of vaccine development rely on host responses that enable distinctions to be made in the responses of immunized and non-immunized animals to infectious challenge. It is therefore important that animals be challenged with standardized infectious doses that allow such distinctions to be made. We report here the results of a challenge titration experiment in which cattle were challenged with Babesia bigemina, at dosages ranging over six orders of magnitude. No significant dose-dependent differences were observed in the maximum fever attained, duration of fever, minimum hematocrit reached, kinetics with which anemia developed or was resolved, or animal weight gain. Significant differences were noted only in the length of time post-infection required to initiate fever, reach maximum fever, and attain maximum reduction in hematocrit. These results suggest that, in the absence of further supporting evidence, it is not possible to conclude any direct anti-parasite effects from reductions in maximum fever or hematocrit drop during B. bigemina immunization-and-challenge experiments. However, lengthening of the time to reduction in hematocrit may be a useful indicator of overt suppression of the challenge inoculum.

Gamma interferon suppresses erythropoiesis via interleukin-15

Impaired erythropoiesis causes anemia during genetic disorders, chronic disease, and infection. In studies of the underlying mechanisms researchers have increasingly focused on gamma interferon (IFN-gamma). Here, we identified a previously unrecognized role for interleukin-15 (IL-15) in red blood cell homeostasis and demonstrated that IFN-gamma and signal transducer and activator of transcription protein 1-dependent pathways up-regulate expression of IL-15 in vivo. These findings identified new therapeutic targets for anemia.

Phenotypic features of circulating leucocytes as immunological markers for clinical status and bone marrow parasite density in dogs naturally infected by Leishmania chagasi

Canine visceral leishmaniasis (CVL) manifests itself as a broad clinical spectrum ranging from asymptomatic infection to patent severe disease. Despite relevant findings suggesting changes on lymphocytes subsets regarding the CVL clinical forms, it still remains to be elucidated whether a distinct phenotypic profile would be correlated with degree of tissue parasite density. Herein, we have assessed the correlation between the clinical status as well as the impact of bone marrow parasite density on the phenotypic profile of peripheral blood leucocytes in 40 Brazilian dogs naturally infected by Leishmania chagasi. Our major findings describe the lower frequency of B cells and monocytes as the most important markers of severe CVL. Our main statistically significant findings reveal that the CD8(+) T cell subset reflects most accurately both the clinical status and the overall bone marrow parasite density, as increased levels of CD8(+) lymphocytes appeared as the major phenotypic feature of asymptomatic disease and dogs bearing a low parasite load. Moreover, enhanced major histocompatibility complex (MHC)-II density as well as a higher CD45RB/CD45RA expression index seems to represent a key element to control disease morbidity. The association between clinical status, bone marrow parasitism and CD8(+) T cells re-emphasizes the role of the T cell-mediated immune response in the resistance mechanisms during ongoing CVL. Higher levels of circulating T lymphocytes (both CD4(+) and CD8(+) T cells) and lower MHC-II expression by peripheral blood lymphocytes seem to be the key for the effective immunological response, a hallmark of asymptomatic CVL.

The epidemiology of malaria in adults in a rural area of southern Mozambique

Background

Epidemiological studies of malaria in adults who live in malaria endemic areas are scarce. More attention to the natural history of malaria affecting adults is needed to understand the dynamics of malaria infection and its interaction with the immune system. The present study was undertaken to investigate the clinical, parasitological and haematological status of adults exposed to malaria, and to characterize parasites in these individuals who progressively acquire protective immunity.

Methods

A cross-sectional survey of 249 adults was conducted in a malaria endemic area of Mozambique. Clinical, parasitological and haematological status of the study population was recorded. Sub-microscopic infections and multiplicity of infections were investigated using polymerase chain reaction (PCR) and restriction fragment length polymorphism of Plasmodium falciparum merozoite surface protein 2 (msp2).

Results

Prevalence of P. falciparum infection by microscopy (14%) and PCR (42%) decreased progressively during adulthood, in parallel with an increase in the prevalence of sub-microscopic infections. Anaemia was only related to parasitaemia as detected by PCR. Multiplicity of infection decreased with age and was higher in subjects with high P. falciparum densities, highlighting density-dependent constraints upon the PCR technique.

Conclusion

Adults of Manhiça progressively develop non-sterile, protective immunity against P. falciparum malaria. The method of parasite detection has a significant effect on the observed natural history of malaria infections. A more sensitive definition of malaria in adults should be formulated, considering symptoms such as diarrhoea, shivering and headache, combined with the presence of parasitaemia.

Malaria signs and infection rate among asymptomatic schoolchildren in Hajr Valley, Yemen

This study recorded malaria signs and the rate of parasitaemia among asymptomatic schoolchildren in Hajr valley, Hadhramout governorate, Yemen. Tests were made for malaria parasites and anaemia in 469 randomly selected primary-school children aged 6-11 years, together with clinical examination to determine spleen size, and interviews to study sociodemographic factors. Of the children, 12.8% had positive malaria blood films and 11.3% had spleen enlargement. There were significant associations between malaria infection, anaemia and splenomegaly and fever. Children with malaria parasitaemia were more often absent from school.