Risk factors for anemia in children under 6 years of age in Ethiopia: analysis of the data from the cross-sectional Malaria IndicatorSurvey, 2007.

BACKGROUND: Malaria is a leading cause of morbidity in Ethiopia. However, its transmission varies in both space and time, and large areas of the country are hypoendemic and epidemic-prone. The Ethiopia National Malaria Indicator Survey 2007 is a cross-sectional, nationally-representative household survey. The objective of the analyses presented here were to use the survey's data to identify factors associated with anemia presence in children under 6 years of age (U6); specifically, investigate the association between malaria and anemia; and discuss using anemia as a malaria proxy biomarker in the Ethiopian hypo-endemic transmission setting. METHODS: The survey sampled 4185 households in 347 enumeration areas ≤2500 m above sea level. Primary outcome was increasing anemia severity in sampled children: no anemia (Hb: ≥11g/dl); mild anemia (Hb: ≥8g/dl and <11g/dl); and moderate-severe anemia (Hb: <8g/dl). Secondary outcomes were positive malaria rapid diagnostic test (RDT) or blood slide microscopy. RESULTS: The analysis included 6054 (92.0%) children U6 in 3962 households. The proportion of children with no anemia, mild anemia, and moderate-severe anemia was 63.6%, 31.3%, and 5.1%, respectively. The overall prevalence of anemia (Hb <11g/dl) was 36.4% (95% CI 34.4-38.4). Factors independently associated with reduced relative odds of anemia categories were age (OR=0.7, 95% CI 0.7-0.7) and female sex (OR=0.9, 95% CI 0.8-1.0); malaria RDT positivity was associated with increased relative odds of a more severe anemia category (OR=5.8, 95% CI 3.7-9.2). CONCLUSIONS: We conclude that at altitudes ≤2500 m malaria appears to be a significant risk factor for anemia; potentially anemia could be used as a useful proxy biomarker for malaria and its control in Ethiopia.

Rapid Increase in Ownership and Use of Long-Lasting Insecticidal Nets and Decrease in Prevalence of Malaria in Three Regional States of Ethiopia (2006-2007)

Following recent large scale-up of malaria control interventions in Ethiopia; this study aimed to compare ownership and use of long-lasting insecticidal nets (LLIN); and the change in malaria prevalence using two population-based household surveys in three regions of the country. Each survey used multistage cluster random sampling with 25 households per cluster. Household net ownership tripled from 19.6in 2006 to 68.4in 2007; with mean LLIN per household increasing from 0.3 to 1.2. Net use overall more than doubled from 15.3to 34.5; but in households owning LLIN; use declined from 71.7to 48.3. Parasitemia declined from 4.1to 0.4. Large scale-up of net ownership over a short period of time was possible. However; a large increase in net ownership was not necessarily mirrored directly by increased net use. Better targeting of nets to malaria-risk areas and sustained behavioural change communication are needed to increase and maintain net use

Productivity of natural and artificial containers for Aedes polynesiensis and Aedes aegypti in four American Samoan villages.

Six mosquito species were identified in a survey of containers associated with 347 households in four villages in American Samoa. Aedes polynesiensis Marks (Diptera: Culicidae) and Aedes aegypti (L) were the most abundant species, representing 57% and 29% of the mosquitoes identified. Culex quinquefasciatus (Say), Culex annulirostris (Skuse), Aedes oceanicus (Belkin) and Toxorhynchites amboinensis (Doleschall) were also found. Aedes aegypti and Ae. polynesiensis showed distinct differences in their use of containers, preferring large and small containers, respectively. By contrast with previous studies, Ae. polynesiensis utilized domestic and natural containers with equal frequency, whereas Ae. aegypti continued to be found predominantly in domestic containers. Only 15% of containers holding immature mosquitoes included pupae and fewer than 10 Aedes spp. pupae were found in most containers with pupae. An estimated 2289 Ae. polynesiensis and 1640 Ae. aegypti pupae were found in 2258 containers. The presence of both species in the same container did not affect the mean density of either species for larvae or pupae. Glass jars, leaf axils, tree holes and seashells produced few Aedes spp. pupae in any of the study villages. Overall, 75% of Ae. polynesiensis pupae were found in buckets, ice-cream containers and tyres, with <7% being produced in natural containers, whereas 82% of Ae. aegypti pupae were found in 44-gallon (US) drums ( approximately 166L), buckets and tyres. Source reduction efforts targeting these container types may yield significant reductions in both Ae. polynesiensis and Ae. aegypti populations in American Samoa.

Lack of association between early childhood immunizations and beta-cell autoimmunity.

OBJECTIVE: To determine whether early childhood immunization history affects the risk of developing the beta-cell autoimmunity that precedes type 1 diabetes. RESEARCH DESIGN AND METHODS: This article describes a case-control study whose participants were 317 children aged < or = 12 years who have a first-degree relative with type 1 diabetes. The children were enrolled in a prospective cohort study of the etiology of beta-cell autoimmunity, the Diabetes Autoimmunity Study in the Young, in Denver, Colorado. The main outcome measure was beta-cell autoimmunity as determined by persistent autoantibodies against insulin, GAD, or islet cell antibody (IA-2) 512. The number of cases with beta-cell autoimmunity was 25, and the number of control subjects (the remainder of the cohort) was 292. RESULTS: There was no difference between cases and control subjects in the proportion receiving hepatitis B (HBV), Haemophilus influenzae b (Hib), polio, or diphtheria tetanus pertussis (DTP) vaccines before 9 months of age; in the proportion receiving HBV at birth rather than later; or in the median age at first HBV, Hib, polio, or DTP vaccination. CONCLUSIONS: The results suggest that changing the early childhood immunization schedule would not affect the risk of developing beta-cell autoimmunity or type 1 diabetes.

Comparison of the cost-effectiveness of vaccines and insecticide impregnation of mosquito nets for the prevention of malaria.

The cost-effectiveness of two different methods of prevention of morbidity and mortality due to Plasmodium falciparum malaria, vaccination and impregnation of mosquito nets with permethrin, was compared. The analysis was performed with reference to the cohort of all children born in The Gambia in 1990 and protected for 5 years, using estimates of costs from studies in The Gambia. The vaccine was assumed to be given in three doses before the age of 6 months, through the Expanded Programme of Immunization, and to remain effective up to the age of 5 years. The bednets were assumed to be impregnated at 6-monthly intervals over the 5-year period. The expected number of deaths and attacks due to P. falciparum in the first 5 years of the 1990 cohort's lives were estimated from published literature. The numbers of deaths and attacks averted by the two strategies were then estimated by decision analysis, using the best estimates of effectiveness available in the literature. The vaccine strategy would have averted an estimated 743 deaths and 50,502 malaria attacks, whereas the net impregnation would have averted 1537 deaths and 69,415 attacks. The estimated cost per death averted was U.S. $252 for the vaccine and U.S. $711 for net impregnation. The estimated cost per P. falciparum attack averted was U.S. $3.71 for the vaccine and U.S. $15.75 for net impregnation. Sensitivity analysis, examining the effect of varying the vaccine cost or insecticide cost, the efficacy of the vaccine or net impregnation, and the percentage coverage of the population, confirmed the greater cost-effectiveness of the vaccine strategy for either of the outcomes examined under the conditions of the model. However, limitations on the absolute number of deaths and malaria attacks which can averted by currently available vaccines demonstrate that a vaccine of higher efficacy would be highly desirable.

The role of enteroviral infections in the development of IDDM: limitations of current approaches.

Enteroviruses have been examined for their possible role in the etiology of IDDM for nearly 40 years, yet the evidence remains inconclusive. The mechanism of acute cytolytic infection of beta-cells, proposed by earlier studies, appears to be incompatible with the long preclinical period of autoimmunity preceding IDDM. Advances in molecular biology have improved our understanding of enteroviral biology and of potential alternative pathogenic mechanisms through which enteroviruses may cause diabetes. The focus of future human studies will likely shift from people with IDDM to those with prediabetic autoimmunity to determine whether acute enteroviral infections can promote progression from autoimmunity to overt diabetes. We propose that such studies use assays to detect enteroviral RNA, in addition to IgM serology. RNA assays can overcome sensitivity and type-specificity limitations of IgM assays as well as identify diabetogenic strains of enteroviruses, if such exist. Evaluation of the role of enteroviruses in triggering beta-cell autoimmunity in humans will require large prospective studies of young children. The Diabetes Autoimmunity Study in the Young--one of very few such studies currently underway--is focusing on potential interactions between HLA class II genes and enteroviral infections. Future studies will likely examine interactions between viral infections and non-HLA IDDM candidate genes, including those that may determine beta-cell tropism of candidate viruses.

The value of vector-based estimates of malaria transmission.

Estimating malaria transmission in the human is fraught with problems of reconciling clinical illness with parasitological status. It follows that there is a role for entomological assessments as an independent outcome variable and as a process indicator. Advances in DNA technology have expanded our capacity to identify vectors rapidly, while immunoassays allow the inoculation rate to be measured simultaneously in a number of villages with a precision 3-fold greater than measurements of vectorial capacity. The rapid specific identification of parasites in vectors has been utilized to estimate survivorship in mosquitoes per extrinsic incubation period (EIP), circumventing the need for estimates of survivorship per feeding cycle, lengths of feeding cycles or the length of the EIP. While lack of accuracy does not universally preclude the utility of estimates of the components of vectorial capacity in serving as relative estimates of transmission, particularly as process indicators, more accurate estimates of these parameters, particularly for density-dependent variables, may diminish the associated bias in their measurement. When this is accomplished, we will come closer to obtaining true rather than relative estimates of transmission.

Antibody detection ELISAS for malaria diagnosis.

Parasite extracts of Plasmodium falciparum and P. chabaudi and three synthetic peptides from the P. falciparum MSA2 merozoite antigen were tested for suitability as antigens in an antibody detection ELISA using sera from malaria patients in Brisbane. The P. chabaudi extract was superior to P. falciparum extract for detecting P. vivax cases, while for P. falciparum cases the two parasite extracts were equivalent. Single peptide antigens were generally less sensitive than parasite extracts; however, peptides G3 and G7 were more sensitive than parasite extracts in detecting first attacks of P. vivax. Examination of isotype specific responses demonstrated that this may be explained by higher IgG responses to these peptides in first than in subsequent P. vivax attacks. Because of the differing antibody specificities in primary and secondary P. falciparum and P. vivax cases, the best sensitivity was achieved by using the combined results of assays with three antigens: P. chabaudi, peptide G3 and peptide G7. The combined sensitivity was 77.1% for P. falciparum and 88.6% for P. vivax acute cases with 91.1% specificity.

Human antibody responses to epitopes on the Plasmodium falciparum gametocyte antigen PFS 48/45 and their relationship to infectivity of gametocyte carriers.

Antibodies in human sera recognizing epitopes I, IIa, III, and IV on the Plasmodium falciparum gametocyte antigen Pfs 48/45 have been investigated by competitive enzyme-linked immunosorbent assay. More than one-third of the residents of three villages in Madang, Papua New Guinea responded to epitopes I, IIa and III, with little variation by village or with time. There was a bimodal distribution of positive sera by age, with the highest proportion of responders in the 5-9- and greater than 20-year-old age groups. The data suggest a lower prevalence of antibodies against epitopes IIa and III in P. falciparum gametocyte carriers than in non-carriers. Enhancement of binding of monoclonal antibodies to epitopes IIa and III was also observed more frequently with sera from gametocyte carriers. Sera from gametocyte carriers in Papua New Guinea and Thailand, whose infectivity to mosquitoes had been tested, were used to examine the relationship between recognition of particular epitopes and infectivity. There was a significant association between lack of infectivity of P. falciparum gametocyte carriers and recognition of epitope IIa on Pfs 48/45 by antibodies in their sera.

Antibody responses to Plasmodium falciparum gametocyte antigens during and after malaria attacks in schoolchildren from Madang, Papua New Guinea.

Sera from 49 school children in Madang, Papua New Guinea with malaria and follow-up sera from 40 of these cases were tested by competitive ELISA for antibodies capable of inhibiting binding of eight monoclonal antibodies (MoAbs) to Plasmodium falciparum gametocytes. The proportion of sera inhibiting each MoAb ranged from 31.2% to 85.7%. At follow-up, the proportion of inhibitory sera decreased for 3 MoAbs, did not change significantly for 4 MoAbs and increased for one MoAb. When sera were grouped according to whether the follow-up blood slide was positive or negative, further trends emerged for MoAbs against the gamete surface antigen Pfs 48/45. Antibody levels to the IA3-B8 epitope decreased in follow-up positive cases, but remained unchanged for follow-up negative cases. The converse was observed for the IIC5-B10 epitope with an increase of antibody in follow-up positive cases and no change in the negative cases. Amount of antibody to the 3G12/58 epitope decreased when the follow-up was negative but not when it was positive. Increase in antibody to the 3E12/58 epitope occurred at the follow-up sample irrespective of the blood slide result. Thus four distinct patterns of longitudinal antibody response were observed against four epitopes on the same molecule.

Developmental aspects of the primary process.

The structural-developmental view of primary process initially proposed by Holt (1967) defines primary process as a special system of processing information in the service of "synthetic necessity." Rather than being an archaic, chaotic mode of ideation, primary process follows an independent line of development with specific organizational and synthesizing properties. Vignettes from three phases of the treatment of a severely disturbed child provide clinical evidence to support this viewpoint.

Properties of epitopes of Pfs 48/45, a target of transmission blocking monoclonal antibodies, on gametes of different isolates of Plasmodium falciparum.

We have studied the properties of epitopes on Plasmodium falciparum gamete surface protein Pfs 48/45, a target antigen of malaria transmission blocking antibodies. Using a two site immunoradiometric assay we have defined three spacially separate, non-repeated, epitope regions on the peptides representing this antigen. Epitope region I is a target of monoclonal antibodies (MoAbs) which strongly suppress infectivity of gametocytes of P. falciparum to mosquitoes; the effect is complement independent and is mediated as effectively by the monovalent Fab fragments as by intact MoAb. Epitope region II consists of two spacially close subregions, IIa and IIb; variant forms of epitopes IIa and IIb occurred in different isolates of P. falciparum. Epitope region III also showed slight structural modification between isolates. MoAbs against regions II or III were relatively ineffective in suppressing gametocyte infectivity compared to MoAbs against region I. However, certain combinations of MoAbs against regions II and III together acted synergistically to suppress infectivity to mosquitoes. All these epitopes failed to react with MoAb when the antigen was presented in reduced form. A fourth epitope, however, was identified which reacted strongly with MoAb when the antigen was presented in reduced form. The MoAb against this epitope had no effect on the infectivity of gametocytes of P. falciparum to mosquitoes.

Variations in malaria transmission rates are not related to anopheline survivorship per feeding cycle.

Anopheline survivorship, vectorial capacity, and mosquito infection probability estimates from mosquito infection rates were determined 4 times in 1 year in a Papua New Guinea village. Estimates of survivorship over the length of the extrinsic incubation period differed significantly during the year. However, survivorship per feeding cycle, individual mosquito vectorial capacity, and mosquito infection probability did not vary significantly. Estimates of these parameters were then compared to estimates of survivorship, individual vectorial capacity, and mosquito infection probability in mosquito populations in other villages in the study area. Since survivorship per feeding cycle did not vary significantly among the mosquito populations in these villages, changes in malaria transmission potential can be better gauged from estimates of survivorship over the length of the extrinsic incubation period. However, as measurements of relative inoculation rates are easier to perform and have been related to parasite prevalences in children in this area, estimates of inoculation rates are a preferred option for estimating malaria transmission in the Madang area of Papua New Guinea.

The primary antibody response of malaria patients to Plasmodium falciparum sexual stage antigens which are potential transmission blocking vaccine candidates.

Thirty serum samples collected from adult patients attending the Hospital for Tropical Diseases, London, with P. falciparum malaria, were studied. Sera were screened by indirect immunofluorescence for anti-gametocyte antibodies. Twelve of the serum samples taken from 14 patients with primary infections were found to have both IgM and IgG antibodies to gametocyte antigens and total Ig titres comparable with those of patients who had had previous malaria attacks. Sera of individuals from hyperendemic areas have been found to immunoprecipitate the 230 and 48/45 kD gametocyte surface antigens which are known targets of transmission blocking antibodies. To investigate the epitope specificity of the serum samples from our adult patients, competitive ELISAs with 3 monoclonal antibodies (MAbs) that block transmission and recognize different epitopes on the 48/45 Kd antigen, were carried out. Specific antibodies for these epitopes were found in 60% of the sera while nearly a third were able to inhibit the binding of at least two MAbs.

The prevalence of naturally acquired multiple infections of Wuchereria bancrofti and human malarias in anophelines.

Malaria and filaria infection rates were determined for anopheline mosquitoes collected whilst biting and resting in village houses in Papua New Guinea. The number of anophelines infected with both parasites was greater than expected from the infection rates of each parasite and this difference was significant in resting collections. The excess of multiply infected mosquitoes is probably a result of a vector population composed of individuals with differing numbers of opportunities to become infected. Malaria-positive Anopheles punctulatus from resting catches had a significantly greater number of Stage 3 Wuchereria bancrofti larvae than malaria-negative mosquitoes. However, multiply infected mosquitoes appear to suffer greater mortality than non-infected or singly infected mosquitoes when the filarial worm reaches the third stage. Any potential increase in transmission resulting from multiple infections is thereby offset by a greater mortality rate in these mosquitoes.

High frequency of antibody response to Plasmodium falciparum gametocyte antigens during acute malaria infections in Papua New Guinea highlanders.

Sera from 62 adult Papua New Guinea highlanders with suspected acute malaria were tested by competitive ELISA for the presence of antibodies capable of inhibiting binding of 8 monoclonal antibodies (Mabs) directed against epitopes on gametocytes of Plasmodium falciparum. Between 33% and 72% of the malaria cases were inhibitory, depending on the Mab. There was no difference between the proportion of persons with P. falciparum (asexuals or gametocytes) and P. vivax whose sera inhibited Mab binding, but all 3 categories had a significantly higher proportion of inhibitors than persons who were malaria negative. The amount of gametocyte antibody recognizing epitopes on Pfs 48/45 and Pfs 230 increased with increasing numbers of previous malaria episodes. The proportion of sera from these relatively nonimmune adults which had gamete antibodies was similar to the proportion seen in sera from a highly endemic area, suggesting that antibody responses to these epitopes are a part of the initial response observed after a limited number of malaria episodes.

Association between HLA type and antibody response to malaria sporozoite and gametocyte epitopes is not evident in immune Papua New Guineans.

HLA-A,B,C and DR types were determined for 46 adults living in the Madang area of Papua New Guinea. Sera from these individuals were tested by ELISA for antibodies against: (i) sonicated schizont extract of Plasmodium falciparum; (ii) circumsporozoite repeat regions of P. falciparum and P. vivax; and (iii) epitopes on the 230 and 48/45 kD gametocyte antigens of P. falciparum. All sera were from highly immune individuals and reacted strongly to the schizont antigen. The proportions responding to circumsporozoite repeat regions were 60.7% and 23.9% for P. falciparum and P. vivax, respectively. Between 32.6 and 47.8% of adults responded to each gametocyte epitope as assessed by inhibition of monoclonal antibodies. The limited number of alleles present at each HLA locus which is characteristic of coastal Papua New Guinea was observed. Five HLA-DR alleles were detected, of which only three (HLA-DR2, 4 and w5) were present at frequencies over 0.12. All individuals possessed at least one DR2,4 or w5 allele, and 96% of individuals possessed DR2, or 4 or both. There was no evidence for association between HLA type and antibody response to circumsporozoite repeat regions or the gametocyte epitopes. Homozygotes for DR2 and 4 were able to respond to each antigen. These results imply that either there is no HLA restriction of the response to these antigens or that each DR type is responding to a different variant of the T-epitope. Even in the latter case the results are encouraging for the prospects of inclusion of an HLA-restricted T-epitope in a malaria vaccine for Papua New Guinea since a limited number of versions would be required to cover a population with an HLA profile similar to that in Madang.

Malaria in adult outpatients at Goroka Hospital during 1986.

Of 206 adult outpatients attending Goroka Hospital with suspected malaria during 1986, 40.3% had blood slides positive for malaria (28.2% Plasmodium falciparum, 13.6% P. vivax and 1.9% P. malariae). Parasite densities and proportions of cases with gametocytes were higher than observed in endemic regions. Acquisition of infection during recent coastal travel was implicated in the majority of cases (86%). 6 out of 13 gametocyte carriers tested were infectious to Anopheles farauti mosquitos. Anti-malaria ELISA values in sera were elevated above non-immune values in over 75% of infections, although ELISA values were low compared to those in sera from residents of coastal areas, indicating the low level of previous exposure to malaria.