Avidity of IgG antibodies against meningococcal serogroup a polysaccharide and correlations with bactericidal activity in sera from meningitis patients and controls from Ethiopia.

Meningococcal meningitis is a significant global health challenge, especially for sub-Saharan area: the African meningitis belt. Neisseria meningitidis of serogroup A (MenA) is responsible for the large number of epidemics that have been recorded in these countries. To determine the level of antibodies against meningococcal A polysaccharide (APS) that correlates with protection against MenA disease in the African meningitis belt, it may be important to consider antibody avidity along with quantity. In this study, two ELISA methods using the chaotropic agent ammonium thiocyanate were compared and employed to measure avidity indexes (AI) of IgG antibodies against APS in controls and in acute and convalescent sera from Ethiopian meningococcal patients. High statistical correlations between the AIs determined by the two methods were observed. The geometric mean AI (GMAI) increased with time from acute to convalescent sera indicating affinity maturation. GMAI was significantly higher in convalescent sera from the MenA patients and in sera from the controls than in acute sera from patients with meningococcal disease. A significant correlation between serum bactericidal activity titres (SBA) and concentration of IgG antibodies against APS was observed; however, our results did not indicate that determination of antibody avidities by the thiocyanate elution method gave a better correlation with SBA than anti-APS IgG concentrations determined by the standard ELISA method.

Cryptosporidium and Giardia infection and drinking water sources among children in Lege Dini, Ethiopia.

We assessed the prevalence of Cryptosporidium and Giardia infections among children using protected and unprotected water sources in the Lege Dini watershed, Eastern Ethiopia, in November 2005 and May 2006. Of 655 children examined, 80 (12.2%) were infected with Cryptosporidium and 231 (35.3%) with Giardia. No difference was observed in the prevalence of cryptosporidiosis and giardiasis (P > 0.05) between children drinking water from protected and unprotected sources.

Prevalence of pulmonary tuberculosis among students in three eastern Ethiopian universities.

SETTINGS: Three universities located in eastern Ethiopia: Haramaya University, Haramaya; Dire-Dawa University, Dire-Dawa; and Jigjiga University, Jigjiga. OBJECTIVE: To determine the burden of pulmonary tuberculosis (PTB) among university students and to identify risk factors for the development of TB disease. DESIGN: All full-time university students were screened for symptoms of PTB and sputum was collected for acid-fast bacilli (AFB) examination and culture for Mycobacterium tuberculosis. RESULTS: Of 35 344 students screened, we identified 153 PTB cases that occurred over the 1-year study period, or 433/100 000 students. Of these, 117 (76%) PTB cases were found through passive case finding at student health centres, while 36 (24%) previously undiagnosed patients were identified through active case finding. Sixteen cases detected using active case finding (44%) were smear-positive. Living in a dormitory with 5 students and attending university for 2 years were both significantly associated with PTB (adjusted OR 2.49 and 3.79, respectively, P < 0.001). In persons who underwent drug susceptibility testing, 11 (30.5%) had resistance to at least one first-line anti-tuberculosis drug. CONCLUSION: We found a high burden of TB among university students in eastern Ethiopia. Screening for PTB upon university admission and at regular intervals should be considered to minimise TB transmission on university campuses.

Ethical review of health-related biotechnology research in Africa: a role for the Pan African Bioethics Initiative (PABIN).

The paper reviews the status of nature and functions of the Pan African Bioethics Initiative (PABIN) a voluntary organization, founded in 2001 by leading members of the African health research and bioethics communities, with the aim of enhancing ethical awareness in Africa, in general, and building ethical clearance capacity in all African countries in particular. PABIN, with a membership drawn from more than 20 African countries is a member of the forum of the WHO/TDR Strategic Initiative for Developing Capacity in Ethical Review (SIDCER). PABIN works closely with its sister forums in Asia, Latin America, Eastern Europe, and North America as well as other continental and international organizations that promote bioethics in health research. PABIN has conducted three conferences and several seminars in collaboration with continental and international partners on subjects of ethical concerns in Africa. Strategically, PABIN aims at assisting in the development of competent in-country bioethics review systems in all African countries. Notable among the contemporary issues that is on the PABIN agenda is addressing the repercussions of the active pursuit by pharmaceutical and other commercial interests from the Western developed countries to conduct all sorts of clinical biomedical trials on African populations before marketing such biotechnological products and services. This drive has brought with it highly controversial ethical issues at a time when both technical and organizational capacity are lacking in much of Africa to address the ethical concerns that are arising from some health-related researches. PABIN seeks to assure that the expected health and social benefits derivable from biotechnology are reaped in accordance with internationally accepted norms.

Differences in PCR reactivity between HIV proviruses from individuals in Ethiopia and Sweden.

The polymerase chain reaction (PCR), using primer pairs in the gag, pol, and env regions, was used in a comparative study of HIV-1 DNA in peripheral mononuclear blood cells from HIV-1-seropositive individuals in Ethiopia and Sweden. Although all Swedish samples were positive by PCR, the reactivity was more pronounced in samples from late stages than in those from early stages of infection. Six of nine Ethiopian samples from HIV-1-seropositive patients were positive by PCR, but the reactions were much weaker than those observed for Swedish samples, and in most cases seen with one primer pair only. These results suggest that the burden of HIV-1 DNA in peripheral mononuclear blood cells increases with advancing disease. PCR using primer pairs designed to detect HIV-1 infection in Europe and North America is not always suitable for the detection of HIV-1 infection in Ethiopia. The differences in PCR reactivity could possibly be a consequence of differences regarding host responses to the virus in the two countries, but more likely due to genomic differences between HIV-1 strains prevalent in Ethiopia and Sweden.

Differences in prevalence, intensity of infection and parasite-specific antibody levels do not predict different age-infection profiles.

Acquired immunity is believed to influence the age-infection profile of Schistosoma infections. We compared antibody responses against Schistosoma mansoni adult worm antigen (AWA) and soluble egg antigen (SEA) in 164 residents of two communities with different levels of infection. IgG, IgA, IgM, IgE, and IgG subclass 1 to 4 antibodies were determined by ELISA. Seventy-five of the subjects were from Harbu, an area with a prevalence of 39% and an intensity of infection of 116 eggs per gram of stool (EPG), whereas 89 subjects were from Bati, with a prevalence of 66% and intensity of infection of 256 EPG. In both communities the prevalence and the intensity of infection were highest in the age group 10-14 years, although both were significantly higher in Bati than in Harbu. Mean levels of AWA-specific IgA, IgM, IgG, IgG1 and IgG2, and of SEA-specific IgG, IgM, IgG2 and IgG3 were significantly higher in Bati than in Harbu. However, mean levels of IgE against worm and egg antigens were significantly higher in Harbu than in Bati. Significant differences were detected in the levels of IgA, IgE, IgG, IgM, IgG1 and IgG2 against AWA, and in IgE, IgM, IgG2 and IgG3 against SEA according to the place of residence. The levels of anti-AWA IgG, IgG1 and IgG2 and anti-SEA IgG, IgG1 and IgG4 were significantly associated with the intensity of infection. Anti-AWA IgM levels were associated with age, whereas sex and age had interacting effects on the levels of AWA-specific IgG1 and SEA-specific IgG and IgM. Antibody responses exhibited different age-related patterns in the two communities. This may indicate that differences in history of exposure influence the evolution of immune responses. However, the study did not support the view that differences in antibody levels between communities subject to different levels of infection result in a systematic deviation in age-infection profile (the "peak shift").

Age- and sex-related differences in antibody responses against Schistosoma mansoni soluble egg antigen in a cohort of school children in Ethiopia.

Acquired immunity is believed to be the main factor in the age-related differences in prevalence and intensity of Schistosoma infections. We studied antibody responses against S. mansoni soluble egg antigen (SEA) by ELISA in children before treatment, 5 weeks and one year after treatment. After screening for S. mansoni infection, positive children were treated with praziquantel (40 mg per kg body weight). Infection rate was significantly higher in boys younger than 12 years than in girls in the same age group. Levels of all antibody isotypes, except IgG1 (before treatment) or IgA (one year after treatment), were higher in children older or equal to 12 years than in those younger. The difference between age groups was significant for IgE, IgM, IgG3 and IgG4 (before treatment) and IgE (one year after treatment). Similarly, all antibody isotypes, except IgE, before treatment were higher in boys than in girls. At 5 weeks after treatment, IgG, IgE and IgG1 showed an increasing tendency, whereas IgM and IgG3 tended to decrease. One year after treatment, significant decreases were observed in IgG, IgG1 and IgG4 and a significant increase in IgG2 levels. The study presents further evidence for the difference in acquired immunity between younger and older children, and between boys and girls. The study also suggests that praziquantel differentially affects antibody responses against S. mansoni SEA.

The relationships between dehydroepiandrosterone sulphate (DHEAS), the intensity of Schistosoma mansoni infection and parasite-specific antibody responses. A cross-sectional study in residents of endemic communities in north-east Ethiopia.

There are speculations that the puberty-related hormone dehydroepiandrosterone sulphate (DHEAS) might influence the intensity of infection and immune responses during Schistosoma infections. We studied the relationships between DHEAS, intensity of Schistosoma mansoni infection and humoral immune responses in 135 residents of Ethiopia. Serum levels of eight antibody isotypes against worm and egg antigens were determined by ELISA. DHEAS was measured with an immunoluminometric assay. There was a significant negative correlation between serum levels of DHEAS and intensity of S. mansoni infection. A significant increase in serum levels of DHEAS in the age group 15-19 years was accompanied by a progressive decline in the intensity of infection. Peak level of DHEAS coincided with the lowest intensity of infection in the age group 20-29 years. Multiple regression analysis showed that DHEAS alone had a significant (p<0.0001) negative effect when the effect of age was removed. Age also had a significant (p<0.0001) negative effect on the intensity of infection, after removing the effect of DHEAS. The two predictive variables accounted for 34.4% of the decline in the intensity of infection. Age accounted for 24.9%, whereas DHEAS accounted for 15.2% when the effect of each of the variables was removed. DHEAS had significant negative effects on AWA-specific IgG (p=0.02) and IgG1 (p=0.018) and SEA-specific IgG1 (p=0.009), after adjusting for the effect of age.

Detection of Plasmodium falciparum sporozoites in naturally infected anopheline species using a fluorescein-labelled DNA probe.

A dot blot hybridization method was developed to detect Plasmodium falciparum sporozoites in naturally infected mosquitoes. A fluorescein-labelled oligomer was used as a probe. Initial non-specific hybridization was found to correlate with the presence of blood in the mosquitoes. This was eliminated by allowing digestion of the engorged blood by keeping the mosquitoes in cages for 48 h before processing. The limit of detection of the hybridization assay was estimated to be about 500 sporozoites. The assay was evaluated on 198 indoor resting blood fed female Anopheles gambiae s.l mosquitoes collected from three malaria hypo- and meso-endemic areas in Ethiopia. An application of the polymerase chain reaction (PCR) amplifying a fragment of the K1-14 gene of P. falciparum was used as a reference method. P. falciparum sporozoites were detected in four specimens (2%) by hybridization assay and by PCR alike. The results of this study indicate that the hybridization method can be potentially valuable in large scale epidemiological studies for detection of P. falciparum sporozoites in naturally infected anopheline species.

Cryptosporidium and other parasites in Ethiopian AIDS patients with chronic diarrhoea.

Previous studies in other African countries have shown high prevalences of Isospora belli and Cryptosporidium parvum infections in acquired immunodeficiency syndrome (AIDS) patients with chronic diarrhoea. However, there is lack of information regarding these infectious agents in Ethiopian AIDS patients. Thus, this investigation has been aimed at determining the prevalence of Cryptosporidium and other related gastrointestinal parasites in AIDS patients with diarrhoea in seven Addis Ababa hospitals. Stool specimens from 246 clinically diagnosed AIDS patients were parasitologically screened for parasitic infections constituting HIV-negative with diarrhoea and HIV-positive without diarrhoea control groups. A variety of intestinal protozoa and helminths were found in 50% of AIDS patients and 42% of the controls. Cryptosporidiosis was detected in 38(25.9%), Isosporiasis in two (1.4%), and Blastocystosis in one (0.7%) of the AIDS patients with diarrhoea. The occurrence of cryptosporidiosis among the AIDS patients and possible explanation of the increasingly high study subjects with diarrhoea but without identifiable parasites is discussed.

Determination of the human blood index of some anopheline mosquitos by using ELISA.

To determine the human blood index, 1253 anopheline mosquitos collected from Arbaminch, Awassa, Metahara and Ziway were tested by the blood meal ELISA, based on anti-human IgG. Higher positivity for human blood were observed in anopheline mosquitos collected from mixed dwellings (range, 26-92%) while those from animal shelters had the lowest positivity (range, 9-48%). The human blood index for A. arabiensis, a principal malaria vector in most parts of the country, from mixed dwelling collections was 88% while it was 43% for those collected from animal shelters. For A. pharoensis, it was 84% and 9%, and for A. coustani, it was 26% and 15% for the respective sites of collection. The human blood index of A. marshalli was 40%; for A. demeilloni, it was 36%; and for A. christyi, 91% for collections from mixed dwellings, while 35% for A. tenebrosus was determined for those collected from animal shelters. Out of the 15 A. funestus and the 11 A. longipalpis tested, 13 and 8 were positive for human blood, respectively. As the feeding and resting preference of the mosquitos varied, malaria control measures must be based on integrated measures in order to reduce man-mosquito contact.

Urban malaria in Nazareth, Ethiopia: parasitological studies.

Cross-sectional surveys for parasite infection, and factors that possibly influence human malaria transmission were carried out to characterize the epidemiology of urban malaria in Nazareth. Thick and thin blood films for parasite diagnosis were collected from individuals residing in 6 representative kebeles in the town. A questionnaire was used to obtain socioeconomic information. An overall parasite rate of 2.8%, P. falciparum (1.6%) and P. vivax (1.2%)- was observed among the 3890 individuals examined during the 4 surveys. Significant intra-urban differences (X2 = 27.31; P < 0.0001), in parasite rates, were observed with a much higher prevalence in the peripheral kebeles. A marked seasonal variation in parasite rates was evident during the sampling period and the peak occurred in Sept./Oct. There was no apparent decrease in parasite rate with increase in age, suggesting a delayed acquired immunity, typical of hypoendemic settings. The study has indicated that in Nazareth the prevalence of malaria is seasonally variable and relatively low, showing that it is unstable. Hence, if appropriate control measures are not instituted, malaria situation in -Nazareth is subject to epidemics.

Transmission of intestinal schistosomiasis in Bahir Dar, northwest Ethiopia.

Parasitological, malacological and transmission studies were made for a period of one year in the town of Bahir Dar, northwest Ethiopia. The overall prevalence of schistosomiasis mansoni in residents of Kebeles 8, 9 and 10 was 12%. The prevalence in Sertse Dengel school children was 45% and that in Dil Chibo school children was 32%. The peak prevalence in both sexes in school and non-school populations occurred in the age group 10-14 years. Intensity of infection showed a similar pattern of age variation as prevalence. Biomphalaria pfeifferi snail density peaked towards the end of the rainy season (September) in Lake Tana and around the middle of the dry season (January) on the shore of the River Abay. In September, infected snails were recovered from all collection sites. Of mice immersed in four water contact sites in September, schistosome infections developed in those immersed in three sites. Parasitological findings suggested that schistosomiasis infection rates depended on age and sex of individuals and geographical location of the place from the potentially infective water bodies. Snail population density and associated schistosomal infection in a human population depended on rainfall and associated ecological changes such as fluctuation in water level and vegetation density. As malacological findings and sentinel mouse immersion results indicated, it appeared that the main transmission season in Lake Tana region is towards the end of the rainy season although low level intermittent transmission may take place throughout the year.

A nitrocellulose membrane-based ELISA for the detection of Plasmodium infections in mosquitos.

A nitrocellulose (NC) membrane was evaluated as a solid-phase support for the detection of malaria-infected mosquitos using monoclonal antibodies (MAb) with a laboratory model based on Plasmodium inui and Anopheles dirus. MAbs produced against sporozoites of the N34 strain of P. inui, and selected by immunofluorescence assay and the circumsporozoite precipitin test, were used. A one-site indirect NC-ELISA that used unlabelled MAb and enzyme-labelled anti-mouse IgG was developed. Its sensitivity was about 200 sporozoites and it reliably detected one infected mosquito in a pool of 20. This indirect NC-ELISA has the advantage that it does not require direct conjugation of the MAb to an enzyme or biotin. In the direct one-site NC-ELISA, which is also reported, the relatively simple biotinylation procedure was an alternative to the enzyme- or radiolabelled MAbs. The NC-ELISAs were simple and rapid. Furthermore, the indirect NC-ELISA can be used to detect sporozoite antigen localized in various body sectors of mosquitos.

Control of human African trypanosomiasis: trap and odour preference of tsetse flies (Glossina morsitans submorsitans) in the upper Didessa river valley of Ethiopia.

Ethiopia is one of the endemic countries for Human African Trypanosomiasis (HAT) as over 100,000 people are at risk of having the disease. The control of HAT using odour preference of tsetse flies (Glossina morsitans submorsitans) was studied in upper Didessa river valley of Ethiopia. No information exists on the effectiveness of attractants for these species of tsetse flies in Ethiopia. Three attractants and their combinations namely: acetone, octenol, cow urine, acetone + octenol, acetone + octenol + cow urine, were evaluated using biconical and NGU traps for their efficacy as a first step in developing a sustainable community-based HAT control initiative. The biconical traps baited with acetone, octenol or cow urine, or when combined, were more effective in catching G. m. submorsitans than the NGU traps (P < 0.05). However, the NGU traps caught more female tsetse flies than the biconical traps (P < 0.05). The acetone, octenol and cow urine combination was the most effective in attracting tsetse flies in both the biconical and NGU traps. Acetone was the best attractant while octenol was the least effective. Cow urine showed great promise for possible use in community-based HAT control activities, especially urine that has been kept for several days. The use of cow urine in HAT control in Ethiopia is likely to succeed in the future because of its sustainability.

Effect of deworming on human T cell responses to mycobacterial antigens in helminth-exposed individuals before and after bacille Calmette-Guérin (BCG) vaccination.

The protective efficacy of BCG vaccination against pulmonary tuberculosis (TB) is highly variable in different populations. The reason remains to be elucidated. This study aims to investigate the possible effect of intestinal helminths on the immune response to PPD in naturally immunized or BCG-vaccinated humans. The study population was assessed for helminthic infection and those found to be positive were randomly assigned to either an albendazole treatment group or a control group who received a placebo. The immune response to PPD was compared between the two groups. In addition, subjects who were tuberculin skin test-negative in both groups were BCG vaccinated and later on tested for PPD-specific responses. Albendazole induced elimination/or reduction in intestinal worms resulting in a significant improvement in T cell proliferation and in interferon-gamma production by peripheral blood mononuclear cells (PBMC) stimulated with PPD. Moreover, BCG vaccination significantly improved PPD-specific immune responses in the treated group but not in the placebo group. The differences in the in vivo skin test responses were not significant. The data show that cellular immune responses to PPD are reduced in persons with concurrent helminthic infections, perhaps reflecting a lowered resistance to mycobacterial infections. This could explain, at least in part, the reduced efficacy of BCG against TB in helminth-endemic areas of the world.

The use of real-time PCR to identify Entamoeba histolytica and E. dispar infections in prisoners and primary-school children in Ethiopia.

In Ethiopia, it is generally unknown what proportion of the amoebic infections commonly found, by microscopy, in humans are caused by non-invasive Entamoeba dispar rather than the potentially invasive E. histolytica. Faecal samples were therefore collected from 363 primary-school students and 409 prisoners from various regions of Ethiopia. Each of these samples was checked for Entamoeba infection by the microscopical examination of formol-ether concentrates. DNA was then extracted from the 213 samples (27.6%) found Entamoeba-positive, and run in a real-time PCR with primers, based on the SSU-rRNA gene sequences of E. histolytica and E. dispar, that allow DNA from the two species to be distinguished. Although E. dispar DNA was identified in 195 (91.5%) of the 213 samples checked by PCR, no E. histolytica DNA was detected. This finding is consistent with the conclusion of a previous, smaller investigation: that many amoebic infections in Ethiopia are incorrectly attributed to E. histolytica and then treated, unnecessarily, with amoebicidal drugs.

HIV-1 subtype C in commerical sex workers in Addis Ababa, Ethiopia.

In this study, we have investigated the diversity of the current HIV-1 strains circulating in Addis Ababa, Ethiopia; in addition, we have evaluated the applicability of peptide enzyme-linked immunosorbent assay (ELISA) and heteroduplex mobility assay (HMA) for HIV-1 subtyping. Previous studies have indicated that HIV-1 subtype C is the major subtype present in HIV-positive samples collected from various risk groups between 1988 and 1995 in Addis Ababa. To assess the possible influx of new HIV-1 subtypes, 150 commercial sex workers (CSW) reporting in 1997 to two Health Centers in Addis Ababa were enrolled in an unlinked anonymous cross-sectional study. Subtyping was performed according to the World Health Organization algorithm of peptide ELISA, followed by HMA and DNA sequencing. As a result, the HIV-1 prevalence among these CSWs was found to be 45% (67 of 150). Of the 67 samples, 66 contained HIV-1 of subtype C and only one was of subtype D. This confirms the persistent overall presence of HIV-1 subtype C in Addis Ababa and a low influx of other subtypes into this location.

Sexual transmission of SIVagm in wild grivet monkeys.

This study reports the prevalence of simian immunodeficiency virus and the relationship of serostatus to age and sex among a wild population of Ethiopian grivet monkeys (Cercopithecus aethiops aethiops). Seropositivity paralleled patterns of sexual activity, being nearly universal in females of reproductive age, and absent in all males except those that were fully adult. One female seroconverted between two capture seasons at an age consistent with first breeding. Our findings support a predominantly sexual mode of transmission among SIVagm infected grivets.

Role of incidental and/or cured intestinal parasitic infections on profile of CD4+ and CD8+ T cell subsets and activation status in HIV-1 infected and uninfected adult Ethiopians.

Intestinal parasitic infections have been suggested to cause persistent immune activation leading to an unbalanced immune state. Such a state has been proposed to be a major factor in the pathogenesis of AIDS in an African context. The present study investigated the effect of incidental parasitic infection and treatment on the profile of T cell differentiation and activation markers on CD4+ and CD8+ T cells from HIV-1 infected and uninfected adult Ethiopians. Cryopreserved PBMCs from 64 subjects (41 HIV-negative and 23 HIV-positive) with follow-up visits at 6-monthly intervals were used to compare the effect of incidental intestinal parasites and their treatment upon T cell subset profiles and activation status. The samples were stained with antibodies to various T cell differentiation and activation markers allowing naive, memory, effector, memory/effector, activated and resting CD4+ and CD8+ T cell subsets to be quantified by triple-colour FACScan. Incidental intestinal parasitic infections resulted in a significant increase in memory CD4+ T cell numbers both in HIV-negative and HIV-positive subjects (P < 0.05). There was also a significant increase in the percentage of CD8+ HLA-DR+ T cells (P < 0.05) in HIV-positive subjects co-infected with parasites. In HIV-negative subjects, a significant decline in activated cells and a significant increase in resting CD8+ T cells (P < 0.05) was observed after treatment for parasites. These data suggest that intestinal parasitic infections could result in the alteration of T cell subset counts and also in the up-regulation of T cell activation markers in peripheral blood. Treatment of parasitic infections showed a tendency to reduce the activation suggesting that, together with other community based intervention strategies, such treatment could be used to down-regulate immune activation and hence protect the host from being easily attacked by HIV.