The rs150311303 polymorphism in FcγRIIa enhances IgG binding capacity.

Fc gamma receptor (FcγR) provides an important link between humoral and cellular immune responses. FcγRIIa-H131R polymorphism has been associated with differential binding to IgG subclasses and susceptibility to severe malaria phenotypes among different populations in the malaria endemic world. In this study, the effect of FCGR2A gene polymorphisms on susceptibility to symptomatic malaria among Ghanaian cohort children was investigated. Blood samples from four hundred and 29 (429) healthy Ghanaian children were genotyped for FCGR2A polymorphisms by direct DNA sequencing. Attributable and relative risks to symptomatic malaria were calculated for the polymorphic variants. Two major FCGR2A polymorphisms, rs1801274A/G (FcγRIIa-H131R) and rs150311303 (FcγRIIa-ins170L), were identified in the study population, and assessment of their risks did not show significant association with susceptibility to symptomatic malaria. The functional significance of these polymorphisms was also examined by evaluating their binding abilities to IgG subclasses using flow cytometric analysis of HEK cells transfected with the FcγRIIa haplotype variants. The binding assay revealed the rs150311303, which was observed only among carriers of the FcγRIIa-131RR genotype for the rs1801274 to consistently enhance binding capacities to all IgG subclasses. Thus, of the three FcγRIIa haplotype variants observed in this study population, the FcγRIIa(RL) haplotype variant was observed to have the highest binding ability to IgG1, IgG3 and IgG4.

Plasmodium falciparum: sensitivity to chloroquine in vivo in three ecological zones in Ghana.

4690 children aged 6-15 years in 5 urban and 4 rural communities in 3 ecological zones in Ghana were screened from June 1988 to December 1990 to provide suitable candidates for the World Health Organization standard in vivo test for susceptibility of Plasmodium falciparum to chloroquine. 1880 (40.1%) had parasitaemia, mostly (83.7-98.6%) due to P. falciparum infection. Of the 626 in vivo tests performed, 570 (91.1%) showed sensitivity to chloroquine and 56 (8.9%) responses were classified as resistant to chloroquine at RI (5.1%) and RII (3.8%). The resistance responses were commonest (17.1-22.7%) in the coastal zone, followed by the savanna zone (8.6-10.0%), and lowest in the forest zone (3.1-6.3%). The RII responses occurred mainly in communities in the coastal zone. There was no RIII resistance in any zone. The pattern of RI (early) and RII responses of P. falciparum to chloroquine in this study suggested an increase in sensitivity, or a reduction in resistance, of P. falciparum to chloroquine from the coast to the forest and northern savanna zones, and from the urban to the rural communities in each zone in Ghana.

Anaemia caused by asymptomatic Plasmodium falciparum infection in semi-immune African schoolchildren.

A cohort of 250 Ghanaian schoolchildren aged 5-15 years was followed clinically and parasitologically for 4 months in 1997/98 in order to study the effect of asymptomatic Plasmodium falciparum infections on haematological indices and bone-marrow responses. Of the 250 children 65 met the predefined study criteria. Thus, 14 children were parasite-free throughout (group 1), 44 had P. falciparum in all blood samples collected but no symptoms of malaria (group 2), and 7 had 1 malaria attack during the study period (group 3). At the end of the study the mean haemoglobin (Hb) level in group 1 was 123 g/L, significantly higher than the value of 114 g/L in groups 2 and 3 (P < 0.02, adjusted for age and splenomegaly). The low Hb in group 2 was associated with subnormal plasma iron. Low Hb was associated with elevated erythropoietin (EPO) levels, and there was a positive correlation between EPO and reticulocyte counts. However, the reticulocyte response to EPO was more pronounced in uninfected than in infected children, suggesting a partial interference with erythropoiesis in asymptomatic infections. Children with asymptomatic infections had significantly higher plasma levels of tumour necrosis factor than uninfected children (geometric means 50 ng/L and 27 ng/L, respectively, P < 0.001) and this cytokine may contribute to bone-marrow suppression and disturbed iron metabolism. We suggest that asymptomatic malaria leads to a homeostatic imbalance in which erythrocyte loss due to parasite replication is only partially compensated for by increased erythropoiesis. The consequences of the reduced Hb levels on the development and cognitive abilities of children with asymptomatic infections, and the risk of precipitation of iron deficiency, deserve further study and should be considered in malaria control programmes that aim at reducing morbidity rather than transmission.

Haptoglobin 1-1 is associated with susceptibility to severe Plasmodium falciparum malaria.

The haptoglobin (Hp) phenotypes were determined by polyacrylamide-gel electrophoresis in plasma samples obtained in 1997 from 113 Plasmodium falciparum malaria patients (aged 1-12 years) with strictly defined cerebral malaria, severe malarial anaemia, or uncomplicated malaria and 42 age-matched healthy controls from the same area (coastal Ghana). Hp1-1 was significantly more prevalent among the patients (43%) than among healthy controls (7.1%), whereas Hp2-1 and Hp2-2 were underrepresented among the patients (11% and 2%, respectively) compared to the control donors (33% and 14%, respectively). No significant difference in frequency of Hp0 was observed between patients and controls. Among the malaria patients, the Hp1-1 phenotype was significantly more prevalent among patients with the complications of cerebral malaria and severe anaemia compared to patients with uncomplicated disease, whereas the reverse was seen with respect to Hp2-1 and Hp2-2. Our data suggest that the Hp1-1 phenotype is associated with susceptibility to P. falciparum malaria in general, and to the development of severe disease in particular.

Complement binding to erythrocytes is associated with macrophage activation and reduced haemoglobin in Plasmodium falciparum malaria.

We have examined IgG and complement factor C3d deposition on erythrocytes by means of the direct Coombs' test (DAT) and looked for an association with the anaemia seen in falciparum malaria in children living in an area of hyperendemic malaria transmission (in Ghana). In one study (in 1997), 53 out of 199 patients had a positive DAT. Of these, 45 samples reacted with anti-C3d antibodies, 2 with anti-IgG and 6 with both reagents. There were significantly lower haemoglobin (Hb)-levels and higher prevalence of spleen enlargement in DAT-positive than in DAT-negative patients. Hb-levels were independently associated with DAT and age. This initial study was designed to investigate the role of intravascular haemolysis (IVH), but we found no association between IVH and either DAT result or anaemia. Because of the risk of selection bias we repeated the study using consecutive enrollment of malaria patients and were able to confirm the results in a total of 49 DAT-positive and 183 DAT-negative patients. This second study (in 1998) was designed to look at the importance of erythrophagocytosis through measurement of plasma neopterin levels and total nitrite and nitrate as markers of NO-release. Both parameters were significantly higher in DAT-positive than in DAT-negative patients (P < 0.001), indicating that complement binding to erythrocytes was associated with macrophage activation. Plasma levels of haptoglobin, interleukin-10 and tumour necrosis factor-alpha did not vary between the groups. The studies support the role of complement activation and erythrophagocytosis in the pathogenesis of anaemia in falciparum malaria in African children.

Prevalence of tuberculosis in cattle in the Dangme-West district of Ghana, public health implications.

Bovine tuberculosis due to Mycobacterium bovis is a major cause of human gastrointestinal tuberculosis in developing countries where bovine milk is often not pasteurised before use. Little information is available on the prevalence of the disease in African cattle and its zoonotic impact. The Ghanaian Government, through its peri-urban dairy cattle development project, is promoting the use of milk and dairy products from local cows in selected districts of the country, including the Dangme-West district of the Greater Accra region. A survey was, therefore, undertaken to determine the prevalence of tuberculosis infection in cattle in this district and to assess the level of awareness with regard to the risks through milk consumption. The standard single intradermal comparative tuberculin test (SCITT) using purified protein derivative (PPD) of M. bovis and M. avium was used to detect cattle infected with M. bovis. The study established the prevalence of a 13.8% infection in cattle in the district although the prevalence was as high as 50% in some kraals. Prevalence was highest in the Ningo sub-district (19.0%), followed by Dodowa, the district capital (14.0%), while the other two sub-districts, Prampram and Osudoku had lower rates of 11.3 and 10. 8%, respectively. Cattle of all ages and both sexes were affected, but the prevalence in cows was twice as high as that in heifers or bulls. The study also established that there is a considerable lack of knowledge about bovine tuberculosis among cattle owners and herdsmen in the community and that milk is often used untreated, thus increasing the risk of human infection.

Seroprevalence of brucellosis in cattle and humans in the Akwapim-South district of Ghana: public health implications.

A total of 183 cattle comprising 54 bulls, 53 milking cows, 76 heifers and 44 calves in the Akwapim-South district of Ghana were tested for antibodies against Brucella abortus using the Rose Bengal plate test. The results indicated that cattle in the Akwapim-South district were infected with Brucella with a mean seroprevalence of 6. 6%. There was no difference in the seroprevalence either between females 11/129 (8.5%) and males 1/54 (1.9%), or among the three different breeds of cattle (Sanga, West African short horn (WASH) and white Fulani) in the study area. However, there was a significant increase in seropositivity with respect to age. A significant association between antibodies against Brucella and a history of abortions and retained placenta in cows indicated that brucellosis might be responsible for significant economic losses to farmers in the area. However, no evidence of human brucellosis was detected by antibody screening in selected risk groups.

Detection and management of zoonotic diseases at the Kumasi slaughterhouse in Ghana.

Slaughterhouse surveys are important in the detection and management of zoonotic diseases. Routine reports from the Kumasi slaughterhouse, in the Ashanti region of Ghana, include cases of zoonotic diseases. Due to its location and size, Kumasi is the major cattle market and an important transit point for cattle trade from places within and outside Ghana. This present study was designed to examine slaughterhouse reports and to explore the nature of the knowledge, attitude and practices of butchers who operate at this slaughterhouse, in relation to zoonoses. The study was largely descriptive, employing qualitative methods and tools. Butchers were interviewed and their practices along the production line observed. The study indicates that zoonotic diseases are frequently detected at the Kumasi slaughterhouse. However the knowledge, attitudes, practices and beliefs of the butchers are largely inadequate for their profession in view of the important public health role that butchers play. The butchers have never received any form of training. It is recommended that the butchers receive training on a regular basis and that laws be formulated and implemented to protect the health of the butchers and the general public.

Human behavioural factors implicated in outbreaks of human anthrax in the Tamale municipality of northern Ghana.

The knowledge, attitude, beliefs and practices of cattle owners, herdsmen, butchers and meat consumers about anthrax were used to provide a better understanding of the major factors responsible for the frequent outbreaks of human anthrax in the Tamale municipality of northern Ghana. A total of 96% of the respondents, made up of 50 cattle owners, 50 herdsmen, 25 butchers and 125 consumers, knew of anthrax and the clinical signs indicative of anthrax in cattle. However, very few knew the causative agent and many attributed the disease to the supernatural. Eight percent of the respondents believed that herbal preparations could protect against human anthrax, while 9% indicated that they would seek help from traditional practitioners or herbalists, if they suspected anthrax. A significant proportion of respondents were of the view that animals, which had died of unknown causes could be eaten because they served as a source of inexpensive meat for the community, especially if the meat was cooked with herbs which was commonly thought to prevent anthrax. These attitudes, taken together with the low income of the population studied, made the consumption of meat from animals, which had died of unknown causes, an attractive option. This increased the vulnerability to human anthrax in an area with frequent anthrax outbreaks in livestock. The results of this study suggest that a public education campaign involving both veterinary and local health personnel on the actual cause and prevention of anthrax could reduce outbreaks of anthrax in people.

The seroprevalence of toxoplasmosis in pigs in Ghana.

A serological survey of toxoplasmosis in pigs in Ghana was carried out between October 1997 and April 1998 in the three ecological zones of Ghana: the Coastal Savannah, the Forest Belt and the Guinea Savannah. Antibody against Toxoplasma gondii was measured in pig serum using a microplate-ELISA which had a sensitivity and specificity of 90.2 and 92.3%, respectively when compared with IFAT. A national seroprevalence of 39% was obtained in pigs, with the ecological distribution being 43.9, 30.5 and 42.5% for the Coastal Savannah, the Forest Belt and the Guinea Savannah, respectively. The age of the animal, the breed, the environmental conditions and the management practices appeared to be the major determinants of prevalence of antibodies against T. gondii. The prevalence of anti-T. gondii antibodies was found to increase with age (P<0.05). Pigs from the two Savannah zones had a significantly higher (P<0.05) antibody prevalence than those sampled from the Forest belt. Antibody prevalence (46.8%) in crossbreed pigs was significantly higher (P<0.05) than that of the exotic Large White breed (38.8%).

The prevalence of anti-Toxoplasma gondii antibodies in Ghanaian sheep and goats.

The enzyme-linked immunosorbent assay (ELISA) was used to detect anti-Toxoplasma gondii antibodies in 1258 small ruminants (732 sheep and 526 goats) sampled from 28 different locations in the three ecological zones of Ghana. The animals sampled had an overall seroprevalence of 30.5% (384 of the total). Sheep had a higher overall prevalence (33.2%) compared to the goats (26.8%). Animals sampled from the Coastal Savannah and the Forest zones had prevalences of 39.4% and 39.1%, respectively, which were significantly higher (P<0.01) than the prevalence recorded for the drier Guinea Savannah zone (20%). Prevalence of antibodies in female animals (35.8%) was significantly higher (P<0.01) than that for males (21.1%). Significant differences were also observed between breeds and age groups. The ELISA was found to be both highly sensitive (92%) and specific (91%) when compared to the IFAT, which was used as a reference test.

Distinct patterns of cytokine regulation in discrete clinical forms of Plasmodium falciparum malaria.

The pathogenesis of two of the most severe complications of Plasmodium falciparum malaria, cerebral malaria (CM) and severe malarial anaemia (SA) both appear to involve dysregulation of the immune system. We have measured plasma levels of TNF and its two receptors in Ghanaian children with strictly defined cerebral malaria (CM), severe malarial anaemia (SA), or uncomplicated malaria (UM) in two independent studies in an area of seasonal, hyperendemic transmission of P. falciparum. Levels of TNF, soluble TNF receptor 1 (sTNF-R1) and 2 (sTNF-R2) were found to be significantly higher in CM than in the other clinical categories of P. falciparum malaria patients. Levels of both receptors depended on clinical category, whereas only sTNF-R1 levels were significantly dependent on parasitemia. Detailed analysis of the interrelationship between these variables resolved this pattern further, and identified marked differences between the patient categories. While levels of TNF, sTNF-R1 and sTNF-R2 correlated with parasitemia in UM, this was not the case in CM and SA. Rather, there was a tendency towards high levels of TNF and its receptors in CM and low levels in SA without significant correlation to parasitemia in either category. This, and the fact that malaria-induced increases in plasma levels of IL-10 are much lower in SA compared to CM, suggest that distinct forms of dysregulation of the immune response to infection contribute to the pathogenesis of CM and SA.

Serum immunoglobin and complement levels in Ghanaian sickle cell patients in the steady asymptomatic state.

Serum IgM levels in sickle cell patients in the steady asymptomatic state were determined using radial immunodiffusion and found to be significantly higher than in health controls. Other immunoglobulins (IgA and IgG) were not significantly different from those of the controls. However concentrations of both C3 and C4 components of complements were significantly lower in sickle cell disease. This explains the low opsonization and chemotactic functions observed in these patients and further confirms the transient activation of the alternate pathway of complement. Abnormal complement C3 metabolism may explain the high susceptibility of patients to infections which contributes to the crisis in sickle cell disease.

In vitro responses of P. falciparum parasites to chloroquine, amodiaquine and quinine in two ecological zones in Ghana.

Blood specimens were taken from 318 school children with at least 1,000 and not more than 80,000 P. falciparum asexual parasites per microliter of blood for a 30 hour in vitro microtest of P. falciparum asexual parasites responses to chloroquine, amodiaquine and quinine. The study was conducted in primary schools in four urban and three rural communities in the costal and forest zones in Ghana between June 1988 and December 1990. Chloroquine resistance was present in 58.7 pc (54/92) and 3.9 pc (4/103) of the successful in vitro tests in the coastal and forest zones respectively. Resistance to amodiaquine was recorded in 28.6 pc (12/42) of the successful tests in coastal zone. There was no resistance to quinine in any of the ecological zones. Concentrations of the three drugs in pmol required for 90 pc inhibition of schizont maturation were generally higher in communities in the coastal zone than those in the forest zone. The results suggest an increase in sensitivity or a reduction in resistance of P. falciparum to the drugs from the coast to the forest zone.

Enhancing access to immunization services and exploiting the benefits of recent innovations in the African region.

The African Regional Office of the World Health Organization (WHO AFRO) organized the annual regional conference on immunization (ARCI) from 10 to 12 December 2012 in Dar es Salaam, Tanzania, under the theme, "Innovations, access and the right of all to vaccines". The meeting reviewed the status of immunization in the region and identified all innovations, strategies and technologies available and how these could be fully utilized to enhance the access and the rights of all to vaccines. Over 50 oral presentations were made in plenary and parallel sessions of the conference which was attended by over 200 participants drawn from national immunization programs, academia, public health experts and immunization partners. In addition there were 40 poster presentations. This manuscript summarizes of the meeting, highlighting the innovations in immunization being piloted or scaled-up, their impact and suggesting ways to further improve immunization service delivery for the eradication, elimination and control of vaccine-preventable diseases in the region.

MALVAC 2009: progress and challenges in development of whole organism malaria vaccines for endemic countries, 3-4 June 2009, Dakar, Senegal.

Research and development into whole organism malaria vaccines is progressing rapidly thanks to the major investments over recent years from several funders, and the commitment and interest of many leading researchers. Progress includes the discovery of potential new candidate vaccines and the start of the first phase 1/2a clinical trial of the radiation attenuated sporozoite approach for Plasmodium falciparum, under US Food and Drug Administration regulatory oversight. A group of leading scientists, clinical trialists and stakeholders, together with representatives of regulatory authorities including some from African countries, met recently to document the issues that will require detailed consideration to assess this promising approach. Questions related to scale-up, quality, purity and consistency of a manufacturing process using mosquitoes to generate a commercial product, and demonstration of the stability of attenuated sporozoites will need further work. Should a high level of efficacy be demonstrated in clinical challenge studies, it will become a priority to agree in which populations and age groups questions about strain-transcendence and duration of efficacy should be answered, and how clinical development can progress with an approach based on cryopreservation in liquid nitrogen.

Circulating epstein-barr virus in children living in malaria-endemic areas.

Children living in malaria-endemic regions have high incidence of Burkitt's lymphoma (BL), the aetiology of which involves Plasmodium falciparum malaria and Epstein-Barr virus (EBV) infections. Acute malarial infection impairs the EBV-specific immune responses with the consequent increase in the number of EBV-carrying B cells in the circulation. To further understand the potential influence of malarial infection on the EBV persistence in children living in malaria-endemic areas, we studied the occurrence and quantified cell-free EBV-DNA in plasma from 73 Ghanaian children with and without acute malarial infection. Viral DNA was detected in 40% of the samples (47% in the malaria-infected and 34% in the nonmalaria group) but was absent in plasma from Ghanaian adults and healthy Italian children. These findings provide evidence that viral reactivation is common among children living in malaria-endemic areas, and may contribute to the increased risk for endemic BL. The data also suggest that the epidemiology of EBV infection and persistence varies in different areas of the world.