Edwin Afari

Species composition and inversion polymorphism of the anopheles gambiae complex in some sites of Ghana, West Africa.

Samples of Anopheles gambiae s.1. were collected from eight localities belonging to four of the five main ecological strata of Ghana. Analysis of ovarian polytene chromosomes revealed the presence of A. gambiae s.s. in all the sites studied, while A. arabiensis was detected only in the extreme northern locality of Navrongo and A. melas in some southern sites. Anopheles arabiensis showed a degree of inversion polymorphism comparable to the one observed in other West African countries. The analysis of the chromosomal polymorphism of A. gambiae s.s. showed the presence of the FOREST form in the rain forest localities and the SAVANNA form in the coastal savanna sites. The MOPTI form occurred sympatrically with the SAVANNA form in the northernmost locality. The possible influence of the presence of various taxa of the A. gambiae complex and of their intra-specific variants on malaria vectorial system is discussed.

Health centre versus home presumptive diagnosis of malaria in southern Ghana: implications for home-based care policy.

A study was conducted in 1997 to compare the accuracy of presumptive diagnosis of malaria in children aged 1-9 years performed by caretakers of the children to that of health centre staff in 2 ecological zones in southern Ghana. Similar symptoms were reported in the children at home and at the health centre. In the home setting, symptoms were reported the same day that they occurred, 77.6% of the children with a report of fever were febrile (axillary temperature > or = 37.5 degrees C) and 64.7% of the reports of malaria were parasitologically confirmed. In the health centre, the median duration of symptoms before a child was seen was 3 days (range 1-14 days), 58.5% of the children with a report of fever were febrile and 62.6% of the clinically diagnosed cases were parasitologically confirmed. In the 2 settings almost all the infections were due to Plasmodium falciparum. Parasite density was 3 times higher in the health centre cases compared to the home-diagnosed cases. Early and appropriate treatment of malaria detected in children by caretakers may prevent complications that arise as a result of persistence of symptoms and attainment of high parasitaemic levels.

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.

Risk factors for buruli ulcer in ghana-a case control study in the suhum-kraboa-coaltar and akuapem South districts of the eastern region

Background Buruli ulcer (BU) is a skin disease caused by Mycobacterium ulcerans. Its exact mode of transmission is not known. Previous studies have identified demographic, socio-economic, health and hygiene as well as environment related risk factors. We investigated whether the same factors pertain in Suhum-Kraboa-Coaltar (SKC) and Akuapem South (AS) Districts in Ghana which previously were not endemic for BU. Methods We conducted a case control study. A case of BU was defined as any person aged 2 years or more who resided in study area (SKC or AS District) diagnosed according to the WHO clinical case definition for BU and matched with age- (+/−5 years), gender-, and community controls. A structured questionnaire on host, demographic, environmental, and behavioural factors was administered to participants. Results A total of 113 cases and 113 community controls were interviewed. Multivariate conditional logistic regression analysis identified presence of wetland in the neighborhood (OR = 3.9, 95% CI = 1.9–8.2), insect bites in water/mud (OR = 5.7, 95% CI = 2.5–13.1), use of adhesive when injured (OR = 2.7, 95% CI = 1.1–6.8), and washing in the Densu river (OR = 2.3, 95% CI = 1.1–4.96) as risk factors associated with BU. Rubbing an injured area with alcohol (OR = 0.21, 95% CI = 0.008–0.57) and wearing long sleeves for farming (OR = 0.29, 95% CI = 0.14–0.62) showed protection against BU. Conclusion This study identified the presence of wetland, insect bites in water, use of adhesive when injured, and washing in the river as risk factors for BU; and covering limbs during farming as well as use of alcohol after insect bites as protective factors against BU in Ghana. Until paths of transmission are unraveled, control strategies in BU endemic areas should focus on these known risk factors.

Prevalence and Antibiogram of Campylobacter jejuni in Domestic Animals in Rural Ghana

A total of 134 samples of rectal and cloacal swabs taken from apparently healthy domestic animals that were in 43 of 76 homes located in rural Ghana were examined for Campylobacter jejuni. C. jejuni was isolated from 32.8% (44/134) of the animals. The highest isolation rate of 43.6% was from local domestic fowls, followed by goats (33.3%) and sheep (23%). This organism was not detected in the pigs, cats, and ducks. All 44 strains of this bacterium produced hydrogen sulphide and hydrolyzed hippurate; antibiogram on 24 strains showed resistance to cephalothin, cephalexin, and sulfamethoxazole/trimethoprim. C. jejuni biotype 2 is the prevailing strain in animals in the area studied.

Human T-cell recognition of synthetic peptides representing conserved and variant sequences from the merozoite surface protein 2 of Plasmodium falciparum

Merozoite surface protein 2 (MSP2) is a malaria vaccine candidate currently undergoing clinical trials. We analyzed the peripheral blood mononuclear cell (PBMC) response to synthetic peptides corresponding to conserved and variant regions of the FCQ-27 allelic form of MSP2 in Ghanaian individuals from an area of hyperendemic malaria transmission and in Danes without exposure to malaria. PBMC from 20-39% of Ghanaians responded to each of the peptides by proliferation and 29-36% had PBMC which produced interferon-gamma (IFN-gamma) in response to peptide stimulation. In Danes, there was no proliferation to two of the peptides and only PBMC from 5% of the individuals proliferated to the other three peptides. IFN-gamma production was not detected to any peptide. In both Danes and Ghanaians in only a few instances was IL-4 detected in the PBMC cultures. Overall PBMC from 79% of the Ghanaians responded by proliferation and/or cytokine secretion to at least one of three peptides tested, whereas responses were only observed in 14% of Danes (P = 0.002). These data suggest that the Ghanaians had expanded peripheral blood T-cell populations recognizing the peptides as a result of natural infection. The findings are encouraging for the development of a vaccine based on these T-epitope containing regions of MSP2, as the peptides were broadly recognized suggesting that they can bind to diverse HLA alleles and also because they include conserved MSP2 sequences. Immunisation with a vaccine construct incorporating the sequences present in these peptides could thus be expected to be immunogenic in a high percentage of individuals and lead to the establishment of memory T-cells, which can be boosted through natural infection.

Antibody response to 17D yellow fever vaccine in Ghanaian infants

OBJECTIVES To assess the seroresponses to yellow fever vaccination at 6 and 9 months of age; assess any possible adverse effects of immunization with the 17D yellow fever vaccine in infants, particularly at 6 months of age. METHODS Four hundred and twenty infants who had completed BCG, OPV and DPT immunizations were randomized to receive yellow fever immunization at either 6 or 9 months. A single dose of 0.5 ml of the reconstituted vaccine was administered to each infant by subcutaneous injection. To determine the yellow fever antibody levels of the infants, each donated 1 ml whole blood prior to immunization and 3 months post-immunization. Each serum sample was titred on Vero cells against the vaccine virus. FINDINGS The most common adverse reactions reported were fever, cough, diarrhoea and mild reactions at the inoculation site. The incidences of adverse reactions were not statistically different in both groups. None of the pre-immunization sera in both age groups had detectable yellow fever antibodies. Infants immunized at 6 months recorded seroconversion of 98.6% and those immunized at 9 months recorded 98% seroconversion. The GMT of their antibodies were 158.5 and 129.8, respectively. CONCLUSIONS The results indicate that seroresponses to yellow fever immunization at 6 and 9 months as determined by seroconversion and GMTs of antibodies are similar. The findings of good seroresponses at 6 months without significant adverse effects would suggest that the 17D yellow fever vaccine could be recommended for use in children at 6 months in outbreak situations or in high risk endemic areas.

Randomized controlled trial of acellular diphtheria, pertussis and tetanus vaccines in southern Ghana.

A randomized controlled trial of acellular diphtheria/pertussis/tetanus (ADPT) freeze-dried and liquid vaccines in infants was conducted in a peri-urban community (Ashaiman) in southern Ghana. Immunogenicity of the acellular vaccines, persistence of antibodies and adverse reactions were compared with those achieved with a whole-cell diphtheria-pertussis-tetanus (DPT) vaccine. The incidence of pertussis in the vaccine groups and prevalence of pertussis in children under 5 years of age in the study area were also determined. The acellular vaccines produced significantly fewer local and systemic reactions. Local reactions such as swelling and redness were observed in 2% (8/399) to 2.3% (9/385) of the acellular vaccine recipients as against 31% (122/394) in the whole-cell vaccine group. Fever ( > or = 37.5 degrees C) occurred in 7.27% (29/399) to 9.8% (38/385) in the acellular vaccine groups compared with 36.6% (145/394) in the whole-cell vaccine group. Geometric mean titres (GMTs), measured by ELISA, to pertussis toxin (PT) and filamentous haemagglutinin (FHA) were significantly higher in the acellular vaccine groups than in the whole-cell DPT (WCDPT) group. There were no significant differences in the GMTs of tetanus and diphtheria antitoxins between the two groups after each vaccination. Twelve months after primary vaccination, GMTs to PT in the freeze-dried, liquid ADPT groups and the WCDPT group have fallen from 56.23, 62.63 and 44.97 ELISA U/ml to 6.08, 6.18 and 11.30 ELISA U/ml, respectively. GMTs to FHA in all the vaccine groups also dropped during the same period from 49.94, 41.73 and 20.74 ELISA U/ml to 7.26, 7.72 and 5.91 ELISA U/ml, respectively. In this comparative controlled trial, the ADPT vaccines were more immunogenic, with less local and systemic reactions, than the WCDPT vaccine but there was a considerable drop in antibody titres in all the vaccine groups 12 months after primary vaccination. However, the levels of titres of anti-PT and anti-FHA antibodies in all the three vaccines that confer protection are not known. Further studies are necessary to provide this information in order to assess the need for subsequent booster doses after primary immunization with both ADPT and WCDPT vaccines.

A randomized controlled trial of two acellular pertussis-diphtheria-tetanus vaccines in primary immunization in Ghana: antibody responses and adverse reactions.

Two acellular pertussis vaccines combined with diphtheria and tetanus toxoids (APDT vaccines) were compared with a whole cell PDT (WCPDT) vaccine in primary immunization in Ghana. One is a liquid vaccine which is used for general immunization in Japan and the other is a freeze-dried vaccine newly developed as a heat-stable vaccine. Eighty-nine infants were recruited in the study. Sixty-eight who completed three doses of the immunization were assessed for immunological responses. Twenty-one dropped out because of sickness or moving from the study area. A total of 242 vaccinations in 89 infants were followed up for adverse reactions. Geometric mean titres (GMTs) to filamentous haemagglutinin in the two APDT vaccinees were significantly higher than in the WCPDT recipients. GMTs to pertussis toxin, diphtheria and tetanus toxoids were not significantly different among the three groups. Seropositive rates to pertussis antigens, tetanus and diphtheria toxoids were 94.4 to 100% in the two APDT vaccines. Systemic reactions within 7 days of inoculation were similarly low in the three groups, but significantly fewer infants had local reactions after either of the two APDT vaccines than after the WCPDT vaccine.

Pertussis immunization with acellular vaccines in Ghanaian children

In the present study, the persistence of antibodies to pertussis antigens was assessed in 51 Ghanaian children immunized with one of two acellular vaccines and one whole cell vaccine in early infancy. The effect of a booster dose 1 year after primary immunization was also examined. Antibody titres to pertussis toxin (PT) and filamentous haemagglutinin (FHA) were measured 1 month and 1 year after primary immunization and 1 month after the booster dose. Although geometric titres (GMTs) to FHA were significantly higher in the two types of acellular vaccinees in the whole cell vaccinees 1 month after primary immunization, GMTs to FHA and PT after 1 year were not significantly different in the three groups. Geometric mean titres to PT and FHA following the booster dose were significantly higher in the acellular vaccinees than in the whole cell vaccinees. Seropositivity rates to PT and FHA in the acellular vaccinees, which were more than 93.3% 1 month after primary immunization, ranged from 50.0 to 77.8% after 1 year. In conclusion, the acellular vaccines did not produce higher antibody levels than the whole cell vaccine 1 year after primary immunization. The booster dose was essential to maintaining sufficient seropositivity to pertussis antigens.