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The incidence of calicivirus infection in Ghana and many other African countries is not known. Thirteen (15.9%) of the 82 diarrhoeic stool samples tested for caliciviruses were positive for noroviruses (NoVs). NoVs were present in all age groups and were detected only during the diarrhoea peak that coincided with the peak rotavirus season. Ten (76.9%) of the NoV detected were genogroup II (GII) NoVs and the remaining three (23.1%) genogroup I (GI) NoVs. The predominant GII detected was GII-4 (60%, 6/10). Three of the GII NoVs were determined to be recombinants of GII-8/GII-14 as deduced from the sequencing of the region spanning the Orf1/2 junction. The GII genotypes formed four clusters with published GII sequences. The data shown enhances understanding of NoV diversity in Ghanaian children and demonstrate the global spread of distinct common genotypes to African countries.

The study examined the efficacy of chloroquine (CQ), amodiaquine (AQ) and sulphadoxine-pyrimethamine (SP) for the treatment of uncomplicated Plasmodium falciparum malaria in Ghana. A total of 351 children were randomized to receive either of the three study drugs. Patients were evaluated using the WHO 14-day in vivo antimalarial testing guidelines. The 14-day adequate clinical and parasitological response analysis revealed that CQ, 46.7% (95% CI 37.5, 56.0) has the least efficacy compared with AQ, 86.1% (95% CI 78.3, 91.8) and SP, 77.6% (95% CI 68.9, 84.8). Late parasite failures were also lower and similar in the AQ and SP (9.6% and 10.3%) than in the CQ (32.5%) group. However, CQ and AQ groups showed better fever clearance compared with SP throughout except for day 7 and after when possibly due to its significant late clinical failures, clearance by CQ was lower. Our findings suggest that CQ is no longer useful in Ghana and should be replaced as a first-line treatment of malaria. Replacement of CQ preferably with AQ combination treatment will be an effective and an affordable alternative for the treatment of uncomplicated malaria.

We studied the malaria transmission dynamics in Kassena Nankana district (KND), a site in northern Ghana proposed for testing malaria vaccines. Intensive mosquito sampling for 1 year using human landing catches in three micro-ecological sites (irrigated, lowland and rocky highland) yielded 18 228 mosquitoes. Anopheles gambiae s.l. and Anopheles funestus constituted 94.3% of the total collection with 76.8% captured from the irrigated communities. Other species collected but in relatively few numbers were Anopheles pharoensis (5.4%) and Anopheles rufipes (0.3%). Molecular analysis of 728 An. gambiae.s.l. identified Anopheles gambiae s.s. as the most dominant sibling species (97.7%) of the An. gambiae complex from the three ecological sites. Biting rates of the vectors (36.7 bites per man per night) were significantly higher (P<0.05) in the irrigated area than in the non-irrigated lowland (5.2) and rocky highlands (5.9). Plasmodium falciparum sporozoite rates of 7.2% (295/4075) and 7.1% (269/3773) were estimated for An. gambiae s.s. and An. funestus, respectively. Transmission was highly seasonal, and the heaviest transmission occurred from June to October. The intensity of transmission was higher for people in the irrigated communities than the non-irrigated ones. An overall annual entomological inoculation rate (EIR) of 418 infective bites was estimated in KND. There were micro-ecological variations in the EIRs, with values of 228 infective bites in the rocky highlands, 360 in the lowlands and 630 in the irrigated area. Approximately 60% of malaria transmission in KND occurred indoors during the second half of the night, peaking at daybreak between 04.00 and 06.00 hours. Vaccine trials could be conducted in this district, with timing dependent on the seasonal patterns and intensity of transmission taking into consideration the micro-geographical differences and vaccine trial objectives.

We conducted all-age point prevalence surveys to profile the severity and seasonality of malaria and anaemia in Kassena-Nankana District of northern Ghana. Random cross-sectional surveys were timed to coincide with the end of low (May 2001) and high (November 2001) malaria transmission seasons and to yield information as to the potential value of haemoglobin (Hb) levels and parasitaemia as markers of malaria morbidity and/or malaria vaccine effect. Parasitaemia was found in 22% (515 of 2286) screened in May (dry-low transmission), and in 61% of the general population (1026 of 1676) screened in November (wet-high transmission). Malaria prevalence in May ranged from 4% (infants <6 months and adults 50-60 years) to 54% (children 5-10 years). Age-specific malaria prevalence in November ranged from 38% (adults 50-60 years) to 82% (children 5-10 years). Differences between low- and high-transmission periods in the prevalence of severe anaemia (SA) among young children (6-24 months) were unexpectedly comparable (low, 3.9%vs. high, 5.4%; P = 0.52) and greatly reduced from levels measured in this same community and age group in November 2000 (12.5%) and November 1996 (22.0%). Despite the lower frequency of anaemia/SA in young children surveyed in 2001, it was still clear that this condition was strongly associated with parasitaemia and that children under 5 years of age experienced a significant drop in their mean Hb levels by the end of the high transmission season. Prevalence of parasitaemia was significantly lower (P < 0.01) among infants and young children (<2 years) whose parents reported the use of bednets. There was a significantly lower risk of parasitaemia among infants [odds ratio (OR) 6-8] and young children (OR 3-4) living in the central, more urbanized sector of the study area.

Genotyping of human rotaviruses was performed on 312 rotavirus-positive samples collected from 2,205 young children with diarrhea in the Upper East District of Ghana, a rural community. Of the 271 (86.9%) rotavirus strains that could be VP7 (G) or VP4 (P) characterized, 73 (26.9%) were of G9 specificity. The predominant G9 genotype was G9P[8], which constituted 79.5% of all G9 strains detected, followed by G9P[6] (12.3%), G9P[10] (2.7%), and G9P[4] (1.3%). G9 strains with mixed P types constituted 2.7% of all G9 strains found in the study. All the G9P[8] strains had a long RNA electrophoretic pattern with VP6 subgroup II specificity. Four G9 isolates, GH1319, GH1416, GH3550, and GH3574, which were selected based on the abundance of stool material and were representative of the three electropherotypes observed, were cloned and sequenced. The Ghanaian isolates shared more than 98% sequence nucleotide homology with other G9 strains from the United States (US1205), Malawi (MW69), Brazil (R160), Japan (95H115), and Nigeria (Bulumkutu). However, they showed only 95% nucleotide homology with the Thai G9 strain Mc345. Phylogenetic analysis of the nucleic acid sequence revealed the existence of at least three clusters, with Ghanaian strains forming one cluster, Nigerian and Brazilian strains forming a second cluster, and U.S., Malawian, and Japanese strains forming a third.

A cohort of 197 adults in Kassena-Nankana District (northern Ghana) was radically cured of malaria parasites to study subsequent incidence of malaria infection. During the following 20 weeks of the malaria transmission season, 49% experienced clinical attacks associated with Plasmodium falciparum parasitaemia. In a group of 202 adults identically followed-up 1 year later without being treated, only 38% experienced such episodes (log-rank test for equality of survivor functions, P=0.035). Clinical attacks in radically cured individuals presented with lower parasite densities but more symptoms. Randomized studies are needed to test the hypothesis that radical cure of P. falciparum enhances the risk and severity of subsequent clinical malaria attacks.

An epidemiological study of rotavirus infection was conducted on specimens collected from patients with gastroenteritis and domiciled in the rural Upper Eastern Region of Ghana during 1998. Fifty isolates, randomly selected from 165 human group A rotavirus-positive samples, were G and P characterized by a reverse transcription (RT)-PCR assay using a seminested multiplex method. Rotaviruses of the G3 genotype were found to be the predominant strain (78%), followed by G2 (14%) and G1 (2%). Mixed infections, as shown by combinations of G3 and G2 (4%) and G3 and G1 (2%), were also observed. P typing showed P[4] (72.34%) to be the prevalent strain, followed by P[6] (21.3%), P[8] (2.13%), and a combination of P[4] and P[6] (4.3%).

Sixty-seven rotavirus-positive fecal samples, collected between January and April 1999, from children with diarrhea in the Upper East Region of Ghana were examined for rotavirus VP7 and VP4 types. Sufficient viral RNA could be obtained from 46 (68.7%) of the samples and all the isolates had short electrophoretic pattern and typed as subgroup I rotaviruses by subgroup ELISA. Three rotavirus strains with G8 specificity were identified for the first time in Ghana. G and P typing by PCR identified two distinct strains, P[6]G2 (50%) and P[6]G8 (4.3%). Eighty-two percent of the isolates (n = 38) were of the "putative" neonatal P[6] genotype. Two of these G8 isolates carried the VP4 P[6] genotype whereas the third could not be assigned a P type. Mixed infections of G1, G2, G3 and G8 were detected amongst the stool samples. The presence of these unusual strains, especially the high incidence of G2 rotavirus strains in Ghana, reinforces the need to put in place a surveillance system for the detection of new and exotic rotavirus strains, that will provide information on the spread of these strains in West Africa as well as useful data for the formulation of the next generation of rotavirus vaccines.