Genetic Diversity and Protective Efficacy of the RTS,S/AS01 Malaria Vaccine.

BACKGROUND: The RTS,S/AS01 vaccine targets the circumsporozoite protein of Plasmodium falciparum and has partial protective efficacy against clinical and severe malaria disease in infants and children. We investigated whether the vaccine efficacy was specific to certain parasite genotypes at the circumsporozoite protein locus. METHODS: We used polymerase chain reaction-based next-generation sequencing of DNA extracted from samples from 4985 participants to survey circumsporozoite protein polymorphisms. We evaluated the effect that polymorphic positions and haplotypic regions within the circumsporozoite protein had on vaccine efficacy against first episodes of clinical malaria within 1 year after vaccination. RESULTS: In the per-protocol group of 4577 RTS,S/AS01-vaccinated participants and 2335 control-vaccinated participants who were 5 to 17 months of age, the 1-year cumulative vaccine efficacy was 50.3% (95% confidence interval [CI], 34.6 to 62.3) against clinical malaria in which parasites matched the vaccine in the entire circumsporozoite protein C-terminal (139 infections), as compared with 33.4% (95% CI, 29.3 to 37.2) against mismatched malaria (1951 infections) (P=0.04 for differential vaccine efficacy). The vaccine efficacy based on the hazard ratio was 62.7% (95% CI, 51.6 to 71.3) against matched infections versus 54.2% (95% CI, 49.9 to 58.1) against mismatched infections (P=0.06). In the group of infants 6 to 12 weeks of age, there was no evidence of differential allele-specific vaccine efficacy. CONCLUSIONS: These results suggest that among children 5 to 17 months of age, the RTS,S vaccine has greater activity against malaria parasites with the matched circumsporozoite protein allele than against mismatched malaria. The overall vaccine efficacy in this age category will depend on the proportion of matched alleles in the local parasite population; in this trial, less than 10% of parasites had matched alleles. (Funded by the National Institutes of Health and others.).

Extrapulmonary and disseminated tuberculosis in HIV-1-seropositive patients presenting to the acute medical services in Nairobi.

We studied 506 consecutive adult acute medical admissions to hospital in Nairobi; 95 (18.8%) were seropositive for HIV-1, and 43 new cases of active tuberculosis (TB) were identified. TB was clearly associated with HIV infection, occurring in 17.9% of seropositive patients compared with 6.3% of seronegatives [odds ratio (OR) 3.2; 95% confidence limits (CL) 1.6-6.5]. Extrapulmonary disease was more common in seropositive than seronegative TB patients (nine out of 17 versus five out of 26; OR 4.7; 95% CL 1.01-23.6); this accounted for most of the excess cases of TB seen in seropositive patients. Mycobacteraemia was demonstrated in two of eight seropositive TB patients but in none of 11 seronegative TB patients. No atypical mycobacteria were isolated. The World Health Organization (WHO) clinical case definition for African AIDS did not discriminate well between seropositive and seronegative TB cases. Five out of seven seropositive women with active tuberculosis had delivered children in the preceding 6 months and were lactating, compared with only one out of eight seronegative tuberculous women. An association between recent childbirth, HIV immunosuppression and the development of TB is suggested.

Recombinant DNA probes reveal simultaneous infection of tsetse flies with different trypanosome species.

The utility of recombinant DNA probes in the detection of natural trypanosome infection of tsetse flies has been assessed in Lambwe Valley, near the shores of Lake Victoria, Kenya. The tsetse flies were surveyed during two different seasons in 1988. Three different probes used each contained highly repetitive DNA sequences specific for a species or subspecies of trypanosomes of the Nanomonas subgenus. A fourth probe contained repetitive sequences common to trypanosome species of the Trypanozoon subgenus. Mixed mature or immature infections were detected in a variety of combinations in different individual tsetse flies. Such infections were detected in both the guts and mouthparts of some tsetse flies. Simultaneous natural infection of tsetse with the savannah type Trypanosoma congolense and Kilifi type T. congolense, T. congolense and Trypanosoma brucei or T. congolense and Trypanosoma simiae were demonstrated. The probes have thus been used to demonstrate the presence of Lambwe Valley, south-western Kenya, of a type of T. congolense first observed among trypanosome isolates obtained from sentinel cattle exposed to natural infection on a ranch at Kilifi on the Kenya coast. This type of T. congolense appears not to be confined to the coastal region nor to any particular species of tsetse flies and may contribute significantly to livestock morbidity in other areas of eastern Africa. In the Kilifi area, T. congolense was found primarily in Glossina austeni; in Lambwe valley, it was found in Glossina pallidipes.

The presence in salivary secretions of Glossina morsitans of stages of Trypanosoma (Trypanozoon) brucei other than those occurring in the salivary glands.

Using the bat wing membrane technique to study salivary secretions of Glossina morsitans infected with Trypanosoma (Trypanozoon) brucei, it was shown that flies extrude infected salivary secretions as early as day six after an infective blood meal. The non-salivary-gland stages of T. (T.) brucei were extruded intermittently and flies infected with such trypanosomes were not all destined to develop metacyclic infections. Once the salivary glands were involved, the trypanosomes appeared in the secretions each time the flies were tested. Some of the flies with gut infections, but no demonstrable salivary gland involvement, transmitted T. brucei to mice and it is suggested that these infections were intiated by some of the proventricular trypanosomes secreted with saliva.

Development of Trypanosoma (Trypanozoon) brucei in Glossina morsitans inoculated into the tsetse haemocoel.

Classically, infective development of Trypanosoma (Trypanozoon) brucei in tsetse flies is thought to take the route crop-midgut-hindgut proventriculus-hypopharynx-salivary gland, where the parasites reach their infective phase. It has been shown experimentally that T. (T.) brucei is capable of developing up to the infective stage in G. morsitans following inoculation of bloodstream form trypanosomes into the haemocoel. The rabbit on which flies were maintained became infected 18 days after exposure to the bite of experimentally inoculated flies. The possibility that T. (T.) brucei may be transmitted cyclically from tsetse flies to a mammalian host without necessarily following the classical, prescribed route is discussed. Apart from the normal longitudinal binary fission, various modes of multiplication were observed among trypanosomes in the haemocoel, modes which have not been observed previously in the tsetse fly.

Influence of D(+)-glucosamine on infection rates and parasite loads in tsetse flies (Glossina spp.) infected with Trypanosoma brucei.

Teneral Glossina morsitans centralis, G. m. morsitans and G. pallidipes were infected with three different clones of Trypanosoma brucei in blood containing D(+)-glucosamine, an inhibitor of tsetse midgut lectin. On average, 5 days of D(+)-glucosamine treatment tripled infection rates, without affecting the proportion of infections that matured. Total infection rates were equal in males and females, but twice as many infections matured in males. Counts of parasites in the guts and salivary glands of 277 flies revealed order of magnitude differences among flies, with females consistently having 2-3-times as many parasites as males. Parasite numbers varied in a sex-specific manner among tsetse-clone combinations, but these differences were not correlated with similar large differences in infection rates. D(+)-glucosamine treatment had no significant effect on parasite loads.

Selection for drug resistance in Trypanosoma congolense during cyclic transmissions through Glossina morsitans morsitans and drug treated rabbits.

A drug-sensitive Trypanosoma congolense (IL 1180 strain), with a known CD50 and CD90 (doses required to cure 50 and 90% of the infected animals) was cyclically passaged through tsetse flies. The infected flies were then fed on rabbits which received weekly prophylactic treatment of Samorin. It was observed that the infections arising from flies maintained for over 60 days on drug-treated rabbits required higher curative doses to achieve a 50 and 90% cure. The results of this work suggest that a selection for drug resistance occurs when trypanosome stage in Glossina is continuously exposed to drug-treated animals.

Increased sensitivity to a natural pyrethrum extract of Trypanosoma-infected Glossina morsitans.

Topical application of a natural pyrethrum extract on male and pregnant female Glossina morsitans morsitans resulted in higher mortality for flies infected with Trypanosoma brucei brucei than for uninfected control flies. Infected males showed a significantly higher mortality while infected pregnant females showed a marginally significant increase in mortality. Results support the hypothesis that infected flies are less healthy than uninfected flies. Results also parallel previous findings using endosulfan as the topical applicant and exclude the likelihood that the results were because of a peculiar effect of endosulfan.

Some observations on factors associated with the development of Trypanosoma brucei brucei infections in Glossina morsitans morsitans.

The susceptibility of Glossina morsitans morsitans to Trypanosoma brucei brucei infection was shown to be age-dependent during the first 12 h: the youngest age group (1-8 h after emergence) being more susceptible than the older ones. The susceptibility was enhanced by cooling the young flies to a temperature of 0-5 degrees C for 30 min. Male flies were found to be more susceptible than females. The number of trypanosomes ingested did not influence the subsequent salivary-gland infection rates observed in G.m. morsitans; however, there was a relationship between the number ingested and subsequent T.b. brucei midgut infections in the flies.

Defence reactions of Glossina morsitans morsitans against different species of bacteria and Trypanosoma brucei brucei.

Tsetse flies, Glossina morsitans morsitans, fed on rats infected with Trypanosoma brucei brucei showed wide fluctuations in total and differential haemocyte counts. Similar fluctuations occurred in controls fed on non-infected rats and also between the two groups without showing any difference which could be attributed to the infection. Trypanosome infection of the tsetse haemocoel occurred in 16.25% of the flies, starting from the second day after feeding on the infected rats, but salivary glands and proboscis became infected only after the eleventh day. About 2% of bloodstream forms of T. b. brucei injected into tsetse haemocoels completed their developmental cycle successfully. Injection of tsetse homogenates into teneral G. m. morsitans prior to exposure to trypanosome-infected feed increased T. b. brucei infections in the flies significantly. Injection of live Escherichia coli, Enterobacter cloacae and Acinetobacter calcoaceticus into tsetse induced a remarkable increase in two pre-existing haemolymph proteins with molecular weights of about 70 and 17 kilodaltons, while live Bacillus subtilis and Micrococcus luteus induced a very weak response or sometimes none at all. T. b. brucei also failed to induce any increase in these proteins. Inoculation of G. m. morsitans with live E. coli und T. b. brucei prior to feeding on trypanosome-infected rats had no effect on the salivary gland and proboscis infection rates by T. b. brucei. Injection of live T. b. brucei into the haemocoels of tsetse caused no change in total haemocyte counts, but the trypanosomes disappeared from the haemolymph so rapidly that by 48 h post-injection, only about 1% were left.

Diabetic ulcers--a clinical and bacteriological study.

One hundred consecutive patients with diabetic ulcers were studied in an 8-month-period. There were 58 females. The mean age was 59.9 years. Eighty three patients had non-insulin dependent diabetes mellitus. The mean duration of diabetes mellitus was 11.6 years. The mean duration of the ulcer was 8.5 months. Sixty nine of the ulcers were gangrenous. Over 50% of the ulcers involved the big toes. Neuropathic ulcers were found mainly in the sole of the feet. Roentgenograms showed evidence of osteomyelitis in 44 patients. There were 356 bacterial isolates (340 aerobes and 16 anaerobes) from the ulcers. There were 3.6 infecting organisms per ulcer in gangrenous ulcers, while in neuropathic ulcers, there were 3.4 infecting organisms per ulcer. In both types of ulcer Staphylococcus aureus and Escherichia coli were the commonest infecting organisms each being isolated in 88 of the 100 ulcers studied. In repeat bacterial cultures at 4 weeks there were 116 bacterial isolates. Staphylococcus aureus persisted in 63 ulcers despite therapy, while Escherichia coli persisted in 35. There were no new organisms isolated at repeat cultures and no ulcer was completely sterile. The Staphylococcus aureus was 100% sensitive to Augmentin (Amoxicillin plus clavulinic acid), Clindamycin, Novobiocin, and Amikacin while the gram negative bacilli were sensitive to Cefotaxime, Piperacillin, Amikacin and augmentin, Clindamycin, Chloramphenicol and Lincomycin inhibited the growth of anaerobes to a varying degree.

Renal failure diagnosis and management.

Acute and chronic renal failure (ARF and CRF) are primary health problems in health centres, district and provincial hospitals. Their managements should be initiated in these areas of the health services. Some of the managements of CRF & ARF should be initiated in private clinics by private practitioners. ARF is a medical emergency while CRF is insidious with non-specific features. Discussions on CRF and ARF and their timely managements are mandatory if the mortality and morbidity associated with them are to be prevented.

Acute renal failure as seen at Kenyatta National Hospital.

Forty seven patients with acute renal failure were studied prospectively over a two-year period at the Kenyatta National Hospital. There were 20 males and 27 females. The mortality rate was 40.4%. Most patients had medically oriented problems. Complications that were associated with a high mortality were infections and the presence of neuropsychiatric manifestations.

Acute renal failure following the use of herbal remedies.

Acute renal failure (ARF) complicated the use of traditional herbal remedies in six adult patients seen at Kenyatta National Hospital in a 2-year period (August 1984 to August 1986). This comprised 10.9% of all the cases of ARF and 24% of the cases of ARF due to medical causes. All the patients were oliguric and the period of oliguria in the four patients who survived ranged between 19-57 days (mean 26.3 days). Five of the patients had evidence of fluid overload. The blood urea nitrogen and serum creatinine were elevated in all the patients. The serum sodium was normal in all, while the serum potassium was elevated in 2 cases. Identity of the herbal medication was unknown in all the cases. The indication was abdominal pain in 4 cases, infertility and abdominal pain in one and prophylaxis against witchcraft in the other. All the patients were started on haemodialysis, two of them having had periods of peritoneal dialysis for 12 and 16 days. Two patients died. Of the four surviving patients, follow up has been carried out for 8, 6, 5 and 4 months. At four months follow up the creatinine clearance in the 4 surviving patients have been 54, 63, 51 and 43 ml/min.

Bacteriuria in patients with glomerular diseases.

In a comparative study of significant bacteriuria in an African population, 1.7% of 697 healthy subjects (10 females and 2 males) were found to have positive urine cultures. Of these, 5 subjects grew E. coli, 4 Klebsiella strains, 2 Staphylococcus aureus and 1 Serratia marcescens. Among 116 patients with glomerular disease, 15.5% (7 males and 11 females) yielded positive cultures. E. coli, Staph. aureus and Proteus species were commonly isolated organisms. There was a nine fold increase in prevalence of bacteriuria in patients with glomerular disease and in females, this correlated with the amount of protein lost per 24 hours. It is postulated that the presence of protein in urine per se favours bacterial growth and because of the high prevalence of bacteriuria in patients with glomerular disease, it is recommended that all such patients should be screened and treated appropriately.

Intestinal parasitoses and other infections in a college community.

In order to assess the health status of students doing their teaching diploma course at the Siriba Teachers College, Maseno, a study of their blood slides, their stools for ova and cysts and their urine samples for urinary tract infection was carried out. A total of 298 students were investigated: 27 (6%) had intestinal parasites, 96 (32.2%) had urinary tract infection, i.e., pyuria, bacteria and epithelial cells in their urines, most of them being females (55/96 or 57.3%). The peak occurrence of urinary tract infections was in the 22-23 year age group. There were four female students who were found to have Trichomonas vaginalis giving a prevalence rate of 1.3%.

Thyroid hormone profiles in patients with chronic renal failure on conservative management and regular haemodialysis.

Patients with chronic non-thyroid illness (NTI) generally show biochemical features of hypothyroidism despite their being clinically euthyroid. Using assays that employ the antibody coated tubes technique, we measured thyroid hormone levels in 52 patients with chronic renal failure. 30 of the patients were on conservative management while 22 were on regular haemodialysis (HD) for a mean period of 14.2 +/- 9.9 months. The findings were compared to those of 14 healthy controls. All patients were clinically euthyroid. Only 3 patients on HD had goitres. The mean value of total thyroxine (TT4) total triiodo thyronine (TT3), free thyroxine (FT4) and the free triiodothyronine (FT3) were low in patients compared with controls (P less than 0.01). The mean basal thyroid stimulating hormone (TSH) levels were significantly higher in patients than in controls (P less than 0.001). There were no significant differences in all parameters between the patients on conservative management and those on haemodialysis (P greater than 0.05). Although all patients were clinically euthyroid, the biochemical features suggest hypothyroidism.

Surgical aspects of live donor kidney transplants in Kenya.

Review of twenty cases of live-donor kidney transplants in Kenya for a period of 5 years (1985-1989) and the follow up study results revealed that there were both high graft losses, high morbidity and mortality due to various complications pertaining to surgery and immunosuppression. The most serious complications were intercurrent infections, acute or chronic rejection, pulmonary embolism, steroid induced diabetes, pneumonia, and myocardial infarction. At the end of the first year follow up, there were only twelve graft patients alive. Magnetic Resonance Imaging (MRI) was not available for assessing the anatomical and functional behaviour of the transplanted kidneys. This would have assisted in early diagnosis of the degree and onset of rejection for appropriate treatment before the death of the allografts. It would also assist in differentiating perfusional problems from rejection.

Asymptomatic bacteriuria among diabetics attending Kenyatta National Hospital.

Significant asymptomatic bacteriuria is an important cause of pyelonephritis and gram negative septicaemia among certain predisposed individuals, such as diabetics. We investigated the incidence of asymptomatic urinary tract infections (UTIs) among our diabetic patients and the type and antibacterial sensitivity patterns of the organisms causing these UTIs. One hundred and thirty five patients submitted midstream urine specimens for culture. Fifteen patients had positive cultures showing the incidence of asymptomatic UTI to be 11.1%. There were ten female and five male patients with UTI. The commonest organism isolated was Escherichia coli at 40%. Gram negative bacilli made up 66.7% of the isolates. Isolates were poorly sensitive to the regularly available antibiotics-ampicillin (33% sensitive, cotrimoxazole (33% sensitive). Nitrofurantoin inhibited growth in 93% of the isolates. Other antimicrobials with over 80% sensitivity level included: gentamicin, ceftazidime, augmentin, cefuroxime and norfloxacin. They are expensive or require parenteral administration. The incidence of asymptomatic UTI is high among diabetics and although the organisms isolated are those usually isolated in UTIs, they are not that sensitive to the commonly available and antibacterial agents.

Urinary tract stone disease in Nairobi.

At the Kenyatta National Hospital (KNH) and other private hospitals in Nairobi urinary stone disease is not being correctly diagnosed. Over a 15 year period (1980-1995) only 56 patients have been confirmed to have urinary tract stones out of the expected number of 220 patients. The age range was 10-60 years. The peak age was 30-40 years. Pain and haematuria were the commonest presenting symptoms. Ultrasonography and plane abdominal radiology were the commonest methods of diagnosis. Open surgery and endoscopic stone removal were the commonest modes of management. Extracorporeal shortwave lithotripsy (ESWL) has recently been introduced into the Nairobi Hospital, but was not functional at the time of this study. Percutaneous nephrolithotomy (PCNL) is possible but has not been adequately used due to lack of correct equipment. Septicaemia and haemorrhage were the commonest complications of the open surgery.