ABSTRACT
The prevalence and severity of hypoglycaemia and lactic acidosis in Nigerian children diagnosed with Plasmodium falciparum malaria were determined in 100 outpatient children aged 3-144 months (12 years). The children were grouped into 2 categories: 3-59 month old and 60-144 month old. The results obtained indicated that out of the 100 children recruited into this study, seventy-five (75%) were infected while twenty-five (25%) were uninfected with Plasmodium falciparum malaria. On the basis of age group, higher incidence of malaria was recorded in children under 5 years of age with prevalence rate of 85.3%, while those above 5 years had low prevalence rate of 14.7%. The mean blood glucose concentration of malaria-infected children below 5 years (3.80 ± 0.73 mmol/l) was lower than that of malaria-infected children above 5 years (4.21 ± 1.34 mmol/l); however, the difference was not significant (p>0.05). Comparatively, the mean glucose concentrations of the corresponding uninfected subjects were 4.10 ± 0.87 and 4.26 ± 0.51 mmol/l respectively. The mean blood lactate concentration of children below 5 years of age (2.59 ± 1.63 mmol/l ) was significantly (p<0.05) higher than those above 5 years (2.30 ± 1.75 mmol/l). The mean values for both groups were also above the normal range of 1.0 – 2.0 mmol/l while the mean haemoglobin concentration of malaria-infected children below 5 years (16.11 ± 2.24 g/dl) was slightly lower than that of malaria-infected children above 5 years (16.36 ± 2.64g/dl) though not significant (p> 0.05). The prevalence rates of 14.7% were recorded for both hypoglycaemia and lactic acidosis in malaria-infected subjects while 16.0% was recorded for anaemia. There was no significant correlation between blood lactate concentration and blood glucose concentration (r= 0.032, p=0.751) but there was significant positive correlation between haemoglobin level and glucose concentration (r=0.401, p=0.0001). The results suggest that the risk of hypoglycaemia, lactic acidosis and anaemia is higher in younger children, particularly among those below five years of age and also confirmed the knowledge that malaria is a major cause of hospital visits by children.
TABLE OF CONTENTS
PAGE
Title Page i
Certification ii
Dedication iii
Acknowledgements iv
Abstract v
Table of Contents vi
List of Figures x
List of Tables xi
List of Abbreviations xii
CHAPTER ONE: INTRODUCTION
1.1 Malaria 2
1.1.1 World malaria report 3
1.1.2 Malaria in children 5
1.1.3 Malaria parasite life cycle 5
1.1.3.1 Sporogony within the mosquitoes 5
1.1.3.2 Schizogony in the human host 6
1.1.3.3 Pre-erythrocytic phase-schizogony in the liver 6
1.1.3.4 Erythrocytic schizogony-centre stage in red cells 7
1.1.4 Pathogenic basis of malaria 9
1.1.5 Pathophysiology of severe malaria in children 11
1.1.6 Cytokine-associated neutrophil extracellular traps and antinuclear
antibodies in Plasmodium falciparum 12
1.2 Biochemistry of Plasmodium falciparum 13
1.2.1 Detoxification of heme and reactive oxygen intermediates 17
1.2.2 Biochemistry and molecular biology of malaria parasite:
pyrimidine biosynthetic pathway 18
1.2.3 Complication of Plasmodium falciparum malaria 20
1.2.4 Prevalence and management of Plasmodium falciparum malaria
among infants and children 22
1.3 Hypoglycaemia in childhood malaria 22
1.3.1 Sublingual sugar for hypoglycaemia in children with severe malaria 24
1.4 Lactic acidosis in childhood malaria 24
1.4.1 Lactate levels in severe malarial anaemia 25
1.5 Transport of lactate and pyruvate in Plasmodium falciparum malaria 26
1.6 Anaemia in childhood malaria 27
1.6.1 Severity of anaemia in children diagnosed with Plasmodium falciparum
malaria 28
1.7 Typhoid and malaria co-infection 28
1.8 Aim and objectives of the study 29
1.8.1 Aim of the study 29
1.8.2 Specific objectives of the study 29
CHAPTER TWO: MATERIALS AND METHODS
2.1 Materials 30
2.1.1 Subjects and location 30
2.1.2 Instruments/Equipment 30
2.1.2.1 Accutrend plus meter 30
2.1.2.2 Crista haemoglobinometer 31
2.1.3 Reagent kit/ Test strips 31
2.1.3.1 Malaria diagnostic rapid test kit 31
2.1.3.2 Glucose reagent strip 31
2.1.3.3 Lactate reagent strip 31
2.2 Methods 31
2.2.1 Preparation of 70% (v/v) ethanol 31
2.2.2 Experimental design 32
2.2.3 Malaria diagnostic test 32
2.2.4 Biochemical parameters determined 33
2.2.4.1 Determination of blood glucose concentration 33
2.2.4.2 Determination of blood lactate concentration 34
2.2.5 Haematological parameter determined 35
2.2.5.1 Estimation of haemoglobin concentration 35
2.3 Statistical analysis 35
CHAPTER THREE: RESULTS
3.1 Prevalence of Plasmodium falciparum malaria according to age of subjects 36
3.2 Blood glucose levels in malaria-infected and uninfected subjects 37
3.3 Blood lactate levels in malaria-infected and uninfected subjects 38
3.4 Haemoglobin levels in malaria-infected and uninfected subjects 39
3.5 Variation of glucose concentration with age of malaria-infected
subjects 40
3.6 Variation of lactate concentration with age of malaria-infected
subjects 41
3.7 Variation of haemoglobin concentration with age of malaria-infected
subjects 43
3.8 Effect of Plasmodium falciparum parasite load on the blood glucose
concentration of subjects 44
3.9 Effect of Plasmodium falciparum parasite load on the blood lactate
concentration of subjects 46
3.10 Effect of Plasmodium falciparum parasite load on haemoglobin
concentration of subjects 47
3.11 Comparison of glucose concentration of malaria-infected and
uninfected subjects 48
3.12 Comparison of lactate concentration of malaria-infected and
uninfected subjects 49
3.13 Comparison of haemoglobin concentration of malaria-infected and
uninfected subjects 50
3.14 Correlations matrix 51
CHAPTER FOUR: DISCUSSION
4.1 Discussion 53
4.2 Conclusion 56
4.3 Suggestions for further studies 56
REFERENCES 57
APPENDICES 76
LIST OF FIGURES
Fig 1: World malaria burden (World Malaria Report, 2011) 4
Fig. 2: Ingestion of host cytoplasm 15
Fig. 3: Variation of glucose concentration with age of malaria-infected
subjects 40
Fig. 4: Variation of lactate concentration with age of malaria-infected
subjects 42
Fig. 5: Variation of haemoglobin concentration with age of malaria-infected
subjects 43
Fig. 6: Effect of Plasmodium falciparum parasite load on the blood glucose
concentration of subjects 45
Fig. 7: Effect of Plasmodium falciparum parasite load on the blood lactate
concentration of subjects 46
Fig. 8: Effect of Plasmodium falciparum parasite load on haemoglobin
concentration of subjects 47
Fig. 9: Comparison of glucose concentration of malaria-infected and
uninfected subjects 48
Fig. 10: Comparison of lactate concentration of malaria-infected and
uninfected subjects 49
Fig. 11: Comparison of haemoglobin concentration of malaria-infected and
uninfected subjects 50
LIST OF TABLES
Table 1: Indicators of severe malaria and poor prognosis 21
Table 2: Prevalence of Plasmodium falciparum malaria according to age of subjects 36
Table 3: Blood glucose concentration (BGC) in malaria-infected and uninfected
subjects 37
Table 4: Blood lactate concentration (BLC) in malaria-infected and uninfected
subjects 38
Table 5: Haemoglobin concentration (HC) in malaria-infected and uninfected
subjects 39
Table 6: Correlations matrix 52
LIST OF ABBREVIATIONS
µl: Microlitre
ABC: ATP-binding cassette
ANOVA: Analysis of Variance
ATC: Aspartate transcarbamylase
ATP: Adenosine triphosphate
BGC: Blood glucose concentration
BLC: Blood lactate concentration
CPS : Carbamyl phosphate synthase
CRP: C-reactive protein
DBL: Duffy binding-like
de novo: From the beginning
DHO: Dihydroorotase
DHOD: Dihydroorotate dehydrogenase
DNA: Deoxyribonucleic acid
DPAP: Dipeptidyl aminopeptidase
DRC: Democratic Republic of the Congo
Fe2+: Ferrous ion
Fe3+: Ferric ion
GSH: Reduced glutathione
H+: Hydrogen ion
HC: Haemoglobin concentration
HCl: Hydrochloric acid
HCM: Hz-containing monocytes
HCN: Hz-containing neutrophils
HCO3: Bicarbonate
HRP: Histidine-rich protein
Hz: Haemozoin
IFN-y: Interferon gamma
IgG: Immunoglobulin G
IgM: Immunoglobulin M
IL: Interleukin
LED: Light-emitting diode
MCTs: Monocarboxylate transporters
NAD+: Nicotinamide adenine dinucleotide
NADH: Reduced form of nicotinamide adenine dinucleotide
NETs: Neutrophil extracellular traps
OMPDC: Orotidine 5’-monophosphate decarboxylase
OPRT: Orotate phosphoribosyltransferase
pCMBS: p chloromercuribenzenesulphonate
Pfmdr-1: Plasmodium falciparum multidrug resistance protein/gene
pHi: Intracellular pH
pLDH: Plasmodium lactate dehydrogenase
ppm: Parasite plasma membrane
PVM: Parasitophorous vacuole membrane
RBC: Red blood cell
RNA: Ribonucleic acid
ROI: Reactive oxygen intermediates
SD: Standard deviation
SEARO/WPRO: South-East Asia and Western Pacific Regional Office
SOD: Superoxide dismutase
SPPS: Statistical product and service solutions
TNF-α: Tumor necrosis factor alpha
TRAP: Thrombospondin-related anonymous protein
UMP: Uridine 5’ monophosphate
WHO/AFRO: World Health Organization Regional Office for Africa
CHAPTER ONE
INTRODUCTION
Plasmodium falciparum is the most common cause of severe and life-threatening malaria, which causes over 2 million deaths every year (Bruneel et al., 2003; Njuguna and Newton, 2004). In Africa, a vast majority of these deaths occur in children under five years of age (WHO, 2012). Lactic acidosis complicates 35% of severe childhood malaria (Krishna et al., 1994) and hypoglycaemia is present in 20% of children with cerebral malaria (Newton and Krishna, 1998). Both acidosis and hypoglycaemia commonly coexist but each is considered separately as a cause of fatality in children and adults due to severe complicated malaria. Hypoglycaemia is known to be an independent risk factor for death in both severe malaria (Gray et al., 1985; Molyneux et al., 1989) and other severe childhood infections in the tropics (Kawo et al., 1990). Despite its importance, its pathogenesis is not well understood (English et al., 1998). Hypoglycaemia is associated with a poor prognosis in severe malaria (krishna et al, 1994).
In African children with malaria, impairment in hepatic gluconeogenesis in the presence of adequate levels of precursors (glycerol) has been considered the most likely mechanism (White et al., 1987). Irreversible coma may quickly develop if the condition is not effectively treated. Hyperlactataemia is often associated with a poor outcome in severe malaria in African children (Krishna et al, 1994). The pathophysiology of metabolic acidosis is complex. The direct contribution of P. falciparum to the final lactate concentration, through anaerobic glycolysis in the parasite itself, is likely to be small (Vander et al., 1990). More significantly, an inadequate supply of oxygen to tissues may follow from severe anaemia and provoke a metabolic shift within host cells to anaerobic glucose metabolism and increased lactic acid production. In addition, the flow of blood through the microcirculation may be impeded by adherence of infected erythrocytes to the endothelium of post-capillary venules and/or increased rigidity of uninfected cells (Dondrop et al., 1997). Lactate may not in itself be sufficient to cause acidaemia but the inhibition of oxidative metabolism in the context of an ongoing inflammatory response will cause protons (H+) to accumulate and eventually lead to metabolic acidosis (English et al.,1997). These pathophysiological pathways suggest that the syndrome of lactic acidosis may be associated with the total parasite burden during acute infection.