Abstract: Malaria parasitaemia has been shown to be associated with abnormalities in fluid, electrolyte and acid-base balance. Sodium and potassium ions have also been shown to be indispensable in water homeostasis, necessary for survival of organisms. Serum sodium and potassium levels were analyzed in 150 confirmed malaria patients from five different hospitals in Enugu metropolis, South-East Nigeria. The patients were divided into four different age brackets; 1-10, 11-20, 21-40 and >40 years, respectively. Sixty apparently healthy, age-matched individuals were used as control subjects. The mean�SD of the sodium (Na⁺) and potassium (K⁺) levels in malaria patients of all age ranges were significantly decreased (p<0.05) when compared with the controls. Comparison of the different age brackets showed a statistically significant difference (p<0.05) between the mean�SD in the (11-20 years) age bracket compared with the other age brackets. There was however no significant difference (p>0.05) between the values obtained in the age brackets; 1-10, 21-40 and >40 years, respectively. The study shows that there is significant lowering of the Na⁺ and K⁺ levels in malaria infection. Subjects between 11-20 years were the most vulnerable in this regard from the result of the study and constitute the major risk group. Electrolytes (Na⁺ and K⁺) should be monitored in malaria patients to enhance patient management.

INTRODUCTION

Malaria is a life-threatening parasitic disease transmitted through the bite of a female anopheles mosquito (WHO, 2009). It is a disease that can be treated in just 48 h, yet it can cause fatal complications if the diagnosis and treatment are delayed (Kakkilaya, 2003). Malaria in man is caused by four distinct species of malaria parasite; Plasmodium vivax, Plasmodium falciparum, Plasmodium ovale and Plasmodium malariae. Most adults living in malaria endemic areas have partial immunity and are at risk of chronic or repeated infections (WHO, 2009). Many are asymptomatic carriers of the disease (White, 2004). Typically, malaria produces fever, headache, vomiting and other flu-like symptoms. If drugs are not available for treatment or the parasites are resistant to them, the infection can progress rapidly to become life-threatening (White, 1996; Stanley, 1997). Malaria parasites are developing unacceptable levels of resistance to one drug after another and many insecticides are no longer useful against mosquitoes transmitting the disease (WHO, 2009). Sodium is the major cation of the extra cellular fluid and as such plays a central role in the maintenance of the normal distribution of water and osmotic pressure in various fluid compartments (Tietz et al., 1996). Potassium on the other hand is the major intracellular cation having an average cellular concentration in tissue cells of 150 mmol L^-1 (Maiteki-Sebuguzi, 2008). In addition to water balance, these electrolytes play an important role in maintenance of pH, regulation of heart and muscle function, electron transfer reactions as well as serving as cofactors for enzymes (White and Kilbey, 1996). Disorders of water and balance include hyponatreamia, hypernatraemia, hypokalaemia, hyperkalaemia occur in conditions of electrolyte disturbance, such as severe malaria infection (Kakkilaya, 2003).

In human erythrocytes infected with the mature form of the malaria parasite, plasmodium falciparum, the cytosolic concentration of sodium ion is increased and that of potassium is decreased (Matthys et al., 2008). Kakkilaya (2003) observed that malaria is often associated with abnormalities of fluid, electrolytes (sodium and potassium) and acid-base balance. These can occur in any body but are more common in severe falciparum malaria, extremes of age and in patients with high degree of fever and vomiting. Nutritional status, hemoglobin type and erythrocyte glucose-6-phosphate dehydrogenase activity all influence response to malaria infection (Kaslow, 1993).

Since Sodium and potassium have been shown to be highly indispensable in water homeostasis which is fundamental to the survival of all organisms, it is therefore necessary to estimate the levels of these electrolytes in all cases of falciparum malaria and in severe malaria infection for better management of such patients.

MATERIALS AND METHODS

Subjects: The study subjects were made up of a total of one hundred and fifty confirmed malaria patients recruited from the General out-patient and the Paediatric out-patient Departments, University of Nigeria Teaching Hospital in Enugu Metropolis who reported ill with fever (axillary temperature >37.5°C) headache, vomiting, diarrhoea, respiratory distress and other clinical signs and symptoms of malaria as previously documented and also have not been placed on any anti-malarial drug. The subjects who did not meet these criteria were excluded from the study. The subjects were divided into four different age ranges; 1-10, 11-20, 21-40 and >40 years.

Sixty apparently healthy age-matched individuals were used as controls. Informed consent was obtained from all the subjects and adequate approval was given by the institute’s ethical committee before the study commenced.

Inclusion criteria: All the test subjects were confirmed malaria patients.

Exclusion criteria: Subjects with abnormal sodium and potassium levels (electrolyte imbalance) were excluded from the control group of the study.

Sample collection and preparation: Two specimen bottles were used for each subject. Anticoagulant bottles containing K₂ EDTA for malaria parasite test and plain bottles for electrolyte assay. Blood samples (5 mL) were collected by clean venepuncture from the ante-cubital fossa into already labeled bottles without undue pressure to either the arm or the plunger of the syringe. The samples were mixed by gentle inversion.

The samples in the K₂ EDTA anticoagulant bottles were tested immediately for malaria parasite, after staining their thick films with Giemsa stain, while those samples in the plain tubes were allowed to clot and the clotted samples centrifuged at 3000 rpm for 5 min to obtain the sera.

The serum supernatants were separated into sterile bottles and were used for when immediate analysis was not possible, the samples were stored in the refrigerator and analysis carried out within 4 days.

Malaria parasite density determination: The malaria parasite density was determined by examining a thick blood film stained by Giemsa method (Cheesbrough, 1998).

Classification of the degree of parasitaemia: The malaria parasite density was graded as follows:

Serum sodium and potassium analysis: The sodium and potassium in the samples were analyzed using flame emission spectrophotometric method (Tietz et al., 1996).

Procedure: One in 100 dilution of serum was made with deionized water in universal container, mixed and aspirated into the flame analyzer at a wavelength of 589 nm for sodium and 765 nm for potassium having calibrated the machine with a standard solution containing 140 mmol L^-1 Na and 4.0 mmol L^-1 of deionized water.

Statistical analysis: Data from the study was analyzed separately using paired t-test at 95% confidence interval and analysis was done using the Statistical Package for Social Sciences (SPSS). Results are presented as mean± Standard Deviation (±SD) and p<0.05 are considered significant.

RESULTS AND DISCUSSION

Table 1 shows the mean (±SD) of the Na⁺ and K⁺ in all the malaria patients and the overall control subjects.

Table 1:	Variations in serum sodium and potassium levels in all the malaria patients and control subjects

Table 2:	Mean±SD of serum sodium and potassium levels of malaria patients and control subjects in the different age brackets

Table 3:	Comparison between the (mean±SD) of serum sodium and potassium levels in different age brackets of malaria patients

Table 1 showed a statistically significant decrease (p<0.05) in both Na⁺ and K⁺ levels in the test subjects when compared with the controls.

In Table 2, the mean (±SD) of Na⁺ and K⁺ in malaria patients of different age brackets were compared statistically with the age-matched controls and there was significant differences (p<0.05) in all the age brackets, between the test subjects and their age-matched controls.

The mean values in the different age brackets were compared with one another and only the 11-20 years bracket was significantly decreased (p<0.05) when compared to the other three age brackets (Table 3).

The results of the study show that malaria infection leads to a reduction in the levels of both serum sodium and potassium. A significant difference (p<0.05) was observed between the malaria patients and the overall control subjects as well as the test subjects of all the age brackets in comparison with their age-matched controls. Mutuku et al. (2009) stated that there is a progressive decrease in the Na⁺ and K⁺ in 12 h of the parasite’s occupancy whereas Kakkilaya (2003) reported a mild hyponatraemia in malaria patients. Both findings are in line with the reductions observed in the present study. The reason for the decrease in K⁺ level might also be linked with the statements of White and Kilbey (1996) who reported that host cells loose up to 75-80% of their normal potassium content during the course of malaria attack.

The present study however revealed the vulnerability of the 11-20 years age bracket being the age group with a significant decrease in Na⁺ and K⁺ levels in malaria infection. The reason for this is not fully known. The study further shows the importance of electrolyte management in malaria patients to prevent electrolyte (Na⁺ and K⁺) depletion.

CONCLUSION

The study draws attention to the need to manage electrolyte derangements in the overall management of malaria infections. The age-related effect that made the 11-20 years age bracket to appear most vulnerable should be further investigated and always taken into consideration in management and treatment of malaria in patients of this age bracket.

In general, serum electrolytes should be estimated in malaria patients of all ages to prevent complications which might result from electrolyte depletion, as these may have grave consequences.