IMMUNOLOGICAL STUDIES ON Plasmodium falciparum HISTIDINE RICH- PROTEIN2 (PfHRP2) GENE DELETION AMONGST SYMPTOMATIC MALARIA PARASITAEMIC PATIENTS IN KADUNA METROPOLIS
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Abstract
Malaria is a major public health challenge worldwide with high morbidity and mortality. For prompt and accurate diagnosis, the World Health Organization (WHO) recommends
rapid diagnostic test (RDT) as good alternative method for malaria diagnosis in sub- Sahara Africa prior to drug administration and treatment. Malaria RDTs are commercially
available test kits and majority detects Plasmodium falciparum Histidine-rich protein-2
(PfHRP2 gene) as the target antigen. The WHO then recommends that PfHRP2 gene
deletion must be monitored, especially in Africa. The aim of this study was to determine
PfHRP2 gene deletion in blood samples of malaria parasitaemic patients in Kaduna
metropolis. The Study was carried out using microscopy, PCR and RDT. All RDT- negative samples were further subjected to microscopy and molecular analysis (PCR) for
malaria parasite speciation and PfHRP2 gene and deletion. Of the 1196 samples analysed, 694 were negative and 502 were positive by RDT. Of the RDT negatives, 83 samples
were found to be microscopically positive, the 78 samples were for Plasmodium
falciparum species and 5 non-falciparum species (2P. Vivax, 2P. malariae, 1P. falciparum/Vivax). These 83 samples were further subjected NM-PCR and were equally
found positive for malaria, hence classified as RDT false–negatives. Statistical analysis
for frequencies and confidence intervals (Cl) was used for prevalence estimates. Associations were assessed by chi square test. The level of significance was set at P<0.05. The significance package used was Minitab 22.1. From the 83 samples identified as RDTfalse negative by PCR; 69 (5.8%) 95% Cl 4.6-7.0), had gene deletion both in PfHRP2
and PfHRP3, 4 samples (0.33%) 95% CI - 0.94-1.54) had deletion only in PfHRP2 but
not in PfHRP3 and 5 samples (0.42%) 95% CI-0.84-1.64) had deletion in PfHRP3 but not
in PfHRP2. With particular interest and considering PfHRP2 gene only within the total of
1196 samples 73(6.1%) 95% 4.76- 7.44) had evidence of deletion. This study provides
evidence of PfHRP2 gene deletion in Plasmodium falciparum in Kaduna and PfHRP2
deletion was detected in the 73 samples analysed. This surveillance study also discovered
that there is no significant difference (p<0.001) in Plasma level of CRP, IFN- and IL-6 of
blood samples of participants with intact PfHRP2 gene and those with PfHRP2 gene
deletion. It is, therefore, highly recommended that more surveillance studies across
different geographical zone of the country be carried out to determine the full extent of
PfHRP2 deletion frequencies. It also recommended that routine RDT kit contain
additional PfHRP3 antigen, to improve the RDT efficacy and provide broad spectrum of
diagnosis
rapid diagnostic test (RDT) as good alternative method for malaria diagnosis in sub- Sahara Africa prior to drug administration and treatment. Malaria RDTs are commercially
available test kits and majority detects Plasmodium falciparum Histidine-rich protein-2
(PfHRP2 gene) as the target antigen. The WHO then recommends that PfHRP2 gene
deletion must be monitored, especially in Africa. The aim of this study was to determine
PfHRP2 gene deletion in blood samples of malaria parasitaemic patients in Kaduna
metropolis. The Study was carried out using microscopy, PCR and RDT. All RDT- negative samples were further subjected to microscopy and molecular analysis (PCR) for
malaria parasite speciation and PfHRP2 gene and deletion. Of the 1196 samples analysed, 694 were negative and 502 were positive by RDT. Of the RDT negatives, 83 samples
were found to be microscopically positive, the 78 samples were for Plasmodium
falciparum species and 5 non-falciparum species (2P. Vivax, 2P. malariae, 1P. falciparum/Vivax). These 83 samples were further subjected NM-PCR and were equally
found positive for malaria, hence classified as RDT false–negatives. Statistical analysis
for frequencies and confidence intervals (Cl) was used for prevalence estimates. Associations were assessed by chi square test. The level of significance was set at P<0.05. The significance package used was Minitab 22.1. From the 83 samples identified as RDTfalse negative by PCR; 69 (5.8%) 95% Cl 4.6-7.0), had gene deletion both in PfHRP2
and PfHRP3, 4 samples (0.33%) 95% CI - 0.94-1.54) had deletion only in PfHRP2 but
not in PfHRP3 and 5 samples (0.42%) 95% CI-0.84-1.64) had deletion in PfHRP3 but not
in PfHRP2. With particular interest and considering PfHRP2 gene only within the total of
1196 samples 73(6.1%) 95% 4.76- 7.44) had evidence of deletion. This study provides
evidence of PfHRP2 gene deletion in Plasmodium falciparum in Kaduna and PfHRP2
deletion was detected in the 73 samples analysed. This surveillance study also discovered
that there is no significant difference (p<0.001) in Plasma level of CRP, IFN- and IL-6 of
blood samples of participants with intact PfHRP2 gene and those with PfHRP2 gene
deletion. It is, therefore, highly recommended that more surveillance studies across
different geographical zone of the country be carried out to determine the full extent of
PfHRP2 deletion frequencies. It also recommended that routine RDT kit contain
additional PfHRP3 antigen, to improve the RDT efficacy and provide broad spectrum of
diagnosis
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