GENETIC DIVERSITY OF PLASMODIUM FALCIPARUM AND ANTIBODY RESPONSES TO ERYTHROCYTE SURFACE ANTIGENS AMONG CHILDREN IN MINNA, NIGERIA

Abstract

Malaria is a major global public health concern especially in countries where transmission occur regularly. A larger proportion of the malaria cases that resulted in mortality occurred among children less than five years old. This cross sectional study was aimed at determining the genetic diversity of Plasmodium falciparum and antibody responses to erythrocyte surface antigens among children in Minna, Nigeria. Blood samples were collected from children with no signs of fever (asymptomatic cases) within the residential communities in Minna, and children with symptoms of fever (symptomatic cases) who attended selected healthcare facilities within the period of the study. Thick and thin films of blood samples were prepared using Giemsa staining technique to determine the parasite density and the infective stage. Subsequently, a complete blood count to determine the haematological indices of the blood samples was carried out. Blood samples were exposed to enzyme linked immunosorbent assay (ELISA) for the measurement of IgG antibody levels against P. falciparum. Samples were further analyzed for the molecular characterization and gene type using polymerase chain reaction (PCR). A total population of 316 children both symptomatic and asymptomatic were sampled for this study from children between 6 months and 17 years between the months of February to July, 2018. The sampled population comprises 181 (57 %) males and 135 (43 %) females. Of the 316 blood samples screened for P. falciparum infection, 238 (75.37 %) were infected with P. falciparum which comprises of 39 (16.39 %) from asymptomatic children from the communities and 199 (83.61 %) symptomatic children attending the six healthcare facilities. The male and female categories recorded a P. falciparum prevalence of 126 (39.61 %) and 112 (35.44 %), respectively, and a non-significant difference (P>0.05) was observed between sex and P. falciparum infection. P. falciparum infected cases with anaemia recorded a high prevalence rates as compared to the non-infected cases. However, the multinomial logistic regression model demonstrated that P. falciparum was not a significant predictor to anaemia. In addition, the results of ELISA showed P. falciparum infected cases had higher specific antibody IgG responses of 64 (68.81 %) as compared to the negative P. falciparum samples, though a non-significant difference (P>0.05) between the negative and positive P. falciparum infected cases and the production of IgG antibody was observed (χ2=0.896, P =0.979). Determination of gene diversity revealed MAD20 and FC27 as the predominant allele for MSP1 and MSP2, respectively. However, K1 and FC27 were the predominant allele from asymptomatic children and on the other hand, FC27 and MAD20 were predominant for symptomatic cases. A high malaria transmission intensity as a result of mixed infection was observed in Minna with an overall multiplicity of infection (MOI) of 2.22. The MOI for symptomatic cases was lower 2.21 than what was observed from asymptomatic cases with 2.41. Finally, findings from this study revealed a high level of gene diversity within the antigenic markers of MSP1 and MSP2 (0.714 and 0.830, respectively). This study has demonstrated the potential of malarial antibody and gene diversity, as important markers for assessing differences in malaria parasite transmission intensity. Continuous genetic surveillance in P. falciparum will therefore serve as an important tool in monitoring changes in gene types and for intervention programmes effectiveness.