CHAPTER ONE

INTRODUCTION

1.1 BACKGROUND

Malaria is a mosquito-borne infectious disease affecting humans and other animals caused by parasitic single-celled microorganisms belonging to the Plasmodium species. The disease is known to be transmitted by an infected female Anopheles mosquito. The mosquito bite introduces the parasite from its saliva into the person’s blood. There are five species of the parasite P. falciparium. P. vivax, P. ovale, P. malariae and P. knowlesi.

Most deaths are caused by P. falciparium. P. vivax, P. ovale and P. malariae generally cause a milder form of malaria while P. knowlesi rarely causes disease in humans rather it causes diseases in long-tailed macaque [2] [1]. In 2016, 91 countries reported a total of 216 million cases of malaria, an increase of 5 million cases over the previous years. The global tally of malaria deaths reached 445,000 deaths, about the same number reported in 2015 [2].

Children under 5 years of age are one of the most vulnerable groups affected by malaria. In Africa, about 285 000 children died before their fifth birthdays in 2016, with 10 % of all deaths of children under the age of 5 years due to malaria which is equivalent to one child in sub-Saharan Africa dying of malaria every 2 min.

In high transmission areas, partial immunity to the disease is acquired during childhood. In such settings, the majority of malarial disease, and particularly severe disease with rapid progression to death, occurs in young children without acquired immunity. Severe anemia, hypoglycemia, and cerebral malaria are features of severe malaria more commonly seen in children than in adults [5].

According to the latest WHO data published in 2017 Malaria Deaths in Cameroon reached 9,161 or 4.14% of total deaths. The age-adjusted Death Rate is 29.11 per 100,000 population, which ranks Cameroon, number 30 in the world. Malaria is number 10 on the list of deaths in Cameroon [7].

The clinical manifestations of malaria, the severity, and the course of a clinical attack depend on the species and strain of the infecting plasmodium parasite. It also depends on the age, genetic constitution (ethnicity), immune status, malaria-specific immunity, nutritional status of the child, mode of transmission of infection, whether the individual was on prophylaxis or had previous exposure to antimalarial drugs, as the latter may present with only minimal symptoms or signs [6].

During the season of high malaria transmission, most children are infected by Plasmodium. As malaria parasites target red blood cells (RBCs), hematological changes are one of the most common complications and thus play a major role in the outcomes of the disease.

Several blood constituents, including RBCs, platelets, and leucocytes, are affected during malaria and serious anemia and thrombocytopenia are the most common complications in children with severe malaria in the rural areas [3].

Malaria infected patients tend to have significantly lower Platelets (PLT), Lymphocytes (LYM), Eosinophils (EOS), Red Blood Cells (RBCs), and Hemoglobin (HGB) levels, while monocyte and neutrophil counts go significantly higher in comparison to non-malaria infected patients.

Persons with platelet counts < 150,000/μL are 12-15 times more likely to have malaria infection than persons with platelet counts > 150,000/μL. Previous studies found that the ratio of monocytes to lymphocytes correlated with the risk of clinical malaria during follow-up [4].

Hematological alterations that are thought to characterize malaria are related to the overt biochemical changes that occur during the asexual stage of the life cycle of the malaria parasite.

Entry of P. falciparum into erythrocytes usually leads to a marked increase in the secretion of inflammatory cytokines (TNFα, IL-1, IL-10, and IFNγ), endothelial cell activation (due to overexpression of cell adhesion molecules: ICAM-1, VCAM-1), activation of the coagulation cascade (due to platelet consumption and endothelial damage), and sequestration of parasitized red blood cells (due to overexpression of cell adhesion molecules: pf EMP, and iNOS) [7].

These along with other mechanisms set in motion events, that ultimately result in morphological and numerical changes in the different blood cell lines such as red blood cells, leukocytes, and thrombocytes [8].

Haemolysis due to multiplication and metabolic activities of the Plasmodium within the red blood cells often results to anemia. Thrombocytopaenia and leukocytosis or leukopenia have been reported in malaria, but the extent of these alterations varies with the level of malaria parasitemia, endemicity, background hemoglobinopathy, nutritional status, demographic factors, and immunity to malaria [9].

Hematological changes are some of the most common complications in malaria and play a major role in malaria pathology. Knowledge on the changes that occur in the various hematological parameters in children suffering from malaria can improve on the diagnosis of malaria by increasing malaria suspicion and prompting a meticulous search for parasitemia using available diagnostic technologies.

Rationale

Malaria is the most common parasitic disease in many tropical countries especially sub-Saharan African countries. The most vulnerable population to this parasitic infection include children and pregnant women. Though presently available prevention and control tools have significantly reduced the morbidity, the diseases persist. Considerable hematological changes occur in malaria including mainly anemia and thrombocytopenia which may lead to complications and aggravation of the disease.

Data on the investigations of the hematological changes induced by malaria is scanty. Analyzing the hematological changes in malaria parasitemia in children in this specific sample area will generate data that could improve the clinical management of children affected by malaria.

1.2. Hypothesis

Malaria infection has a significant effect on hematological parameters in Cameroonian children.

1.3. Objectives

1.3.1 General Objective

This research seeks to determine the effects of malaria on hematological parameters in children in Yaoundé in order to contribute to improved clinical management of the patients.

1.3.2. Specific Objectives

1. To determine the malaria prevalence in children attending the Military hospital and University Teaching Hospital Yaounde.
2. To determine the changes posed by malaria parasitemia on the levels of hematological parameters.