TABLE OF CONTENTS
1.1. Situation analysis
1.3. Material and methods
2. EPIDEMIOLOGIC DETERMINANT
2.2. Epidemiologic triad
2.3. Clinical manifestations
3. MALARIA INCIDENCE
4. MALARIA AND ANAEMIA
4.1. Malaria and anaemia
4.2 Relative risk, Odds ratio, p-value
4.2.3 Control of confounding
1.1. Situation analysis
Malaria is an endemic disease in Zambia and it’s a major public health problem in Africa, especially in the Tropics and developing countries. Malaria continues to place an unacceptable burden on health and economic development in over 100 countries across the world, with malaria mortality exceeding one million annually, primarily in children under five(3).
Efforts have been put in place over the years to reduce the high incidence and mortality rate due to Malaria. From pharmaceutical options reviews to environmental actions, governments and their stakeholders through the Ministries of Health in various countries affected by the endemic, have worked to initiate policies for a massive and effective disease control.
According to WHO, about 109 countries in the world are considered endemic for malaria,45 countries within the African continent.3,3 billion people were estimated to be at risk of malaria in 2006.Of this total,2,1 billion were at low risk(<1 reported case per 1000 population),97% were living in regions other than Africa. The 1, 2 billion at high risk (≥1 case per 1000 population) were living mostly in the WHO African (49%) and South-East Asia regions (37%)(18).In the same report, there was an estimated death of 881,000(610,000-1,212,000) due to malaria in 2006, of which 91%were in Africa and 85% were of children under 5 years of age. (Table 1).
In Zambia, during a national malaria indicator survey, it was found that 22% of children below 5 years old of age had malaria. The highest malaria parasitemia were among children aged between 24-47 months. The distribution was higher in rural areas (28, 9%) than in urban areas (4, 9%). (9)
Table 1: Estimated of Malaria deaths by WHO region, 2006
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In this study, we would like to measure the magnitude of Malaria infection in line with the Fundamentals of Epidemiology. The objectives in this case control study is:
- To understand the epidemiological determinants of malaria associated with anaemia.
- To present and discuss epidemiologic elements in case control study
(Magnitude of anaemia in malaria cases).
- To present a data analysis of the available data collected.
- Analyze the effectiveness of prevention and control measures.
The study is conducted at Sichili Mission Hospital, a remote hospital situated in Sesheke district at 287km from Sichili mission hospital is a first level referral hospital in the district. With 68 beds capacity, it is the only hospital in an area of 17,000 square kilometers with estimated population of 36,412(2009).
The Hospital is organized into 5 major in-patients department, out patients departments and paramedical services. The Male ward admits all male surgical and medical conditions. The female ward admits all female surgical, medical and gynecologic cases. The maternity ward admits all ante partum and postpartum patients and neonatology. The paediatric ward admits all children with various conditions. The Isolation ward admits all patients with Tuberculosis and mental illness. The theatre is functioning 24hourly for emergency cases and twice in week for elective operations.
Paramedical services available are physiotherapy, laboratory, and pharmacy.
1.3. Material and methods:
A retrospective case control study is conducted for 1 year (from January 2009 to December 2009) at Sichili Mission Hospital. Data is aggregated from in-patients medical files, OPD registries, Maternity registries, Laboratory reports and hospital annual reports.
Cases are defined as all patients who presented at the hospital with presumptive malaria symptoms and developed anaemia. Malaria was confirmed by thick and thin films of finger prick blood smears (11).
The controls are defined as all patients with same variables like cases, who presented at the hospital with symptoms suggestive of other illnesses but screened deliberately for malaria parasitaemia and were fund negative but had anaemia.
Patients whose blood smear was not collected were not included even though they were admitted.
Patients referred from the Rural Health centers to the hospital were considered, yet data from the center itself was not analyzed. The RHC (Rural Health center) use RDT (Rapid Diagnostic Test) for rapid and easy way for malaria diagnosis.
2. EPIDEMIOLOGIC DETERMINANTS
Malaria is a protozoan disease caused by infection with parasites called ‘Plasmodium’’ and transmitted to man by certain species of infected female anopheline mosquito (14). Malaria is a major cause of mortality and morbidity in the tropics and sub-tropical regions. (13)
2.2. Epidemiologic triad: Figure 1
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2.2.1 Agent and Host
Four different species of Plasmodium parasite are responsible to cause malaria in humans: Plasmodium falciparum, Vivax, malariae and ovale.
In our region, plasmodium falciparum is mainly the cause of malaria morbidity and mortality. It’s the most dangerous and, if untreated, causes cerebral malaria and death (10). The malaria parasite undergo 2 cycles of development: the human cycle (asexual cycle) and the mosquito cycle (sexual cycle).
The plasmodium multiplies in the anopheline gut and comes into its saliva glands each time the mosquito feed new blood (sporozoites). At the human bite, the sporozoites are transmitted into man and migrate to the liver where they multiply and destroy liver cells. Some merozoites of the ovale and vivax species will remain dormant in the hepatocytes (Hypnozoites) and will be responsible of Relapses.(16) After 9 to 15 days, the merozoites will be released in the blood stream and will colonize the erythrocytes. Here they enlarge and get a “ring form” (Trophozoites).This stage is accompanied by an active metabolism including the ingestion of the host cytoplasm and proteolysis of the haemoglobin in amino-acids. Mature scizonts (merozoites) are released following the rupture of the infected erythrocyte. The invasion of other erythrocytes initiates another cycle.
As an alternative to the asexual explicative cycle, the parasite can differentiate into sexual forms known as macro- or microgametocytes. The gametocytes are large parasites which fill up the erythrocyte, but only contain one nucleus. Ingestion of gametocytes by the mosquito vector induces gametogenesis (i.e., the production of gametes) and escape from the host erythrocyte.
Factors which participate in the induction of gametogenesis include: a drop in temperature, an increase in carbon dioxide, and mosquito metabolites. Microgametes, formed by a process known as exflagellation, are flagellated forms which will fertilize the macrogamete leading to a zygote.
The zygote develops into a motile ookinete which penetrates the gut epithelial cells and develops into an oocyst. The oocyst undergoes multiple rounds of asexual replication resulting in the production of sporozoites. Rupture of the mature oocyst releases the sporozoites into the hemocoel (i.e., body cavity) of the mosquito. The sporozoites migrate to and invade the salivary glands, thus completing the life cycle.
In summary, malaria parasites undergo three distinct asexual replicative stages (exoerythrocytic schizogony, blood stage schizogony, and sporogony) resulting in the production of invasive forms (merozoites and sporozoites). A sexual reproduction occurs with the switch from vertebrate to invertebrate host and leads to the formation of the invasive ookinete. All invasive stages are characterized by the apical organelles typical of apicomplexan species. (7)
Malaria is widely spread in African regions, Asia and South America. The situation is worsened by multiple factors such as: poor or lack of health infrastructures to control
the disease, long distances of populations to health facilities, erratic drug supply and political conflicts in regions with high prevalence. Outbreaks have been reported even in zones where the disease was under control.
Malaria is caused by an anopheline mosquito. There are almost 300 species of mosquitos, among them only 60 or so can transmit the infection. Male anopheles does not transmit the plasmodium as they feed only on plants juices.
Like all other mosquitos, the anopheline breed in water and have different preferred breeding grounds, feeding options and resting place.
2.3. Clinical manifestations:
Clinical manifestations of malaria include:
-Fever: This is the main symptom. Fever is generated by the subsequent release of merozoites (paroxysm) in the blood stream. Its characteristics vary according to the plasmodium species. Between the paroxysm time, patient feels well and the temperature is normal. Travellers who have never been exposed to the plasmodium before are tending to develop severe forms of malaria. For this reason, it is important to consider malaria in any person with fever who visited some malaria endemic zones recently (17).
-Other symptoms include joints pains or general body malaise, vomiting, body weakness, anaemia, delirium, confusion or loss of consciousness depending on the severity of the disease, the host immune system and genetics (19).
Severe forms of malaria which include cerebral malaria, hypoglycaemia, pulmonary edema, anaemia, renal failure, DIC (Disseminated Intravascular Coagulation), cyanosis.
Mostly these complications may constitute other research topics.
In this retrospective case control study, we are looking at the occurrence of anaemia in patients with malaria.
According to WHO, the treatment of malaria requires more effort from governments to elaborate effective policies and implementation in the fight against the disease. Most of countries with high malaria incidence have tried not without success. The Zambian malaria initiative is one of the largest malaria control program which has proved tangible success in the region. In 2005, the National Malaria Control Program (NMCP) has set a goal of 75% reduction of malaria incidence and 20%reduction of under five mortality in 5 years through massive distribution of Insecticide Treated Nets (ITNs), Indoor residual spraying, Intermittent Preventive treatment of pregnant women using Sulphadoxine-Pyrimethamine,Use of Rapid Diagnostic Test and adopt Artemisinin-Based Combination as first line of malaria treatment. (12)