Description
CHAPTER ONE
INTRODUCTION
1.1 Background of the Study
Malaria is a disease caused by plasmodium species which is a parasitic organism that completes its life cycle in both human and the female Anopheles mosquito (the vector). There are five species known to infect man which are Plasmodium falciparum, P. vivax, P. ovale, P. malariae and P. knowlesi of which two causes severe cases of malaria (P. falciparum and P. vivax) (Ukaegbu et al., 2014). Malaria is a major cause of infant mortality and is the only insect borne parasite disease comparable in impact to the world’s killer transmissible diseases: diarrhea, acute respiratory infections, tuberculosis and AIDS (Curtis, 2006). Typhoid fever (enteric fever) on the other hand is a systemic prolonged feverish illness caused by certain Salmonella serotypes. Salmonella enteric serotype typhi (S.typhi) and Salmonella enteric serotype paratyphi (S. paratyphi A, S. paratyphi B, and S. paratyphi C) are the species that cause typhoid fever. S typhi is the most common serotype of Salmonella that causes typhoid fever (Pradhan, 2011). Poor disposal of human excreta, poorly equipped latrine with water facility, poor hand washing habit, and untreated water usage are the main cause of transmission of typhoid fever in developing countries (Malisa et al., 2010). However, an association between malaria and enteric fever was first described in the medical literature in the 19th century and was named typhomalarial fever by the United States Army (Uneke, 2008). The relationship by the two diseases has been substantiated by studies from Africa, India and elsewhere (Kanjilal et al., 2006).
Although malaria and typhoid are caused by very different and distinct organisms, a protozoan and a gram-negative bacillus and transmitted via different mechanisms, both diseases share rather similar symptoms. Thus it is very common to see patients undergoing both typhoid and malaria treatments even when their diagnosis has not been confirmed (Mbuh et al., 2003). Typhoid has been diagnosed most times in malaria confirmed patients or in individuals negative to malaria testing. The diagnosis of typhoid has however been controversial in terms of sensitivity and specificity, serological assays such as widal test are less than optimal but this form of diagnosis is the most readily and available test for typhoid diagnosis in rural settlements and areas with poor health infrastructure (Mogasale et al., 2016). Typhoid has an incident rate of twenty million annually and two hundred thousand deaths (200,000), describing the public health impact of these disease. It has been reported that misdiagnosis of typhoid fever for malaria is a common practice especially in areas of high malaria burden (Mongasale et al., 2016; Wong et al., 2016)
According to World Health Organization (WHO, 2015), infants and children (<5 years), pregnant women and patients with HIV/AIDS are at high risk of malaria infection, especially those living in Sub-Saharan Africa. It was estimated by WHO (2016) that 212 million cases of malaria and 429, 000 deaths was recorded globally in the year 2015 of which 90% of the malaria cases and 92% of the death cases were in Sub-Saharan Africa. Till date, malaria remains the leading cause of morbidity and mortality particularly in West Africa and Central Africa of which Nigeria ranks as the most affected with an estimated prevalence burden of about 30% of all global infections in 2015 (WHO, 2015). The tropical situation of the country and the suitability of the hot climate to breeding of the parasite definitive host (the female Anopheles mosquito), promotes the continuous and endemic transmission of the parasite in Nigerian population. However, over-diagnosis of malaria and misdiagnosis of other aetiologies of other illness as malaria has been on the increase in recent decade. Due to the endemic nature of malaria in the country, some healthcare providers in the poor resourced settings of the country generalize other illness as malaria and proceed to treatment with anti-malarial drugs without proper diagnosis (Ukaegbu et al., 2014). The effects of such actions are not far-reaching (drug resistance and changes in population structure of the parasite). Understanding its prevalence and the serotypes responsible will help in proper diagnosis of the disease, and adequate monitoring of antimicrobial resistance in circulating serotypes identified in the study population as well as phylogenetic relatedness across isolates.
According to WHO (2017) Malaria transmission occurs in five WHO regions. Globally, an estimated 3.2 billion people in 95 countries and territories are at risk of being infected with malaria and 1.2 billion are at high risk (> 1 in 1000 chance of getting malaria in a year). According to the World Malaria Report (2015), there were 214 million cases of malaria globally in 2015 (uncertainty range from 149-303 million) and 438 000 malaria deaths (range 236 000 to 635 000), representing a decrease in malaria cases and deaths of 37% and 60% respectively since 2000. The burden was heaviest in the WHO African Region, where an estimated 90% of all malaria deaths occurred, and in children aged under 5 years, who accounted for more than two third of all deaths. The World Malaria Report (2016) showed that the rate of new malaria cases fell by 21% globally between 2010 and 2015. Malaria death rates fell by 29% in the same 5 year period. In Sub-Saharan Africa, case incidence and death rates fell by 21% and 31% respectively. Other regions have made substantial gains in their malaria responses, but the disease remains a major public health threat. In 2015, the global tally of malaria reached 429 000 malaria deaths and 212 million new cases. One child died from malaria every 2 minutes (WHO, 2017).
In 2015, WHO estimated that 7 of the 43 countries in sub-Saharan Africa with malaria transmission had more than 25% of their population infected with malaria parasites (Burkina Faso, Cameroon, Equatorial Guinea, Guinea, Mali, Sierra Leone and Togo); this number has decreased from 12 countries in 2010 (WHO, 2016).
In 2015, WHO reported that Nigeria had 76% of its population being infected with malaria. The prevalent circulating parasite is plasmodium falciparum which is transmitted by 6 anopheles species (An. gambiae, An. arbiensis, An. moucheti, An. melas and An. nili). The prevalence of P. falciparum in Nigeria is reported to be high in Kaduna, Kano, Kebbi, Cross River, Akwa- Ibom, Kwara and Niger (WHO, 2017).
Co-infection of Malaria and Typhoid fever
Malaria and typhoid are the most endemic diseases in the tropics. However, malaria remains the most overwhelming health problem facing humanity in the vast majority of the tropical and subtropical regions, with 300 to 500 million cases and up to 3 million deaths annually (WHO, 2000). About 90% of all malaria deaths in the world today occur in the Sub-Saharan Africa mostly as a result of majority of infection being caused by most dangerous species of parasite, P. falciparum: accounting for an estimated 1.4 to 2.6 million deaths per year in the region (WHO, 2006; Clara, 2010).
In the last two decades, the relationship and co-existent prevalence of typhoid and malaria diseases have been substantiated by studies from Africa and Asia (Ohanu et al., 2003; Sur et al., 2006; Kanjilal et al., 2006). The prevalence of malaria and typhoid co-infection using Widal test ranged from 4.4% to 70% (Tanyigna et al., 2001; Ibadin and Ogbimi, 2004), on the other hand the prevalence of concurrent malaria and typhoid fever using cultural technique alone ranged from 11.1% to 26.6% (Smith et al., 2004; Khan et al., 2005; Akinyemi et al., 2007). Mbuh and others (2003) also observed that the two studies that used both techniques reported higher rates of co-infection compared with that using bacteriological culture technique. Nwuzo et al., (2009) analyzed 250 blood samples from symptomatic subjects for malaria parasite and typhoid fever using parasitological strip, Widal screening and bacteriological cultural techniques, respectively. The result showed that 33 (13.2%) samples were positive for malaria parasite, 53 (21.2%) were positive for typhoid fever by the Widal test and 2 (0.8%) were positive by culture method. Fourteen patients (5.6%) had co-infection which was significantly high when diagnosed by Widal test than by cultural method (0.8%) (Clara, 2010).
In a research carried out by Florence et al., (2004). Sixty samples were positive for malaria parasites, 22 of which were positive for typhoid by the Widal test and only one by the culture method. The rate of co-infection was significantly high when typhoid was diagnosed by Widal (10.1%) than by blood culture method (0.5%). The correlation analysis showed no specific relationship between malaria parasite load and the level of Salmonella antibody titre in malaria patients. Florence et al., (2004) noted that the incidence of typhoid and malaria co-infection will greatly reduce if the diagnosis of typhoid fever in malaria endemic areas is based on blood culture (Clara, 2010).
1.2 Statement of the Problem
Malaria and typhoid fever are well known undifferentiated feverish illnesses which may be responsible for varying degrees of morbidity and mortality in developing countries, Nigeria inclusive. Due to inadequate availability of diagnostics in developing countries, most cases of severe feverish illnesses are diagnosed as malaria (Stoler & Awandare, 2016). In 2015, out of 182, 200,000 million cases in Nigeria, 76% of the population had high transmission of malaria, 24% of the population had low transmission with no free malaria cases (WHO, 2017). Also, the prevalence of typhoid fever in Nigeria ranges from 0.071% to 47% (Akinyemi et al., 2005). Predisposition to co-infection is usually influenced by their similar epidemiological factors such as dense population, poor hygiene and sanitation practices (Iheukwumere et al., 2013; Sharma et al., 2016). Due to their similar clinical presentations and the likelihood of a misdiagnosis and mistreatment of feverish patients, it has been suggested that malaria and typhoid should be treated simultaneously in endemic communities (Uneke, 2008; Iheukwumere et al., 2013). However, concurrent treatment may have some public hazards in the sense that, indiscriminate use of antibiotics or anti-malarial may result in increasing surge of drug resistance, unnecessary expenditure and exposure of patients to side effects of antibiotics (Sharma et al., 2016).
Patients presenting feverish symptoms reporting to the laboratory section of the Nasarawa state University keffi clinic are usually tested for malaria using malaria Rapid Diagnostic Test (mRDT) and subsequently treated separately or concomitantly without further investigation of other possible causes. This method of diagnosis usually lack sensitivity at low levels of parasitaemia. Meanwhile reliable diagnosis is by microscopic examination of blood film. The diagnosis of typhoid fever on clinical grounds is difficult, as the presenting symptoms are diverse and similar to those observed with other common feverish illnesses (Stuart et al., 1996). The isolation of serotype Typhi from blood remains the method of choice for the laboratory diagnosis (Wain et al., 1998). However, the availability of microbiological culturing facilities is often limited in regions in which typhoid is endemic (such as the study area for this research work), and blood cultures can be negative when patients have received prior antibiotic therapy. Bone marrow culturing has a higher sensitivity than blood culturing but is a more invasive procedure (Farooqui et al., 1991; Koeleman et al., 1992). It is therefore advisable to perform both tests on individuals presenting with fever of malaria-typhoid signs and symptoms using accurate diagnostic methods to ascertain true co-infection followed by appropriate treatment (Mbuh et al., 2003).
This research work therefore seeks to use malaria Rapid Diagnostic Test (mRDT), Widal Serology Test, blood culture (for Salmonella species) and Enzyme-linked immunosorbent assay (ELISA) technique to compare their reliability and accuracy.
1.3 Justification of the Study
Malaria and typhoid are common causes of illness globally but more endemic in Africa and Asia. Diagnosing patients based on clinical signs and symptoms is difficult to differentiate between malaria and typhoid fever (Moses et al., 2016).
The global burden of malaria cases is about 207 million annually resulting in 627, 000 deaths (WHO, 2013), with sub-Saharan Africa being the most affected region. According to WHO malaria report (2014), there were about 197 million malaria cases worldwide and an estimated 584 000 deaths, mostly African children. In Nigeria, malaria still remains a major health challenge with about two-third of the population living in malaria endemic areas (WHO, 2015). Each year, typhoid fever causes an estimated 21.7 million illness and 217 000 fatalities globally (Marks et al., 2017). A key limitation to improving the control of typhoid fever is the lack of reliable diagnostic tests (Baker, et al., 2010). In addition to confirming infection in individuals, accurate laboratory diagnostics are needed to ascertain true disease burden, and to improve understanding of the natural history of infection in humans. Diagnostic approaches for typhoid infection are broadly aimed either at directly detecting bacteria or bacterial products or measuring the host response in clinical samples (Darton, et al., 2014).
Diagnosis is done by Widal and culture methods, however, isolation of the etiological agent, the Salmonella enteric (serovar typhi) from bone marrow culture is the ideal gold standard (Parry et al., 2011). Given the poor accuracy of currently available diagnostic tests, attempt have been made to carry out diagnosis using serology tool such as Enzyme-linked immunosorbent assay (ELISA) to ascertain its reliability and accuracy. Although malaria and typhoid fever is endemic in Nigeria, in Nasarawa state, there are fewer data on the diseases with respect to the serology aspect of diagnosis.
1.4 Aim of the Study
The aim of the study is to evaluate the prevalence of co-infection of malaria and typhoid fever among patients attending Nasarawa State University clinic Keffi, using serology.
1.5 Objectives of the study
The specific objectives of this study were:
- To determine the prevalence of malaria and typhoid in patients attending Nasarawa State University Keffi clinic using malaria Rapid Diagnostic Test (mRDT), Widal test and blood culture.
- To determine the infection rate in relation to demographic factors of patients attending Nasarawa State University Keffi clinic.
- To identify plasmodium species causing malaria in the study area using Enzyme-linked immunosorbent assay (ELISA).
- To identify Salmonella species causing typhoid fever in the study area using Enzyme-linked immunosorbent assay (ELISA)
1.6 Scope of the Study
This study was carried out in Keffi Local Government Araea of Nasarawa State among patients attending Nasarawa State University Keffi clinic between the months of May and July, 2019. Nasarawa State University Keffi clinic was established in the year 2009 primarily to cater for the health challenges of students and staff of the institution. But because of the significantly available equipment at the clinic, it does not only serve the university students and staff alone, it also service the health needs of Keffi residents as a whole. This was what informed the choice of the clinic for this study. Nigeria suffers the world’s greatest malaria burden with approximately 51 million cases and 207, 000 deaths reported annually (approximately 30% of the total malaria burden in Africa), while 97% of the total population (approximately 173 million) is at risk of infection (WHO, 2014). In Nigeria, typhoid fever prevalence rates were put at 42% in Owerri (Opara et al., 2011); 80.1% in Abeokuta among patients with febrile illness (Okonko et al., 2010) and 81.5% in Minna (Abu et al., 2012; Festus, 2014).
The purpose of the study is to determine the prevalence of malaria and typhoid fever among the population in the study area using demographic factors and testing methods as indices. The study covers patients who upon consultation with a Doctor on duty and were referred to the laboratory section to carried out either malaria or typhoid test or malaria and typhoid test were considered for the study. The study populations were patient ≥ 2years who show sign and symptoms of malaria and typhoid fever. The study was limited by unwillingness to give informed consent by patient, inability to collect whole blood samples from participatory patients and presence of other infection.
1.7 Definition of Operational Terms and Acronyms
BA – Blood Agar
CA – Chocolate Agar
EDTA – Ethylene Diamine Tetra Acetic Acid
ELISA – Enzyme-Linked Immunosorbent Assay
HRP-2 – Histidine Rich Protein
LDH- Limit of Detection
MAC – MacConkey Agar
RBCs – Red Blood Cells
RDT – Rapid Diagnostic Test
PCR – Polymerase Chain Reaction
WHO – World Health Organization
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