CHAPTER ONE
Introduction
Background to the Study
Historical record has it that tuberculosis otherwise known as phthsis or consumption disease has been the affliction of man since ancient times. It is reported to have occurred in Egypt in about 3000BC. It was not clearly understood until Robert Koch in 1882 first described the disease and the causative agent. Tuberculosis is an acute or chronic necrotizing disease caused by the mycobacterium tuberculosis and characterized pathologically by inflammatory changes, caseation, tubercle formation and fibrosis. It is a communicable disease transmitted mainly by droplets from an infectious person to another person (Lyght, 1971).
The disease initially was limited many centuries to Europe, America, and Asia and North Eastern part of Africa. However, activities of explorers, adventurers and traders led to the extension of the disease to West Africa by the 1900. Since then it has remained a major public health problem in many tropical countries including Nigeria (Weathral, 2004). Though it can affect any organ, the one most commonly encountered in clinical practice is the pulmonary type which affects the lungs and it is very important in the epidemiology of the infection.
Tuberculosis (TB) has remained one of the world’s major causes of illness and death, and in 1993, the World Health Organization (WHO) declared TB to be a global health emergency. One third of the world’s population or two billion people carry the TB bacteria, more than 9 million of whom become sick each year with “active” TB which can spread to other; “latent TB” disease cannot be spread (WHO, 2006).
The World Health Organization disclosed that tuberculosis disproportionately affects people in resource poor settings particularly, those in Asia and Africa. More than 90 per cent of new tuberculosis cases and deaths occur in developing countries posing significant challenges to the livelihood of individuals and developing economies as tuberculosis primarily affects people during their most productive years 15-59 years (WHO, 2OO7). The United State Agency for International Development USAID (2009) stated that twenty two countries are considered “high burden countries (HBCs).” These countries account for approximately 80 per cent of new tuberculosis cases each year. Most high burden countries are in Africa and Asia. India, China, Indonesia, South Africa and Nigeria have the highest number of new tuberculosis cases in the world (USAID, 2OO9).
Kaiser (2007) disclosed that an estimated 13.7 million people were living with “active” tuberculosis, including 9.3 million new cases. There were an estimated 1.8 million tuberculosis deaths, one in four which was HIV-related twice as many as previously recognized. In Nigeria, the incidence rate of tuberculosis is 123 per 100,000, prevalence rate of 536 per 100,000 and mortality rate of 76 per 100,000 (Haruna, 2008). Within the context of this study, tuberculosis refers to a contagious mycobacterial respiratory disease that is transmitted from one infected person to another person through infected droplets during coughing, and sneezing. Usually, the disease can affect any organ giving rise to extra-pulmonary tuberculosis (ETB), but involvement of the lungs account for more than eighty per cent of tuberculosis cases. TB affecting the lungs is called pulmonary tuberculosis (PTB). The lungs are organs of respiration found in the thoracic cavity.
Lucas and Gilles (2003) outlined three stages of the clinical manifestation or signs and symptoms of tuberculosis in man; the primary complex, which consists of a small parenchymal lesion and involvement of lymph nodes in the lungs, this constitutes the classical Ghon focus. In most cases the primary complex heals spontaneously with fibrosis and calcification of the lesions, but the organism may persist for many years within the focus. A person develops this primary complex only when infected for the first time.
Early complication is the second stage, which occurs when the primary complex progresses to produce more severe manifestation locally or there may be spread to other parts of the body. The first 6 months of the infection is the most dangerous as there may be haematogenous spread to either, the bones and joints or disseminated in the form of miliary tuberculosis.
The third stage occurs when there is reactivation of existing lesion or by exogenous re-infection. It involves the destruction of the lung parenchyma with fibrosis and cavitations. It is at this stage that pulmonary tuberculosis is clinically established and it may present with cough, haemoptysis and chest pains. Other symptoms are fever, loss of weight and malaise. The frequency and vigour of cough and the ventilation of the environment influence transmission of infection (Park, 2007). Left untreated a person with active Tuberculosis will infect an average of 10-15 people every year (Haruna, 2008).The statistics for incidence of tuberculosis for different countries have been estimated as follows: Vietnam: 148,000, Bangladash; 332,000; China; 1,365,000, India; 1,856000, Russia; 193,000, South Africa; 228,000, United States; 18,361, Brazil; 116,000 (Centre for Disease control, 2010). Even though the cause of tuberculosis in man is a bacterium known as mycobacterium tuberculosis transmitted mainly by airborne droplets, certain contributory factors seem to play a major role for its prevalence in human population.
Infection with human immunodeficiency virus (HIV) is one of the most important risk factor for development of tuberculosis in persons infected with M-tuberculosis (Lienhardt, 2001). Due to immune suppression caused by HIV infection, persons with latent tuberculosis as well as newly infected persons may progress rapidly to clinical disease. Complication of TB in HIV infected people include increase frequency of side effects of drugs treatments and increase rates of relapse and re-infection. The estimated risk of clinical disease in HIV – infected persons is between 6 and 26 times the risk in non HIV infected persons (Ravigoline and Diye, 1992). By mid-1992, Ravigoline and Diye, stated that an estimated 5.6 million persons were dually infected with HIV and M. tuberculosis world wide; 3.8 million of them in sub-Saharan Africa. WHO (2010) disclosed that the TB burden in Nigeria is compounded by a high prevalence of HIV which stands at 4.1 per cent in general population. It further stated that the prevalence of HIV among TB patients increased from 2.2 per cent in 1991 to 19.1 per cent in 2001 and 25 per cent in 2010. This indicates that the TB situation in the country is HIV driven. Other factors associated with tuberculosis are, age and sex, lack of access to health care, crowding, urbanization and homelessness, migration, socioeconomic status (SES), race/ethnicity, and level of education.
The extent to which differences in reported cases of TB between men and women reflects differences in prevalence or differences in access remains uncertain, but there is evidence that gender influences access to health care and therefore higher propensity for diagnosis. Bennstam (2004) stated that perceptions of TB are affected by gender norms and stereotypes. He stressed that the social and economic impact of being diagnosed with TB can differ for women and men of different ages and positions affecting their vulnerability to effects of ill-health. Differences in anticipated impact of TB may translate into differences between men and women in seeking care and therefore for vulnerability to severe disease. Gender distribution studies in India has shown that more males were screened compare to females, but there was no difference in the prevalence positivity rate between male and female patients (Shamila, Andrabi & Imtiyaz, 2012).
Women and men often face different barriers to accessing care. With passive case finding as is usual with directly observed treatment short course (DOTS), a low proportion of women with TB are found, in contrast to active case finding where roughly equal numbers of men and women with TB are detected (Uplekar, 2001). The factors which bring about this differential access have included self-image, status, access to resources, manifestation and expression of symptoms and stigma of having TB. Once detected with TB, women are more likely to be adherent to therapy and be cured of TB than men.
Men postpone care seeking longer than women. Reasons for longer delay among males includes fear of individual costs of diagnosis, and treatment as documented in studies, in India and Nigeria (Enwuru, 2002). He further stated that men are more likely to neglect symptoms longer until serious before going to the hospital. Women, on the other hand are more likely than men to seek care immediately after symptoms. Studies in India and China however, have shown that women tend to self medicate or choose private practitioners as the first point of contact after deciding to seek care (Lonnroth, 1999).
Another significant gender difference have been documented in Sudan and Nepal in which women are offered sputum test less frequently than men (Godfrey, 2002). This according to him is due to the fact that in some communities, women need to be accompanied to DOTS clinic hence longer female delay. Ahsan (2004) reported that women bear the highest burden of stigmatizing behaviours. In some communities, female TB patients and women who are suspected to have active TB are likely to be force to get divorced, send back to their parents home and have fewer chances of getting married. In Bangladesh and Vietnam, studies have shown that fear of isolation from family or community is a key factor contributing to delay among women. Stigma is suspected to be a contributing cause as to why females are more likely to postpone diagnosis, are offered sputum test less frequently and felt more inhibited than men to discuss TB with their family (Barhoom and Driannase, 1991).
Age and sex, variations in the prevalence of tuberculosis infection and disease have been reported world wide. Shamila et al (2012) documented highest prevalence of sputum positivity 26.4 per cent among cough symptomatic in the age group 55years and above, followed by 15-24 years 24.5 per cent and 25-35years age group 24.0 per cent. Early tuberculin skin test surveys have shown that infection with M. tuberculosis increase with age and then declines in older adults (Lienhardt, 2001). In children, less than 5 years of age, the risks of progressive tuberculosis disease after primary infection has been shown to be high, probably reflecting a high dose challenge within the home environment (contacts of smear-positive tuberculosis cases). The risk then decreases until age 12 years and rises again in young adults. Most Tuberculosis in adults arises many years after primary infection because of exogenous re-infection or reactivation of a latent focus of infection. It is probable that in addition to genuine age and sex differences in susceptibility related to biologic mechanisms, socio-economic and cultural factors may play a role in determining age and sex differences in rates of infection, progression to disease and treatment outcome (Vidal, Malo & Vogan, 1993). In Nigeria, the age group commonly affected by TB are the most productive age groups with 25-34 age group accounting for (33.6%), 15,303 of the smear positive cases registered in 2010 (WHO, 2010).
Although TB principally affects people in the economically active age group (15-59yrs), it is also an important cause of mortality in children. Regarding the sex specific prevalence of pulmonary tuberculosis, Hussen, Ahmed, Abihu, Solomon and Solomon (2012) reported that out of total cases examined for acid fast bacilli (AFB) between 2005/06-2009/10 in Agaro, Ethiopia 22.3% of males and 17.3% of the females were smear positive for AFB, but there was no statistically significant difference between sex or gender and pulmonary tuberculosis. It is believed that the incidence of childhood TB is underestimated by half or more in official figures (Dye, 2001). Children with TB are neglected by health services, which concentrated on adults. Studies have revealed over the years that young children equally face the highest risk of developing disease after infection with Mycobacterium Tuberculosis. Age plays a further role because older people are more likely to have been infected with TB during their youthful years and are therefore vulnerable to reactivation (active disease) with the natural physiological decline of the immune system in advanced age. TB prevention and control programmes which do not address these vulnerable groups will at best leave a reservoir from which new sputum smear positive cases will emerge in the future.
Crowding, urbanization and homelessness is associated with the risk of tuberculin conversion in children living in the house of an infectious tuberculosis case and number of cubic feet per person in the house (Hopewell, 1992). This finding suggests that in crowded houses, a greater degree of shared air space increase exposure to M. tuberculosis, which can be limited by air movement in close spaces, hence a greater risk of infection. The progression to disease might be enhanced by other factors modifying host’s immune defenses such as malnutrition, depressed immune status or HIV infection (Davies, 1994).
Association between tuberculosis and urbanization is probably confounded by poverty and crowding, because residential crowding in low socioeconomic groups brings more persons (especially children) into contact with infectious cases of tuberculosis in people living in the same house hold (Kruger, Woodaw Diehr, 1990). In New York City, US, and South Africa, the resurgence of tuberculosis since the early 1980s has been attributed to high rates of tuberculosis in alcoholics, drug users, and homeless people. The development of mass shelters for homeless population exacerbated transmission of tuberculosis, because persons whose tuberculosis was treated inadequately were gathered together in crowded shelters with highly susceptible persons, including HIV-infected subjects (Brudney and Dopkin, 1991).
Tuberculosis has been linked with poverty. It is associated with vulnerability to severe disease and death due to TB, especially through its effect on access to health care. Evidence is accumulating to suggest that the poor have greater difficulty in overcoming barriers in accessing care and completing treatment than the less poor because they have fewer resources to use for direct costs, such as transport to health facilities and consulting fees (Lonnroth, 1999). He further stated that delays in seeking treatment are longer amongst poor patients with a chronic cough especially for poor female or aged people. Upleker (2001) posited that poverty is associated with low concordance with treatment and therefore poor treatment outcomes. People constrained by the conditions of poverty who suffer from TB are more likely to default, especially between diagnosis, registration and completion of treatment. Poverty conditions during the industrial revolution in the 19th century in Europe were accompanied by disease and death due to tuberculosis (Comstock, 1982).
Disease rates declined constantly between the early 19th century (when approximately one death in four was caused by tuberculosis) and the mid 1980s (Rowland & Bell, 1996). This decline started long before effective chemotherapy or vaccines were available. It has been attributed to the combined effects of isolation of infectious Tuberculosis patients in sanitariums as well as socio-economic development. A study on socio-economic status and infections among high school students in Maryland in 1963, showed that children from homes that ranked higher with respect to the educational level of the head of house hold, lack of crowding, and adequacy of housing had lower rates of tuberculin reactions (Aoki, Shimao, & Mori, 1985). In a similar study in Srinagar India, sputum positivity rate was higher in illiterates compared to literates and highest among those in the lower socio-economic class compared to those in the upper class Shamila et al (2012). Ogboi, Idris, Olayinka and Illyas (2010) documented high sputum smear-positive cases of TB among subjects with no formal education in Zaria, Nigeria compared to those with higher level of education. The risk of disease in persons in Europe and America has also been associated with socio-economic status. Other risk factors include effect of race/ethnicity on infection and disease and genetics and the environment (Toque, Doherty & Bellis 1998). Tuberculosis at the early stage may present no symptom to the sufferer making it impossible for the individual to identify the on set of the disease.
Weathral (2004) explained that with progression in the infectious disease, the following signs and symptoms are notice; fatigue, unexplained loss of weight, anorexia, sweating at night which may assume drenching proportions and fever. As the disease progresses cough becomes very severe and tuberculosis patients may become exhausted by the almost continuous but ineffectual attempt to clear the respiratory system, haemoptysis, pain and dyspnoea when the lesion is close to the pleura and involves it. In order to arrived at the correct diagnosis, adequate investigation has to be made to rule out other conditions which often mimic signs and symptoms similar to tuberculosis. Few of such conditions are pneumonia, bronchietasis, lung abscess, lung cancer and asthma. In a developing country like Nigeria, anyone manifesting such symptoms should be suspected of having tuberculosis. Park (2008) opined that diagnosis of tuberculosis is as laid down in the World Health Organization (WHO) protocol, which is direct sputum smear. Nigeria currently adopts this method for case finding activities. A case as defined by WHO is someone whose sputum is positive for tubercle bacilli. All other sufferers from tuberculosis whose sputum is negative, but show suggestive shadows in chest X-ray are reckoned as “suspects”.
The Federal Ministry of Health (2004) through its co-ordinating unit, the National Tuberculosis and Leprosy Control Programme (NTBLCP) has a standard treatment protocol for the management of confirmed cases. The treatment is basically chemotherapeutic and consists of a combination of regimen to be administered using Directly Observe Treatment Short course (DOTS). DOTS strategies emphasize the supervision of patients taking their drugs directly by health care workers. The drugs currently being used in Nigeria are Rifampicin, Isoniazid, ethambutol, Pyrazinamide, Streptomycin and Thiazetazone. This regimen when strictly adhere to render those with confirmed cases of TB non-infectious within two weeks hence preventing further transmission. It therefore means that they no longer serve as a potential source of infection in the community. When there is no further source of infection, there won’t be incidence of Tuberculosis infection in the community.
Lucas and Gilles (2007) explained that incidence is suitable in describing the pattern of sickness in the community which falls under morbidity statistic. Specifically they defined incidence rate as the frequency of occurrence of new cases or spells of illness. Park (2007) defined incidence as the number of new cases of a particular disease condition occurring in a defined population during a specified period of time. He further stated that incidence measures the rate at which new cases are occurring in a population and that it is not influenced by the duration of the disease. Watt and Hosseini (2007) stated that the incidence of tuberculosis is the estimated number of new tuberculosis cases arising in one year per 100,000 populations including all forms of Tuberculosis.
The use of incidence rate is generally restricted to acute conditions. It’s usefulness as a health status indicator is for taking action to control disease and for research into the causes and pathogenesis, distribution of diseases and efficacy of preventive and therapeutic measures (Park, 2009). Similarly, Onwasigwe (2010) stated that incidence measures the probability that healthy people will develop disease or health related event during a specified period of time. It indicates the rate at which new cases of the disease occur in a defined, previously disease free population. She further asserted that incidence can be determined by following a group of people and finding the rate at which new cases of a disease appear. Before this can be done, the individuals are grouped according to their health status, the infected and the non infected. This information may be obtained after conducting a suitable screening test or from the available health records. It is necessary to determine the date of onset of the disease if possible, or the earliest sign of recognition of the problem. For chronic diseases like Tuberculosis, the date of definite diagnosis is taken as the date of on set of the disease. Incidence is of two types: incidence risk and incidence rate.
Evans (1997) identified two measures of incidence: incidence risk and incidence rate. The incidence risk is also known as the cumulative incidence. It provides an estimate of the probability that a person will develop a disease during a specified period. Incidence rate is also known as the force of morbidity or incidence density. It measures the number of cases of a particular disease within a specified period. The incidence rate is likely to be a more accurate measure of disease incidence than the incidence risk because it takes into account the fact that in most studies, not everyone is followed-up for all of the time. For this study, incidence will be considered as the new cases of tuberculosis in a specified population in a given period of time. Of the two types, incidence rate will be used to measure incidence of Tuberculosis. Rate is the number of cases of a disease multiplied by one thousand, and divided by the population at risk. Chronic diseases like tuberculosis usually have prevalence because of its long duration.
The term “disease prevalence” refers to all current cases (old and new) existing in a given population. Broadly defined, prevalence rate is the total number of all individuals who have an attribute or disease at a particular time (or during a particular period) divided by the population at risk of having the attribute or disease at this point in time or mid-way through the period (Parks, 2009). Prevalence is of two types used by investigators, point prevalence and period prevalence. Point prevalence refers to the number of cases present at a specified moment of time. Period prevalence refers to the number of cases that occur during a specified period of time – for example, a year. Period prevalence consists of the – point prevalence at the beginning of a specified period of time plus all new cases that occur during that period (Lilienfeld, 1976). Period prevalence will be a more appropriate measure for this study as it aims to investigate the prevalence of tuberculosis from 2002-2011 in all approved DOTS centres in Central Senatorial District of Plateau state. In this study, incidence will be regarded as new cases of Tuberculosis from 2002-2011, while prevalence is the number of cases of Tuberculosis for this period of twelve years and duration of the disease.
Incidence and prevalence can be determined using the rate. Rate is the number of times something happens or number of examples of something or event within a certain period. In relation to disease condition, it means the number of time a particular disease occurs in a given population.
Incidence is measured against the number of people at risk because the individuals exposed to the disease are the ones likely to develop such disease which makes up the new cases while prevalence is concerned with the population. This is because both new and old cases of the disease are considered and it is assumed that the population is stable, and incidence and duration of diseases are changing. The difference between prevalence and incidence is that knowledge of time of onset of disease is not required in prevalence study. However it is necessary to determine the date of on set for studies of incidence. In view of its preponderance to chronicity, high infectivity, and social consequences, prevention holds the key to curbing the spread of tuberculosis in developing countries including Nigeria.
Hornby (2005) defined prevention as the act of stopping something bad from happening (like accidents, crime and prevention of disease). Prevention of disease can be defined as all actions to reduced or eliminate the onset, causes, complications or recurrence of a disease. For certain diseases like Tuberculosis that have a preponderance to chronicity, high infectivity and serious consequences, prevention remains a useful tool to stop its transmission in human population. Some activities that can be adopted to prevent tuberculosis includes; education, immunization, personal hygiene, environmental hygiene, specific prophylaxis, early diagnosis and treatment to prevent further damage to the individual and in cases of infectious disease to prevent its spread to the community. Its basic method is screening of high risk groups, (Lucas and Gilles, 2003).
Prevention of tuberculosis is the act of averting the occurrence of the disease in human population. This can be achieved in various ways depending on the available resources. For effective preventive measures to be adopted, the population in which such activities are to be targeted should be well defined. There are about four groups of persons that can benefit from properly planned tuberculosis prevention and control activities. The first groups are those who had no previous exposure to tubercle bacilli; that is they are not infected with tuberculosis: this group requires intervention in the area of health promotion with emphasis on inculcation of better personal health habits with regard to spitting and coughing, eating of healthy diets to boost ones immunity. Overcrowding should be avoided and adequate ventilation should be provided in individual houses. This will reduce the chances of contracting tuberculosis since it is an airborne infection. Vaccination with BCG particularly children at birth is another useful tool with proven efficacy.
The second group are those who have been infected but do not manifest the signs and symptoms of tuberculosis, but must be protected from reactivation of the disease and re-infection: This category normally benefits from the services given to the first group except that instead of specific protection with BCG in form of vaccination, they are administered prophylactic drug such as isoniaziad.
The third group are those diagnosed with active disease which must have effective treatment and remain under supervision until they have recovered fully. This group should be supported by the family. Patients should ensure adherence to treatment schedule until they are fully cured. Health workers therefore, have a responsibility to supervise treatment compliance and to give priority to tuberculosis patients. By properly treating those diagnosed, with Tuberculosis, the chain of transmission is being interrupted as there will be no source of further infection.
The fourth group, are those with undiagnosed active disease without treatment, the disease may progress with further irreversible damage. As a potential source of infection, they constitute a danger to the community. The best way to prevent TB transmission is to detect TB suspects early as possible and ensure treatment completion. Adherence to the treatment is critical as the number of TB bacilli is significantly reduced within two weeks of beginning treatment (Hope Well, 1986). They need proper awareness to appreciate the fact that they should seek for treatment. Community members could arrange for the transportation of TB suspects to the hospital.