Tuberculosis in Children in Developed Countries

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Jill Hanley

Introduction


Tuberculosis is a disease caused by infection of the body by bacteria from the family Mycobacteria. The bacteria settle in the lungs, but can move through the blood to other parts of the body such as the kidneys, the spine, and the brain. Infection occurs upon ingesting airborne bacteria expelled by an infected person and entry of the bacteria into the lungs [3]. TB bacteria can stay in the air for several hours [4]. The TB bacteria in the lungs can multiply and erode the tissue, causing cavitary lesions that are difficult for TB drugs to penetrate [16]. TB can be fatal, especially if it goes untreated or if it develops resistance to drugs [3]. 1/3 of the global population has some form of TB infection [3]. There is a distinction between latent TB infection and active TB disease. Latent TB infection occurs when the bacteria enter the lungs but are prevented from growing by the immune system; people with latent TB infection do not show symptoms and cannot infect others. TB disease occurs when the infection becomes active, or when the bacteria begin to grow in the lungs. Someone with active pulmonary TB is highly contagious. If left untreated, latent TB infection may eventually progress to TB disease; untreated TB disease may cause death in the sufferer as well as an increased risk of infection to others [5]. 9 million new cases of TB are expected to surface every year worldwide [2].

Between 2000 and 2020, it is estimated that 1 billion people will be infected with TB bacteria, 200 million will develop TB disease, and 35 million will die from the disease [10, pg 624]. In developed countries such as the US and the UK, TB treatment is available through the public health system and through private physicians. However, TB is a global issue, and its spread is serious and cannot always be contained, even in these developed countries with sound treatment technology. It is important that health care officials do not stop trying to control the spread of TB even in developed countries. The rise in TB cases in the 1980s and 1990s has been attributed by the CDC to the failed efforts of health care officials to keep the infection under control [5].

One of the most important aspects of TB as a global issue is its transmission to and infection in children. Family members with TB can easily spread TB to their children; the special attention and care that an ill child must receive demands constant adult supervision, which may lead to a rise in TB cases worldwide. This article focuses on TB in children in developed countries. For the perspective on this disease elsewhere, see Tuberculosis in Children in Developing Countries.


TB in Children


Every year, over 250,000 children will become infected with TB and 1,000 children will die from TB disease [3]. These deaths can be prevented with proper treatment of the adults around them and of the children themselves. The immune system of a child is less developed than that of an adult, which means that a child’s ability to resist infection is not as high as an adult’s [11]. If exposed to TB, latent infection is more likely to escalate into TB disease [10, pg 625]. Diagnosis is also difficult in children. Normally, a stained sputum smear can identify the presence of mycobacterium tuberculosis in a patient’s body, but children have less sputum; young children often have to undergo gastric lavage in order to be tested for TB [9]. Children are also unlikely to even exhibit symptoms for about 2-12 weeks after being exposed [15]. This reduces the likelihood of identifying the cause of the infection, which is important for reducing the spread of TB generally as well as in children. Since children’s immune systems are weaker than most adults’, they are more prone to adverse effects associated with TB such as loss of hearing, blindness, and paralysis [11].

Children in developed countries have a better chance of getting treatment, however; public health systems in developed countries are often diligent in educating parents and other healthcare workers about symptoms to watch out for in children. These include rapid weight loss, cough, a fever that does not respond to antibiotic therapy for acute respiratory disease, abdominal swelling with a hard painless mass and free fluid, swelling in the lymph nodes, or signs of meningitis or disease in the central nervous system [12]. Developed countries may have an advantage over developing countries in terms of diagnosing and treating TB in children. For example, even though diagnosis in children can be difficult, the children in developed countries usually do not suffer from malnutrition and poverty to the degree that children in developing countries suffer. Malnutrition leaves a child even more weak and prone to infection, and complications that arise from malnutrition such as weight loss may overlap with TB symptoms [14], making diagnosis more difficult. Developed countries such as the US and the UK also are very likely to have the drugs and technology necessary to treat TB in children provided that the infection is detected early enough; usually children in developed countries are not even given the BCG vaccine because it is not 100% effective in preventing TB [13].

Typical treatment for children in developing countries is similar to treatment for adults [15]. The standard treatment consists of short-course, multi-drug treatment [10, pg. 624]. If detected early enough, the bacteria in the body may be destroyed with a combination of four main drugs: isoniazid (INH), rifampin (RIF), ethambutol (EMB), and pyrazinamide. The WHO recommends 2 months of all four drugs followed by 4 months of rifampin and isoniazid [10, pg 629]. Since children have a higher metabolism and can thus take more drugs with less risk of side effects, their doses should be higher per kilogram of their body weight. If the drugs are taken correctly, children are less likely to develop drug resistant TB, since they have fewer microorganisms [15]. Countries such as the US and the UK have come a long way in the fight to control TB since the 1980s. Thus, many people believe that TB is a “disease of the past” [2].

Fig. 1 TB Cases in children in English regions by place of birth and survey year. (Balasegaram et al. 775)


Developed Countries and the Spread of TB in Children


High incidence of TB has been linked to breakdowns of tuberculosis control programs [10, pg. 624]; this must be prevented. Even in developed countries, risk of infection can be high, especially due to increased travel and immigration. People in developed countries tend to travel a lot, especially for business or study. 50% of the world’s TB cases are located in 5 countries, including India, Indonesia, and China. Many Americans visit these three countries often. Since tuberculosis is so easily spread through the air, there is a risk of becoming infected if one travels to these countries [6]. We can see from these examples that there may be a steady flow of bacteria coming into developed countries and into areas within those countries that are not endemic.

In developed countries, immigration is becoming an issue central to tuberculosis. A retrospective study [1] done to monitor childhood TB disease patterns in England and Wales explores this issue. This study, conducted during a time when TB cases were increasing, could give us helpful information about migration patterns that facilitated the spread of disease. Between 1978-79 and 1988, there was a 60% decrease in tuberculosis cases in children in England and Wales according to the National Tuberculosis Survey; 2 other surveys (conducted in 1993 and 1998) were studied in comparison to the 1988 survey [1, pg 772]. The number of childhood TB cases rose from 308 in 1988 to 408 in 1993; this number fell to 364 in 1998. The proportion of cases in London doubled, reaching 49% in the decade between 1988 and 1998; the proportion of cases in children who were born outside of the UK grew from 13% to 27%. London saw an increase in TB cases from 1993 to 1998; there were 63 cases in 1988, 88 in 1993, and 178 in 1998 [1, pg 774]. The number of cases in children who were known to be born in the UK rose from 67% in 1988 to 72% in 1993, then fell to 42% in 1998. 1998 saw a rise in cases in children who had been born outside of the UK, as well as a slight rise in cases in children who had been born in the UK (see Fig. 1). This suggests that immigration was a factor in the rise in tuberculosis in London. Another scientific journal [10, pg. 624] states that a WHO high prevalence level of greater than 40 notifications per 100000 population has been reached in a third of London's boroughs. The study and the journal seem to support a hypothesis that the rise of cases of TB in London may have been caused by the diagnosis of cases in immigrants from endemic areas [1, pg 776].


Fig. 2 Ethnicity and place of birth of 192 childhood TB cases in San Diego County, CA in 1989, 1991 and 1993. (Kenyon et al. 3)
Fig. 3 TB cases in foreign-born persons as of May 20, 2009. (CDC, "TB Elimination: Now is the Time!")

Another study [7] focused on another area central to the immigration issues of developed countries: the United States-Mexico border in the county of San Diego, CA. The aim of the study was to identify possible reasons for the 400% increase in TB in children in San Diego County between 1985 and 1993. Reports of TB cases multiplied (culminating in a 51% increase) in children younger than 15 years between 1988 and 1992 in the United States, from 1133 cases in 1988 to 1708 cases in 1992. During the years of the study, California ranked first among the 50 states and the District of Columbia for number of TB cases in children (reporting 29% of all cases in children in the United States). Data on the tuberculosis cases reported to the San Diego Dept. of Health Services Tuberculosis Control Program in 1989 (before the main increase in cases), 1991 (during the increase) and 1993 (after the increase) was collected during the study (children with latent TB infection were not analyzed). Data such as birth certificates, health department records, demographic characteristics, household language, travel and immigration history, clinical information, and culture and drug susceptibility results was also collected and analyzed [7, pg 1]. For children younger than 7 years, there was a special emphasis on finding the source cases [7, pg.2]. The results showed an increase in immigration corresponding with an increase in tuberculosis cases. 62.3% of affected children were born in the US but were born to at least one parent who had been born in an endemic area (Mexico, the Philippines, Vietnam, Somalia, Laos, Ethiopia, and Guatemala). Children younger than 5 years old and of Hispanic ethnicity who were born in the US had the highest increase in cases (see Fig. 2); these children were also known to spend time with foreign-born adolescents. In 1989 the percentage of Hispanic children in the US was 70%; this escalated to 80.4% in 1991 and to 95.3% in 1993 [7, pg 2]. The rise in TB cases along the United States-Mexico border was attributed to transmission outside of the US in endemic areas, along with transmission to children within the US by household contacts from those areas [7, pg. 1]. This study shows us that it is important to screen adults along the border to identify cases and treat them before they spread, especially to children. Only 54% of the identified source cases were parents; the foreign-born or first-generation children who were infected were in close contact with relatives and friends from endemic areas [7, pg. 5]. It is easy to see the problem that this poses; children can spread TB germs to their friends and schoolmates, and to other adults who may take care of them. This study shows us both the extent of the problem that immigration poses to the control of tuberculosis and the extent that adults can transmit tuberculosis to their children.

The immigration problem has continued to influence current TB trends (see Fig. 3); 59% of all TB cases diagnosed in the US in 2008 were in foreign-born persons, compared to 42% in 1998 [2]. From the aforementioned studies, we can get a sense of the importance of surveillance when it comes to the spread of TB among people from endemic areas.

Problems in Developed Countries


TB in children is a good indicator of disease patterns in adults [1, pg. 772], since children are usually infected with TB after transmission from adults. The spread of TB from adults to children, even in developed countries, is a serious issue, especially considering the weaker immune systems of children; in fact, children should be treated for latent infection [10, pg. 624) as well as for the disease, because 40%-50% of infants and 15% of older children will develop TB disease within 1-2 years of becoming infected. The progression of TB infection from latent to active is faster in children than it is in adults [10, pg. 625]. Therefore it is important for adults with TB disease to be diligent in taking their medicine so as to prevent transmission to children.

Compliance is especially important to the health of TB patients, both adults and children [10, pg. 624]. If the medicine is not taken correctly, the bacteria may become resistant to the drugs, leading to the development of multi-drug resistant TB (MDR-TB) within the patient; MDR-TB can be spread from person to person just like drug-susceptible TB [18]. MDR-TB is classified as a strain of TB that is resistant to the two major drugs used in common treatment, isoniazid and rifampin [2]. It is especially important that children do not become infected with multi-drug resistant TB; the second-line drugs used to treat MDR-TB may cause more side effects [16]. MDR-TB is also extremely expensive to treat; the medical costs associated with one case of MDR-TB can be as much as $1.5 million. Finally, people with MDR-TB are more likely to die from their disease [2]. Even though children are less likely to contract MDR-TB, the incidence of MDR-TB is increasing [10, pg. 624]. If people from endemic areas have not taken their medicine correctly, they can be a danger to their own children as well as others. As shown from the previous studies, infected adults can have a major impact on the health of children; MDR-TB could spread from adults to children more easily if cases increase in adults.

What is most unsettling is the fact that the problem of transmission of both kinds of TB continues in a cycle; not only can adults easily infect children; children are a “reservoir” for the development of adult cases [8, pg. 115]. If the number of children with TB rises and the children’s caretakers seek treatment for them as they are supposed to do, the health care professionals and staff who attend to them could be at risk for developing TB; all health care professionals are at risk for developing TB if they treat a person with TB disease [13]. Finally, while immigration and travel are important factors in the spread of TB, transmission of TB can be facilitated by other factors such as overcrowding [10, pg. 624], which could be a problem for children in poor or inner-city areas in developed countries.

Conclusion


The spread of TB in children is a problem even in developed country. It is important for people in developed countries to acknowledge that TB is not a "disease of the past" but is very real and dangerous. The resurgence and 20% increase of TB cases between 1985 and 1992 in the US has been linked to the country's lack of diligence relating to the issue [2]; this cannot be allowed to happen again. Adults with TB who are not treated or who do not take their drugs correctly can spread TB (including its more lethal drug-resistant forms) to children whose immune systems are more vulnerable; children can in turn infect more people. The cycle must be stopped. Preventive measures such as mandatory screening of immigrants from endemic areas should be enforced, as well as proper surveillance of all TB cases. With effort, we can keep our children and our nation healthy.

References

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Edited by student of Joan Slonczewski for BIOL 191 Microbiology, 2009, Kenyon College.