Infections in tropical and developing countries

12.4 Infections in tropical and developing countries

Stephen Graham, David Brewster

Most of the world’s population lives in the tropics and subtropics in developing countries where health outcomes are much poorer than in developed countries such as Australia or New Zealand. Infections are a major cause of childhood disease in these settings and an important contributor to overall child mortality. Rather than geography and climate, however, it is socioeconomic factors that have most influence on susceptibility to infections, leading to high mortality. These factors are highlighted in Chapter 1.2: Child health in a global context. They include low levels of female literacy, lack of access to clean water, poor sanitation and hygiene, nutritional insecurity, and inadequate health-care resources, including human resources. The main causes of morbidity and mortality are not exotic tropical diseases but common conditions such as pneumonia, malaria, diarrhoea, sepsis and human immunodeficiency virus (HIV) infection caused by common pathogens.

The main seasonal influences in the tropics are the rainy season, when there is increased exposure to pathogens (e.g. malaria and diarrhoea), and the hungry season, when there is food insecurity. These seasons tend to coincide resulting in a strong seasonal influence on the prevalence of childhood malnutrition. Poor nutrition is an important contributor to the high childhood mortality rate from infectious diseases in the developing world, including intrauterine growth retardation resulting in low birth weight. Over half of child deaths are due to the potentiating effect of malnutrition on infections. Malnutrition can also be a consequence of recurrent or chronic infections.

The purpose of this chapter is to give an overview of common infections in tropical regions, including Australia, and developing countries. It is not possible to discuss in detail the many disorders endemic to these areas. The focus of the chapter is on the common infectious causes of childhood disease, with an emphasis on public health and prevention.

An overview

Prevention and disease control

Three of the seven Millennium Development Goals (MDGs) set in 2000 for 2015 have direct relevance to childhood infections:

• MDG 4: Reduce by two-thirds the mortality rate among children under 5 years of age

• MDG 6: Halt and begin to reverse the spread of HIV/AIDS and the incidence of malaria and other diseases

• MDG 7: Reduce by half the proportion of people without sustainable access to safe drinking water and basic sanitation.

Although these MDGs are unlikely to be achieved in many high-mortality settings, they have provided an important focus and substantial progress has been made in the last decade. Important child health programmes that reduce the burden of infectious disease include the Expanded Programme on Immunization (EPI), breastfeeding promotion and infectious disease control programmes. Immunization against measles and polio, for example, has been highly effective and highly cost-effective. EPI continues to be expanded with the addition of Haemophilus influenzae type b (Hib) conjugate vaccine and hepatitis B vaccine to the schedules of many low-income countries in recent years. Vaccines against Streptococcus pneumoniae (pneumococcus) and rotavirus are the likely next candidates for wider implementation in low-income countries.

Gains are also being made by disease control programmes using a combination of reducing transmission of infections and more effective treatment. Three infections that have received particular attention and funding support to national control programmes are HIV, tuberculosis (TB) and malaria. HIV has had a profound impact on child morbidity and mortality in high HIV-endemic countries. Strategies that lead to a reduction in antenatal HIV prevalence and prevent mother-to-child transmission of HIV will reduce HIV-related child mortality as well as reduce the burden on child health-care services. Antiretroviral treatment of the mother during and after pregnancy can reduce the risk of HIV transmission to the newborn to less than 1%, and make breastfeeding a feasible option. The HIV epidemic has also increased the prevalence of TB, including drug-resistant infection. In malaria-endemic settings, children and pregnant women are particularly susceptible to severe disease. Malaria control is being improved with increased usage of insecticide-treated bed-nets and more effective first-line therapy.

Integrating and improving clinical case management

The usual clinical presentations of infections in tropical and developing countries are as one or more of typical clinical scenarios (e.g. respiratory distress, diarrhoea with dehydration, sepsis, anaemia or febrile seizures). There is clinical overlap between disease groups, a range of possible causes including the possibility of co-infections with more than one pathogen, and the need for health workers to assess and promptly treat the most likely infectious causes, often empirically on the basis of clinical assessment alone. Further, these challenges are particularly common in those at greatest risk of death, such as the young infant, the malnourished or the HIV-infected.

The World Health Organization (WHO) has developed treatment protocols for the common diseases, based upon simple clinical indicators, that can be assessed by health workers with minimal training. The Integrated Management of Childhood Illness (IMCI) initiative aims to reduce child morbidity and mortality in developing countries by improved management of common illnesses (Box 12.4.1). This integrated horizontal approach aims to avoid the limitations of a vertical single-disease approach. This will hopefully provide improved patient care as well as recognition of the importance of integration between national disease control programmes. Evaluation studies of the quality of care at hospitals and health centres in the developing world consistently report major deficiencies in triage, emergency care, monitoring, drug availability, staffing levels and the use of protocols for clinical care. On the other hand, implementation studies show what can be achieved when such deficiencies are addressed, even with limited resources. In 2005, WHO published a pocketbook of guidelines for the management of common illnesses in health facilities with limited resources.

Box 12.4.1 Diagnostic classifications and clinical signs for referral to hospital

Young infants (0–2 months)

1. Possible serious bacterial infection – seizures, tachypnoea (≥ 60 breaths/min), severe chest indrawing, nasal flaring, grunting, bulging fontanel, perforated eardrum, omphalitis, fever or hypothermia (≥ 38 °C or < 30 °C), many or severe skin pustules, difficult to wake up or cannot be calmed within 1 hour

2. Diarrhoea with severe dehydration – lethargic or unconscious, sunken eyes and skin pinch goes back very slowly

3. Severe persistent diarrhoea (≥ 14 days)

4. Not able to feed

Children (2 months to 5 years)

1. General danger signs – not able to drink or breastfeed, vomits everything, convulsions, or lethargic or unconscious

2. Severe febrile disease – fever (rectal temperature ≥ 38 °C) and any general danger sign, or stiff neck

3. Severe pneumonia – cough or difficult breathing and any general danger sign, chest indrawing, or stridor when calm

4. Diarrhoea with severe dehydration – abnormally sleepy or difficult to wake up, sunken eyes, not able to drink or drinking poorly, skin pinch goes back very slowly

5. Severe persistent diarrhoea (≥ 14 days) with dehydration – restless/irritable, sunken eyes and skin pinch goes back slowly

6. Severe malnutrition or severe anaemia – visible severe wasting, oedema of both feet, or severe palmar pallor

Adapted from World Health Organization Integrated Management of Childhood Illness.

Travel bug

The ease of air travel and the frequency of people of all ages visiting the tropics have made it essential for the student and practising doctor to have an appreciation of tropical medicine. Migration, including for humanitarian reasons (refugees), makes it almost certain that some will carry disease undetected by the medical screening process. The majority of children with TB infection or disease identified in Australia have recently immigrated from or spent time in TB-endemic countries. It is of the greatest importance that a history of overseas travel is sought in any unusual disease presentation, particularly a febrile illness.

Invasive bacterial disease

Serious bacterial infections are much more common in children in tropical and developing countries than in temperate and developed countries, and 25% or more of children dying in hospital have bacteraemia. Studies from tropical Africa in infants and children hospitalized with a wide range of presentations, including severe malaria, have documented that invasive bacterial infections are common and associated with a high case-fatality rate.

Common clinical presentations include:

• septicaemia with or without focus

• bone and joint sepsis

• soft tissue sepsis (e.g. abscess, cellulitis, pyomyositis).

Important risk factors for disease incidence and/or poor outcome include:

• Age: particularly common in infants and young children. Neonatal sepsis is a major contributor to the high neonatal mortality in developing countries.

• Co-morbidities: such as malnutrition, HIV infection, measles or sickle cell disease.

• Late presentation to health services: common in resource-limited settings.

Pneumococcus and Hib have been the commonest causes of invasive bacterial disease in children beyond the neonatal age group. The increasing uptake of Hib conjugate vaccine into EPI schedules has resulted in a dramatic reduction in the burden of invasive disease due to Hib, including meningitis. Pneumococcus is the commonest cause of bacterial pneumonia and meningitis in developing countries. Uptake of the pneumococcal conjugate vaccine has been limited in low- and middle-income countries due to cost constraints. However, wider implementation of a vaccine that covers the majority of the serotypes causing disease is high on the global public health agenda, such as the GAVI Alliance.

Other causes of invasive bacterial disease include the Gram-negative enteric pathogens (e.g. Salmonella spp, Escherichia coli, Klebsiella pneumoniae) and Staphylococcus aureus. They are important causes in the young including neonates, the malnourished and HIV-infected. Resistance of Gram-negative bacilli to multiple antibiotics is common. S. aureus is an important cause of bone, joint and soft tissue sepsis, as well as of pneumonia in association with measles and HIV infection.

Salmonella infections occur worldwide but are particularly important in tropical and developing countries. Enteric or typhoid fever is due to Salmonella typhi and S. paratyphi. Typhoid fever is confined to humans, and occurs where standards of hygiene, water supply and sanitation are poor. The typical presentation is fever, malaise, headache, abdominal discomfort, and sometimes vomiting and diarrhoea. In severe disease, toxaemia is profound and complications such as small bowel perforation can occur in older children. This typical presentation of typhoid fever is mainly in children of school age. In younger children, S. typhi often presents with a non-specific febrile illness. Invasive disease due to S. typhi is particularly common in Asia and some Pacific Islands.

There are over 2000 serotypes of non-typhoidal salmonellae. In developed countries, the usual presentation is acute gastroenteritis due to food poisoning. In malaria-endemic regions of Africa, non-typhoidal salmonellae commonly cause severe invasive disease in children, including meningitis in infants, especially during the rainy season, presenting as a non-specific febrile illness with a high case-fatality rate of 20–25%. Consistent clinical associations include young age, malaria, anaemia, malnutrition and HIV infection.

Antibiotic resistance to ampicillin, co-trimoxazole and chloramphenicol (multidrug resistance) is now common for S. typhi in Asia and for non-typhoidal Salmonella in Africa. This poses a management challenge in settings where availability and choice of antibiotics is limited. Third-generation cephalosporins (e.g. ceftriaxone) or quinolones (e.g. ciprofloxacin) are usually effective alternatives, although quinolone resistance is increasing in Asia.

Group A streptococcus is also important in developing countries, not as a major cause of invasive disease in children, but more as a cause of pharyngitis and skin sepsis in communities where rheumatic heart disease and acute glomerulonephritis are common and cause significant morbidity.

Viruses

Finally, it is important to recognize that viruses are a common cause of lower respiratory tract infection and diarrhoea in developing countries. The causes are similar to those in developed countries, but with less marked seasonal variation in the tropics. With improved socioeconomic conditions in communities in the Asia–Pacific region, viruses are responsible for a larger proportion of disease than bacteria, and virus-induced airway disease (e.g. acute bronchiolitis, asthma) is increasingly common. This has important implications for clinical management guidelines such as IMCI protocols, and appropriate use of antibiotics.

Practical points

Bacterial infections

• Serious bacterial infections are common in children in developing countries and associated with a high case-fatality rate.

• Important causes include pneumococcus, Haemophilus influenzae type b, multiresistant Enterobacteriaceae (e.g. Salmonella, E. coli) and Staphylococcus aureus.

• IMCI guidelines aim to help primary care health workers to identify children needing antibiotic treatment.

Tuberculosis

It is estimated that a third of the world’s population is infected with Mycobacterium tuberculosis and almost all live in developing countries. Most of these people have latent TB infection and will not develop TB disease. However, many do develop disease, most commonly pulmonary tuberculosis (PTB), and infection is readily transmitted through coughing. Children are usually infected by contact with an adult or older child with sputum smear-positive PTB. Generally, children under 8–10 years of age do not develop pulmonary cavities; thus they have pauci-bacillary disease which is not considered contagious, and do not require isolation.

If a child is infected, the risk of developing symptomatic TB disease depends on:

• Age: infants and children aged less than 3 years have a much higher risk of disease than older children, and a high risk of severe disseminated forms of disease such as TB meningitis.

• HIV co-infection: HIV-infected children are at increased risk of exposure/infection because they live in families with TB/HIV, and at much higher risk of disease than HIV-uninfected. Antiretroviral therapy (ART) reduces the risk of developing disease following infection in HIV-infected children.

• Other co-morbidities: severe malnutrition, recent measles or other conditions associated with immunosuppression.

• Bacille Calmette–Guérin (BCG) vaccination: given to newborns in TB-endemic countries, this provides some protection against severe forms of TB in young children, such as TB meningitis and miliary TB. It is recommended that BCG is not given to HIV-infected infants because of the risk of disseminated BCG infection.

The commonest form of TB in children is PTB (about 75% of cases) and most cases present in young children, as do TB meningitis and miliary TB. Other forms of extrapulmonary TB that tend to present in older children include TB adenitis (cervical TB is commonest), TB pleural effusion, TB ascites or spinal TB.

Common clinical features associated with a diagnosis of TB include a persistent cough not responding to broad-spectrum antibiotics, weight loss or failure to thrive, persistent fever, and fatigue or reduced playfulness. A history of contact with an infectious case should be carefully sought, and is often positive in young children. The diagnosis of PTB is usually based on clinical and radiological features because young children have pauci-bacillary disease and have difficulty in providing sputum for microscopy. Sputum smear-positive disease is not unusual in older children and adolescents, but the yield from gastric aspirates or induced sputum in young children is very low. Thus, TB diagnosis in young children remains one of the most challenging issues in paediatric practice in tropical and developing countries with HIV and malnutrition, and diagnostic algorithms perform poorly.

An HIV test should be routine in assessment of children with suspected TB. This is because HIV infection increases risk of TB disease and is associated with a poorer outcome. Further, the diagnosis of TB in children with chronic respiratory symptoms can be more challenging in HIV-infected children because there are other forms of HIV-related lung disease to consider such as lymphoid interstitial pneumonitis and bronchiectasis.

Children with TB receive similar regimens to adults depending on the type of disease, but at higher dosages in milligrams per kilogram (mg/kg). Children tolerate anti-TB therapy very well and serious adverse events are rare. HIV-infected children with TB require co-trimoxazole preventative therapy and antiretroviral therapy (ART) in addition to anti-TB therapy. ART improves outcome in HIV-infected children treated for TB disease, and is generally commenced as soon as TB treatment is tolerated. Although there is a risk of immune reconstitution inflammatory syndrome (IRIS) in the severely immuno- suppressed child, early HIV treatment appears not to increase mortality.

Children who are close household contacts of source cases with TB, especially those with sputum smear-positive disease, should be screened. Those with symptoms suggestive of TB disease should be assessed and investigated as appropriate for possible TB disease. Asymptomatic children at risk of developing disease after exposure: any child contact aged less than 5 years, or an HIV-infected child of any age, should be given preventative therapy following exclusion of active disease.

Practical points

Tuberculosis

• Childhood TB is common in countries with a high incidence of sputum smear-positive TB in the community.

• Diagnosis is usually clinical, and important features in children include persistence of symptoms, history of contact with a source case, age and nutritional status of the child, and HIV infection status.

Only gold members can continue reading. Log In or Register to continue

Related

Stay updated, free articles. Join our Telegram channel

Tags: Practical Paediatrics With STUDENT CONSULT Online Access

Aug 4, 2016 | Posted by admin in PEDIATRICS | Comments Off

Full access? Get Clinical Tree

Get Clinical Tree app for offline access

Get Clinical Tree app for offline access