Tuberculosis

Background

Tuberculosis (TB) is a disease caused by:

  • Mycobacterium tuberculosis
  • M. bovis
  • M. africanum
  • M. canetti
  • M. microti

Together they form the Mycobacterium tuberculosis complex.

There are two forms of TB. The first affects the lungs and the other causes infection elsewhere in the body. The symptoms that occur when TB disease develops aren't usually very specific but often there are complaints of:

  • tiredness
  • listlessness
  • loss of weight
  • night sweating

When TB affects the lungs, a cough is usually present for weeks or even months.

TB is a notifiable disease under the Public Health etc. (Scotland) Act 2008. More information on the Public Health etc. (Scotland) Act 2008 is available from the Scottish Government website.

The Scottish Mycobacteria Reference Laboratory (SMRL) undertakes the identification, including molecular characterisation, and susceptibility testing of all mycobacterial isolates in Scotland, both for clinical management and for epidemiological purposes. The laboratory reports all identification results weekly to our organisation through the Electronic Communication of Surveillance in Scotland (ECOSS).

Transmission

Transmission of TB is by inhalation of infected droplets and requires prolonged close contact, for example sharing sleeping quarters, with an infected individual. An important feature of TB is that after infection, the bacteria can remain latent in the body for a long time, possibly even lifelong, causing no symptoms. People with latent TB infection are not infectious. Under favourable conditions, the bacteria can start multiplying and cause clinical disease.

Guidance

The following guidance has been approved for use in Scotland by the Scottish Health Protection Network Guidance Group (SHPN-GG) and should be used in conjunction with the SHPN addendum:

Other guidance:

 

For all infection prevention and control guidance visit the A-Z ​pathogens section of the National Infection and Prevention Control Manual.

Data and surveillance

The establishment of the Enhanced Surveillance of Mycobacterial Infections (ESMI) scheme in 2000 represented a major development in the surveillance of TB in Scotland. Our organisation co-ordinates the scheme and incorporates the European minimum dataset and provides feedback to the various agencies involved in the diagnosis, treatment and control of TB.

Overall numbers, rates and geographical distribution

Tuberculosis infographic 2019A total of 271 cases of TB were reported to the ESMI scheme in 2018, equating to an annual incidence of 5.0 cases per 100,000 population.

This was a 7.5% decrease in the number of cases and a 7.7% decrease in annual incidence when compared with 2017 (293 cases, 5.4 cases per 100,000 population).

Gender and age

In 2018, 61.3% of TB cases occurred in males (166 cases or 6.3 cases per 100,000 population). The incidence of TB was higher among males in all age groups except those aged 15 to 24 years and those aged 85+ years.

As shown in Figure 2, TB incidence was highest in those aged 35 to 44 years, (9.0 cases per 100,000 population) and lowest in those aged 5 to 14 years (0.5 cases per

100,000 population).

Place of birth

Place of birth was known for 94.1% of cases in 2018. Of these, 60.0% were born outside of the UK. As shown in Figure 3, this is a slight increase in the percentage of non-UK born cases when compared with 2017 (57.2%).

As shown in Figure 4, the incidence of TB among those born outside of the UK and those born within the UK have both decreased over the past several years. In 2018, TB incidence in those born outside of the UK (32.6 cases per 100,000 population) was over 15 times higher than the incidence in those born within the UK (2.1 cases per 100,000 population), which is comparable to previous years.

Drug resistance

The first line drugs considered for the treatment of TB in the UK are isoniazid, rifampicin, ethambutol, and pyrazinamide. Of the 186 culture-confirmed cases of TB reported in 2018, 184 had drug susceptibility tests for both isoniazid and rifampicin. Among these, resistance to at least one first line drug at the start of treatment was reported for 29 cases (15.8%). Further to that:

  • 16 cases (8.7%) were resistant to isoniazid
  • 2 cases (1.1%) were resistant to rifampicin
  • 2 cases (1.1%) were resistant to ethambutol
  • 16 cases (8.7%) were resistant to pyrazinamide

Based on the above, the proportion of isolates resistant to any first-line drug and to isoniazid and pyrazinamide individually in 2018 are at the highest levels seen since enhanced surveillance began. In addition, two cases (1.1%) were resistant to both isoniazid and rifampicin and were therefore classified as multidrug-resistant TB (MDR-TB). There were no cases of extensively drug-resistant TB in 2018.

TB outcomes in the drug sensitive cohort at 12 months

In 2017, 293 cases of TB were reported to ESMI of which one case was rifampicin resistant and was therefore excluded from outcomes analysis. Outcomes data were available for 94.5% cases, of whom 85.8% had successfully completed treatment at 12 months, which is slightly higher than that reported in 2016 when 82.1% of cases successfully completed their treatment.

Vaccination

The Bacille Calmette Guérin (BCG) vaccine is offered to those babies who are more likely than the general population to come into contact with someone with TB. This is because they either lived in an area with high rates of TB, or their parents or grandparents came from a country with high rates of TB. These include some countries in Eastern Europe, as well as South-East Asia and sub-Saharan Africa.

The vaccine is usually offered soon after birth, either while the baby is still in hospital or soon after the patient returns home. However, it can be given at any time if necessary. The vaccine gives protection against severe forms of the disease, like TB meningitis and miliary TB, in children under five years of age. Further information can be found in the green book, chapter 32, on the Public Health England (PHE) website.


BCG vaccine for the national immunisation programme

Since 2015, deliveries of a UK licensed BCG vaccine from the Statens Serum Institut (SSI) in Denmark, were interrupted due to manufacturing issues and this vaccine was unavailable.

From June 2016, PHE secured an alternative BCG vaccine for use across the UK. InterVax BCG vaccine was then used for the national BCG immunisation programme. This was supplied as an unlicensed product, which meant it did not have a valid licence in the UK. The vaccine was provided in accordance with medicines legislation allowing an unlicensed medicine to be supplied when a licensed alternative was not available.

In August 2018, AJ Vaccines resumed supply of licensed BCG vaccine into the UK. There are no current restrictions on ordering quantities of the AJ Vaccines BCG vaccine for the national BCG programme.