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Tuberculosis – between a Brock¹ and a hard place

| October 20, 2013

Badgers are short-legged omnivores. 11 species of badger are grouped in three subfamilies: Melinae (9 European badgers), Mellivorinae (the honey badger) and Taxideinae (the American badger).

In August, a 6 week cull of 5,000 badgers started in the UK counties of Gloucestershire and Somerset, with the aim of helping to bring bovine tuberculosis (bTB) under control. Badgers in the UK, contrary to other European countries, are a protected species and considered by many as a valued creature of the UK countryside; one that has been romanticised in European folklore and modern literature.

Badger culling in the UK is not new, having taken place on 2 previous occasions. Farms in the South West of the country, considered a bTB hotspot, have been particularly badly hit and like farmers across the rest of England and Wales, endure regular TB testing and the financial burden of having cattle movement restricted and cows taken for slaughter, if detected positive for the disease.

It was also not so long ago that dairy farmers were among those most likely to suffer the human form of tuberculosis (hTB) originating from their close contact with animals and the consumption of unpasteurised milk.

Tuberculosis has variously been known by a variety of names including phthisis pulmonaris and consumption. The roots can be traced back to soil organisms that existed 15,000 to 20,000 years ago. Symptoms are weight loss, fever, chronic productive cough, and death.

Usually contracted by inhalation, less commonly by ingestion, and rarely through an infected wound, it may affect other organs such as the bones – particularly the spine, kidneys, brain, lymph nodes, intestine, and skin. The tuberculosis bacterial infection was discovered in 1882 by the German microbiologist Robert Koch.

The bacteria, Mycobacterium tuberculosis is a complex of closely related Mycobacterium species, including M. tuberculosis, M. bovis and M. africanum. It is spread through the inhalation of droplets from coughs or sneezes of infected individuals. A serious condition, it can be cured with a combination of specific antibiotics. The pulmonary form is the contagious form and spread after prolonged exposure. In most healthy people, the immune system kills the bacteria and there are no further symptoms.Sometimes the bacteria are not killed and may remain in the body, a condition known as latent TB which can develop into an active TB infection at a later date.

TB is the leading cause of death due to a single infectious agent among human adults and the second leading cause of death from an infectious disease, after HIV/AIDS. Persons with compromised immune systems, such as people living with HIV, malnutrition or diabetes, or people who use tobacco, have a much higher risk of falling ill.

History in the UK

Although UK deaths from hTB have declined over the last 100 years (figure 1), there has been a gradual increase in the number of human tuberculosis (hTB) cases observed in the UK over the last 20 years. With global migration population on the increase it is not surprising that 73% of new TB cases are with people born outside the UK. The incidence within the UK-born population has remained stable at 4.1 deaths per 100,000 per year. The incidence of hTB in the UK remains high compared to most other Western European countries, with 8,751 cases reported in 2012.

TB Deaths

Figure 1 – Only persons for whom TB was reported to be the underlying cause of death are included. Sources: Office for National Statistics (notifications of infectious disease deaths).

Footnote: 1: Brock is an Old or Middle English and slang name for a badger; derived from the Celtic word broc meaning badger.

This is a preview of a full article published in International Pest Control – September/October 2013 issue.

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Author: D A Loughlin is editor of International Pest Control Magazine and owner of Sentomol Ltd.

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Category: Animal Health

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