Diseases crossing species barriers: Tuberculosis
Animal and human health is inextricably interwoven. Food derived from animals, especially cattle serve as a reservoir of diseases of public health importance. Nobody seems to take notice of this in the public health community of Pakistan. A series of blogs is started to high highlight the issues involved and the problems this negligence is resulting in a multitude of health problems. Some of the next topics would include dengue, rabies, leishmania, anthrax, cholera.
If there was one advice I wanted my children to follow when I was no more would be to never drink raw milk or eat it as cheese. I don’t believe claims that pasteurising milk destroys its nutritional value or that it’s a conspiracy of big agribusiness and government to promote the interests of big pharma. Pasteurisation of dairy products indeed is the single most effective means to prevent spread of tuberculosis in human beings. Here is how the story goes.
TB remains Pakistan’s leading cause of death among infectious diseases – about 68,000 people die of TB every year in the country. Three-quarters of those infected are never diagnosed by a doctor. The problems is indeed getting out of hands every passing day due to a complex interplay of factors like inadequacies of the TB Control Program, lack of coordination amongst the different players, poverty, stigma, and lack of awareness.
Pakistan has a population of about 30 million cattle and 27 million heads of buffalo. Bovine tuberculosis is not only a threat to these animals but is also an important public health problem. TB is prevalent at epidemic proportions in these domestic animals.
Mycobacterium bovis, the bacteria that causes bovine tuberculosis and mycobacterium tuberculosis, that causes classical human tuberculosis, are genetically and anti-genically very similar and cause identical clinical disease in humans. It is now well established that the bovine TB amongst other factors may be prevalent in the Pakistani population due to use of unpasteurised or poorly pasteurized milk.
As if totally unaware of these facts, health authorities, local and provincial governments, TB control programs, international donors spending billions of rupees remain focused on controlling TB at human beings level only.
Fact of the matter is that bovine TB has never been seriously attended to in the country even though there is a vast and growing body of anecdotal experience showing high prevalence and transfer of bovine TB to humans.
There is also a lot of evidence from industrially developed countries showing how bovine tuberculosis eradication campaigns and mandatory milk pasteurisation have led to a huge reduction in the prevalence of human tuberculosis.
But bovine TB is not the only disease that goes across the species boundary to inflict ill health to human beings. There is a need for a comprehensive understanding of the problems and adopting a comprehensive approach to minimise the threats it poses to human well being.
Diseases that are naturally transmissible from animals to humans and vice-versa are classified as “zoonoses”. Over 200 zoonoses have been described in literature and they have been known for many centuries. They are caused by all types of agents: bacteria, parasites, fungi, viruses and unconventional agents.
Some 60 per cent of all human diseases and 75 per cent of all emerging infectious diseases are animal-borne diseases. In actual terms, such “zoonotic” transfer of diseases from animals to humans are responsible for 2.5 billion cases of human illness and 2.7 million deaths a year, according to a recent study. Stomach and intestinal illnesses, mostly due to contaminated food, are the biggest killer, causing 2.33 billion sick cases and 1.5 million deaths around the world.
The existing TB situation in the country calls for a comprehensive program to control spread in livestock. The case for mandatory milk pasteurisation also seems to be overwhelming. There must be necessary legislation, as well as promotion of appropriate practices in the market and at consumer level.
Ayyaz Kiani is a public health specialist. He heads Devnet – a network of development consultants. Based in Islamabad, he has travelled around the world and continues to do so to meet fellow travelers. He can be contacted at email@example.com
The views expressed by this blogger and in the following reader comments do not necessarily reflect the views and policies of the Dawn Media Group.