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Bovine tuberculosis: A growing threat

Maneka Sanjay Gandhi

Bovine tuberculosis (bTB), a cattle disease, is a major public health threat. It is transmitted within herds by inhalation of infected aerosol droplets from infected cattle.

Despite the considerable economic costs, and zoonotic risk, India still does not have any accurate estimates. No surveillance, no checking systems and absolutely no national disease control programmes. Not even the education of farmers. In fact, India has the poorest veterinary system in the world. It is one of the few countries left where the disease is considered endemic.

A metastudy called ‘Prevalence of Bovine Tuberculosis in India: A systematic review and meta-analysis’, done by Srinivasan, Easterling, Rimal, Maggie, Niu, Conlan, Dudas, Kapur, published in June 2018, reveals that there are about 21.8 million infected cows and buffaloes in India, more than the total number of dairy cows in the USA.

Bovine tuberculosis (bTB) is caused by a bacterium called Mycobacterium bovis. While it mainly affects cattle, the bacteria affects a large number of species, and it has been estimated that M bovis causes 10 per cent or more of the total human TB cases in India and poses a significant threat to global health (Olea-Popelka et al, 2014).

To remove tuberculosis from humans will require removing bTB from cattle simultaneously.

A government survey done in 2018 showed 2.690 million cases of tuberculosis, 199 people per lakh in India. Mortality is 32 people per lakh – a million times more than the “pandemic” corona virus. India has the highest number of sufferers in the world, with 2.8 million cases annually, more than a quarter of the tuberculosis patients all over the world. Much, much, worse is the fact that India has the largest burden of multi-drug-resistant tuberculosis among all countries, with almost 150,000 cases every year.

Much of this is from drinking milk, eating milk products, and eating beef. The bacterium, Mycobacterium bovis, survives one-eight weeks in cattle faeces, so anyone handling gobar is at risk.

Pasteurisation kills the bacteria but is your milk pasteurised? Forget the consumer, when the dairy owner is physically taking out the milk from the animal, he stands a strong risk of getting bTB. When we surveyed the Idgah slaughterhouse, which I shut down 30 years ago, most of the butchers had bTB, getting it from the infected meat. It is as prevalent today among dairy workers and butchers. Their spit and perspiration on the meat, gives it to you.

Do you know where your milk came from? Are there any records of dairies kept by the local district chief veterinary officer? We are told that pasteurisation kills the bTB bacteria. But most people in small towns (70 per cent of India according to FAO/OIE/WHO, 1993) get their milk unpasteurised from the dairy next door – the man who keeps a few cows in a makeshift shed and allows them to roam around and eat garbage the whole day so he doesn’t have to feed them. He has no licence, no parameters, no government controls. The milk that is bought from him is simply boiled by you – killing no tuberculous bacteria. No mithai seller uses pasteurised milk (if he uses real milk at all). He gets his milk from a small unregistered dairy.

Before pasteurisation was made compulsory in western countries a century ago, M bovis accounted for 25 per cent of all TB cases in children (Roswurm & Ranney, 1973). But it is not compulsory in India. So, how many lakh Indian children have it? All studies say that the disease is going to increase in the coming years due to the growing intensification of dairy and cattle grown for export. For instance, cattle herds in Puri, Odisha have increased in bTB from 9.1 per cent to 84.7 per cent (Dhanda and Lall).

We have 300 million cows and buffaloes, the largest population of cattle in the world (Basic Animal Husbandry and Fisheries Statistics, Government of India, 2017). We have the largest beef export. Therefore, we have the potential to infect the whole world with bTB.

Animals are more likely to be infected by M bovis when they are poorly nourished or under stress. There is evidence that intensive dairy farms have a higher risk of infection. The bacteria is spread by infectious animals – in their breath, milk, open lesions, saliva, urine or droppings. In cattle, excretion of M bovis begins around 87 days after infection occurs. It spreads from cows to calves via the milk.

What are the symptoms in cattle? In the early stages, clinical signs are not visible. In the later stages, clinical signs may include: sluggishness, emaciation, lethargy, weakness, anorexia, low-grade fever, and pneumonia with a soft chronic, moist cough and a chest wheeze. The lymph nodes may be enlarged. If the animal is killed for its meat in an early stage of TB, the microscopic lesions will be missed – that is, if someone is looking. No slaughterhouses in India have even the most basic TB skin test.

Cattle need to be isolated and treated with a combination of antibiotics for six-12 months. But who will do this? In the unlikely event that the cattle are tested for bTB, which dairyman will spend money on their treatment. He is more likely to keep taking the milk and then, as they grow sicker and the milk dries up, he will sell them for meat. The meat is sold with no warning to processors or consumers that it comes from TB infected cattle.

Tuberculosis is often fatal. It is a long-lasting disease that cripples through emaciation, coughing, abdominal infections, enlarged lymph nodes and general bad health. The name, tuberculosis, comes from the nodules, called ‘tubercles’, which form in the lymph nodes of affected animals and people. M Bovis causes the same problems as M Tuberculosis – except that it is even more resistant to drugs. Not everyone exposed to the mycobacterium bovis bacterium will develop symptoms. If symptoms of bovine TB occur, they can include: fever, night sweats, persistent cough, diarrhoea, weight loss and abdominal pain. According to WHO, about 143,000 people die of M Bovis annually. Corona virus with 10,000 deaths has frightened us. This is so much bigger.

The BCG vaccine, invented in the 1920s by Calmette and Guerin, had proved to be ineffective. It reduces the severity of the disease but does not prevent infection. Cattle that are vaccinated with the BCG vaccine, which contains a harmless strain of the bovine TB pathogen mycobacterium bovis, make it impossible to distinguish, with the skin test, if the animal has TB or has simply been vaccinated. The vaccine is banned in most countries.

The study recommends: a national surveillance programme using a single, well-standardised skin test performed by independent, well trained operators using approved protocols and well-standardised tuberculin antigen.

Is the government going to do this? No. So human tuberculosis in India will not slow down, inspite of our signing the World Health Assembly protocol in May 2014 to end the global TB epidemic by 2035. Any attempt to eradicate the disease from humans without eradicating it from cattle is futile.

You need to protect yourself. Don’t drink milk or any dairy based product and don’t eat meat.

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