Tuberculosis in animals
Posted on: 23 Jul 2012
Tuberculosis is one of the top three infectious diseases along with HIV/AIDS and malaria. It infects nearly a third of the world's population and still kills well over two million people a year, with India heading the list. Jawaharlal Nehru's wife Kamala died of it in her early thirties. It is the fastest spreading disease in our country.
Why is tuberculosis not eradicable? In large part, because we continue to drink milk and eat meat. Human tuberculosis is from a germ called Mycobacterium tuberculosis. A large percentage of cattle in India are infected with a strain of tuberculosis called Mycobacterium bovis. Are humans capable of getting tuberculosis from cattle infected by Mycobacterium bovis? Absolutely. Through milk and beef.
One interesting discovery, after unveiling the genomes of both bacterial villains, which share 99.95% identical gene sequences, was that M. bovis came from M. tuberculosis, and not the other way around. Humans infected their cows 10-15,000 years ago and are being infected right back by them. Humans can get TB from milk in various ways: through drinking milk produced in unsanitary conditions; through infected, tubercular workers who get it from lesions in the udders of cows racked with bovine tuberculosis. A milk bucket is easily contaminated.
A tubercular worker coughing into even one bucket could contaminate thousands of gallons when his milk is poured into a larger batch. Milk is a nutrient rich liquid so it is easy for microbes to grow in it. Even if there is a ' modern' milk processing plant with cows hooked up to machines and milk being transferred for boiling by, and to, machines, there are still areas where 'foot traffic' from employees brings in microbes Tuberculosis is passed from cows to humans even in the hyper-modernized dairies of the United States.
A fifteen month old child died recently in New York of TB caused by M. bovis infection. A multiagency investigation identified 35 more cases of M. bovis infection in New York City alone. The United States requires testing of all dairy cows for bovine TB. Any cow found infected is killed. But inspite of regularly killing thousands of animals, whole herds of 300,000 cows at a time are found infected every year. In a country like Mexico which has better standards than India in keeping cattle – but only just – 17% of cattle have been found with tuberculosis.
Go and look at the average Indian dairy. It is filthy, unsanitary and overcrowded. It has to be a breeding ground for TB. Neither the owner nor the useless animal husbandry inspector ever checks cows for any disease, much less tuberculosis. One inspection which took place at the sperm producing centre in Kerala found that all the bulls—whose sperm is injected into cows all over India—had TB. Not one bull was killed. No re-inspections took place, nor were any of the cows that had been injected with the bulls' sperm inspected. Do even Amul and Mother Dairy inspect the village cows, from which they take milk, for M. bovis infections? They don't. Even if they did, would any villager agree to kill his milk producer ? No. Most cows and buffaloes in India are in filthy dung-filled sheds, standing in their own faeces for days. In cattle faeces M bovis will survive 1 – 8 weeks. Animals are probably more likely to be infected by M. bovis when they are poorly nourished or under stress. Once the Mycobacterium is ingested or inhaled, the disease may be 'silent', even to an experienced farmer or veterinarian, until the advanced stage.
Infected people or animals that appear healthy are capable of transmitting the infection. Tuberculosis lesions can affect any part of the body but generally affect the lungs and lymph nodes and the chest cavity. The normally smooth internal lining of the chest cavity may be marred by lesions. How do you make out a milch animal has TB ? A soft, chronic cough occurs once or twice at a time. In more advanced cases, there is a marked increase in the depth and rate of respiration as well as shortness of breath.
In advanced stages, animals may show weakness, weight loss, and fluctuating fever. The complicated nature of TB transmission, the resistance of the agent to disinfection, and the long period of infection prior to development of signs of disease have made bovine TB impossible to control. M. bovis is spread in a number of ways by infectious animals - in their breath, milk, discharging lesions, saliva, urine or droppings. Once in a herd, infection spreads from cow to cow by inhalation and from cows to calves via milk. People acquire TB by the same means as animals, by ingestion and inhalation. Is there any evidence that human TB comes from cow and buffalo meat and milk? The government has made a The Roadmap to Combat Zoonoses in India – a mission to combat diseases spread from humans to animals. Tuberculosis is No 1 on the list – even above rabies.
This confirms that they know the danger in milk – but will not speak openly for fear of harming the industry . All the studies done in India show vast numbers of cattle infected with TB. Even worse, a study done by AIIMS called 'Bovine tuberculosis in India: potential basis for zoonosis' did TB tests of cattle and humans, 15.7 % humans had M. tuberculosis, 26.8% of cattle had M. bovis. BUT 8.7% of humans had M.Bovis TB and 35.7% cattle had 'mixed infections' as well. The conclusion 'The detection of mixed infection with the mycobacterial pathogenic duo in humans and bovines denotes the prospect of potential transmission of these pathogens from humans to cattle (zoonosis) and vice versa (reverse zoonosis). Animals infected with M tuberculosis potentially constitute a grave public health hazard as virulent bacilli can be transmitted to humans'. Similar studies have shown the same results.
As recently as last year, seeing the increase in TB in Mumbaikars, doctors of the preventive social medicine department of Jalgaon's Ulhas Patil Medical College have asked the civic authorities to look at the cattle sheds as a source of human TB. The head of the department Dr Ashok Kale was recently called by the Maharashtra Gazetted Veterinary Association to talk about the threat of zoonotic TB. 'Animals are a source of TB virus. Milk, their excreta and breath of a TB-affected animal can spread the disease. And most of us are unaware of this,' he said. India is the largest consumer of milk in the world. And the country with the largest number of tuberculosis patients. Do you want your milk drinking child to be a TB statistic ?
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