Need for Tuberculosis control in animals- for Tuberculosis eliminationtext_fields
Recently, the sudden death of several animals in quick succession at the Zoological Park, Thiruvananthapuram in the state of Kerala had raised concerns over the possible presence of Zoonotic TB. After the results of the samples of the internal organs of the animals sent to the State Institute for Animal Diseases (SIAD) came back positive for the presence of tuberculosis, the chief investigative officer of SIAD issued orders to the officials of the zoological park, Thiruvananthapuram to be extremely cautious, as there were high chances of it being transmitted to other animals as well as to humans. The minister for Animal Husbandry Mrs J Chinchu Rani had also expressed concerns and advised caution over the same. As per the news published, in January 2023, 126 animals including 54 blackbucks, 42 spotted deer, 3 iguanas, wild buffaloes, 24 birds of various species, 2 special types of parrots and an anaconda have died in the past year at the zoo in Thiruvananthapuram district of Kerala.
Currently, about 60 per cent of infectious diseases affecting humans and 75 per cent of emerging zoonotic diseases are animal-borne diseases. Although this disease may not affect animals as such, it can prove to be fatal for humans. Yearly 250 crores of humans get infected by zoonotic diseases out of which 27 lakh people succumb to it. Globally 15.8% of deaths are reported to be due to zoonotic diseases, whereas for undeveloped countries it is as high as 43.7%. The most common among them are plague, flu, AIDS, COVID, SARS, MERS, Ebola, NIPAH etc to name some. Apart from these, there are vector-borne diseases as well.
Types of Zoonotic TBs
Mycobacterium bovis or bovine tuberculosis is the name of the bacteria which causes Tb in animals. Having adequate knowledge about the symptoms can help in controlling the spread of the disease. Once detected, precautions should be taken to control its spread. As per studies, in developing countries like India, 10% of all Tb is carried by the mycobacterium bovis. The main disease vector being cattle along with dogs, swine and other mammals.
Microbacterium Avium Complex ( MAC) is yet another strain which is spread by birds as well as swine, sheep and other mammals. Although rare, it can spread to other humans as well. The disease is caused by bacteria called Mycobacterium avium paratuberculosis.
* Statistics of Zoonotic TB
According to the WHO report of 2017, more than 140,000 people get infected every year and 12,000 people lose their lives due to zoonotic Tb. In India, according to a study in 2018, the prevalence of zoonotic Tb was found to be 7.3%. Yet another study reported more than 2 crores of cattle as being affected by Mycobacterium Bovis.
Bovine Tb and its Transmission
Bovine TB, which affects cattle and other domestic animals, is also caused by bacteria of the genus Mycobacterium. But many people are ignorant about Bovine TB, which is caused by the bacterium Mycobacterium bovis and is transmitted from animals to humans. Bovine TB is a zoonotic disease because it can spread from animals to humans. The following are the symptoms of Bovine Tb: fatigue, wasting of body/losing weight, not taking feed, respiratory issues, inflammation of veins, intermittent cough/fever and reduced milk production. An infected animal may show signs of fatigue, lethargy, loss of appetite, persistent cough, diarrhoea, and enlarged lymph nodes.
Bovine Tb is spread mainly through infected cattle by direct contact with them or by ingesting food which is contaminated with the pathogen, infection by inhalation/ coming into contact with the excreta, urine, phlegm and blood of the infected animals or by inhaling secretions when infected animals cough. Once the bacteria enter the body they can remain dormant for several years without any symptoms and at the same time transmit it to others as well. If inhaled, the germs multiply in the lungs and get transformed into nodules. As the disease progresses, it can spread to the liver, kidneys, and spleen. It can also spread from infected feed-water bowls, pastures and water bodies. The main mode of transmission of the disease to humans is through the consumption of undercooked milk, milk products and meat from infected cattle.
Detecting of Tb in animalsDiagnosing Tb in animals is difficult in the initial stages since it might manifest without many symptoms. Tuberculin Skin Testing is one test which can aid in the diagnosis. Along with this, culture, histopathology molecular diagnosis by polymerase chain reaction, and ELISA can also be done for diagnosing purposes. It requires a time period of around 8 weeks for the results. The treatment of TB in animals though similar to humans is costly in terms of time and money and hence is not considered very practical.
Prevention of Bovine Tb
Scientific meat inspection in slaughterhouses or otherwise known as post-mortem inspection is one way of detecting disease and thereby limiting or preventing disease transmission. Safely discarding the meat which is found to be infected, using only pasteurized milk and milk products, avoiding the addition of raw milk for preparing food like shakes, using only well-cooked meat etc. can go a long way in preventing the spread of bovine Tb. Relocating infected animals and ensuring that the animals brought from other states are free of tuberculosis and conducting post-mortems on dead animals are other ways by which the spread of bovine Tb can be contained. Once tuberculosis is suspected, always seek advice from the nearest veterinarian.
As Bovine TB is similar to ordinary TB, the existing DOTS (Directly Observed Therapy Shortcourse) scheme is sufficient for treatment. However, Pyrazinamide, one of the four drugs in the DOTS program, is not resistant to Mycobacterium bovis. It can be effectively treated and cured with other drugs.
TB from Humans to Animals
Bovine Tb is not restricted to cattle, it can affect all mammals, especially pets at home. Man, non-human primates, cattle, dogs swine and psittacines (parrots) too can get infected. In 2019 there was a report of 3 wild elephants being infected with the bovine Tb in the Muthanga forest, Wayanad which raised quite a concern. Although the presence of Tb was found to be in elephants earlier, its presence in wild elephants has been viewed as a grave problem since it points to the effect of human encroachment into the habitat of wild elephants. Similar observations have been made in Sri Lanka as well. Signs of disease in elephants include lethargy, fatigue and weight loss. The disease is mostly seen in elephants between 18-20 years of age. The disease was also transmitted to the elephants from mahouts who had tuberculosis.
Paratuberculosis Pathogen and its Symptoms
Paratuberculosis bacteria can survive adverse weather conditions and disinfectants and can survive in contaminated environments for longer periods. Other animals are mainly infected through contaminated feed and water. Drinking the milk of infected cows and goats can also infect their young. Infection can also be spread through the breeding process and it may affect their natural immunity as well.
Goats and cows show gradual emaciation and weight loss. It has a gradual onset with prolonged and severe diarrhoea in cattle and intermittent diarrhoea in goats. Persistence of symptoms such as weight loss and diarrhoea despite treatment with antibiotics and dewormers and gradual decrease in milk production, hair loss and discolouration of mane, swelling in jaw, anaemia, fever, fatigue, lethargy, the birth of babies with low birth weight and stunted growth, decreased fertility and infertility are some of the symptoms associated with the pathogen. Paratuberculosis can be suspected if these symptoms are observed in cows and goats. As the symptoms are similar to various diseases, scientific diagnosis requires advanced methods such as PCR and ELISA)
Paratuberculosis- No treatment is effective
Currently, there are no effective methods to treat or control paratuberculosis. Once infected with this, the germs break down and multiply in the animal's body and get out through excreta and body fluids. Since paratuberculosis bacteria also can survive in the soil for long periods, current guidelines for disease control require that infected animals be identified through scientific testing and destroyed or relocated and cared for separately. Since the disease is incurable and can spread to humans and other animals, infected animals need to be isolated and cared for a long time. The World Health Organization for Animal Health recommends that the most effective control method is euthanizing and safely disposing of animals diagnosed with paratuberculosis.
The National Goat Research Centre at Makhdoom, Uttar Pradesh under the Indian Council of Agricultural Research has developed an effective vaccine to prevent paratuberculosis disease. Lambs and calves can be vaccinated after three months of age. A single dose of the vaccine can provide life-long immunity. The vaccine can be used not only to prevent disease but also to prevent disease in infected animals. Biovet Limited, a vaccine manufacturing company, manufactures and distributes paratuberculosis vaccines on a commercial basis.
Livestock sector is the livelihood of 20.5 million people
In India, about 20.5 million people in India depend on the livestock sector for their livelihood. Livestock accounts for 16 per cent of the income of small farmers and 14 per cent of the income of rural farmers. The sector employs 8.8 per cent of India's population and about 1.69 per cent of land is used for all forms of livestock rearing. According to the 20th Livestock Census (2019), the number of cattle in the country is 535.78 million. With India continuing to be the largest producer of milk with a contribution of 20.17% to the world’s total milk production, livestock rearing and related sectors, which are the livelihood of many people, will have to face a huge social and economic setback if diseases like Bovine TB continue to be a concern. Strong awareness and prevention measures are strongly recommended in this area.
It is reassuring that the Animal Welfare Department in Kerala with the help of other local government bodies concerned is implementing various programs for the complete elimination of infectious diseases. Foot and mouth disease eradication programme, Rabies-free Kerala, vaccination program and ASCAD poultry vaccination program are some of the programs which are being implemented systematically.
Importance of One Health
One Health is a universally accepted concept for raising the standard of living healthy in the world. The goal of the project is to realize that the environment includes humans, animals and plants, and the mutual understanding between them, to achieve suitable health conditions for all living beings. This is a collaborative approach to health while recognizing the importance of working together on the interface of different sectors concerning humans and animals living in a shared environment. The WHO defines One Health as “an approach to designing and implementing programmes, policies, legislation and research in which multiple sectors communicate and work together to achieve better public health outcome”. Thus “One Health” is an integrated and unified approach to balance and optimize the health of people, animals and the environment.
As animal health and human health are interrelated, the theory of One world- One health is very relevant. Today the world can be divided into two-those who got affected by COVID and those who did not. The takeaway is that many future epidemics may be zoonotic. Hence the importance of One Health.
It is said that SARS and Covid originated from the Chinese wet markets. Climate change also creates favourable conditions for the emergence and spread of new diseases. Taking all this into account, it is extremely important to take cognizance of the health of not only humans but to focus on an integrated and interlinked approach emphasizing animals as well as the ecosystem and the environment. This is the 'One Health' approach. But the reality is that there is currently no single health approach to TB control in Kerala, which involves both public health experts and animal health experts.
* Need of the Hour- Intervention and Care
In the goal of total elimination of Tb by 2025, the state of Kerala looks promising. However, it has its challenges also. It is surprising to note that to date no action has been taken to address or curb the spread of Tb from animals to humans. When Tb can spread from animals to humans it is worth noting that no new studies have been conducted in this regard at the national and state levels suggesting that the authorities should be more vigilant in this regard.
When it comes to animal husbandry and management we still do not follow any scientific methods. Most of the present slaughterhouses still follow primitive methods for the same. When done scientifically it requires that we do the antemortem as well as post-mortem tests to rule out the possibility of infectious diseases. This is not followed by the majority of the slaughterhouses in the state. This can result in people getting access to contaminated meat. Apart from this, it can also result in an increased risk of disease transmission to those who get involved in the slaughter. The meat of infected cattle and dead animals is also being distributed across the borders to many states including Kerala at a cheap price. When it comes to Kerala, there has been a widespread complaint that the food safety department is not taking effective measures despite these serious cases being caught with evidence. These are called tsunami meat and can cause other diseases and even death.
With Tb in animals becoming a concern, there is a strong demand that testing should be done on a regular and strict basis. Today most of the meat being transported to Kerala is being done in small thermocol boxes with no proper refrigeration system in place. Bacteria such as E.coli, Salmonella, Listeria, Staphylococcus, Clostridium and Campylobacter that form in aged meat are extremely dangerous. It is to be noted that of the 3.5 crores of Kerala, almost 90% are non –vegetarians. Around 21 lakhs of cattle, every year are consumed by the state of Kerala only. The certificates of veterinary doctors which are to be shown at the check post are allegedly procured without examination.
Further, the Food Safety Department does not have a system at the border check-posts to check the milk and milk products brought to Kerala from other states. The dairy department’s predicament is that although it inspects the milk it does not have the authority to take action against the culprits. In this situation, there should be measures by the Animal Husbandry Department to create awareness about paratuberculosis disease and information about its vaccine.
"Beef in Kerala comes from animals brought for slaughter from outside the state, ie from Andhra Pradesh, Karnataka and Tamil Nadu. These animals are slaughtered on roadsides in unsanitary surroundings. Most slaughterhouses slaughter and hanging animals in open, unsanitary conditions for the public to see. It is a fact that waste and waste management activities are not effectively in place. Biogas plants have been installed in a few units for waste treatment but they are non-functional due to a lack of timely maintenance and lack of expert supervision. This type of meat production chain leads to public health problems and has serious impacts on animal welfare, food safety, occupational health, environment and sanitation- report of State Planning Board's Financial Review 2021.
Today routine testing for the presence of Tb does not help in distinguishing among the various types of bacteria. It only confirms the presence of Tb. The culture test is costly in terms of time and the molecular tests come at a high cost in terms of price. Hence it is difficult to determine the extent and spread of mycobacterium bovis. Hence awareness programs about this must be done with regard to this.
Diseases transmitted from animals to humans can be prevented only with the joint efforts of veterinarians and public health experts. The fact is that there are currently no effective collective plans for bovine Tb at the national or state level. Steps should be taken to educate farmers and people who are likely to be in direct contact with livestock about disease control and ways of transmission needed for the movement towards total tuberculosis elimination.
*WHO’S 10 priorities for zoonotic TB
The World Health Organization (WHO), the World Organisation for Animal Health (OIE), the Food and Agriculture Organization of the UN (FAO) and the International Union Against Tuberculosis and Lung Disease (The Union) launched the first-ever roadmap for tackling zoonotic TB in October 2017. The roadmap is centred on a One Health approach, recognising the interdependence of human and animal health sectors to address the major health and economic impact of this disease. It articulates clear immediate actions that all stakeholders can take to address this issue across different sectors and disciplines, and defines milestones for the short- and medium-term. The roadmap calls for concerted action from government agencies, donors, academia, non-governmental organizations and private stakeholders across political, financial and technical levels. Ten priorities for action are defined, which will also bring substantial benefits for the control of other zoonotic and foodborne diseases:
* Improve the scientific evidence base
1. Systematically survey, collect, analyse and report better quality data on the incidence of zoonotic
TB in people, and improve surveillance and reporting of bovine TB in livestock and wildlife.
2. Expand the availability of appropriate diagnostic tools and capacity for testing to identify and characterize zoonotic TB in people.
3. Identify and address research gaps in zoonotic and bovine TB, including epidemiology, diagnostic tools, vaccines, effective patient treatment regimens, health systems and interventions coordinated with veterinary services.
Reduce transmission at the animal-human interface
4. Develop strategies to improve food safety.
5. Develop the capacity of the animal health sector to reduce the prevalence of TB in livestock.
6. Identify key populations and risk pathways for transmission of zoonotic TB.
Strengthen intersectoral and collaborative approaches
7. Increase awareness of zoonotic TB, engage the key public and private stakeholders and establish effective intersectoral collaboration.
8. Develop and implement policies and guidelines for the prevention, surveillance, diagnosis, and treatment of zoonotic TB, in line with intergovernmental standards where relevant.
9. Identify opportunities for community-tailored interventions that jointly address human and animal health.
10. Develop an investment case to advocate for political commitment and funding to address zoonotic TB across sectors at the global, regional and national levels.
* Zoonotic tb must be prioritized in the global health agenda
The UN Sustainable Development Goals (SDGs) emphasise the importance of multidisciplinary approaches to improving health. In the context of the SDGs, WHO’s End TB strategy calls for the diagnosis and treatment of every TB case. This must include people affected by zoonotic TB. Zoonotic TB in people cannot be fully addressed without controlling bovine TB in animals and improving food safety. Through a One Health approach, together we can save lives and secure livelihoods.
-Dr.Muhammed Asif M. Veterinary Surgeon, Veterinary Dispensary, Muliyar, Kasaragod
-Dr.Sabir M C (Senior Consultant Pulmonology)
-World Health Organization (WHO). https://www.who.int
-Economic Review 2021, State Planning Board, Thiruvananthapuram, Kerala