Public health issue in India over meat-borne zoonotic diseases
Rupendra Kumar1, Deepti Sinha2
1PhD scholar, Livestock Production and Management, ICAR-NDRI, Karnal, Haryana (132001), India
2PhD scholar, Animal Genetics and Breeding, ICAR-NDRI, Karnal, Haryana (132001), India
Abstract
Meat borne zoonotic diseases always considered as an enigma for human beings mostly transmitted through the consumption of meat obtained from infected animals or the contaminated meat during handling or processing. Rampant unhygienic street slaughtering of food animals in India without adopting proper antemortem and postmortem examinations considered as important source of contamination. Butchery practices by untrained personnel further culminate the infection by throwing different carcass byproducts to the environment which not only responsible for pollution but also spread the infection to stray animals which subsequently act as potential reservoirs of disease. Meat consumers should be well aware of all meat borne zoonotic diseases. Suitable government legislation should be formulated to give a check on street butchery practices with adaptation of careful antemortem and post-mortem inspection to limit the chances of spreading infection from food animal handlers at various levels which will be helpful for providing quality meat as well as nutritional security.
keywords: Meat, meat borne zoonoses, hygiene, postmortem inspection
1 Introduction
The word ‘Zoonosis’ (Pleural: Zoonoses) was introduced by Rudolf Virchow in 1880 to include collectively the diseases shared in nature by man and animals. Later WHO in 1959 defined that Zoonoses are “those diseases and infections which are naturally transmitted between vertebrate animals and man”. The zoonotic diseases can get transmitted from animals to human being through various routes such as by direct contact with diseased animals or infected material, consumption of contaminated meat, water, and milk etc, inhalation of infectious organisms, through vectors or accidental inoculation of pathogen through breach on skin etc. The Zoonoses through meat are generally transmitted by two main modes: (i) During transportation, slaughtering, dehiding, skinning, dressing and processing of the animals and meat, infective agents are transferred from animals/meat, meat products and the equipment and instruments used in the meat production to man. (ii) Through the consumption of meat and meat products intoxicated or infected. Meat-producing animals (e.g., cattle, buffalo, sheep, goat, pigs and poultry) are the major reservoirs for many food poisoning organisms e.g., anthrax, brucellosis, tuberculosis, salmonellosis, campylobacter jejuni etc. These organisms get transferred to human being through meat and meat products. Most of the bacterial zoonotic diseases get transmitted to human being through the consumption of inadequately cooked meat e.g. salmonellosis, pasteurellosis, staphylococcus infection etc.
2 Zoonoses of bacterial origin
(a) Anthrax
Anthrax is a disease of herbivorous animals caused by Bacillus anthracis and humans incidentally acquire infection by direct inoculation of spores through breaks in the skin (cutaneous anthrax), by inhalation of spores (pulmonary anthrax), or by ingestion of contaminated meat (gastrointestinal anthrax) (Appa and Karthikeyan, 2001). In India, however, which has the largest population of livestock in the world, the disease is still endemic. A few sporadic cases and outbreaks of anthrax have occurred in India. The actual incidence of anthrax in India is not known accurately since a large number of cases go unreported and only a fraction of human cases receives medical attention in a hospital. Cases treated on site in a village are hardly brought to the notice of authorities. Hence, the incidence of anthrax in man is likely to be higher than reported in literature. Anthrax is enzootic in southern India but is less frequent to absent in the northern Indian states.
(b) Brucellosis
Brucellosis is a highly contagious zoonosis caused by ingestion of unpasteurized milk or undercooked meat from infected animals, or close contact with their secretions. Bacterial load in animal muscle tissues is low, but consumption of undercooked traditional delicacies such as liver has been implicated in human infection (Mantur and Amarnath, 2008). It primarily affects people who work with animals or animal products. Contamination of skin wounds may be a problem for persons working in slaughterhouses or meat packing plants or for veterinarians. B. abortus is the dominant species in cattle. Bovine brucellosis is widespread in India and appears to be on the increase in recent times, perhaps due to increased trade and rapid movement of livestock (Renuka radhya et al., 2002). Several published reports including recent ones indicate that human brucellosis is quiet common disease in India (Mantur and Amarnath, 2008). It causes mastitis, abortion (7 to 9 month) and sterility in animals.
(c) Leptospirosis (Haemorrhagic jaundice)
Leptospirosis is caused by the spirochaete bacteria belonging to genus Leptospira of family Leptospiraceae under the class Spirochaetes. Natural reservoirs of infection are rats and Leptospira spp. is shed in its urine. The infection may take place from urine of infected animals, by inhalation and ingestion and through skin cut and abrasions. Rats, mice, and moles are important primary hosts but animals like dogs, cows, sheep etc are also responsible for disease transmission. Humans can only become infected through contact with food, water, or soil that is contaminated with urine from these infected animals. It causes septicemia, fever, haemoglobinuria, jaundice, infertility and abortion in most animals. The human leptospirosis is also known as Weil’s disease. In humans, the disease is characterized by variety of symptoms, including high fever, vomiting, jaundice (yellow skin and eyes), red eyes, headache, chills, muscle aches, abdominal pain, diarrhoea, rash etc. (Routray et al., 2018). Leptospirosis is reported to be of endemic importance from many states of India.
(d) Listeriosis
It is caused by Listeria monocytogenes from intestines of domestic animals and man. There has been an increase in the sporadic cases of Listeriosis in the country (Janakiraman, 2008). The mode of transmission is through direct contact with infective material, aborted foetus and contaminated soil. Infection may occur in man by eating infected meat. The organism has also been isolated from faeces of abattoir workers. In animals the disease takes the form of encephalitis or abortion. In human, transmission is mainly through milk products, but contaminated chilled meat could also be a cause of illness. Both in humans and animals, listeriosis may be associated with symptoms including gastroenteritis, sepsis, and infections of the CNS (meningitis or myelitis), and also may lead to miscarriage (Dreyer et al., 2015).
(e) Salmonellosis
It is a disease caused by Salmonella spp. in animal and man. S.typhi and S.paratyphi A, B, and C are pathogenic for humans, but their presence in animals is asymptomatic (Chlebicz et al.,2018). Salmonella typhi cause typhoid in human and Salmonella gallinarum cause fowl typhoid. Salmonella can exist in faeces and pastures. They grow well in meat food. Salmonella food poisoning occurs due to improperly cooked or thawed meat or poultry, infected food, cross infections from person to person through excreted Salmonella. Infected chicken, turkey and eggs are the main sources of food poisoning outbreaks. Salmonella enteritidis and Salmonella typhimurium are main serotypes. Salmonella enters food directly at slaughter from animal excreta transferred to food by hands, flies etc.
(f) Tuberculosis
It is caused by Mycobacterium tuberculosis. Cattle, sheep, pigs, goat and poultry are susceptible to tuberculosis. Tuberculosis remains endemic in developing countries like India that lack disease control programmes because of the associated economic costs and social barriers to test and cull strategies (Srinivasan et al.,2018). It has been estimated that zoonotic transmission of M. bovisis responsible for 10–15% of new human TB cases in developing countries (Ashford et al., 2001). The disease in humans primarily occurs through close contact with infected cattle or consumption of improperly cooked beef and drinking of unpasteurized milk and milk products. People in specific occupations such as veterinarians, farmers, and abattoir workers are considered to be more at risk. Animals affected with generalised tuberculosis in animals are rejected for food whereas in localized conditions, the lesions are carefully removed and carcass, if suitable is passed for food.
3 Meat borne viral Zoonotic diseases
(a) Contagious Pulmonary Dermatitis (CPD)
It is also called as contagious ecthyma or ‘Orf’. CPD is caused by a Parapoxvirus and found in sheep and goat. Lesions are seen on lips of lamb, tongue, palate, lungs and digestive tract. Orf is commonly seen in butchers, abattoir workers and meat handlers.
(b) Norovirus infection
Norovirus genus comprising those viruses capable of infecting humans, cattle, pigs, and mice. Zoonotic transfer could occur through contact with animals or indirectly through the food chain. Noroviruses (NoVs) are being regarded as an important cause of nonbacterial gastroenteritis in human. Spread of these viruses might also be associated with person-to-person contact, fomites, and food. Recently researchers identified GIL-4 strains of Norovirus in raw pork in retail meat shop which considered its important for zoonotic spread and highlights the importance of proper handling and cooking of various meat products before consumption to limit the infection. Presence of virus in farm animals highlight the possibility that a new recombinant highly virulent swine/human or bovine/human Noro virus could emerge in future which should be properly investigated in time to come (Mattison et al., 2007).
(c ) Hepatitis E Virus infection
Hepatitis E virus (HEV) is an RNA virus in the family Hepeviridae, genus Orthohepevirus. Hepatitis E virus is an emerging zoonotic pathogen transmitted to humans through consumption of contaminated meat products, through faeces and direct contact with infected animals. This infection in humans cause acute hepatitis with mortality rate from 0.5 to 3% in young adults. Pigs are the most important animal reservoir for genotypes capable of infecting people. Most pigs acquire HEV via the fecal-oral route. Rabbits may serve as a potential zoonotic reservoir for human hepatitis E virus infection also.
4 Meat borne zoonoses of parasitic origin
(a)Taeniasis
Human taeniasis is a zoonotic condition resulting from infection with the adult stages of Taenia saginata (beef tapeworm), Taenia solium (pork tapeworm) or Taenia asiatica (Asian tapeworm) (Okello et al., 2017). The larval stage of T. solium is Cysticercus cellulosae and that of T. saginata is Cysticerusbovis which are seen in the musculature of pig and cattle respectively and the adult tapeworms are seen in human being. Infection enters into human body through consumption of raw or inadequately cooked beef or pork which contains larval stages of the worm. Taeniasis results in gastrointestinal disorder and nervous symptoms in human being. The tapeworm infection can be prevented by thorough cooking of the meat, refrigeration of meat for at least 21 days or freezing at -95°C for at least 6 days and proper sanitation and meat inspection.
(b)Trichinosis
Trichinosis also known as trichinellosis is a meat borne zoonotic disease caused by Trichinella larvae present in the infected meat. Pigs are the major source of infection to humans. The symptoms of trichinellosis in humans may vary from self-limiting disease to a severe disease terminating in death. On the other hand, animals rarely suffer from the disease. The disease is still largely under recognised in medical domain masking the true picture of the disease status in the country (Kumar et al., 2017). Man gets infection through the consumption of raw or undercooked or improperly cured meat. The larval stages are seen in the muscles of man.
(c)Hydatidosis
In India, hydatid disease is common in most of the states of which Andhra Pradesh and Tamil Nadu predominate. The causative parasite is Echinococcus granulosus that dwells in the small intestine of canids as an adult. Larval stage of this worm is found in human being, cattle and sheep. Larva produces cyst in the visceral organs. This cyst is known as hydatid cyst. Intestinal and Muscular forms are seen in human. Usually lungs and liver are affected. Cranial cysts are also found in some cases. The symptoms may include pain, coughing and some cases where cysts get ruptured somehow fatal anaphylaxis is observed. This disease can be controlled by taking adequate hygienic measures and consuming thoroughly cooked meat.
(d)Toxoplasmosis
This is caused by Toxoplasma gondi. In India, T. gondii’s prevalence in animals has been abundantly established by sero epidemiology, association with abortions in goats and sheep, and isolation of faecal oocysts from cat (Chhabra and Singla, 2009). The infection reaches human through inadequately cooked meat or food containing infective cysts and to the infants through the mother who get infection during pregnancy.
(e)Sarcocystosis
Man gets infection through ingestion of partially cooked sarcocystis contaminated meat. Man acts as intermediate host for species found in pig and cattle. Symptoms in human beings are diarrhoea, transient nausea and abdominal pain. This disease produces fever, anorexia and muscle spasm, diarrhoea, weakness and anaemia in animals.
5 Prevention and control of meat borne zoonotic diseases
Foodborne illness remains a serious problem particularly in developing countries like India. Meat is the major source of foodborne illness worldwide. As most the food animals in our country are being slaughtered at butcheries without following any antemortem as well as postmortem inspection of the animals during slaughter process, the prevalence of meat borne zoonotic diseases is more. So, more focus should be given on the following aspects for effective prevention and control of meat borne zoonotic diseases in our country.
- Monitoring of meat borne pathogens and emerging zoonoses should be done.
- Rapid diagnostic tests applicable under field conditions should be developed.
- Rapid detection or isolation techniques for online testing during production or processing itself for meat quality control should be developed.
- Development /Standardization of quality control tests for detection of pathogens/ toxins in meat and meat products using enzymes, endotoxins or molecular biology techniques should be done.
- Focus should be given on development of vaccines or diagnostics against zoonotic infestations and infections e.g., Salmonella, Listeria, Brucella, EHEC etc.
- Hygienic slaughter and meat processing technique should be followed.
- Quality microbiological specifications for meat and meat products should be laid down by the competent authority.
- HACCP should be strictly followed at each and every step of the food production system i.e from point of production to the point of consumption by the consumers.
- Environmental pollution can be prevented by adopting properdisposal method for non or slow biodegradable wastes and condemned carcass parts.
6 Conclusion
In conclusion, meat borne zoonotic diseases are not uncommon in India but remains largely underreported and under diagnosed due to lack of awareness about the diseases. Lack of strict meat inspection, consumption of undercooked meat and poor epidemiological data has resulted in the recent outbreaks of meat borne zoonotic diseases in our country. So, Public awareness and good meat hygiene practices, regular monitoring and surveillance of the diseases are important components of prevention of these diseases.
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