An Analysis of the Main Meat-Borne Bacterial Zoonoses
Chirag Singh1 and Shikha Tamta2
1Chirag Singh, Department of livestock products technology, College of veterinary and animal science Sardar Vallabhbhai Patel University of Agriculture and Technology, Meerut, U.P,250110.
2 Shikha Tamta, Department of veterinary public health and epidemiology, IIVER, bahu, Akbarpur, Rohtak, Haryana,124001.
Introduction
Zoonosis can be defined as transmission of infectious diseases naturally between humans and animals either domestic or wild. With the emerging concept of one-health, zoonotic diseases are of keen interest for the scientists and doctors as majority of the pathogens which infect humans are somewhere of zoonotic origin. Out of total 1,415 species of infectious disease-causing organisms found to be pathogenic to humans, which includes 217 viruses and prions, 538 bacteria and rickettsia, 66 protozoa, 287 helminths and 307 fungi. Out of all the potential disease-causing organisms mostly of them have a zoonotic origin, and food products obtain specially of animals are considered as major carrier of food-borne infections. In context of food borne diseases bacteria are the most responsible organisms causing 66% diseases in humans followed by chemicals (26%) and virus (4%) are the main causes of food-borne diseases. Meat being a rich source of nutrition and highly partible food products makes it vulnerable to microbial growth as it contains all the necessary ingredients to flourish almost all kinds of organisms. Meat itself and meat products have been found responsible for many diseases and outbreak, therefore it is utmost needed that handling of meat is equally important apart from knowing the back history of animal from which the meat has been produced. Alive animal’s muscle tissues are generally free from pathogens if it is not diseases. Whereas, following slaughtering and carcass forming, muscle undergo many changes to form into meat which could easily get contaminated. According to the WHO, in developed countries about 30% of the population get infected from food-borne diseases every year, and up to 2 million deaths are estimated per year in developing countries.
Pathogens which are responsible for transmitting diseases to humans from meat are of different origin, this chapter tried to concise most of the major causes of zoonosis through meat.
Zoonotic agents responsible for transmission of diseases in humans through meat handling
- Bacterial transmission
Almost all bacterial diseases in animals are having some affinity to cause diseases in humans. Therefore, this category of pathogen is utmost important from human health point of view. Meat borne infections are caused by the entrance of pathogenic bacteria contaminating meat and meat products into the body, and the reaction of the body tissues to their presence.
Campylobacteriosis: campylobacteriosis, is caused by Campylobacter bacteria. The incubation period of disease is between 2 and 11 days with an average of 3–5 days. Animals and birds infected with campylobacter show no sign of illness which makes the disease even more complicated as sometimes during slaughter inspection diseased animals are passed unnoticed. Campylobacter sometimes resides in the intestines, liver, and other organs of animals like muscles, from where it gets transfer to humans when an animal is slaughtered. C. jejuni and C. coli commonly causes illness in humans characterized by fever; abdominal pain (abdominal pain is associated with backache and possible mortality); foul-smelling and watery diarrhoea, dysentery and mucous in faeces, vomiting and nausea. Along with campylobacters and salmonella also causes similar symptoms like gastroenteritis in humans. This disease can also occur in people working in close proximity with animals like workers of poultry processing plants or broiler raising farms.
Yersiniosis: Yersiniosis is a zoonotic disease often caused by eating raw or measly cooked pork contaminated with Yersinia enterocolitica bacteria. Centre for disease control USA estimates Y. enterocolitica causes almost 117,000 illnesses, 640 hospitalizations, and 35 deaths in the United States alone every year. Y. enterocolitica harbours in the intestinal flora of red meat animals, especially pigs. It also resides in the nasopharynx and in the tonsils of pigs. This bacterium has a huge potential to infect wide range of food like beef, lamb, seafood, pork, milk, vegetables and even vacuum-packed meat. Some serotypes of Y. enterocolitica infect humans via contaminated foods, milk or water causing gastroenteritis and sometimes persistent arthritis. Abattoir personals specially working in pig slaughter houses are consider to be at high risk. Children are at higher risk of infection compared to adults, symptoms are generally restricted to abdomen and sometimes confused with appendicitis. In chronic cases skin reaction may occur in association with joint pain.
Salmonellosis: Salmonellosis is a disease caused by salmonella a common bacterial that usually affects the intestinal tract and produce symptoms similar to stomach flu. This bacterium usually resides in animal and human intestines and is shed out through faeces. Human infection usually caused by consuming raw or less cooked meat, poultry, and eggs or egg products or by drinking unpasteurized milk. Incubation period od the disease can be from 6 hours to 6 days. S. typhimurium, S. infantis, S. dublin, S. enteritidis are some of the common species which cause infection and disease in humans. Contamination of meat and meat products with infected meat or touch of infected food handlers is one another cause of infection apart from eating infected food with salmonella itself (Heredia and García (2018); PHAC, 2020). Therefore, maintaining good hygiene and eating properly cooked meat can reduce the chance of disease.
Escherichia coli (E. coli): is a bacterium which normally resides in the intestine of humans and animals and help in digestion and competitive inhibition of pathogenic bacteria growth. Symptoms usually occur 3 to 4 days after a person comes in contact with E. coli O157. Humans get infections usually from eating raw or undercooked beef or raw milk infected with the bacteria. In saviour cases symptoms like bloody diarrhoea and even kidney failure (haemolytic uraemic syndrome) can occur which can be fatal.
Brucellosis: A foodborne and occupational zoonotic disease, caused by the bacteria genus Brucella. Human brucellosis is a complex, life-threatening disease and characterised by the clinical problems such as peripheral arthritis, bronchopneumonia, epididymitis, orchitis, hepatic abscesses, sacroiliitis, osteomyelitis, spondylitis, meningitis, encephalitis, cardiovascular complications, and prostatitis. The transmission in humans occurs through ingestion of infected milk from mothers to breastfed babies and eating undercooked meat infected with brucella or by contamination of clean meat by infected hands or utensils. The transmission of Brucella also happens through mucous membranes or skin wounds, following direct contact with urine, vaginal discharges, blood, tissues, placenta, aborted foetuses, and through inhalation of airborne agents in an atmosphere. In humans the disease can be serious and persist for many years as a recurring fever.
Tuberculosis: M. bovis and M. avium are mostly responsible for infections in red meat animals and poultry respectively. Zoonotic transmission of M. bovis from cattle to humans was identified more than a century ago, but less frequently is it acknowledged that Mycobacterium tuberculosis complex (MTBC) species are transmitted from humans to cattle. The transmission of MTBC from humans to cattle has been documented in numerous publications over the past ten years. Both of these species as well as M. tuberculosis can infect humans. Additionally, M. bovis infection can be contracted through direct skin-to-skin contact with a wound, such as during slaughter or hunting, or by inhaling the bacteria present in animal breathed air. M. bovis can be transmitted directly from person to person when those with the disease reached to the level of lungs and bacteria secrets in cough or sneeze, however direct airborne transmission from animals to humans is regarded to be uncommon. Lesions are most common in the lymph nodes in the neck and hence this is the area most thoroughly examined during meat inspection. Although lymph nodes with tuberculosis may be mistaken for those with other bacterial infections, humans can contract the disease from animals by ingesting the bacteria or by consuming contaminated meat or milk.
Clostridium perfringens: meat borne intoxication: One of the most frequent causes of foodborne sickness is the bacteria Clostridium perfringens. According to the CDC, these bacteria are responsible for around 1 million illnesses in the US each year. Meat, poultry, gravies, and other items cooked in big batches and stored at an inappropriate temperature are also potential sources of C. perfringens contamination. These bacteria produce spores, which function as a kind of barrier and aid in the bacteria’s survival. When food is stored at an inappropriate temperature (between 40°F and 140°F), bacteria can grow and proliferate rapidly. The bacterium may release a toxin (poison) that causes diarrhoea after being ingested. Intoxication is caused by the ingestion of food containing large numbers of vegetative cells of enterotoxigenic C. perfringens type A and some type C and D strains are infective to humans. It multiplies in the intestine and following sporulation releasing C. perfringens enterotoxin (CPE) which causes illness. After consuming contaminated food, most persons with C. perfringens infection experience diarrhoea and stomach pains within 6 to 24 hours. Typically, the disease starts off quickly and lasts for less than 24 hours. Typically, this illness does not result in fever, vomiting, or the ability to spread from one person to another.
Q fever: Animals, including cattle and, less frequently, sheep and goats, are typically infected with Coxiella burnetii while still in the subclinical stage. The organism excretes in the urine and faeces and localises in the mammary glands, lymph nodes, and placenta without producing visible symptoms. Dust or aerosols, foetal membrane and associated tissues, faeces, or urine can all directly infect humans in a way similar to chlamydiosis. Additionally, because C. burnetii can excrete in milk, infection can result from consuming raw milk or from severing the mammary gland in an abattoir. Human infections are usually asymptomatic, but severe and persistent infections can result in endocarditis, hepatitis, and even mortality, particularly in immune-compromised individuals.
Erysipelas: Erysipelothrix rhusiopathiae is a facultative, non-spore-forming, non-acid-fast, small, Gram-positive bacillus. Late in the nineteenth century, the organism was identified for the first time as a human disease. Since then, three different types of human sickness have been identified. These include erysipeloid, a generalised cutaneous form, a localised cutaneous lesion form, and a septicaemic type that is frequently linked to endocarditis. Many mammals and poultry, and even fish, can suffer from erysipelas, characterised by inflamed areas on the skin. Pigs are most commonly infected. Humans develop skin lesions following direct contact with infected animals. Meat or farm workers are most likely to be infected, although these organisms have been isolated from retail meat, particularly pork and poultry.
