Zoonoses That Pass To Humans Via Food

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What is listeriosis?
Listeriosis is a bacterial infection caused by the bacterium Listeria monocytogenes. Until several years ago it was thought that this bacteria only infected animals but it is now accepted that humans are also at risk from this disease. While many bacteria are generally seen to infect specific locations within the human body, Listeria may infect many different locations, such as the brain or the spinal cord membranes or the bloodstream.

Classification:
L. monocytogenes is a gram positive, non-spore forming, motile, facultatively anaerobic, rod shaped bacterium. It is catalase positive, oxidase negative, and expresses a Beta hemolysin which causes destruction of red blood cells. This bacterium exhibits characteristic tumbling motility when viewed with light microscopy. [6] Although L. monocytogenes is actively motile by means of peritrichous flagella at room temperature (20-25C), the organism does not synthesize flagella at body temperatures (37C). [7]

Who gets listeriosis?
Anyone can get this disease, but those at highest risk for serious illness from this bacterium are newborns, the elderly, people with weakened immune systems, and pregnant women. Healthy adults and children occasionally get infected with Listeria, but they rarely become seriously ill. Listeria Monocytogenes is classified as an intracellular paracite. This means that it invades and lives within cells of the body thereby managing to evade the body’s immune system. Infection by as few as 1000 individual bacteria is considered enough for the disease to take hold. When listeric meningitis occurs, the overall mortality may reach 70%; from septicemia 50%, from perinatal/neonatal infections greater than 80%. In infections during pregnancy, the mother usually survives.

When do Listeria infections occur?
Infections occur throughout the year. Although most cases occur sporadically, food-borne outbreaks of this disease do frequently occur. Poor food hygiene and poor personal hygiene conditions are responsible for many of the recently recorded outbrakes.

How is listeriosis spread?
Listeria bacteria are widely distributed in nature and can be found both in water and soil. Infected animals may also serve as sources of contamination. Unlike other organisms, Listeria can be spread through several different methods. Ingestion or food-borne transmission of the organism, such as through the ingestion of unpasteurized milk or by the eating of contaminated vegetables, is often a source of many cases. In newborn infections, the organism can be transmitted from mother to fetus in utero, or directly to the fetus at the time of birth through the contact of the fetus’ blood supply with that of the mothers. Direct contact with the organism can cause lesions on the skin.

What are the symptoms of listeriosis?
Because listeriosis can affect many different parts of the body, the symptoms vary. For meningoencephalitis, the onset can be sudden with fever, intense headache, nausea, vomiting and signs of meningeal irritation. In other body locations, various types of lesions at the site of infection are the primary symptom. In most cases, Listeria infection causes fever and influenza-like symptoms resembling a host of other illnesses.

How soon after exposure do symptoms of listeriosis appear?
Listeriosis has an extremely variable incubation period. It can range from 3 to seventy days, but symptoms usually will typically appear within a month of infection.

How is listeriosis diagnosed?
Specific laboratory tests are the only way to effectively identify this disease. Since many cases may be mild, the disease may be much more common than is realized.

Are there any unusual features of listeriosis?
Listeria infections are a significant risk for pregnant women, who may not experience obvious symptoms. Infection of the fetus can occur before delivery and can cause abortion as early as the second month of pregnancy, but more often in the fifth and six months. An infection later in pregnancy may cause exposure during birth, sometimes resulting in infection of the newborn child which may be fatal.

Does past infection with Listeria make a person immune?
Past infection does not appear to produce immunity.

What is the treatment for Listeria infection?
Several antibiotics are effective against this organism. Ampicillin, either on it’s own or in combination with other types of antibiotics, is frequently used.

What can be done to prevent the spread of Listeriosis?
Since the organism is widly distributed throughout nature, basic sanitary measures such as only using pasteurized dairy products, by only eating cooked meats and washing hands thoroughly prior to the preparation of foods offer the best protection against infection by this disease.

In addition, the following recommendations are for persons who are categorized to be at high risk of infection, such as pregnant women, the elderly and persons with compromised immune systems:

Do not eat hot dogs, luncheon meats, or deli meats, unless they are reheated until they are steaming hot.
Avoid getting the liquid from hot dog packages onto other foods sources, utensils, and food preparation surfaces, and remember to wash hands after handling hot dogs, luncheon meats, and deli meats.
Do not eat soft cheese products such as feta, Brie, and Camembert, blue-veined cheeses, or Mexican-style cheeses such as queso blanco, queso fresco, and Panela, unless they clearly state they are made from pasteurized milk written on the labelling of the product.
Do not eat chilled pâtés or meat spreads. Canned or shelf-stable pâtés and meat spreads can be eaten.
Do not eat refrigerated smoked seafood, unless it is contained in a cooked dish, such as a casserole. Refrigerated smoked seafood, such as salmon, trout, whitefish, cod, tuna or mackerel, is most often labeled as “nova-style,” “lox,” “kippered,” “smoked,” or “jerky.” The fish is found in the refrigerator section or sold over deli counters of grocery stores and delicatessens and supermarkets. Canned or shelf-stable smoked seafood may be eaten.

bird-815011_1920Zoonotic diseases are ones which are passed from the animal kingdom to human beings. Many micro organisms tend to be species specific and it is for this reason that there are not a great many zoonotic diseases. Some diseases passed on to us via animals are very common whereas some others are very rare. Some have the potential to cause world catastrophes whereas others may just about give us an upset stomach.
Below you will find a list of zoonotic diseases in alphabetical order.

Anthrax is a serious disease that is found in all warm blooded animals. The specific host is thought to be antelope and carnivores seem to react more slowly to the bacteria. The bacteria responsible for the cause of anthrax is Bacillus Anthracis. Human infections usually occur through the skin but it may also be inhaled or ingested. This is a very resistant spore forming bacteria whose spores may survive for decades in soil or animal products. The distribution is worldwide. Gastrointestinal anthrax is a very uncommon, often-fatal manifestation of the disease, caused by devouring meat from an animal that died of the disease. Gastrointestinal anthrax causes inflammation of the  stomach and the intestine accompanied by sores or ulcers, much the same as the lesions that appear on the skin in the skin form of anthrax. The primary signs of the disease include nausea, vomiting, loss of appetite and fever, followed by severe abdominal pain, vomiting of  blood, and severe and bloody diarrhea.

Brucellosis comes in four strains, B. abortus (in cattle), B. melitensis (sheep or goats), B. suis (pigs), and canis (dogs). The distribution of brucellosis is distributed worldwide. The disease id contracted via direct contact with animal excretions including milk. it is a disease caused by any of several forms of the gram-negative coccobacilli Brucella: Brucella melitensis, B. abortus, B. suis, and B. canis, the latter of which is very rare and causes only mild illness. Brucellosis is most common in rural areas among farming populations, vets, meat packers, slaughterhouse staff, and livestock breeders. Laboratory workers are also among those who are at risk. It is primarily a disease of animals (including cattle, pigs, sheep, camels, goats, and dogs); humans usually contract it through ingestion of contaminated and unpasteurized milk or other non cooked milk products or by ingesting raw meat or bone marrow, through skin lesions and cuts, through direct contact with an infected animal, or through the inhalation of dust particles that may be present in contaminated soil. Symptoms of brucellosis are manifested as follows:  fever, chills, sweating, malaise, and weakness. The fever often occurs in recurring waves, rising in the evening and subsiding during the day,  separated by periods of remission at intervals. Other symptoms may include  weight loss, headache, muscle and joint pain, and an enlarged spleen, and  often orchiepididymitis in young men. In some victims the disease is acute; however, more often it is chronic, recurring over a period of months or years. Although brucellosis itself is rarely fatal, treatment is important because serious complications such as pneumonia, endocarditis, meningitis, and encephalitis may develop. Tetracycline plus streptomycin is the preferred treatment for this disease; bed rest is also of great importance. A vaccine is available outside the United States. The disease can also be called Cyprus fever, dust fever, Gibraltar fever, Malta fever, Mediterranean fever and  undulant fever. See also abortus fever.

Campylobacteriosis is caused by the bacterium campylobacter spp. It is carried by many animal species with a seemingly increasing incidence rate. Most species of animals seem to be reasonably host specific but cross infection is possible usually via fecal contamination of food. Improper or incomplete cooking of food is the most common way that the disease is spread, and it is commonly thought by bacteriologists that poultry account for over half the diagnosed cases. Untreated water and raw milk are also potential sources of contamination.
The incubation period after exposure is from one to ten days.  symptoms begin with a day or two of mild fever, muscle aches, and headaches. This stage is followed by symptoms that involve the the intestinal tract. Diarrhea occurs with or without the presence of blood and severe abdominal cramps are the overriding intestinal symptom. The severity of symptoms may vary from case to case, ranging from only mild fever to  severe dehydration and very rarely death (this is seen mainly in the very young or old). The disease usually lasts for about a week, but persists longer in about twenty percent of cases. At least ten percent will have a relapse, and some patients will continue to pass the bacteria for several weeks after recovery.
Complications

Clostridial disease is caused by the bacterium clostridium spp. It is transferred by mammals, birds and fish with a worldwide distribution. Although the disease is normally transmitted through wound infection, food poisoning does occur. There is little danger of cross species transmission. The clostridial family of bacteria are noted by their ability to manufacture very potent toxins. The most potent toxin in nature is produced by the bacterium Clostridium botulinum. This toxin renders the bodies ability to contract muscles ineffective and death will occur by paralysis and asphyxiation, or the inability to inhale. Clostridium botulinum is found in the manure of animals along with clostridium tetani, clostridium difficile and clostridium perfringens, which causes gas gangrene. These bacteria are spore forming and the spores can survive for many years in soil. When conditions are favorable the bacterial spores will grow back into bacteria and begin to produce toxin.

Food that has been improperly preserved or stored can harbor botulinum toxin-producing clostridia. Botulism symptoms usually appear within 18-36 hours after eating contaminated food, in extreme cases it may take four hours to eight days for the bacteria to develop toxin. Initial signs of infection include blurred or double vision and difficulty in swallowing food and speaking.  Gastrointestinal problems may include constipation, nausea, and vomiting. As botulism progresses, the victim experiences weakness or paralysis, starting with the head muscles and progressing down the body. Breathing eventually becomes increasingly more and more difficult. and without medical intervention, respiratory failure and death are the likely outcome.

Listeriosis is caused by the bacterium listeria monocytogenes and it can be found in numerous species of animals and birds. It has a worldwide distribution. Listeriosis was traditionally considered to be a disease of animals for the most part. However in recent decades there has been an alarming increase in the incidence of this disease. The symptoms can be severe and patients who are high risk may have a problem overcoming listeriosis. It is becoming resistant to many forms of antibiotics. This is primarily a food borne bacteria. Listeria can be contracted by the ingestion of contaminated meat, dairy products, shellfish, dust and by coming into contact with infected animals. Listeria can pass through the wall of the gut and enter the bloodstream. It likes to sit on the central nervous system and spinal column. Pregnant mothers can spread this disease to their unborn babies through the placenta. Listeria cam cause severe flu like symptoms, meningitis and encephalitis. Listeria is also found in soil, sewage and in five percent of the intestines of humans without them feeling any ill effect.

Salmonellosis is transmitted by the salmonella spp. Bacteria which has over two thousand serotypes. It can be found in all animal species but it is not commonly thought to infect fish. The distribution of salmonellosis is worldwide and the occurrence of this disease is mostly attributed to the ingestion of undercooked food which is contaminated with feces. It is a form of gastroenteritis that is usually caused by the ingestion of food that has been contaminated with a species of Salmonella bacillus. It is characterized by an incubation period of six hours  to forty eight  hours which is followed by sudden colicky abdominal pain, high fever, and bloody, watery diarrhea. Nausea and vomiting are common symptoms, and abdominal signs may be almost identical  those of acute appendicitis or cholecystitis.

Symptoms usually last from four to seven days, but diarrhea and fever may persist for up to 2 weeks. Dehydration may occur. There is no specific treatment for salmonellosis. Antibiotics are usually not prescribed unless the disease has spread beyond the intestine and into other organs. Adequate cooking, good refrigeration, and attention to personal hygiene, especially the washing of hands may reduce the frequency of  salmonella outbreaks. Salmonella can also cause typhoid fever.

Tuberculosis is caused by the bacterium mycobacterium bovis (cattle). It can be transferred to humans via cattle and non human primates. The distribution of tuberculosis is worldwide and has now been linked to the aids virus. The disease can be transmitted by any animal species including humans. It now normally takes treatment with three forms of antibiotics simultaneously to combat this bacteria. No other disease throughout history has claimed so many lives.  The tuberculosis bacteria will infect the organ via which it entered the body. In most cases this is the lungs. As it has a protective enveloping it manages to outsmart the bodies specific immune system. The tuberculosis bacteria can survive within the non specific white blood cells and by colonising them it can move around the body from organ to organ. This is a slow process. It can transpire over a period of years. In the early part of the last century one in seven people were infected with tuberculosis. In the western world this number has dropped greatly due to the improvement in living conditions and lifestyle. In the third world, particularly Africa , conditions are still right for tuberculosis infection.

Tularemia is transmitted by the Francisella Bacteria. It is transmitted to humans by rabbits, dogs, cats, rodents, sheep and deer. Its distribution is circumpolar within the confines of the northern hemisphere. The disease is transmitted through ingestion when exposed to infected animals and also via bites of arthropods. It is an infectious disease of animals caused by the bacillus Francisella (Pasteurella) tularensis, which may be transmitted by insect vectors or direct contact. It is characterized in humans by fever, headache, and an ulcerated skin lesion with localized lymph node enlargement or by eye infection, GI ulcerations, or pneumonia, depending on the site of entry and the response of the host. This disease can be fatal if not treated with the appropriate antibiotics. Treatment includes streptomycin, chloramphenicol, and tetracycline. Recovery produces lifelong immunity. A vaccine was used in the past to protect laboratory workers but is not currently available; however, a new vaccine is in development. Also called deerfly fever, rabbit fever. Also spelled tularaemia.

Vibriosis is transmitted by the Vibrio parahaemolyticus or the V. alginolyticus bacteria. It is transmitted salt water fish and shellfish and is found primarily in the pacific regions including Asia, Australia, North America and the gulf of Mexico . The cause is the ingestion of undercooked contaminated food. Vibriosis is caused by eating seafood contaminated with Vibrio parahaemolyticus or Vibrio vulnificus. These bacteria damage the inner wall of the intestine, which causes diarrhea and related symptoms. Vibrio vulnificus can get through the intestinal wall and into the bloodstream.
Persons at risk for severe, often fatal vibriosis include those with liver disease (cirrhosis), excess iron (hemochromatosis), thalassemia (a blood disorder), AIDS, diabetes, or those who are immunosuppressed.
Symptoms of intestinal infection occur within two days of eating contaminated seafood. Symptoms last for two to 10 days and include watery diarrhea, abdominal cramps, nausea, vomiting, headache, and possibly fever. Symptoms of a blood infection develop one to two days after eating contaminated seafood, and include fever, chills, low blood pressure, and large fluid-filled blisters on the arms or legs. Similar blisters can also be produced by a Vibrio vulnificus skin infection. This can occur when the skin is pierced by the spines of infected fish. These infections can be severe and sometimes require amputations if not treated in time.

Yersiniosis is caused by the yersinia paratuberculosis or the V enterocolitica bacteria and is passed onto human beings by Animals and birds. It is distributed in the northern hemisphere and is transmitted via contaminated food and water.

Yersinia p. causes septicemia (blood poisoning) often with signs of gastroenteritis which is caused by Yersinia pseudotuberculosis, this occurs in wild rodents, birds, and most domestic species, particularly cats, although this is not common. The symptoms are: high  fever, severe toxemia with a high fatality rate. At postmortem there are large numbers of embolic abscesses in most of the internal organs. It is also called  pseudotuberculosis because of the way it infects multiple organs.
Occurs also in many species of fish as a septicemia. This form of infection is caused by Yersinia ruckeri.

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