question: Why do certain animals carry salmonella in their body? Why does it make humans sick?
comment: Salmonella is a bacteria that lives in digestive tracts of all warm blooded animals, and another type of salmonella is in cold blooded animals, mostly reptiles. Certain species of salmonella bacteria cause food borne illness, also called salmonella. (Of course there are scientific names for all of these but I’m trying to keep it simple). When a person ingests food containing a high concentration of the bacteria, they get sick. Young people, old people, and people with weakened immune systems are more susceptible. And guess where that contamination comes from...poop! Contaminated poop.
passages: About 2,000 serotypes of nontyphoidal "Salmonella" are known, which may be responsible for as many as 1.4 million illnesses in the United States each year. People who are at risk for severe illness include infants, elderly, organ-transplant recipients, and the immunocompromised.
  
  Section::::Nontyphoidal "Salmonella".:Invasive.
   Section::::Global monitoring.
  
  In Germany, food-borne infections must be reported. From 1990 to 2016, the number of officially recorded cases decreased from about 200,000 to about 13,000 cases. In the United States, about 1,200,000 cases of "Salmonella" infection are estimated to occur each year. A World Health Organization study estimated that 21,650,974 cases of typhoid fever occurred in 2000, 216,510 of which resulted in death, along with 5,412,744 cases of paratyphoid fever.
  
  Section::::Molecular mechanisms of infection.
   certain serotypes causing illness. Nontyphoidal serotypes can be transferred from animal-to-human and from human-to-human. They usually invade only the gastrointestinal tract and cause salmonellosis, the symptoms of which can be resolved without antibiotics. However, in sub-Saharan Africa, nontyphoidal "Salmonella" can be invasive and cause paratyphoid fever, which requires immediate treatment with antibiotics. Typhoidal serotypes can only be transferred from human-to-human, and can cause food-borne infection, typhoid fever, and paratyphoid fever. Typhoid fever is caused by "Salmonella" invading the bloodstream (the typhoidal form), or in addition spreads throughout the body, invades organs, and secretes endotoxins (the septic form). This can lead to life-threatening hypovolemic shock and septic shock, and requires intensive care including antibiotics.
   Section::::Typhoidal "Salmonella".
   Section::::Serotyping.
   Section::::History.
   Most infections are due to ingestion of food contaminated by animal feces, or by human feces, such as by a food-service worker at a commercial eatery. "Salmonella" serotypes can be divided into two main groups—typhoidal and nontyphoidal. Nontyphoidal serotypes are more common, and usually cause self-limiting gastrointestinal disease. They can infect a range of animals, and are zoonotic, meaning they can be transferred between humans and other animals. Typhoidal serotypes include "Salmonella" Typhi and "Salmonella" Paratyphi A, which are adapted to humans and do not occur in other animals.
  
  Section::::Nontyphoidal "Salmonella".
  
  Section::::Nontyphoidal "Salmonella".:Non-invasive.
   Section::::Molecular mechanisms of infection.:Selective Immune Knockout.
  
  A 2018 Imperial College London study shows how salmonella disrupt specific arms of the immune system (e.g. 3 of 5 NF-kappaB proteins) using a family of zinc metalloproteinase effectors, leaving others untouched.
  
  Section::::Resistance to oxidative burst.
   The collapse of the Aztec society in Mesoamerica is linked to a catastrophic "Salmonella" outbreak, one of humanity's deadliest, that occurred after the Spanish conquest.
  
  Section::::Taxonomy.
   One of the most common food-borne illnesses, "Salmonella" poisoning is caused by ingestion of unsanitary conditions during food preparation. "Salmonella" can also be transmitted to humans via reptiles like turtles and iguanas, which are known carriers of pathogen. Symptoms include chills, diarrhea and fever.
  
  Section::::Diseases Caused by Exogenous Bacteria.:Waterborne and Foodborne.:Cholera.
   "Salmonella" species are intracellular pathogens; 
   Section::::See also.
  
  BULLET::::- Host-pathogen interface
  
  BULLET::::- 1984 Rajneeshee bioterror attack
  
  BULLET::::- 2008 United States salmonellosis outbreak
  
  BULLET::::- 2008–2009 peanut-borne salmonellosis
  
  BULLET::::- Bismuth sulfite agar
  
  BULLET::::- Food testing strips
  
  BULLET::::- List of foodborne illness outbreaks
  
  BULLET::::- Wright County Egg
  
  BULLET::::- Rappaport Vassiliadis soya peptone broth
  
  BULLET::::- XLD agar
  
  BULLET::::- "American Public Health Association v. Butz"
  
  Section::::External links.
  
  BULLET::::- Background on Salmonella from the Food Safety and Inspection Service of the United States Department of Agriculture
  
  BULLET::::- Salmonella genomes and related information at PATRIC, a Bioinformatics Resource Center funded by NIAID
  
  BULLET::::- Questions and Answers about commercial and institutional sanitizing methods
   Those infected may become asymptomatic carriers, but this is relatively uncommon, with shedding observed in only 0.2 to 0.6% of cases after a year.
  
  Section::::Causes.
  
  BULLET::::- Contaminated food, often having no unusual look or smell
  
  BULLET::::- Poor kitchen hygiene, especially problematic in institutional kitchens and restaurants because this can lead to a significant outbreak
  
  BULLET::::- Excretions from either sick or infected but apparently clinically healthy people and animals (especially dangerous are caregivers and animals)
  
  BULLET::::- Polluted surface water and standing water (such as in shower hoses or unused water dispensers)
  
  BULLET::::- Unhygienically thawed poultry (the meltwater contains many bacteria)
   In the case of "Salmonella" a relatively large inoculum of 1 million to 1 billion organisms is necessary to produce symptoms in healthy human volunteers, as "Salmonellae" are very sensitive to acid. An unusually high stomach pH level (low acidity) greatly reduces the number of bacteria required to cause symptoms by a factor of between 10 and 100.
  
  Section::::Epidemiology.
  
  Asymptomatic subclinical infection may help spread these diseases, particularly "Staphylococcus aureus", "Campylobacter, Salmonella, Shigella, V. cholerae," and "Yersinia". For example, as of 1984 it was estimated that in the United States, 200,000 people were asymptomatic carriers of "Salmonella".
  
  Section::::Epidemiology.:Infants.
   Infection with nontyphoidal serotypes of "Salmonella" generally results in food poisoning. Infection usually occurs when a person ingests foods that contain a high concentration of the bacteria. Infants and young children are much more susceptible to infection, easily achieved by ingesting a small number of bacteria. In infants, infection through inhalation of bacteria-laden dust is possible.
   In 2010, an analysis of death certificates in the United States identified a total of 1,316 "Salmonella"-related deaths from 1990 to 2006. These were predominantly among older adults and those who were immunocompromised. The U.S. government reported as many as 20% of all chickens were contaminated with "Salmonella" in the late 1990s, and 16.3% were contaminated in 2005.
   Section::::Presence in agriculture.
  
  Section::::Presence in agriculture.:Contamination through defecation.
   Much of the success of "Salmonella" in causing infection is attributed to two type III secretion systems which function at different times during an infection. One is required for the invasion of nonphagocytic cells, colonization of the intestine, and induction of intestinal inflammatory responses and diarrhea. The other is important for survival in macrophages and establishment of systemic disease. These systems contain many genes which must work co-operatively to achieve infection.
   There are two species of "Salmonella": "Salmonella bongori" and "Salmonella enterica" with many subspecies. Infection is usually spread by eating contaminated meat, eggs, or milk. Other foods may spread the disease if they have come into contact with manure. A number of pets including cats, dogs, and reptiles can also carry and spread the infection. Diagnosis is by a stool test or blood tests.
   Antibodies against nontyphoidal "Salmonella" were first found in Malawi children in research published in 2008. The Malawian researchers identified an antibody that protects children against bacterial infections of the blood caused by nontyphoidal "Salmonella". A study at Queen Elizabeth Hospital in Blantyre found that children up to two years old develop antibodies that aid in killing the bacteria. This could lead to a possible "Salmonella" vaccine for humans.
  
  A 2014 study tested a vaccine on chickens which offered efficient protection against salmonellosis.
   "Salmonella" bacteria can be found in almost any product or animal that has been exposed to fecal matter. These exposures can occur from crops grown from waste-based fertilizers or from food items handled by infected humans. Salmonellosis is an intestinal disease, meaning that the bacteria must be ingested and processed through the intestines in order for infection to occur. Thus, salmonellosis is commonly spread to humans through ingestion of contaminated food items. It can also be spread through contact with reptiles and birds, usually after the person handles the animal or its environment (without hand-washing immediately) and then touches their mouth or food items. Those infected usually develop symptoms anywhere from 12–72 hours after first contact with "Salmonella" bacteria, and most do not require serious medical attention. This salmonellosis displays itself in humans with fever, abdominal pain, nausea, and, most commonly, diarrhea for a period of up to 7 days. Those requiring hospitalization usually are dehydrated or have extreme diarrhea, which can turn deadly, especially if the salmonella bacteria reaches the bloodstream. The elderly, young children, and those with weakened immune systems are most at risk for developing salmonellosis and suffering severe reactions. The most common serotypes of "Salmonella" in the United States and Europe are Enteritidis and Typhimurium.
   BULLET::::- An association with reptiles (pet tortoises, snakes, iguanas, and aquatic turtles) is well described.
  
  BULLET::::- Amphibians such as frogs
  
  "Salmonella" bacteria can survive for some time without a host; they are frequently found in polluted water, with contamination from the excrement of carrier animals being particularly important.
  
  The European Food Safety Authority highly recommends that when handling raw turkey meat, consumers and people involved in the food supply chain should pay attention to personal and food hygiene.
   One strain of "Salmonella" that has recently been emerging in the United States is "Salmonella javiana". "An outbreak occurred in 2002, there were 141 cases that occurred among the participants of the U.S. Transplant Games. Out of the 141 cases, most of the cases were either transplant recipients (34%) or people receiving immunosuppressive therapy (32%)". There is an increasing number of "Salmonella" serotypes that are multidrug resistant (MDR), which was identified by the CDC's National Antimicrobial Resistance Monitoring System. ""Salmonella javiana" causes 4% of nontyphodial "Salmonella" infections in the United States each year."
   The U.S. government reported as many as 20% of all chickens were contaminated with "Salmonella" in the late 1990s, and 16.3% were contaminated in 2005. In the mid- to late 20th century, "Salmonella enterica" serovar Enteritidis was a common contaminant of eggs. This is much less common now with the advent of hygiene measures in egg production, and the vaccination of laying hens to prevent "Salmonella" colonization. Various "Salmonella" serovars (strains) also cause severe diseases in animals.
  
  Section::::Epidemiology.:2007.
   Most cases of salmonellosis are caused by food infected with "S. enterica", which often infects cattle and poultry, though other animals such as domestic cats and hamsters have also been shown to be sources of infection in humans. Investigations of vacuum cleaner bags have shown that households can act as a reservoir of the bacterium; this is more likely if the household has contact with an infection source (i.e., members working with cattle or in a veterinary clinic).
  