Know your risks: Salmonellosis

The best prevention is achieved through understanding and taking precautions based on this knowledge. At Pest Expert we feel it is not only important that we supply you with the markets best pest control products, but also with in depth advice to help you treat and stay protected. In this series or articles we will aim to give you a solid understanding on the various disease transmitted by rodents, how to notice the signs and importantly how you can avoid them while carrying out your rodent treatment.

Salmonellosis

Salmonellosis is zoonotic pathogen, generally regarded as the most prevalent food borne Microbial Pathogens and amongst the leading causes of gastroenteritis in the industrialised world[1].

Salmonellosis is a diseased condition brought about through infection with the salmonella bacterium. With infection usually spread via ingestion of food and water contaminated with infected faeces, urine and bedding material. The bacteria is carried in the intestinal tracks, mostly without showing any clinical outward symptoms of the disease. Infected rodents cause the transmission of pathogens from the farm environment to the food animal. In an agro-ecological surrounding rodents can be infected with salmonella and transfer these pathogens to food animals whilst amplifying the number of bacteria in the farm environment.

Eliminating these pathogens in the first part of the food chain should be seen as a priority, as treatment is often not effective for the control of salmonellosis. Taking steps to prevent the spread of the infection is the best way to manage the condition in rats; as such rodent control should form an integral part of any comprehensive hygiene measures package.  Salmonella are rod shaped motile gram-negative bacteria of the family enterobacteriaceae[2]. The serotype s. typhi and s. paratyphi are adapted to humans[3].

How is Samonellosis transferred?

Salmonellosis is transferred through consuming water or food stuffs contaminated by bacteria spread through contact with rodent faeces and urine or through contact with water, food or bedding contaminated by salmonella carrying rodents.  Salmonella bacteria is carried in the intestinal tracts of animals, transmitted through ingestion of faeces. Humans usually obtain salmonella through eating contaminated beef, poultry, eggs or pork.

Is Salmonellosis common?

In 2002 there were 38 cases of Salmonella per 100,000 inhabitants within the EU, and in the US an estimated 1.4 million people have salmonellosis, leading to 14,800 hospitalizations and 415 deaths. The degree of contamination and the risks of transmission differ between different habitats, distinctions between rodents living in the wild, those in urban environs and those on farms; likewise conventional farms and organic farms, as such its frequency is largely habitat dependent.

What are the symptoms of Salmonellosis?

Incubation period: Ranges from several hours to two days from time of infection

The onset infection of Salmonellosis starts with attachment and internalisation to the cells of the small intestine, this invasion of enterocytes results in the extrusion of infected ephitelial cells into the intestinal lumen with consequent loss of absorptive surfaces and villus blunting. Infection with salmonella elicits a polymorphonuclear leukocyte influx[4] into infected mucosa and induces watery diarrhoea. In short Salmonellosis causes gastrointestinal problems including abdominal cramping, diarrhoea, fever, vomiting. It is when the bacteria passes through the mucosa cells and into the underlying tissues the bacteria can enter the bloodstream and spread throughout the body resulting in gastroenteritis which can be fatal. Young children and older people are most susceptible to acquiring the severe symptoms of salmonellosis after infection.

How is Salmonellosis treated?

Salmonellosis is diagnosed through testing a clinical specimen, such as a stool or blood sample to distinguish it from other illnesses with shared symptoms such as diarrhoea, fever and abdominal cramps. Once the sample has been cultured, if the Salmonella bacteria grows then it is ‘culture confirmed’.

Salmonella gastroenteritis is usually a self-limiting disease and many infections resolve themselves between 5-7 days from the early appearance of symptoms, as such the main required treatment is oral fluids and electrolyte replacement. More severe symptoms require hospitalization, for example severe diarrhoea may require rehydration with intravenous fluids.

As antibiotics do not appear shorten the duration of the symptoms they are not routinely used to treat uncomplicated non-typhoidal salmonella gastroenteritis. Antibiotics are only recommended for patients who have a severe illness resulting from Salmonellosis, such as high fever or bloodstream infection, particularly those who are considered high risk for serious disease or complications, infants, adults over the age of 65 and people with weakened immune systems.

Resistance to antimicrobial agents is not uncommon in salmonella, with emergent drug resistance being recorded over the past 20 years, this has limited the usefulness of some antibiotics. The main choices for antibiotic therapy for severe infections include fluoroquinolones, third-generation cephalosporins or ampicillin.  Bactericidal drugs are used for between 10-14 days.

What steps should I take to avoid Salmonellosis?

In a total package of hygiene measures, rodent control should form an integral part to prevent the transfer of food-borne pathogens.

Elimination of pathogens in the first part of the food chain is important to prevent disease amongst consumers of animal products.

Within animal production systems elimination of Salmonellosis can be more difficult, animals kept outdoors have easy access to potential sources of bacteria or parasites, with rodents being one of the leading causes of infection. As such the decontamination of farms is an important step in the eradication of salmonella infection throughout the food chain.

Salmonella is more frequent on organic product farms, this is largely attributed to their lack of rodent control and the use of rodenticide. However studies on organic farming have shown that live traps can be an effective alternative to the use of poison to reduce rodent pressure, these fall in line with the organic farming philosophy, causing less pollution and being advantageous for the welfare of non-target animals. As rodents can amplify the number of pathogens in environments and transfer them to food animals, organic farmers should be aware of the need for rodent control from the perspective of food safety.

To prevent the spread of infection, to yourself and to others you should follow the below instructions:

Wash and dry hands regularly, especially after going to the bathroom, before preparing food and after handling raw foods

Keep all work surfaces and utensils clean, washing food and vegetables before eating and cooking thoroughly to kill bacteria (Note: You should not prepare food for others if you are displaying any of the symptoms)

Covering all open wounds, cuts and abrasions with waterproof plasters before coming into contact with food or suspect waters

Avoid immersion in or ingesting suspect waters

Do not share towels or flannels and if any clothing or bedding is soiled, first remove any stools, and wash in a separate wash on a high temperatures.

Regularly clean toilets with disinfectant, washing handles, toilet seat and bathroom taps and surfaces with hot water and detergent

Wear disposable safety gloves and a mask when cleaning rodent urine, droppings or nest materials

Important: If you have salmonella infection and work with vulnerable groups of people, such as the elderly, unwell or young or in a food handling environment you should inform your employer immediately.

[1] Gastroenteritis: Inflammation of the stomach and intestines, typically resulting from bacterial toxins or viral infection and causing vomiting and diarrhoea.

[2] Enterobacteriaceae are a family of gran-negative bacteria, including pathogens such as Salmonella, Escherichia, Coli and Shingella.

[3] Serotype are distinct variations within a species of bacteria, classed together based upon their cell surface antigens allowing epidemiologic classification of organisms to the sub-species level. Salmonella has been determined to have over 2600 serotypes.

[4] polymorphonuclear leukocytes are a type of immune cell that has granules with enzymes which are released during infections , a polymorphonuclear leukocytes is a type of white blood cells.