Salmonella is the second most common diarrheal pathogen in Austria and is mainly transmitted through food. Infection occurs through ingestion of food containing salmonella, primarily eggs and egg products, poultry, meat and dairy products, and ice cream (however, there is hardly any food in which salmonella has not been detected). Illness usually only occurs when relatively large amounts of bacteria (more than 100,000 germs) are ingested. This number of germs, known as the infectious dose, is easily reached if food is not stored properly, since Salmonella can multiply explosively in food at room temperature within a few hours (doubling the number of germs every 20 minutes). However, the infection dose may be significantly lower in infants, the elderly, persons with a compromised immune system or also in connection with fatty foods (e.g. chocolate).

Salmonellosis is a diarrheal disease (including vomiting and abdominal cramps) that is common worldwide and is caused by infection with bacteria of the genus Salmonella(S.). Throughout Europe, the two serovars S. Enteritidis and S. Typhimurium are the main causative agents of foodborne salmonellosis in humans. The pathogens of typhoid and paratyphoid fever(S. Typhi and S. Paratyphi) are to be distinguished from them: These do not occur in Austria, but only in tropical and subtropical countries with low hygiene standards; they cause systemic diseases with intestinal involvement.

The transmission routes of Salmonella are very diverse. Farm animals can become infected via Salmonella-contaminated feed. In chickens, Salmonella colonization often remains hidden because the animals do not become ill from it. Occasionally, entire flocks of laying hens become unrecognized permanent excretors. Transfer of the germs to the still unlaid egg in the hen leads to eggs containing Salmonella. If these are not sufficiently heated before consumption, they can pose a health risk to humans.

Salmonella generally grows in a temperature range of 10 to 47 °C and is not killed by freezing. Heating to above 70 °C is considered to kill germs. However, since this temperature must be reached throughout the food during cooking, a cooking time of 15 minutes above 70 °C should be observed.

Domestic and farm animals (especially poultry), wild animals (birds) and exotic reptiles

Salmonella is mainly transmitted by eating raw or insufficiently heated food of animal origin (eggs, poultry meat, meat from other animal species and raw milk). Home-made products containing raw eggs, such as tiramisu, mayonnaise, creams and ice cream, may also be contaminated with Salmonella.

Unheated or insufficiently heated meat (such as poultry meat, kebabs, minced meat, raw sausages) can pose a risk during processing if they come into contact with products that are no longer heated (e.g. potato salad). This transmission to other foodstuffs (cross-contamination) can also occur through insufficiently cleaned utensils, such as cutting boards, knives and towels or failure to wash hands. In addition to kitchen hygiene, great attention must be paid to the continuous refrigeration of raw products during food preparation.

A small proportion of salmonelloses occur through smear infections, an unintentional ingestion of Salmonella through contact with infected humans and animals or with objects contaminated with faeces. Exotic small animals (mainly turtles and iguanas) can also be considered as reservoirs for such smear infections. Thorough cleaning of the hands with soap and warm water is recommended after each animal contact.

6-72 hours, usually 12-36 hours

Symptoms of the disease may include nausea, diarrhea, fever, vomiting, circulatory problems and abdominal cramps. The symptoms usually last only a few days. The course of the disease is often mild or asymptomatic, depending on the number of germs ingested and the immune status of the affected person. In elderly persons, salmonellosis can quickly lead to a life-threatening condition due to the high fluid loss and the associated circulatory stress.

Patients with gastrointestinal complaints without other risk factors should only be treated with antibiotics in special cases, as this can prolong bacterial excretion and develop resistance to antibiotics. In most cases, a therapy that balances the water and electrolyte balance is sufficient.

Food, especially meat, poultry, eggs or pasta with cream filling, should be well boiled and not kept at room temperature for several hours when cooked. After handling raw poultry meat, thorough hand washing is essential before starting other kitchen tasks. Defrosting water from frozen meat should be emptied into the sink and then rinsed hot. All work surfaces and utensils that have been in contact with raw poultry meat, other raw meat or raw eggs should be cleaned with detergent and hot water. Allow freshly prepared food to cool and then store in the refrigerator unless it is to be eaten immediately.

People with salmonellosis must not handle food professionally during the period of illness.

In 2024, 1,416 laboratory-confirmed cases of the disease were reported to the epidemiological reporting system (EMS) (EMS, as at 17.02.2025), which corresponds to an incidence of 15.5 cases per 100,000 inhabitants. Initial isolates from 1,400 sick/infected persons were sent to the NRZ Salmonella. Salmonella was therefore once again the second most frequently reported cause of bacterial food poisoning in Austria after campylobacter.

From 2002 to 2024, the number of salmonellosis cases fell by 83% (2002: 8,405 initial isolates; Annual Report of the Salmonella Centre 2002). This decline in salmonellosis in humans was achieved almost exclusively by the decline in S . Enteritidis infections (2002: 7,459 isolates; 2024: 579 isolates).

The spectrum of the most common Salmonella serovars in human cases of illness has changed slightly in recent years. S . Infantis, which is the most common serovar in broiler chickens, the monophasic variant of S. Typhimurium (probable reservoir: pigs) and S. Coeln are becoming increasingly important alongside S. Enteritidis and the classic biphasic variant of S. Typhimurium.

In 2024, 5,211 food samples were analysed for salmonella, mainly meat and meat preparations (approx. 1,200 samples), other and ready-to-eat foods (approx. 1,400 samples), milk, dairy products (approx. 720 samples), fruit, fruit juices, vegetables, salads, spices and mushrooms (approx. 660 samples), baked goods (approx. 280 samples), eggs and egg products (approx. 210 samples), fish and fish products (approx. 120 samples). Salmonella was detected in 50 samples, predominantly in meat and meat preparations from poultry (44 samples). S. Infantis was isolated most frequently (39 times), of which 22 times in fresh chicken meat and chicken meat products and 16 times in fresh poultry meat. S . Enteritidis was found in one fresh chicken meat sample and S. Typhimurium in two samples of fresh poultry meat (without further details of the poultry).

Animal foodstuffs are the most important source of salmonella infection for humans. In order to determine the significance of different animal populations as reservoirs of salmonella, standardised EU-wide baseline studies have been carried out on various livestock species in recent years. These studies have shown for Austria that poultry (laying hens, broilers and fattening turkeys) play the most important role for salmonellosis in humans and that all other animal species tested (with the exception of reptiles) are only rarely carriers of salmonella.

Based on these studies, the EU has set maximum levels per year at which poultry flocks may be contaminated with the most important serovars in human medicine, S. Enteritidis and S. Typhimurium, including its monophasic variant: This is 2% for laying hens, 1% for broilers and turkeys and 1% for parent stock of chickens (in addition to S. Enteritidis and S. Typhimurium, the target also includes S. Infantis, S. Virchow and S. Hadar). In 2023, the specified targets were achieved in Austria for all types of poultry use.

S. Infantis is an increasingly frequently detected serovar: since 2016 as the third most important serovar in human diseases, in 2024 as the fourth most important serovar and as the most frequent serovar in poultry meat and in broiler flocks. This S. Infantis is usually a multi-resistant variant that is resistant to the three antibiotic classes quinolones, sulphonamides and tetracyclines.

The Salmonella control programme in the EU provides for the most important Salmonella serovars for humans to be combated in animal populations. As S. Infantis is not included in the serovars to be controlled in broiler chickens, no financial support is provided EU-wide for control methods such as possible vaccination or culling of flocks. Although all flocks are tested for salmonella before slaughter, there are no legal consequences if serovars other than the target serovars are detected. However, more and more slaughterhouse operators are refusing to slaughter Salmonella-positive flocks at all. As a result, fattening herds are not slaughtered but culled. This strain of S. Infantis has become established in domestic broiler flocks and is very difficult to eliminate from the barns despite thorough cleaning and disinfection measures.

In turkeys, the prevalence of Salmonella spp. has been reduced from over 10% to < 3% since the start of the control programme in 2010. In 2024, however, this rose again to 5.9%.

Animal feed is subject to a permanent monitoring programme in Austria. As part of the official controls, samples are taken both on farms and in warehouses, compound feed plants and trading companies. Both complete feed mixtures and individual components are officially analysed. In 2024, salmonella(S. Yoruba) was detected in one of 200 feed samples analysed for farm animals (0.5 %). Protein-rich extraction meals or cakes (by-products from the edible oil processing industry) are considered to be the most significant source of salmonella. These can introduce salmonella into the feed chain and contaminate the compound feed produced from them.

In 2024, 32 pet food and chew toy samples were officially analysed. S. Muenster was detected in one. Handling pet food, especially chew toys, poses a demonstrable risk to humans. You should therefore wash your hands after feeding and playing with dogs or cats.

If salmonella is isolated from human or animal test material or from food, laboratories in Austria are obliged to send these isolates to the National Reference Centre for Salmonella (NRZ S) in accordance with the Epidemics Act, the Poultry Hygiene Ordinance and the Food Safety and Consumer Protection Act. The isolates are typed there in order to clarify possible links between the occurrence of the pathogens along the food chain.

In 2024, 1,400 initial human isolates were typed at the National Reference Centre for Salmonella. The discrepancy in the number of reported cases to initial isolates is partly due to the reference centre's practice of counting multiple infections separately (e.g. detection of S. Enteritidis and S. Typhimurium in one submission is counted as two events/first isolates). In addition, isolates from persons infected with Salmonella but not ill and from persons who have not been infected with Salmonella via food but, for example, through contact with reptiles, are also recorded.

The pathogen is usually detected by culturing stool (faeces), possibly also blood or pus. The examination of blood for specific antibodies is not conclusive.

The National Reference Centre for Salmonella at AGES in Graz carries out serotyping according to the White-Kauffmann-Le Minor scheme for all human and non-human Salmonella detected in Austria. In addition, the most important human-medical serotypes S. Enteritidis and S. Typhimurium and all isolates suspected of being part of a (food-borne) outbreak are typed using sequencing (NGS, next generation sequencing).

Salmonella infections can be detected in almost all animal species. Reptiles are particularly affected by latent infections with a broad spectrum of serovars. Salmonellosis in cattle: S. Dublin is adapted to cattle, but other serovars can also cause general infections with severe clinical pictures. Calves from the 2nd week of life are most susceptible. The predominant symptoms are diarrhoea, disturbances of the general condition or pneumonia, which become milder with increasing age. In cows, however, severe diseases with diarrhoea, milk loss and abortions may occur. Salmonellosis in pigs: Adapted species are S. Choleraesuis and S. Typhisuis. Non-adapted serovars cause disease much less frequently, especially with diarrhea. Affected are weanling pigs and young pigs up to 60 kg, the infection usually progresses as a febrile general disease with pulmonary symptoms, more rarely with diarrhoea. Abortions are possible in sows. Salmonellosis in sheep: S. Abortusovis is strictly adapted to sheep and is one of the most important abortive pathogens. Oral or mating infection is followed by a general septicaemic infection. Typical symptom is lambing in the 4th or 5th month of gestation, besides puerperal complications and general diseases of all ages. Non-adapted serovars cause latent infections and diarrhea as well as abortions in sheep. Salmonelloses in horses: S. abortusequi is the adapted type; after oral infection or infection via the mating act, a general infection develops that can lead to foaling in the 4th month of gestation. Life-weak foals are also possible. Mares develop resilient immunity after abortion. Unadapted serovars can lead to asymptomatic disease with shedding of pathogen or mild to severe disease up to septicemia. Salmonellosis in dogs and cats: These species have a higher resistance to Salmonella, there are no adapted serovars. Most often latent infections are observed, under the influence of favoring factors, diarrhea, vomiting and fever may also develop. Salmonellosis in chickens: S. Gallinarum is adapted to chickens, but can also occur in turkeys and some other bird species. Mammals are not susceptible. This serovar occurs in 2 biovars: Biovar Pullorum is responsible for white chick dysentery or pullorum disease and causes acute septicemic infections in chicks up to 3 to 6 weeks of age. Biovar gallinarum is the causative agent of so-called chicken typhus, which occurs primarily in older chickens. Infections with non-adapted types usually do not cause disease in the chicken, but latent infections. However, these are an important source of foodborne infections and therefore receive considerable attention. The most important serovar in this context in Austria is S. Enteritidis, followed by S. Typhimurium. Salmonellosis in waterfowl: has received increased attention as a potential source of infection for humans long before chickens, therefore special rules for the consumption of duck eggs have been in place for a long time. Living in standing water, these animals have increased infection pressure. Diseases with diarrhoea and septicaemia occur mainly in young animals (keel disease: back swimming of diseased animals).

Salmonella in dust: Protein-containing feed materials such as soya, rapeseed or sunflower extraction meal are considered a significant source of contamination for compound feed and compound feed companies. Salmonella is found in feedstuffs in uneven distribution and often in very low concentrations. These factors make sampling and the analytical detection of positive batches difficult.

However, even if feed contains only very few salmonella, optimal propagation conditions, for example in the poultry intestine, can infect the entire herd within a few days without the animals showing any clinical symptoms. The infection of a flock then only manifests itself through positive boot swab samples.

In addition to the regular inspection of incoming feed materials, dust samples from the process environment are particularly suitable for routine checks in a compound feed factory. Due to their large surface area, dust particles are an ideal medium for pathogens, meaning that even low levels of Salmonella contamination can be detected. Dust, which is drawn along the entire production chain of a feed, is therefore a very sensitive matrix for the detection of salmonella and also reflects the hygiene status of a compound feed plant.

Decontamination with organic acids: Salmonella in feed can cause enormous economic damage to the compound feed companies and agricultural businesses affected, as the feed in question is not marketable. In principle, the greatest possible hygiene must be ensured in all work steps in the compound feed plant and, accordingly, contamination or recontamination with salmonella after thermal treatment of the feed must be avoided.

Decontamination of salmonella in feed is permitted under feed legislation. A compound feed manufacturer only has a few options for decontamination. With appropriate effort, the feed can be hygienised primarily using thermal processes. If heat treatment is not possible or undesirable (e.g. in the case of layer meal), the feed can be treated with organic acids

The hygienisation of feed containing salmonella using organic acids is only recommended for the treatment of individual feedstuffs due to the high acid additions required. Decontamination of compound feed is not recommended due to the high acid additions required, for example because of the resulting feed refusal or interactions with other feed components.