Animal-based food is the most important source of Salmonella infections in humans. Standardised basic studies have been carried out in various animal populations across the EU over the past 3 years to record their significance as reservoirs for Salmonella. These studies showed that eggs and poultry play the most important role in Salmonella infections in humans in Austria, while all other animal species tested are only occasional carriers of Salmonella. The EU has defined limits for each Member State, specifying the maximum contamination of such poultry flocks with S. Enteritidis and S. Typhimurium: 2 % for laying hens, 1 % for broilers and turkeys and 1 % for parent animals of chickens (here S. Infantis, S. Virchow and S. Hadar are also part of the target requirements, in addition to S. Enteritidis und S. Typhimurium).
The Member States compile an annual report on the share of Salmonella-positive flocks for the various livestock of poultry, breeding hens, laying hens, chicken and turkey broilers as part of the EU-wide programme to combat Salmonella. The data gathered by the Poultry Health Data PHD are evaluated and used for national reports and then sent to the relevant authorities and to the European Food Safety Agency (EFSA), as part of the EU zoonosis report.
The data processed showed a similar, slightly regressive Salmonella prevalence in flocks of breeding hens, laying hens and broiler hens and a strongly declining prevalence in turkeys in 2014 as compared to previous years. The EU targets were achieved in all categories of poultry listed in the combating programmes in regards to serovars that are relevant to the control programme. A prevalence of 0 % of control relevant serovars was reached for breeding hens and turkeys and a prevalence of under 0.5 % for laying and broiler hens.
The successful fight against Salmonella infections requires a rather complex approach. The goal is to reduce Salmonella infection pressure and create and maintain Salmonella-free livestock, in addition to treating infected animals. This can only be achieved with complex, long-term control programmes. These objectives have already been introduced in Scandinavia to the point at which Salmonella is very rare in livestock. It has been possible to decrease the number of Salmonella-infected poultry flocks in Austria drastically in recent years. The number of positive groups in other livestock is very small.
Salmonella Infections in Animals
Salmonella infections can be detected in almost all animal species. Reptiles are particularly exposed to latent infections from a wide range of serovars.
Salmonellosis in cattle: S. Dublin is adapted to the animal, but also other serovars can cause general infections with severe clinical symptoms. Calves that are in their second week or older are the most susceptible. The most common symptoms are diarrhoea, general health problems and pneumonia, which get milder as the calf gets older. However, serious infections with diarrhoea, decline in milk production and miscarriages can occur in cows.
Salmonellosis in swine: adapted bacteria species are S. Choleraesuis und S. Typhisuis. Non-adapted serovars cause far fewer infections, in particular infections with diarrhoea. The infection affects pigs that are stopping weaning and young pigs up to 60 kg. The infection usually progresses to a feverish general disease with lung symptoms, occasionally with diarrhoea. Sows may have miscarriages.
Salmonellosis in sheep: S. Abortusovis is adapted solely to sheep and one of the most important pathogens causing miscarriages. Oral infection or infection during mating is followed by a septicaemic general infection. Miscarriages in the 4th or 5th month of pregnancy are the most typical symptom, in addition to puerperal complications and general diseases across all age groups. Non-adapted serovars cause latent infections, diarrhoea and miscarriages in sheep.
Salmonellosis in horses: S. Abortusequi is the adapted type. An oral infection or infection during mating is followed by a general infection that can lead to miscarriages in the 4th month of pregnancy. Very weak foals may be born. Mares develop immunity after the miscarriage. Non-adapted serovars may cause asymptomatic infections including the shedding of pathogens or mild to severe infections and even septicaemia.
Salmonellosis in cats and dogs: these animal species are more resistant to Salmonellae and there are no adapted serovars. Latent infections were observed in most cases, but diarrhoea, vomiting and fever were also observed under specific conditions.
Salmonelloses in chickens: S. Gallinarum has adapted to chickens, but can also occur in turkeys and a few other bird species. Mammals are not susceptible. This serovar is found in two biovars: Biovar Pullorum is responsible for Pullorum disease and results in acute septicaemic infections in chicks up to the 3rd to 6th week of life. Biovar Gallinarum is the cause for so-called fowl typhoid, which occurs predominantly in chickens. Infections with non-adapted types do rarely cause disease in chickens, but mostly cause latent infections. However, these latent infections are a primary source of food-borne infections, thus receiving lots of attention. The most important serovar in this context in Austria is S. Enteritidis, followed by S. Typhimurium.
Salmonelloses in water fowl: water fowl were identified as a potential source of infection in humans long before chickens. Thus, there have long been special rules in place for the consumption of duck eggs. These animals are exposed to higher infection pressure as they live in standing waters. Young animals are, in particular, affected with diarrhoea and septicaemia (Keel Disease: infected animals swim on their backs).