With record levels of avian influenza (AI) circulating, it’s important that poultry farmers don’t overlook the potential threats posed by other diseases, including salmonella.
In July 2022, an investigation revealed that “a dangerous strain of salmonella” was becoming more prevalent in the United Kingdom, and worryingly, had already entered the food chain. Tests carried out on raw meat, processed poultry and animal food confirmed the presence of the potentially deadly disease.
First discovered more than 100 years ago in 1879, salmonella is linked to typhoid fever. The first mass outbreak to be documented occurred in New York at the turn of the century, when a cook named Mary Mallon (today better known as Typhoid Mary) was found to be a carrier of Salmonella Typhi which infected more than 3,000 people between 1906-7.
What is salmonella?
Salmonella is an umbrella term for some 2,500 different serotypes from a family of bacteria known as Enterobacteriaceae. Bacteria within this family can be divided into two camps:
- Typhoidal: the smaller group of bacteria which causes those infected to develop typhoid fever, with limited human transmission.
- Non-typhoidal: this is the largest group with Salmonella serotypes within this group able to be transmitted between poultry and humans, causing illness and endangering public health via the food supply.
Which Salmonella serotypes are poultry most susceptible to?
Poultry are most often found to be infected with Salmonella Infantis, Salmonella Gallinarum or Salmonella Pullorum. The latter two are responsible for the greatest rates of mortality amongst poultry flocks. Salmonella Gallinarum leads to fowl typhoid (FT) while Salmonella Pullorum causes poultry to develop pullorum disease (PD).
Download our Salmonella spotlight here.
How is the disease spread?
Salmonella bacteria can spread through a flock quickly, causing mass levels of infection. The bacteria spreads in several ways, creating numerous possible routes of infection on farms and within animal housing, and meaning that farmers need to be particularly mindful of maintaining high standards of conceptual, operational and procedural biosecurity to close off those transmission avenues.
It’s important to note that Salmonella is a very hardy bacteria, able to survive a broad spectrum of temperatures, in a range of conditions including low oxygen, low moisture and wet environments and on a raft of different materials.
Once infected, one bird can spread the disease to other poultry, putting entire flocks at risk.
Salmonella can also be introduced through contaminated clothing entering onto farm, and by vehicles and other equipment including cages and egg trays. It’s also spread via faeces and poultry manure, through eggs and eggshells, contaminated food and in water. Infected birds can also pass on the disease through their eggs to chicks.
Mites are a known carrier of the salmonella bacteria and play a prolific role in transmission of strains such as Salmonella Infantis, Salmonella Gallinarum and Salmonella Pullorum.
Download our Salmonella spotlight here.
What symptoms are visible in poultry infected with Salmonella?
Salmonella is a particularly tricky disease for farmers to spot. Due to the large variety of salmonella serotypes, infection can present in a number of ways.
The added complication for poultry farmers comes from the fact that birds infected with certain types of Salmonella harmful to public health often don’t show symptoms of the disease, making containment difficult.
Other serotypes do cause symptoms and are harmful to bird health but are not thought to pose a danger to humans.
Symptoms of infection include:
- Poor growth in younger birds
- Diarrhoea
- A loss of appetite
- Lethargy or a notable lack of energy
- A decline in egg hatching rates
- A sudden increase in mortality rates
Birds which are infected with Salmonella and subsequently develop fowl typhoid (FT) or Salmonella Pullorum (PD) will typically display 100% mortality rates.
Download our Salmonella spotlight here.
Protecting against Salmonella
If you’re a member of the Red Tractor quality assurance program, you’ll be required to vaccinate your birds to protect against Salmonella. Other biosecurity measures are also required to safeguard your flock against an outbreak of Salmonella:
- Because Salmonella can be spread through contaminated animal feed and water, you should always opt for Salmonella-negative feed. This has been treated specifically to ensure it is free from Salmonella bacteria. Drinking water should also be chlorinated.
- Salmonella has high levels of survivability on a range of surfaces, so it can be easily introduced on clothing, vehicles, and equipment. Implementing cleansing and disinfection measures before and after equipment is used in the poultry shed or near bird housing helps to prevent bacteria introduction. Likewise, clothing should be farm-specific, clean, and laundered regularly.
- Prevent contact with wild birds and vermin, and ensure housing is well maintained to guard against access by wild birds or pests.
For more guidance and support on dealing with Salmonella, including what to do if you suspect an outbreak, download our Salmonella spotlight guide.
