Scientific name

Description

Of the salmonella species, S. pullorum causes pullorum disease and S. gallinarum causes fowl typhoid in poultry. In the past, these two diseases have caused significant problems, though both diseases are now very well controlled in the poultry industry. However, they may still exist in backyard poultry. There is little risk of emus being exposed to these two types of salmonella.

However, the many salmonella species that can infect a wide range of hosts, including man, are more significant to the emu industry. The infection and disease that these salmonellae cause is generally known as ‘paratyphoid’.

Distribution and transmission

Salmonellae are widespread in the environment and a number of sources may infect a property, including wild birds, other emus, feed sources and other animals.

The organisms are reasonably resistant and can survive for several weeks or months in the environment in favourable conditions. They are susceptible to sunlight and drying out.

Carrier birds are the main reservoir of infection in poultry once the organism has established in a flock. These birds have been infected and survived but the organism has established itself in the intestine, where it causes the bird little problem but is regularly passed out in faeces. This is a source of contamination. Some rodents and insects also have a potential to act as reservoirs.

Paratyphoid has been detected on some emu farms in Queensland but the full extent of the problem is not known. Problems have occurred in young chicks less than two weeks old but further research is needed to determine the problem’s full impact and size. It is not known whether adult emus can become carriers, but it is known that paratyphoid affects a wide range of animals, so infection could probably become established in emu flocks.

Transmission between birds occurs mainly by ingestion. Sick birds and carriers excrete salmonella in their faeces, which can then contaminate food, water, litter and other areas.

Females can also lay eggs that are contaminated on the outside of the shell. The paratyphoid organisms are mobile and can penetrate the pores of a shell while it is still warm and moist. If these organisms are not killed through egg disinfection procedures, infected eggs will reach the hatcher. If these eggs hatch, large numbers of salmonella will be released into the hatcher.

Other chicks can become infected by inhaling organisms or eating contaminated fluff circulating round the hatcher. This can result in sickness, deaths and carrier birds from this batch of chicks.

Clinical signs

The disease has the potential to cause significant mortalities, including a high proportion of dead embryos in-shell in both pipped and unpipped stages.

After hatching, deaths may start after two to three days and continue for up to three weeks. The chicks look depressed and lethargic, and sit in one position with their heads down for long periods. They stop eating but may increase their water consumption. A profuse watery diarrhoea develops. Paralysis, blindness, eye infections and joint problems have also been reported in poultry.

In Queensland, signs in young chicks include depression and weakness, leading to death and sudden death with few preceding signs.

Diagnosis

A field diagnosis should be confirmed by sending samples to a veterinary laboratory, where the organism can be cultured and identified.

Freshly dead, whole chicks can be sent to a laboratory for examination or specific samples can be taken from post mortem. Samples should be kept chilled in a fridge and not frozen prior to dispatch.

Treatment

Therefore, it is important to consult your veterinarian regarding treatment and get samples to a laboratory as soon as possible. If a salmonella organism is cultured, the laboratory can also carry out drug sensitivity tests to identify which drugs the organism is susceptible or resistant to. This information is valuable in formulating an effective disease control program.

Prevention

If it becomes established on a property, a control program can be drawn up, which would concentrate on the areas where the disease causes the most damage, such as the incubation, hatching and brooder stages.

This program requires strict attention to hygiene and should include:

• collecting eggs daily and fumigating eggs with formaldehyde gas, which should eliminate or greatly reduce contamination on the outside of the shell. Here fumigation should be used rather than egg washing. If eggs are washed, a hot solution (43-49^oC) is used to expand the egg contents, and force air and hopefully any contamination out through the pores in the shell. The egg is then dried using hot air before the egg contents shrink back to normal size. If the egg is not dried before the contents shrink, the fluid and contamination may be sucked back through the shell’s pores
• washing hands or wearing disposable gloves when handling eggs. As outlined, salmonella are passed in the faeces and can then spread to contaminate many objects, including hands
• fumigating the hatcher between batches with formaldehyde or Virkon® S gas, or clean with a broad spectrum egg disinfectant, such as gluteraldehydes or orthosan. All fluff, dust and egg shell remains must also be removed
• observing chicks closely. Samples should be sent to a laboratory if chicks are dying or not doing well, or there is a high proportion of dead full-term embryos in shell
• using strategic antibiotic treatment to control infection in chicks
• considering additional precautions if problems are identified, such as
• regularly misting the eggs stored in the cold room with a recognised disinfectant. Eggs should not be handled or wiped until the surface has dried and/or each batch of eggs has been fumigated just before they are put into the incubator
• fumigating eggs as soon as they are put in the hatcher and before hatching begins. Advice should be sought if this option is used, as the amounts of formaldehyde and Condy’s crystals are different to other fumigations, and good ventilation is necessary.