Salmonellosis can be caused by any one of the salmonella group of bacteria. There are a large number of salmonella species spread widely throughout the environment.

Two individual salmonella species S. pullorum and S. gallinarum cause pullorum disease (S. pullorum) and fowl typhoid (S. gallinarum) in poultry. In the past these two diseases have caused significant problems, and both diseases are now very well controlled in the poultry industry. However, these diseases may still exist in backyard poultry. It would appear that there is little risk of emus being exposed to these two types of salmonella.

Of more significance to the emu industry are the large number of remaining salmonella species that are capable of infecting a wide range of hosts including man. Infection and disease caused by these salmonella is given the general term paratyphoid.

Paratyphoid occurs worldwide.

Salmonella are widespread in the environment and a property can be infected from a number of sources 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.

In poultry, carrier birds are the main reservoir of infection once the organism has established in a flock. These birds have been infected and have 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 then acts as 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 2 weeks of age, but further research is required to determine the full impact and size of the problem. It is not known whether adult emus can become carriers, but as it is known that paratyphoid affects a wide range of animals it is probable that infection could become established in emu flocks.

Transmission between birds occurs mainly by ingestion. Sick birds and carriers excrete salmonella in their faeces which then has a potential to contaminate food, water, litter etc.

Females can also lay eggs with contamination on the outside of the shell. The paratyphoid organisms are mobile and can penetrate the pores of the shell while it is still warm and moist. If these organisms are not killed during egg disinfection procedures, infected eggs will reach the hatcher. If these eggs hatch, large numbers of salmonella are released into the hatcher. Other chicks can become infected by inhalation of organisms or by eating contaminated fluff circulating round the hatcher. This can result in sickness, deaths and carrier birds from this batch of chicks.

In poultry, mature and semi-mature birds rarely have problems even though they may be infected. However, if these birds are stressed the infection can flare up and cause clinical disease.

Most problems are seen in chicks and the disease has a potential to cause significant mortalities.

These mortalities may include a high proportion of dead embryos in-shell in both the pipped and unpipped stages.

After hatching, deaths may start after 2-3 days and continue for up to 3 weeks. The chicks will look depressed, lethargic and sit in one position with 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 seen in young chicks include depression and weakness leading to death and also sudden death with few preceding signs.

In the early stages after hatching, chicks sick from paratyphoid may show similar signs to those sick from yolk sac infections.

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.

Paratyphoid will respond to antibiotic treatment. Drugs in the class nitrofurans are named in text books as the drug of choice for treatment, but these are no longer available having been withdrawn from the market.

This makes it important to consult your veterinarian regarding treatment and to get samples to a laboratory as soon as possible. If a salmonella organism is cultured then 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.

It is unlikely that salmonella paratyphoid could be eradicated from a property and it would not be worth trying.

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

This program would require strict attention to hygiene and should include:

1. Daily collection and fumigation of eggs with formaldehyde gas which should eliminate or greatly reduce contamination on the outside of the shell.
   Here it would be recommended that fumigation be used in preference to washing eggs. When eggs are washed the aim is to use a hot solution (43-49^oC) so the egg contents expand and force air and hopefully any contamination out through the pores in the shell. The egg then needs to be dried using hot air before the egg contents shrink back to normal size. Problems can occur when the egg is not dried before the contents shrink as this may then suck fluid and contamination back through the pores in the shell.
2. Washing hands or wearing disposable gloves when handling eggs. As outlined, the salmonella is passed in the faeces and from there can spread to contaminate a wide range of objects including hands.
3. Fumigate the hatcher between batches with formaldehyde, virkon (s) gas or clean with a broad spectrum egg disinfectant (eg gluteraldehydes, orthosan etc.). Make sure all fluff, dust and egg shell remains are also removed.
4. Observe chicks closely. Send samples to a laboratory if chicks start dying, are not doing well or a high proportion of dead full-term embryos in shell are seen.
5. Use strategic antibiotic treatment to control infection in chicks.
6. Where a problem is identified additional precautions could be considered:
   • regular misting of 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 fumigation of each batch of eggs just before they are put into the incubator.
   • fumigation of 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.

In summary, paratyphoid appears to be a problem that could become established on emu farms. However, attention to hygiene and strategic use of antibiotics should control the disease if it occurs.