E coli...a millennium bug

E.coli is a bacterium and is a normal inhabitant of a healthy bird's intestines. It belongs to the family of bacteria which also includes Salmonella, Proteus, Citrobacter, Shigella and Klebsiella. All these bacteria have an affinity for living in animal intestines. As a result, they are disseminated widely in the environment via poultry litter, faeces, washing from houses etc, ie in any material contaminated with faeces.

Diseases caused by E.coli:

There are lots of different types of E.coli strains (serotypes), some more invasive and pathogenic than others. The most common disease causing serotype is called 078:K80. Diseases caused by E.coli are usually termed colibacillosis. This includes:

· Coli septicaemia.

· Peritonitis.

· Yolk sac infections.

· Coli granulomata (Hjarres disease).

1. Coli septicaemia:

This is the most important manifestation of E.coli infection especially in broilers but can also be seen in layers during rear as a cause of mortality or associated with egg peritonitis.

Septicaemia is blood poisoning, ie there are actively multiplying E.coli bugs in the bloodstream. All the post mortem lesions seen are caused by the toxins that the E.coli produces in the blood, damaging tissues. E.coli enter the blood from the intestines, throat or trachea where they may be sitting harmlessly. They need a precipitating factor to cause damage to the lining of the throat, trachea or intestines to allow the E.coli to invade. In the respiratory tract, this may be high ammonia, dust or relative humidity, or infectious agents such as Mycoplasma or viruses, eg Infectious Bronchitis, Newcastle disease, TRT. In the intestine, this may be direct damage caused by coccidiosis, digestive upset due to nutritional problems or occasionally worm burdens. E.coli from all sites is more likely to gain entry when the birds' immune system is damaged. This may be non specific in sick birds or a direct effect on the immune system such as caused by Gumboro disease, and, on occasions, mycotoxins.

Control of E coli invasion is mainly by prevention of upsetting the balance between the bird and its normal E.coli population. This requires maintenance of good environmental conditions (litter and atmosphere), reducing "stress" and reducing exposure to precipitating disease agents or immunosuppressive agents by effective biosecurity.

E.coli infections can be treated via the drinking water or feed depending on sensitivity data. Your veterinary surgeon can assist in this.

2. Egg peritonitis:

This occurs in stressed flocks as discussed in our article on Egg Peritonitis in The Ranger last year. It frequently effects birds coming into lay especially if the onset of egg production is very sudden. There may be hormonal stress at this time. Certain stresses, eg foxes gaining access to the flock, sudden feed or water depravation, sudden feed change, or sudden onset of disease may interfere with the normal peristaltic wave which moves the egg down the oviduct. Birds are then also more likely to strain causing slight prolapse and vent pecking. These upsets allow bacteria to move up the oviduct into the abdomen causing peritonitis or allow invasion of strains being carried in the gut via the bloodstream to the air sacs, ovary or peritoneum. Again, infectious agents such as Infectious Bronchitis may allow coli penetration into the birds.

Control and treatment were discussed in our previous article on the subject but the aim is to reduce the physical infectious stresses on the bird. Antibiotic treatment via the feed during stressful periods may be helpful in prevention and water treatment may be necessary in severe cases.

3. Yolk sac infection:

This is so called mushy chick disease (or the more technical term of omphalitis). E.coli gains access via unhealed navels in the hatchery or via bacterial penetration of the unhatched egg. Either way, infection is usually caused by poor egg hygiene allowing high bug load on the shell and underlining shell membrane, especially cracked or thin shelled eggs. Control is therefore obviously by better attention to egg collecting, egg handling and egg sanitisation and good hygienic practices in the hatchery. Unfortunately treatment is seldom effective with affected birds dying out in the first week.

4. Coli granulomota (Hjarres disease):

This is usually seen as sporadic nodular lumps and bumps on the gut wall in free range hens due to local invasion of E.coli. This is seldom a flock problem but may be seen secondary to gut damage such as that caused by heavy worm infestations.

Conclusions

· E.coli is ubiquitous being spread via faecal contamination. It is all around us.

· E.coli is the ultimate opportunist waiting for the equilibrium between bug and bird to be tipped in favour of bacterial proliferation and penetration.

· E.coli requires precipitating assistance from adverse environmental, managemental, physiological or infectious factors.

· E.coli can be easily spread via the drinking water and therefore effective water sanitisation goes a long way to reducing spread of the organism.

· E.coli can be treated with selective targeted antibiotic use.

· E.coli will always be with us. The answer to the science is never to allow it to get the upper hand.