E.. coli Infection (Colibacillosis) in Poultry

Escherichia coli infection or colibacillosis is the most common, the most widely prevalent, and

economically the most important bacterial disease of poultry in our country. It may be seen right from

the day-old chick as yolk sac infection up to the adult bird as egg peritonitis. It occurs throughout

the year. Collectively, infections caused by f. coli are responsible for huge economic losses to poultry farmers.

Cause

A bacterium called Escherichia coli. E. coli normally lives in the digestive tract of birds, but most types (strains)

do not produce disease. Certain strains, however, can cause disease in poultry. These diseases include blood

infection (colisepticaemia) and yolk sac infection in young chickens, and egg peritonitis (inflammation

of the peritoneum, a membrane in the abdominal cavity) in adult chickens. All the conditions are collectively

called 'Colibacillosis'.

E. coli causes disease only when there is a serious managemental fault, or some other underlying diseaseproducing

organism like Mycoplasma is present. Thus, f. coli infection occurs when bird's defences have

been damaged or defeated.

I. Yolk Sac Infection

Yolk sac infection is the commonest cause of mortality in chicks during the first week after hatching (early

chick mortality). Faecal contamination of the eggs is the most important source of infection. Bacteria can

grow in the hatching egg after entering the shell. Other sources may be infection of the ovary and inflammation

of the oviduct (salpingitis). The incidence of infection increases soon after hatching and decreases after about 6

days. E. coli enters through the unhealed navel. Yolk of chicks is the site of infection. Yolk sac infection can

cause up to 100% mortality in chicks during the first week of life, but deaths are usually between 5 to 10%.

Symptoms

Affected chicks are depressed, have swollen abdomens, and show a tendency to crowd together.

Postmortem Findings

The yolk sac blood vessels are dilated and filled with blood (Fig. 46, 49). The lungs are congested and the

liver and kidneys are dark and swollen. The most important finding is an inflamed unabsorbed yolk, the yolk

being abnormal in colour and consistency (Fig. 47, 48, 50). It is usually very foul-smelling. Peritonitis and

haemorrhages on the surface of intestine are most common.

2. Blood Infection (Colisepticaemia)

Blood infection is most common in young chickens, and is a very serious form of f. coli infection.

Sources of infection

I . Through inhalation of f. coli contaminated dust via the respiratory tract. This is the most important

source of infection.

2. Through ingestion of contaminated drinking water and feed.

3. E. coli can be found in litter and faecal matter. Dust in poultry houses may contain between one lakh to

ten lakhs E. coli per gram. The bacteria persist for long periods, particularly when dust is dry.

4. E. coli can also be introduced into the poultry flocks through contaminated well water.

Predisposing Factors

These are those factors which make the bird easily prone to infection, and include:

I. Contaminated water

2. Dry, dusty conditions. E. coli persist for long periods outside the bird 's body in dry, dusty conditions.

3. Overcrowding

4. Poor ventilation

5. Poor litter condition

6. Exposure to ammonia

7. Temperature extremes (too hot or too cold)

8. Stress

9. Feed/water restriction

10. Immunosuppression: Certain factors cause immunosuppression. That is, they suppress the natural immune responses. The bird is therefore unable to fight E. coli and succumbs to infection. For example, viral infections and toxins, such as mycotoxins, cause immunosuppression and predispose the birds to coli bacillosis.

Postmortem Findings

I. A layer of white fibrin covers heart (pericarditis) and liver (perihepatitis). This is typical of blood infection

by E. coli (Fig. 5 I, 52, 53, 54, 55, 56, 57, 58, 59, 60).

2. Infected airsacs are thickened and usually contain cheese-like material.

3. Rarely, in certain cases, liver presents a corn meal appearance. That is, it appears as if ground maize has been sprinkled on its surface.

3. Egg Peritonitis

Egg peritonitis is inflammation of the peritoneum caused by the presence of a broken egg in the abdominal cavity. Postmortem findings include the presence of scattered pieces of yolk, thickened yolk, cheese-like material, or milky fluid in the abdominal cavity . Almost always a profuse growth of E. coli can be isolated from the caseous inspissated material in such cases. There is also inflammation of the ovaries and oviduct. A complete, or partially formed egg, may be found impacted in the oviduct.

Diagnosis

All the three conditions, namely, yolk sac infection, colisepticaemia, and egg peritonitis can be easily

diagnosed from the characteristic postmortem findings.

Treatment

Any treatment must begin with a complete sanitation programme as most E. coli infections start with dirty surroundings and various envi ronmental stresses. Broad-spectrum antibiotics (chloramphenicol, chlortetracycline, neomycin, nitrofurans, gentamicin, oxytetracycline, en rofloxacin, and others) may be helpful in treating the conditions. An antibiotic sensitivity test is essential in identifying the best drug to use in a treatment programme.

Control

I. Maintain the highest standards of management and sanitation.
2. Avoid overcrowding.
3. Avoid dry, dusty conditions.
4. Provide adequate ventilation in the poultry house.
5. Avoid build-up of ammonia.
6. Maintain proper litter conditions.
7. Protect the birds against extremes of temperature, heat or cold.
8. Ensure supply of clean water. Also use water sanitizers. Contaminated water can contain organisms in high numbers.
9. To prevent yolk sac infection and early chick mortality, provide the best possible brooding conditions.
10. Provide well-balanced diet to avoid mineral deficiencies and malnutrition. Ensure a supply of high protein, vitamin A, vitamin E, vitamin C, and zinc.
I I. Provide probiotic in the very first drinking water given to chicks and continue to use it for at least a week, and thereafter in the feed.