E.coli infection of baby chicks (yolk. Sac infection , mushy chick disease, omphalitis)
Early chick mortality may occur due to E.coli infection in which the mortality increases in the first few days of ages. Infection occurs from egg shell contamination or open navel.
Yolk sac infection can cause 100 % mortality in a batch of chicks in the first week of life PM. exarnination reveals septicemic picture, pericarditis, unhsorbed yolk sac. Yolk of abnormal color (brownish green) and consistency (watery or inspissated) and often of fetid odor.
Recovered birds become uneven Incidence of omphalitis increases with decreased humidity at incubation , low brooding temperature and fasting .E.coli multiplies rapidly in the intestine of newly hatched chicks and infection spreads rapidly from chick to chick in the hatchery and brooders 70 % of omphalitis cases are due to E.coli . other organisms incriminated for omphalitis either alone or with E.coli andē include salmonella , staph , proteus , pseudomonas, clostridia and bacillus cereus .
Salpingitis and egg peritonitis
Occur in laying birds usually at the onset of laying . high estrogenic activity seems to be associated with coliform growth in the oviduct. inflammation of the oviduct follows the infection of the obdominal air sacs or ascending from the cloaca
Birds appear pale, emaciated, with distended abdomen and drop in egg production, mortality seems to be unavoidable 1 % a month.
Lesions: abdominal cavity contains egg material, inspissated yolk, caseous material or milky fluid with inflammation and distortion of the ovary.
Accumulation of egg material in the oviduct forming a core of inspissated inflammatory debris which may lead to rupture of the oviduct wall .A whole or partly formed egg may be impacted in the oviduct. Pritonitis with adhesions of internal organs may occur & salpingitis must be differentiated from that caused by mycoplasma.
Chronic respiratory disease
Slowly progressive disease caused by E.coli. Maximum incidence at 5-12 weeks age.
Signs: respiratory signs of varying degree of severity that is more pronounced in 3- 8 week broiler.
Adults suffer from poor food conversion & drop in egg production but low mortality.
Lesions: opaque air sacs, fibrinopurulent exudates on air sacs, liver and heart, catarrhal inflammation of the upper respiratory tract
N. B. E.coli usually complicates air sac infection by mycoplasma complicated CRD.
Coligranuloma (Hjarreís disease)
Itís a chronic granulomatous condition caused by E.coli in adult birds especially fowls and turkeys This condition is rare, sporadic and manifested by depression, loss of condition, anemia and paleness PM. Examination reveals hard yellow nodules on the serosal surface of intestine, ceci , liver and mesentry .Nodules vary from small circumscribed to large masses . Liver may be hard, blotchy, discolored and swollen There is no effective treatment or control and must be differentiated from nodules caused by salmonella, T. B. , tapeworms & tumors
Occur in young birds usually following septicemia and characterized by lameness and swelling of the joint (usually the hock) with inflammatory signs.
May recover in a weekor progress in chronicity Must be diferentiated from arthritis caused by salmonella, mycoplasma , T. B. ,staph , pasteurefla and reovirus.
Uncommon , usually unilateral ,follow septicemia
Infection is localized in the eye and conjunctiva
Caseous exudates accumulates in the eye chambers leading to blindness & hypopyon.
Catarrhal enteritis . catarrhal exudale fills the intestinal lumen congestion and hemorrhagic spots . should be differentiated from coccidiosis
Swollen head syndrome
E.coli is incriminated in most cases of edema and swelling of the head and nasal sinuses of broilers , broiler breeder and commercial layers although other agent may attribute in it
Cellulitis (sometimes called necrotic dermatitis) of the lower abdomen below the vent and the thighs of broilers results in considerable economic loss through condemnation or downgrading of carcasses, serotypes 01, 02 ,and 078 are usually isolated but other bacteria are sometimes recovered.
Diagnosis of E.coli infections
1- History, signs & lesions
2- laboratory diagnosis
(A) Isolation and identification of the causative agent:
unless the carcass examined immediately after death , the significance of E.coli may be difficult to determine because the organism is a frequent and rapid contaminant Samples are collected from heart blood , liver joint and pericardium or yolk and cultured on broth or agar of EMB, Macconkey, blood agar or nutrient agar and incubated at 37 C for 24 - 48 hrs.
E. coli can be identified by: colony morphology.
Films from colonies gram ó ve. Bacilli.
Motility test Biochemical reactions
(B) Serological identification:
Slide agglutination, precipitation test, tube agglutination, & fluorescent techniques.
Detection of carriers serologically is impossible due to the complexity and plurality of the organism.
Serological tests are valuable only in epidemiological investigations not in routine diagnosis because:
donít distinguish E. Coli infection from fecal contamination
there are probably many pathogenic E. coil strains which donít belong to known serotypes (undistinguishabie strains).
(C) Bird inoculation:
If the pathogenicity is questionable, 0.1 ml of overnight broth culture is inoculated in chicken less than 4 weeks age death occurs within 72 hr with the characteristic lesions especially pericarditis.
Culture isolated from embryos or early deaths can be inoculated in the yolk sac of ore day old chick death within 72 hr, omphalitis, pericarditis.
Colisepticemia; ND, Al, pasteurella & other septicemic diseases.
Pericarditis, perihepatitis & air sacculitis ;mycoplasma,chiamydia, pasteurella, staph, strept.
Coligranuloma : T.B, tapeworm , salmonella, tumors Salpingitis : mycoplasma gallisepticum Arthritis : salmonella , mycoplasma , pasteurella , T.B, staph reovirus
Must be done after sensitivity test to choose the most suitable drugs to reduce the severity and mortality before the result of sensitivity test itís necessary to start treatment for 5 days.
E. coli may be sensitive to quinolones, streptomycin , ampicillin neomycin , chloramphenicol , tetracyclines, nalidixic acid and sulfonamides Mono or multiresistance may occur due to transformation transduction and sexual recombination Competitive exclusion by lactocacilli has given promising results
Prevention and control
sanitation and sound management.
chicks must be from a source free from mycoplasma and this is the most important factor, also have been vaccinated against IBD , IB ND and any other disease that is a local threat.
cleaning and disinfection of equipments
suitable temperature and humidity
good ventilation; avoid pockets of stagnant and build-up of ammonia fumes.
cleaning and disinfection of houses between floks.
avoid contamination of food and water with good feeding
eradication of rodents.
good litter hygiene and management; it must be kept dry but not dusty.
avoid stress factors especially MG infection
hatching egg saniation clean source, fecal contamination of the egg may result in the penetration of E. coil through the shell and it has been estimated that in some cases 0.5 -6 % of eggs may contain the organism , frequent collection , exclusion of dirty eggs, cleaning, disinfection and fumigation of eggs, boxes, incubators and hatcheries.
successful trials with oil ó emulsified multivalent vaccines and other types of vaccine