Colibacillosis

Colibacillosis

Dr. Salah M. Hassan, BVMS, MSC, PHD
College of Veterinary Medicine
University of Mosul

Definition

Colibacillosis refers to any localized or systemic infection caused entirely or partly by avian pathogenic Escherichia coli including:
Colisepticemia
Coligranuloma ( Hjarre’s disease )
Air sac disease ( chronic respiratory disease, CRD )

Swolen – head syndrome

Venereal colibacillosis
Coliform cellulitis ( inflammatory process )
Peritonitis
Salpingitis
Orchitis
Osteomyelitis/ synovitis ( turkey osteomyelitis complex )
Panophthalmitis
Omphalitis/ yolk sac infection
Enteritis


Colibacillosis in mammals is most often a primary enteric or urinary tract disease,
whereas colibacillosis in poultry is typically a localized or systemic disease occurring secondarily when host defenses have been impaired or overwhelmed by virulent E. coli strains.

Strains of E. coli that cause disease outside the intestinal tract of any species share common characteristics and are called extraintestinal pathogenic E. coli (ExPEC).

Most APEC are ExPEC and share characteristics with mammalian ExPEC.

Etiology
The etiology of colibacillosis is Escherichia coli. Other infectious agents and noninfectious factors usually predispose a bird to infection or contribute to the severity of the disease.
Escherichia is the type genus of the family Enterobacteriaceae, which is composed of organisms that can grow aerobically or anaerobically and utilize simple carbon and nitrogen sources
Gram-negative , Rod (bacillus) shape, Non-spore-forming, on MacConkey agar.

Incidence and Distribution

E. coli likely occur in most mammals and birds although healthy psittacines may be an exception.
It is a common inhabitant in the intestinal tracts of poultry at concentrations up to 106 E. coli/gram of intestinal contents.
Higher numbers are found in younger birds, birds
without an established normal flora, and in the lower intestinal tract.
Among normal chickens, 10–15% of intestinal coliforms may belong to potentially pathogenic serotypes although intestinal strains may not be the same serotype as those from extra-intestinal sites in the same bird

Egg transmission of pathogenic E. coli is common and can be responsible for high chick mortality.
Pathogenic coliforms are more frequent in the intestine of newly hatched chicks than in the eggs from which they hatched, suggesting rapid spread after hatching.
The most important source of egg infection seems to be fecal contamination of the egg surface with subsequent penetration of the shell and membranes.
Coliform bacteria can be found in litter and fecal matter.
Dust in poultry houses may contain 105–106 E. coli/g.


Age of Host Commonly Affected
All ages are susceptible to colibacillosis, but young birds are more frequently affected and severity of disease is greater in young birds,
including developing embryos.
Outbreaks can occur in caged layers and coliform salpingitis/peritonitis is a common cause of mortality in breeders.

Host Susceptibility Factors

Normal, healthy birds with intact defenses are remarkably resistant to naturally occurring E. coli exposure including virulent strains.
Infection occurs when skin or mucosal barriers are compromised (e.g., unhealed navel, wounds, mucosal damage from viral, bacterial, or parasitic infections, lack of normal flora, etc.).
The mononuclear-phagocytic system is impaired (e.g., viral infections, toxins, nutritional deficiencies)
There is immunosuppression (e.g., viral infections, toxins)
Exposure is overwhelming (e.g., environmental contamination, poor ventilation, contaminated water ).
And/or birds are exposed to abnormal stress or have an inappropriate response to stress

Incubation Period

The time between infection and onset of clinical signs varies with the specific type of disease produced by E. coli.
The incubation period is short, generally between 1 and 3 days, in experimental studies in which birds are exposed to high numbers of virulent organisms.
In the field it is more common to see colisepticemia 5–7 days after infection with a predisposing agent such as infectious bronchitis virus in chickens or hemorrhagic enteritis virus in turkeys.

Clinical Signs

Clinical signs vary from inapparent to total unresponsiveness just prior to death depending on the specific type of disease produced by E. coli.
Localized infections generally result in fewer and milder clinical signs than systemic diseases.
Coliform cellulitis is typically not detected until the birds are processed.
Lameness and retarded growth are seen in birds with skeletal lesions that develop as a sequel to sepsis.
When joints or bones of one leg are affected, birds walk with a characteristic hopping motion to keep weight off of the affected leg.


When the thoracolumbar spine is affected, the birds have an arched back, sit on their hocks, and bear little or no weight on their feet.
Birds with chronic lameness have caking of droppings around the vent and on abdominal feathers. Feces are green with white to yellow urates as a result of anorexia and dehydration.
Young birds with omphalitis and infected yolk sacs also may have difficulty in walking because of abdominal distention, which alters weight distribution and impairs balance.
Birds with colisepticemia are often terminally moribund and the flock may be inactive and not eating.

Decreased water consumption is associated with a poor prognosis.

Severely affected individual birds are unresponsive when approached, do not react to stimuli, and are easily caught and handled.
They sit with their eyes closed in a hunched position with drooping of the head, neck, and wings.
The beak may be inserted into the litter to support the head.

Morbidity and Mortality

Both morbidity and mortality are highly variable depending on the type of disease produced by E. coli.
It is probable that most, if not all, commercial flocks experience some degree of morbidity, mortality, or condemnation due to E. coli infections.
Mortality occurring during the day indicates a more severe disease outbreak than when birds are only found dead in the morning.
A flock that appears clinically normal when examined during the day, but has an excess number of dead birds the following morning, is a common finding in mildly affected flocks.
This pattern is typical for egg layer and breeder flocks experiencing coliform salpingitis/peritonitis.

Localized Forms of ColibacillosisColiform Omphalitis/Yolk Sac Infection

Omphalitis is an inflammation of the navel (umbilicus).
In birds the yolk sac is usually involved too because of its close anatomic relationship.
Infection follows contamination of the unhealed navel with APEC. Fecal contamination of eggs is considered to be the most important source of infection.
Bacteria may be acquired in ovo if the hen has oophoritis or salpingitis or via contamination following artificial insemination.
Yolk sac infections also can result from translocation of bacteria from the chick’s intestine or from the bloodstream. In these cases the navel is not affected.

Omphalitis

Yolk sac infection

Some embryos may die before hatching, particularly late in incubation; whereas others die at or shortly after hatching.
Surviving infected chicks can be a source of E. coli for other chicks in the same hatch.
The incidence of birds with omphalitis increases after hatching and declines after about 6 days with occasional
losses continuing up to 3 weeks.
When birds become infected with low virulent strains there may be no embryo or chick mortality or some may survive although hatchability, chick livability, and relative yolk weights may be affected ; the only pathologic finding being retention of infected yolk sacs containing caseated yolk.

Swelling, edema, redness, and possibly small abscesses characterize acute inflammation of the navel.
The abdomen is distended and blood vessels are hyperemic.
In severe cases the body wall and overlying skin undergo lysis and are wet and dirty. These birds are referred to as “mushy” chicks or poults.
There may be other nonspecific changes such as dehydration, visceral gout, emaciation, vent pasting, and enlarged gall bladder.
The yolk sac is typically distended because yolk has not been absorbed and inflammatory products have been added. Yolk is abnormal in color, consistency, and smell, and may contain visible exudate. Blood vessels of the yolk sac are often prominent


Chicks or poults with infected yolk sacs that live more than 4 days also may have pericarditis or perihepatitis, indicating systemic spread of the organism from the yolk sac.
Consequences of yolk sac infection include deprivation of nutrients and maternal antibodies, absorption of toxins, and spread of E. coli by extension into the body cavity or systemically to produce colisepticemia.
Survivors are usually stunted and do poorly.

Coliform

Cellulitis

Swollen Head Syndrome

Swollen head syndrome (SHS) is an acute to subacute cellulitis involving the periorbital and adjacent subcutaneous tissues of the head
Swelling of the head is caused by inflammatory exudate beneath the skin that accumulates in response to bacteria, usually E. coli, following upper respiratory viral infections (e.g. avian pneumovirus, infectious bronchitis virus).
Ammonia aggravates the disease.


Swollen Head Syndrome

Diarrheal Disease.

Primary enteritis is a common manifestation of E. coli infections in mammals including human beings, but is considered rare in poultry.
Intestinal E. coli in poultry have been poorly studied, so our knowledge of the role that E. coli may play in intestinal disease is limited.

Coliform Salpingitis/Peritonitis/Salpingoperitonitis

Inflammation of the oviduct caused by E. coli results in decreased egg production and sporadic mortality.
It is one of the most common causes of mortality in commercial layer and breeder chickens.
Accumulations of caseating exudate in the body cavity resemble coagulated yolk, which is the reason for the common name “egg peritonitis.”
Salpingitis and egg binding may occur concurrently.
They are often confused with each other because they both result in an obstructive mass within the oviduct.
Yolk peritonitis is a mild to moderate diffuse peritonitis that results from free yolk in the body cavity.

Coliform Orchitis/Epididymitis/Epididymo-orchitis

An ascending E. coli infection of the male reproductive tract, analogous to that resulting in salpingitis in the hen, occurs infrequently in roosters.
Testicles are swollen, firm, inflamed, irregularly shaped,
and have a mosaic of necrotic and viable tissue when opened.


Systemic Forms of Colibacillosis Colisepticemia
Presence of virulent E. coli in the blood stream defines colisepticemia.
Characteristic features of colisepticemia at necropsy are tissues that develop a green discoloration following exposure to air and a characteristic odor, possibly related to indole produced by the organism.
The bursa of Fabricius is often atrophic or inflamed as a result of colisepticemia.
Pericarditis is common and is a characteristic of colisepticemia. It is usually associated with myocarditis.
Vessels in the pericardium become increasingly prominent because of hyperemia and the pericardium becomes cloudy and edematous.

Initially fluid and soft masses of pale exudate accumulate within the pericardial sac followed by fibrinous exudate.
As the disease progresses exudate increases, becomes more cellular (fibrinoheterophilic), and undergoes caseation.
The pericardial sac adheres to the epicardium with chronicity.












Respiratory-Origin Colisepticemia
E. coli gains access to the circulation following damage to the respiratory mucosa by infectious or noninfectious agents.
Infectious bronchitis virus (IBV) and Newcastle disease virus (NDV), including vaccine strains, mycoplasmas, and ammonia, are the most common predisposing agents.
Severity of the resulting disease, which is commonly referred to as air sac disease, chronic respiratory disease (CRD), or multicausal respiratory disease , is directly related to the number of agents that are involved.

Lesions are prominent in respiratory tissues (trachea, lungs, air sacs), pericardial sac, and peritoneal cavities and are typical of the subacute polyserositis stage of colibacillosis.
Infected air sacs are thickened and often have caseous exudate on the respiratory surface.

Enteric-Origin Colisepticemia

Enteric-origin colisepticemia is most common in turkeys.
E. coli gain access to the circulation and tissues following damage to the intestinal mucosa by infectious agents.
The most common predisposing agent is hemorrhagic enteritis virus.
Lesions are typical of the acute septicemic stage of colibacillosis. Affected birds are in good physical condition and often have full crops containing feed and water.
The most characteristic lesions are congestion or green discoloration of the liver, marked enlargement and congestion of the spleen, and congested muscles.








Neonatal Colisepticemia
Chicks are affected within the first 24–48 hours after hatching.
Mortality remains elevated for 2–3 weeks and usually totals 10–20%. Up to 5% of the flock may be stunted and require culling.
Unaffected birds grow normally and the disease does not appear to spread.
Initial lesions consist of congested lungs, edematous serous membranes, and splenomegaly.
The proventriculus and lungs develop a dark color that
can approach black as the interval between death and necropsy increases.

Layer Colisepticemia.

Colisepticemia is usually a disease of young birds, but occasional outbreaks of acute E. coli infection resembling fowl typhoid or fowl cholera occur in mature chickens and turkeys.
Acute colibacillosis in layers is being seen with increasing frequency. The majority of outbreaks are associated with onset of egg production, but less frequently they occur at an older age, or may continue as the flock ages and potentially spread to older flocks on the same farm.
Death usually occurred suddenly without premonitory signs although depression and/or dirty vents were observed in some affected hens in approximately half of the flocks.

Weekly mortality was significantly higher in affected flocks than age-matched control flocks (0.26–1.71% vs. 0.07-0.30 %).
Cumulative mortality ranged up to 10% and mortality
remained elevated for 3–10 weeks.
Polyserositis (perihepatitis, pericarditis) and peritonitis associated with free yolk in the peritoneal cavity were present in most birds at necropsy.
Oophoritis and salpingitis occurred less frequently.
The pathogenesis of the disease is unknown, but stress associated with onset of egg production is believed to be an important contributing factor.


Panophthalmitis.
Involvement of the eye is uncommon, However, if it is infected the resulting panophthalmitis is severe.
Typically there is hypopyon and hyphema, and infection is unilateral. The eye is swollen, cloudy to opaque, and may be hyperemic initially. Later the eye shrinks as it undergoes atrophy.
Fibrinoheterophilic exudate and numerous bacterial colonies are present throughout the eye. Inflammation, especially adjacent to necrotic tissue, becomes granulomatous with time. Varying degrees of retinal detachment, retinal atrophy, and lysis of the lens also may be seen.

Coligranuloma (Hjarre’s Disease).

Coligranuloma of chickens and turkeys is characterized by multiple granulomas in liver, ceca, duodenum, and mesentery, but not spleen.
Coligranuloma is an uncommon form of systemic colibacillosis that usually occurs sporadically in individual birds, but can cause mortality as high as 75% when a flock is affected.
Serosal lesions resemble leukosis tumors.









Diagnosis
Isolation and Identification of Causative Agent

Differential Diagnosis

Acute septicemic diseases may result from pasteurellae, salmonellae, streptococci, and other organisms.
Chlamydiophila, pasteurellae (Pasteurella, Ornithobacterium, Riemerella), or streptococci (Streptococcus, Enterococcus) sometimes cause pericarditis or peritonitis and other bacteria, mycoplasmas, and Chlamydiophila can cause airsacculitis.

Treatment

Antimicrobial Drugs
When selecting an antimicrobial to use for treatment, it is important to determine the susceptibility of the isolate involved in the disease outbreak so that ineffective drugs can be avoided.
Even a highly effective drug may not result in improvement of the flock if too little is used or it is incapable of reaching the site of infection. Therefore, underdosing may promote development of resistance.

Other Treatments

The declining use of antibiotics for prevention and treatment of colibacillosis has stimulated interest in alternative methods including prebiotics, probiotics, enzymes, digestive acidifiers, vitamins, immune enhancers, anti-inflammatory drugs, and other antimicrobial products.
Essential oils often have substantial inhibitory effect on E. coli in vitro and in the lower intestinal tract of chickens.