Fowl Typhoid in Animals

Fowl Typhoid in animals is an infectious, enteric disease of adult and layer birds. The disease develops a more acute septicemic condition mainly in mature birds and more severe condition in commercial laying flocks.

Fowl typhoid in animals is often characterised by rapid spread with high morbidity and mortality.

Etiology

Salmonella gallinarum causing fowl typhoid is a gram negative, non-capsulated, non-sporogenic, non-motile, rods shaped and flagellated organism. It survives outside the host’s body for many months.

Epidemiology

Prevalence of infection

The bacterium is fairly resistant to normal climate, surviving months, but is susceptible to normal disinfectants.

Source of infection

Red mites persists in poultry houses contribute the spread of infection.
The organism is excreted in droppings.
The organism persists in faeces for a months but survive long time in the infected carcasses.
Rats, dogs, foxes and wild birds may carry infection.
Recovered birds acts as carriers for long periods.

Transmission

Fowl Typhoid is mainly a hatchery borne infection. The lateral spread through ingestion of contaminated food and water occurs.

Chronic birds remain as carrier even after treatment and may lead to re-infection.

Infection also spread through eggs laid by vaccinated birds but egg transmission is not a regular features of the disease.

Host Affected

Adult and growing birds are mostly affected with serious problems and heavy mortality. The organism also affects turkey, ducks, pheasants, guinea fowl, peafowl, grouse, quail, game birds, sparrows, parrots, canaries and bullfinches.

Pathogenesis

Infection occurs by horizontal and vertical transmission. Horizontal transmission occurs via the respiratory and oral routes.
Birds ingest the organism from the contaminated environment.
Infection also occurs by cannibalism.
Wound infections are also possible.
Salmonella Gallinarum transmitted by fomites which includes contaminated feed, water and litter; they may survive in a favorable environment for many months and up to several years.
Wild birds, mammals, and insects can act as mechanical or biological vectors.
Red mites, in particular, are involved in spreading of fowl typhoid.
Rodents acts as biological vectors.
In growing birds and adults, Salmonella Pullorum infections are likely to be inapparent.
Fowl typhoid can occur in older as well as young birds.
Occasionally, Salmonella Pullorum may cause a disease similar to fowl typhoid in older birds; The route of infection is oral or via the navel/yolk.
Morbidity is 10-100%; mortality is increased in stressed or immunocompromised flocks and may be up to 100.
In young birds, it cause septicemia which leads to systemic illness. It mainly affects, heart, kidney, liver and spleen. They become enlarged, congested and haemorrhagic.
In adult birds it causes intestinal and kidney problemss.
Reproductive system is most prominently affected.

Clinical Signs

Acute phase

Affected birds shows decreased food intake, depression, ruffled feathers, closed eyes, respiratory distress, rapid breathing, watery to mucoid, yellow color diarrhoea, pasty feathers around the vent followed by drop in production.

Birds surviving 2-3 days after the onset of acute disease may follow the chronic stage. In this stage higher mortality noticed in young chicks.

Chronic phase

There is progressive loss of condition, pronounced anaemia, shrunken, pale combs and wattles. Incubation period 4-6 days, the disease spread rapidly through the flocks and cause 50% loss.

Subacute phase

Grumbling, increased dead in shell embryos, small, weak, moribund dead and chicks may be found on the hatching trays. Mortality may occurs seldom but follows for a long period. In young birds, signs may be non-specific.

Necropsy Findings

Acute

Septicaemic and jaundice appearance of the carcasses, injected and prominent sub-cutaneous blood vessels and dark congested skeletal muscle seen.
Swollen, friable, dark red or black colored liver is observed as a constant features of the fowl typhoid and the cut surface of the liver may shows a distinct coppery bronze sheen.
Spleen may also be enlarged.
Catarrhal enteritis and the affected intestine may contains a viscous, slimy, bile stained material.
Bone marrow may become dark.

Chronic

Emaciation, intense pale carcass, greyish white focal necrosis of the myocardium, mucosa and submucosa of the initial part of the intestine, pancreas and liver may be seen.
Pericarditis, accumulation of turbid yellow fluid in the pericardial sac, fibrin attachment at the surface of the heart are characteristic for chronic fowl typhoid.
Young birds have discrete, necrotic foci in the lung and gizzard and in the testicles of cockrels noticed.
In laying birds, retained yolk with subsequent rupture may be noticed.
In Turkeys Liver exhibits bronze to mahogany color streak, necrosis of heart, greyish lungs are pathgnomonic lesions of this disease.
Crop usually contains food which suggests paralysis of digestive tract.
Mucous membrane of proventriculus sloughs off readily.
Heamorrhagic enteritis (duodenum) intestinal ulceration is remarkable.

Diagnosis

Based on clinical signs and necropsy findings.
Caecal tonsils and spleen from infected birds is given priority.
Swabs from infected tissues, intestinal and cloacal contents should be collected aseptically.
Eggs, embryos, fecal droppings and hatchery debris, fluff, dust, broken eggshells and chick box linings also be collected for the diagnosis.
Tissue samples can be cultured into selective and non selective enrichement liquid media or into agar based media (brilliant green agar) immediately following collection of samples or else, samples can be stored if there is any delay in diagnosis.
Blood testing using S.pullorum antigen in RBPT or whole blood test (WBT) can detects carriers of S.gallinarum. Positive birds based on the test should be culled. RBPT is not a reliable test in turkeys and ducks.
Antiglobulin indirect haemagglutination test detected serum antibodies in a days after oral infection.

Sample collection

Blood and Serum sample
Fecal sample
Tissues sample

Differential Diagnosis

Typhoid
Pasteurellosis
Colibacillosis
Viral diarrhoea
Parasitic infection
Mycoplasmosis

Treatment

Furazolidone in feed for 10 days at the level of 0.04%.

Use of enrofloxacin unable to completely eliminate the infection. Amoxycillin, potentiated sulponamide, tetracylines, fluoroquinolones.

Prevention

Live attenuated rough Houghton strain of 9R of S.gallinarum and Freunds complete adjuvanted vaccine can be given subcutaneously between 10-18 weeks of age found to give long lasting solid immunity and protection for up to 32 weeks Some vaccinated birds can develop hepatic and spleenic lesions without mortality.
Few birds develops antibody detectable by whole blood agglutination test.

Control

Pullorum and fowl typhoid are reportable diseases.
At the time of outbreak quarantine of birds are essential.
Monitoring of all healthy as well as infected birds are necessary.
Culling of chronically affected birds and blood test reactor birds required.
Removal and proper incineration of all dead carcasses is eassential.
The organism can be killed readily in 10 min at 60°C, by phenol 1:1000 and 1% KMnO4 in 3 min, 2% formalin in 1 minute.