Salmonellosis:

Syn: Fowl Paratyphoid, Avian Salmonellosis

• Avian salmonellosis is an infectious disease of poultry caused by bacteria of genus Salmonella; Family; Enterobacteriaceae
• This is one of the most common infectious diseases caused by ingesting contaminated food and water, especially meat.
• These bacteria also cause food poisoning in human, thus has got public health importance.
• It is estimated that approximately 33 million cases of human illness and 9 million deaths occur annually due to food infected with salmonella and another organism.

Etiology:

• Salmonella typhimurium is principal cause of avian salmonellosis.
• Along this bacteria, Salmonella enteritidis are also responsible for disease.
• These are gram -ve, non-motile bacteria consisting of around 2300 different strains. These strains are called serovars.
• Organism can be cultured on beef infusion agar with colony round slightly raised, smooth with diameter of 1-2 mm.
• Organism is resistant and can survive in the environment for a long time. They are killed by heat and disinfectants.
• Formaldehyde is effective in killing organism.

Epidemiology:

• Disease is distributed globally.
• Moore recorded the first confirmed case of paratyphoid from domestic poultry.
• These diseases are usually observed in young birds than mature adult birds.
• The frequency of different serotypes of Salmonella within live birds varies from 6% to 30%.
• Salmonella contamination in poultry samples has been reported worldwide, with rates of 17% in the USA, 35% in Spain, 36% in Korea, 39% in Brazil, and 53% in Vietnam.
• The general occurrence of Salmonella in white layers from commercial settings was 25.55%, with the highest seroprevalence in finisher birds (32.22%), followed by grower birds (26.66%) and starter birds (17.77%)
• typhimurim and S. enteritidis account for 41.5% of the overall epidemics and makes up nearly 60% of all the Salmonella outbursts globally.
• The peak seroprevalence occurred in the wintertime (49.07%), trailed by the fall season (25.71%), summer (18.57%), and then spring (15.38).

Transmission:

• Infection may spread in 2 ways:
  • Vertical transmission
  • Horizontal transmission
• Vertical transmission usually occurs through contaminated eggs. Infected breeding stock transmit the infection to eggs of the ovary.
• Infected eggs when hatched give rise to infected eggs.
• Horizontal transmission takes place through:
  • Infected chicks to susceptible chicks
  • Contaminated feed and water
  • Contaminated egg shell
  • Feedstuff like bone meal, blood meal, meat, etc.
  • Incubator, hatchery, carrier bird
  • Rats, mice, insects
  • Foot wears, clothes of human, attendants, visitors
  • Ingestion of fecal matter by young birds

Pathogenesis:

Clinical Findings:

• Mortality is greater than in birds of 1 week.
• Mortality rate is more in duck, turkey and pigeons over chicks.
• Birds huddle together and try to remain close to heating sources.
• Affected birds lower their head, close their eyes and drop their feather and wings.
• Anorexia but increased thirst.
• Profuse greenish loose droppings
• Due to diarrhea, there is often pasting of vents.
• Death of birds within 2-3 days due to severe dehydration.
• Adult birds show inappetence, increased thirst, diarrhea, and dehydration.

PM Findings:

• Most striking changes are observed in liver. Liver shows congestion with appearance of nodular lesion.
• Cheesy nodules may be observed on the surface of esophagus.
• Necrotic foci along with deposition of cheesy mass in lumen of intestine
• There may be presence of cecal plug.
• Arthritis of hip and knee joints.
• Yolk sac remains unabsorbed.
• Pericarditis and perihepatitis may be seen.
• Pericardial sac contains large quantity of turbid fluid containing large masses of salmonella.

Diagnosis:

• Based on history, clinical findings and PM findings
• Isolation and identification of organism through bacterial culture. Ceca is best site for isolation of bacteria.
• Serological test: whole blood test and serum agglutination test (SAT) have been used successfully.
• ELISA

Differential Diagnosis

1. Colibacillosis:

• There are often respiratory signs along with diarrhea.
• No characteristic white cecal sores present.
• Culture shows coli.

2. Fowl cholera:

• Acute septicemia with swollen wattles
• Hemorrhages on heart/liver
• Bipolar rods are shown on smear.

3. Necrotic enteritis:

• Fibrinonecrotic lesions in intestine.
• Large gram-positive rods are shown in smear.

4. Coccidiosis:

• Bloody or mucoid diarrhea
• Oocyst are detected on fecal exam

Treatment

• Drugs like nitrofurazone, sulphonamides, cotrimoxazole are used.
• Furazolidine @ 0.022% is given in feed.
• Treatment usually donot eliminate infection. So, aim should be made at preventing and controlling the disease.

Control Measures:

• A good hygienic and sanitation measures are to be adopted.
• Fumigation of the incubator should be made.
• Vitamin A may be supplemented to enhance resistance.
• Sewage should be treated properly to prevent multiplication of the organism.
• Wetland of the farm premises should be properly maintained to avoid spread of infection from wild bird population.
• Inapparent carrier birds should be screened serologically and avoided for breeding.
• Manure from poultry houses should be disposed of properly.
• Contaminated feed and water should be discarded and disposed of properly.
• Entry of visitors to poultry farm should be restricted.
• Dead birds are disposed of properly with lime powder.
• Eggs should be treated with disinfectants prior to incubation. Eggs may be dipped in 1% zinc sulphate solution or Savlon.
• Eggs should be brought under radiation.