Aetiology
Fowl paratyphoid is caused by Salmonella typhymurium and Salmonella enteritidis. They are gram negative flagellated and motile organisms.
Age/host range
They infect chickens, turkeys and ducks of all ages, the younger birds are more susceptible than the adult birds. The disease is worldwide in distribution.
Reservoir host
They include invertebrate, vertebrate, wildlife, domestic animals and humans. They yield to either asymptomatic or clinical disease.
Transmission
-The Horizontal transmission is via bird to bird contact, ingestion of contaminated feed and water or personnel and equipment.
-The organism is also disseminated from widelife vectors, rodents, insects and humans by contact of poultry with the faecal droppings of the vectors.
-Vertical transmission to the progeny by infected breeder flock occurs, this can result in internal or external contamination of eggs through embryo or oviposition.
The Clinical signs
Incubation period is between 1-14 days. Morbidity is 0-90% and mortality is usually low in the first two weeks of life after hatching. Contamination of salmonella in the embryo will lead to high level of embryo mortality and rapid death of newly hatched birds if it survives. There is weight loss and retarded growth.
In young birds
Signs are generally mild compared to host-specific salmonella or absent, dejection, huddling, ruffled feathers, drooping wings, anorexia and thirst, emaciation, closed eyes, vent pasting, profuse watery diarrhea and dehydration, blindness and lameness are occasionally reported.
In adult birds
Anorexia, diarrhea, reduced egg production have been reported in experimental infections.
Post-mortem lesions
In acute disease, there may be few lesions.
Spleen, kidney and liver are swollen and congested with evident necrotic foci or haemorrhagic streaks on the liver.
Fibrinopurulent perihepatitis and pericarditis
Enteritis and focal necrotic intestinal lesions
Unabsorbed yolk present in the yolk sac
Cheesy cores in caecum
Diagnosis
Tentative diagnosis is based on characteristic clinical signs and post-mortem lesions. Positive diagnosis is by isolation and recognition of the salmonella organism. Serologic test for example ELISA and plate agglutination tests can be used.
Differential diagnosis
Typhoid, enterobacteria and pullorum
Treatment
The use of sulphonamides, neomycin, tetracycline, amoxicillin and fluoroquinolones. Chemotherapy can lengthen carrier status in certain conditions.
Prevention
Use uninfected breeders in production
Fumigate eggs before hatching
Practice all-in/all-out production
Routine monitoring of breeding flocks, hatcheries and feed mills is required for effective production. Vaccination with either killed or live preparation has been found to reduce the susceptibility of paratyphoid infection.