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Professional Version

Paratyphoid Infections in Poultry


Sherrill Davison Yeakel

, VMD, DACPV, Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania

Reviewed/Revised Oct 2019 | Modified Oct 2022
Topic Resources

Paratyphoid infections caused by non-host-adapted Salmonella are of public health significance because of contamination and mishandling of poultry products. S enterica Enteritidis is a major food safety concern in the egg-laying industry. Fecal contamination of the eggshell is the main mode of transmission from breeders to progeny, although S enterica Enteritidis is also transovarially transmitted.

Etiology of Paratyphoid Infections in Poultry

Paratyphoid infections can be caused by any one of the many non-host-adapted salmonellae. These Salmonella infect many types of birds, mammals, reptiles, and insects. Paratyphoid infections are of public health significance via contamination and mishandling of poultry products. S enterica Typhimurium, S enterica Enteritidis, S enterica Kentucky, andS enterica Heidelberg are among the most common Salmonella infections in poultry. Some serotypes are more pathogenic than others. The prevalence of other species varies widely by geographic location.

Transmission usually occurs horizontally from infected birds, contaminated environments, or infected rodents. Except for S enterica Enteritidis and S enterica Arizonae, transmission of most serotypes to progeny from infected breeders is mainly through fecal contamination of the eggshell. S enterica Enteritidis and S enterica Arizonae can infect the interior of the egg through transovarial transmission. Infected birds remain carriers.

Clinical Findings and Lesions of Paratyphoid Infections in Poultry

Clinical signs of paratyphoid infection are seen in young birds, but clinical disease is not usually found in mature poultry. Mortality in young birds is most often limited to the first few weeks of age.

Although these clinical signs are not distinctive, hallmarks of the disease include:.

  • depression

  • poor growth

  • weakness

  • diarrhea

  • dehydration

S enterica Enteritidis may cause decrease in feed consumption, diarrhea and a decrease in egg production in layers.

Lesions in young birds may include an enlarged liver with focal necrosis, unabsorbed yolk sac, enteritis with necrotic lesions in the mucosa, and cecal cores. Infections occasionally localize in the eye or synovial tissues. Conversely, there may be no lesions due to acute death caused by septicemia. Isolation, identification, and serotyping of the causal agent are essential for diagnosis. Serology is not highly reliable.

Treatment and Control of Paratyphoid Infections in Poultry

  • Antibiotic use is not recommended, so control relies on biosecurity and may also include vaccination.

Control measures for paratyphoid Salmonella include sanitation in the hatchery and poultry houses; elimination of vectors such as wild birds, rodents, pets, and flies; feed management; vaccination; and use of competitive exclusion products. Due to transovarial transmission of S enterica Enteritidis, additional control measures include depopulation of infected breeder flocks and refrigeration of eggs. Complete protection is not afforded by vaccination, and it should be used in combination with other control measures to reduce the incidence of Salmonella infection.

Antibiotic use is not recommended. Several antibacterial agents help prevent mortality but cannot eliminate flock infection and may lead to drug resistance.

S enterica Enteritidis (a paratyphoid Salmonella serotype) is a major food safety concern, primarily for the egg-laying industry. Possible sources in commercial layers include transmission from breeders, contaminated environments, infected rodents, and contaminated feed. Transmission to progeny from breeders is mainly through eggshell contamination, although, unlike other paratyphoid Salmonella, transovarial transmission may also occur. The National Poultry Improvement Plan includes S enterica Enteritidis control measures in breeders, including depopulation of infected breeder flocks, cleaning and disinfection of pullet and layer houses, rodent control programs, pest management, feed management, use of competitive exclusion products, vaccination, biosecurity, and proper handling and refrigeration of eggs.

Key Points

  • Paratyphoid infections are of public health concern and have been associated with foodborne disease outbreaks. S enterica Enteritidis is a major food safety concern for the egg-laying industry. Control measures for S enterica Enteritidis are outlined in the National Poultry Improvement Plan.

  • Clinical signs, including weakness, poor growth, and diarrhea, are primarily seen in infected birds during the first few weeks of age. Lesions in young birds include enlarged livers with necrotic areas, yolk sac enlargement, enteritis, and cecal cores.

  • Control measures focus on breeders, hatcheries, and poultry houses and include sanitation, pest control, feed management, competitive exclusion products, and vaccination.

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