Erysipelothrix rhusiopathiae Erysipelas in Turkeys and Poultry: Etiology, Clinical Pathology, Diagnostics, and Control

Etiology and Taxonomy

The genus Erysipelothrix comprises Gram-positive, facultatively anaerobic, slender, pleomorphic rods that produce alpha-hemolysis on blood agar. The primary pathogen within the genus is Erysipelothrix rhusiopathiae, the causative agent of erysipelas in a wide range of avian and mammalian species [1]. The bacterium possesses a characteristic filamentous growth pattern in older cultures and produces hydrogen sulfide in triple sugar iron agar, a feature used for preliminary identification. A second species, Erysipelothrix tonsillarum, is generally considered non-pathogenic for poultry, although serological cross-reactivity can complicate diagnostics [1, 2].

The pathogenicity of E. rhusiopathiae is mediated by several virulence factors, including a neuraminidase (sialidase) that degrades host cell surface glycoproteins, a hyaluronidase that facilitates tissue invasion, and a surface polysaccharide capsule that confers resistance to phagocytosis [1]. The bacterium survives for months in organic matter, soil, and water, contributing to its persistence in poultry environments.

Erysipelothrix rhusiopathiae Erysipelas in Turkeys and Poultry: Epidemiology

Erysipelas is historically significant in turkeys (Meleagris gallopavo), in which the disease manifests as an acute septicemic illness with high mortality. Turkeys are the most susceptible domestic poultry species, although outbreaks have been documented in chickens, ducks, geese, and game birds [3, 4, 5]. The bacterium is shed in feces, urine, and oronasal secretions from infected birds, and transmission occurs via oral ingestion, skin abrasions, or arthropod vectors (e.g., the poultry red mite Dermanyssus gallinae, described in Ectoparasites of Poultry).

A retrospective summary of avian erysipelas cases in California from 2000 to 2019 documented that turkeys accounted for the majority of submissions, with fewer cases in layers, broilers, and waterfowl [5]. Seasonal peaks in late winter and spring have been observed, possibly linked to climatic conditions that favor bacterial survival. Recent studies from Poland have similarly shown that domestic geese are affected, with molecular typing revealing genetic diversity among isolates [3].

Genetic resistance to erysipelas has been investigated in turkeys. Saif et al. reported that lines selected for increased body weight showed higher mortality after challenge, whereas a line selected for egg production demonstrated greater resistance [6]. This suggests a genetic component in susceptibility that may be exploited in breeding programs.

Clinical Signs and Pathogenesis

The incubation period ranges from one to seven days following natural exposure. In acute erysipelas, turkeys and other poultry present with sudden onset of depression, anorexia, cyanosis of the comb and wattles, and diarrhea. Mortality can reach 50% or higher in untreated flocks. In peracute cases, birds may be found dead without premonitory signs [7, 8]. A chronic form, known as diamond skin disease, is characterized by cutaneous hemorrhages and urticarial plaques on the skin, especially of the breast and legs, and was first described in turkeys by Peterson and Hymas [9]. This form may also lead to vegetative endocarditis, arthritis, and valvular lesions.

Experimental infection studies have elucidated the pathogenesis. Following intravenous inoculation, bacteria rapidly colonize the spleen, liver, and kidneys. Electron microscopic examination of renal tissue reveals bacterial emboli in glomerular capillaries, tubular necrosis, and interstitial inflammation [10]. Bickford et al. described the sequential pathology: within 24 hours, widespread capillary thrombosis and necrosis of lymphoid tissue occur, followed by fibrinoid necrosis of small arteries [8].

Pathology and Histopathology

On necropsy, acute erysipelas in turkeys produces characteristic lesions: petechiae and ecchymoses on the epicardium, serosal membranes, and thigh musculature; splenomegaly; hepatomegaly with a mottled appearance; and pulmonary congestion. Chronic cases exhibit fibrinous pericarditis, valvular endocarditis (particularly the mitral valve), and arthritis. Histologically, the spleen shows lymphoid depletion and fibrinoid necrosis of arterioles; the liver has multifocal necrosis and sinusoidal bacterial clumps. Joints in chronic cases contain purulent exudate with mononuclear cell infiltration [8].

The pathognomonic lesion of "diamond skin" appears as raised, dark red or purple areas in the dermis and subcutis, corresponding to foci of vasculitis and thrombosis [9].

Diagnostic Approaches

Definitive diagnosis of Erysipelothrix rhusiopathiae erysipelas in turkeys and poultry requires isolation of the bacterium from affected tissues. Liver, spleen, bone marrow, or blood from heart or jugular vein are optimal samples. The organism grows on blood agar under microaerophilic conditions at 37 degrees C, forming small, transparent, alpha-hemolytic colonies after 24 to 48 hours. Gram staining showing slender Gram-positive rods with a "tangled thread" morphology is suggestive. Biochemical characterization includes catalase negative, oxidase negative, hydrogen sulfide production, and acid production from glucose and lactose [1, 11].

Serological tests, such as agglutination and ELISA, are available but primarily used for seroepidemiology or vaccination monitoring. Because antibodies persist after natural infection, acute and convalescent sera are needed for active disease diagnosis. Molecular diagnostics using polymerase chain reaction (PCR) targeting the 16S rRNA gene or the surface protein gene spaA provide rapid, sensitive identification from clinical specimens. Random amplified polymorphic DNA (RAPD)-PCR and pulsed-field gel electrophoresis (PFGE) have been used for strain typing, revealing genetic heterogeneity among avian isolates [3].

The diagnostic workflow for suspect erysipelas is summarized below.

flowchart TD
    A[Dead or moribund bird with signs of septicemia], > B[Necropsy and gross lesion evaluation]
    B, > C[Petechiae, splenomegaly, cyanosis?]
    C, >|Yes| D[Collect liver, spleen, bone marrow]
    D, > E[Gram stain: Gram-positive slender rods]
    E, > F[Culture on blood agar: alpha-hemolysis, H2S production]
    F, > G[Biochemical confirmation: catalase -, oxidase -]
    G, > H{PCR targeting 16S rRNA or spaA}
    H, >|Positive| I[Confirmed Erysipelothrix rhusiopathiae]
    H, >|Negative| J[Consider other septicemic diseases:\nfowl cholera, avian influenza, Salmonella]
    J, > K[Perform differential diagnostics:\nPasteurella multocida culture, AI RT-PCR, Salmonella isolation]

Differential diagnoses include Fowl Cholera in Poultry caused by Pasteurella multocida, Highly Pathogenic Avian Influenza (H5N1), Infectious Coryza in Poultry and Ducks, and septicemic colibacillosis. Accurate differentiation relies on culture and molecular methods.

Treatment and Antimicrobial Therapy

Early intervention with antimicrobials reduces mortality in affected flocks. E. rhusiopathiae is susceptible to penicillins, ceftiofur, erythromycin, tylosin, and tetracyclines. Penicillin G (10,000 to 20,000 IU/kg intramuscularly for three to five days) is the drug of choice. In laying hens and turkeys, water-soluble formulations of amoxicillin or tetracycline can be administered via drinking water for flock treatment (withdrawal periods must be observed). Resistance to gentamicin and sulfonamides has been reported and susceptibility testing is recommended, especially for recurrent outbreaks [4, 1].

Supportive care includes reducing stress, improving ventilation, and ensuring access to clean water. Culling or isolation of chronically infected birds (e.g., those with arthritis or endocarditis) is advised because these individuals may serve as persistent shedders.

Vaccination and Control Strategies

Vaccination is a cornerstone of control, particularly in turkey breeder flocks and layer replacements. Bacterins (killed whole-cell vaccines) are commercially available and have been used successfully for decades. However, a landmark study by Bricker and Saif demonstrated that a live attenuated oral vaccine could be administered to turkeys via drinking water, conferring significant protection against challenge [12]. The live vaccine provides both humoral and cell-mediated immunity, but it retains some virulence and is not recommended for use in very young poults or in flocks already infected.

A standard vaccination protocol for turkeys involves subcutaneous or intramuscular administration of a bacterin at 8 to 10 weeks of age, with a booster at 14 to 16 weeks. For layer pullets, two doses before the onset of egg production are typical. Revaccination every 6 months may be necessary in high-risk environments.

Biosecurity measures include strict rodent and wild bird control, proper disposal of dead birds, and cleaning and disinfection of houses between flocks. Because D. gallinae can transmit the bacterium, an integrated mite control program is essential.

Public Health and Comparative Aspects

Although this article focuses strictly on veterinary and avian medicine, it is important to note that E. rhusiopathiae is a zoonotic pathogen (erysipeloid in humans). Personnel handling infected birds or carcasses should wear protective gloves. However, detailed discussion of human disease is beyond the scope of this article.

Comparative serotyping studies have shown that serovars 1a, 1b, and 2 are predominant in poultry isolates, with serovar 2 also commonly recovered from pigs and sheep [2]. Australian isolates from turkeys have similar serovar distributions, reinforcing the role of E. rhusiopathiae as a multi-host pathogen.

Conclusion

Erysipelothrix rhusiopathiae erysipelas in turkeys and poultry remains a significant cause of acute mortality and chronic production loss. Recognition of its characteristic clinical and pathological manifestations, along with rapid laboratory confirmation via culture and molecular methods, is essential for effective outbreak management. Vaccination, antimicrobial therapy, and strict biosecurity, including control of ectoparasites such as D. gallinae, constitute the core control measures. Ongoing surveillance and genotyping of circulating strains will inform vaccine composition and antimicrobial stewardship.

References

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[2] Cross GM, Claxton PD. Serological classification of Australian strains of Erysipelothrix rhusiopathiae isolated from pigs, sheep, turkeys and man. Aust Vet J. 1979. URL: https://pubmed.ncbi.nlm.nih.gov/444165/

[3] Bobrek K, Gaweł A. Phenotypic Characterization and Pulsed-Field Gel Electrophoresis and Random Amplified Polymorphic DNA-PCR Profiling of Erysipelothrix rhusiopathiae Isolated from Erysipelas in Domestic Geese in Poland (2008-2018). Vet Sci. 2025. URL: https://pubmed.ncbi.nlm.nih.gov/41472181/

[4] Eriksson H, Wattrang E, Söderlund R, et al. Erysipelas-A Review of an Emerging Disease in Layers. Avian Dis. 2025. URL: https://pubmed.ncbi.nlm.nih.gov/40249592/

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[6] Saif YM, Nestor KE, Dearth RN, et al. Possible genetic variation in resistance of turkeys to erysipelas and fowl cholera. Avian Dis. 1984. URL: https://pubmed.ncbi.nlm.nih.gov/6487197/

[7] Hollifield JL, Cooper GL, Charlton BR. An outbreak of erysipelas in 2-day-old poults. Avian Dis. 2000. URL: https://pubmed.ncbi.nlm.nih.gov/11007027/

[8] Bickford AA, Corstvet RE, Rosenwald AS. Pathology of experimental erysipelas in turkeys. Avian Dis. 1978. URL: https://pubmed.ncbi.nlm.nih.gov/697661/

[9] Peterson EH, Hymas TA. Diamond skin disease (chronic erysipelas) in a turkey. J Am Vet Med Assoc. 1950. URL: https://pubmed.ncbi.nlm.nih.gov/14794545/

[10] Tsangaris T, Iliadis N, Kaldrymidou E, et al. [Experimental erysipelas in turkeys following intravenous infection with Erysipelothrix insidiosa. I. Electron microscopic findings in the kidneys]. Zentralbl Veterinarmed B. 1980. URL: https://pubmed.ncbi.nlm.nih.gov/7223179/

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[12] Bricker JM, Saif YM. Use of a live oral vaccine to immunize turkeys against erysipelas. Avian Dis. 1988. URL: https://pubmed.ncbi.nlm.nih.gov/3202763/