Salmonella Dublin Infection in Cattle

Salmonella Dublin infection in cattle occurs worldwide; however, the proportion of affected herds varies greatly by country. In Europe, some countries have established S Dublin infection control and eradication programs. Generally, the prevalence is lower in countries with control programs.

Salmonella Dublin infection in cattle can cause respiratory disease and septicemia. The disease is transmitted by two major routes: oral and vertical (see transmission routes figure). In the oral route, susceptible cattle ingest the bacteria through contact with materials contaminated by feces or other bodily fluids (eg, milk, saliva, nasal secretions) from infected animals. In the vertical route, infected pregnant cows transmit the disease to their offspring in utero. This can result in abortion in the last trimester of gestation or the birth of congenitally infected calves. Aerosolized transmission is also possible, especially among calves housed in tight, confined spaces. 

Transmission routes for Salmonella Dublin infection in cattl...

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Created with BioRender.com.

Once an animal is infected, S Dublin colonizes the digestive tract and then moves to the mesenteric lymph nodes. From there, it can disseminate and cause systemic disease. Adaptation of S Dublin to cattle is attributed to the selective survival of strains capable of evading the host’s immune response. In these instances, the inflammatory response to infection in the intestine is ineffective in preventing systemic dissemination of infection. Because of the more invasive capacity of S Dublin, clinical signs of infection with this serotype are more severe than they are with salmonellosis from other, less pathogenic, bovine-adapted Salmonella serotypes, such as S Cerro.

The clinical signs of S Dublin infection depend on the affected patient's age and the pathogen's endemicity in the herd. Although S Dublin infection can affect cattle of all ages, it is most common in calves aged 2−12 weeks. In naive herds, the pathogen is rapidly transmitted, and an outbreak ensues. Although most Salmonella infections present as GI disease, S Dublin infection most often presents as a respiratory illness. Typical clinical signs of S Dublin infection in calves include the following:

• hyperthermia (fever)

• obtundation (listlessness)

• anorexia

• pneumonia

• respiratory distress (eg, elevated respiratory rate, coughing)

• dehydration

• septicemia

Arthritis (swollen joints) and meningoencephalitis can also occur in calves after bloodborne transmission of the bacteria. Bloody diarrhea is also possible but not very common. A peracute presentation may occur in calves, and sudden death in 1–2 days may result from endotoxic shock. Calves 6–8 weeks old that survive acute infection can develop chronic infection characterized by poor growth rate, ill thrift, lameness due to arthritis, and loose stool. Morbidity, mortality, and case fatality rates for S Dublin infection outbreaks in dairy calves are 10.5–34.8%, 2.3–18.2%, and 26.4%, respectively.

In adult cattle, typical clinical signs of S Dublin infection include the following:

• slight fever

• mild diarrhea

• sudden decrease in milk production

Less typically, S Dublin infection in adults can cause bloody diarrhea and, in rare instances, death. Pregnant cattle may abort as a result of bacteremia. S Dublin infection in adult cattle can generate persistent infections without clinical signs. These latent carriers can periodically shed the pathogen in feces or fluids during times of stress or when immunocompromised, contributing to disease transmission in affected herds.

• Culture

• Necropsy

• ELISA

Confirmation of the diagnosis of S Dublin infection is based primarily on isolating the bacteria in samples from affected cattle. Although feces are the most frequently submitted sample for isolation of S Dublin, fecal culture has a relatively low sensitivity. Thus, other samples—ideally postmortem specimens from mesenteric lymph nodes, lungs, liver, kidney, and spleen—are recommended for confirmation. Blood can also be submitted for culture in cases of suspected bacteremia in live patients; however, aseptic collection techniques must be used, which can be difficult under farm conditions.

Although there are no pathognomonic lesions for infections with S Dublin, postmortem examination of affected calves (see necropsy image) usually reveals lesions compatible with septicemia. These include pulmonary congestion, suppurative pneumonia, and chronic bronchopneumonia; diffuse catarrhal hemorrhagic enteritis, ileitis, and mesenteric lymphadenitis; and hepatomegaly, splenomegaly, and gelatinous edema of the gallbladder. Jaundice and suppurative arthritis in several joints are also common findings.

Salmonella Dublin infection, necropsy, heifer

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Courtesy of Faith Cullens-Nobis (Michigan State University).

ELISA can detect antibodies against S Dublin in serum or milk and can be used for herd monitoring, identification of latent carriers, and control and eradication programs. However, the assay's sensitivity is relatively low: antibodies in the assay can cross-react with other Salmonella serotypes. Thus, results must be interpreted carefully. Sequential samples should be obtained from individual patients, using milk or serum samples to differentiate acutely infected patients from latent carriers, who have elevated antibody concentrations for several months. The monitoring of bulk-milk antibody concentrations is used in S Dublin eradication schemes in some Scandinavian countries, although this approach has low sensitivity unless repeated sampling is done.

• Fluid and electrolyte replacement

• Anti-inflammatory administration

• Antimicrobial use: controversial

There is no targeted treatment for S Dublin infection beyond the general recommendations for any S enterica infection, which are to correct dehydration and electrolyte imbalances and to decrease inflammation. Calves with systemic infection should be administered NSAIDs (eg, flunixin meglumine, 2.2 mg/kg, IV, every 24 hours; or meloxicam [extralabel use], 0.5 mg/kg, IV or SC, every 24 hours for up to 5 days) to manage inflammation.

The administration of antimicrobials for treatment of S Dublin infection is controversial for several reasons. First, appropriate antimicrobial selection is challenging, because most S Dublin strains are multidrug-resistant. US strains are frequently not susceptible to antimicrobials labeled for use in calves with septicemia. Thus, in most cases, treatment with antimicrobials would require extralabel administration of these drugs, as well as determination of withholding periods for meat, under the direction of a licensed veterinarian.

Second, the use of an antimicrobial deemed potentially effective, based on the susceptibility of S Dublin to the drug, is usually not permitted for the treatment of S Dublin infection. For example, US isolates of S Dublin are usually susceptible to enrofloxacin; however, use of enrofloxacin to treat S Dublin infection is extralabel, which is prohibited for fluoroquinolones in food-producing animals in the US.

Finally, there is a risk of enhancing pathogen resistance to antimicrobials with continuous administration, and cattle treated with antimicrobials are more likely to become latent carriers of S Dublin that contribute to further transmission of infection.

Prevention and control goals for S Dublin infection in cattle are to 1) minimize pathogen exposure and 2) maximize pathogen resistance. Sanitation and biosecurity are critically important for achieving these goals.

• Velasquez-Munoz A, Castro-Vargas R, Cullens-Nobis FM, Mani R, Abuelo A. Review: Salmonella Dublin in dairy cattle. Front Vet Sci. 2024;10:1331767.