The Centers for Disease Control and Prevention has linked the multistate outbreak of the multidrug resistant Salmonella Heidelberg infections to contact with infected dairy bull calves that were bought from livestock markets in Wisconsin.
Twenty-One Cases In Eight States
In an update on the outbreak posted on Nov. 28, the CDC said that 21 people have been infected in eight states between Jan. 11 and Oct. 24. Of these, eight were hospitalized albeit no death was reported. The CDC attributed the outbreak to Wisconsin calves based on epidemiologic, traceback and laboratory results.
Those who got sick were between 1 and 72 years old. Wisconsin had the most number of cases with 12 individuals in eight counties infected. South Dakota and Minnesota each had two cases while Iowa, Idaho, California, Oklahoma and Missouri each had one case.
Some Calves Bought For 4H Projects
Dairy bull calves are young male cattle that were not castrated. They may be raised for their meat. Some of the calves linked to the outbreak were bought for use with 4H projects.
In interviews, 15 of the 19 interviewed patients reported contact with the calves or other cattle. Some also reported that they got sick after their dairy bull calves became sick or died.
Human Infections Linked To Sick Calves
Tests using whole genome sequencing revealed that isolates from those who were sickened are genetically closely related to isolates from the calves, which means human infections in this outbreak were likely linked to ill calves.
The isolates were likewise found to be resistant to antibiotics. The Wisconsin State Laboratory of Hygiene, which conducted antibiotic resistance testing on clinical isolates from infected individuals, identified multiple antimicrobial resistance genes in isolates taken from 15 patients and eight cattle.
All of the isolates were found to be multidrug resistant, which is linked to increased chances for hospitalization, development of infection in the bloodstream or treatment failure in infected individuals.
Symptoms of Salmonella infection include abdominal pain, nausea, vomiting, diarrhea, chills, fever, headaches and muscle pain. The symptoms often start six to 72 hours after exposure to bacteria. Most people recover in a matter of one week but some become so sick they need to be hospitalized.
Hospitalization rate is usually about 20 percent but the hospitalization rate in this particular outbreak is nearly twice the rate at 38 percent. The high rate may be attributed to the fact that the bacteria are resistant to antibiotics and some of the infected individuals are very young.