Salmonella enterica subsp. Enterica in Cattle Egret (Bubulcus ibis) chicks from central Texas: prevalence, serotypes, pathogenicity, and epizootic potential.

The research article focuses on the prevalence, serotypes, pathogenicity, and possible transmission of Salmonella enterica subsp. Enterica in Cattle Egret chicks found in central Texas. While 17 diverse serotypes were discovered, the 4,5,12:i-monophasic serotype was most common, and highly pathogenic. However, no concrete evidence of transmission between Cattle Egrets and horses or cattle was found.

Introduction and Objectives

• The researchers aim to understand the occurrence and spread of a bacterial species, Salmonella enterica subsp. enterica, in Cattle Egret chicks over a period of three years in Central Texas. The purpose of the study is to identify the prevalence, specific variants (serotypes), the degree of destructiveness (pathogenicity), and the potential for wide-scale spread (epizootic potential) of the bacteria.

Methodology

• Nestlings from five Cattle Egret colonies were studied for bacterial infection. The bacterial cultures were obtained from the digestive tract and pooled spleen and liver of these birds.
• These isolates were further tested for their susceptibility to antibiotics and their ability to cause disease using a day-old chick infection model.
• For comparison purposes, the researchers also studied Salmonella enterica subsp. enterica isolates from horses admitted to the Texas A&M University Veterinary Teaching Hospital.
• Further, isolates from feedlot and dairy cattle from Texas and the surrounding states were also analyzed.

Findings and Conclusions

• Infected nestlings ranged from 29% to 95% amongst all the colonies, indicating a significant presence of Salmonella.
• Among the 17 different serotypes identified in the bird colonies, the 4,5,12:i-monophasic serotype was the most common and was observed to be highly invasive.
• Microscopic lesions were found in the livers of Cattle Egrets infected with the 4,5,12:i-monophasic serotype, suggesting that this particular variant could often lead to fatal outcomes.
• While 12 serotypes were common to both Cattle Egrets and horses, there was no evidence of bacterial transmission between these species. Similar results were observed when the Cattle Egret bacterial isolates were compared with those from cattle.
• In light of the high invasiveness of the 4,5,12:i-monophasic serotype and its association with food poisoning in other studies, it appears that colonies of Cattle Egrets could pose a significant health risk to humans living close by, possibly through contamination of food or the environment.