Sero-surveillance and risk factors of burkholderia mallei infection in indigenous horses of Bangladesh with a brief review on validation of serodiagnosis

Background: Glanders is a highly contagious and fatal zoonotic reportable antique disease of solipeds caused by the Gram-negative bacterium Burkholderia mallei. This disease has been eradicated from most of the western developed countries in the 20th century and its occurrence was reduced in endemic developing nations but recent reports on the occurrence of clinical cases and outbreaks of this disease in both the eradicated and endemic countries indicates that it has regained the status of a re-emerging disease in the world. However, the information on the occurrence of B. mallei infection is almost lacking in Bangladesh. Objective: This study was conducted on the sero-surveillance and risk factors of B. mallei infection in indigenous working horses in Bangladesh Materials and Methods: A cross-sectional study on the sero-surveillance and risk factors of B. mallei infection was carried out in 125 indigenous horses in the districts of Mymensingh and Tangail during January to August 2019. Individual serum samples were screened using Complement fixation test (CFT) at the OIE and National Reference Laboratory for Glanders, Germany and Enzyme linked immunosorbent assay (ELISA) at the National Research Centre on Equines, Haryana, India. Risk factors were identified using multivariable logistic regression analysis. Results: The overall sero-prevalence of B. mallei infection in indigenous horses was found to be 10.4% (95% CI: 5.9 -17.5). None of the 13 CFT positive sera was positive with ELISA. The odds of B. mallei infection were 6.1 times (95%CI: 1.7-28.9) higher in horses with the history of skin lesion than those without skin lesion. Significantly higher odds of B. mallei infection (odds ratio: 5.8; 95% CI: 1.4-39.7) were observed in horses with the history of parasitic infestation than those without parasitic infestation. Conclusions: The relatively higher prevalence of B. mallei infection observed in this study should be interpreted with caution as all CFT positive samples negative with ELISA indicating some false positive reactions. Further studies are needed to test the accuracy of the serological tests for the detection of B. mallei infection in horses in Bangladesh.