An evidence gap map (EGM) is an innovative, visual and interactive tool used to systematically present a range of research activity on a topic. EGMs highlight any gaps in the current published literature and emphasize the abundance of available research on a topic. We used EGMs to convey the range of literature examining Salmonella found in feed intended for consumption by livestock and poultry.
Evidence gap maps can be used to inform decisions about areas for future research. For instance, an EGM can identify a potential area for a systematic review based on the available published literature. In contrast, EGMs can also indicate where research is lacking and where future primary research could be directed.
In these evidence gap maps, the columns display the region or animal species for which the feed is intended and the rows display the animal species, the sector the feed-related Salmonella came from, or the serovars that were investigated. The bubbles within each cell display the number of studies that examined the specific combination of categories. Depending on the table, the bubbles represent the study design, study outcome, or the serovar reported. The size of the bubble is the proportion of studies that belong to a specific characterization, with the denominator being the total number of studies in that cell (i.e., a cell may have a single large bubble if all studies in that cell belong to one categorization). Multiple studies can report results for more than one region, animal species, sector and serovar. Thus, the total number of studies in the EGMs may exceed the actual number of different studies reported in the scoping review.