Continued analyses of sample material and epidemiological data in recent weeks has not provided significant new information, but has confirmed and strengthened results and assessments from earlier in the outbreak. 

"The results of the survey of sample material from the sick dogs has reinforced the suspicion that Providencia alcalifaciens has contributed to the disease in sick dogs, and genetic analyses of bacterial isolates from sick dogs indicate that they may stem from a common source. However, we do not know what a possible source of infection is", says veterinarian Hannah Joan Jørgensen at the Veterinary Institute.

Diarrhea, also bloody diarrhea, is relatively common in dogs and is a possible symptom of many different infectious and non-infectious diseases. It is, therefore, a non-specific symptom that is not unexpected in dogs occasionally. However, in this outbreak, many dogs became severely ill within a short period of time, and this is unusual. 

Not previously known to cause such large outbreaks

The discovery of the bacteria P. alcalifaciens in so many sick dogs is striking, but some work remains to document whether this bacteria itself caused the disease. 

"This bacterium is not previously known to cause such large outbreaks with severe symptoms in dogs. Nor have we been able to demonstrate any commonalities in the sick dogs regarding, e.g. form of activities, walking areas or feeding to explain a common source of infection. Therefore, it is still uncertain whether a point introduction of this bacterium is the origin of the outbreak. We are prepared that it may never be possible to confirm this. It will take time to determine whether Providencia alcalifaciens alone can cause such severe bowel disease in dogs, but this will remain a priority research task for us and our research partners in the months to come", says Jorun Jarp, Chief Security Officer at the Norwegian Veterinary Institute.

The source of infection remains unknown

"Genetic analyses of the Providencia bacterium from several of the sick dogs show that these are so genetically similar that there is reason to suspect that the bacteria came from the same source of infection. However, results from epidemiological studies, in the form of surveys and interviews, do not point to a common source of infection. If it is one common source, it is unlikely that we will be able to identify it now that the outbreak is over", says Jørgensen.

Full genome sequencing of the Providencia bacteria from 22 dogs has shown that for 14 of these, the bacteria are so closely related genetically, that one may suspect a common source of infection. These findings must nonetheless be interpreted in relation to other factors, such as for example, epidemiological findings. The Norwegian Veterinary Institute is working on expanding genetic analyses of bacteria as well as pathological investigations of intestinal tissues collected from the necropsied dogs. Together with research on the potential of Providencia alcalifaciens to cause cell and tissue damage, we hope to eventually conclude whether the outbreak seen during the autumn of 2019 was caused by P. alcalifaciens or not.