SIGNIFICANCE AND IMPLICATIONS FOR ANIMAL HEALTH
It is generally considered that B. burgdorferi establishes persistent infections with minimal harm to its natural hosts. However, aberrant hosts, such as humans and domestic animals, may develop clinical disease as a deviation from the norm.
However, very little research on potential effects of bor- relial infection in wild animals has been performed. It is improbable that infection with B. burgdorferi is a common cause of acute mortality in wild species, but it is possible that natural hosts develop non- fatal disease that escapes detection. Very few natural host species have so far been analysed for pathogenesis in experimental studies, and in the field it is even more difficult to detect disease caused by B. burgdorferi.
The possibility should not therefore be dismissed that borrelial infection may affect the life history traits of wild animals. Subclinical infections could plausibly result in loss of vigour with subsequent decrease in survival and reproduction. In particular, neonatal animals, having immature innate and acquired immune responses that favour development of disease, and animals that suffer from other disorders affecting the immune responses (i.e. anaplasmosis), may be at risk.
Genotypes of B. burgdorferi sl other than the four most important pathogens for humans probably have reservoir host-vector cycles that rarely if ever involve human infections and may, for this reason, have escaped attention. Much work remains to elucidate all possible aspects of borrelial infection in wild birds, mammals and reptiles.