Date Published: June 14, 2006
Publisher: BioMed Central
Author(s): N Kemper, A Aschfalk, C Höller.
The specific aim of this study was to assess the faecal shedding of zoonotic enteropathogens by semi-domesticated reindeer (Rangifer tarandus tarandus) to deduce the potential risk to human health through modern reindeer herding. In total, 2,243 faecal samples of reindeer from northern regions of Finland and Norway were examined for potentially enteropathogenic bacteria (Campylobacter species, Enterococcus species, Escherichia coli, Salmonella species and Yersinia species) and parasites (Cryptosporidium species) in accordance with standard procedures. Escherichia coli were isolated in 94.7%, Enterococcus species in 92.9%, Yersinia species in 4.8% of the samples and Campylobacter species in one sample only (0.04%). Analysis for virulence factors in E. coli and Yersinia species revealed no pathogenic strains. Neither Salmonella species nor Cryptosporidium oocysts were detected. The public health risk due to reindeer husbandry concerning zoonotic diseases included in this study has to be considered as very low at present but a putative epidemiological threat may arise when herding conditions are changed with respect to intensification and crowding.
Zoonotic organisms such as viruses, bacteria or parasites can possess the potential to cause severe diseases both in humans and animals. Free-ranging animals with sporadic or indirect contact to domestic livestock and humans may serve as reservoirs or sentinels for diseases. Transmission of these pathogens can occur directly from a reservoir to the susceptible animal or human being, for example through direct contact with free-ranging animals including cervids . Indirect transmission occurs via vectors, i.e. mosquitos, by contamination of the environment through faecal shedding  or by consumption of venison . The epidemiological situation in free-ranging, semi-domesticated animals like reindeer (Rangifer tarandus tarandus), however, is difficult to assess, in contrast to domestic animals. Conclusions derived from studies which focus on domestic animal species in extensive husbandry systems can only be used with caution. But it can be assumed that pathogens are transmitted easily through close animal contact and lead to high animal losses as it is known from intensive husbandry systems. This is of special importance as the crowding of reindeer for winter feeding is becoming more and more common, particularly in southern parts of Northern Finland.
In 2,224 (99.2%) out of the total number of 2,243 faecal samples, one or more of the examined bacteria species were isolated.
In reindeer, Enterococcus species and E. coli occurred at very high prevalence, showing the affiliation of these two species to the normal intestinal flora of healthy reindeer. With regard to E. coli, there are few reports of diseases caused by shigatoxin-producing bacteria in ruminants [14,15]. However, these bacteria are of extreme importance in causing severe diseases in humans . As the genes encoding stx1, eae and hlyEHEC were detected in very few of the isolated E. coli-strains, the human health risk due to E. coli excreted by reindeer can be considered very low at present. These results comply with two other studies detecting no E. coli O157:H7 in 1,387 faecal and 421 meat samples from reindeer  and no STEC in 50 faecal samples from reindeer . It is known, however, that STEC virulence factors are mobile within bacterial populations . Therefore, an increase in the occurrence of toxin genes in E. coli from reindeer cannot be excluded when influencing parameters such as herding conditions are changed.
With respect to the investigated pathogens, the analysis of faecal samples from Norwegian and Finnish reindeer indicates that the animals do not represent an important source for zoonotic diseases at the moment. Enterococcus species and E. coli belong to the normal intestinal flora of reindeer. Climate conditions in the northern regions are a limiting factor to the survival of enteropathogens in the environment and might be a reason for the low prevalences of the other pathogens examined.
Campylobacter spp., Enterococcus spp., Escherichia coli, Salmonella spp., Yersinia spp., og Cryptosporidium oocyster hos semi-domesticerade renar (Rangifer tarandus tarandus) i Finlands och Norges nordliga trakter