Download Presence of Mycobacterium Avium Subspecies

Presence of Mycobacterium Avium Subspecies Paratuberculosis in Freeranging Caribou
Orsel K. (1), Kutz S. (2), De Buck J. (1), Branigan M. (3), Croft B. (3), Cuyler C. (4), Davison T. (3), Veitch A. (3),
Rivard S. (5), Brodeur V. (5), Taillon J. (6), Elkin B. (3), Barkema H.W. (1)
(1) Dept. of Production Animal Health, Univ. of Calgary. Calgary, AB, T2N 4N1, Canada, [email protected]
(2) Dept. of Ecosystem and Public Health, Univ. of Calgary. Calgary, AB, T2N 4N1, Canada
(3) Environment and Natural Resources, Government of the NWT, NT, Canada
(4) Greenland Institute of Natural Resources, DK-3900 Nuuk, Greenland
(5) Ministère des Ressources naturelles et de la Faune, Québec, Canada
(6) Université Laval, Québec, Canada
ABSTRACT
Fecal samples were collected from hunted caribou in northern Canada and Greenland under the CircumArctic
Rangifer Monitoring and Assessment network (CARMA) research program to determine the prevalence of
shedding of Mycobacterium avium subspecies paratuberculosis (MAP). One-time sampling results are currently
available of 121 caribou in 6 herds. The average prevalence of fecal shedding with MAP was 14%. Greenland,
with a prevalence of 32%, was the region with the highest prevalence. IS1311 PCR-REA subtyping was done on
one isolate from the Greenland herd and was found to be of the bovine subtype. At this point in time the
significance of these findings is not fully understood. Further investigations on the implications are needed.
KEYWORDS
Johne’s disease, Mycobacterium avium subsp. paratuberculosis, caribou, prevalence, arctic, wildlife
INTRODUCTION
Johne’s disease is a debilitating chronic enteritis in ruminants caused by Mycobacterium avium subspecies
paratuberculosis (MAP). The presence of MAP in both wild cervids and bovids, including semi-domesticated
reindeer (Tryland et al., 2004), is increasingly being reported, although the epidemiology and impact in wild
species is not understood. Transmission of the pathogen between wildlife and livestock has never been
reported.
Johne’s disease is a concern for human health too, due to its zoonotic potential. Recent meta-analyses
demonstrate that the association of MAP with Crohn’s disease in humans is specific and cannot be denied,
although a causal role has not yet been demonstrated (Abubakar et al., 2008; Feller et al., 2007). Intestines may
contain a high MAP load and thus a special concern for indigenous people who depend on wild caribou for
sustenance may be the consumption of uncooked intestines or contamination of the meat by intestinal contents.
Within the CircumArctic Rangifer Monitoring and Assessment network (CARMA) fecal samples were collected
from hunted caribou in northern Canada and Greenland (Figure 1). The goal of the CARMA project is to improve
understanding of the relative resilience and vulnerability of regional Human-Rangifer systems to climate change
on circumpolar scale. Through coordinated knowledge collection and sharing and using a multidisciplinary
exchange, we try to develop and promote adaptive strategies and policies that will ensure a sustainable humanRangifer future. Sampled caribou populations are distributed across the Canadian North and Greenland. The
samples are field collections of hunter-killed animals to assess body condition and health. If possible, information
was collected on gender, female with or without calf, estimated age and GPS latitude of capture location. Fecal
samples were submitted to the laboratory at University of Calgary, Faculty of Veterinary Medicine. All fecal
samples were decontaminated to eliminate fungi, spores and non-Mycobacterium spp. Presence of MAP was
determined after 56-day of culture in a TREK ESP Culture System II using a liquid 7H9 supplemented medium
and by using a nested MAP-specific IS900 PCR (Bull et al., 2003).
The prevalence of MAP PCR-positive fecal samples was 14% (95% CI: 8 to 20%) (Table 1). However, the
prevalence was not equally distributed over the 6 regions in which caribou were sampled (P<0.05). Greenland
was with a prevalence of 32% the region with the highest prevalence of shedding MAP, while the prevalence
was low in the other regions. IS1311 PCR-REA subtyping was done on one of the Greenland isolates according
to the method previously described by Motiwala et al. (2003). This isolate was found to be of the bovine subtype.
Figure 1. Geographic location of the sampled caribou herds (1=George river; 2=Leaf river; 3=Bathurst;
4=Bluenose west; 5=Boreal woodland caribou; 6=Tuktoyaktuk Peninsula; 7=Greenland).
Table 1. Culture results of 121 caribou in 6 regions of the CircumArctic (culture results of George river
and Leaf river herds not available yet).
# samples
total
MAP-pos
Bathurst
37
1 ( 3%)
Cape Bathurst
13
0 ( 0%)
Bluenose West
8
1 (13%)
Boreal W Caribou
10
0 ( 0%)
Tukt. Peninsula
6
0 ( 0%)
Greenland
47
15 (32%)
DISCUSSION
Although the epidemiology and significance of MAP in wild species is not fully understood, it is clear that caribou
do harbor the bacterium. It is probable that all species of ruminants are susceptible to infection with MAP
(Mannings and Collins, 2001). MAP has also been isolated from non-ruminant wildlife such as lagomorph, canid,
mustelid, corvid and murid species (e.g. Daniels et al., 2003). The role of wildlife as reservoirs of this infectious
disease for cattle has been discussed in literature (e.g. Daniels et al., 2003). Increasing the knowledge on this is
of importance as northern expansion of domestic, or semi-domestic (reindeer), livestock farming might lead to
increased opportunities for contact with wild caribou. Additionally, the finding of MAP in caribou raises concerns
about possible translocation and re-introduction activities. In particular, consideration needs to be given as to
whether test positive animals pose a risk for MAP translocation and introduction into new habitats and whether
such introduction may pose a risk for conservation of other wildlife species.
In caribou no clinical case of Johne’s disease has been reported. However, if MAP infection caused clinical
disease in caribou it is probable that these animals would be detected by predators in the ‘pre-clinical’ or very
early in the clinical stage and thus would be removed from the population (and thus unlikely to be selected by
hunters). It is possible, however, that MAP-infection does not affect caribou at all.
We are currently investigating the contact structure between caribou herds and contact structure of caribou with
other ruminants. Ideally, we would like to investigate if MAP is present in other sympatric, or nearby, species.
We will explore existing and develop new typing techniques with a greater discriminatory power to investigae
whether the same MAP strains can be found in other wildlife species and domestic ruminants. The genetic
material of MAP from Caribou will be compared to that of previously MAP DNA in wood bison (Sibley et al.,
2007).
Culture of fecal samples is in cattle less sensitive than culture of tissue samples such as mesenteric lymph
nodes and ileum (e.g. McKenna et al., 2004). If this is also true in caribou, the prevalence based on culture of
fecal samples will underestimate the true prevalence of MAP-infection in caribou. For this purpose, we currently
are collecting tissue samples of caribou in the same herds.
CONCLUSIONS
Mycobacterium avium subspecies paratuberculosis is present in free-ranging caribou. Currently, the significance
of these findings is not fully understood. Focus of future investigations should be on understanding transmission
of disease within and between herds, contact structure analysis of the herd under investigation and culture of the
MAP bacterium for strain typing.
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