Iveson et ah Salmonella in an island marsupial 
Table 2 
Salmonella isolations by serovars from tagged quokkas {Setonix brachyurus) in close associations with humans on Rottnest Island over 
a 12-month period from 1984-1985. 
Salmonella 
Settlements 
Camping 
Kingston 
Lighthouse 
Mobiles 
Totals 
serotypes 
Area 
Barracks 
Swamp 
adelaide 
10 
3 
5 
23 
3 
44 
It alsterdorf 
1 
1 
aiibtum 
3 
1 
2 
6 
birkcnhead 
2 
2 
4 
booth 
4 
4 
bovismorbificans 
2 
2 
Chester 
1 
1 
16 
18 
decatiir 
3 
1 
1 
2 
1 
8 
infantis 
1 
1 
2 
javiana 
8 
4 
8 
1 
2 
23 
muenchen 
12 
5 
5 
13 
3 
38 
newington 
2 
6 
8 
oranienburg 
8 
8 
orientalis 
4 
3 
14 
1 
22 
orion 
3 
1 
4 
polsdam 
2 
2 
rottnest 
1 
1 
7 
9 
typhimurium 
11 
10 
10 
4 
35 
It wandsbek 
9 
2 
8 
36 
55 
IV waycross 
2 
4 
6 
53:d:z^^ 
1 
1 
2 
Illb 25:1 v:z^ 
3 
1 
1 
Illb 50:K:z^ 
1 
1 
Illb 61 1 
3 
3 
Illb 
2 
3 
5 
Total Isolations 
81 
27 
54 
133 
14 
309 
Total Serotypes 
20 
8 
15 
14 
6 
(25) 
Quokkas tagged 
344 
91 
86 
100 
49 
670 
javiana was isolated once but S. typhimmium remained 
undetected. A summary of the serotypes isolated at all 
sites in contact with the public, including isolations from 
mobile quokkas, is given in Table 2. 
Differences in infection rates between areas 
Examination of all field data reveals three major 
groupings based on the infection rates in the 670 quokkas 
examined. These are Kingston Barracks, Lighthouse 
Swamp and the settlement areas and variation over time 
in infection rates at these sites is graphed in Figure 2. A 
marked seasonal pattern is evidept in all 3 sites, with 
infection rates falling to between 0 and 20% in winter 
and reaching a peak in late summer/autumn. A one-way 
ANOVA shows significant variation between the 
infection rates in the 3 sites with F^,^ = 4.813 and P 
= 0.0163. Bonferoni's posteriori Multiple Comparison 
Test shows that infection rates in the Settlement areas are 
significantly lower than both Kingston Barracks and 
Lighthouse Swamp with P < 0.05. 
Differences in infection rates based on age and sex 
The number of juveniles sampled was generally too 
small for statistical analysis except in the case of the 
settlement areas where the infection rate in juveniles was 
significantly higher than in adults (X- = 5.06, P = 0.02, see 
Table 3). A sex difference was only found in adults from 
the Lighthouse Swamp sample where a higher infection 
rate was seen in females (X= = 4.349 P = 0.037) as shown 
in Table 4. This difference was not due to a seasonal bias 
in sampling of the two sexes as a total of 67 quokkas was 
positive at least once of which 30 were males and 37 
females. 
Changes in infection rates in individual quokkas 
Only at Lighthouse Swamp were individuals 
recaptured frequently and thus was it possible to observe 
changes in infection status in a single animal over both 
the short and long term. Data from 19 quokkas that were 
Table 3 
Comparison of Salmonella infection rates in adult and juvenile 
quokkas, Setonix brachyunis, from settlement areas on Rottnest 
Island, with percentages in parentheses 
Quokkas 
Positive (%) 
Negative (%) 
Totals 
Adults 
101 (15.4) 
555 (84.6) 
656 
Juveniles 
15 (28.3) 
38 (71.7) 
53 
Totals 
115 (16.2) 
594 (83.8) 
709 
Table 4 
Comparison of Salmonella infection rates in male and female 
adult quokkas, Setonix brachyunis, from Lighthouse Swamp on 
Rottnest Island, with percentages in parentheses 
Quokkas 
Positive (%) 
Negative (%) 
Totals 
Males 
36 (27.5) 
95 (72.5) 
131 
Females 
63 (39.9) 
95 (60.1) 
158 
Totals 
99 (34.3) 
190 (65.7) 
289 
131 
