3.3. Occurrence of C. parvum in Neonatal (1-4-Week-Old)
Calves
During the outbreak, 27 of 40 (67.5%) fecal specimens collected from
neonatal calves were positive for Cryptosporidium spp. by PCR,
including C. parvum (n = 24) and C. bovis (n = 3). After
the outbreak, 35 of 56 (62.5%) fecal specimens collected from neonatal
calves were positive for Cryptosporidium spp., including C.
parvum (n = 17), C. bovis (n = 17) and C. ryanae (n = 1)
(Fig. 2). The infection rate of C. parvum during the outbreak
(60.0%, 24/40) was significantly higher
(χ2 =
8.38, df = 1, P = 0.004) than after the outbreak (30.4%,
17/56) (Fig. 2). Animals older than 4 weeks had no C. parvuminfection during and after the outbreak. Instead, they were mostly
infected with C. bovis (n = 56) and C. ryanae (n = 39),
together with some occurrence of C. occultus (n = 6) and C.
andersoni (n = 5) (Table 3). Therefore, during the outbreak, C.
parvum was the dominant species in neonatal calves, while after the
outbreak, C. bovis and C. parvum occurred at the same
frequency (Table 3).
Altogether, 39/41 specimens positive for C. parvum were
successfully subtyped at the gp60 locus. The sequences obtained
were all identical to the reference sequence KU248815 of the IIdA20G1
subtype from GenBank.
3.4. Correlation between Cryptosporidium Spp. and
Diarrhea Occurrence as Indicated byχ2Analysis
In neonatal (1-4-week-old) calves, Cryptosporidium infection
rates were 66.7% (26/39), 69.2% (9/13) and 61.4% (27/44) in animals
with watery diarrhea, moderate diarrhea and no diarrhea, respectively.
The differences among groups were not significant in
χ2 analysis
(χ2 =
0.40, df = 2, P = 0.820) (Tables 4). ByCryptosporidium species, C. parvum infection rates were
61.5% (24/39), 38.5% (5/13), and 27.3% (12/44) in animals with watery
diarrhea, moderate diarrhea and no diarrhea, respectively. The
difference in C. parvum infection rates between animals with
watery diarrhea and those with no diarrhea was significant
(χ2 = 9.88, df = 1, P = 0.002)
(Tables 4). In contrast, the infection rate of C. bovis in
animals with no diarrhea (31.8%, 14/44) was significantly higher than
those with watery diarrhea (5.1%, 2/39) (χ2 =
9.46, df = 1, P = 0.002). Infection rates of C.
ryanae were similar among the three groups (χ2= 1.19, df = 2, P = 0.550) (Tables 4).
No C. parvum infection nor watery diarrhea was observed in calves
older than 4 weeks. In this age group, the infection rates ofCryptosporidium spp. were 58.8% (30/51) and 60.6% (40/66) in
animals with moderate diarrhea and those without diarrhea, respectively
(χ2 = 0.04, df = 1, P = 0.845)
(Tables 4). By Cryptosporidium species, the infection rates ofC. bovis (χ2 = 0.078, df = 1,P = 0.780) or C. ryanae (χ2 =
0.005, df = 1, P = 0.941) were not significantly different
between the two groups (Tables 4).