TABLE 2.
Neonatal-mouse infectivity of intact Cryptosporidium parvum oocysts (bovine genotype A) isolated by one of three in vitro excystation protocolsa
| Trialb | Dose | % Infected (no. of infected pups/total no. of pups)
|
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Protocol I
|
Protocol II
|
Protocol III
|
Positive controlc
|
Negative controld
|
|||||||
| Homogenate | Histology | Homogenate | Histology | Homogenate | Histology | Homogenate | Histology | Homogenate | Histology | ||
| A | 50 | 60 (6/10) | 90 (9/10) | 70 (7/10) | 60 (6/10) | 40 (4/10) | 36.4 (4/11) | 76.9 (10/13) | 76.9 (10/13) | ||
| A | 500 | 100 (11/11) | 100 (11/11) | 100 (11/11) | 100 (11/11) | 83.3 (10/12) | 66.7 (8/12) | 100 (14/14) | 100 (14/14) | ||
| A | 5000 | 100 (10/10) | 100 (10/10) | 100 (10/10) | 100 (10/10) | 100 (12/12) | 100 (12/12) | 100 (12/12) | 100 (12/12) | ||
| A | 0f | 0 (0/11) | 0 (0/11) | ||||||||
| B | 50 | 66.7 (8/12) | 0 (0/12) | NDe | NDe | 45.5 (5/11) | 0 (1/11) | 72.7 (8/11) | 9.0 (1/11) | ||
| B | 500 | NDe | NDe | NDe | NDe | 92.3 (12/13) | 23.1 (3/13) | 100 (11/11) | 72.7 (8/11) | ||
| B | 5000 | 100 (14/14) | 100 (14/14) | NDe | NDe | 100 (14/14) | 100 (14/14) | 100 (12/12) | 100 (12/12) | ||
| B | 0f | 0 (0/13) | 0 (0/13) | ||||||||
| C | 50 | 70 (7/10) | 70 (7/10) | 75 (9/12) | 66.7 (8/12) | 58.3 (7/12) | 75 (9/12) | 77.8 (7/9) | 77.8 (7/9) | ||
| C | 100 | 88.9 (8/9) | 88.9 (8/9) | 72.7 (8/11) | 72.7 (8/11) | 69.2 (9/13) | 69.2 (9/13) | 90.9 (10/11) | 90.9 (10/11) | ||
| C | 500 | 100 (7/7) | 100 (7/7) | 100 (10/10) | 50 (5/10) | 100 (11/11) | 100 (11/11) | 100 (9/9) | 100 (9/9) | ||
| C | 0f | 0 (0/11) | 0 (0/11) | ||||||||
Protocol I was that of Black et al. (3), protocol II was that of Rennecker et al. (11), and protocol III was that of Atwill et al. (2). Two different methods were used to determine if neonatal mice were infected with C. parvum oocysts: staining of intestinal tract tissue homogenates and histopathology.
Oocysts remaining intact after excystation trials 7, 8, and 9 (Table 1) were used to conduct three independent sets of neonatal-mouse experiments, A, B, and C, respectively.
Fresh bovine genotype A oocysts which were not subject to excystation protocols.
Neonatal mice inoculated with distilled water only.
ND, not done.
Inoculated with distilled water only.