Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL) offers a variety of testing to assist in working up calf diarrhea cases. The calf diarrhea multiplex PCR—which targets bovine coronavirus, bovina rotavirus A, and Cryptosporidium—has been requested by Texas veterinarians over 1,000 times since 2019. Using TVMDL test results gathered between March 2019 and October 2023, this article provides a brief overview of available epidemiological data from Texas cattle tested using this multiplex PCR.
Animal Demographics & Geographic Locations
Over the 4.5-year period for which data is available (March 2019 – October 2023), TVMDL performed 1,088 calf diarrhea multiplex PCR tests. Samples submitted for this test originated from 108 different counties in Texas. A dot density map representing the geographic distribution of samples is below; each dot represents a single animal tested within that county (and not the exact location within each county).
Exact breed information was provided for 419 (39%) of animals tested; the remainder (669, 61%) were either not specified or listed as crossbred. A breakdown of testing by the number of animals listed as beef breeds, dairy breeds, and crossbred/not specified is as follows:
| Breed Listed on TVMDL Submission Form | Number Tested | Percentage of Total |
|---|---|---|
| Beef Breed | 180 | 16.5% |
| Dairy Breed | 239 | 22.0% |
| Crossbred/Not Specified | 669 | 61.5% |
| TOTAL TESTED | 1088 |
TVMDL accepts feces, intestinal contents, or gastrointestinal tissues as appropriate specimen types for the calf diarrhea multiplex PCR. The sample types tested between 2019 and 2023 are below:
| Sample Type | Number Tested | Percentage of Total |
|---|---|---|
| Feces | 883 | 81.2% |
| Tissue or Other Sample | 205 | 18.8% |
| TOTAL TESTED | 1088 |
Test Positivity by Sample Type
Over 80% (883 out of 1,088) of calf diarrhea multiplex tests between 2019 and 2023 were positive for at least one of the targeted pathogens. A breakdown of pathogen positivity by sample type is below:
| Sample Type | # Tested (%) | # Positive for ≥1 Target (%) | Bovine Coronavirus Positive (%) | Bovine Rotavirus Positive (%) | Cryptosporidium Positive (%) |
|---|---|---|---|---|---|
| Feces | 883 (81.2%) | 719 (81.5% | 215 (29.9%) | 576 (65.2%) | 398 (45.1%) |
| Tissue/Other | 205 (18.8%) | 164 (80.0%) | 74 (36.1%) | 150 (73.2%) | 75 (36.6%) |
| TOTAL | 1088 | 883 (81.2%) | 289 (26.6%) | 726 (66.7%) | 473 (43.5%) |
Bovine Coronavirus
Since March 2019, 289 (27%) of 1,088 samples tested via the calf diarrhea multiplex PCR were positive for bovine coronavirus. Of these positive samples, 78 (27%) were from dairy breeds, 36 (12%) were from beef breeds, and the remainder (175, or 61%) were either crossbred or not specified. The map below shows the total number of tests and percent positivity for bovine coronavirus by county.
Bovine Rotavirus
Out of 1,088 calf diarrhea samples tested at TVMDL between 2019 and 2023, 726 (67%) were positive for bovine rotavirus by PCR. The majority (442, or 61%) of positive samples came from cattle that were either crossbred or did not have breed information specified upon submission to TVMDL; those listed as dairy breeds accounted for 200 samples (27%), and the remainder (84, or 12%) were listed as a beef breed. The map below shows the total number of tests and percent positivity for bovine rotavirus by county.
Cryptosporidium
Between 2019 and 2023, 473 out of 1,088 (43%) calf diarrhea multiplex PCR tests were positive for Cryptosporidium. The breakdown of cattle breeds from which positive samples originated (as listed on the TVMDL submission form) is as follows: 139 or 29.4% were dairy breeds, 44 or 9.3% were beef breeds, and 290 or 61.3% were crossbred or not specified. The map below shows the total number of tests and percent positivity for Cryptosporidium by county.
Coinfections
Of the 883 samples with positive results, 491 (56%) were positive for more than 1 pathogen. A summary of the numbers and types of infections (i.e., both single and coinfections) is below:
For more information about TVMDL’s test catalog, visit tvmdl.tamu.edu or call 1.888.646.5623.