Objective—To compare economic outcome for herds
not exposed to Neospora caninum with that for herds
with various seroprevalences of N caninum infection
and evaluate 3 control strategies.
Design—Economic simulation model.
Sample Population—Beef herds with various seroprevalences
of N caninum infection.
Procedure—A 5-year simulation model was used.
Control strategies that were evaluated included
culling females that fail to calve, selling seropositive
females and purchasing seronegative replacements,
and excluding the daughters of seropositive dams as
Results—For a 5-year period with low prices for feeder
calves, endemic N caninum infection decreased
mean return to fixed assets by 22.2% when true seroprevalence
was 10% and by 29.9% when true seroprevalence
was 70%. Percentage decrease in return to
fixed assets was less dramatic when a 5-year period
with high prices for feeder calves was evaluated.
Analysis indicated that 2 control strategies (culling
females that fail to give birth to a calf and selling
seropositive female cattle and purchasing seronegative
replacement female cattle) were not likely to be economically
beneficial. The third control strategy (testing
the entire herd for N caninum infection and excluding
the female offspring of seropositive dams as replacements)
appeared to be a reasonable control strategy.
Conclusions and Clinical Relevance—For the
assumptions in the model, endemic N caninum infection
decreases return to fixed assets for cow-calf
herds. Of the potential control strategies evaluated,
testing the entire herd for N caninum infection and
excluding the daughters of seropositive dams as
potential replacements provided the best economic
return. (J Am Vet Med Assoc 2004;224:1597–1604)
Objective—To determine whether somatic cell
counts (SCCs) or California mastitis test (CMT) scores
for individual quarter milk samples could be used to
detect subclinical intramammary infection among
dairy cattle in a herd with a high bulk tank SCC.
Design—Prospective clinical trial.
Animals—278 Holstein-Friesian dairy cattle from a
Procedure—Individual quarter milk samples were collected
and submitted for bacterial culture, California
mastitis testing, and determination of SCC. Additional
milk samples were collected 34 days later and submitted
for bacterial culture.
Results—During the initial visit to the herd, milk samples
were collected from all 278 cows. However,
because of blind mammary quarters or missing data,
results for 1,057 quarter milk samples were included.
Bacterial culture did not yield any growth for 622
(58.8%) of these samples. Regardless of the cutoff
that was used, sensitivity of the CMT score was ≤ 0.50
and sensitivity of the SCC linear score (SCS) was
≤ 0.60. For 497 mammary quarters, results of bacterial
culture of samples collected 34 days apart were concordant;
bacterial culture did not yield any growth for
342 (68.8%) of these quarters. Regardless of the cutoff
that was used, sensitivity of the CMT score was
≤ 0.61 and sensitivity of the SCS was ≤ 0.76 for mammary
quarters with concordant bacterial culture results.
Conclusions and Clinical Relevance—Results suggest
that neither CMT score nor SCC is sensitive
enough to be useful as a screening test for identifying
infected mammary quarters among dairy cattle in a
herd with high bulk tank SCC. ( J Am Vet Med Assoc 2004;224:419–423)