In February 2004, an HPAI virus was confirmed to have infected a flock of broiler chickens in Gonzales County, Texas. Subsequent epidemiologic investigation identified infected birds in 2 live-bird markets in the area of Houston, Tex; these markets had received birds from the index flock or birds that had been transported by the index flock manager. All infected premises were depopulated, cleaned, and disinfected. Disease surveillance standards were established to assess the potential for spread of this virus from the index flock. Surveillance testing in commercial and noncommercial poultry operations revealed no area spread of virus from the index flock.
Objective—To determine risk factors associated with
hemorrhagic bowel syndrome (HBS) among dairy cattle
in the United States and identify characteristics of
HBS in individual cows.
Design—Cross-sectional, population-based survey.
Sample Population—A stratified random sample of
1,013 dairy operations with ≥ 30 cows located in 21
Procedure—Information on management and animal
health-related topics was collected with a questionnaire.
Results—HBS was estimated to have been observed
on 9.1% of operations during the preceding 5 years and
on 5.1% of operations during the preceding 12 months.
Factors found in multivariable analysis to be associated
with the occurrence of HBS during the preceding 12
months were large herd size, administration of bovine
somatotropin, and routine use of milk urea nitrogen
concentration to determine ration composition. Use of
pasture as part of the lactating cow ration during the
growing season was associated with decreased odds
of HBS in operations with rolling herd average milk production
≤ 20,000 lb, whereas in operations with higher
milk production, use of pasture was not associated with
occurrence of HBS. For individual cows with signs consistent
with HBS, the third lactation was the median of
the parity distribution and the median time between
parturition and the onset of clinical signs was 104 days.
Conclusions and Clinical Relevance—Results suggest
that management practices implemented to achieve
high milk production may increase the risk of developing
HBS in dairy cattle. Increased consumption of a high-energy
diet seems to be the most plausible common
pathway for all of the risk factors that have been
described. (J Am Vet Med Assoc 2005;226:1700–1706)
Objective—To determine effects on production and
risk of removal related to Mycobacterium avium subsp
paratuberculosis (MAP) infection at the individual animal
level in dairy cattle.
Animals—7,879 dairy cows from 38 herds in 16 states.
Procedure—A subset of dairy cattle operations that
participated in the National Animal Health Monitoring
System Dairy 2002 study was evaluated via a serum
ELISA for antibodies against MAP and categorized
according to ELISA score. Dairy Herd Improvement
Association records were obtained to collect current
and historical lactation data and removal (ie, culling)
information. Production variables were evaluated on
the basis of serum ELISA category.
Results—Cows with strong positive results had
mature equivalent (ME) 305-day milk production, ME
305-day maximum milk production, and total lifetime
milk production that were significantly lower than cows
in other categories. No differences were observed for
ME 305-day fat and protein percentages, age, lactation,
and lactation mean linear somatic cell count score
between cows with strong positive results and those
with negative results. After accounting for lactation
number and relative herd-level milk production, cows
with strong positive results were significantly more
likely to have been removed by 1 year after testing.
Conclusions and Clinical Relevance—Without management
changes designed to reduce the farm-level
prevalence of MAP infection, paratuberculosis will continue
to reduce farm income by decreasing milk production
and potentially increasing premature removal from
the herd. (J Am Vet Med Assoc 2005;227:1975–1981)
Objective—To report clinical and serologic findings in
horses with oral vesicular lesions that were consistent
with vesicular stomatitis (VS) but apparently
were not associated with VS virus (VSV) infection.
Design—Serial case study.
Procedure—Horses were quarantined after appearance
of oral lesions typical of VS. Severity of clinical
signs was scored every 2 to 5 days for 3 months.
Serum samples were tested for antibodies by use of
competitive ELISA (cELISA), capture ELISA for IgM,
serum neutralization, and complement fixation (CF).
Virus isolation was attempted from swab specimens
of active lesions.
Results—2 horses with oral vesicular lesions on day
1 had antibodies (cELISA and CF) against VSV; however,
results of CF were negative by day 19. Five of
the 6 remaining horses were seronegative but developed
oral lesions by day 23. Virus isolation was unsuccessful
for all horses.
Conclusion and Clinical Relevance—Horses were
quarantined for 75 days in compliance with state and
federal regulations. However, evidence suggests that
oral lesions were apparently not associated with VSV
infection. The occurrence in livestock of a vesicular
disease that is not caused by VSV could confound
efforts to improve control of VS in the United States
and could impact foreign trade.Vesicular stomatitis is
of substantial economic and regulatory concern. (J
Am Vet Med Assoc 2000;216:1399–1404)
The US dairy industry is moving toward fewer dairy farms with more cattle per farm. Between 1995 and 2005, the number of dairy farms decreased by 43.9% (from 139,670 to 78,295), but the total number of milk cows decreased by only 4.5% (from 9.47 to 9.04 million).1 Consequently, the average herd size for dairies in the United States has almost doubled during the past 10 years.
It has become difficult for dairy farms to be completely self-sufficient, self-contained production units. Large dairy farms are at risk of exposure to disease agents from external sources of labor, feedstuffs, replacement