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- Author or Editor: J. M. Gay x
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Summary
Samples were obtained for bacteriologic culturing of salmonellae from cows and calves on, and the environment of, a large California dairy that used free-stall housing and a flush system for manure handling. Two years previously, the dairy had an outbreak of clinical salmonellosis in the lactating herd; however, since that time, it had not had problems with clinical salmonellosis. On the basis of mean annual milk production per cow, this dairy was consistently ranked in the top 25% of dairies in the area enrolled in the Dairy Herd Improvement Association. Results of bacteriologic culture of 76% (108/142) of environmental samples and 48% (639/1,339) of fecal samples were positive for salmonellae. Eighty-two percent of the isolates were serovar C1, subclassified as Salmonella montevideo, and 17% were serovar E. Results of bacteriologic culture of 85% of samples of recycled flush water being pumped into the free-stall alleys were positive, as were results of bacteriologic culture of 78% of samples of herd bulk milk filters, 97% of fecal samples collected from calves being fed nonsalable milk, and 25% of fecal samples collected from cows at the time of breeding. These findings suggest that freedom from clinical salmonellosis and comparatively high measures of herd performance do not indicate the absence of salmonellae from a premises, and that hardy infectious agents transmitted by ingestion of feces can become established in the environment of modern free-stall dairies that use recycled water in their manure flush systems.
Abstract
Muscle potentials evoked by stimulation of the sciatic nerve were evaluated in 4- and 15-week-old chickens. Each bird was anesthetized and slowly cooled externally from a normal body temperature of 40 C to 28 C, and motor nerve conduction velocities were measured at various intervals during cooling. Motor nerve conduction velocity decreased linearly with decreasing limb temperature in both groups. The rate of change in motor nerve conduction velocity per degree in 2 groups (2.13 m/s/C vs 1.84 m/s/ C) fell just short of a statistically significant difference (P = 0.0508), indicating that an age-related effect on temperature-associated variation in motor nerve conduction velocity may be present.
Summary
An epizootic of subclinical and clinical mastitis caused by Serratia marcescens was investigated in a 1,000-cow dairy farm in California. Serratia marcescens was isolated from 13 to 18% of composite milk samples obtained from lactating dairy cows. During monthly milk sampling performed during a 4-month period, S marcescens was isolated from 38.8 to 62.3% of composite milk samples obtained from cows from which S marcescens was previously isolated. Few cows infected with S marcescens had evidence of clinical mastitis. Somatic cell count value was associated with isolation of S marcescens. Cows with somatic cell counts > 500,000 were 5.48 times as likely to have intramammary infections with S marcescens, compared with cows with somatic cell count ≤ 500,000. Lactation number also was associated with S marcescens intramammary infection. After adjusting for the effect of lactation number, cows with high somatic cell count values were 2.98 times as likely to have intramammary infection with S marcescens, compared with cows with low somatic cell counts. Infection with S marcescens was independent of days in lactation, production string, and daily milk production. Eleven months after the beginning of the epizootic, S marcescens was isolated from organic bedding samples obtained from the dairy. Despite numerous attempts, other sources of S marcescens could not be identified on this dairy.
Abstract
Objective
To examine cross-reactivity among Neospora caninum and closely-related apicomplexans.
Design
Sera from animals were examined for antibody production to N caninum and cross-reactivity to Toxoplasma gondii.
Animals
Cattle were experimentally infected with 3 tissue cyst-forming protozoan parasites N caninum, T gondii, and Sarcocystis sp, and calves were monospecifically inoculated with the intestinal coccidia, Eimeria bovis and Cryptosporidium parvum. Similar studies were done in laboratory rabbits inoculated with N caninum, T gondii, Hammondia hammondi, and Sarcocystis sp. Additionally, sera were obtained from ewes, lambs, goats, sows, cats, rats, and mice inoculated with N caninum tachyzoites.
Procedure
The indirect fluorescent antibody (IFA) and ELISA antibody tests (cattle only) were used to examine reactivity to N caninum; the modified direct agglutination, Sabin-Feldman dye, and IFA tests were used to evaluate reactivity to T gondii.
Results
Serologic cross-reactivity among N caninum, T gondii, and Sarcocystis sp was none or minimal by the IFA test. There was some reactivity to N caninum by the use of ELISA in cattle inoculated with Sarcocystis sp.
Conclusions
The IFA test for N caninum was specific for the diagnosis of neosporosis in animals.(Am J Vet Res 1996;57:329-336)
