Diagnosis of malignant catarrhal fever by PCR using formalin-fixed, paraffin-embedded tissues.
(9/1489)
A previously described polymerase chain reaction (PCR) assay (amplification of a 238-bp fragment of ovine herpesvirus 2 [OHV-2] genomic DNA) for diagnosis of sheep-associated malignant catarrhal fever (MCF) was adapted for use on formalin-fixed, paraffin-embedded tissues. Variables affecting its use were examined. Archived tissues from cattle, white-tailed deer (Odocoileus virginianus), and bison (Bison bison) diagnosed with MCF by clinical signs or histologic lesions were obtained from 2 veterinary diagnostic laboratories. Tissues from healthy animals and from animals diagnosed with other common bovine viral diseases were examined as controls. A total of 86 blocks from 37 suspect MCF cases were examined. Forty-one blocks from healthy animals and animals with unrelated viral diseases were examined as controls. The assay was specific for sheep-associated MCF and did not yield false-positive signals from healthy animals or from cases of infectious bovine rhinotracheitis, bovine virus diarrhea, mucosal disease, or parainfluenza-3 virus infection. A wide variety of tissues were suitable substrates, including spleen, lymph node, intestine, brain, lung, and kidney. Extracted DNA provided a more suitable target than did unextracted tissue lysate. The highest levels of viral DNA were present in lymphoid organs and intestine, but the data indicate that in acute clinical cases, most organs contain sufficient viral DNA to serve as a suitable diagnostic specimen. Fixation of 0.5-cm3 blocks of tissue in 10% neutral buffered formalin was deleterious to the target DNA, and PCR signals progressively diminished after fixation for >45 days. Detection of genomic DNA of OHV-2 by PCR was successful for archived tissues that were 15 years old. (+info)
Quantitation of sheep-associated malignant catarrhal fever viral DNA by competitive polymerase chain reaction.
(10/1489)
A single-step, competitive polymerase chain reaction technique was developed to quantitate sheep-associated malignant catarrhal fever (SA-MCF) viral DNA. The assay employed coamplification of a fixed quantity of target DNA with graded amounts of a competitor, generated by truncation of the target sequence lying between the 2 primer binding sites. The assay yielded a linear response (r = 0.98) for DNA measurement within the range of 30-300,000 copies. Amplification efficiency analysis by coamplification of target and competitor in equal copy numbers for various numbers of cycles showed that the relative abundance of the coamplified products remained constant with increasing cycle numbers up to 40. Reproducibility was assessed by repetitively assaying a set of blind-coded samples from a variety of animals and tissues. Results indicated that the assay is reliable and reproducible for quantitation of SA-MCF viral DNA in samples from asymptomatically infected sheep and from animals with clinical SA-MCF. (+info)
Complete sequence of enzootic nasal tumor virus, a retrovirus associated with transmissible intranasal tumors of sheep.
(11/1489)
The sequence of the complete genome of ovine enzootic nasal tumor virus, an exogenous retrovirus associated exclusively with contagious intranasal tumors of sheep, was determined. The genome is 7,434 nucleotides long and exhibits a genetic organization characteristic of type B and D oncoviruses. Enzootic nasal tumor virus is closely related to the Jaagsiekte sheep retrovirus and to sheep endogenous retroviruses. (+info)
Characterization of nonenterotoxigenic Escherichia coli strains producing F17 fimbriae isolated from diarrheic lambs and goat kids.
(12/1489)
Forty-five ovine and caprine nonenterotoxigenic Escherichia coli strains producing F17-related fimbriae were characterized with respect to the fimbrial structural subunit and adhesin subtypes produced. In addition, several characteristics related to the virulence of strains producing F17 fimbriae were studied. Most of the strains (73%) possessed the f17cA structural subunit gene, whereas the f17aA and f17dA genes were detected only on three (6%) and two (4%) strains, respectively. The f17bA gene was not detected. All but one of these strains possessed the f17G genes of the adhesin subfamily II. The only strain having the f17G gene of subfamily I possessed the structural subunit gene f17dA. Sequencing of the f17A and f17G genes of four selected strains confirmed the association of f17cA and f17dA structural subunit genes with the f17G genes of the adhesin subfamily II. These results indicated that adhesins of the subfamily II are prominent among ovine and caprine isolates and that they are indistinctly associated with the F17 structural subunit subtypes on these field strains. CS31A- and CNF2-related genes were not detected. Most of the strains adhered in vitro to ovine intestinal brush borders (36 of 45) and agglutinated the erythrocytes of different species in the presence of D-mannose (39 of 45). F17-positive strains produced colicin V (57%) and were resistant to the bactericidal effect of serum (91%) in significantly higher percentages than F17-negative strains (34% produced colicin V, and 66% were serum resistant). Thus, most of the studied ovine and caprine strains showed phenotypic characteristics of septicemic strains. (+info)
Effect of locoweed (Astragalus ientiginosus) feeding of fetal lamb development.
(13/1489)
Locoweed, Astragalus lentiginosus, was fed to pregnant ewes for various periods during gestation. The principal gross effects on the developing fetuses were observed to be delayed placentation, decreased vascularization, fetal edema and hemorrhage, and alteration of cotyledon development. Deformed lambs and undersized lambs also occurred. Data from sheep fed locoweed during various periods of the entire gestation period are summarized and indicate that locoweed poisoning in the fetus as with the adult is a chronic type of intoxication. Also, poisoning of the fetus parallels poisoning in the dam. (+info)
Rumen bacteria are involved in the onset of onion-induced hemolytic anemia in sheep.
(14/1489)
The mechanism of onion-induced hemolytic anemia in ruminants was investigated. The ether-extract obtained from the mixture of rumen fluid and onion juice incubated at 38.5 degrees C for 9 hr induced oxidative damage in sheep erythrocytes in vitro, indicating the production of certain oxidants in the mixture. The increase of the oxidative effect in the mixture was inhibited completely by the removal of rumen microorganisms and partly by treatment with antibiotics and by oxygen gas. The sheep fed onions (50 g/kg body weight/day) for 15 days developed more severe Heinz body hemolytic anemia than did the sheep fed the equivalent amount of onions with 5 g/day ampicillin sodium salt. The results indicated that certain rumen bacteria appear to be involved in the onset of onion-induced hemolytic anemia in sheep. (+info)
Analysis of ruminant respiratory syncytial virus isolates by RNAse protection of the G glycoprotein transcripts.
(15/1489)
Two different respiratory syncytial virus (RSV) radiolabeled probes were used to characterize the genetic heterogeneity of 25 ruminant RSV isolates by the ribonuclease protection assay. A 32P-radiolabeled antisense RNA probe was transcribed from cloned ovine and bovine RSV G glycoprotein genes and then hybridized with total RNA isolated from infected cells with various ruminant RSV isolates. The results of this study, along with previously published nucleotide sequence data of the ovine RSV G glycoprotein gene, suggest the presence of at least 2 ruminant RSV subgroups. One subgroup is represented by RSV isolated from respiratory disease outbreaks from calves and goats, and the other is represented by RSV isolated from sheep. (+info)
Humoral immune response to equine chorionic gonadotropin in ewes: association with major histocompatibility complex and interference with subsequent fertility.
(16/1489)
In dairy ewes, the use of eCG as a convenient hormone for the induction of ovulation is necessary for out-of-season breeding and artificial insemination (AI). In this report we show the presence of anti-eCG antibodies in plasma of treated ewes. The major histocompatibility complex (MHC) was involved in the individual variability of the humoral immune responses to eCG. We found significant associations between the anti-eCG response phenotype and some MHC class II alleles. The low immune response phenotype was associated with one MHC class II allele only in Lacaune ewes, and the high immune response phenotype was associated with one MHC class II allele both in Manech and in Lacaune ewes. In herds, the impact of residual anti-eCG antibodies on subsequent fertility after AI seems minimal because of an indirect elimination of high-responder ewes from AI breeding. Therefore, the true magnitude of the association between residual anti-eCG antibody concentration and fertility has been underestimated. An additional experiment without any high-responder female elimination showed a significant correlation between high residual antibody concentrations and lower lambing rate after AI at a fixed time, possibly because of a delayed preovulatory LH surge. The results suggest that anti-eCG antibody concentration is one risk factor for infertility after AI. (+info)