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Abstract
Objective—To evaluate the in vitro activity of an ear rinse (ER) containing tromethamine, EDTA, and benzyl alcohol on bacterial pathogens from dogs with otitis.
Sample Population—Organisms were collected from ear swab specimens from the external and middle ear and included Staphylococcus spp (n = 11; Staphylococcus intermedius [7] and Staphylococcus spp [4]), Pseudomonas aeruginosa (5), Proteus spp (5), β-hemolytic streptococcus (11), and 1 control strain of each organism.
Procedures—3 test solutions were evaluated including EDTA, tromethamine, and benzyl alcohol (ER); EDTA and tromethamine (ER without benzyl alcohol [ER – BA]); and purified water. Ten-milliliter aliquots of each test solution were transferred into 36 tubes and inoculated with one of the organisms. Samples were retrieved from each tube at 0, 15, 30, 45, and 60 minutes, transferred to Petri dishes, mixed with soybeancasein digest agar, and incubated. After incubation, plates were examined for growth, and the number of colonies was expressed as CFU per milliliter.
Results—ER significantly decreased bacterial growth in vitro of P aeruginosa and β-hemolytic streptococcal organisms within 15 minutes, Proteus spp within 30 minutes, and Staphylococcus spp within 60 minutes. Comparatively, the presence of benzyl alcohol in ER significantly decreased bacterial growth of β-hemolytic streptococcus and Proteus spp.
Conclusions and Clinical Relevance—On the basis of results of this study, future studies should be performed to evaluate the in vivo efficacy of ER alone as a treatment for otic infections caused by β-hemolytic streptococcus, P aeruginosa, and Proteus spp and of ER combined with an antimicrobial agent for otic infections caused by Staphylococcus spp.
Abstract
Objective—To test horses for serologic evidence of an association between vesiviral antibodies and abortion.
Sample Population—Sera from 141 horses.
Procedures—2 experiments were conducted. Experiment 1 comprised sera obtained in 2001 and 2002 from 3 groups of horses (58 mares from farms with a history of abortion problems, 25 mares between 3 and 13 years of age with unknown reproductive histories that were sold at auction [breeding-age control mares], and 29 mixed-age males and yearling females sold at auction [negative control population]). Experiment 2 comprised sera from 3 groups of pregnant mares (10 pregnant mares fed Eastern tent caterpillars [ETCs], 9 pregnant mares fed ETC frass only, and 10 pregnant control mares). Sera were analyzed for antibodies against vesivirus by use of a validated recombinant vesivirusspecific peptide antigen in an indirect ELISA.
Results—For experiment 1, 37 of 58 (63.8%) mares from farms with abortion problems were seropositive for vesivirus antibodies, whereas 10 of 25 (40%) breeding-age control mares were seropositive. All 29 mixed-age males and yearling females were seronegative for vesivirus antibodies. For experiment 2, 17 of 29 mares aborted (some from each group). Seropositive status for vesivirus antibodies increased from 47.1% (8/17) to 88.2% (15/17) for the pregnant mares that aborted during the experiment.
Conclusion and Clinical Relevance—Significant association was detected between seropositive status for vesivirus and abortion in mares; consequently, vesivirus appears to be a pathogenic virus associated with abortion in mares. These data support adding vesivirus antibody testing into diagnostic screening to determine the cause for abortion in mares.
Abstract
Objective—To analyze the 7a7b genes of the feline coronavirus (FCoV) of cheetahs, which are believed to play a role in virulence of this virus.
Sample Population—Biologic samples collected during a 4-year period from 5 cheetahs at the same institution and at 1 time point from 4 cheetahs at different institutions.
Procedures—Samples were first screened for FCoV via a reverse transcription-PCR procedure involving primers that encompassed the 3′-untranslated region. Samples that yielded positive assay results were analyzed by use of primers that targeted the 7a7b open reading frames. The nucleotide sequences of the 7a7b amplification products were determined and analyzed.
Results—In most isolates, substantial deletional mutations in the 7a gene were detected that would result in aberrant or no expression of the 7a product because of altered reading frames. Although the 7b gene was also found to contain mutations, these were primarily point mutations resulting in minor amino acid changes. The coronavirus associated with 1 cheetah with feline infectious peritonitis had intact 7a and 7b genes.
Conclusions and Clinical Relevance—The data suggest that mutations arise readily in the 7a region and may remain stable in FCoV of cheetahs. In contrast, an intact 7b gene may be necessary for in vivo virus infection and replication. Persistent infection with FCoV in a cheetah population results in continued virus circulation and may lead to a quasispecies of virus variants.
Abstract
Objective—To determine whether specific strains of Listeria monocytogenes, as determined by genetic characteristics and virulence phenotypes, were associated with distinct clinical manifestations of listeriosis in cattle and thus may potentially have tissue specificity.
Animals—32 cattle.
Procedure—DNA sequence data for the virulence genes actAand inlAwere used to infer the phylogeny of L monocytogenes and to test for positive selection. Isolates were screened for the presence or absence of internalin genes and assigned an internalin profile. Plaquing assays were performed to determine the relative cytopathogenicity of each isolate. Categorical data analyses were performed to describe associations among L monocytogenes genotypes, virulence phenotypes, and clinical manifestations of listeriosis.
Results—Results confirmed that L monocytogenes represents 2 deeply separated evolutionary lineages. Genes actA and inlA contained amino acid sites under positive selection, and specific residues at some sites were associated with lineage and manifestation of listeriosis. Whereas lineage I was clonal and predominantly composed of isolates from cases of encephalitis, lineage II was more genetically diverse and equally represented by isolates from cases of encephalitis versus septicemia and fetal infection. Lineage I isolates also had greater cytopathogenicity in vitro, compared with lineage II isolates.
Conclusions and Clinical Relevance—Results indicated that L monocytogenes virulence genes underwent positive selection that is consistent with the diversification of 2 evolutionary lineages: lineage I is clonal and associated with encephalitis, and lineage II is more genetically diverse and equally likely to cause both major forms of listeriosis in cattle.
Abstract
Objective—To compare incubation time and clinical signs of scrapie in codon 136/171 alanine-valine/gluta-mine-glutamine (AVQQ) experimentally inoculated sheep with that in sheep with the more common 136/171 AAQQ genotype.
Animals—60 Suffolk sheep.
Procedure—Twenty-seven 171 QQ ewes purchased from 2 private flocks were bred with a 171 QQ Suffolk ram before being inoculated with a 20% solution of scrapie-positive brain homogenate (5 mL, PO) from sheep containing genotypes 136/154/171 AA/argi-nine-arginine (RR)/QQ, AVRRQQ, and VVRRQQ that had died of scrapie. Ewes had 33 lambs, which were inoculated in the same manner on the day of birth.
Results—All 16 genotype 136/154/171 AVRRQQ sheep that died of scrapie were 9 to 11 months of age; clinical signs lasted 1 day to 3 weeks with no wasting and only mild pruritus. The first AARRQQ sheep died with typical clinical signs of scrapie 27 months after inoculation, and 14 were still alive 37 to 42 months after inoculation. The 136/171 AVQQ sheep had minimal accumulation of modified cellular protein (PrPSC) as determined by immunohistochemical (IHC) staining within affected cells; thus the severity of clinical signs and time of death were not associated with brain lesions or the amount of PrPSC in brain tissue of 136/154/171 AVRRQQ sheep as determined by IHC staining.
Conclusions and Clinical Relevance—The rapid incubation time may have been influenced by the codon 136 genotype, a new unreported valine (V)-dependent strain of scrapie similar to strain SSBP/1, or the inoculum may have contained a traditional strain and a V-dependent or SSBP/1-like strain of scrapie.
Abstract
Objective—To determine whether Mycoplasma haemofelis (Mhf) and Candidatus Mycoplasma haemominutum (Mhm) can be transmitted by ingestion of Mycoplasma-infected Ctenocephalides felis and by-products (feces, larvae, and eggs).
Animals—10 cats.
Procedure—3 cats were carriers of Mhf, and 1 was a carrier of Mhm. Six cats had negative results of PCR assay for Mhf and Mhm DNA. A chamber containing 100 C felis was bandaged to 2 Mhf carrier cats. Five days later, fleas and by-products were analyzed for Mycoplasma spp DNA. The remaining fleas and a sample of by-products were fed to 2 Mycoplasma-naïve cats. A chamber containing 200 C felis was bandaged to the Mhm carrier cat. Five days later, fleas and by-products were analyzed for Mycoplasma spp DNA. The remaining fleas and a sample of by-products were fed to 2 Mycoplasma-naïve cats. A chamber containing 200 C felis was bandaged to an Mhf carrier cat and Mhm-carrier cat. Three days later, fleas and by-products were analyzed for Mycoplasma spp DNA. The remaining fleas and a random sample of by products were fed to 4 Mycoplasma-naïve cats. All cats were monitored for infection for ≥7 weeks.
Results—Uptake of Mhf and Mhm DNA into fleas and by-products was detected. None of the naïve cats became infected.
Conclusions and Clinical Relevance—Results suggested that ingestion of Mycoplasma-infected C felis or by-products is not an important means of transmission for Mhf or Mhm.
Abstract
Objective—To evaluate the influences of animal age, bacterial coinfection, and porcine reproductive and respiratory syndrome virus (PRRSV) isolate pathogenicity on virus concentration in pigs.
Animals—Twenty-one 2-month-old pigs and eighteen 6-month-old pigs.
Procedure—Pigs were grouped according to age and infected with mildly virulent or virulent isolates of PRRSV. The role of concurrent bacterial infection was assessed by infecting selected pigs with Mycoplasma hyopneumoniae 21 days prior to inoculation with PRRSV. On alternating days, blood and swab specimens of nasal secretions and oropharyngeal secretions were collected. On day 21 after inoculation with PRRSV, selected tissues were harvested. Concentrations of PRRSV were determined by use of quantitative real-time PCR and expressed in units of TCID50 per milliliter (sera and swab specimens) or TCID50 per gram (tissue specimens).
Results—Concentrations of virus were higher in blood and tonsils of pigs infected with virulent PRRSV. Pigs infected with virulent PRRSV and M hyopneumoniae had significantly higher concentrations of viral RNA in lymphoid and tonsillar tissue. Coinfection with M hyopneumoniae resulted in a higher viral load in oropharyngeal swab specimens and blood samples, independent of virulence of the PRRSV isolate. Two-month-old pigs had significantly higher viral loads in lymph nodes, lungs, and tracheal swab specimens than did 6-month-old pigs, independent of virulence of the PRRSV isolate.
Conclusions and Clinical Relevance—Multiple factors affect PRRSV concentration in pigs, including pathogenicity of the PRRSV isolate, age, and concurrent infection with M hyopneumoniae.
Abstract
Objective—To examine sera obtained from dairy and beef cattle to detect antibodies against vesivirus and compare seroprevalence among cattle within the sample population.
Sample Population—Cattle sera from 8 western states and Maryland submitted to the Washington Animal Disease Diagnostic Laboratory during 1999 and 2000.
Procedure—Sera were analyzed for vesivirus-specific antibodies by use of a recombinant vesivirus–San Miguel sea lion virus serotype 5–capsid peptide antigen in an indirect ELISA.
Results—Overall, 693 sera were tested and 105 (15.2%) had positive results. Seropositive cattle were from 7 states (all cattle from Montana and Maryland 10 and 4, respectively were seronegative). Overall seroprevalence for antivesivirus antibody in herds ranged between 0% and 80% (median, 14%). Higher antibody prevalence was significantly associated with older age, dairy rather than beef cattle, and reasons for submission. Logistic regression of factors (abortion, respiratory tract disease, and all other reasons for sample submission) revealed that older age and other reasons were independently associated with higher seroprevalence. Higher seropositive optical density values for the ELISA were observed among older cattle and cattle that aborted, compared with values for cattle with respiratory tract disease or other reasons for submission.
Conclusions and Clinical Relevance—This laboratory-based surveillance sample provided a point estimate of seroprevalence against vesivirus among cattle in 9 US states. This suggests that vesivirus infection is widespread with high prevalence in some herds. Risk factors associated with vesivirus seroprevalence in beef and dairy cattle should be confirmed in population-based studies.
