Objective—To estimate potential spread of foot-and-mouth disease (FMD) if introduced from wild pigs in California and to evaluate efficacies of various control strategies.
Sample Population—Data for California livestock and from hunter surveys on wild pigs in California.
Procedures—A spatial, stochastic simulation model was used to simulate FMD epidemics that might occur if a dairy or beef herd were infected from contact with a wild pig. Index herd location and type were examined, in addition to different statewide movement ban (SWMB) durations, to determine their effect on extent of the epidemic.
Results—Duration, number of infected premises, size of simulated outbreak, number of culled animals, and spatial distribution of infected herds resulting from the simulated outbreaks varied considerably among geographic regions, depending on index case type and location. Outbreaks beginning in the southern region of California were consistently longest, whereas those beginning in the northern region were shortest. The largest outbreaks resulted from index cases located in the southern and valley regions, whereas outbreaks were smallest when originating in the Sonoma or northern regions. For all regions, when the index herd was a dairy herd, size and duration of the outbreak were consistently reduced with implementation of an SWMB ≥ 3 days.
Conclusions and Clinical Relevance—Introduction of FMDV from wild pigs into a dairy or beef herd could result in a large and rapidly spreading outbreak, potentially affecting large numbers of herds. Size and duration of the outbreak might be reduced with an SWMB; however, the impact is highly dependent on the index herd type and location.
Objective—To determine within a cat shelter effects of dietary lysine supplementation on nasal and ocular disease and detection of nucleic acids of Chlamydophila felis, feline calicivirus (FCV), and feline herpesvirus (FHV-1).
Animals—261 adult cats.
Procedures—Cats were fed a diet containing 1.7% (basal diet; control cats) or 5.7% (supplemented diet; treated cats) lysine for 4 weeks. Plasma concentrations of lysine and arginine were assessed at the beginning (baseline) and end of the study. Three times a week, cats were assigned a clinical score based on evidence of nasal and ocular disease. Conjunctival and oropharyngeal swab specimens were tested for FHV-1, FCV, and C felis nucleic acids once a week.
Results—Data were collected from 123, 74, 59, and 47 cats during study weeks 1, 2, 3, and 4, respectively. By study end, plasma lysine concentration in treated cats was greater than that in control cats and had increased from baseline. There was no difference between dietary groups in the proportion of cats developing mild disease. However, more treated cats than control cats developed moderate to severe disease during week 4. During week 2, FHV-1 DNA was detected more commonly in swab specimens from treated versus control cats.
Conclusions and Clinical Relevance—Dietary lysine supplementation in the amount used in our study was not a successful means of controlling infectious upper respiratory disease within a cat shelter. Rather, it led to increases in disease severity and the incidence of detection of FHV-1 DNA in oropharyngeal or conjunctival mucosal swab specimens at certain time points.
Objective—To compare pathogenicity of an emergent abortifacient Campylobacter jejuni (IA 3902) with that of reference strains after oral inoculation in pregnant guinea pigs.
Animals—58 pregnant guinea pigs.
Procedures—12 animals were challenged IP with C jejuni IA 3902 along with 5 sham-inoculated control animals to confirm abortifacient potential. Once pathogenicity was confirmed, challenge via oral inoculation was performed whereby 12 guinea pigs received IA 3902, 12 received C jejuni isolated from ovine feces (OF48), 12 received a fully sequenced human C jejuni isolate (NCTC 11168), and 5 were sham-inoculated control animals. After abortions, guinea pigs were euthanized; samples were collected for microbial culture, histologic examination, and immunohistochemical analysis.
Results—C jejuni IA 3902 induced abortion in all 12 animals following IP inoculation and 6 of 10 animals challenged orally. All 3 isolates colonized the intestines after oral inoculation, but only IA 3902 induced abortion. Evidence of infection existed for both IA 3902 and NCTC 11168; however, C jejuni was only recovered from fetoplacental units of animals inoculated with IA 3902. Immunohistochemical analysis localized C jejuni IA 3902 infection to subplacental trophoblasts, perivascular tissues, and phagocytes in the placental transitional zone.
Conclusions and Clinical Relevance—This study revealed that C jejuni IA 3902 was a unique, highly abortifacient strain with the ability to colonize the intestines, induce systemic infection, and cause abortion because of its affinity for the fetoplacental unit. Guinea pigs could be effectively used in the study of septic abortion after oral inoculation with this Campylobacter strain.
Objective—To determine prevalence of within-household sharing of fecal Escherichia coli between dogs and their owners on the basis of pulsed-field gel electrophoresis (PFGE), compare antimicrobial susceptibility between isolates from dogs and their owners, and evaluate epidemiologic features of cross-species sharing by use of a questionnaire.
Sample Population—61 healthy dog-owner pairs and 30 healthy control humans.
Procedures—3 fecal E coli colonies were isolated from each participant; PFGE profiles were used to establish relatedness among bacterial isolates. Susceptibility to 17 antimicrobials was determined via disk diffusion. A questionnaire was used to evaluate signalment, previous antimicrobial therapy, hygiene, and relationship with dog.
Results—A wide array of PFGE profiles was observed in E coli isolates from all participants. Within-household sharing occurred with 9.8% prevalence, and across-household sharing occurred with 0.3% prevalence. No behaviors were associated with increased clonal sharing between dog and owner. No differences were found in susceptibility results between dog-owner pairs. Control isolates were more likely than canine isolates to be resistant to ampicillin and trimethoprim-sulfamethoxazole. Owners and control humans carried more multdrug-resistant E coli than did dogs.
Conclusions and Clinical Relevance—Within-household sharing of E coli was detected more commonly than across-household sharing, but both direct contact and environmental reservoirs may be routes of cross-species sharing of bacteria and genes for resistance. Cross-species bacterial sharing is a potential public health concern, and good hygiene is recommended.
Objective—To characterize the influence of the viral protein Npro on virulence of bovine viral diarrhea virus (BVDV) and on type I interferon responses in calves.
Animals—10 calves, 4 to 6 months of age.
Procedures—BVDV virulence and type I interferon responses of calves (n = 5) infected with a noncytopathic BVDV with a deleted Npro were compared with those of calves (5) infected with a noncytopathic BVDV with a functional Npro. Rectal temperatures, clinical signs, platelet counts, and total and differential WBC counts were evaluted daily. Histologic examinations and immunohistochemical analyses of tissues were conducted to assess lesions and distribution of viral antigens, respectively. Serum type I interferon concentrations were determined.
Results—Calves infected with Npro-deleted BVDV developed leukopenia and lymphopenia, without developing increased rectal temperatures or lymphoid depletion of target lymphoid organs. There was minimal antigen deposition in lymphoid organs. Calves infected with Npro BVDV developed increased rectal temperatures, leukopenia, lymphopenia, and lymphoid depletion with marked BVDV antigen deposition in lymphatic tissues. Interferon type I responses were detected in both groups of calves.
Conclusions and Clinical Relevance—Deletion of Npro resulted in attenuation of BVDV as evidenced by reduced virulence in calves, compared with BVDV with a functional Npro. Deletion of Npro did not affect induction of type I interferon. The Npro-deleted BVDV mutant may represent a safe noncytopathic virus candidate for vaccine development.
Objective—To develop a PCR assay for Candidatus Mycoplasma haemolamae (CMhl) infection in alpacas and use it to study the efficacy of oxytetracycline treatment and development of a subclinical carrier state.
Animals—8 healthy adult alpacas.
Procedures—Alpacas initially had negative results for CMhl in blood samples via PCR assay and were experimentally infected with CMhl; 4 were treated with oxytetracycline, and 4 were not treated. All were monitored regularly via PCR assay, blood smear examination, PCV, rectal temperature, and physical examination. At 6 months after treatment, all alpacas were immunosuppressed by administration of dexamethasone and tested for CMhl.
Results—7 of 8 alpacas had positive PCR assay results 4 to 6 days after experimental infection. When organisms were detectable on a blood smear, they were seen 2 to 6 days after positive results of PCR assay. Infection was often associated with mild anemia that was usually transient. No alpacas became hypoglycemic. Oxytetracycline treatment was not associated with faster clearance of organisms or resolution of anemia, and 4 of 4 treated alpacas still had positive results of PCR assay when immunosuppressed 6 months later; 0 of 3 nontreated alpacas had positive results of PCR assay following immunosuppression. Transient fever was detected in 3 alpacas during immunosuppression.
Conclusions and Clinical Relevance—The PCR assay was more sensitive than blood smear examination for detection of infection. Clinical signs, anemia, and fever were not necessarily associated with infection. Oxytetracyline administration did not consistently clear CMhl infection. Although treated with oxytetracycline, infected alpacas remained chronic carriers.
Objective—To evaluate the use of RNA interference targeted against feline herpesvirus 1 (FHV-1) glycoprotein D for inhibition of FHV-1 infection of feline kidney cells.
Sample Population—Crandell-Rees feline kidney cells.
Procedures—Crandell-Rees feline kidney cells were transfected with small interfering RNAs (siRNAs) that were designed to inhibit expression of FHV-1 glycoprotein D. The effectiveness of the treatment was determined via measurement of amounts of glycoprotein D mRNA, intracellular glycoprotein D, and glycoprotein D expressed on the surface of infected cells and comparison with appropriate control sample data.
Results—2 of 6 siRNAs tested were highly effective in reducing expression (ie, knockdown) of glycoprotein D mRNA; there were 77% and 85% reductions in mRNA in treated samples, compared with findings in the control samples. The knockdown of glycoprotein D mRNA resulted in reduced glycoprotein D protein production, as evidenced by 27% and 43% decreases in expression of glycoprotein D on the surface of siRNA-treated, FHV-1–infected cells and decreased expression of the protein within infected cells, compared with control samples. Treatment with these siRNAs also resulted in inhibition of FHV-1 replication, with reductions of 84% and 77% in amounts of virus released into cell culture supernatant, compared with findings in control samples.
Conclusions and Clinical Relevance—2 chemically produced siRNAs that targeted the glycoprotein D gene significantly reduced FHV-1 titers in treated cells, suggesting that glycoprotein D is necessary for production of infective virions. This gene is a potential target for RNA interference as a means of inhibition of FHV-1 infection of feline cells.
Objective—To determine the prevalence of Mycoplasma suis infection in swine, swine-farm workers, and swine veterinarians in Shanghai, China.
Sample Population—172 swine and 65 workers and veterinarians from 19 commercial swine farms.
Procedures—Blood samples were collected from all study subjects. Blood samples were examined for the presence of M suis by means of compound and scanning electron microscopy. A species-specific PCR assay was developed for detection of M suis DNA extracted from blood samples. Relationships between infection status of swine and sex, age, geographic location, and clinical signs of disease were evaluated by use of a C2 test. The phylogenetic relationship between partial 16S ribosomal RNA (rRNA) sequences from swine and human isolates of M suis was determined.
Results—86% (148/172) of swine and 49% (32/65) of humans had positive PCR assay results for M suis infection. Swine infection status was not associated with any variable, with the exception of pyrexia and subcutaneous bleeding. The partial 16S rRNA sequences from human and swine isolates of M suis were 98% homologous and in the same phylogenetic cluster as a previously identified swine isolate of M suis.
Conclusions and Clinical Relevance—A large proportion of swine and humans in close contact with those swine were infected with M suis in Shanghai, China. The close phylogenetic relationship between swine and human isolates of M suis suggested possible interspecies transmission; however, additional research is required to better assess that possibility.
Objective—To evaluate the stability and retention of viscous formulations of the antifungal drug clotrimazole in vitro and to evaluate retention times, absorption, and histologic response to these compounds when placed in the frontal sinus of dogs.
Animals—6 male Beagles.
Procedures—1% clotrimazole gels were formulated with hydroxypropyl cellulose, poloxamer, and carboxymethylcellulose sodium bases. Commercially available 1% clotrimazole creams were also evaluated. Each compound was incubated at 37°C in a funnel. Volume retained and clotrimazole stability were evaluated for 4 weeks. Six compounds were then chosen for in vivo evaluation. The frontal sinuses of 6 dogs were filled with 1 of the 6 compounds. Computed tomographic evaluation was performed weekly for up to 4 weeks to evaluate gel retention. Blood samples were collected to evaluate clotrimazole absorption. Following euthanasia, sinuses were examined histologically.
Results—Commercially available clotrimazole creams were not retained in funnels in vitro. In vivo, hydroxypropyl cellulose– and carboxymethylcellulose-based gels resulted in the most severe inflammatory response and were retained the longest. Poloxamer-based gels had a shorter retention time and were associated with less inflammation. Clotrimazole was minimally absorbed. Despite a marked inflammatory response to several of the clotrimazole-containing gels, no notable adverse clinical responses were observed.
Conclusions and Clinical Relevance—Poloxamer gels had the most promise for improving drug contact within the frontal sinus of dogs, while limiting the inflammatory response. Poloxamer gels have the additional benefit of improved handling as a result of reverse gelation (ie, they gel when warmed to 37°C).
Objective—To evaluate the effect of vaccination of calves with a killed Mycobacterium avium subsp paratuberculosis (MAP) vaccine on colonization of tissues following oral MAP exposure.
Animals—12 healthy Holstein calves.
Procedures—At 14 days after birth, calves received the MAP vaccine (1.0 mL, SC) or saline (0.9% NaCl) solution (1.0 mL, SC [control treatment]). Each calf received 1.2 × 109 CFUs of live MAP orally 21 and 22 days after vaccination. Prior to vaccination and at subsequent intervals, a blood sample was collected for ELISA detection of antibodies against MAP and for whole blood, antigen-specific, interferon (IFN)-γ–release assay. Nine weeks after MAP challenge, calves were euthanized and various tissue samples were collected for mycobacterial culture. Interferon-γ production in prescapular lymph node cells was measured following in vitro stimulation with MAP antigens.
Results—Calves were seronegative for anti-MAP antibodies at all times. Compared with the findings in control calves, antigen-specific IFN-γ production in circulating lymphocytes and prescapular lymph node cells from vaccinated calves was significantly higher. Culture of tissues from vaccinated calves yielded significantly fewer CFUs of MAP (2,417 CFUs/g), compared with tissues from control calves (15,709 CFUs/g). Furthermore, significantly fewer tissue samples from vaccinated calves yielded MAP in culture (21.8 tissues/calf), compared with findings in control calves (27.6 tissues/calf).
Conclusions and Clinical Relevance—Inoculation of calves with a killed MAP vaccine was associated with reduced colonization of intestinal tissues following experimental exposure to MAP. Use of the vaccine could potentially reduce transmission of MAP to calves in infected herds.