Experimental transmission of Corynebacterium pseudotuberculosis biovar equi in horses by house flies.

BACKGROUND: The route of Corynebacterium pseudotuberculosis infection in horses remains undetermined, but transmission by insects is suspected. OBJECTIVES: To investigate house flies (Musca domestica L.) as vectors of C. pseudotuberculosis transmission in horses. ANIMALS: Eight healthy, adult ponies. METHODS: Randomized, controlled, blinded prospective study. Ten wounds were created in the pectoral region where cages for flies were attached. Three ponies were directly inoculated with C. pseudotuberculosis. Four ponies were exposed for 24 hours to 20 hours C. pseudotuberculosis-inoculated flies. One negative control pony was exposed to noninoculated flies. Ponies were examined daily for swelling, heat, pain, and drainage at the inoculation site. Blood was collected weekly for CBC and biochemical analysis, and twice weekly for synergistic hemolysis inhibition titers. RESULTS: Clinical signs of local infection and positive cultures were observed in 7/7 exposed ponies and were absent in the negative control. In exposed ponies, peak serologic titers (1:512 to 1:2,048) were obtained between days 17 and 21. Seroconversion was not observed in the negative control. Neutrophil counts were higher in the positive and fly-exposed groups than in the negative control (P = .002 and P = .005) on day 3 postinoculation. Serum amyloid A concentrations were higher in the positive control than in the negative control and fly-exposed ponies on days 3 (P < .0001) and 7 (P = .0004 and P = .0001). No differences were detected for other biochemical variables. CONCLUSIONS AND CLINICAL IMPORTANCE: House flies can serve as mechanical vectors of C. pseudotuberculosis and can transmit the bacterium to ponies.

Efficacy of coarse-spray administration of a reovirus vaccine in young chickens.

Coarse-spray (CS) administration of a commercial S1133 reovirus vaccine in chickens for prevention of clinical viral tenosynovitis (VT) infection was evaluated. In Expt. 1, one-day-old specific-pathogen-free (SPF) white leghorns were vaccinated with a combination of reovirus, Newcastle disease (ND), and infectious bronchitis (IB) vaccines by CS and infectious bursal disease vaccine by the subcutaneous (SQ) route. In Expt. 2, one-day-old commercial broilers were vaccinated by CS with reovirus vaccine and Marek's disease (MD) vaccine by SQ. In Expt. 3, one-day-old commercial broilers received reovirus vaccine in combination with ND-IB vaccines at 1 day of age by CS and MD vaccine by SQ. Some birds received an initial or second vaccination at 7 days of age by CS or the drinking-water (DW) route. Birds vaccinated by CS at 1 day of age with reovirus vaccine did not produce circulating virus-neutralizing antibody against reovirus, although they had resistance to VT infection. In contrast, initial or booster vaccination at 7 days of age by CS or DW resulted in an antibody response and greater resistance to challenge than did CS vaccination at 1 day of age. There was no difference in efficacy between CS and DW routes at 7 days of age. The reovirus vaccine did not interfere with other vaccines as measured by serologic (ND-IB-IBD) or challenge (MD) studies.

Digoxigenin-labeled nucleic acid probe for the detection of infectious bursal disease virus in infected cells.

A cDNA probe was synthesized from the VP-4 region of a virulent field isolate of infectious bursal disease virus (IBDV). The probe was labeled during synthesis with a non-radioactive steroid hapten, digoxigenin. The probe was used to develop a hybridization assay to detect the presence of IBDV in infected cell-culture and tissue suspensions from the bursa of Fabricius of infected chickens. The test was rapid, reproducible, and sensitive, and it could detect four serologic subtypes of IBDV, including the GLS-5 isolate.

Tissue-print hybridization using a non-radioactive probe for the detection of infectious bursal disease virus.

Tissue-print hybridization was evaluated as a simplified means for detection of infectious bursal disease virus (IBDV) in the bursa of Fabricius from infected chickens. The assay employed a biotin-labeled synthetic oligonucleotide as a probe. The bound probe was detected using a color assay consisting of streptavidin conjugated to alkaline phosphatase. Bursae were imprinted onto nitrocellulose and then hybridized with the biotinylated probe. Bursal prints from IBDV-infected chickens were readily distinguished from control prints by color development and differences in signal intensity.

Effect of a live reovirus vaccine on reproductive performance of broiler breeder hens and development of viral tenosynovitis in progeny.

A live commercial reovirus vaccine, Enterovax, was administered to adult broiler breeder hens via the drinking water to determine its efficacy in stimulation of circulating antibody. This vaccine was compared with a commercial inactivated reovirus vaccine. Only the inactivated product resulted in increased antibody as measured by a commercial enzyme-linked immunosorbent assay. However, the live reovirus vaccine caused diarrhea in the hens and decreased eggshell quality, fertility, and hatchability. In addition, the live vaccine virus was vertically transmitted from hens to their progeny, resulting in increased embryonic mortality and viral tenosynovitis.

The prevalence of Aeromonas species in feces of horses with diarrhea.

Feces collected from 40 horses with diarrhea and 34 horses without diarrhea were examined to determine if an association existed between isolation of Aeromonas spp. and diarrhea. Samples were also examined for Salmonella spp., and identification of viruses and parasite ova. Neither Salmonella spp. nor Aeromonas spp. were isolated from the feces of 34 control horses. Aeromonas spp. were isolated from feces of 22 of 40 (55%) horses with diarrhea. Salmonella spp. were isolated from feces of 8 (20%) horses, and of these, 5 (12.5%) were also positive for Aeromonas spp. Twenty-nine isolates of Aeromonas spp. were recovered from the feces of 22 diarrheic horses. Of these isolates, more than 80% were susceptible on in vitro testing to amikacin, ceftiofur, chloramphenicol, and gentamicin. All isolates were susceptible to enrofloxacin. Diarrheic horses positive for Aeromonas were significantly (P = .04) older than diarrheic horses negative for Aeromonas spp. A significantly greater number of fecal samples were positive for Aeromonas spp. during March through August than samples examined in other months (P = .014). Results of this study indicate that Aeromonas spp. should be considered as a cause of diarrhea in horses.

Listeria monocytogenes septicemia in a foal.

Listeria monocytogenes is rarely reported as a cause of septicemia in foals. In this case, the foal had diarrhea 2 weeks prior to the onset of signs of lethargy, high rectal temperature, and leukopenia with a left shift. Listeria monocytogenes was isolated from the blood culture. The most commonly isolated organism causing septicemia in foals is Escherichia coli. Without the blood cultures, a definitive diagnosis would not have been possible.

Evaluation of surgical scrub and antiseptic solutions for surgical preparation of canine paws.

The purpose of the prospective study reported here was to evaluate surgical preparation of canine paws. Three combinations of surgical scrub solutions and antiseptic solutions were used: (1) 7.5% povidone-iodine scrub/10% povidone-iodine solution; (2) 2% chlorhexidine acetate scrub/2% chlorhexidine diacetate solution; and (3) tincture of green soap/70% isopropyl alcohol. The control was warm (38 to 42 C) tap water. Four microbial colony counts were used to evaluate surgical preparation of 4 paws of 8 dogs. Specimens were obtained from the paws for a baseline microbial flora count. After surgical scrub was performed, additional specimens were obtained for bacteriologic culturing. Antiseptic was applied followed by collection of another specimen for bacteriologic culturing. A final specimen was obtained following a 24-hour period under a sterile occlusive bandage. The 3 scrub solutions and the tap water control resulted in lower colony counts following scrubbing of the paws; however, only the 3 antiseptic solutions resulted in further colony count reduction after their application. Evaluation of residual colony counts isolated from specimens taken after a 24-hour period under a sterile occlusive bandage revealed chlorhexidine and povidone-iodine scrub/antiseptic combinations to be similar in antibacterial activity, with significantly (P less than or equal to 0.05) lower colony counts than those from specimens of paws treated with either the tincture of green soap/isopropyl alcohol combination or the tap water control. The lack of a significant difference between the bacterial counts immediately after surgical preparation with povidone-iodine and chlorhexidine and their respective 24-hour residual counts, indicated no particular advantage to surgical preparation and occlusive bandaging 24 hours prior to surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Reproductive and economic impact following controlled introduction of cattle persistently infected with bovine viral diarrhea virus into a naive group of heifers.

The reproductive impact following controlled introduction of animals persistently infected (PI) with bovine viral diarrhea virus (BVDV) was evaluated in BVDV-naive heifers. Heifers were randomly allocated into two groups: an unexposed control herd (n = 34) and a herd exposed to five persistently infected (PI) animals for 7 mo, beginning 50 days before the breeding season (n = 34). Initiation of the BVDV-challenge was timed to mimic either direct contact with PI calves born in the previous calving season or accidental introduction of PI herd additions prior to the breeding season. The PI animals represented BVDV Types 1a (n = 3), 1b (n = 1) and 2 (n = 1). Two BVDV-free, seropositive bulls were used in each group for 78 days breeding seasons. In both groups, 33 of 34 heifers became pregnant, with similar distribution of fetal ages. Two heifers in each group aborted (etiology undetermined). In addition, one calf was born dead and one calf died 3 days post-partum in the BVDV-exposed group. One calf in the unexposed group died 4 mo post-partum. No calves, including the stillborn calf and the two calves that died prior to weaning, were persistently infected with BVDV. In summary, introduction of PI cattle to a group of BVDV-naive heifers 50 days prior to the breeding season did not negatively impact reproductive performance. To the contrary, the active immunity that developed following field exposure to BVDV provided effective reproductive and fetal protection during the breeding season and subsequent gestations, despite continuous exposure to PI animals until approximately midgestation. Although BVDV can have potentially devastating reproductive effects, timing of infection is a critical determinant in the outcome of a BVDV infection. A controlled breeding season with introduction of herd additions at less critical reproductive time points can mitigate the negative reproductive health consequences of BVDV.

Bovine rumenitis - liver abscess complex: a bacteriological review.

Fusobacterium necrophorum is considered to be a member of the normal rumen flora and is the primary etiologic agent of bovine liver abscesses. Of the three biotypes of F. necrophorum, A, B, and C, only biotypes A and B have been implicated in the disease. Type B is the predominant biotype isolated from ruminal lesions and type A is the predominate biotype isolated from liver abscesses. Type A is usually found in pure culture in the liver abscesses; whereas, type B is usually found in mixed culture with either type A or with other bacterial species. Corynebacterium pyogenes, Streptococcus spp., Staphylococcus spp., and Bacteroides spp. are the most prevalent bacteria recovered from mixed cultures. Corynebacterium pyogenes is the most common species isolated and can cause disease synergistically with type B isolates.