Steen Bech-Nielsen

Diagnostic performance of two serologic tests and fecal culture for subclinical paratuberculosis, and associations with production

Abstract A sample of three dairy herds served by the same private veterinary practice was selected on the basis of similarrity of size, calf-rearing practices and owner cooperation. All animals were tested for paratuberculosis three or four times at 6-month intervals by fecal culture, enzyme-linked immunosorbent assay (ELISA), agar-gel immunodiffusion (AGID) serology. Fecal-culture results were reported to herd owners through their veterinary practitioner. Production data and somatic-cell counts were collected from two of the herds using DHI (Dairy Herd Improvement, Powell, OH) records. Sensitivity and specificity relative to fecal culture of single test results were 71% and 83% for ELISA and 38% and 100% for AGID, respectively. Repeated tests gave sensitivity and specificity of 73% and 61% for ELISA and 33% and 100% for AGID when tests were interpreted in parallel testing. A maximum-likelihood procedure was used to generate estimates of sensitivity and specificity of single (91% and 82%) and repeated (73% and 66%) ELISA testing. There were no significant differences by sign test between fecal culture and ELISA in the time period which infection was first identified (P=0.38). Fecal culture detected infection earlier than AGID. Mean milk production (controlling for differences in somatic-cell counts) was 3275 lbs. per lactation or 18.8% higher in fecal culture-negative cows than in fecal culture-positive cows. No associations were found between milk production and ELISA results.

Identification by transfer blot of antigens reactive in the Enzyme-Linked Immunosorbent Assay (ELISA) in rabbits immunized and a calf infected with cryptosporidium SP.

Soluble and particulate fractions of Cryptosporidium sp. oocysts from cattle were obtained by homogenization and sonication. Electrophoresis of the soluble fraction in polyacrylamide gels with sodium dodecyl sulfate and silver staining revealed the presence of 41 bands. Enzyme-linked immunosorbent assay (ELISA) of sera from rabbits immunized with either fraction and from a calf 40 days after infection showed that the animals produced specific antibodies. Enzyme-linked immunoelectrotransfer blot tests revealed the presence of five antigens with the rabbit sera and nine with the calf serum. ELISA proved to be an appropriate test for diagnosis of cryptosporidiosis. Selection of reactive antigens may improve the quality of diagnosis and/or reveal the presence of protective materials in the parasite.

A CASE STUDY OF AN OUTBREAK OF AFRICAN SWINE FEVER IN SPAIN.

This report represents a case study of an outbreak of African swine fever (ASF) that took place in the autonomic region of Extramadura, Badajoz Province, during the month of August, 1992, and aims to describe the Spanish ASF eradication programme as carried out in the field at producer level. Extensive husbandry methods used in the management of Iberian pigs in ASF endemic areas of Spain (about 4% of Spanish territory in 4/52 provinces) makes eradication particularly difficult. Since there is no vaccine available for ASF, the identification and slaughter of carrier animals is crucial to the control of the disease. A case of ASF, which caused one secondary outbreak, was diagnosed on 26 August 1992 and is described in terms of case history, laboratory examination, disease eradication measures and epidemiological observations. Additional evidence is presented in an attempt to evaluate and gain an understanding of the long-term risk of carrier animals, wild European pigs, vector ticks and biting flies as a cause of the persistence in endemic areas of recrudescence of ASF in areas from which the disease was previously eradicated.

Laboratory diagnosis and disease occurrence in the current African swine fever eradication program in Spain, 1989–1991

Abstract The purpose of this study was to determine the rate of decline and geographical distribution by municipality of clinical and subclinical African swine fever (ASF) in the affected areas of Spain. A second aim was to evaluate the performance of diagnostic tests in the Spanish ASF eradication program. Clinical outbreaks were confirmed using both the direct and indirect immunofluorescence test (and if both were negative, by the hemabsorption test). The serological status of swine was determined by an enzyme-linked immunosorbent assay (ELISA) and suspect serum samples were confirmed by the immunoblot assay. The number of clinical outbreaks (herds) of ASF for 1989, 1990 and 1991 was 170, 347 and 207, respectively. The numbers of municipalities within each affected province experiencing acute outbreaks for the same time periods were 49, 69 and 48, respectively. Serologically diagnosed animals positive for ASF were 1.1% of animals tested in 1989, 0.5% in 1990 and 0.8% in 1991. The corresponding positive predictive values of the standard ELISA test used were 99.0, 97.9 and 98.8, respectively. Similarly, the number of municipalities within each affected province experiencing serologically positive subclinically infected animals was 269, 178 and 147 for each of the years 1989, 1990 and 1991, respectively.

Benefit-cost analysis of the current African swine fever eradication program in Spain and of an accelerated program

Abstract We predicted the rate of spread and economic losses due to African swine fever (ASF) infections in Spanish swine for a 20 year period using current epidemiological data. Two possibilities for eradication were examined: continuation of the eradication program presently in use, assuming continued funding at present levels, and an accelerated eradication program using more frequent testing to identify seropositive carrier animals. Both programs theoretically would result in the eradication of African swine fever. The calculated benefit-cost ratios were 1.23 and 1.47 respectively. A reduction in current yearly funding would result in a benefit-cost ratio of 0.97, making the program unprofitable according to our model. The projected year for the eradication of outbreaks is 1996 using provinces as units in the model. Similarly, the projected year for the eradication of seropositive animals is 2001.

Factors for seropositivity to leptospirosis in horses

A serological investigation to determine the prevalence of leptospiral antibodies in horses that were admitted to the Ohio State University (OSU) teaching hospital was conducted on 222 serum samples from 204 horses. Sera were included in this study without prior knowledge of the referral complaint or signs at presentation. In addition, 22 horses residing at two farms where there was clinical evidence of equine leptospirosis had sera collected for testing. All serum samples were tested for the presence of antibodies to Leptospira interrogans serovars L. pomona, L. icterohemorrhagiae, L. canicola, L. hardjo, L. grippotyphosa and L. bratislava, using the microscopic agglutination microtiter test (MAMT). Forty-two of the 204 (20.6%) OSU horses and 16 of 22 (72.7%) horses at the two farms were positive (MAMT titer ≥ 1:100) to one or more of the six serovars tested (P<0.001). The most common serovar antigen reacting with serum antibodies was Leptospira interrogans serovar bratislava, with 33 positives (16.2%) among the 204 OSU horses and 15 positives (68.2%) among the 22 farm horses (P<0.001). There were higher proportions of positive titers among females with increasing age, particularly those in the 8–11 year group (P<0.001). Horses presented with eye conditions were more likely to be positive to leptospirosis, and those with laminitis and colic had a higher prevalence than those presented for other conditions (P<0.05).

Interpretation of an enzyme-linked immunosorbent test using different cut-offs between positive and negative samples for diagnosis of paratuberculosis

The purpose of this study was to compare the serologic responses of cows infected and non-infected with Mycobacterium paratuberculosis in infected and non-infected herds using different cut-offs between positive and negative samples. Infection status of cattle was determined by fecal culture. The serological test was an enzyme-linked immunosorbent assay (ELISA) using an affinity-purified antigen. Cows differed in their level of exposure (high- vs. low-prevalence and negative herds) and disease manifestation (clinical vs. subclinical infection). The ELISA optical density (OD) for cow samples from fecal culture-positive herds (no clinical cases) was higher than that for samples from the fecal culture-negative herd (0.49 vs. 0.26, respectively). The mean OD value (0.61) for clinically-affected cows was not different from that of fecal culture-positive, clinically-normal cows (0.49), nor were differences found between the OD values from fecal culture-negative cows from the herd with no history of paratuberculosis (0.21) and cattle with negative cultures from paratuberculosis-infected herds (0.26). The likelihood-ratio method was used to calculate the optimum ELISA discrimination value between test-positives and -negatives at a given prevalence in a herd, a d a receiver-operator characteristic (ROC) curve was constructed.

Risk factors identified as source of new infections (area spread) with pseudorabies (Aujeszky's disease) virus in 50 swine herds in a contiguous geographical area of Ohio

A retrospective cohort study was done using 50 swine herds in western Ohio for a 15-month period from December 1991 through February 1993. The objective of the study was to determine risk factors for ‘area spread’ of newly infected herds in an area with pseudorabies virus (Aujeszkys disease) (PRV) — especially in relation to factors associated with biosecurity. Herds were operated as either farrow-to-finish, feeder-pig producer or feedlots. The study area was a high-density swine area endemic for PRV since the late 1970s. Twelve of 14 (86%) quarantined herds delivered finishing hogs to the same swine market during the study period. Herds were stratified into two groups with the division between groups at the mean number of shipments of swine delivered to markets per year (mean, 34 per year). The odds of the herds delivering swine to one specific market in the study area were 21 times higher for quarantined than for non-quarantined herds (P < 0.05), four times higher for those herds selling swine ⩾ 34 times to market per year compared with those selling swine to market once per year (P < 0.05), and 14 times higher if grower/finishers were not vaccinated in the quarantined herds compared with being non-vaccinated in the non-quarantined herds. These stepwise logistic regression results support the concept of ‘area spread’ — which is defined as the source of new PRV infections being other than animal contact. Area spread here was associated with which swine market was used and the frequency of swine delivery to markets per year.

Toxoplasma gondii associated behavioural changes in mice, rats and humans: Evidence from current research

This letter to the editor was spurred by a science proram on Danish TV (Viden om, Hosted by Line Friis Moeller n November 16th, 2010), and dealt among others with he current research of investigators who’s research show omplimentary results. Dr. J.A. Webster, Department of Infectious Disease Epiemiology, Imperial College, Faculty of Medicine, London, 2 1PG, UK, who’s specialty in the program was presented s to how Toxoplasma gondii latent infected mice and rats oose their natural fear of cat urine and thereby cats makng it more likely for them to be eaten, and complete the ife cycle of the parasite in the gut of the final host, the cat. Dr. J. Flegr, Faculty of Science, Charles University, rague, Czech Republic, who’s work starting in the early 990s on latent Toxoplasmosis in humans at the time of riting concluded that the infection was dangerous due o its high prevalence (mean 25%), that it is associated ith personality changes, and thereby the infected persons uture destiny. Previously it was thought to be completely harmless, ut the parasite actually changes your personality. If you re infected, you become more daring and unconcentrated, or example it has been noted that people that have the nfection, more often are involved in traffic accidents, and ven is thought be make a person suffer from schizophreia. The program ended with the host of the program conluding “that the results are incredible and scary, and there s much we still do not know” (Line Friis Moeller, Zoologist nd TV Science Journalist). Investigating the topics further in the literature let to proliferating scientific literature also from additional esearch groups among other in the United States. Excellent pdated reviews on the topic already existed in the literaure, many from 2009 and 2010 and prepared by the worlds eading research groups investigating the possible fascinatng association of latent T. gondii infections in rodents as ell as in human beings. This letter is an effort to familiarize readers of the joural with the recent references of the subject of behavioural hanges in mice, rats and humans associated with latent . gondii infection, in which there have been made imporant advances and containing information that has or will

Pseudorabies (Aujeszky's disease) eradication progress and program costs in Ohio, USA

Abstract The purpose of this study was to document how the Ohio pseudorabies (PRV) (Aujeszkys disease) eradication program has progressed to its current status from its initiation in 1977 to the present, as well as to project the year and program costs of eradication of PRV from Ohio, based on a retrospective study of data retrieved from records available on swine herds quarantined in Ohio. All swine herds newly quarantined for PRV from January 1985 to 31 December 1992 ( n = 446) were eligible for the study, 374 (84%) of which had useable data available. Projected year of PRV eradication from Ohio was 1996. Information on detection methods of newly infected herds were only available for 52 of the 374 (14%) data files reviewed from 1985 through 1992, with laboratory diagnosis accounting for 30 of 52 (58%). ‘Area spread’ was identified as the most likely source of PRV infection of newly quarantined herds in 140 of 194 (72%) for which data files were available from the time period 1985 to 1992. Information on herd plans used in the same time interval were available for 285 of the 374 data files (76%). The median number of months under quarantine per herd from 1986 to 1992 were 7.7 months, 6.2 months, 5.9 months, 5.1 months, 17.3 months, 18.9 months and 12.3 months, respectively. Finally the average yearspecific cost per herd-month under quarantine representing 54% of herds released from quarantine for each of the years 1986 through 1992 ranged from