Confirmation of rinderpest in experimentally and naturally infected cattle using microtitre techniques

Summary Virulent rinderpest virus was detected by immunoperoxidase staining of microtitre bovine kidney cell cultures within 24 to 48 hours of inoculation with prescapular lymph node and spleen homogenates from experimentally infected steers. Rinderpest virus specific cytopathic effects were evident from 48 hours in microtitre plates and from 72 hours in rolled tube cultures. Nasal and ocular secretions collected from cattle naturally infected with rinderpest and inoculated into bovine kidney cell cultures did not readily yield cytopathic virus in both tubes and microtitre plates, but immunoperoxidase staining of microtitre cultures on the fourth day of inoculation detected replication of virus in cultures inoculated with ocular and nasal secretions from seven of 17 cattle tested.

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Resumen Se detectó el virus virulente de mediante la tinción con inmunoperoxidasa de cultivos de células de ri?ón bovino en bandejas de microtitulación, después de la inoculación de estos con suspensiones homogenizadas de ganglios linfáticos preescapulares y de bazo provenientes de novillos infectados experimentalmente. El efecto citopático del virus de la peste bovina fue evidente desde las 48 horas en bandejas de microtitulación y desde las 72 horas en tubos de cultivo giratorios. Secreciones oculares y nasales colectadas de ganado infectado en forma natural con la peste bovina e inoculadas en cultivos de células de ri?ón bovino, no mostraron efecto citopático fácilmente en tubos giratorios o bandejas de microtitulación, pero la tinción de las bandejas con inmunoperoxidasa reveló replicación del virus a partir del cuarto día de inoculación con secreciones oculares y nasales en siete de los 17 animales examinados.

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Résumé Un virus bovipestique virulent a été décelé par le test de coloration à l'immunoperoxydase de cellules rénales bovines en culture dans des plaques de microtitrage et infectées 48 heures plus t?t avec des homogénats de ganglions lymphatiques et de rate provenant de bouvillons infectés expérimentalement. Les effets cytopathogènes du virus étaient évidents au bout de 48 h dans les plaques de microtitrage et 72 h dans les tubes en rollers. Les sécrétions nasales et oculaires prélevées sur du bétail infecté naturellement par la peste bovine et inoculées sur des cellules rénales bovines n'ont pas toujours montré d'effet cythopathogène aussi bien dans les tubes que dans les plaques de microtitrage. Cependant, la coloration à la peroxydase au jour 4 après l'inoculation a permis de déceler la présence de virus dans 7 cas sur 17.

     

The Control of Rinderpest in Tanzania between 1997 and 1998

In January 1997, Tanzania requested international assistance against rinderpest on the grounds that the virus had probably entered the country from southern Kenya. Over the next few months, a variety of attempts were made to determine the extent of the incursion by searching for serological and clinical evidence of the whereabouts of the virus. At the clinical level, these attempts were hampered by the low virulence of the strain, and at the serological level by the lack of a baseline against which contemporary interpretations could be made. Once it became apparent that neither surveillance tool was likely to produce a rapid result, an infected area was declared on common-sense grounds and emergency vaccination was initiated. The vaccination programme had two objectives, firstly to prevent any further entry across the international border, and secondly to contain and if possible eliminate rinderpest from those districts into which it had already entered. On the few occasions that clinical rinderpest was subsequently found, it was always within this provisional infected area. Emergency vaccination campaigns within the infected area ran from January to the end of March 1997 but were halted by the onset of the long rains. At this time, seromonitoring in two districts showed that viral persistence was still theoretically possible and therefore a second round of emergency vaccination was immediately organized. Further seromonitoring then indicated a large number of villages with population antibody prevalences of over 85%. These populations were considered to have been `immunosterilized'. Although no clinical disease had been observed in them, it was decided to undertake additional vaccination in a group of districts to the south of the infected area. Serosurveillance indicated that rinderpest could have been present in a number of these districts prior to vaccination. Serosurveillance in 1998 suggested that numerous vaccinated animals had probably moved into districts outside the infected and additional vaccination areas, but did not rule out the continued presence of field infection.     

The pathology of spontaneous paratuberculosis in the North American bison (Bison bison)

Gross and histopathologic examinations were performed on 70 North American bison (Bison bison) from a Mycobacterium avium paratuberculosis culture-positive herd. The bison examined were part of a breeding herd totaling 2,800 animals. Eight of 70 (11%) animals had gross findings of intestinal mucosal thickening, and 16 of 70 (23%) of the animals had enlarged mesenteric lymph nodes. Histologic lesions compatible with Johne's disease were diagnosed in 30 of 70 (43%) bison on the basis of the demonstration of noncaseating granulomatous inflammatory infiltrates and of one or more acid-fast bacilli characteristic of Mycobacterium avium paratuberculosis. A suspicious diagnosis of Johne's disease was obtained in 11 of 70 (16%) bison on the basis of the observation of noncaseating granulomatous inflammatory infiltrates without demonstrable acid-fast bacteria. Twenty-nine of 70 (41%) animals were assessed as histologically paratuberculosis free. Histologic results were compared to Johne's disease tests such as culture, serology, and polymerase chain reaction, which were performed on some of the cohort animals.     

Microneutralisation systems for use with different strains of peste des petits ruminants virus and rinderpest virus

Summary Comparative studies were made to determine the most suitable microtitration system for assaying strains of peste des petits ruminants virus (PPRV) and rinderpest virus (RV). Infectivity titres did not differ significantly when assayed in either calf kidney, sheep kidney or Vero cells. However, cytopathic effects were much easier to detect in the latter making them the cell of choice. Addition of small amounts of virus to preformed cell monolayers in microplates with the subsequent addition of maintenance medium give higher infectivity titres than when cell suspension was added to virus, although the latter is more convenient for routine use. The titres of PPRV and neutralising antibodies assayed in tubes and microplates were not significantly different. Simultaneous screening of sera at a 1 in 20 dilution against both PPRV and RV gave a higher incidence of positives against homologous as opposed to heterologous virus.

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Resumen Se hicieron estudios comparativos para determinar el mejor sistema de microtitulación para detectar cepas del virus de la peste de peque?os rumiantes (VPPR) y virus de rinderpest (VR). Los títulos infectivos, no difirieron significativamente cuando los ensayos se efectuaron en cultivos celulares de ri?ón de ternero, de oveja y células Vero. Sin embargo, los efectos citopáticos se detectaron más facilmente en este último, haciendo de este cultivo celular el preferencial para pruebas de microtitulación. La adición, de peque?as poblaciones virables a monocultivos celulares preformados en microplacas, conjuntamente con medio de mantenimiento, dió títulos infectivos más altos, que cuando la suspensión de células se a?adió al virus, aunque este último método es más conveniente para trabajos de rutina. Los títulos del VPPR, y los anticuerpos neutralizantes, pruebas determinadas en tubo y microplacas, no difirieron significativamente. El análisis simultáneo de suero en diluciones 1 en 20 contra los virus de Pest de Peque?os Rumiantes y Rinderpest, dió una incidencia más alta de positivos contra el suero homólogo, que contra el heterólogo.

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Résumé Des études comparatives ont été effectuées pour déterminer la microméthode la mieux adaptée au titrage des souches des virus de la peste des petits ruminants (VPPR) et de la peste bovine (VPB) Les titres d'infectivité n'étaient pas significantivement différents qu'ils soient dosés sur cellules de rein de veau, de rein de mouton ou sur cellules Vero. Cependant, les effects cytopathogènes étaient plus facile à déceler dans les cellules Vero, ce qui en fait les cellules de choix. L'addition de petites quantités de virus aux tapis cellulaires complets en microplaques puis adjonction ultérieure de milieu d'entretien s'est traduit par des titres d'infectivité plus élevés que lorsque le virus était inoculé aux cellules en suspension, bien que cette dernière méthode soit plus commode pour l'utilisation de routine. Les titres du virus de la PPR et des anticorps neutralisants ne se sont pas révélés significativement différents en tubes ou en microplaques. Les examens simultanés de sérums au 1/20 contre à la fois le virus de la PPR et de la PB se tradusient par une fréquence plus élevée de réactions positives aux virus homologues qu'aux virus hétérologues.

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Research project R3792.     

Economic land evaluation: why and how

Abstract. Economic land evaluation is a method for predicting the micro-economic value of implementing a given land-use system on a given land area. This is a more useful prediction of land performance than a purely physical evaluation, since many land-use decisions are made on the basis of economic value. Measures of economic suitability include the gross margin, net present value, internal rate of return, benefit:cost ratio, and utility functions based on these. The economic value of the in-situ resource quality of a land area may be inferred directly from land characteristics or from Land Qualities which, when less than optimum, result in decreased yields or increased costs. The economic value of geographic land characteristics may be determined by spatial analysis. Single or multi-criteria economic optimization and risk analysis can extend the economic land evaluation from a natural resource or management unit to a production or planning unit. Computerized tools may be used to assist in economic land evaluation.     

A mathematical model of the United States beef production system

Dynamic linear programming was used to model the US beef production system, to determine the cattle cycle effects on feeder cattle supplies and to select feeding options that would maximise USDA choice and prime quality grade beef production. The model represented the US as a five-region beef production system with inter-regional transportation of offspring for feeding purposes. Cow weights, offspring weaning weights and feed efficiency were different for each region, but the feeding activities were the same in each region except for region two. In region two the feeding of grain to steer and heifer offspring was not an industry practice. Dynamic properties of the model were achieved through constraints that transferred animals from year zero (initial condition) to year five using calving, cow culling, replacement heifer and death loss rates as controlling parameters. The results of model exercises that used historical parameter values indicate that there will be a significant decrease in the supply of beef at all grade levels over the next five years. They also suggest that it is more economically efficient to feed calves from the southeastern and northern parts of the USA if they are transported to the southwestern region.     

The development of antibodies in rabbits and cattle infected experimentally with an african strain of malignant catarrhal fever virus

An indirect immunofluorescence (IIF) test for antibody to wildebeest-derived strains of malignant catarrhal fever virus (MCFV) was developed using infected bovine embryonic kidney cells as antigen. This IIF technique and a microtitre method for the assay of virus-neutralizing (VN) antibody were then applied to sequential serum samples from rabbits and calves infected experimentally with a virulent strain of MCFV, which caused lethal disease.Antibody of the IIF type appeared in both species about 6–7 days prior to the onset of pyrexia and increased continuously until death. Neutralizing antibody was detected shortly before the end of the incubation period in the majority of rabbits but was not produced in calves which were killed up to 3 days after reaction. The presence of either antibody did not affect the fatal outcome in rabbits.     

Antigens and antibodies of malignant catarrhal fever herpesvirus detected by immunodiffusion and counter-immunoelectrophoresis

Using hyperimmune rabbit and cattle sera, immunodiffusion (ID) and counter-immunoelectrophoresis (CIEP) tests detected three or four and two or three malignant catarrhal fever (MCF) virus antigens, respectively, in infected cells. The ID test detected precipitating antibodies to MCF virus in $\text{3}\text{9}$ experimentally infected rabbits, $\text{0}\text{14}$ experimentally infected cattle, $\text{1}\text{13}$ naturally infected cattle, $\text{62}\text{176}$ wildebeest and $\text{3}\text{20}$ hartebeest. The CIEP test detected specific antibodies in $\text{3}\text{9}$ rabbit sera, but non-specific reactions prevented its use with bovine sera.The CIEP test was 2 to 4 times more sensitive than ID for detecting antibodies to MCF virus, but both tests were less sensitive than indirect immunofluorescence.The ID test demonstrated an antigenic relationship between wildebeest and hartebeest strains of MCF virus. Neither ID nor CIEP detected MCFV antigens in tissues infected with MCF virus.     

Prediction of soil depth using environmental variables in an anthropogenic landscape, a case study in the Western Ghats of Kerala, India

Soil (regolith) depth is a crucial input for modeling earth surface phenomena. However, most studies ignore its spatial variability. Techniques that map the spatial variability of soil depth are of three types: (1) physically-based; (2) empirico-statistical from environmental correlates; and (3) interpolation from point observations. In an anthropogenic landscape, soil depth does not depend primarily on natural processes, making it difficult to apply a physically-based approach. The present study compares empirico-statistical methods with geostatistical methods for predicting soil depth in such a landscape: Aruvikkal catchment (9.5 km²) in the Western Ghats of Kerala, India. Regression kriging applied on blocks of 20 m by 20 m using the environmental covariates elevation, slope, aspect, curvature, wetness index, land use and distance from streams, proved to be the best predictor of soil depth. This model explains 52% of the variability of soil depth in the catchment; with a prediction variance of 0.05 to 0.19. A Gaussian simulation was attempted for a more realistic visualization of the depth, as opposed to the smooth kriging prediction. The most important explanatory variable of soil depth in this landscape is land use, as expected from the strong human intervention.