Using a Bayesian belief network to aid differential diagnosis of tropical bovine diseases

The examination of presenting signs has always played an important role in the diagnosis of diseases in animal populations. In the case of diseases of tropical cattle, such expertise is often scarce and confined to those experts with many years of experience. To capture, conserve and disseminate such valuable expert knowledge remains a key challenge to the application of knowledge-based systems in veterinary medicine. In this communication, we explore the use of a Bayesian belief network to quantify expert opinion with a view to estimating the likelihood of various diseases in the presence and absence of certain signs. Information was elicited from a panel of 44 experienced veterinarians to provide the response matrix of 27 signs associated with 20 commonly occurring diseases in sub-Saharan cattle. Using this prior information, estimates of the probability of certain signs occurring with each disease were calculated from which the Bayesian belief network was able to propagate the posterior probability of each of the diseases based on the observed signs. The method as an aid in making diagnosis is discussed. It is recognised that such an approach is but one strand in the process of arriving at a diagnosis. For ease of use and accessibility, the approach has been converted into the software program CaDDiS (Cattle Disease Diagnosis System) which is available for consultation on the World Wide Web.     

New pig disease in Hungary: postweaning multisystemic wasting syndrome caused by circovirus (short communication)

Postweaning multisystemic wasting syndrome (PMWS), a new disease in Hungary, was recognized in a swine herd located in Southeast Hungary, during the early winter of 1999. The first clinical signs of paleness, anaemia, and leanness appeared immediately after weaning, at the age of 40-50 days. Pustules were frequently observed on the skin of the trunk, and signs of necrotic dermatitis were also visible. A syndrome of poor growth and wasting was characteristic of the affected pigs. A porcine circovirus (PCV), the suspected causative agent, was detected by polymerase chain reaction (PCR). Sequencing data and restriction endonuclease (RE) analysis of the PCR products suggested that the virus belonged to the PCV-II group where all the causative agents of PMWS are also grouped.     

Seroepidemiology of Brucella abortus infection in bovids in Sri Lanka

From 1992 to 1995, 0.15% (n=3916) of the bovids (cattle and buffalo) in Sri Lanka were sampled, using a multi-stage sampling procedure. Serum antibodies for Brucella abortus were detected using the indirect enzyme-linked immunosorbent assay (ELISA). The age, the agroecological zone and the management system practiced in the farms of the sampled bovids were studied as risk factors for seropositivity.The overall seroprevalence of brucellosis in cattle was 4.7% (n=3076) and 4.2% in buffaloes (n=840). Bovids that were over 3 years of age, from the dry zone (annual rainfall 20-35 in.), and reared under an extensive management system had higher odds of being seropositive. Bovids from the dry zone were at approximately six times higher odds of being seropositive even after controlling for the possible effects of age and management system. Approximately 75% of the seropositive males were from the dry zone. Most bovids (84%) from the dry zone in this study were reared under an extensive management system (free grazing) which allows unrestricted contact between animals. These factors may have contributed to the spread of brucellosis in bovids in the dry zone.This infection might be an important cause of abortion in bovids in Sri Lanka. However, there is also evidence of other causes for abortion, repeat breeding and retained placenta.     

A comparison of the cytologic and histologic features of meningiomas in four dogs

Abstract: The cytologic and histologic features of 2 intracranial and 2 spinal (extramedullary cervical) canine meningiomas were compared. Cerebrospinal fluid analysis in 2 cases revealed mild, mixed cell pleocytosis, primarily composed of small lymphocytes and monocytoid cells, with a moderate increase in total protein concentration. Cytologic features suggestive of meningioma included cells with both epithelial and mes-enchymal characteristics and a tendency towards cell clustering. Tumor location also was useful in making a diagnosis. The 4 meningiomas differed histologically from one another, and included angioblastic, psam-momatous, meningotheliomatous, and microcystic anaplastic types, which conformed to a classification scheme for human meningiomas. The classification scheme could not be applied to cytologic specimens.     

Formation of a secondary corpus luteum after ultrasound-guided follicular aspiration in cows

This paper reports the observed formation of a secondary corpus luteum (CL) in the presence of the cyclic corpus luteum, on the ovaries of a cow after ultrasound-guided follicular aspiration for oocyte recovery. The secondary structure, although smaller and lighter (4.97 g vs. 6.02 g) than the natural one, had the typical macroscopic appearance of a corpus luteum. Histological examination of the structure using electron microscopy revealed typical structural features of a natural CL. Mean tissue progesterone concentration was significantly lower in the secondary CL (31.15 +/- 3.11 compared with 58.29 +/- 6.32 micrograms/g tissue of the cyclic CL) and oestradiol-17 beta significantly higher than in the natural CL (108 +/- 11.6 compared with 74.2 +/- 7.81 pg/g tissue). P450scc and P450(17 alpha) mRNA was detected in both structures while P450arom and full-length mRNA FSH receptor were detected only in the secondary structure.     

Bioremediation of olive oil mill wastewater: chemical alterations induced by Azotobacter vinelandii

An environmentally friendly bioremediation system of olive oil mill wastewater (OMWW) is studied with respect to its physicochemical characteristics and degradation efficiency on major characteristic constituents. The method exploits the biochemical versatility of the dinitrogen fixing bacterium Azotobacter vinelandii (strain A) to grow in OMWW at the expense of its constituents and to transform it into an organic liquid fertilizer. The system eliminates the phytotoxic principles from OMWW and concomitantly enriches it with an agriculturally beneficial microbial consortium along with useful metabolites of the latter. The end product, branded "biofertilizer", is used as soil conditioner and liquid organic fertilizer. Growth of A. vinelandii in OMWW results in the decline of content of most of the compounds associated with phytotoxicity, and this is confirmed by the assessment of degradation yields. In parallel, during the process several other compounds noncommittally undergo degradation and biotransformation. More specifically, the biofertilization system is capable of achieving removal yields as high as 90 and 96% after 3 and 7 days of treatment, respectively. Statistical analysis of the results showed that between the periods of operation no significant difference occurs with respect to the degradation yield. Moreover, the degradation yield from 3 to 7 days of continuous operation of the system remains almost unaltered during 2 consecutive years.     

Hypertension. Mutation points to salt recycling pathway

A team of researchers at Yale Medical School has uncovered a gene mutation that leads to early-onset hypertension that may point the way to causes for more common forms of high blood pressure. On page 119, the Yale group reports finding a new mutation in the so-called mineralocorticoid receptor, a protein in kidney cells that is involved in the body's handling of salt. This is the first work to demonstrate how alterations in the receptor could give rise to hypertension; in particular, the findings may explain why some women experience a sharp rise in blood pressure during pregnancy.     

Photochemistry. Twist and fluoresce

Catalytic antibodies, or artificial enzymes, act as catalysts by lowering the energy of the transition state of a reaction. In his Perspective, Brauman highlights the study by Simeonov et al., who have applied similar principles to photochemical processes and shown that intense fluorescence can be achieved. The approach provides a way of measuring internal molecular motion within the antibody on a very fast time scale. Fluorescent antibodies may find applications in immunochemistry, histological assays, and genomic studies.