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PubMed2006

Genomic structure, promoter analysis and expression of the porcine (Sus scrofa) TLR4 gene.

Toll-like receptor 4 (TLR4) is essential for initiating the innate response to lipopolysaccharide (LPS) from Gram-negative bacteria by acting as a signal-transducing receptor. As the pig industry faces a unique array of related pathogens, it is anticipated that the genotype of swine TLR4 could be of crucial importance in future strategies aimed at improving genetic resistance to infectious diseases. In order to help in investigating TLR4 as a candidate disease-resistance gene in pigs, we established its genomic structure and produced sufficient flanking intronic sequences to enable simple PCR amplification of the coding portions of the gene. Expression in different porcine tissues was studied and showed splicing variations in mRNA sequences. The cDNA sequence for poTLR4 contains an open reading frame of 2526bp that codes for 841 aa, 98 and 568bp in the 5'- and 3'-UTRs, respectively. Overall, the general organization of porcine, human, murine, and avian TLR4 genes is quite similar: three exons with the third one very long. A high level of conservation of the size and the sequence, especially for the two last exons and particularly in the sequence corresponding to the LRRs and TIR domain, is observed between species. The important antimicrobial properties of these proteins may account for a conservative selection pressure on these TLR4 coding sequences. Several putative binding sites described in the human and murine promoter of TLR4 genes have been identified in the 5'-flanking region of poTLR4. Conversely, this region lacks a TATA box, consensus initiator sequences, or GC-rich regions. The basic sequence data gathered will allow the establishment of an inventory of naturally occurring variation in porcine TLR4, so that alleles can be tested for disease association studies.

Animals↗
PubMed2000

The effects of bovine viral diarrhoea virus on cattle reproduction in relation to disease control.

Bovine viral diarrhoea virus (BVDV) is a major reproductive pathogen in cattle. Infection of the bull can lead to a fall in semen quality and the isolation of infectious virus in the ejaculate, while infection in the cow leads to poor conception rates, abortions and congenital defects. BVDV also reduces the animal's resistance to other respiratory and enteric pathogens. The prevalence of BVDV is primarily due to the efficiency with which the virus crosses the placenta of susceptible females. Calves that survive infection during the first trimester of pregnancy are born with a persistent and lifelong infection. These persistently infected (PI) animals represent between 1.0% and 2.0% of the cattle population and continuously shed infectious virus. The availability of reliable diagnostic ELISA and PCR techniques, which can test milk or serum samples for virus or antibodies, has simplified BVDV surveillance and improved the prospects for control. Although PI animals are the principal vectors within and between herds, they can be readily identified and removed. By contrast, cows carrying a PI foetus are particularly problematic. These animals have been compared to 'Trojan Horses' because they are virus-negative and antibody-positive but they deliver PI calves. In general, acutely infected cattle are much less efficient vectors but infections at the onset of puberty have resulted in a localised and persistent infection within the testes. Under these circumstances, virus shedding into the semen may remain undetected. Transmission of BVDV can be controlled through vaccination or eradication. BVDV vaccine technology has been developing over the past 30 years, but currently available vaccines are still of the conventional inactivated or attenuated sort. In general, vaccination has not been applied with sufficient rigor to make a significant impact on the level of circulating virus, unlike the national and regional eradication programmes established in areas such as Scandinavia, Austria, the Netherlands and Scotland. Eradication confers the added advantage of improved herd health; however, it also creates a susceptible cattle population that needs to be protected by stringent biosecurity. In this article, we discuss how BVDV influences reproductive function, the potential for viral transmission during breeding and the measures that must be taken to avoid the spread of infection to susceptible cattle populations via semen, embryos, culture fluids and infected cows.

Abortion, Veterinary↗
PubMedDate not supplied

[Bovine diarrhea virus: an update].

Bovine Viral Diarrhea Virus (BVDV) is a pathogen of cattle, member of the family Flaviviridae, genus pestivirus, which also includes Classical Swine Fever Virus (CSFV, or hog cholera virus), and Border Disease Virus of sheep (BDV). It causes important economical losses associated mainly with reproductive failure. Pestiviruses are small enveloped viruses, with a diameter of about 40 nm. The nucleocapsid is probably icosahedral . The genome consists of a single stranded positive RNA, encoding approximately 430 kD of proteic product. Genetic expression consists of the synthesis of a polyprotein which is co- and post-translationally processed. According to its behavior "in vitro" two biotypes can be distinguished: non cytopathic (ncp) and cytopathic (cp), most probably derived from the ncp through mutations and/or recombination. BVDV is able to cross the placenta and infect the fetus, causing a variety of problems, from fetal death to the birth of a persistently infected (P) calf, according to the fetal age at the time of infection. PI animals are immunotolerant to the virus and shed it in all secretions. Only the ncp biotype has been isolated from PI animals. The superinfection of a PI animal with a cp strain causes mucosal disease, always fatal. Outbreaks of a severe, sometimes hemorrhagic disease, caused by ncp BVDV, have occurred in Canada and USA since 1993. Genomic and serological differences between the "traditional" strains and the viruses isolated from these outbreaks led to the division of BVDV in subtypes I and II, both including cp and ncp strains. Analyses of the non coding 5'-UTR zone of the genome of pestiviruses from different species (bovine, ovine, porcine) suggest that there are at least 3 genotypes within the genus. A new classification of these viruses, based on genomic sequence instead of species of origin, has been proposed. Genomic heterogeneity exists in the BVDV genome, which presents 3 hypervariable zones, 2 of them in the major neutralizing protein. In Argentina prevalence of BVDV antibodies in cattle population is 70%, and the prevalence of persistent infections is around 1%.

Abortion, Veterinary↗
PubMed2005

[Scientific standards in parasitology in historical perspective].

An analysis of scientific standards in parasitology was carried out from the perspective of anthropology of knowledge - a new discipline that emerged from non-classical history science in the 1990s. The history of parasitology, its development and limitations, are presented in a broad socio-cultural context, as the answers of scientists to different social needs in historical periods. In parasitological history there are some periods characteristic for all newly emerging disciplines of natural science. The first systematic account of natural phenomena and their interpretations was initiated in the 16th century and continued till the mid 18th century. It was a period when the phenomena could not be explained in a proper way by the existing and accepted theories. The epidemic diseases were one of these phenomena which were interpreted based on ancient ideas, mostly humoral pathology. In the 16th century a new contagium concept of material factors (pathogenes) that could be spread by contact among humans or close association was formed. This hypothesis, however, was not widely accepted because it contradicted the well-established normative concepts in the European academic naturalism. The development of parasitology was stopped because of theoretical barriers and interpretation difficulties (non-materialistic standard of naturalism, humoral pathology and spontaneous theory). In the second half of the 18th century, the theoretical crisis in natural sciences gave a new impulse for many disciplines; among others, parasitology entered in its second stage of development. The collected observations were classified in a new way and in the context of new interpretations. The progress in parasitology was prompted by the intensified urbanization, rapid increase of European population as well as by wars connected with infections and epidemics. It resulted in two competitive research programs (the French and the German). On the basis of the same observations, they advanced different theoretical interpretations. The third period in the history of parasitology lasted from the mid 19th century to the end of World War I. At that time a common agreement was established in all Europe, with regard to interpretation of standards inspired by positivism, i.e. verification of empirical statements through observation. Parasitology emerged as a separate discipline. Theoretical barriers limiting its progress and setting the questions were overcome. The contagion concept was reinstated. The colonial conquests solving demography problem provided the most important social impulse for the progress in parasitology. It was supported by governments interested in having their colonies free from diseases, mainly malaria and other tropical diseases, and thus safe for the European pioneer settlers. There was also development of parasitological scientific institutions (institutes of tropical medicine) and didactics. After World War I parasitology entered the fruitful stage of discipline development which resulted in a division into subdisciplines and a progress of new scientific fields. Its theoretical standards have become fixed and provided a basis for preventive programmes against parasite diseases, supported financially by European goverments, USA and some other countries. Those programmes were executed both in the home countries and in the colonies. After World War II, in the fourth stage of parasitology development, attention was mainly paid to local natural environment in order to diagnose parasites and their vectors. At the same time, parasitology became an applied science practiced in many specialized centres not only at universities. Presently, the main aims of parasitology are studies on biodiversity of parasites and environmental protection in the developed countries, and within tropical medicine as the travel medicine, because of rapid increase of tourism.

Animals↗