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F van Knapen

Publications and source records attributed to F van Knapen.

At least 37 records · Page 2Linked to original sources

Cows, cats, and FSE: death penalty justified?

Transmissible spongiform encephalopathies affect a number of mammalian species. The most common spongiform encephalopathies are scrapie in sheep and Bovine Spongiform Encephalopathy (BSE) in cattle. Feline Spongiform Encephalopathy (FSE) is a related disorder in domestic cats. Because of the link between BSE and FSE, cats are put on a par with cattle, in terms of politics and regulations. In the Netherlands, when a case of BSE is found on a farm, not only the ruminants, but also the cats are taken away for post-mortem examination. So far, the cats examined have always been negative for FSE. There are no scientific reasons for destroying the cats on farms where BSE has been found.

Animals↗

Inhibition of a glucose-limited sequencing fed-batch culture of Salmonella enterica serovar enteritidis by volatile fatty acids representative of the ceca of broiler chickens.

The effects of concentrations of volatile fatty acids on an anaerobic, glucose-limited, and pH-controlled growing culture of Salmonella enterica serovar Enteritidis were studied. Suddenly increasing volatile fatty acids to the concentrations representative of the ceca of 15-day-old broiler chickens caused washout of serovar Enteritidis. In contrast, a sudden increase to the volatile fatty acid concentrations representative of the ceca of younger broiler chickens caused a reduction in the biomass but not washout. Gradually increasing volatile fatty acids caused a gradual decrease in the biomass of serovar Enteritidis. We conclude that the concentrations of volatile fatty acids present in the ceca of broilers with a mature microflora can cause washout of serovar Enteritidis in an in vitro system mimicking cecal ecophysiology.

Anaerobiosis↗

Effect of fermented feed on the microbial population of the gastrointestinal tracts of pigs.

An in vivo experiment was performed with pigs to study the inhibitory effect of fermented feed on the bacterial population of the gastrointestinal tract. Results demonstrated a significant positive correlation between pH and lactobacilli in the stomach contents of pigs in dry feed as well as in the stomach contents of pigs fed fermented feed. Furthermore, a significant positive correlation between the pH and the numbers of bacteria in the family Enterobacteriaceae in the contents of the stomach of pigs fed dry feed was found. In the stomach contents of pigs fed fermented feed, a significant negative correlation was found between the concentration of the undissociated form of lactic acid and the numbers of Enterobacteriaceae. The numbers of Enterobacteriaceae in the contents of the stomach, ileum, cecum, colon, and rectum of pigs fed fermented feed were significantly lower compared with the contents of the stomach, ileum, caecum, colon, and rectum of pigs fed dry feed. The numbers of total lactobacilli were significantly higher in the stomach contents of pigs fed fermented feed and in the ileum contents of one pig group fed fermented feed compared with the contents of pigs fed dry feed. However, the influence of lactobacilli on numbers of Enterobacteriaceae could not be demonstrated. It was concluded that fermented feed influences the bacterial ecology of the gastrointestinal tract and reduces the levels of Enterobacteriaceae in the different parts of the gastrointestinal tract.

Animal Feed↗

Control of trichinellosis by inspection and farm management practices.

The prevention of human trichinellosis by proper meat inspection is a classic example of successful veterinary public health measures. The microscopic methods which have been used for more than a century to test pigs for trichinae were intended to prevent human disease. However, the value of these relatively insensitive direct detection methods, including trichinoscopy and pooled sample digestion, was debated as soon as more sensitive indirect (serological) methods became available. Two issues related to testing were discussed. First, should public health authorities endeavour to prevent all infections of humans rather than simply prevent the occurrence of disease, and second, would epidemiological surveillance and monitoring of the pig population on farms not provide a better control system to prevent human infection. This latter issue is of particular importance for those countries in the world where human trichinellosis acquired from farmed animals is absent and examination of pigs at the abattoir only results in negative findings. In countries where domestic pig infections are virtually non-existent, monitoring of Trichinella infection in wildlife could also contribute to understanding the infection pressure from nature to livestock. Trichinella-free pig farming is a feasible option for controlling this zoonosis, even in endemic areas. This approach provides an opportunity to combine good veterinary practice, in order to prevent animal diseases, with the prevention of Trichinella infection. All animals with access to the environment, or animals which are fed with potentially Trichinella-infected feed (swill, carcasses) will always constitute a public health threat, and must be inspected individually at slaughter (swine, horses, wild boars). Finally, it is important to recognize that trichinellosis is a world-wide problem that needs continuous public health attention. If no control system exists, for whatever reason, the public should be educated not to consume improperly cooked meat.

Animal Husbandry↗

International Commission on Trichinellosis: recommendations on methods for the control of Trichinella in domestic and wild animals intended for human consumption.

This document provides a uniform set of recommendations for the control of Trichinella at all levels (on the farm, at slaughter and in processed meats). These recommendations are based on the best scientific information available and represent the official position of the International Commission on Trichinellosis regarding acceptable control methods. These recommendations are subject to change as new scientific information becomes available.

Abattoirs↗

Role of volatile fatty acids in development of the cecal microflora in broiler chickens during growth.

It is known that volatile fatty acids can inhibit growth of species of the family Enterobacteriaceae in vitro. However, whether these volatile fatty acids affect bacterial populations in the ceca of chickens is unknown. Therefore, a study was conducted to investigate if changes in volatile fatty acids in ceca of broiler chickens during growth affect bacterial populations. Results showed that members of the Enterobacteriaceae and enterococci are present in large numbers in 3-day-old broilers and start to decrease when broilers grow older. Lactobacilli are present in large numbers as well in 3-day-old broilers, but they remain stable during the growth of broilers. Acetate, butyrate, and propionate increase from undetectable levels in 1-day-old broilers to high concentrations in 15-day-old broilers, after which they stabilize. Significant negative correlations could be calculated between numbers of Enterobacteriaceae and concentrations of undissociated acetate, propionate, and butyrate. Furthermore, pure cultures of Enterobacteriaceae isolated from the ceca were grown in the presence of volatile fatty acids. Growth rates and maximal optical density decreased when these strains grew in the presence of increasing volatile fatty acid concentrations. It is concluded that volatile fatty acids are responsible for the reduction in numbers of Enterobacteriaceae in the ceca of broiler chickens during growth.

Animals↗

[Foot-and-mouth disease of cattle is not a zoonosis].

In 1997 there was an outbreak of foot-and-mouth disease (FMD) among cattle in Turkey. People visiting that country were warned against importing animal products into the Netherlands. This had nothing to do with hazards to human health, as FMD virus is not a zoonotic virus, but with the risk of spread of the disease to livestock in the Netherlands, notably to cattle and pigs. A disease with similar clinical symptoms in pigs is swine vesicular disease (SVD), which is not a zoonosis either. FMD virus is an aphtovirus, SVD virus is an enterovirus. Hand-foot-and-mouth disease in humans is caused by other enteroviruses, i.e. Coxsackie virus and enterovirus 71.

Animals↗

An outline of a risk assessment-based system of meat safety assurance and its future prospects.

Discussed are the outlines of a risk assessment-based system of meat safety assurance to replace the current meat inspection. An example of a system that uses the Hazard Analysis of Critical Control Points (HACCP)-principles in the entire production chain from stable to table is also given. Continuous evaluation of risks is the main driving force of the new system. Only then the system has the means to remain flexible and provide for the data necessary to convince trade partners that the products they buy are safe. A monitoring system that keeps track of the important health hazards in the entire chain from stable to table is therefore necessary. This includes monitoring of cases of disease in the human population caused by the hazardous agents of concern. Coordination of the monitoring and control and processing of the information is done by an independent body. Furthermore, the system demands a production from stable to table that is based on the ideas of Integrated Quality Control (IQC), HACCP, and certification of production processes and quality control procedures. Clear legislation provides for criteria about acceptable or unacceptable health risks for the consumer and determines at what moments which risks should be controlled by the producers. Simultaneously, the legislation has to be flexible enough to be able to adapt quickly to any changes in risks, or in the way risks should be controlled. In the new system current meat inspection can easily be carried out by employees of the slaughter houses and is no longer a direct responsibility of the authorities. The authorities only demand certain safety levels and verify whether producers stick to these. Producers remain fully responsible for the safety and quality of their products, and fully liable in case of any damage to the consumers' health. However, it is to be expected that some EU Member-States miss the organizational and agricultural basis for a successful application of the new system. Consequences are that two parallel flows of meat and meat products may come to existence. One flow will exist of meat produced according to the new, and with respect to safety assurance, superior system. The other flow will consist of meat produced and inspected in the traditional way. However, this meat will contain all the flaws that required a revision of the system in the first place. This, and the fact that EU policy ordains that part-taking in an alternative meat inspection system should be voluntary, may very well result in a very slow start-up of the new system. One of the easiest solutions, however, would be to implement a decontamination step in the slaughtering process, provided that this is accompanied by strict codes of hygienic practices and good manufacturing practices. Not only would this lead to safer meat, but also result in the two separate flows of meat becoming one flow again as well as an easier to organize livestock production according to HACCP-principles.

Abattoirs↗

[Toxoplasmosis in goats in the Netherlands: a pilot study].

A pilot-study was carried out on ten Dutch goat farms to see whether there is a relationship between farm management factors and the occurrence of toxoplasmosis. Questionnaires were used to collect information about farm management factors and blood samples were taken to determine the prevalence of toxoplasmosis on these farms. The mean prevalence was 47% (range 5-90%). The presence of kittens on a farm was a risk factor for a higher prevalence of toxoplasmosis.

Animal Husbandry↗

Characterization of Giardia duodenalis by polymerase-chain-reaction fingerprinting.

The development of a polymerase chain reaction (PCR) based fingerprinting method for the characterization of Giardia duodenalis isolates is described. The method uses three different PCRs; one is specific for the A ("Polish") major group of G. duodenalis isolates, another is specific for the B ("Belgian") group of isolates; and one amplifies a fragment of the glutamate dehydrogenase gene present in all G. duodenalis isolates. The PCRs perform highly sensitively on DNA from cultured trophozoites. Isolates were further characterized by restriction-fragment-length polymorphism (RFLP) analysis of the PCR products. In this way, representative isolates from the A and B groups could be grouped together into a number of subgroups. The stability of the genotypes with time and the reproducibility of the two methods were tested on cloned and subcloned lines from a number of isolates and proved to be highly satisfactory. The PCR/RFLP method was evaluated on cysts derived from a number of human patients. It is concluded that the PCR fingerprinting method described in this paper provides a reliable characterization method for Giardia isolates and has the potential to be used as a direct method of typing G. duodenalis cysts from feces.

Adolescent↗

Production of monoclonal antibodies specific for the i and 1,2 flagellar antigens of Salmonella typhimurium and characterization of their respective epitopes.

Salmonella typhimurium expresses two antigenically distinct flagellins, each containing a different H antigen (i and 1,2), the combination of which is highly specific for this serotype. In this study, overlapping recombinant flagellin fragments were constructed from the fliC (H:i) and fljB (H:1,2) flagellin genes, and the expression products were tested for binding to H antigen-specific monoclonal and polyclonal antibodies. A minimal area, 86 amino acids for H:i and 102 amino acids for H:1,2, located in the central variable domain of each flagellin was required for the binding of serotype-specific antibodies, providing further evidence for the presence of a discontinuous H epitope. Two peptides comprising these areas were shown to be highly suitable for application as antigens in an enzyme-linked immunosorbent assay detecting S. typhimurium-specific antibody.

Antibodies↗

Comparison of the internal transcribed spacer, ITS 1, from Toxoplasma gondii isolates and Neospora caninum.

The internal transcribed spacer (ITS1) region and the 5' part of the 5.8S ribosomal RNA gene of the ribosomal DNA repeat from 20 Toxoplasma gondil isolates was sequenced and found to be identical in all isolates, independent of host origin or virulence to mice. The ITS1 region from the closely related coccidian parasite Neospora caninum differed in 22% of its nucleotides. Hence, the ITS1 region provides a good marker for the distinction of T. gondii and N. caninum but is not useful for epidemiology studies of T. gondii.

Animals↗

Bovine fetal neosporosis: a comparison of epizootic and sporadic abortion cases and different age classes with regard to lesion severity and immunohistochemical identification of organisms in brain, heart, and liver.

Eighty bovine fetuses with confirmed neosporosis were used to score lesion severity and presence of parasites in brain, heart, and liver. A comparison was made between epizootic and sporadic abortion cases. The possible influence of fetal age was also investigated. Histologic lesions of multifocal encephalitis, myocarditis, and periportal hepatitis with or without focal hepatocellular necrosis were almost always observed. Neospora caninum tachyzoites were identified immunohistochemically in 85% of the brains, 14% of the hearts, and 26% of the livers. Tissue cysts were observed in 21% of the brains. Significant differences between epizootic and sporadic abortion cases were found only in the liver. Hepatic lesions were more prominent and N. caninum tachyzoites were observed more frequently and in higher numbers in epizootic cases. Examination by immunohistochemistry of the liver in addition to the brain can be highly contributive diagnostically, particularly in epizootic cases. There were no significant age-related differences except for a higher presence of tachyzoites in the hearts of younger fetuses (3-4 months gestational age).

Abortion, Veterinary↗