[Covered shortage: Can there be a lack of veterinarians at the human health services?].
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Animals↗
Biomedical subjects
F van Knapen
Publications and source records attributed to F van Knapen.
[Negligible risk of visceral or ocular larva migrans from petting a dog].
In a recent publication it was suggested that human toxocarosis, including ocular larva migrans, may result from petting dogs infected with Toxocara canis, the dog roundworm. Recalculating the eggs per gram in the dog's coat revealed that in 7 of the 15 positive dogs only one Toxocara egg per dog was found. Only 4% of all eggs were embryonated and hence infectious. It is, however, very plausible that this is contamination originating from the environment. The authors found also many other parasite eggs and free-living larvae in their samples, which points to the dog being merely a passive transport host. The risk to man of acquiring the infection by stroking a dog is therefore considered to be extremely limited.
Animals↗
['Petting dogs can cause blindness': a critical analysis].
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Animals↗
Effect of acidified feed on susceptibility of broiler chickens to intestinal infection by Campylobacter and Salmonella.
Consumption of poultry meat is associated with human Campylobacter and Salmonella infections. One way to control the presence of these bacteria in broiler flocks is to make chickens less susceptible for colonisation. Acidification of feed may be a tool to reduce the Campylobacter and Salmonella carriage in broiler chickens. In the present experiments an acidified feed with high levels of organic acid, 5.7% lactic acid and 0.7% acetic acid, was applied. In an in vitro experiment the reduction or growth of Campylobacter and Salmonella was measured after addition of 10(7)cfu of these bacteria into a conventional broiler feed, acidified feed and fermented feed, whereas the numbers of Salmonella increased in non-acidified feed. The number of Campylobacter decreased 2-3 (10)log cfu. In the acidified and fermented feed a complete reduction of Campylobacter was observed within 20 min, and a total Salmonella reduction started after 1h, and was complete after 2h. Subsequently, an in vivo experiment with 100 individually housed broiler chickens showed that chickens fed acidified feed were less susceptible to an infection with Campylobacter than were chickens fed conventional feed. The size of reduction was however limited. The susceptibility for Salmonella colonisation was not affected by acidified feed. It is concluded that the role for acidified feed in the control of Campylobacter and Salmonella is limited.
Animal Feed↗
Antagonistic activities of several bacteria on in vitro growth of 10 strains of Campylobacter jejuni/coli.
Chicken meat contaminated with Campylobacter jejuni can be the source of human enteritis. To decrease the risk of human infection, Campylobacter should be controlled at farm levels. Orally given probiotic bacteria could prevent colonisation of chicken with pathogenic bacteria like Campylobacter. The aim of this study was to investigate the effect of different bacteria on Campylobacter growth. Our results demonstrated that bacteria isolated from conventional chicken had potential inhibitory activities against Campylobacter. Other bacteria not isolated from chickens but with known antagonistic capacities, e.g. Enterococcus (56 strains) and Escherichia coli (20 strains), did not show any negative effect on Campylobacter. Interestingly, one Lactobacillus (P93) strain isolated from the chicken gut showed bactericidal activity against all tested Campylobacter. The bactericidal effect was characterised as the production of organic acids in combination with probably production of an anti-Campylobacter protein. In a co-culture study of Campylobacter and Lactobacillus (P93), the culturability of Campylobacter was under the detection limit after 48 h of incubation. A chicken experiment is needed to further evaluate the effect of the promising probiotic bacteria against Campylobacter colonisation in chicken.
Animals↗
Fermented liquid feed reduces susceptibility of broilers for Salmonella enteritidis.
The presence of Salmonella in chickens is a problem because poultry meat is recognized as a source of human salmonellosis. Fermented feed has characteristics like a high number of lactobacilli and high concentration of lactic acid, which could make chickens less susceptible for infection with Salmonella. Fermented feed might therefore prevent the colonization of chickens with Salmonella. Two studies were performed to quantify the effect of fermented liquid feed on the susceptibility of broilers for Salmonella. The fermented feed was prepared by fermenting a dry broiler feed supplemented with 1.4 parts of water. Lactobacillus plantarum was used for fermentation. The fermented liquid feed (FLF) contained 10(9) to 10(10) cfu lactobacilli per gram, and the pH was 4. Individually housed control chickens and FLF-fed chickens were inoculated with 10(2) to 10(7) cfu Salmonella enteritidis (SE). Colonization was estimated by cloacal swabs and quantitative caecal culture. The proportion of SE-shedding chickens was decreased in FLF-fed chickens. FLF-fed chickens required a longer time after inoculation or a higher inoculation dose to get the same proportion of infected chickens in comparison with dry feed-fed chickens. The level of cecal colonization with Salmonella in the ceca was not different at the end of the experimental period. The results indicate that FLF can hamper the introduction of Salmonella in broiler flocks because the chickens are less susceptible for infection. Fermented liquid feed might therefore be a new hurdle in the strategy to control Salmonella in chicken flocks.
Animal Feed↗
Survival and resuscitation of ten strains of Campylobacter jejuni and Campylobacter coli under acid conditions.
The culturability of 10 strains of Campylobacter jejuni and Campylobacter coli was studied after the bacteria were exposed to acid conditions for various periods of time. Campylobacter cells could not survive 2 h under acid conditions (formic acid at pH 4). The 10 Campylobacter strains could not be recovered, even when enrichment media were used. Viable cells, however, could be detected by a double-staining (5-cyano-2,3-ditolyl tetrazolium chloride [CTC]-4',6'-diamidino-2-phenylindole [DAPI]) technique, demonstrating that the treated bacteria changed into a viable but nonculturable (VBNC) form; the number of VBNC forms decreased over time. Moreover, some VBNC forms of Campylobacter could be successfully resuscitated in specific-free-pathogen fertilized eggs via two routes, amniotic and yolk sac injecting.
Animals↗
Spatial and temporal variation of the intestinal bacterial community in commercially raised broiler chickens during growth.
The objective of this study was to determine whether host, compartment, or environmental specific factors play an important role in the establishment of the intestinal microflora in broiler chickens during growth. This objective was addressed using a 16S rDNA approach. PCR-amplicons from the V6 to V8 regions of the 16S rDNA of intestinal samples were separated by denaturing gradient gel electrophoresis (DGGE). The number of bands in all intestinal compartments increased when broilers grew older, indicating that the dominant bacterial community becomes more complex when chickens age. Each chicken had a unique banding pattern for all locations in the intestinal tract, irrespective of the age of chickens. This suggests that host-related factors affect the establishment of the dominant bacterial community. Banding patterns of intestinal compartments within one chicken were different from each other for broilers older than 4 days, except for both ceca which were highly similar. In 4-day-old broilers, banding patterns from crop, duodenum, and ileum were very similar. We conclude that (unknown) host specific factors play an important role in the development of the intestinal bacterial community in each broiler chicken. Furthermore, compartment-specific factors play an important role in the bacterial development of each intestinal compartment within one chicken.
Animals↗
[From veterinarian to quality control manager. What is going to change in the Netherlands for the practicing large animal veterinarian under influence of the White Paper about food safety?].
The work of farm animal practitioners will change in the coming years as a result of the White Paper on food safety. Both government and the Royal Veterinary Association of the Netherlands are working on an accreditation system for veterinarians. The veterinary practitioner is a link in the chain to achieve safe products. Where in the past emphasis was on the individual animal, it will now be on the herd or flock. The veterinarian will officially determine the health status of the farm, which in turn will play a role in the inspection procedures at the slaughterhouse. This form of farm management will become compulsory for all stockholders within the framework of the Veterinary Network for Supervision. In turn, these developments will affect the veterinary medicine curriculum. New subjects such as quality management will become increasingly important.
Animal Welfare↗
Effect of administration of Lactobacillus crispatus, Clostridium lactatifermentans and dietary lactose on the development of the normal microflora and volatile fatty acids in the caeca of broiler chicks.
1. Lactobacillus crispatus and Clostridium lactatifermentans, both isolated from the caeca of chickens, grown together in an in vitro model system are able to ferment lactose to acetate and propionate. In this study, the capabilities of these organisms were studied in vivo. 2. The effect on concentrations of volatile fatty acids and lactate, together with the development of some bacterial groups in the caeca of chicks, was studied after oral inoculation with L. crispatus and C. lactatifermentans together with dietary lactose. For this purpose, chicks were divided into 4 groups: (i) control group, (ii) dietary lactose, (iii) L. crispatus and C. lactatifermentans, and (iv) dietary lactose together with L. crispitaus and C. lactatifermentans. 3. In general, concentrations of (undissociated) volatile fatty acids in the caeca were not significantly different in broilers receiving both bacteria and dietary lactose compared with control broilers. Concentrations of lactate in the caeca of 14-d-old broilers treated with any of the three treatments were significantly higher than in the caeca of control broilers. 4. This indicates that L. crispatus or other lactate-producing organisms were responsible for the elevated concentrations of lactic acid. Clostridium lactatifermentans has probably not colonised the caeca sufficiently to ferment this lactate further to acetate and propionate. 5. Numbers of Enterobacteriaceae and enterococci in the caeca of broilers receiving both bacteria and dietary lactose were not different from control broilers. 6. We conclude from these results that under the conditions applied in this study a mixture of L. crispatus and C. lactatifermentans with dietary lactose was able to increase lactate concentrations but was unable to increase concentrates of acetate and propionate in the caeca of broiler chicks.
Animals↗
In vitro study on the effect of organic acids on Campylobacter jejuni/coli populations in mixtures of water and feed.
Gastroenteritis caused by Campylobacter spp. infection has been recognized as one of the important public health problems in the developed countries. Outbreaks mostly originate from the consumption of contaminated poultry or infected water. The aim of this study was to determine the bactericidal activity on Campylobacter spp. of organic acids individually and in combinations at different pH levels and times and to compare bactericidal activities with activities of commercially available products. Ten strains of Campylobacter spp. were added in a mixture of water with commercial broiler feed, separately adjusted by four acids: formic, acetic, propionic, and hydrochloric acids, into pH 4.0, 4.5, 5.0, and 5.5. A combination of three organic acids was used in two different formulation ratios: formic:acetic:propionic at 1:2:3 and 1:2:5, at pH 4.0, 4.5, 5.0, and 5.5. All organic acids showed the strongest bactericidal effect on Campylobacter at pH 4.0. In contrast, at pH 5.0 and 5.5, the bactericidal activity of the four acids was low. The combination of organic acids showed a synergistic bactericidal activity at pH 4.5. Interestingly, the effect of the combined organic acids was stronger than the commercial products. Morphological cell changes were studied by transmission electron microscopy to determine the effect of the organic acids on the cell structure of Campylobacter. Some loss of outer membranes of the bacteria could be found in treated groups. Therefore, it can be concluded that organic acids, individually or in combination, have a strong bactericidal effect on Campylobacter spp. Routine application of organic acids to the water supply on poultry farms could prevent or diminish Campylobacter transmission.
Acetic Acid↗
Risk of infection with Leishmania spp. in the canine population in the Netherlands.
The dog is the main reservoir of Leishmania infantum, the causative agent of visceral leishmaniasis (VL) in humans in Southern Europe. In order to identify the risk of dogs from a Leishmania non-endemic area traveling to a Leishmania-endemic area becoming infected and the risk of transmitting infection to humans in non-endemic areas an investigation was performed, in which the results of a questionnaire were combined with the results of a serologic survey. The questionnaire was sent to 1478 at random chosen families in the Netherlands. Of the 59.0% responders 28.0% had one or more dogs and 4.8% of these dogs had visited Southern Europe during the summer period of that year. On a total population of 1,200,000 dogs in the Netherlands, this means that each year some 58,000 dogs are at risk of being exposed to a Leishmania infection in Southern Europe. During the period 1990-1992 blood was collected for serology in 1911 dogs presented to the Utrecht University Clinic because of clinical problems not related to leishmaniasis, of which 434 had been in Southern Europe in the foregoing years. None was serologically positive. From these data it can be deduced that the highest chance to obtain leishmaniasis during a vacation in Southern Europe is mathematically less than 1/434 or less than 0.23%. Serology was also performed during the period 1989-1993 in 597 dogs that had been in Southern Europe and were suspected of leishmaniasis. Titers were positive in 145 of these samples. Sixty-four of these dogs were born in the Mediterranean and had been imported into the Netherlands. Excluding these imported dogs, it was calculated that at least 0.027% of the 58,000 dogs yearly taken to Southern Europe during holidays become infected with Leishmania. In order to establish the risk of disease transmission for people in close contact with an infected dog, serum samples of owners and house mates of 37 dogs with leishmaniasis were tested. All 112 sera tested negative. It was concluded that the risk to get leishmaniasis was between 0.027% and 0.23% for the dog when taken to Southern Europe during vacation, and that the risk for owners in non-endemic areas to get leishmaniasis from an infected dog is minimal.
Agglutination Tests↗
Sensitivity of Shiga toxin-producing Escherichia coli (STEC) strains for colicins under different experimental conditions.
Twenty Escherichia coli strains producing well-characterised colicins were tested for their inhibitory activity against five Shiga toxin-producing E. coli (STEC) strains using different media under aerobic and anaerobic conditions. The five STEC strains used were of serotype O26, O111, O128, O145 and O157:H7 which are frequently isolated serotypes associated with disease in humans. The main route of infection for humans is through the eating of badly cooked or handled beef. The major reservoir for STEC strains in cattle is the rumen. To mimic the situation in the rumen of cattle, overlay assays were also performed under anaerobic conditions in the presence of 30% rumen fluid. Colicins E1, E4, E8-J, K and S4 are most active against STEC strains under anaerobic conditions in the absence or presence of rumen fluid. These colicins will be used in future experiments with the aim to eradicate the presence of STEC in cattle.
Aerobiosis↗
Salmonella in slaughter pigs: prevalence, serotypes and critical control points during slaughter in two slaughterhouses.
The purpose of this study was to show the distribution of Salmonella in slaughtered pigs and the environment of the slaughterhouse. 1,114 samples of slaughtered pigs (six different samples for Salmonella isolation and one serum sample for ELISA on antibodies per pig) and 477 samples of the slaughterhouse environment were collected in two slaughterhouses on two sampling days per slaughterhouse. Salmonella was isolated from one or more samples of 47% of the pigs. The highest prevalence of Salmonella was observed in rectal content samples (25.6%), whereas the lowest prevalence of Salmonella was observed on the carcasses (1.4%). The prevalence of Salmonella in other samples was: 19.6% in tonsils, 9.3% on livers, 9.3% on tongues, and 9.3% in mesenterial lymphnodes. The prevalence of Salmonella in environmental samples was high in the drain water samples in both slaughterhouses (61%) and on the carcass splitter in one slaughterhouse (33%). Salmonella typhimurium was the most frequently isolated serotype in pig samples and environmental samples in both slaughterhouses: 43% of the Salmonella isolates from pigs and 33% of the Salmonella isolates from the environment was S. typhimurium. The results of this study show that Salmonella prevalences in pigs differ a lot, depending on which part of the pig is sampled. Not all different samples of the pig will become available for human consumption, but collecting more than one sample per pig showed that Salmonella can be found in almost the whole pig. The result of surface samples of carcass and liver gives information about hygiene during the slaughter process; the result of tonsils, lymphnodes and rectal contents, combined with the serological result, gives information about infection of the pig before the slaughter process (on the farm, during transport or in lairage). It can be concluded that results of Salmonella isolation of slaughter pigs should always be carefully interpreted, depending on the type of sample that has been collected.
Abattoirs↗
Salmonella in slaughter pigs: the effect of logistic slaughter procedures of pigs on the prevalence of Salmonella in pork.
A substantial part of the finishing pigs in the Netherlands is infected with Salmonella. Infection of pigs with Salmonella can occur already on the farm. Pigs can also get infected or contaminated during transport, lairage or slaughter. The aim of this study was to evaluate the effect of separating pigs from Salmonella-infected farms from pigs from Salmonella-free farms during transport, lairage and slaughter on the prevalence of Salmonella on pork after slaughter. Two experiments were carried out. In the first experiment, farms were selected to participate, based on serology of the pigs (Dutch Salmonella ELISA). The pigs were slaughtered at the beginning of the day: firstly, sero-negative herds, secondly, sero-positive herds and thirdly, again sero-negative herds. The latter were slaughtered to investigate the effect of a contaminated slaughterline due to a previously slaughtered positive herd. In the second experiment, farms were selected to participate, based on both serology and bacteriology of the pigs on the farm. Two hundred pigs from Salmonella-free farms were slaughtered after 200 pigs from Salmonella-infected farms. Results showed that the prevalence of Salmonella in pork samples of sero-negative herds was lower than in samples of sero-positive herds. Results also showed that Salmonella contamination of carcasses after slaughter was partially caused by Salmonella-infected herds that were slaughtered before, and partially by residential flora of the slaughterhouse. It is concluded that separate slaughter of sero-negative pig herds can be useful to decrease the prevalence of Salmonella-contaminated pork after slaughter. To avoid cross-contamination by residential flora from trucks, lairage and slaughterline, cleaning and disinfection have to be improved.
Abattoirs↗
Monitoring of transmission of Salmonella enterica serovars in pigs using bacteriological and serological detection methods.
The standard method to detect Salmonella positive pigs is bacteriological examination of the faeces, but in recent years the use of Salmonella-ELISA's have become available to screen pigs for serological evidence of infection. This study was conducted to monitor the transmission of five different Salmonella enterica serovars (S. Typhimurium, S. Brandenburg, S. Panama, S. Livingstone, and S. Goldcoast) in fattening pigs and to test the feasibility of Salmonella-ELISA, using seeder pigs as a mode of transmission. Serovar dependence in transmission was observed. The Salmonella-ELISA proved to be useful to detect S. Typhimurium and S. Brandenburg in herds but was of limited value to demonstrate S. Livingstone, S. Goldcoast, and S. Panama.
Animals↗
[Lambing sheep as source of severe psittacosis in pregnancy].
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Animals↗
Human health hazards associated with the administration of antimicrobials to slaughter animals. Part I. An assessment of the risks of residues of tetracyclines in pork.
This article describes the assessment of consumer risks of residues of tetracyclines in slaughter pigs in the Netherlands. The assessed risks were toxic and allergic reactions, and the disturbance of the consumers' intestinal flora. Toxic and allergic reactions in humans and animals have only been observed at therapeutic doses, affecting between an estimated 1 in 5,000 and one 1 in 140,000 individuals exposed. Residues of tetracyclines in pigs are closely associated with treatment with injectable formulations. Established Maximum Residue Levels (MRLs) do not reflect actual consumer risks in case a limit is violated incidentally. For example, when the established MRLs for tetracyclines in meat are exceeded with a factor 400, 40,000, and 200,000, respectively, the actual risk of an adverse drug reaction for the consumer following a single consumption of this meat is maximally 1 in 3 million, 1 in 300,000, and 1 in 8,000, respectively. At the current estimated low levels of incidental exposure via pork, the annual risk of negative health effects for a random consumer is estimated at maximally 1 in 33 million. The annual risk that a temporary disturbance of the intestinal flora may also result in a facilitated infection with certain enteropathogens, such as Salmonella spp., is estimated at 1 in 45 million. It is concluded that the current microbiological risks of pork are greater than the risks of residues of tetracyclines as such, and that the control of the microbiological risks of pork should therefore be given first priority.
Animals↗