Publications by authors named "Piet Vellema"

31 Publications

Dairy Sheep Played a Minor Role in the 2005-2010 Human Q Fever Outbreak in The Netherlands Compared to Dairy Goats.

Pathogens 2021 Dec 3;10(12). Epub 2021 Dec 3.

Department of Small Ruminant Health, Royal GD, P.O. Box 9, 7400 AA Deventer, The Netherlands.

Q fever is an almost ubiquitous zoonosis caused by . This organism infects several animal species, as well as humans, and domestic ruminants like cattle, sheep and goats are an important animal reservoir of . In 2007, a sudden rise in notified human Q fever cases occurred in The Netherlands, and by the end of 2009, more than 3500 human Q fever patients had been notified. Dairy sheep and dairy goats were suspected to play a causal role in this human Q fever outbreak, and several measures were taken, aiming at a reduction of shedding by infected small ruminants, in order to reduce environmental contamination and thus human exposure. One of the first measures was compulsory notification of more than five percent abortion within thirty days for dairy sheep and dairy goat farms, starting 12 June 2008. After notification, an official farm inspection took place, and laboratory investigations were performed aiming at ruling out or demonstrating a causal role of . These measures were effective, and the number of human Q fever cases decreased; levels are currently the same as they were prior to 2007. The effect of these measures was monitored using a bulk tank milk (BTM) PCR and an antibody ELISA. The percentage PCR positive dairy herds and flocks decreased over time, and dairy sheep flocks tested PCR positive significantly less often and became PCR negative earlier compared to dairy goat herds. Although there was no difference in the percentage of dairy goat and dairy sheep farms with a abortion outbreak, the total number of shedding dairy sheep was much lower than the number of shedding dairy goats. Combined with the fact that Q fever patients lived mainly in the proximity of infected dairy goat farms and that no Q fever patients could be linked directly to dairy sheep farms, although this may have happened in individual cases, we conclude that dairy sheep did not play a major role in the Dutch Q fever outbreak. BTM monitoring using both a PCR and an ELISA is essential to determine a potential risk, not only for The Netherlands but for other countries with small ruminant dairy industries.
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http://dx.doi.org/10.3390/pathogens10121579DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8703908PMC
December 2021

An Accessible Diagnostic Toolbox to Detect Bacterial Causes of Ovine and Caprine Abortion.

Pathogens 2021 Sep 6;10(9). Epub 2021 Sep 6.

Department of Research and Development, Royal GD, P.O. Box 9, 7400 AA Deventer, The Netherlands.

Results of laboratory investigations of ovine and caprine cases of abortion in the lambing season 2015-2016 were analyzed, using pathology records of submissions to Royal GD (Deventer, the Netherlands) from January until and including April 2016, in comparison with the results of two accessible alternative techniques for sampling aborted lambs and kids, swabbing the fetal oropharynx and puncture of the fetal lung. was the main cause of abortion in sheep as well as in goats. Other causes of abortion were spp., spp., , and Ovine pathological submissions resulted more often in detecting an infectious agent compared to caprine submissions. For the three main bacterial causes of abortion, spp., spp., and spp., compared to results of the pathological examination, oropharynx mucus, and fetal lung puncture samples showed an observed agreement of 0.87 and 0.89, an expected agreement of 0.579 and 0.584, and a kappa value of 0.691 and 0.737 (95% CI: 0.561-0.82 and 0.614-0.859), respectively. The agreement between the results of the pathological examination and both fetal lung puncture and oropharynx mucus samples was classified as good. In conclusion, although a full step-wise post-mortem examination remains the most proper way of investigating small ruminant abortions, the easily accessible, low-threshold tools for practitioners and farmers as described in this paper not only provide reliable results compared to results of the post-mortem examination but also stimulates farmers and veterinarians to submit fetuses and placentas if necessary. Suggestions for further improvement of both alternatives have been summarized. Both alternatives could also be tailor-made for specific regions with their specific causes of abortion.
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http://dx.doi.org/10.3390/pathogens10091147DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8468688PMC
September 2021

Zoonotic risks of pathogens from sheep and their milk borne transmission.

Small Rumin Res 2020 Aug 15;189:106123. Epub 2020 May 15.

Royal GD, Department of Small Ruminant Health, Deventer, The Netherlands.

Sheep were domesticated around 9000 BC in the Middle East, and since then milk from sheep gradually became very popular, not only for drinking but also for making cheeses and other dairy products. Nowadays, these dairy products are also important for people with an allergy to cow milk, and these products are an essential part of the local daily diet in regions of the world that are not suitable for cows and goats. Consumption of raw milk and raw milk products has a zoonotic risk, and with regard to sheep, the main pathogens associated with such dairy products are: , spp., spp., spp., Shiga-toxin producing , , tick borne encephalitis virus, and . Especially, young children, elderly people, pregnant women and immunocompromised (YOPI) persons, and those suffering from disease should be aware of the risk of consuming raw milk and raw milk products. This latter risk can be reduced by proper flock health management, prevention of contamination during milking, adequate milk processing, transport, and refrigerated storage. Only processes equaling pasteurization sufficiently reduce zoonotic risks from milk and milk products, but proper cooling is essential and recontamination must be prevented. Therefore, strict hygiene practices throughout the production process and supply chain especially for raw milk and raw dairy products, should be applied. Small scale production systems pose a greater risk compared to industrialized production systems because of a less protocolized and controlled production process. This manuscript describes zoonotic risks of pathogens from sheep and their milk borne transmission. Additionally, routes of contamination, possibilities for multiplication, and prevention measures thereof are described. We summarize some major human outbreaks caused by consumption of sheep milk and products made thereof, and finally discuss their implications.
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http://dx.doi.org/10.1016/j.smallrumres.2020.106123DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7227596PMC
August 2020

Relationship between Coxiella burnetii (Q fever) antibody serology and time spent outdoors.

J Infect 2020 07 21;81(1):90-97. Epub 2020 Apr 21.

Institute for Risk Assessment Sciences (IRAS), Division Environmental Epidemiology and Veterinary Public Health, Utrecht University, Utrecht, the Netherlands.

Background/aim: From 2007 through 2010, the Netherlands experienced the largest recorded Q fever outbreak to date. People living closer to Coxiella burnetii infected goat farms were at increased risk for acute Q fever. Time spent outdoors near infected farms may have contributed to exposure to C. burnetii. The aim of this study was to retrospectively evaluate whether hours/week spent outdoors, in the vicinity of previously C. burnetii infected goat farms, was associated with presence of antibodies against C. burnetii in residents of a rural area in the Netherlands.

Methods: Between 2014-2015, we collected C. burnetii antibody serology and self-reported data about habitual hours/week spent outdoors near the home from 2494 adults. From a subgroup we collected 941 GPS tracks, enabling analyses of active mobility in the outbreak region. Participants were categorised as exposed if they spent time within specified distances (500m, 1000m, 2000m, or 4000m) of C. burnetii infected goat farms. We evaluated whether time spent near these farms was associated with positive C. burnetii serology using spline analyses and logistic regression.

Results: People that spent more hours/week outdoors near infected farms had a significantly increased risk for positive C. burnetii serology (time spent within 2000m of a C. burnetii abortion-wave positive farm, OR 3.6 (1.2-10.6)), compared to people spending less hours/week outdoors.

Conclusions: Outdoor exposure contributed to the risk of becoming C. burnetii serology positive. These associations were stronger if people spent more time near C. burnetii infected farms. Outdoor exposure should, if feasible, be included in outbreak investigations.
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http://dx.doi.org/10.1016/j.jinf.2020.04.013DOI Listing
July 2020

subsp. ELISA Responses in Milk Samples from Vaccinated and Nonvaccinated Dairy Goat Herds in The Netherlands.

Vet Sci 2019 Jun 22;6(2). Epub 2019 Jun 22.

Department of Small Ruminant Health, GD Animal Health, P.O. Box 9, 7400 AA Deventer, The Netherlands.

The aims of our study were to calculate the most appropriate cut-off value for milk samples in a serum-validated subsp. (MAP) ELISA and to analyze MAP ELISA responses in milk samples from vaccinated and nonvaccinated dairy goats in the Netherlands. Analyzed herds were representative for location and herd size of dairy goat herds in the Netherlands. A significantly higher proportion of the analyzed 49 herds were organic as compared with the total Dutch dairy goat population. First, the MAP ELISA was optimized using 992 paired serum and milk samples. At a cut-off of 25 S/P%, the relative sensitivity (Se) was 58.4% ( = 992, 95% CI: 48.8%-67.6%) and relative specificity (Sp) was 98.5% ( = 992, 95% CI: 97.5%-99.2%), as compared to serum ELISA results. The percentage of positively tested herds was 78.2% ( = 49, 95% CI: 63.4%-88.1%). The percentage of positive milk samples per herd ( = 22) was on average 4.6% (median, min, and max of 4.7%, 0.0%, and 10.7%, respectively). Average age of ELISA-positive (3.2 years) and -negative goats (3.2 years) was not different. Significantly more vaccinated goats tested positive (6.7%) as compared with nonvaccinated goats (1.1%). This study shows that a high number of vaccinated and nonvaccinated commercial dairy goat herds in the Netherlands have MAP-ELISA-positive goats.
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http://dx.doi.org/10.3390/vetsci6020058DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6632119PMC
June 2019

Incidence, possible risk factors and therapies for pseudopregnancy on Dutch dairy goat farms: a cross-sectional study.

Vet Rec 2019 06 19;184(25):770. Epub 2019 Jun 19.

Department of Epidemiology, Gezondheidsdienst voor Dieren BV, Deventer, The Netherlands.

Pseudopregnancy is a frequently diagnosed reproductive disorder in (dairy) goats. This cross-sectional study evaluates the incidence, possible risk factors and therapies for pseudopregnancy on Dutch dairy goat farms. Two questionnaires, one for farmers and one for veterinarians, were designed and included questions about general farm demographics, breeding management, hormonal oestrous induction, treatment, measures for reduction and stress moments in dairy goats in the period June 1, 2016-May 31, 2017. In total, 43 farmers (21.5 per cent response rate) and 27 veterinarians (22.5 per cent response rate) completed the questionnaire. The annual incidence of pseudopregnancy varied between 1 and 54 per cent per farm, with a mean annual incidence of 17 per cent (95 per cent CI 0.14 to 0.21). In this study, we found a significant association between incidence of pseudopregnancy and a higher percentage of goats with an extended lactation (p<0.0001) and between incidence of pseudopregnancy and the number of ultrasound examinations per year (p<0.0001). The recommended therapy in literature consists of two administrations of prostaglandins. This was only correctly applied by 10 per cent of the farms. On 52 per cent of the farms, an overdose was used comparing to the recommended dose in literature.
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http://dx.doi.org/10.1136/vr.105346DOI Listing
June 2019

Risk factors related to Toxoplasma gondii seroprevalence in indoor-housed Dutch dairy goats.

Prev Vet Med 2016 Feb;124:45-51

Toxoplasma gondii can cause disease in goats, but also has impact on human health through food-borne transmission. Our aims were to determine the seroprevalence of T. gondii infection in indoor-housed Dutch dairy goats and to identify the risk factors related to T. gondii seroprevalence. Fifty-two out of ninety approached farmers with indoor-kept goats (58%) participated by answering a standardized questionnaire and contributing 32 goat blood samples each. Serum samples were tested for T. gondii SAG1 antibodies by ELISA and results showed that the frequency distribution of the log10-transformed OD-values fitted well with a binary mixture of a shifted gamma and a shifted reflected gamma distribution. The overall animal seroprevalence was 13.3% (95% CI: 11.7–14.9%), and at least one seropositive animal was found on 61.5% (95% CI: 48.3–74.7%) of the farms. To evaluate potential risk factors on herd level, three modeling strategies (Poisson, negative binomial and zero-inflated) were compared. The negative binomial model fitted the data best with the number of cats (1–4 cats: IR: 2.6, 95% CI: 1.1–6.5; > = 5 cats:IR: 14.2, 95% CI: 3.9–51.1) and mean animal age (IR: 1.5, 95% CI: 1.1–2.1) related to herd positivity. In conclusion, the ELISA test was 100% sensitive and specific based on binary mixture analysis. T. gondii infection is prevalent in indoor housed Dutch dairy goats but at a lower overall animal level seroprevalence than outdoor farmed goats in other European countries, and cat exposure is an important risk factor.
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http://dx.doi.org/10.1016/j.prevetmed.2015.12.014DOI Listing
February 2016

Integrating interdisciplinary methodologies for One Health: goat farm re-implicated as the probable source of an urban Q fever outbreak, the Netherlands, 2009.

BMC Infect Dis 2015 Sep 3;15:372. Epub 2015 Sep 3.

Centre for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), PO Box 1, , 3720 BA, Bilthoven, The Netherlands.

Background: In spring 2008, a goat farm experiencing Q fever abortions ("Farm A") was identified as the probable source of a human Q fever outbreak in a Dutch town. In 2009, a larger outbreak with 347 cases occurred in the town, despite no clinical Q fever being reported from any local farm.

Methods: Our study aimed to identify the source of the 2009 outbreak by applying a combination of interdisciplinary methods, using data from several sources and sectors, to investigate seventeen farms in the area: namely, descriptive epidemiology of notified cases; collation of veterinary data regarding the seventeen farms; spatial attack rate and relative risk analyses; and GIS mapping of farms and smooth incidence of cases. We conducted further spatio-temporal analyses that integrated temporal data regarding date of onset with spatial data from an atmospheric dispersion model with the most highly suspected source at the centre.

Results: Our analyses indicated that Farm A was again the most likely source of infection, with persons living within 1 km of the farm at a 46 times larger risk of being a case compared to those living within 5-10 km. The spatio-temporal analyses demonstrated that about 60 - 65 % of the cases could be explained by aerosol transmission from Farm A assuming emission from week 9; these explained cases lived significantly closer to the farm than the unexplained cases (p = 0.004). A visit to Farm A revealed that there had been no particular changes in management during the spring/summer of 2009, nor any animal health problems around the time of parturition or at any other time during the year.

Conclusions: We conclude that the probable source of the 2009 outbreak was the same farm implicated in 2008, despite animal health indicators being absent. Veterinary and public health professionals should consider farms with past as well as current history of Q fever as potential sources of human outbreaks.
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http://dx.doi.org/10.1186/s12879-015-1083-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4558730PMC
September 2015

A probably minor role for land-applied goat manure in the transmission of Coxiella burnetii to humans in the 2007-2010 Dutch Q fever outbreak.

PLoS One 2015 27;10(3):e0121355. Epub 2015 Mar 27.

Department of Small Ruminant Health, GD Animal Health, Deventer, The Netherlands.

In 2007, Q fever started to become a major public health problem in the Netherlands, with small ruminants as most probable source. In order to reduce environmental contamination, control measures for manure were implemented because of the assumption that manure was highly contaminated with Coxiella burnetii. The aims of this study were 1) to clarify the role of C. burnetii contaminated manure from dairy goat farms in the transmission of C. burnetii to humans, 2) to assess the impact of manure storage on temperature profiles in dunghills, and 3) to calculate the decimal reduction time of the Nine Mile RSA 493 reference strain of C. burnetii under experimental conditions in different matrices. For these purposes, records on distribution of manure from case and control herds were mapped and a potential relation to incidences of human Q fever was investigated. Additionally, temperatures in two dunghills were measured and related to heat resistance of C. burnetii. Results of negative binomial regression showed no significant association between the incidence of human Q fever cases and the source of manure. Temperature measurements in the core and shell of dunghills on two farms were above 40°C for at least ten consecutive days which would result in a strong reduction of C. burnetii over time. Our findings indicate that there is no relationship between incidence of human Q fever and land applied manure from dairy goat farms with an abortion wave caused by C. burnetii. Temperature measurements in dunghills on two farms with C. burnetii shedding dairy goat herds further support the very limited role of goat manure as a transmission route during the Dutch human Q fever outbreak. It is very likely that the composting process within a dunghill will result in a clear reduction in the number of viable C. burnetii.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0121355PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4376525PMC
March 2016

Estimation of the use of antibiotics in the small ruminant industry in The Netherlands in 2011 and 2012.

PLoS One 2014 12;9(8):e105052. Epub 2014 Aug 12.

Department of small ruminant health, GD Animal Health, Deventer, The Netherlands.

The aim of this study was to estimate the quantity of antibiotics and classes of antibiotics used in the small ruminant industry in the Netherlands in 2011 and 2012. Twelve large veterinary practices, located throughout the Netherlands were selected for this study. All small ruminant farms associated with these practices that had complete records on the quantity of antibiotics prescribed were included. The veterinary practices provided data on all antibiotics prescribed, and the estimated animal used daily dose of antibiotics per year (AUDD/Y) was calculated for each farm. The median AUDD/Y in small ruminant farms was zero in both years (mean 0.60 in 2011, and 0.62 in 2012). The largest quantity of antibiotic use was observed in the professional goat industry (herds of ≥32 goats) with a median AUDD/Y of 1.22 in 2011 and 0.73 in 2012. In the professional sheep industry (flocks of ≥32 sheep), the median AUDD/Y was 0 in 2011 and 0.10 in 2012. In the small scale industry (flocks or herds of <32 sheep or goats), the median AUDD/Y never exceeded 0. The most frequently prescribed antibiotics in the small scale industry and professional sheep farms belonged to the penicillin class. In professional goat farms, antibiotics of the aminoglycoside class were most frequently prescribed. This study provides the first assessment on the quantity of antibiotic use in the small ruminant industry. Given a comparable attitude towards antibiotic use, these results might be valid for small ruminant populations in other north-western European countries as well. The antibiotic use in the small ruminant industry appeared to be low, and is expected to play a minor role in the development of antibiotic resistance. Nevertheless, several major zoonotic bacterial pathogens are associated with the small ruminant industry, and it remains important that antibiotics are used in a prudent way.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0105052PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4130639PMC
April 2016

Risk factors for malformations and impact on reproductive performance and mortality rates of Schmallenberg virus in sheep flocks in the Netherlands.

PLoS One 2014 17;9(6):e100135. Epub 2014 Jun 17.

Department of Small Ruminant Health, GD Animal Health, Deventer, The Netherlands.

In Northwestern Europe, an epizootic outbreak of congenital malformations in newborn lambs due to infection with Schmallenberg virus (SBV) started at the end of 2011. The objectives of this study were to describe clinical symptoms of SBV infection, the effect of infection on mortality rates, and reproductive performance in sheep, as well as to identify and quantify flock level risk factors for SBV infections resulting in malformations in newborn lambs. A case-control study design was used, with 93 case flocks that had notified malformed lambs and 84 control flocks with no such lambs. Overall animal seroprevalence in case flocks was estimated at 82.0% (95% CI: 74.3-87.8), and was not significantly different from the prevalence in control flocks being 76.4% (95% CI: 67.2-83.6). The percentages of stillborn lambs or lambs that died before weaning, repeat breeders, and lambs with abnormal suckling behaviour were significantly higher in case flocks compared to control flocks. However, effect of SBV infection on mortality rates and reproductive performance seemed to be limited. Multivariable analysis showed that sheep flocks with an early start of the mating season, i.e. before August 2011 (OR = 33.1; 95% CI: 10.0-109.8) and in August 2011 (OR = 8.2; 95% CI: 2.7-24.6) had increased odds of malformations in newborn lambs caused by SBV compared to sheep flocks with a start of the mating season in October 2011. Other flock-level risk factors for malformations in newborn lambs were purchase of silage (OR 5.0; 95% CI: 1.7-15.0) and flocks with one or more dogs (OR = 3.3; 95% CI: 1.3-8.3). Delaying mating until October could be a potential preventive measure for naïve animals to reduce SBV induced losses. As duration of immunity after infection with SBV is expected to last for several years, future SBV induced congenital malformations are mainly expected in offspring of early mated seronegative animals.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0100135PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4061107PMC
October 2015

Test and cull of high risk Coxiella burnetii infected pregnant dairy goats is not feasible due to poor test performance.

Vet J 2014 May 28;200(2):343-5. Epub 2014 Feb 28.

Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 7, 3584 CL Utrecht, The Netherlands. Electronic address:

A major human Q fever epidemic occurred in The Netherlands during 2007-2009. In response, all pregnant goats from infected herds were culled before the 2010 kidding season without individual testing. The aim of this study was to assess whether high risk animals from recently infected naive herds can be identified by diagnostic testing. Samples of uterine fluid, milk and vaginal mucus from 203 euthanized pregnant goats were tested by PCR or ELISA. The results suggest that testing followed by culling of only the high risk animals is not a feasible method for protecting public health, mainly due to the low specificity of the tests and variability between herds. The risk of massive bacterial shedding during abortion or parturition can only be prevented by removal of all pregnant animals from naive recently infected herds.
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http://dx.doi.org/10.1016/j.tvjl.2014.02.015DOI Listing
May 2014

Seroepidemiological survey for Coxiella burnetii antibodies and associated risk factors in Dutch livestock veterinarians.

PLoS One 2013 16;8(1):e54021. Epub 2013 Jan 16.

Department of Small Ruminant Health, Animal Health Service, Deventer, The Netherlands.

Since 2007, Q fever has become a major public health problem in the Netherlands and goats were the most likely source of the human outbreaks in 2007, 2008 and 2009. Little was known about the consequences of these outbreaks for those professional care providers directly involved. The aim of this survey was to estimate the seroprevalence of antibodies against C. burnetii among Dutch livestock veterinarians and to determine possible risk factors. Single blood samples from 189 veterinarians, including veterinary students in their final year, were collected at a veterinary conference and a questionnaire was filled in by each participant. The blood samples were screened for IgG antibodies against phase I and phase II antigen of C. burnetii using an indirect immunofluorescent assay, and for IgM antibodies using an ELISA. Antibodies against C. burnetii were detected in 123 (65.1%) out of 189 veterinarians. Independent risk factors associated with seropositivity were number of hours with animal contact per week, number of years graduated as veterinarian, rural or sub urban living area, being a practicing veterinarian, and occupational contact with swine. Livestock veterinarians should be aware of this risk to acquire an infection with C. burnetii. Physicians should consider potential infection with C. burnetii when treating occupational risk groups, bearing in mind that the burden of disease among veterinarians remains uncertain. Vaccination of occupational risk groups should be debated.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0054021PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3546960PMC
July 2013

Smooth incidence maps give valuable insight into Q fever outbreaks in The Netherlands.

Geospat Health 2012 Nov;7(1):127-34

Centre for Infectious Disease Control, National Institute for Public Health and the Environment, PO Box 1, 3720 BA Bilthoven, The Netherlands.

From 2007 through 2009, The Netherlands faced large outbreaks of human Q fever. Control measures focused primarily on dairy goat farms because these were implicated as the main source of infection for the surrounding population. However, in other countries, outbreaks have mainly been associated with non-dairy sheep and The Netherlands has many more sheep than goats. Therefore, a public discussion arose about the possible role of non-dairy (meat) sheep in the outbreaks. To inform decision makers about the relative importance of different infection sources, we developed accurate and high-resolution incidence maps for detection of Q fever hot spots. In the high incidence area in the south of the country, full postal codes of notified Q fever patients with onset of illness in 2009, were georeferenced. Q fever cases (n = 1,740) were treated as a spatial point process. A 500 x 500 m grid was imposed over the area of interest. The number of cases and the population number were counted in each cell. The number of cases was modelled as an inhomogeneous Poisson process where the underlying incidence was estimated by 2-dimensional P-spline smoothing. Modelling of numbers of Q fever cases based on residential addresses and population size produced smooth incidence maps that clearly showed Q fever hotspots around infected dairy goat farms. No such increased incidence was noted around infected meat sheep farms. We conclude that smooth incidence maps of human notifications give valuable information about the Q fever epidemic and are a promising method to provide decision support for the control of other infectious diseases with an environmental source.
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http://dx.doi.org/10.4081/gh.2012.111DOI Listing
November 2012

Lack of evidence for zoonotic transmission of Schmallenberg virus.

Emerg Infect Dis 2012 Nov;18(11):1746-54

National Institute for Public Health and the Environment, Bilthoven, the Netherlands.

The emergence of Schmallenberg virus (SBV), a novel orthobunyavirus, in ruminants in Europe triggered a joint veterinary and public health response to address the possible consequences to human health. Use of a risk profiling algorithm enabled the conclusion that the risk for zoonotic transmission of SBV could not be excluded completely. Self-reported health problems were monitored, and a serologic study was initiated among persons living and/or working on SBV-affected farms. In the study set-up, we addressed the vector and direct transmission routes for putative zoonotic transfer. In total, 69 sheep farms, 4 goat farms, and 50 cattle farms were included. No evidence for SBV-neutralizing antibodies was found in serum of 301 participants. The lack of evidence for zoonotic transmission from either syndromic illness monitoring or serologic testing of presumably highly exposed persons suggests that the public health risk for SBV, given the current situation, is absent or extremely low.
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http://dx.doi.org/10.3201/eid1811.120650DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3559138PMC
November 2012

Seroprevalence and risk factors for Coxiella burnetii (Q fever) seropositivity in dairy goat farmers' households in The Netherlands, 2009-2010.

PLoS One 2012 27;7(7):e42364. Epub 2012 Jul 27.

Centre for Infectious Disease Control, National Institute for Public Health and The Environment, Bilthoven, The Netherlands.

Community Q fever epidemics occurred in The Netherlands in 2007-2009, with dairy goat and dairy sheep farms as the implicated source. The aim of the study was to determine the seroprevalence and risk factors for seropositivity in dairy goat farmers and their household members living or working on these farms. Sera of 268 people living or working on 111 dairy goat farms were tested for Coxiella burnetii IgG and IgM antibodies using immunofluorescence assay. Seroprevalences in farmers, spouses and children (12-17 years) were 73.5%, 66.7%, and 57.1%, respectively. Risk factors for seropositivity were: performing three or more daily goat-related tasks, farm location in the two southern provinces of the country, proximity to bulk milk-positive farms, distance from the nearest stable to residence of 10 meters or less, presence of cats and multiple goat breeds in the stable, covering stable air spaces and staff not wearing farm boots. Goat farmers have a high risk to acquire this occupational infection. Clinicians should consider Q fever in this population presenting with compatible symptoms to allow timely diagnosis and treatment to prevent severe sequelae. Based on the risk factors identified, strengthening general biosecurity measures is recommended such as consistently wearing boots and protective clothing by farm staff to avoid indirect transmission and avoiding access of companion animals in the goat stable. Furthermore, it provides an evidence base for continuation of the current vaccination policy for small ruminants, preventing spread from contaminated farms to other farms in the vicinity. Finally, vaccination of seronegative farmers and household members could be considered.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0042364PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3407076PMC
January 2013

Seroprevalence and risk factors of Q fever in goats on commercial dairy goat farms in the Netherlands, 2009-2010.

BMC Vet Res 2011 Dec 30;7:81. Epub 2011 Dec 30.

Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, the Netherlands.

Background: The aim of this study was to estimate the seroprevalence of Coxiella burnetii in dairy goat farms in the Netherlands and to identify risk factors for farm and goat seropositivity before mandatory vaccination started. We approached 334 eligible farms with more than 100 goats for serum sampling and a farm questionnaire. Per farm, median 21 goats were sampled. A farm was considered positive when at least one goat tested ELISA positive.

Results: In total, 2,828 goat serum samples from 123 farms were available. Farm prevalence was 43.1% (95%CI: 34.3%-51.8%). Overall goat seroprevalence was 21.4% (95%CI: 19.9%-22.9%) and among the 53 positive farms 46.6% (95%CI: 43.8%-49.3%). Multivariable logistic regression analysis included 96 farms and showed that farm location within 8 kilometres proximity from a bulk milk PCR positive farm, location in a municipality with high cattle density (≥ 100 cattle per square kilometre), controlling nuisance animals through covering airspaces, presence of cats or dogs in the goat stable, straw imported from abroad or unknown origin and a herd size above 800 goats were independent risk factors associated with Q fever on farm level. At animal level almost identical risk factors were found, with use of windbreak curtain and artificial insemination as additional risk factors.

Conclusion: In 2009-2010, the seroprevalence in dairy goats in the Netherlands increased on animal and farm level compared to a previous study in 2008. Risk factors suggest spread from relatively closely located bulk milk-infected small ruminant farms, next to introduction and spread from companion animals, imported straw and use of artificial insemination. In-depth studies investigating the role of artificial insemination and bedding material are needed, while simultaneously general biosecurity measures should be updated, such as avoiding companion animals and vermin entering the stables, next to advice on farm stable constructions on how to prevent introduction and minimize airborne transmission from affected dairy goat farms to prevent further spread to the near environment.
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http://dx.doi.org/10.1186/1746-6148-7-81DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3292966PMC
December 2011

Proximity to goat farms and Coxiella burnetii seroprevalence among pregnant women.

Emerg Infect Dis 2011 Dec;17(12):2360-3

National Institute for Public Health and the Environment, Bilthoven, the Netherlands.

During 2007-2009, we tested serum samples from 2,004 pregnant women living in an area of high Q fever incidence in the Netherlands. Results confirmed that presence of antibodies against Coxiella burnetii is related to proximity to infected dairy goat farms. Pregnant women and patients with certain cardiovascular conditions should avoid these farms.
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http://dx.doi.org/10.3201/eid1712.110738DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3311170PMC
December 2011

The 2007–2010 Q fever epidemic in The Netherlands: characteristics of notified acute Q fever patients and the association with dairy goat farming.

FEMS Immunol Med Microbiol 2012 Feb;64(1):3-12

National Institute for Public Health and the Environment, Centre for Infectious Disease Control, Bilthoven, The Netherlands.

We describe the Q fever epidemic in the Netherlands with emphasis on the epidemiological characteristics of acute Q fever patients and the association with veterinary factors. Data from 3264 notifications for acute Q fever in the period from 2007 through 2009 were analysed. The patients most affected were men, smokers and persons aged 40–60 years. Pneumonia was the most common clinical presentation (62% in 2007 and 2008). Only 3.2% of the patients were working in the agriculture sector and 0.5% in the meat-processing industry including abattoirs. Dairy goat farms with Coxiella burnetii-induced abortion waves were mainly located in the same area where human cases occurred. Airborne transmission of contaminated dust particles from commercial dairy goat farms in densely populated areas has probably caused this epidemic. In 2010, there was a sharp decline in the number of notified cases following the implementation of control measures on dairy goat and sheep farms such as vaccination, hygiene measures and culling of pregnant animals on infected farms. In combination with a rise in the human population with antibodies against C. burnetii, these have most likely ended the outbreak. Development of chronic Q fever in infected patients remains an important problem for years to come.
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http://dx.doi.org/10.1111/j.1574-695X.2011.00876.xDOI Listing
February 2012

Q fever in The Netherlands: the role of local environmental conditions.

Int J Environ Health Res 2011 Dec 23;21(6):441-51. Epub 2011 May 23.

National Institute for Public Health and the Environment, Bilthoven, The Netherlands.

The Netherlands is facing a Q fever epidemic in which dairy goats are implicated. People living close to an affected farm have an increased risk. However, no human cases were reported around a number of farms with serious Q fever problems. To assess the role of local environmental conditions which may add to the transmission or risk of Q fever, we gathered datasets on vegetation, land use, soil characteristics, and weather conditions in 5 km areas around infected farms. Areas without transmission had a higher vegetation density and relatively shallow groundwater conditions. Vegetation and soil moisture are relevant factors in the transmission of Coxiella burnetii from infected farms to humans, by reducing the amount of dust available for dispersion of the bacteria. The findings suggest that intensive goat and sheep husbandry should be avoided in areas that are characterized by a combination of arable land with deep groundwater and little vegetation.
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http://dx.doi.org/10.1080/09603123.2011.574270DOI Listing
December 2011

Molecular epidemiology of Coxiella burnetii from ruminants in Q fever outbreak, the Netherlands.

Emerg Infect Dis 2011 Apr;17(4):668-75

Central Veterinary Institute, part of Wageningen UR, Lelystad, the Netherlands.

Q fever is a zoonosis caused by the bacterium Coxiella burnetii. One of the largest reported outbreaks of Q fever in humans occurred in the Netherlands starting in 2007; epidemiologic investigations identified small ruminants as the source. To determine the genetic background of C. burnetii in domestic ruminants responsible for the human Q fever outbreak, we genotyped 126 C. burnetii-positive samples from ruminants by using a 10-loci multilocus variable-number tandem-repeat analyses panel and compared them with internationally known genotypes. One unique genotype predominated in dairy goat herds and 1 sheep herd in the human Q fever outbreak area in the south of the Netherlands. On the basis of 4 loci, this genotype is similar to a human genotype from the Netherlands. This finding strengthens the probability that this genotype of C. burnetii is responsible for the human Q fever epidemic in the Netherlands.
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http://dx.doi.org/10.3201/eid1704.101562DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3377418PMC
April 2011

Reduction of Coxiella burnetii prevalence by vaccination of goats and sheep, The Netherlands.

Emerg Infect Dis 2011 Mar;17(3):379-86

Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.

Recently, the number of human Q fever cases in the Netherlands increased dramatically. In response to this increase, dairy goats and dairy sheep were vaccinated against Coxiella burnetii. All pregnant dairy goats and dairy sheep in herds positive for Q fever were culled. We identified the effect of vaccination on bacterial shedding by small ruminants. On the day of culling, samples of uterine fluid, vaginal mucus, and milk were obtained from 957 pregnant animals in 13 herds. Prevalence and bacterial load were reduced in vaccinated animals compared with unvaccinated animals. These effects were most pronounced in animals during their first pregnancy. Results indicate that vaccination may reduce bacterial load in the environment and human exposure to C. burnetii.
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http://dx.doi.org/10.3201/eid1703.101157DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3166012PMC
March 2011

Breeding with resistant rams leads to rapid control of classical scrapie in affected sheep flocks.

Vet Res 2011 Jan 11;42. Epub 2011 Jan 11.

Department of Epidemiology, Crisis organisation and Diagnostics, Central Veterinary Institute of Wageningen UR, P,O, Box 65, 8200 AB Lelystad, the Netherlands.

Susceptibility to scrapie, a transmissible spongiform encephalopathy in sheep, is modulated by the genetic make-up of the sheep. Scrapie control policies, based on selecting animals of resistant genotype for breeding, have recently been adopted by the Netherlands and other European countries. Here we assess the effectiveness of a breeding programme based on selecting rams of resistant genotype to obtain outbreak control in classical scrapie-affected sheep flocks under field conditions. In six commercially-run flocks following this breeding strategy, we used genotyping to monitor the genotype distribution, and tonsil biopsies and post-mortem analyses to monitor the occurrence of scrapie infection. The farmers were not informed about the monitoring results until the end of the study period of six years. We used a mathematical model of scrapie transmission to analyze the monitoring data and found that where the breeding scheme was consistently applied, outbreak control was obtained after at most four years. Our results also show that classical scrapie control can be obtained before the frequency of non-resistant animals is reduced to zero in the flock. This suggests that control at the national scale can be obtained without a loss of genetic polymorphisms from any of the sheep breeds.
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http://dx.doi.org/10.1186/1297-9716-42-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3037897PMC
January 2011

[How widespread is resistance to invermectin among gastrointestinal nematodes in sheep in The Netherlands?].

Tijdschr Diergeneeskd 2010 Nov;135(21):782-5

Centraal Veterinair Instituut van Wageningen U R, Postbus 65, 8200 AB Lelystad.

In Autumn 2009, a faecal egg count reduction test (FERCT) was carried out on three sheep farms. Groups of 8-11 lambs were treated with ivermectin or moxidectin, with a 14-day interval between treatment and sampling. Ivermectin resistance was present on all three farms. Treatment with ivermectin resulted in a reduction in faecal egg numbers of 94.6%, 63%, and 59%. On two farms, 14 days after treatment pooled faecal samples yielded predominantly larvae of Hamonchus contortus (100% and 98%, respectively). On the third farm, H. contortus and (probably) Teladorsagia circumcincta were resistant to ivermectin (64% and 36% of the larvae, respectively). Treatment with moxidectin resulted in a 100% reduction in egg output in sheep on all three farms. More sensitive culture techniques failed to detect any larvae in samples taken from two farms, but a few Ostertagia-type larvae, probably of T. circumcincta, were detected in samples from the third farm. It can be concluded that gastrointestinal nematodes in sheep from these three farms were resistant to ivermectin, whereas resistance to moxidectin was not detected.
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November 2010

The use of a geographic information system to identify a dairy goat farm as the most likely source of an urban Q-fever outbreak.

BMC Infect Dis 2010 Mar 16;10:69. Epub 2010 Mar 16.

Centre for Infectious Disease Control, National Institute for Public Health and the Environment, A van Leeuwenhoeklaan 9, PO Box 1, 3720 BA Bilthoven, the Netherlands.

Background: A Q-fever outbreak occurred in an urban area in the south of the Netherlands in May 2008. The distribution and timing of cases suggested a common source. We studied the spatial relationship between the residence locations of human cases and nearby small ruminant farms, of which one dairy goat farm had experienced abortions due to Q-fever since mid April 2008. A generic geographic information system (GIS) was used to develop a method for source detection in the still evolving major epidemic of Q-fever in the Netherlands.

Methods: All notified Q-fever cases in the area were interviewed. Postal codes of cases and of small ruminant farms (size >40 animals) located within 5 kilometres of the cluster area were geo-referenced as point locations in a GIS-model. For each farm, attack rates and relative risks were calculated for 5 concentric zones adding 1 kilometre at a time, using the 5-10 kilometres zone as reference. These data were linked to the results of veterinary investigations.

Results: Persons living within 2 kilometres of an affected dairy goat farm (>400 animals) had a much higher risk for Q-fever than those living more than 5 kilometres away (Relative risk 31.1 [95% CI 16.4-59.1]).

Conclusions: The study supported the hypothesis that a single dairy goat farm was the source of the human outbreak. GIS-based attack rate analysis is a promising tool for source detection in outbreaks of human Q-fever.
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http://dx.doi.org/10.1186/1471-2334-10-69DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2848044PMC
March 2010

[Q fever in 2008 in the Netherlands and the expectations of 2009].

Tijdschr Diergeneeskd 2009 Apr;134(7):300-3

Centraal Veterinair Instituut van Wageningen.

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April 2009

[Q fever in the Netherlands: 2008 and expectations for 2009].

Ned Tijdschr Geneeskd 2009 Apr;153(14):662-7

Rijksinstituut voor Volksgezondheid en Milieu, Centrum Infectieziektebestrijding, Bilthoven.

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April 2009

[Bluetongue virus serotype 8 in healthy young calves].

Tijdschr Diergeneeskd 2008 Dec;133(23):992-4

Gezondheidsdienst voor Dieren, Deventer.

Following the detection in Northern Ireland of bluetongue serotype-8 (BTV-8) PCR-positive calves born from PCR-negative but seropositive heifers imported from the Netherlands, an investigation was started to determine whether PCR-positive calves were born in the first quarter of 2008 in the Netherlands. Blood samples were collected on 43 dairy farms from 388 cow-calf combinations. All calves were at least 10-days-old and had been born after 1 January 2008. In total, 229 cows had had a BTV-8 infection, and from these cows 37 PCR-positive calves were born (16.2%). If these calves are viraemic, they can contribute to BTV-8 overwintering in North-West Europe.
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December 2008

A cross-sectional study to determine the seroprevalence of bluetongue virus serotype 8 in sheep and goats in 2006 and 2007 in the Netherlands.

BMC Vet Res 2008 Aug 27;4:33. Epub 2008 Aug 27.

Department of Virology, Central Veterinary Institute of Wageningen UR, Lelystad, The Netherlands.

Background: In August 2006 a major epidemic of bluetongue virus serotype 8 (BTV8) started off in North-West Europe. In the course of 2007 it became evident that BTV8 had survived the winter in North-West Europe, re-emerged and spread exponentially. Recently, the European Union decided to start vaccination against BTV8. In order to improve the understanding of the epidemiological situation, it was necessary to execute a cross-sectional serological study at the end of the BT vector season. Cattle were the target species for cross-sectional serological studies in Europe at the end of 2006 and 2007. However, there was no information on the BTV8-seroprevalence in sheep and goats.

Results: On the basis of our cross-sectional study, the estimated seroprevalence of BTV8-exposed locations in the Netherlands in 2006 was 0% for goats (95% confidence interval: 0 - 5.6%) and 7.0% for sheep (95% confidence interval: 3.5 - 12.9%). The estimated seroprevalence of BTV-8 exposed locations in 2007 was 47% for goats (95% confidence interval: 36 - 58%) and 70% for sheep (95% confidence interval: 63 - 76%). There was a wide range in within-location seroprevalence in locations with goats and sheep (1 - 100%). A gradient in seroprevalence was seen, with the highest level of seroprevalence in the southern Netherlands, the area where the epidemic started in 2006, and a decreasing seroprevalence when going in a northern direction.

Conclusion: There is a much higher estimated seroprevalence of locations with goats exposed to BTV8 than can be inferred from the rather low number of reported clinical outbreaks in goats. This is probably due to the fact that clinical signs in infected goats are far less obvious than in sheep. The wide range in within-location seroprevalence observed means that the proportion of animals protected in 2008 by a natural infection in 2006 and/or 2007 can differ highly between flocks. This should be taken into account when vaccinating animals.
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http://dx.doi.org/10.1186/1746-6148-4-33DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2531099PMC
August 2008
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