Spread and Control of Rift Valley Fever virus after accidental introduction in the Netherlands: a modelling study.

Rift Valley Fever (RVF) is a zoonotic vector-borne infection and causes a potentially severe disease in both humans and young animals. The Ministry of Economic Affairs, Agriculture and Innovation (EL&I) is interested in the risk of an outbreak of Rift Valley Fever virus (RVFV) for the Netherlands, and more knowledge is needed about the risk of introduction of the virus, the risk of spread (transmission) of the virus in the country once introduced, and the methods for control and surveillance. For this purpose, a mathematical model was developed to study (1) the probability of a RVF outbreak at different days of introduction during the year, (2) the probability of persistence of the infection during the entire year, and (3) outbreak size and duration at different days of introduction during the year

Modelstudie surveillance rundertuberculose : epidemiologische en economische evaluatie van detectiemethoden

Rundertuberculose wordt veroorzaakt door de bacterie Mycobacterium bovis. Nederland heeft binnen de EU de officiële rundertuberculose-vrije status. Deze status wordt bewaakt met name op basis van slachthuisonderzoek. Voor het definitief aantonen van tuberculose bij runderen is het in de meeste gevallen nodig een reeks van testen uit te voeren. Met het epidemiologisch en economisch model zijn 6 verschillende detectiemethoden geëvalueerd. De uiteindelijke doelstellingen van dit project zijn: Het analyseren van de rundertuberculose-uitbraak van 1999 om daarmee inputparameters voor een epidemiologisch model te schatten. Ontwikkeling van een epidemiologisch model, bestaande uit een binnenbedrijfs-transmissie-module en een tussenbedrijfs-transmissiemodule, waarmee de detectietijd en het aantal geinfecteerde bedrijven bij detectie (inclusief de verdeling) kan worden geschat, afhankelijk van de gekozen detectiemethode. Ontwikkeling van een economisch optimalisatiemodel ter bepaling van het optimale surveillanceprogramma, op basis van surveillance- en uitbraakkosten. Dit model gebruikt de output van het epidemiologische model als inpu

Early life supply of competitive exclusion products reduces colonization of Extended Spectrum Beta-Lactamase producing Escherichia coli in broilers

Broilers are an important reservoir of ESBL/pAmpC-producing bacteria. In previous studies a single supply of a competitive exclusion (CE) product before challenge with a high dose of ESBL/pAmpC-producing E. coli led to reduced colonization, excretion and transmission, but could not prevent colonization. The hypothesized mechanism is competition; therefore in this study the effect of a prolonged supply of CE products on colonization, excretion and transmission of ESBL-producing E. coli after challenge with a low dose at day 0 or day 5 was investigated. Day-old broilers (Ross 308) (n=220) were housed in isolators. Two CE products, containing unselected fermented intestinal bacteria (CEP) or a selection of pre- and probiotics (SYN), were supplied in drinking water from day 0 to 14. At day 0 or day 5 broilers were challenged with 0.5 mL with 101 or 102 cfu/mL E. coli encoding the beta–lactamase gene blaCTX-M-1 on an IncI plasmid (CTX-M-1-E. coli). Presence and concentration of CTX-M-1-E. coli was determined using cloacal swabs (day 0-14, 16, 19, 21) and cecal content (day 21). Cox proportional hazard model and a mixed linear regression model were used to determine the effect of the intervention on colonization and excretion (log10 cfu/g). When challenged at day of hatch, no effect of CEP was observed. When challenged at day 5, both CEP and SYN led to a prevention of colonization with CTX-M-1-E. coli in some isolators. In the remaining isolators, we observed reduced time until colonization (HR between 3.71 ×10-3 and 3.11), excretion (up to -1.60 log10 cfu/g) and cecal content (up to -2.80 log10 cfu/g) and a 1.5 to 3-fold reduction in transmission rate. Colonization after a low dose challenge with ESBL-producing E. coli can be prevented by CE products. However, if at least one bird is colonized it spreads through the whole flock. Prolonged supply of CE products provided shortly after hatch, may be applicable as an intervention to reduce prevalence of ESBL/pAmpC-producing bacteria in the broiler production chain

Hoe een modelleur een mug vangt - het nut van wiskundige modellen voor het bestuderen en bestrijden van vector-overgedragen ziekten

Vector-overgedragen ziekten zijn infectieziekten die worden overgedragen door vectoren, meestal anthropoden, zoals muggen, knutten en teken. De laatste jaren is de aandacht voor deze ziekten toegenomen. Aanleidingen hiervoor zijn bijvoorbeeld de uitbraak van het West-Nijlvirus in Noord-Amerika, de recente blauwtong-epidemie in Nederland en omringende landen en de uitbraak van chikungunya in Italië

Quantitative analysis of the probability of introducing equine encephalosis virus (EEV) into The Netherlands

Equine encephalosis is a midge-borne viral disease of equines caused by equine encephalosis virus (EEV, Orbivirus, Reoviridae), and closely related to African horse sickness virus (AHSV). EEV and AHSV share common vectors and show similar transmission patterns. Until now EEV has caused outbreaks in Africa and Israel. This study aimed to provide insight in the probability of an EEV outbreak in The Netherlands caused by infected vectors or hosts, the contribution of potential source areas (risk regions) to this probability, and the effectiveness of preventive measures (sanitary regimes). A stochastic risk model constructed for risk assessment of AHSV introduction was adapted to EEV. Source areas were categorized in risk regions (high, low, and very low risk) based on EEV history and the presence of competent vectors. Two possible EEV introduction pathways were considered: importation of infected equines and importation of infected vectors along with their vertebrate hosts. The probability of EEV introduction (PEEV) was calculated by combining the probability of EEV release by either pathway and the probability of EEV establishment. The median current annual probability of EEV introduction by an infected equine was estimated at 0.012 (90% uncertainty interval 0.002–0.020), and by an infected vector at 4.0 10−5 (90% uncertainty interval 5.3 10−6–2.0 10−4). Equines from high risk regions contributed most to the probability of EEV introduction with 74% on the EEV introduction by equines, whereas low and very low risk regions contributed 18% and 8%, respectively. International movements of horses participating in equestrian events contributed most to the probability of EEV introduction by equines from high risk regions (86%), but also contributed substantially for low and very low risk regions with 47% and 56%. The probability of introducing EEV into The Netherlands is much higher than the probability of introducing AHSV with equines from high risk countries contributing most. The introduction by an infected equine is the most likely pathway. Control measures before exportation of equines showed to have a strong mitigating effect on the probability of EEV introduction. The risk of EEV outbreaks should be taken into account when altering these import regulations