Infected Farms Research Articles

Emergence and Selection of a Highly Pathogenic Avian Influenza H7N3 Virus.

Low-pathogenicity avian influenza (LPAI) viruses of subtypes H5 and H7 have the ability to spontaneously mutate to highly pathogenic (HPAI) virus variants, causing high mortality in poultry. The highly pathogenic phenotype is caused by mutation of the hemagglutinin (HA) cleavage site, but additional mutations may play a role. Evidence from the field for the switch to high pathogenicity remains scarce. This study provides direct evidence for LPAI-to-HPAI virus mutation during H7N3 infection of a turkey farm in the Netherlands. No severe clinical symptoms were reported at the farm, but deep sequencing of isolates from the infected turkeys revealed a minority of HPAI virus sequences (0.06%) in the virus population. The HPAI virus contained a 12-nucleotide insertion in the HA cleavage site that was likely introduced by a single event as no intermediates with shorter inserts were identified. This suggests nonhomologous recombination as the mechanism of insertion. Analysis of different organs of the infected turkeys showed the largest amount of HPAI virus in the lung (4.4%). The HPAI virus was rapidly selected in experimentally infected chickens after both intravenous and intranasal/intratracheal inoculation with a mixed virus preparation. Full-genome sequencing revealed that both pathotypes contained a deletion in the stalk region of the neuraminidase protein. We identified additional mutations in HA and polymerase basic protein 1 (PB1) in the HPAI virus, which were already present as minority variants in the LPAI virus population. Our findings provide more insight into the molecular changes and mechanisms involved in the emergence and selection of HPAI viruses.IMPORTANCE Low-pathogenicity avian influenza (LPAI) viruses circulate in wild birds and can be transmitted to poultry. LPAI viruses can mutate to become highly pathogenic avian influenza (HPAI) viruses causing severe disease and death in poultry. Little is known about this switch to high pathogenicity. We isolated an LPAI H7N3 virus from an infected turkey farm and showed that this contains small amounts of HPAI virus. The HPAI virus rapidly outcompeted the LPAI virus in chickens that were experimentally infected with this mixture of viruses. We analyzed the genome sequences of the LPAI and HPAI viruses and identified several changes that may be important for a virus to become highly pathogenic. This knowledge may be used for timely identification of LPAI viruses that pose a risk of becoming highly pathogenic in the field.

Polymerase chain reaction for detection of some highly dangerous viral fish disease agents

Today viral fish diseases cause major losses in the world aquaculture. Pathogen spread often occurs during the transportation of fish from infected farms to the disease-free ones. Therefore, the import of fish stocking material to Russia from countries with a different epidemic situation requires risk-based monitoring and forecasting. Diagnostics is of primary importance in the complex of measures to prevent the spread of viral infections in fish. To date, laboratory diagnostics of viral fish diseases is based on pathogen isolation and its identification using serological methods which require a lot of time and are performed only in large research institutes with specialized laboratories. Molecular diagnostic methods are more sensitive and high-performance. The article presents the results of using reverse transcription polymerase chain reaction to detect a number of highly dangerous viral diseases of fish (Salmonidae). As a result of this work, primers were selected and the temperature and time conditions of the reaction were optimized for the identification of infectious hematopoietic necrosis, viral hemorrhagic septicemia and infectious salmon anemia. The results obtained during the research allowed us to establish that this diagnostic method is highly specific with analytical sensitivity to infectious salmon anemia virus of 2.5 lg TCD50/сm3, to infectious hematopoietic necrosis – 2.9 lg TCD50/сm3 and to viral hemorrhagic septicemia – 4.2 lg TCD50/ сm3. The described method was used to identify reference and field strains available at the FGBI ARRIAH Reference Laboratory for Aquaculture Diseases and isolated in different years in fish farms in the territory of the Russian Federation. The research data correlated with the results obtained from virus neutralization in cell culture and ELISA performed using commercial kits. The proposed method of RT-PCR allows to detect pathogens both in fish with pronounced clinical signs and in latent virus carriers.

Spatial transmission risk during the 2007-2010 Q fever epidemic in The Netherlands: Analysis of the farm-to-farm and farm-to-resident transmission.

Between 2007 and 2010 a Q fever epidemic in Dutch dairy goat farms caused a large Q fever outbreak in human residents in the southern part of the Netherlands. Here we characterize the transmission of Coxiella burnetii, the aetiological agent of Q fever, between infected and susceptible dairy goat farms by estimating a spatial transmission kernel. In addition, we characterize the zoonotic transmission of C. burnetii by estimating the spatial kernel for transmission from infected farms to neighbouring residents. Whereas the range of between-farm transmission is comparable to the scale of the Netherlands, likely due to long-range between-farm contacts such as animal transport, the transmission risk from farms to humans is more localized, although still extending to 10 km and beyond. Within a range of about 10 km, the transmission risk from an infected goat farm to a single resident is of the same order of magnitude as the farm-to-farm transmission risk per animal in a receiving farm. We illustrate how, based on the estimated kernels, spatial patterns of transmission risks between farms and from farms to residents can be calculated and visualized by means of risk maps, offering further insight relevant to policy making in a one-health context.

Comparative evaluation of fluorescence polarization assay and competitive ELISA for the diagnosis of bovine brucellosis vis-a-vis sero-monitoring

Brucellosis is an important zoonosis that constitutes a serious public health hazard which is caused by a bacterium belonging to the genus Brucella. In the present study, two highly specific serological tests for brucellosis diagnosis, fluorescence polarization assay (FPA) and competitive ELISA (cELISA) were standardized in the laboratory, evaluated and compared with rose bengal plate test (RBPT), indirect ELISA (iELISA) and commercial cELISA kit. For test evaluation, 1386 serum samples [apparently healthy animals (n = 260), samples from Brucella infected farms (n = 701) and B. abortus S19 vaccinated animals (n = 425)] were analyzed to assess suitable diagnostic test in B. abortus S19 post vaccinated bovine population. In apparently healthy brucellosis free farms, RBPT, iELISA, in-house FPA and cELISA were found to be highly specific than commercial cELISA. Commercial cELISA kit was comparatively more sensitive than other serological tests in samples collected from infected farms. The FPA showed sensitivity nearly equal to RBPT and in-house cELISA showed greater sensitivity than RBPT in infected farms. In animals with persistent vaccinal antibodies, only in-house FPA and cELISA recorded higher specificity of 87.64 and 90.27%, respectively. The other tests, RBPT and iELISA displayed similar reactivity with vaccine antibodies to that of infection antibodies whereas commercial cELISA kit showed an intermediate specificity of 47.69%. With these findings, RBPT, iELISA and cELISA are suggested for screening infected herds, and in-house developed FPA and cELISA tests with a proven specificity can be used for confirmatory diagnosis of brucellosis in B. abortus S19 post vaccinated animal populations.

Proximity and density of neighboring farms and water supply, as risk factors for bacteriosis: A case study of spatial risk analysis in tilapia and rainbow trout farms of Oaxaca, Mexico

In this work, we conducted a spatial analysis of three types of diseases: bacteriosis, trichodiniasis and girodactylosis in 336 tilapia and rainbow trout farms during a three-years-period. In order to identify and characterize spatial risk associated with exposure via water for each disease, we used the incidence of cases per type of water supply during the study period (R0), the reciprocal of distance to farms into the same water supply (R1), the inverse distance to farms with an epidemiological background into the same water supply (R2), the reciprocal of distance with an epidemiological background into the same water supply by their prevalence and incidence indexes (R3), and the reciprocal of distance to nearest wastewater domestic discharges that could affect the farm's water supply (R4). For this, through binomial linear multiple regression by generalized linear models (GLM), geographically weighted regression (GWR), logistic multiple regression by generalized additive models (GAM) and Partial Least Squares Path Modeling (PLS-PM); several models were tested to find the best fit to analyze the relationship between the prevalence and incidence index as the outcome variable and the calculated risk factors, as explicative variables. Consequently, the best models were utilized to construct risk maps with predicted relative risks values, employing interpolation methods such as ordinary Kriging and Inverse Distance Weighted Interpolation (IDW). As a result, an ANOVA of the residuals and fitted values from all models showed that the logistic binomial model GAM was the best to analyze all farms globally. The latter allowed predicting in a better way risk zones of bacteriosis in the cases presented during in the next year after the study period; that is to say that was more important to consider the nearness to an infected farm than its prevalence and incidence indexes in its epidemiological background of bacteriosis cases. From there, we found that bacteriosis cases were mainly affected by two of the five risks: the reciprocal of the distance to farms into the same water supply (R1) and the reciprocal of the distance to farms with an epidemiological background into the same water supply (R2). Also, these risk factors were used to estimate the relative risk and establish risk zones, using risk maps in tilapia and rainbow trout farms, whose water supply were lake and river. Finally, the cases of trichodiniasis and gyrodactylosis did not show a relationship to the five risks; accordingly, they could be associated with other not included risks in this work, such as the movement of organisms.

Infectious Salmon Anemia and Farm-Level Culling Strategies.

Infectious salmon anemia (ISA) is an infectious disease, and outbreaks must be handled to avoid spread between salmon sea farms. Intensive culling at infected farms is an important biosecurity measure to avoid further spread but is also a costly intervention that farmers try to avoid. A lack of action, however, may lead to new outbreaks in nearby salmon sea farms, with severe impacts on both economy and animal welfare. Here, we aim to explore how a time delay between a detected outbreak and the culling of both infected cages and entire farms affects the further spread of the disease. We use a previously published model to calculate how many salmon sea farms were directly infected in each outbreak. To investigate the effect of culling on the further spread of disease, we use the number of months elapsed from the detected outbreak to (a) the first cage being depopulated, and (b) to the entire salmon sea farm being depopulated as predictors of how many new farms the virus was transmitted to, after controlling for contact between the farms. We show that the lapse in time before the first cage is depopulated correlates positively with how many new salmon sea farms are infected, indicating that infected cages should be culled with as little time delay as possible. The model does not have sufficient power to separate between culling of only cages assumed to be infected and the entire farm, and, consequently, provides no direct empirical evidence for the latter. Lack of evidence is not evidence, however, and we argue that a high probability of spread between cages in infected salmon sea farms still supports the depopulation of entire farms as the safest option.

Campylobacter hepaticus, the Cause of Spotty Liver Disease in Chickens: Transmission and Routes of Infection.

The epidemiology of Spotty Liver Disease (SLD) was investigated by assaying 1,840 samples collected from layer chickens and the environment in poultry farms across Australia for the presence of Campylobacter hepaticus, the agent responsible SLD in chickens. A C. hepaticus specific PCR and bacterial culture were used. Results showed that birds could be infected with C. hepaticus up to 8 weeks before clinical SLD was manifested. In addition, birds could be infected long before laying starts, as young as 12 weeks old, but the peak period for SLD outbreaks was when the birds were 26–27 weeks old. Campylobacter hepaticus DNA was detected in motile organisms such as wild birds and rats and so these organisms may be vectors for C. hepaticus dissemination. Moreover, water, soil, mites, flies, and dust samples from SLD infected farms were also found to be PCR-positive for C. hepaticus DNA. However, it still remains to be determined whether these environmental sources carry any viable C. hepaticus. The indications from this study are that environmental sources are a likely transmission source of C. hepaticus. Therefore, biosecurity practices need to be strictly followed to prevent the spread of SLD amongst and between flocks. Also, a rapid, molecular detection method such as PCR should be used as to monitor for C. hepaticus presence in flocks before clinical disease is apparent, and therefore inform the use of biosecurity and therapeutic measures to help prevent SLD outbreaks.

Nipah shell disorder, modes of infection, and virulence

The Nipah Virus (NiV) was first isolated during a 1998–9 outbreak in Malaysia. The outbreak initially infected farm pigs and then moved to humans from pigs with a case-fatality rate (CFR) of about 40%. After 2001, regular outbreaks occurred with higher CFRs (~71%, 2001–5, ~93%, 2008–12). The spread arose from drinking virus-laden palm date sap and human-to-human transmission. Intrinsic disorder analysis revealed strong correlation between the percentage of disorder in the N protein and CFR (Regression: r2 = 0.93, p < 0.01, ANOVA: p < 0.01). Distinct disorder and, therefore, genetic differences can be found in all three group of strains. The fact that the transmission modes of the Malaysia strain are different from those of the Bangladesh strains suggests that the correlations may also be linked to the modes of viral transmission. Analysis of the NiV and related viruses suggests links between modes of transmission and disorder of not just the N protein but, also, of M shell protein. The links among shell disorder, transmission modes, and virulence suggest mechanisms by which viruses are attenuated as they passed through different cell hosts from different animal species. These have implications for development of vaccines and epidemiological molecular analytical tools to contain outbreaks.

Cell-mediated and humoral immune profile to hydatidosis among naturally infected farm animals.

Background and Aim:Cystic echinococcosis (CE) is a widespread parasitic disease caused by Echinococcus granulosus tapeworm infect different intermediate hosts including sheep, cattle, and camels. The intermediate host’s immune response to the hydatid cyst is still conflict and complex. The current study was designed to evaluate the immune response in sera of hydatid naturally infected sheep, cattle, and camels in the form of features of inflammatory cell infiltrations, levels of Th1 and Th2 cytokines, besides the humoral specific immunoglobulin G (IgG) responses.Materials and Methods:Thirty-nine sheep, 74 cattle, and 79 camels’ sera were collected and considered as CE naturally infected and ten samples from each species were graded as non-infected. Lung specimens were collected for histopathological examination. The quantitative concentrations of tumor necrosis factor-α, interleukin (IL)-6, IL-4, and IL-10 were determined. Different antigens were prepared from hydatid cyst; hydatid cyst fluid of lung origin hydatid cyst fluid of liver origin, hydatid cyst protoscoleces of lung origin (HCP-g), hydatid cyst protoscoleces of liver origin, hydatid cyst germinal layer of lung origin, and hydatid cyst germinal layer of liver origin; and characterized by gel electrophoresis and Western blotting analysis. The total specific IgG level against E. granulosus infection was measured using an indirect enzyme-linked immunosorbent assay.Results:The results indicated that the cellular immune response in the infected tissues was characterized by inflammatory cell penetration. The pro-inflammatory Th1 cytokine profile was predominant in infected animals in comparison with non-infected ones. However, the humoral immune response was seen as a high level of IgG in infected animals. The presented data approved that the HCP-g antigen could be considered as a delegate antigen for all other prepared antigens with an immunoreactive band at molecular weights 32 kDa.Conclusion:This study provides a fundamental insight into the events that manipulate cellular and humoral immune profiles in an intermediate host; sheep, cattle, and camel that naturally infected with CE. Hence, it was concluded that CE is a constant disease and confirm the reactivity Th1 in combating hydatid cyst. Besides, it could lead to the activation of the humoral immune response in the form of a high level of IgG.

African swine fever in China: a new twist to an emerging crisis

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Epizootic characteristics of rabies and rabies assistance in the territory of the Kirov region in the years 2010-2018.

One of the negative consequences of an increase in the incidence of animal rabies is the increased risk of human infection. study of the main manifestations of rabies epizootic and the status of anti-rabies care in the Kirov region in 2010-2018. Reporting forms of monitoring the situation of rabies FBHI "Center for Hygiene and Epidemiology in the Kirov Region" for 2010-2018 were statistically processed and studied. Since 2014, increase in the incidence of rabies among animals and expansion of the boundaries of the range have been revealed. Rabies is recorded among foxes (67%), raccoon dogs (up to 40%), domestic and farm animals. Every year in Kirov region over 4 thousand people get injured from animals: dogs (76%) and cats (20%). Damage is often localized on the lower extremities (34%) and was the most dangerous on the head, neck, face, hands (29%). In average of 3,500 victims are sent to immunization. An inverse correlation dependence between preventive oral immunization of wild animals and contacts of people with rabid animals was revealed. A high percentage of refusals from vaccination (up to 31%) is associated with low sanitary literacy of the population. The problem of rabies is relevant for the Kirov region. An increase of the proportion of infected domestic and farm animals leads to an increase the risk of human disease. In order to stabilize rabies epizootic, it is necessary to carry out the whole complex of prophylactic measures.

Estimation of infection risk on pig farms in infected wild boar areas—Epidemiological analysis for the reemergence of classical swine fever in Japan in 2018

In September 2018, classical swine fever (CSF) reemerged in Japan after 26 years’ absence. The first case was detected at a pig farm in Gifu Prefecture, in the center of Japan, and the disease spread to both domestic pigs and wild boar (Sus scrofa). The spread of CSF in wild boar is extremely difficult to control and is thus a great threat to domestic pig farms, and understanding the transmission risk from wild boar to domestic pigs is essential to implement effective control measures that will prevent domestic pig infection. Therefore, this study elucidates the transmission risk from wild boar to domestic pigs by introducing a transmission kernel that is dependent on the distance between infected wild boar and pig farms, and then estimating the risk area of infection from wild boar by describing the transmission probability. The study used epidemiological data from Gifu Prefecture in the period from September 2018 to March 2019, including a total of 171 1-km grid cells where an infected wild boar was detected and pig farm data from 13 infected and 34 uninfected farms. The estimated infection risk area within 28 days matched well with the observed data. The risk area widened gradually during the epidemic, and at the end of March, the risk area extended over a range of approximately 75 km from east to west and 40 km from north to south (almost 3000 km2). Ten out of the 13 infected farms and four out of the 34 uninfected farms were located within the high-risk area (>60 % infection probability). In contrast, one infected farm and 18 uninfected farms were located within the low-risk area (<5 % infection probability). When several infected grid cells were detected within 5 km of a pig farm, the risk of infection from wild boar within 28 days was more than 5 %. This analysis provides an estimate of the potential spatial range over which CSF virus can spread between wild boar and domestic pig farms, and can be used to inform the early detection of CSF-suspected pigs and the strengthening of biosecurity measures that will effectively prevent and control the disease based on the infection risk level.

Neospora caninum, A potential cause of reproductive failure in dairy cows from Northern Greece.

Neospora caninum infection has been reported in a large number of intermediate hosts, such as ruminants, rabbits, mice, etc. but neosporosis has emerged as a serious disease in cattle and dogs worldwide. Abortions and other infertility issues have been reported in the infected cows, leading to great economic losses in farmers. The aim of our study was to assess N. caninum seroprevalence in dairy cattle from Northern Greece (region of Xanthi) by using the indirect fluorescent antibody technique. Blood samples were collected from 875 Holstein – Friesian dairy cows and tested for Neospora caninum antibodies. Among the cows that were studied, 184 (21.03%) were positive for N. caninum antibodies and concurrently their farms had a known previous history of infertility problems, such as abortions, increased number of artificial inseminations needed for conception, increased rate of returning to estrus and retention of fetal membranes.

Assessment of Human Immunodeficiency Virus (HIV) and Acquired Immunodeficiency Syndrome (AIDS) Vulnerability Index and Its Effect on Labour Productivity of Rural Farmers in Cross River State, Nigeria

The research assessed the HIV/AIDS vulnerability index effects on rural labour productivity of agricultural communities in Cross River State. Using multistage random sampling techniques on infected and non-infected farm households, 308 respondents were sampled and structured questionnaires were administered by trained enumerators with adequate experience in the state. Data were analysed using the fussy set approach to health risk vulnerability, descriptive and correlation analysis to determine vulnerability index, productive labour force and relationship between vulnerability index and productivity of both infected and non-infected rural farmers. The average labour force (18 years and above) for infected households was approximately 3 persons per household as against 4 persons for non-infected farm households. The mean labour productivity for infected farmers was 6715 ton/man day while, the non-infected farmer was 8285 ton/man day, where the difference in productivity was significant. A vulnerability index of 16% was established and the indicators that contributed significantly were; care not to take unscreened blood, care not to touch blood of others, having sex indiscriminately, sharing clipper, reduction in savings, and reduction in number of working hours. Furthermore, 43.97% of infected households and 20.40% of the pooled farmers were found to be highly vulnerable. Also an inverse relationship between labour productivity and vulnerability index was established and data were statistically significant. The researcher recommends special inputs subsidy programme for infected farmers, institutionalization of the HIV/AIDS (public health) desk in the State and federal Ministries of Agriculture and Rural Development.

Molecular Identification of Vibrio alginolyticus Causing Vibriosis in Shrimp and Its Herbal Remedy.

Penaeus monodon is highly susceptible to vibriosis disease. Aims of the study were to identify the pathogen causing vibriosis in P. monodon through molecular techniques and develop a biocontrol method of the disease by application of herbal extracts. Shrimp samples were collected aseptically from the infected farm and the bacteria were isolated from the infected region of those samples. Based on phenotypic identification, several isolates were identified as Vibrio sp. 16S rRNA gene sequences of the selected isolates exhibited 100% homology with V. alginolyticus strain ATCC 17749. An in vivo infection challenge test was performed by immersion method with V. alginolyticus where these isolates caused high mortality in juvenile shrimp with prominent symptoms of hepatopancreatic necrosis. Antibiogram profile of the isolates was determined against eleven commercial antibiotic discs whereas the isolates were found resistant to multiple antibiotics. A total of twenty-one herbal extracts were screened where Emblica officinalis, Allium sativum, and Syzygium aromaticum strongly inhibited the growth of V. alginolyticus in in vitro conditions. In in vivo conditions, the ethyl acetate extracts of E. officinalis and A. sativum successfully controlled the vibriosis disease in shrimp at a dose of 10 mg/g feed. This is the first report on molecular identification and biocontrol of V. alginolyticus in shrimp in Bangladesh.

수온변화에 따른 해수내 VHSV(Viral Hemorrhagic Septicemia Virus)의 생존능 분석

Viral hemorrhagic septicemia (VHS) is a serious viral disease that infects the olive flounder in South Korea. The Korean aquaculture industry experienced an economic loss caused by the high infectivity and mortality. Wastewater is a factor in transferring infections to wild and cultured fish in waters near infected aquaculture farms. In this study, we analyzed the stability of the VHS virus in sterilized seawater depending on the water temperature. The VHS virus maintained infectivity for 8 days and was detected using quantitative polymerase chain reaction after 10 days of inoculation to sterilized seawater at low temperatures. On the other hand, at high temperatures, the virus maintained infectivity for 4 days and was detected for 7 days. These results may contribute to basic data for epidemiological studies.

Game theory of vaccination and depopulation for managing livestock diseases and zoonoses on small-scale farms

Livestock producers adapt their farm management to epidemiological risks in different ways, through veterinary interventions but also by modulating their farm size and the removal rate of animals. The objective of this theoretical study was to elucidate how these behavioral adaptations may affect the epidemiology of highly-pathogenic avian influenza in domestic poultry and the outcome of the implemented control policies. We studied a symmetric population game where the players are broiler poultry farmers at risk of infection and where the between-farms disease transmission is both environmental and mediated by poultry trade. Three types of farmer behaviors were modelled: vaccination, depopulation, and cessation of poultry farming. We found that the transmission level of the disease through trade networks has strong qualitative effects on the system's epidemiological-economic equilibria. In the case of low trade-based transmission, when the monetary cost of infection is high, depopulation behavior can maintain a stable disease-free equilibrium. In addition, vaccination behavior can lead to eradication by private incentives alone – an outcome not seen for human diseases. In a scenario of high trade-based transmission, depopulation behavior has perverse epidemiological effects as it accelerates the spread of disease via poultry trade. In this situation, state interventions should focus on making vaccination technologies available at a low price rather than penalizing infected farms.

Relationships between Coxiella burnetii antibody serology and daily -GPS measured- active mobility in the Netherlands

PDS 75: Microbiome, infections and respiratory effects, Johan Friso Foyer, Floor 1, August 27, 2019, 1:30 PM - 3:00 PM Background/aim: From 2007 through 2010 the Netherlands experienced the largest recorded Q-fever outbreak to date. People living close to goat farms that reported an abortion storm (AS+) were identified as having higher risk to have Q-fever compared to persons living further away. Active mobility close to infected farms may have contributed to exposure to Coxiella burnetii, but no mobility data was available during the outbreak. During 2014-2016 we performed mobility measurements in the outbreak region using week-long Global Position System (GPS) tracking. The main goal of this study was to investigate whether daily active mobility near previously Q-fever positive farms (AS+ or bulk tank milk-positive (BM+)) was related to positive Q-fever serology in humans. Methods: From a cohort of 2494 participants we collected 941 GPS tracks. People were indicated as exposed when they entered specific distances around AS+ or BM+ farms: <500m, 500-1000m, 1000-2000m, 2000-4000m. We evaluated if only mobility in proximity to AS+, BM+ or negative goat farms influenced the risk of being Q-fever serology positive using logistic regression. We adjusted for a range of potential confounders and residential exposure, therefore mobility and living >4000m of a positive farm was grouped as unexposed. Results: Active mobility near AS+ farms translated to increased risks for positive Q-fever serology 1000-2000m: OR 5.7 (1.5-21.9), 2000m-4000m: OR 2.7 (1.2-6.0). Mobility near BM+ farms did not increase risks; maximum OR was 1.2 (0.5-2.8). We found a marginally increased risk for active mobility near negative farms, but this was not statistically significant OR 2.1 (0.4-10.5). Conclusions: Active mobility near AS+ goat farms represented an increased risk for positive Q-fever serology in study participants, BM+ and negative goat farms did not add significantly to Q-fever serology risk. If a C.burnetii related abortion storm occurs on a goat farm, active mobility near that farm should be restricted.

How could an African swine fever outbreak evolve in an enzootic context? The case of Imerintsiatosika, Madagascar in 2015.

African swine fever (ASF) is a haemorrhagic contagious pig disease generally causing high mortality. ASF is enzootic in Madagascar with outbreaks reported each year. An ASF outbreak occurred in May 2015 in the municipality of Imerintsiatosika in Madagascar. We investigated the outbreak to describe it and to identify risk factors in order to propose control measures, and to document evidence of an ASF outbreak in an enzootic country. We took biological samples from very sick and dying pigs, sold by the farmer to the butcher, for PCR analysis. An active search for all possible farm-cases was carried out. A definition of suspected farm-case was established and we implemented a descriptive survey and a retrospective cohort study. Laboratory results confirmed ASF virus infection. Suspected farm-cases represented 81 farms out of 922. Out of 3081 pigs of infected farms, 44% (95% CI: 42–46%) were sick, of which 47% were sold or slaughtered. Case fatality was 60% (95% CI: 56–63%) while 21% (95% CI: 19–24%) of the diseased pigs recovered. The outbreak duration was nine months and half of the infected farms’ pig population remained after the outbreak. Compared to the exotic breed, local pigs had twice the risk of infection. It is the first detailed report of an ASF outbreak in an enzootic situation. The disease still has a large impact with 50% animals lost. However, the case fatality is lower than expected that suggests the possibility of resistance and subclinical cases. Proximity to road and increased number of farms are risk factors so biosecurity measures are needed. Further studies are needed to understand why pigs of local breed are more affected. Finally, an acceptable alternative to the sale of sick animals should be found as this currently is the breeders’ means to reducing economic loss.

The Role of Movement Restrictions in Limiting the Economic Impact of Livestock Infections.

Movements are essential for the economic success of the livestock industry. These movements however bring the risk of long-range spread of infection, potentially bringing infection to previously disease-free areas where subsequent localised transmission can be devastating. Mechanistic predictive models usually consider controls that minimize the number of livestock affected without considering other costs of an ongoing epidemic. However, it is more appropriate to consider the economic burden, as movement restrictions have major consequences for the economic revenue of farms. Using mechanistic models of foot-and-mouth disease (FMD), bluetongue virus (BTV) and bovine tuberculosis (bTB) in the UK, we contrast the economically optimal control strategies for these diseases. We show that for FMD, the optimal strategy is to ban movements in a small radius around infected farms; the balance between disease control and maintaining ‘business as usual’ varies between regions. For BTV and bTB, we find that the cost of any movement ban is more than the epidemiological benefits due to the low within-farm prevalence and slow rate of disease spread. This work suggests that movement controls need to be carefully matched to the epidemiological and economic consequences of the disease, and optimal movement bans are often far shorter than existing policy.