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Summary: Compartmental models have often been used to test the effectiveness and efficiency of alternative control strategies to mitigate the spread of infectious animal diseases. A fundamental principle of epidemiological modelling is that models should start as simple as possible and become as complex as needed. The simplest version of a compartmental model assumes that the population is closed, void of births and deaths and that this closed population mixes homogeneously, meaning that each infected individual has an equal probability of coming into contact with each susceptible individual in the population. However, this assumption may oversimplify field conditions, leading to conclusions about disease mitigation strategies that are suboptimal. Here, we assessed the impact of the homogeneous mixing/closed population assumption, which is commonly assumed for within‐farm models of highly contagious diseases of swine, such as foot‐and‐mouth disease (FMD), on predictions about disease spread. Incorporation of farm structure (different barns or rooms for breeding and gestation, farrowing, nursery and finishing) and demography (piglet births and deaths, and animal movement within and off of the farm) resulted in transmission dynamics that differed in the latter portion of an outbreak. Specifically, farm structure and demography, which were included in the farrow to finish and farrow to wean farms, resulted in FMD virus persistence within the population under certain conditions. Results here demonstrate the impact of incorporating farm structure and demography into models of FMD spread in swine populations and will ultimately contribute to the design and evaluation of effective disease control strategies to mitigate the impact of potential incursions. [ABSTRACT FROM AUTHOR]

Summary: Foot‐and‐mouth disease (FMD) is an important transboundary disease with substantial economic impacts. Although between‐herd transmission of the disease has been well studied, studies focusing on within‐herd transmission using farm‐level outbreak data are rare. The aim of this study was to estimate parameters associated with within‐herd transmission, host physiological factors and FMD virus (FMDV) persistence using data collected from an outbreak that occurred at a large, organized dairy farm in India. Of 1,836 regularly vaccinated, adult dairy cattle, 222 had clinical signs of FMD over a 39‐day period. Assuming homogenous mixing, a frequency‐dependent compartmental model of disease transmission was built. The transmission coefficient and basic reproductive number were estimated to be between 16.2–18.4 and 67–88, respectively. Non‐pregnant animals were more likely to manifest clinical signs of FMD as compared to pregnant cattle. Based on oropharyngeal fluid (probang) sampling and FMDV‐specific RT‐PCR, four of 36 longitudinally sampled animals (14%) were persistently infected carriers 10.5 months post‐outbreak. There was no statistical difference between subclinical and clinically infected animals in the duration of the carrier state. However, prevalence of NSP‐ELISA antibodies differed significantly between subclinical and clinically infected animals 12 months after the outbreak with 83% seroprevalence amongst clinically infected cattle compared to 69% of subclinical animals. This study further elucidates within‐herd FMD transmission dynamics during the acute‐phase and characterizes duration of FMDV persistence and seroprevalence of FMD under natural conditions in an endemic setting. [ABSTRACT FROM AUTHOR]

Social structure creates heterogeneity of interactions between individuals, thus influencing infectious disease spread. The objective of this study was to describe and characterise the social structure of free-roaming dog populations in three communities in the Torres Strait, Australia. Dogs in Kubin, Saibai, and Warraber communities were collared with GPS units that recorded locations at 15 s intervals for up to 1 week, and datasets were obtained from 24 (62% of the dog population), 23 (53%) and 21 (51%) dogs in each community, respectively. An association (potential contact) between dogs was defined as proximity within a spatio-temporal window of 5 m for 30 s. Networks were constructed for each dog population: 1. nodes were individual dogs, and 2. edges were weighted according to the duration of spatio-temporal association between pairs of dogs as a proportion of their simultaneous time monitored. Network statistics were calculated for each population and the robustness of networks to the duration of association between pairs of dogs was assessed in terms of efficiency, degree distribution and fragmentation (number of components). Dog social networks had 'small-world' structures, with characteristic clustering and low average shortest-path length between individuals. Overall, all three networks were highly connected in terms of degree distribution and global and local efficiency, but the median tie strength (2–13.5 min) was low. Centrality and the duration of association (tie-strength) between dogs were significantly different between communities. The Kubin network was least robust to fragmentation when ties of short duration were successively removed (14 components with minimum tie strength of 2 h). In contrast, the Warraber dog network was relatively robust with 7 components at minimum tie strength of 2 h as well as high local efficiency within components. We conclude that whilst infectious disease that requires a short duration of contact for transmission is likely to spread rapidly between and within clusters in all three networks in this study, fragmentation of networks ― once ties of short duration are removed ― is likely to limit spread of disease that requires a longer duration of direct contact. The network information in this study is useful as a foundation for disease spread modelling and to investigate control strategies such as movement restrictions in dog populations. [ABSTRACT FROM AUTHOR]

Summary: Foot‐and‐mouth disease (FMD) poses a significant obstacle to international trade and economic development, and for that reason, FMD prevention, control and eradication are major goals guiding animal health policy in most countries. The purpose of this study was to conduct a retrospective spatiotemporal analysis of FMD outbreaks among livestock in the Republic of Kazakhstan (RK) from 1955 to 2013. During that time, several FMD control strategies were implemented in RK, which culminated with the World Organization for Animal Health (OIE) recognition of RK as a country that is FMD‐free with partial vaccination (2015). Here, we describe and analyse the changes in spatial and temporal dynamics of FMD under different control strategies that were utilized as the country progressively moved towards eradication of the disease. A total number of 5,260 FMD outbreaks of serotype O and A (including the A22 lineage) were recorded in the cattle, pig and small ruminant populations of RK during that period. We found that outbreaks occurred in spatiotemporal clusters only prior to 1970, which is before ring vaccination around outbreaks was first employed. This finding suggests that ring vaccination substantially reduced local spread and prevented large FMD epidemics in the country. Disease incidence steadily decreased after the implementation of ring vaccination and culling of infected animals, with spatiotemporal clusters only occurring as a result of an introduction of an antigenically distinct variant of serotype A. From 1955 to 1984, FMD outbreaks demonstrated two seasonal peaks of incidence in the spring and fall. In contrast, only the peak in spring was observed between 1984 and 2013. Quantitative knowledge on how different policy and alternative control strategies contributed to RK achieving FMD‐free status could improve prospects for continued control in RK and inform control strategies in other FMD‐endemic regions. [ABSTRACT FROM AUTHOR]

Summary: The goal of this study was to characterize the properties and duration of the foot‐and‐mouth disease (FMD) carrier state and associated serological responses subsequent to vaccination and naturally occurring infection at two farms in northern India. Despite previous vaccination of cattle in these herds, clinical signs of FMD occurred in October 2013 within a subset of animals at the farms containing juvenile‐yearling heifers and steers (Farm A) and adult dairy cattle (Farm B). Subsequent to the outbreak, FMD virus (FMDV) asymptomatic carriers were identified in both herds by seroreactivity to FMDV non‐structural proteins and detection of FMDV genomic RNA in oropharyngeal fluid. Carriers’ seroreactivity and FMDV genome detection status were subsequently monitored monthly for 23 months. The mean extinction time of the carrier state was 13.1 ± 0.2 months, with extinction having occurred significantly faster amongst adult dairy cattle at Farm B compared to younger animals at Farm A. The rate of decrease in the proportion of carrier animals was calculated to be 0.07 per month. Seroprevalence against FMDV non‐structural proteins decreased over the course of the study period, but was found to increase transiently following repeated vaccinations. These data provide novel insights into viral and host factors associated with the FMDV carrier state under natural conditions. The findings reported herein may be relevant to field veterinarians and governmental regulatory entities engaged in FMD response and control measures. [ABSTRACT FROM AUTHOR]