A Tool for Prioritizing Livestock Disease Threats to Scotland.

There are a number of disease threats to the livestock of Scotland that are not presently believed to be circulating in the UK. Here, we present the development of a tool for prioritizing resources for livestock disease threats to Scotland by combining a semi-quantitative model of the chance of introduction of different diseases with a semi-quantitative model of disease impact. Eighteen key diseases were identified and then input into a model framework to produce a semi-quantitative estimate of disease priorities. We estimate this through a model of the potential impacts of the infectious diseases in Scotland that is interpreted alongside a pre-existing generic risk assessment model of the risks of incursion of the diseases. The impact estimates are based on key metrics which influence the practical impact of disease. Metrics included are the rate of spread, the disease mitigation factors, impacts on animal welfare and production, the human health risks and the impacts on wider society. These quantities were adjusted for the size of the Scottish livestock population and were weighted using published scores. Of the 18 livestock diseases included, the model identifies highly pathogenic avian influenza, foot and mouth disease in cattle and bluetongue virus in sheep as having the greatest priority in terms of the combination of chance of introduction and disease impact. Disregarding the weighting for livestock populations and comparing equally between industry sectors, the results demonstrate that Newcastle disease and highly pathogenic avian influenza generally have the greatest potential impact. This model provides valuable information for the veterinary and livestock industries in prioritizing resources in the face of many disease threats. The system can easily be adjusted as disease situations evolve.

Characterizing Livestock Markets, Primary Diseases, and Key Management Practices Along the Livestock Supply Chain in Cameroon.

Live animal markets are common hotspots for the dispersal of multiple infectious diseases in various production systems globally. In Cameroon livestock trade occurs predominantly via a system of livestock markets. Improving the understanding of the risks associated with livestock trade systems and markets is, therefore, key to design targeted and evidence-based interventions. In the current study, official transaction records for a 12-month period were collected from 62 livestock markets across Central and Southern Cameroon, in combination with a questionnaire-based survey with the livestock markets stakeholders. The available information collected at these markets was used to characterize their structural and functional organization. Based on trade volume, cattle price and the intensity of stakeholder attendance, four main classes of livestock markets were identified. Despite an evident hierarchical structure of the system, a relatively limited pool of infectious diseases was consistently reported as predominant across market classes, highlighting homogeneous disease risks along the livestock supply chain. Conversely, the variable livestock management practices reported (e.g., traded species, husbandry practices, and transhumance habits) highlighted diverse potential risks for disease dissemination among market classes. Making use of readily available commercial information at livestock markets, this study describes a rapid approach for market characterization and classification. Simultaneously, this study identifies primary diseases and management practices at risk and provides the opportunity to inform evidence-based and strategic communication, surveillance and control approaches aiming at mitigating these risks for diseases dissemination through the livestock supply chain in Cameroon.

Reproducibility of the mark-resight method to assess vaccination coverage in free-roaming dogs.

The mark-resight methodology is a widely used tool to assess both population size and vaccination coverage of free-roaming dogs. Evaluating coverage is often critical to determine the progress and impact of vaccination interventions. The aim of this study was to assess the reproducibility of the mark-resight method during a rabies vaccination campaign. A total of 90 areas in Goa, India, were surveyed on two occasions following a vaccination campaign, during which vaccinated dogs were marked. The estimated vaccination coverage for both confined and free-roaming dogs in the study area after a first round of vaccination was 68.9% (95% CI, 66.7-71.0%). The number of dogs counted in each survey, as well as the proportion of marked dogs, were the main outcomes recorded. Linear and mixed-effects models were used to evaluate the effect of survey order, surveyor, time of day, days between surveys, and weather on the outcomes between repeated surveys. Fewer dogs were likely to be counted in afternoon surveys compared to morning surveys (19.2% fewer dogs, 95%CI 7.5-31.9%) and a 17.2% (95%CI 3.6-32.7%) higher proportion of marked dogs was associated with the repeated survey compared to the first survey. Increased variation of the marked percentage between surveys was associated with using different surveyors (8.3%, 95%CI 0.4-16.2). This study demonstrated that external or personnel factors can influence the number of dogs counted and the estimated vaccination coverage of individual survey areas. Regular staff training, to ensure equal effort and quality of survey techniques between surveyors, could help standardise survey outcomes.

Incidence rates and risk factor analyses for owner reported vomiting and diarrhoea in Labrador Retrievers - findings from the Dogslife Cohort.

Dogslife collects data directly from owners of Labrador Retrievers across the UK including information regarding signs of illness irrespective of whether the signs precipitated a veterinary visit. In December 2015, the cohort comprised 6084 dogs aged up to six years and their owners had made 2687 and 2601 reports of diarrhoea and vomiting respectively. The co-occurrence of vomiting and diarrhoea with other signs was described and the frequencies and durations of the two signs were examined with reference to veterinary visitation. Age-specific illness rates were described and Cox Proportional Hazards models were used to estimate risk factors. Just 37% of diarrhoea reports were associated with a veterinary visit and the proportion was even lower for vomiting at 28%; indicating that studies of veterinary practice data miss the majority of signs of gastrointestinal upset. In terms of frequency and duration, diarrhoea typically needed to last two days before the dog would be taken to the vet but if the dog vomited at least every six hours, the owner would be more likely to take the dog to the vet after one day. The illness rates of both signs peaked when the dogs were aged between three and six months. There was also a seasonal pattern to the incidents with the lowest hazards for both in May. Diarrhoea incidents peaked in August-September each year but, while vomiting appeared to be higher in September, it peaked in February. Having another dog in the household was associated with a lower hazard for both vomiting and diarrhoea but having a cat was only associated with a reduced hazard of vomiting. In addition to the distinct seasonal patterns of reporting, there were clear differences in the geographic risks for the two signs. The hazard of diarrhoea was positively associated with human population density within Great Britain (according to home post code) whereas no significant geographical association was found with vomiting. This study is particularly relevant for dog owners because it highlights the wealth of gastrointestinal illnesses in dogs that are dealt with by owners but never seen by veterinarians. The risk factor analyses make use of owner-reported demographic information, highlighting the differences between vomiting and diarrhoea. The analyses give rise to the possibility that the presence of other pets in households may affect rates of illness and indicate new avenues for investigations of these distinct, and oft-suffered conditions.

Assessing the potential for Bluetongue virus 8 to spread and vaccination strategies in Scotland.

Europe has seen frequent outbreaks of Bluetongue (BT) disease since 2006, including an outbreak of BT virus serotype 8 in central France during 2015 that has continued to spread in Europe during 2016. Thus, assessing the potential for BTv-8 spread and determining the optimal deployment of vaccination is critical for contingency planning. We developed a spatially explicit mathematical model of BTv-8 spread in Scotland and explored the sensitivity of transmission to key disease spread parameters for which detailed empirical data is lacking. With parameters at mean values, there is little spread of BTv-8 in Scotland. However, under a "worst case" but still feasible scenario with parameters at the limits of their ranges and temperatures 1 °C warmer than the mean, we find extensive spread with 203,000 sheep infected given virus introduction to the south of Scotland between mid-May and mid-June. Strategically targeted vaccine interventions can greatly reduce BT spread. Specifically, despite BT having most clinical impact in sheep, we show that vaccination can have the greatest impact on reducing BTv infections in sheep when administered to cattle, which has implications for disease control policy.

Co-infections determine patterns of mortality in a population exposed to parasite infection.

Many individual hosts are infected with multiple parasite species, and this may increase or decrease the pathogenicity of the infections. This phenomenon is termed heterologous reactivity and is potentially an important determinant of both patterns of morbidity and mortality and of the impact of disease control measures at the population level. Using infections with Theileria parva (a tick-borne protozoan, related to Plasmodium) in indigenous African cattle [where it causes East Coast fever (ECF)] as a model system, we obtain the first quantitative estimate of the effects of heterologous reactivity for any parasitic disease. In individual calves, concurrent co-infection with less pathogenic species of Theileria resulted in an 89% reduction in mortality associated with T. parva infection. Across our study population, this corresponds to a net reduction in mortality due to ECF of greater than 40%. Using a mathematical model, we demonstrate that this degree of heterologous protection provides a unifying explanation for apparently disparate epidemiological patterns: variable disease-induced mortality rates, age-mortality profiles, weak correlations between the incidence of infection and disease (known as endemic stability), and poor efficacy of interventions that reduce exposure to multiple parasite species. These findings can be generalized to many other infectious diseases, including human malaria, and illustrate how co-infections can play a key role in determining population-level patterns of morbidity and mortality due to parasite infections.