Bioclimatic and anthropogenic variables shape the occurrence of Batrachochytrium dendrobatidis over a large latitudinal gradient

AbstractAmphibian chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), has caused the greatest known loss of biodiversity due to an infectious disease. We used Bd infection data from quantitative real-time PCR (qPCR) assays of amphibian skin swabs collected across Chile during 2008–2018 to model Bd occurrence with the aim to determine bioclimatic and anthropogenic variables associated with Bd infection. Also, we used Bd presence/absence records to identify geographical Bd high-risk areas and compare Bd prevalence and infection loads between amphibian families, ecoregions, and host ecology. Data comprised 4155 Bd-specific qPCR assays from 162 locations across a latitudinal gradient of 3700 km (18º to 51ºS). Results showed a significant clustering of Bd associated with urban centres and anthropogenically highly disturbed ecosystems in central-south Chile. Both Bd prevalence and Bd infection loads were higher in aquatic than terrestrial amphibian species. Our model indicated positive associations of Bd prevalence with altitude, temperature, precipitation and human-modified landscapes. Also, we found that macroscale drivers, such as land use change and climate, shape the occurrence of Bd at the landscape level. Our study provides with new evidence that can improve the effectiveness of strategies to mitigate biodiversity loss due to amphibian chytridiomycosis.</jats:p

The consequences of reservoir host eradication on disease epidemiology in animal communities.

Non-native species have often been linked with introduction of novel pathogens that spill over into native communities, and the amplification of the prevalence of native parasites. In the case of introduced generalist pathogens, their disease epidemiology in the extant communities remains poorly understood. Here, Sphaerothecum destruens, a generalist fungal-like fish pathogen with bi-modal transmission (direct and environmental) was used to characterise the biological drivers responsible for disease emergence in temperate fish communities. A range of biotic factors relating to both the pathogen and the surrounding host communities were used in a novel susceptible-exposed-infectious-recovered (SEIR) model to test how these factors affected disease epidemiology. These included: (i) pathogen prevalence in an introduced reservoir host (Pseudorasbora parva); (ii) the impact of reservoir host eradication and its timing and (iii) the density of potential hosts in surrounding communities and their connectedness. These were modelled across 23 combinations and indicated that the spill-over of pathogen propagules via environmental transmission resulted in rapid establishment in adjacent fish communities (<1 year). Although disease dynamics were initially driven by environmental transmission in these communities, once sufficient numbers of native hosts were infected, the disease dynamics were driven by intra-species transmission. Subsequent eradication of the introduced host, irrespective of its timing (after one, two or three years), had limited impact on the long-term disease dynamics among local fish communities. These outputs reinforced the importance of rapid detection and eradication of non-native species, in particular when such species are identified as healthy reservoirs of a generalist pathogen

Exploring genetic resistance to infectious salmon anaemia virus in Atlantic salmon by genome-wide association and RNA sequencing

Funding The authors gratefully acknowledge funding from BBSRC (BB/R008612/1, BB/R008973/1), in addition to BBSRC Institute Strategic Programme Grants to the Roslin Institute (BB/P013759/1 and BB/P013740/1).Peer reviewedPublisher PD

Controlling emerging infectious diseases in salmon aquaculture

In this paper, the authors review the impacts of diseases facing salmon aquaculture, drawing lessons from terrestrial animal diseases. They discuss the implementation of current control strategies, taking into account transmission patterns (vertical versus horizontal), disease reservoirs, and interactions with wild fish. In addition, the decision-making context of aquatic disease control and the institutional organisation of control strategies are considered, with particular emphasis on the roles and responsibilities of regulatory authorities and the private sector. Case studies on the emergence and control of infectious salmon anaemia worldwide and pancreas disease in Norway are used to examine some of the controversies that may influence decision making and provide lessons for the future

Controlling emerging infectious diseases in salmon aquaculture

In this paper, the authors review the impacts of diseases facing salmon aquaculture, drawing lessons from terrestrial animal diseases. They discuss the implementation of current control strategies, taking into account transmission patterns (vertical versus horizontal), disease reservoirs, and interactions with wild fish. In addition, the decision-making context of aquatic disease control and the institutional organisation of control strategies are considered, with particular emphasis on the roles and responsibilities of regulatory authorities and the private sector. Case studies on the emergence and control of infectious salmon anaemia worldwide and pancreas disease in Norway are used to examine some of the controversies that may influence decision making and provide lessons for the future

Veterinary epidemiology: Forging a path toward one health

The One Health concept has been extensively used to describe those practices that support transdisciplinary collaborations involving animal and human health and the environment. During the past International Society of Veterinary Epidemiology and Economics (ISVEE) conference in Merida (Mexico) in November 2015, a panel discussion was held to identify gaps and needs required for success with such approaches. Key messages included further development of dynamic, transdisciplinary collaborations, new mechanisms for obtaining, integrating and interpreting data from diverse sources, the identification of One Health joint priorities and resources for the veterinary and public health professions, and operationalization and institutionalization of One Health. Additionally, all abstracts that were presented at ISVEE containing the term "One Health" were identified. There has been an increase in the use of the term over time. One Health research has been presented at ISVEE since at least as early as 2009 and has been highlighted at the conference for work carried out in at least 41 countries from 69 research centers or institutions, with highly diversified articles, which reveals the richness of this field of research

Within-farm spread of infectious salmon anemia virus (ISAV) in Atlantic salmon Salmo salar farms in Chile

Spread of infectious salmon anemia virus (ISAV) at the cage level was quantified using a subset of data from 23 Atlantic salmon Salmo salar farms located in southern Chile. Data collected from official surveillance activities were systematically organized to obtain detailed information on infectious salmon anemia (ISA) outbreaks. Descriptive statistics for outbreak duration, proportion of infected fish, and time to secondary infection were calculated to quantify the magnitude of ISAV incursions. Linear and multiple failure time (MFT) regression models were used to determine factors associated with the cage-level reproduction number (Rc) and hazard rate (HR) for recurrent events, respectively. In addition, the Knox test was used to assess if cage-to-cage transmissions were clustered in space and time. Findings suggest that within farms, ISA outbreaks, on average, lasted 30 wk (median = 26 wk, 95% CI = 24 to 37 wk) and affected 57.3% (95% CI = 47.7 to 67.0%) of susceptible cages. The median time to secondarily diagnosed cages was 23 d. Occurrence of clinical ISAV outbreaks was significantly associated with increased Rc, whereas increased HR was significantly associated with clinical outbreaks and with a large number of fish. Spatio-temporal analysis failed to identify clustering of cage cases, suggesting that within-farm ISAV spread is independent of the spatial location of the cages. Results presented here will help to better understand ISAV transmission, to improve the design of surveillance programs in Chile and other regions in which salmon are intensively farmed, and to examine the economic impact of ISAV and related management strategies on various cost and demand shifting factors

Determination of presence of Tritrichomonas foetus in uterine lavages from cows with reproductive problems Determinação da presença de Tritrichomonas foetus em lavados uterinos de vacas com problemas reprodutivos

The aim of this study was to determine the presence of Tritrichomonasfoetus in two dairy herds on the Altiplano Cundiboyacense. Twenty-one low-volume uterine lavages from cows with a history of reproductive problems in two dairy herds located in the municipality of Sibaté (Cundinamarca) and Ventaquemada (Boyacá) were evaluated. In the first herd, 10 cows were sampled and in the second, 11 cows, based on three inclusion criteria. The uterine lavages were obtained through infusion of physiological saline solution into the uterine body. The samples were centrifuged and seeded in Tritrichomonas basal medium for 10-15 days at 37 ºC. The protozoa were evaluated on the day of sampling and 10 and 15 days after incubation by means of direct viewing under a dark-field microscope. Positive samples were stained with Wright and Lugol to identify the morphological characteristics. This study showed that T. foetus was present in 61.8% of the animals sampled. The determination that T. foetus was present in 61.8% of the samples analyzed is a significant finding given that in the herds evaluated, this agent had not previously been diagnosed.<br>O objetivo do presente estudo, foi determinar a presença de Tritrichomonas foetus em dois rebanhos leiteiros no Altiplano Cundiboyacense. De vacas com um histórico de problemas reprodutivos, foram avaliados 21 lavados uterinos de pequeno volume, em dois rebanhos leiteiros localizados nos municípios de Sibaté (Cundinamarca) e Ventaquemada (Boyacá). No primeiro rebanho, 10 vacas foram amostradas e no segundo 11, baseado em três critérios de inclusão. Os lavados uterinos foram obtidos mediante infusão de solução salina fisiológica no corpo do útero. As amostras foram centrifugadas e semeadas em meio de cultura básico para Tritrichomonas por 10-15 dias a 37 ºC. Os protozoários foram avaliados no dia da colheita de amostras e 10 e 15 dias após incubação por meio de visualização direta sob um microscópio de campo escuro. As amostras positivas foram coradas com Wright e Lugol para identificar as características morfológicas. Este estudo mostrou que T. foetus estava presente em 61,8% dos animais amostrados. A determinação de que T. foetus estava presente em 61,8% das amostras analisadas é um achado significativo, dado que nos rebanhos avaliados, esse agente não tinha sido previamente diagnosticado