Modelling the lethargic crab disease

The lethargic crab disease (LCD) is an emergent infirmity that has decimated native populations of the mangrove land crab (Ucides cordatus, Decapoda: Ocypodidae) along the Brazilian coast. Several potential etiological agents have been linked with LCD, but only in 2005 was it proved that it is caused by an ascomycete fungus. This is the first attempt to develop a mathematical model to describe the epidemiological dynamics of LCD. The model presents four possible scenarios, namely, the trivial equilibrium, the disease-free equilibrium, endemic equilibrium, and limit cycles arising from a Hopf bifurcation. The threshold values depend on the basic reproductive number of crabs and fungi, and on the infection rate. These scenarios depend on both the biological assumptions and the temporal evolution of the disease. Numerical simulations corroborate the analytical results and illustrate the different temporal dynamics of the crab and fungus populations.     

Histopathology of the mangrove land crab Ucides cordatus (Ocypodidae) affected by lethargic crab disease

Lethargic crab disease (LCD) has caused extensive epizootic mortality of the mangrove land crab Ucides cordatus (Linnaeus 1763) (Brachyura: Ocypodidae) along the Brazilian coast. Direct culture of tissue samples from sick crabs and subsequent isolation and purification identified the causative agent as an Exophiala species of fungus. The histopathology of crabs with variable signs of LCD indicates that the most affected tissues are the epidermis, connective tissue, heart, hepatopancreas, nervous system, and gills. Gonads, somatic muscles, and digestive system are less affected by the fungus. The observed pathology is compatible with the clinical signs of LCD. Necrosis, tissue degeneration, and congestion of hemal sinuses and vessels are present in heavily infected organs. Nerve fibers may be compressed by accumulations of yeast-like cells. In heavy infections the tissue of gill lamellae is destroyed with subsequent dilation or compression. Cellular immune responses include hemocytic infiltration, agglutination and encapsulation, and phagocytosis. Phagocytosis of yeast-like cells is abundant in the connective tissue associated with the exoskeleton. These results indicate that LCD is the result of a systemic phaeohyphomycosis caused by a species of Exophiala. The present study also suggests that dispersal of the fungus within the crab occurs through the hemal system.     

Specific primers for the detection of the black-yeast fungus associated with lethargic crab disease (LCD)

Lethargic crab disease (LCD) is an emerging infirmity that has been causing extensive mortalities in populations of the mangrove land crab Ucides cordatus (Ocypodidae) along the Atlantic coast of Brazil. Previous studies have indicated that LCD is associated with a dematiaceous fungus, Exophiala cancerae de Hoog et al. In the present study, we sequenced the internal transcribed spacer (ITS) of the rDNA region of this black yeast species and developed species-specific PCR primers. Sensitivity tests indicated that the developed protocol is capable of detecting very small amounts of target DNA. Also, the application of the protocol to a variety of other dematiaceous fungi did not generate any false positives. The specific primers provided in the present study represent an important tool for rapidly surveying a large number of crab individuals, as well as environmental samples. Such knowledge will be instrumental in understanding the epidemiological dynamics of LCD.     

Modelling the dynamics of invasion and control of competing green crab genotypes

Establishment of invasive species is a worldwide problem. In many jurisdictions, management strategies are being developed in an attempt to reduce the environmental and economic harm these species may cause in the receiving ecosystem. Scientific studies to improve understanding of the mechanisms behind invasive species population growth and spread are key components in the development of control methods. The work presented herein is motivated by the case of the European green crab (Carcinus maenas L.), a remarkably adaptable organism that has invaded marine coastal waters around the globe. Two genotypes of European green crab have independently invaded the Atlantic coast of Canada. One genotype invaded the mid-Atlantic coast of the USA by 1817, subsequently spreading northward through New England and reaching Atlantic Canada by 1951. A second genotype, originating from the northern limit of the green crabs European range, invaded the Atlantic coast of Nova Scotia in the 1980s and is spreading southward from the Canadian Maritime provinces. We developed an integrodifference equation model for green crab population growth, competition and spread, and demonstrate that it yields appropriate spread rates for the two genotypes, based on historical data. Analysis of our model indicates that while harvesting efforts have the benefit of reducing green crab density and slowing the spread rate of the two genotypes, elimination of the green crab is virtually impossible with harvesting alone. Accordingly, a green crab fishery would be sustainable. We also demonstrate that with harvesting and restocking, the competitive imbalance between the Northern and Southern green crab genotypes can be reversed. That is, a competitively inferior species can be used to control a competitively superior one.     

Modelling the biological invasion of Carcinus maenas (the European green crab)

This paper proposes a system of integro-difference equations to model the spread of Carcinus maenas, commonly called the European green crab, that causes severe damage to coastal ecosystems. A model with juvenile and adult classes is first studied. Here, standard theory of monotone operators for integro-difference equations can be applied and yields explicit formulas for the asymptotic spreading speeds of the juvenile and adult crabs. A second model including an infected class is considered by introducing a castrating parasite Sacculina carcini as a biological control agent. The dynamics are complicated and simulations reveal the occurrence of periodic solutions and stacked fronts. In this case, only conjectures can be made for the asymptotic spreading speeds because of the lack of mathematical theory for non-monotone operators. This paper also emphasizes the need for mathematical studies of non-monotone operators in heterogeneous environments and the existence of stacked front solutions in biological invasion models.     

Modelling torque generation by the mero-carpopodite joint of the american lobster and the snow crab

The torque generated by a rotating joint comprises the useful force exerted by the joint on the external environment, and both the magnitude and distribution of torque through the step cycle during walking are important variables in understanding the mechanics of walking. The mechanics of the American lobster (Homarus americanus) and snow crab (Chionoecetes opilio) during walking were modelled to examine the relative roles of flexor versus extensor apodeme-muscle complexes, investigate which legs of these decapods likely contribute the greatest to locomotion, determine scaling effects of torque generation, and assess the relative roles of various model variables on torque production. Force generated along the length of the apodeme by the muscle was modelled based on apodeme surface area, muscle stress, and muscle fibre pinnation angle. Torque was then calculated from this estimated force and the corresponding moment arm. The flexor apodeme-muscle complex is calculated to generate consistently greater forces than the extensor, and generally this results in flexor torque being larger than extensor, though the snow crab does illustrate the opposite in two of its legs. This greater torque generation in flexion suggests that, in addition to the pushing of the trailing legs, the pulling action of the leading legs may play a significant role, at least during lateral walking. Leg 4 of both species appears to generate greater torques and thus provide the greatest forces for locomotion. Torque generation as a function of body size shows a second order response due to the increase in apodeme surface area. The pinnation angle of the muscle fibre is found to be insignificant in force generation, apodeme surface area (representing muscle cross sectional area) likely plays the most influential role in total force production, and moment arm controls the distribution of this force through the step cycle. Muscle stress remain a largely unknown quantity however, and may significantly affect both magnitude and distribution through step cycle of forces, and thus torque. Despite the uncertainty associated with the muscle stress parameter, the modelled results fit well with previously published force measurements.     

Gas-bubble disease in the blue crab, Callinectes sapidus.

Exposure of crabs to water supersaturated with air resulted in formation of gas emboli in the hemal system, which in turn caused localized ischemia. More than one-third of the exposed crabs died during the 2 days following the episode. In surviving crabs, the most severely affected organs and tissues were the gills, heart, and antennal gland. Especially in gills, emboli were still present in apparently healthy crabs 35 days following exposure to water supersaturated with air. Evidence of ischemic injury was focal in character except in the antennal gland, where the epithelium of the labyrinth was sometimes extensively degenerate. Repair processes apparently did not involve hemocytes except for occasional fibroblastic infiltration in damaged gill lamellae.     

Modelling infectious disease to support human health

During the current COVID-19 pandemic, there has been renewed scientific and public focus on understanding the pathogenesis of infectious diseases and investigating vaccines and therapies to combat them. In addition to the tragic toll of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), we also recognize increased threats from antibiotic-resistant bacterial strains, the effects of climate change on the prevalence and spread of human pathogens, and the recalcitrance of other infectious diseases – including tuberculosis, malaria, human immunodeficiency virus (HIV) and fungal infections – that continue to cause millions of deaths annually. Large amounts of funding have rightly been redirected toward vaccine development and clinical trials for COVID-19, but we must continue to pursue fundamental and translational research on other pathogens and host immunity. Now more than ever, we need to support the next generation of researchers to develop and utilize models of infectious disease that serve as engines of discovery, innovation and therapy.

Summary: This Editorial considers how knowledge from animal and other models of infectious disease can impact our understanding of human biology and potential therapies, focusing largely on zebrafish. It also highlights ways in which DMM is supporting these areas.

As an Editor at Disease Models & Mechanisms (DMM) and an academic researcher using zebrafish as a model to study tuberculosis, it is especially exciting to read and publish research in zebrafish to obtain, in a whole, live vertebrate, insights into infectious diseases and therapies (Box 1). Indeed, zebrafish provide a remarkable vertebrate model for many questions related to infectious disease. Embryos and larvae are optically transparent, enabling microscopy of both pathogen and host that would be more challenging or cumbersome in other systems (Fig. 1). Knock-in of fluorescent tags at endogenous loci allows direct and detailed in vivo visualization of the host immune response (Cronan et al., 2018). Both forward and reverse genetic approaches for understanding infection are straightforward and are buttressed by the high-throughput capabilities of this model, in which a single tank of adult zebrafish can produce hundreds of embryos per week. Furthermore, chemical biology screens and interventions using intact, living animals are uniquely accessible to researchers, as zebrafish larvae and embryos are permeable to diverse small molecules and fit within a single well of 96-well and 384-well plates (Patton et al., 2021). Open in a separate windowFig. 1.Zebrafish larva infected with fluorescent Mycobacterium abscessus expressing TdTomato, shown in red. Image courtesy of Matt Johansen (Johansen et al., 2021).Box 1. DMM highlights zebrafish advancing knowledge in infectious diseaseRecent publications in DMM show the potential of the zebrafish model system to provide new or fuller insights into infectious diseases and therapies. One question being addressed is how basic cell-autonomous immune processes function in the context of a full organism. Various Reviews have highlighted what we have learned about the role of pyroptosis in host defence against bacterial infections (Brokatzky and Mostowy, 2022), as well as advances in understanding the diverse roles that macrophages and neutrophils play during the initial response to a variety of infectious and inflammatory stimuli (Rosowski, 2020). Zebrafish can also provide models for parasitic diseases that are relatively neglected, and we were pleased to publish a zebrafish model that provides insight into Toxoplasma pathogenesis, particularly the in vivo interactions of Toxoplasma with macrophages (Yoshida et al., 2020). Research dissecting the role of host immune cells in pathogen responses can be further potentiated by new tools, such as those developed by the Lieschke laboratory using macrophage and neutrophil-specific Cas9 driver lines to allow cell-specific genetic perturbation (Isiaku et al., 2021).Non-tuberculous mycobacteria causing pulmonary disease are a growing threat worldwide, with an antibiotic resistance profile that makes them very difficult to treat (Stout et al., 2016; Vinnard et al., 2016). An exploration of phage therapy for non-tuberculous mycobacteria in the zebrafish provides new insights into exciting clinical work that bookends this publication (Johansen et al., 2021). Engineered bacteriophages targeting specific strains of Mycobacterium abscessus have now been used clinically in cases of advanced lung disease (Dedrick et al., 2019; Nick et al., 2022). In other work, Habjan et al. employed the zebrafish mycobacterial infection model as an early screening step for anti-tuberculosis hits from in vitro screens that might have the best chance for in vivo translation. Following up on a screen for novel in vitro activity against Mycobacterium tuberculosis that identified ∼240 compounds, they identified 14 compounds with good in vivo activity. Impressively, they went on to identify the target of the strongest in vivo hit as being a mycobacterial aspartyl-tRNA synthase through screening for resistant mutants in both Mycobacterium marinum and Mycobacterium tuberculosis (Habjan et al., 2021).Drug screens, like those discussed above, are possible due to the permeability of the zebrafish to small molecules, which also allows creative ways to control the induction of host cytokines. DMM published an approach that enables drug-inducible, tissue-specific, titratable expression of different cytokines (Ibrahim et al., 2020). Harnessing this permeability in zebrafish can also enable detailed exploration of the effects of drugs, such as broadly used glucocorticoids, on specific innate immune cell types (Xie et al., 2019).The zebrafish has also been used as a model to understand infectious disease therapies targeting the pathogen directly. A recent paper describes the in vivo efficacy of nanoparticle-based delivery of lipophilic antibiotics, as well as use of the zebrafish to screen different formulations (Knudsen Dal et al., 2022). Finally, in the adult zebrafish sphere, a recent Review focused on how zebrafish can inform vaccine development strategies (Saralahti et al., 2020).These recent publications highlight some of the strengths of the zebrafish model for infectious disease research. DMM aims to be at the forefront in encouraging scientists and clinicians to leverage these insights for future therapies.Although efforts in zebrafish are often recognized and valued within the model organism community and beyond, it can sometimes be hard to break through to the world of clinical research. I vividly remember the excitement of being invited to present my work as a starting assistant professor at an early-career researcher lunch with a prominent visiting scientist, only to have my research and plans dismissed with some variation of “Well, why don''t you try to figure out what''s actually going on in people?”.Indeed, this is what many zebrafish researchers are ultimately trying to do by a different route. The goal of harnessing the knowledge we generate in models to impact human biology and therapies is an important part of the scientific enterprise. Many of us want and expect our findings to be relevant beyond the context of a model system. In my field, it has been exciting to see work in the zebrafish emerge that has led to the discovery of fundamentally conserved features of tuberculosis and host immunity – from zebrafish to humans – and has since translated to ongoing clinical trials.However, although we might hope that our work will be inherently understood and utilized in the clinical context, maximizing the potential of this research requires community advocates and communicators to help place the work in context. This can be achieved through ongoing dialogue among researchers, clinicians and patients to understand medical needs and perspectives. For example, DMM and The Company of Biologists have been long-time supporters of societies, such as the Zebrafish Disease Models Society, which focuses on the translational potential of zebrafish for understanding human disease and for developing new therapies, including some being investigated in clinical trials.Thus, it is useful to consider the following three broad themes when using model organisms in infectious disease research:

1. Conserved host–pathogen interactions in model systems. Although we all recognize, even at a strictly visual level, the many differences between the biology of a model organism and human biology, there is fundamentally conserved biology to be explored. Immune signalling pathways and underlying principles, as well as molecular and cellular details, first discovered and dissected in worms, flies, fish, mice and other model organisms, have translated remarkably well to human biology in many cases.
2. Model diversity. Divergent biology – in addition to being fascinating and important for the sake of knowledge itself – also leads to vital new insights and therapeutic approaches. As just one example, bacteriophages were instrumental in the discovery of fundamental aspects of gene regulation, have been used to facilitate genetic manipulation of seemingly genetically intractable pathogens, and are now being engineered and deployed therapeutically. And the study of bacterial–bacteriophage interactions of course led to all the advances made possible by CRISPR. These and many other examples from models that diverge from humans all support open-mindedness in science and emphasize the strength of laboratories taking diverse approaches and using diverse models. Pressing questions and opportunities in this realm are many, including investigation of how some non-human immune systems – those of bats, as just one example – permit asymptomatic tolerance of viruses that may be pathogenic in humans (Hayman, 2019). Which animal species restrict human pathogens via immune mechanisms that might eventually be harnessed therapeutically? Some of these topics will be prominent in a 2023 meeting organized by DMM entitled ‘Infectious Diseases Through an Evolutionary Lens’, which will take place in London at the British Medical Association House (Fig. 2).Open in a separate windowFig. 2.DMM''s 2023 meeting is entitled ‘Infectious Diseases Through an Evolutionary Lens’ and will take place in London at the British Medical Association House. Register your interest here: https://www.biologists.com/infectious-diseases-through-an-evolutionary-lens-contact-form/.
3. Engineering preclinical and predictive models of infectious disease. With advances in gene editing and the ability to make specific base edits, it is possible to precisely model human variants in an in vivo context during infection. Organisms like the zebrafish can provide useful models to delve into the specific consequences of these variants. Orthogonal approaches include mammalian animal models and advanced human cell models (Leist et al., 2020; van der Vaart et al., 2021). Discussion between scientists doing this preclinical work and clinical collaborators will be needed to determine to what degree the model recapitulates human disease and how these models can be used to advance new therapies. Recently, we have seen some of the landscape for clinical trials change, and in public health emergencies, collaborations would ideally accelerate the time from discovery to clinic. Again, this will require dialogue with and buy-in from clinical researchers to put together rigorous clinical trials.

DMM seeks to create and contribute to the ongoing conversations among and between basic scientists, clinical researchers and clinicians, with insights and criticisms from each of these domains. By highlighting rigorous, high-quality science in these areas, we hope to contribute to improved understanding of infectious diseases and new approaches to treatment.     

Modelling congenital transmission of Chagas’ disease

The successful elimination of vectorial and transfusional transmission of Chagas’ disease from some countries is a result of the reduction of domestic density of the primary vector Triatoma infestans, of almost 100% of coverage in blood serological selection and to the fact that the basic reproductive number of Chagas’ disease is very close to one (1.25). Therefore, congenital transmission is currently the only way of acquiring Chagas’ Disease in such regions. In this paper we propose a model of congenital transmission of Chagas’ disease. Its aim is to provide an estimation of the time period it will take to eliminate this form of transmission in regions where vetorial transmission was reduced to close to zero, like in Brazil.     

The invasive green crab and Japanese shore crab: behavioral interactions with a native crab species,the blue crab

Blue crabs, Callinectes sapidus (Rathbun), are an ecologically and commercially important species along the East coast of North America. Over the past century and a half, blue crabs have been exposed to an expanding set of exotic species, a few of which are potential competitors. To test for interactions with invasive crabs, juvenile C. sapidus males were placed in competition experiments for a food item with two common non-indigenous crabs, the green crab Carcinus maenas (L.) and the Japanese shore crab, Hemigrapsus sanguineus (De Haan). Agonistic interactions were evaluated when they occurred. In addition, each species’ potential to resist predators was examined by testing carapace strength. Results showed that C. maenas was a superior competitor to both C. sapidus and H. sanguineus for obtaining food, while the latter two species were evenly matched against each other. Regarding agonism, C. sapidus, was the “loser” a disproportionate number of times. C. sapidus carapaces also had a significantly lower breaking strength. These experiments suggest that both as a competitor, and as potential prey, juvenile blue crabs have some disadvantages compared with these common sympatric exotic crab species, and in areas where these exotics are common, juvenile native blue crabs may be forced to expend more energy in conflict that could be spent foraging, and may be forced away from prime food items toward less optimum prey.     

Modelling the initial spread of foot-and-mouth disease through animal movements

Livestock movements in Great Britain (GB) are well recorded and are a unique record of the network of connections among livestock-holding locations. These connections can be critical for disease spread, as in the 2001 epidemic of foot-and-mouth disease (FMD) in the UK. Here, the movement data are used to construct an individual-farm-based model of the initial spread of FMD in GB and determine the susceptibility of the GB livestock industry to future outbreaks under the current legislative requirements. Transmission through movements is modelled, with additional local spread unrelated to the known movements. Simulations show that movements can result in a large nationwide epidemic, but only if cattle are heavily involved, or the epidemic occurs in late summer or early autumn. Inclusion of random local spread can considerably increase epidemic size, but has only a small impact on the spatial extent of the disease. There is a geographical bias in the epidemic size reached, with larger epidemics originating in Scotland and the north of England than elsewhere.     

Lethargic crab disease: multidisciplinary evidence supports a mycotic etiology

Although lethargic crab disease (LCD) is causing massive mortalities in populations of the mangrove crab Ucides cordatus of Northeastern Brazil, the identity of its etiological agent was hitherto unknown. In this study we provide robust evidence suggesting that LCD is caused by an anamorph Ascomycota (Fungi). We examined specimens of U. cordatus collected from stocks affected by LCD. Histological and TEM methods detected the presence of hyphae, conidia, and condiophores in several host tissues. Moreover, the abundance of fungal stages is negatively associated with crab health. Finally, DNA was isolated from the fungus and a region of its 18S ribosomal gene was sequenced Phylogenetic analyses not only confirm the diagnosis of the LCD fungus in crab tissues as an ascomycete, but also suggest a close relationship with members of the subphylum Pezizomycotina.     

Modelling the effect of a booster vaccination on disease epidemiology

Despite the effectiveness of vaccines in dramatically decreasing the number of new infectious cases and severity of illnesses, imperfect vaccines may not completely prevent infection. This is because the immunity afforded by these vaccines is not complete and may wane with time, leading to resurgence and epidemic outbreaks notwithstanding high levels of primary vaccination. To prevent an endemic spread of disease, and achieve eradication, several countries have introduced booster vaccination programs. The question of whether this strategy could eventually provide the conditions for global eradication is addressed here by developing a seasonally-forced mathematical model. The analysis of the model provides the threshold condition for disease control in terms of four major parameters: coverage of the primary vaccine; efficacy of the vaccine; waning rate; and the rate of booster administration. The results show that if the vaccine provides only temporary immunity, then the infection typically cannot be eradicated by a single vaccination episode. Furthermore, having a booster program does not necessarily guarantee the control of a disease, though the level of epidemicity may be reduced. In addition, these findings strongly suggest that the high coverage of primary vaccination remains crucial to the success of a booster strategy. Simulations using estimated parameters for measles illustrate model predictions. This work was supported in part by the Natural Sciences and Engineering Research Council of Canada (NSERC). One of the authors (P.R.) acknowledges the support of the Ellison Medical Foundation.     

Modelling within-host spatiotemporal dynamics of invasive bacterial disease

Mechanistic determinants of bacterial growth, death, and spread within mammalian hosts cannot be fully resolved studying a single bacterial population. They are also currently poorly understood. Here, we report on the application of sophisticated experimental approaches to map spatiotemporal population dynamics of bacteria during an infection. We analyzed heterogeneous traits of simultaneous infections with tagged Salmonella enterica populations (wild-type isogenic tagged strains [WITS]) in wild-type and gene-targeted mice. WITS are phenotypically identical but can be distinguished and enumerated by quantitative PCR, making it possible, using probabilistic models, to estimate bacterial death rate based on the disappearance of strains through time. This multidisciplinary approach allowed us to establish the timing, relative occurrence, and immune control of key infection parameters in a true host–pathogen combination. Our analyses support a model in which shortly after infection, concomitant death and rapid bacterial replication lead to the establishment of independent bacterial subpopulations in different organs, a process controlled by host antimicrobial mechanisms. Later, decreased microbial mortality leads to an exponential increase in the number of bacteria that spread locally, with subsequent mixing of bacteria between organs via bacteraemia and further stochastic selection. This approach provides us with an unprecedented outlook on the pathogenesis of S. enterica infections, illustrating the complex spatial and stochastic effects that drive an infectious disease. The application of the novel method that we present in appropriate and diverse host–pathogen combinations, together with modelling of the data that result, will facilitate a comprehensive view of the spatial and stochastic nature of within-host dynamics.     

Hydrophobic proteins which bind cholinergic agonists from brains of lethargic mutant mice

An investigation of hydrophobic proteins of synaptosomes isolated from the CNS tissue of the lethargic mutant mouse, which exhibits a behavioral epilepsy as the major visible effect of the mutant gene (lh), has revealed that the binding affinity of these proteolipid components for acetylcholine was higher than that observed in control (+/+) animals, a finding that may be directly related to the behavioral epilepsy.Submitted in partial fulfillment of the requirements for the Ph.D. degree.     

Modelling the developmental origins of health and disease in the early embryo

The concept that certain adult diseases, such as hypertension, type 2 diabetes and dyslipidaemia can originate from events occurring in utero arose from epidemiological studies in humans but has since been supported by numerous animal-based studies. Referred to as the "developmental origins of health and disease" or "DOHaD" hypothesis, nutritional studies to date have largely focused on two experimental paradigms involving either calorie or protein restriction for varying intervals during pregnancy, where the favoured animal models have been the sheep and rat. In recent times, attention has been directed towards the earliest stages of gestation, where there is emerging evidence to indicate that the pre-implantation embryo may be particularly sensitive to environmentally induced perturbations leading to impaired health in adulthood. In this article, we make the case for hESCs as a model of the human pre-implantation embryo. Working with comparatively large populations of embryonic cells from the species of clinical interest, the scope exists to investigate the effects of specific genetic manipulations or combinations of metabolites against contrasting genetic backgrounds, where the consequences can be evaluated in downstream tissue specific progenitor and/or terminally differentiated cells. In order to fully realize these potentials, however, both derivation and culture conditions need to be harmonized and refined so as to preclude the requirement for feeder cells and serum.     

Modelling the effect of urbanization on the transmission of an infectious disease

This paper models the impact of urbanization on infectious disease transmission by integrating a CA land use development model, population projection matrix model and CA epidemic model in S-Plus. The innovative feature of this model lies in both its explicit treatment of spatial land use development, demographic changes, infectious disease transmission and their combination in a dynamic, stochastic model. Heuristically-defined transition rules in cellular automata (CA) were used to capture the processes of both land use development with urban sprawl and infectious disease transmission. A population surface model and dwelling distribution surface were used to bridge the gap between urbanization and infectious disease transmission. A case study is presented involving modelling influenza transmission in Southampton, a dynamically evolving city in the UK. The simulation results for Southampton over a 30-year period show that the pattern of the average number of infection cases per day can depend on land use and demographic changes. The modelling framework presents a useful tool that may be of use in planning applications.