Economic losses due to foot-and-mouth disease (FMD) in Ethiopian cattle.

Ethiopia's cattle population is among the largest in Africa and is burdened by frequent foot-and-mouth disease (FMD) outbreaks. FMD is caused by several distinct and highly contagious viral strains that can result in acute disease in cattle, causing losses in productivity and impeding international trade. This economic simulation study considered four main sources of losses due to FMD in cattle: reduced milk yield, draft power yield, fertility, and increased mortality. Economic losses were estimated per case across age-sex strata in 89 Ethiopian administrative zones for the years 2010-2021 using a wide range of data to estimate distributions for 30 input variables in a series of Monte Carlo simulations. It was estimated that an average case of FMD in Ethiopian cattle results in losses (mean values reported followed 95 % confidence intervals in brackets) of US dollars (USD) 11 (USD 7-USD 16) per case. Losses resulting from an average outbreak were estimated to be USD 2300 (USD 1400-USD 3300), while national annual losses were estimated to be USD 0.9 Mil. (USD 0.2 Mil.-USD 2.3 Mil.). Per cow-year, based on a national cow population of approximately 39 Mil. head, these estimated annual losses are equivalent to losses of only USD 0.02 (USD 0.01-USD 0.06). Nationally, these losses were significantly less than previously estimated in the literature, with currently estimated losses more accurately reflecting the economic burden of FMD in Ethiopian cattle over the past decade. The relatively small estimated losses suggest that control efforts based on widespread vaccination in countries with primarily extensive cattle production systems, such as Ethiopia, are unlikely to be economically sound. Sensitivity analyses suggested losses would be far greater in intensive systems, and that certainty surrounding incidence rates is paramount to the formulation of economically sound animal healthpolicy in regions with endemic FMD.

Global Burden of Animal Diseases: a novel approach to understanding and managing disease in livestock and aquaculture.

Investments in animal health and Veterinary Services can have a measurable impact on the health of people and the environment. These investments require a baseline metric that describes the burden of animal health and welfare in order to justify and prioritise resource allocation and from which to measure the impact of interventions. This paper is part of a process of scientific enquiry in which problems are identified and solutions sought in an inclusive way. It poses the broad question: what should a system to measure the animal disease burden on society look like and what value would it add? Moreover, it aims to do this in such a way as to be accessible by a wide audience, who are encouraged to engage in this debate. Given that farmed animals, including those raised by poor smallholders, are an economic entity, this system should be based on economic principles. These poor farmers are negatively impacted by disparities in animal health technology, which can be addressed through a mixture of supply-led and demand-driven interventions, reinforcing the relevance of targeted financial support from government and non-governmental organisations. The Global Burden of Animal Diseases (GBADs) Programme will glean existing data to measure animal health losses within carefully characterised production systems. Consistent and transparent attribution of animal health losses will enable meaningful comparisons of the animal disease burden to be made between diseases, production systems and countries, and will show how it is apportioned by people's socio-economic status and gender. The GBADs Programme will produce a cloud-based knowledge engine and data portal, through which users will access burden metrics and associated visualisations, support for decisionmaking in the form of future animal health scenarios, and the outputs of wider economic modelling. The vision of GBADs, strengthening the food system for the benefit of society and the environment, is an example of One Health thinking in action.

Les investissements réalisés en santé animale et dans les Services vétérinaires ont un impact mesurable sur la santé des personnes et de l'environnement. Le système de mesure appliqué à ces investissements doit reposer sur un référentiel de base décrivant l'impact de la santé et du bien-être animal de manière à justifier et classer par priorités les ressources allouées et à mesurer les effets des interventions. Les auteurs présentent une étude conduite dans le cadre d'une enquête scientifique destinée à identifier les problèmes et à rechercher des solutions de manière inclusive. L'étude pose la question de savoir à quoi devrait ressembler un système conçu pour mesurer l'impact sur la société des maladies animales, et quelle serait sa valeur ajoutée. En outre, l'étude est conduite de manière à être accessible à une large audience afin d'encourager cette dernière à participer aux discussions. Étant donné que les animaux d'élevage constituent une entité économique, y compris les animaux appartenant à des éleveurs pauvres, le système de mesure doit reposer sur des principes économiques. Les exploitants pratiquant une agriculture de subsistance subissent les effets négatifs des disparités entre les différentes technologies applicables à la santé animale, disparités auxquelles il est possible de remédier par le biais d'interventions associant des mesures dictées par l'offre et par la demande et en renforçant l'efficacité du soutien financier ciblé apporté par les organisations gouvernementales et non gouvernementales. Le Programme « L'impact mondial des maladies animales ¼ (GBADs) aura pour tâche de glaner les données existantes afin de mesurer les pertes associées à la santé animale au sein de systèmes de production qui auront été soigneusement caractérisés au préalable. Grâce à l'élucidation cohérente et transparente des pertes imputables à chaque problème de santé animale, des comparaisons pertinentes pourront être effectuées concernant l'impact des maladies animales par maladies, par systèmes de production et par pays, et la répartition de cet impact dans les populations concernées suivant le statut socio-économique et le genre des intéressés sera mieux comprise. Le Programme GBADs entend créer un moteur de recherche et un portail de données qui seront disponibles sur le Cloud et donneront aux utilisateurs l'accès à des outils de mesure de l'impact des maladies et à d'autres informations présentées sous forme graphique, ainsi qu'à des outils d'aide à la décision sous forme de scénarios prospectifs sur la santé animale et aux résultats d'études plus larges de modélisation économique. La vision du GBADs, renforcer le système de production de denrées alimentaires au profit de la société et de l'environnement, est un exemple de mise en oeuvre du concept Une seule santé.

Las inversiones en sanidad animal y en los Servicios Veterinarios pueden tener un efecto mensurable en la salud de las personas y el medio ambiente. Para efectuar estas inversiones se precisan parámetros que describan y cuantifiquen la situación de partida y el impacto de los problemas de sanidad y bienestar animales, a fin de poder, a partir de ahí, justificar y jerarquizar la asignación de recursos y medir los efectos de las intervenciones. Este artículo, inscrito en un proceso de indagación científica encaminado a detectar problemas y buscar soluciones de forma incluyente, plantea la cuestión general de cómo debería ser y qué valor añadido aportaría un sistema destinado a medir el impacto que imponen a la sociedad las enfermedades animales. Los autores, además, tratan de exponer la cuestión de manera que sea accesible a un público amplio, al que se alienta a participar en este debate. Dado que los animales de granja (incluidos los de pequeñas explotaciones) constituyen una entidad económica, tal sistema debería estar basado en principios económicos. Los productores que trabajan en régimen de subsistencia se ven negativamente afectados por las disparidades existentes en materia de tecnología zoosanitaria, disparidad que cabe corregir con una combinación de intervenciones marcadas por la oferta y otras marcadas por la demanda, dirigiendo así más selectivamente el apoyo económico de entidades gubernamentales y organizaciones no gubernamentales. El programa GBADs (El impacto global de las enfermedades animales) servirá para compilar datos ya existentes con el fin de medir las pérdidas zoosanitarias dentro de sistemas productivos cuidadosamente caracterizados. La atribución coherente y transparente de estas pérdidas zoosanitarias permitirá efectuar comparaciones significativas del impacto que representan las enfermedades animales en el caso de diferentes dolencias, sistemas productivos o países y pondrá de relieve cómo se distribuye este impacto en función del género y la condición socioeconómica de las personas. Por medio del programa GBADs se creará un motor de conocimiento y portal de datos ubicado en la nube que permita al usuario acceder a mediciones del impacto de enfermedades y representaciones gráficas conexas, a herramientas de apoyo a la adopción de decisiones, en forma de hipotéticas situaciones zoosanitarias futuras, y a los resultados de modelizaciones económicas más generales. La aspiración del programa GBADs ­ reforzar el sistema alimentario en beneficio de la sociedad y el medio ambiente ­ constituye un ejemplo de aplicación en la práctica del pensamiento en clave de Una sola salud.

An economic case study of the control of dog-mediated rabies by an animal welfare organisation in Jaipur, India.

A global strategic plan for the elimination of dog-mediated human rabies deaths by 2030 was announced in 2018. The cost-effectiveness of annual mass dog vaccination programmes, as a control and elimination method, has been advocated on many occasions. Complementary methods, such as animal birth control (ABC) activities, have received less attention. This paper provides a case-study of a programme operated by Help in Suffering (HIS) in Jaipur, India from 1994/95 until 2016/17 comprising both ABC and additional vaccination-only activities. The availability of cost data alongside information on dog numbers, dog bites and human rabies cases provided an exceptionally detailed and unique retrospective dataset recording actual events and expenditures. Updated to 2016/17 prices, the total cost of the programme was 658,744 USD. Since 2007/2008, activity costs have been separated and returned costs of 10.78 USD per dog, both sterilised and vaccinated, and 1.86 USD per dog, vaccinated only. Over the course of the programme, the number of disability-adjusted life years (DALYs) due to premature death and the distress associated with dog bites was estimated to be 36,246 fewer than would have been expected if HIS had not been operating, based on a counterfactual scenario using pre-intervention values. Linking the DALY figure to the cost of the activities undertaken by HIS yields a cost of 26 USD per DALY averted. Discounted at 3%, the DALYs averted equate to 16,587 at a cost of 40 USD per DALY averted. Both cases make it a very cost-effective intervention, in relation to the threshold of investing one year's gross domestic product (GDP) per DALY averted (1981 USD in 2016/17). The monetary benefit from fewer dog bites and clinical human rabies cases requiring treatment amounted to 5.62 million USD after discounting, which, if attributed to Help in Suffering, yields a monetary benefit-cost ratio of 8.5. Thus, the potential monetary benefits greatly outweigh the programme costs, even without considering the DALYs averted. If a modest notional monetary value of one year's GDP is assigned to represent the human capital or production value of DALYs averted, the discounted societal economic benefit reaches 38.48 million USD and implies a benefit-cost ratio of 58.4. These economic analyses demonstrate that ABC activities in combination with additional vaccination efforts can be a cost-effective control measure for dog-mediated human rabies.

DALYs, dollars and dogs: how best to analyse the economics of controlling zoonoses.

Decision-makers increasingly require comprehensive economic metrics summarising and comparing the benefits and costs of controlling zoonotic diseases. The impact of disease in people is conventionally quantified in non-monetary terms, usually a disability-adjusted life year (DALY), whereas the losses due to disease in animals, particularly livestock, are quantified in monetary terms. The potential for the development of a non-monetary metric for ill health in animals, based on life years lost and disability, is discussed and rejected. Within and across animal species and livestock production systems, maximising life spans is not a consistent goal and morbidity/disabilities have very different weights and often lead to culling. By relating livestock losses to a measure of national income forgone, the recently developed alternative of converting monetary losses due to livestock illness into an animal loss equivalent (ALE) provides a viable solution. Based on this, the literature on the economics of controlling zoonoses is revisited and four options for quantifying and comparing benefits and costs are examined and illustrated using numerical examples. These are i) the simplistic grouping of all monetary elements and their comparison to DALYs averted (described as the aggregate net cost method), ii) the separable costs method, iii) the use of ALEs to convert all benefits to a non-monetary equivalent, termed the zoonotic DALY (zDALY), or iv) the use of a full monetary cost-benefit analysis, based on converting DALYs to a monetary equivalent. The strengths and weaknesses of each are discussed. For effective prioritisation and decision-making, it is vital that an analytical approach is widely adopted which yields consistent results and which supports the control of zoonoses.

Les décideurs politiques sont de plus en plus dépendants de méthodes exhaustives de mesure économique permettant de synthétiser et de comparer les avantages et les coûts de la lutte contre les zoonoses. Par convention, l'impact des maladies humaines est quantifié en des termes non monétaires, à savoir, le plus souvent, en « années de vie corrigées de l'incapacité ¼ (DALY), tandis que les pertes dues aux maladies animales, en particulier celles affectant les animaux d'élevage, sont quantifiées en termes monétaires. Dans cet article, les auteurs envisagent (et réfutent) la possibilité de mettre en oeuvre un système de mesure non monétaire des problèmes sanitaires chez les animaux qui soit basé sur les années de vie perdues ou d'incapacité. La longévité n'est pas un objectif uniformément recherché dans tous les systèmes de production, ni pour toutes les espèces animales, voire pour tous les individus au sein d'une même espèce, et la morbidité et l'incapacité représentent des fardeaux très variables, conduisant souvent à l'abattage. Parce qu'elle relie les pertes animales à une mesure de la réduction du revenu intérieur entraînée, la récente proposition de convertir les pertes monétaires dues aux maladies du bétail en un « équivalent pertes animales ¼ (indicateur ALE : animal loss equivalent) constitue une solution viable. À partir de ces considérations, les auteurs examinent la littérature dédiée aux aspects économiques de la lutte contre les zoonoses en détaillant quatre méthodes possibles pour en quantifier et comparer les avantages et les coûts, avec des exemples chiffrés. Ces possibilités sont : i) le simple regroupement de tous les éléments monétaires et leur comparaison en termes de DALY évitées (méthode dite de la présentation agrégée des coûts nets) ; ii) la méthode des coûts séparables ; iii) l'utilisation d'un indicateur ALE pour convertir l'ensemble des bénéfices en leur équivalent non monétaire, désigné sous le terme de DALY zoonotique (zDALY) ; iv) le recours à une analyse monétaire coûts-avantages exhaustive, après avoir converti les DALY en leur équivalent monétaire. Les auteurs font ressortir les atouts et les faiblesses de chacune de ces méthodes. La priorisation et la prise de décisions gagneront en efficacité si les décideurs adoptent et appliquent largement une approche analytique permettant d'obtenir des résultats cohérents et de renforcer la lutte contre les zoonoses.

Cada vez más, las instancias decisorias necesitan parámetros econométricos integrales, que sirvan para sintetizar y comparar los costos y beneficios de la lucha contra enfermedades zoonóticas. Convencionalmente, los efectos de una enfermedad en las personas se cuantifican en términos no monetarios, por lo general en forma de «años de vida ajustados en función de la discapacidad¼ (AVAD), mientras que las pérdidas inducidas por las enfermedades en animales, en particular el ganado, se cuantifican en valores monetarios. Los autores examinan y descartan la posible definición de parámetros no monetarios, basados en los años de vida perdidos y en la discapacidad, para cuantificar problemas zoosanitarios. Con independencia de la especie animal o el sistema de producción ganadera de que se trate, el de lograr una longevidad máxima no es un objetivo habitual, y los niveles de morbilidad o discapacidad, que suelen desembocar en el sacrificio sanitario, tienen un peso muy variable. En fechas recientes ha aparecido una alternativa que, al establecer una relación entre las pérdidas de ganado y una medida de la renta nacional prevista, ofrece una solución viable: se trata de convertir las pérdidas monetarias causadas por enfermedades del ganado en un «equivalente a las pérdidas animales¼ (animal loss equivalent: ALE). Partiendo de esta idea, los autores repasan la bibliografía sobre la economía de la lucha contra las zoonosis y examinan cuatro opciones para cuantificar y comparar beneficios y costos, ilustrándolas con ejemplos numéricos. Se trata de las siguientes: i) el simplificador procedimiento de agrupar todos los elementos monetarios y compararlos con los AVAD evitados (método que describen como del «costo agregado neto¼); ii) el método de los costos específicos; iii) el uso de «equivalentes a las pérdidas animales¼ para convertir todos los beneficios en un equivalente no monetario que denominan AVAD por zoonosis; y iv) el uso de un análisis monetario completo de la relación entre beneficios y costos, basado en la conversión de los AVAD en un equivalente monetario. A continuación examinan los puntos fuertes y débiles de cada uno de esos métodos, y concluyen que para fijar prioridades y adoptar decisiones con eficacia es vital aplicar de forma generalizada un mismo planteamiento analítico, que arroje resultados coherentes y ayude así a combatir las zoonosis.

Mapping the benefit-cost ratios of interventions against bovine trypanosomosis in Eastern Africa.

This study builds upon earlier work mapping the potential benefits from bovine trypanosomosis control and analysing the costs of different approaches. Updated costs were derived for five intervention techniques: trypanocides, targets, insecticide-treated cattle, aerial spraying and the release of sterile males. Two strategies were considered: continuous control and elimination. For mapping the costs, cattle densities, environmental constraints, and the presence of savannah or riverine tsetse species were taken into account. These were combined with maps of potential benefits to produce maps of benefit-cost ratios. The results illustrate a diverse picture, and they clearly indicate that no single technique or strategy is universally profitable. For control using trypanocide prophylaxis, returns are modest, even without accounting for the risk of drug resistance but, in areas of low cattle densities, this is the only approach that yields a positive return. Where cattle densities are sufficient to support it, the use of insecticide-treated cattle stands out as the most consistently profitable technique, widely achieving benefit-cost ratios above 5. In parts of the high-potential areas such as the mixed farming, high-oxen-use zones of western Ethiopia, the fertile crescent north of Lake Victoria and the dairy production areas in western and central Kenya, all tsetse control strategies achieve benefit-cost ratios from 2 to over 15, and for elimination strategies, ratios from 5 to over 20. By contrast, in some areas, notably where cattle densities are below 20per km(2), the costs of interventions against tsetse match or even outweigh the benefits, especially for control scenarios using aerial spraying or the deployment of targets where both savannah and riverine flies are present. If the burden of human African trypanosomosis were factored in, the benefit-cost ratios of some of the low-return areas would be considerably increased. Comparatively, elimination strategies give rise to higher benefit-cost ratios than do those for continuous control. However, the costs calculated for elimination assume problem-free, large scale operations, and they rest on the outputs of entomological models that are difficult to validate in the field. Experience indicates that the conditions underlying successful and sustained elimination campaigns are seldom met. By choosing the most appropriate thresholds for benefit-cost ratios, decision-makers and planners can use the maps to define strategies, assist in prioritising areas for intervention, and help choose among intervention techniques and approaches. The methodology would have wider applicability in analysing other disease constraints with a strong spatial component.

Mapping the economic benefits to livestock keepers from intervening against bovine trypanosomosis in Eastern Africa.

Endemic animal diseases such as tsetse-transmitted trypanosomosis are a constant drain on the financial resources of African livestock keepers and on the productivity of their livestock. Knowing where the potential benefits of removing animal trypanosomosis are distributed geographically would provide crucial evidence for prioritising and targeting cost-effective interventions as well as a powerful tool for advocacy. To this end, a study was conducted on six tsetse-infested countries in Eastern Africa: Ethiopia, Kenya, Somalia, South Sudan, Sudan and Uganda. First, a map of cattle production systems was generated, with particular attention to the presence of draught and dairy animals. Second, herd models for each production system were developed for two scenarios: with or without trypanosomosis. The herd models were based on publications and reports on cattle productivity (fertility, mortality, yields, sales), from which the income from, and growth of cattle populations were estimated over a twenty-year period. Third, a step-wise spatial expansion model was used to estimate how cattle populations might migrate to new areas when maximum stocking rates are exceeded. Last, differences in income between the two scenarios were mapped, thus providing a measure of the maximum benefits that could be obtained from intervening against tsetse and trypanosomosis. For this information to be readily mappable, benefits were calculated per bovine and converted to US$ per square kilometre. Results indicate that the potential benefits from dealing with trypanosomosis in Eastern Africa are both very high and geographically highly variable. The estimated total maximum benefit to livestock keepers for the whole of the study area amounts to nearly US$ 2.5 billion, discounted at 10% over twenty years--an average of approximately US$ 3300 per square kilometre of tsetse-infested area--but with great regional variation from less than US$ 500 per square kilometre to well over US$ 10,000. The greatest potential benefits accrue to Ethiopia, because of its very high livestock densities and the importance of animal traction, but also to parts of Kenya and Uganda. In general, the highest benefit levels occur on the fringes of the tsetse infestations. The implications of the models' assumptions and generalisations are discussed.

Estimating the costs of tsetse control options: an example for Uganda.

Decision-making and financial planning for tsetse control is complex, with a particularly wide range of choices to be made on location, timing, strategy and methods. This paper presents full cost estimates for eliminating or continuously controlling tsetse in a hypothetical area of 10,000km(2) located in south-eastern Uganda. Four tsetse control techniques were analysed: (i) artificial baits (insecticide-treated traps/targets), (ii) insecticide-treated cattle (ITC), (iii) aerial spraying using the sequential aerosol technique (SAT) and (iv) the addition of the sterile insect technique (SIT) to the insecticide-based methods (i-iii). For the creation of fly-free zones and using a 10% discount rate, the field costs per km(2) came to US$283 for traps (4 traps per km(2)), US$30 for ITC (5 treated cattle per km(2) using restricted application), US$380 for SAT and US$758 for adding SIT. The inclusion of entomological and other preliminary studies plus administrative overheads adds substantially to the overall cost, so that the total costs become US$482 for traps, US$220 for ITC, US$552 for SAT and US$993 - 1365 if SIT is added following suppression using another method. These basic costs would apply to trouble-free operations dealing with isolated tsetse populations. Estimates were also made for non-isolated populations, allowing for a barrier covering 10% of the intervention area, maintained for 3 years. Where traps were used as a barrier, the total cost of elimination increased by between 29% and 57% and for ITC barriers the increase was between 12% and 30%. In the case of continuous tsetse control operations, costs were estimated over a 20-year period and discounted at 10%. Total costs per km(2) came to US$368 for ITC, US$2114 for traps, all deployed continuously, and US$2442 for SAT applied at 3-year intervals. The lower costs compared favourably with the regular treatment of cattle with prophylactic trypanocides (US$3862 per km(2) assuming four doses per annum at 45 cattle per km(2)). Throughout the study, sensitivity analyses were conducted to explore the impact on cost estimates of different densities of ITC and traps, costs of baseline studies and discount rates. The present analysis highlights the cost differentials between the different intervention techniques, whilst attesting to the significant progress made over the years in reducing field costs. Results indicate that continuous control activities can be cost-effective in reducing tsetse populations, especially where the creation of fly-free zones is challenging and reinvasion pressure high.

Assessing the economics of animal trypanosomosis in Africa--history and current perspectives.

Finding appropriate ways of dealing with the problem of tsetse and trypanosomosis will be an important component of efforts to alleviate poverty in Africa. This article reviews the history of economic analyses of the problem, starting with the use of cost to guide choice of technique for tsetse control in the 1950s, followed by work in the 1970s and 1980s linking these to the impact of the disease on livestock productivity, and in the 1990s to its wider impact. In the current situation, with limited resources and a range of techniques for controlling or eliminating tsetse, the cost implications of choosing one technique or another are important and a recent study reviewed these costs. A novel approach to assessing the potential benefits from removing trypanosomosis by creating 'money maps' showed that high losses from animal trypanosomosis currently occur in areas with high cattle population densities on the margins of the tsetse distribution and where animal traction is an important component of farming systems. Given the importance of the decisions to be made in the next decade, when prioritising and choosing techniques for dealing with tsetse and trypanosomosis, more work needs to be done underpinning such mapping exercises and estimating the true cost and likely impact of planned interventions.

Analytical tools for planning cost-effective surveillance in Gambiense sleeping sickness.

The re-emergence of sleeping sickness as a major health problem in parts of Africa, combined with the new sources of financial support and provision of drugs means that an investigation of the cost-effectiveness of the different approaches is timely. There has been very little work done on the economics of controlling either form of sleeping sickness. This paper builds on work done for WHO by the authors on developing a framework for analysing the cost-effectiveness of different methods for surveillance in gambiense sleeping sickness. The framework has been used to build a spreadsheet which makes it possible to simulate the effects of controlling the disease at different prevalences, for example using mobile teams or various forms of fixed post surveillance and screening different proportions of the population in a year. Prices, control strategies, prevalence, sensitivity and specificity of tests are all variables which can be altered to suit different situations or investigate how different approaches perform. As new research is beginning to produce calculations of the burden of sleeping sickness, in terms of disability-adjusted life years (DALY) potentially averted by controlling the disease, it is possible to combine these DALY estimates with the analyses of cost-effectiveness undertaken in these exercises to look at the cost-utility of the work, both to compare different approaches and demonstrate that controlling sleeping sickness represents good value for money as an investment in health.

Infection by microsporidia disrupts the host cell cycle.

Microsporidia of the genus Encephalitozoon infect mammalian cells and have become a source of morbidity and mortality in immunocompromised humans. Encephalitozoon microsporidia develop and mature within parasitophorous vacuoles, enlarging the vacuole over time until it eventually occupies most of the cytoplasm of the host cell. The ability of the host cell to accommodate such a large burden for several days suggests that the parasite subverts normal host cell processes to ensure optimal environmental conditions for its growth and development. Since this environment would be threatened if cell division of the host cell occurred, we have formulated the hypothesis that infection with Encephalitozoon microsporidia induces an arrest in the cell cycle of the host cell. In support of this hypothesis, we have found that mitotic index and DNA duplication are reduced in infected cells as compared to uninfected cells. The number of host cell nuclei in S phase is increased. The levels of cyclin D1 and the percentage of cells in G1 are reduced; however, the levels of cyclin B1 are elevated even though the percentage of cells in G2/M is decreased. These results suggest that host cells infected with Encephalitozoon microsporidia are blocked at multiple points in the cell cycle.

Spatiotemporal distribution of zonulae adherens and associated actin bundles in both epithelium and fiber cells during chicken lens development.

Zonulae adherens and associated actin bundles (ZA/AB) are believed to play a major role in epithelial folding and invagination during morphogenesis of neural tube and other vesicular structures. The lens morphogenesis is associated with the formation of the lens vesicle in which ZA/AB would be needed during the formation process. However, the existence of ZA/AB in the lens has never been established. In this study we report for the first time the existence of ZA/AB in both lens epithelium and fiber cells during embryonic development of chicken lens from E4 to E20. Light microscopy revealed contacts between the lens epithelium and primary fiber cells, and between the lens epithelium and secondary fiber cells at E4 and E11, respectively. Thin-section electron microscopy consistently revealed ZA/AB near both the apical ends of lens epithelial cells and primary fiber cells at E4. This arrangement manifests as a parallel pair of belt-like ZA/AB along the epithelium-fiber interface. In semi-tangential sections, a continuous belt-like ZA/AB was also evidenced in individual epithelial cells and fiber cells. Furthermore, the same ZA/AB arrangement was observed near both the apical ends of epithelial cells and secondary fiber cells at E11. Besides ZA/AB, macular-type fasciae adherens were distributed regularly between epithelial cells, between primary fibers, between secondary fibers, and between epithelium and both primary and secondary fibers. Immunofluorescence strongly and preferentially labeled N-cadherin at both the apical ends of lens epithelium and primary or secondary fibers at the corresponding ages, suggesting a direct association with the zonulae adherens. Also punctate N-cadherin labeling was commonly seen along various regions of primary and secondary fiber cells at different ages, and to a larger extent in the mature fibers of older lenses. This study suggests that: (1) ZA/AB located at the apices of lens epithelial cells may play a crucial role in the early stages of lens morphogenesis (e.g. lens vesicle formation); (2) ZA/AB of primary and secondary fiber cells originate from the epithelial cells during their elongation and differentiation; (3) owing to the restricted distribution of ZA/AB, abundant fasciae adherens are needed to maintain the structural stability of the epithelium and fiber cells during development and maturation; and (4) N-cadherin is the principle adhesion protein for both the zonulae adherens and fasciae adherens in the lens.

Actin filament bundles in cortical fiber cells of the rat lens.

The distribution and organization of actin filament bundles were studied in cortical fiber cells of rat lenses at various ages (3 days to 2.5 months old), using thin-section electron microscopy, immunocytochemistry and immunoblotting. Electron microscopy showed that actin bundles were regularly found along cortical fiber cell membranes of the lens at all ages studied. The actin bundles were commonly arranged in three distinct units, one bundle in each fiber cell, located at the intersections where three hexagonal fiber cells meet as seen in cross sections. These actin bundles were approximately 150 nm in diameter and were composed of 7-nm small filaments. They were aligned parallel to the long axis of fiber cells as judged by both cross and longitudinal sections. The outside border of each bundle was always surrounded by a zone of 10-nm intermediate filaments which have the same orientation as that of the actin bundles. In longitudinal sections, elongated actin bundles were always parallel to the cell membranes. A number of individual actin bundles sometimes were found to form a chain with periodic short intervals. In addition, actin bundles were frequently associated with adherens junctions near the intersections and other regions of fiber cell membranes. By immunoelectron microscopy, we demonstrated that these filament bundles indeed contained actins. By rhodamine-phalloidin labelling, we found that labeled actin bundles appeared as large, distinct dots at the corners of hexagonal fiber cells in all ages studied. In addition, non-bundle F-actins were labeled preferentially along the cell membranes of the short sides of hexagonal fiber cells. This resulted in a unique zigzag pattern of actin labeling commonly seen in the cortical fiber cells of a mature rat lens. Finally, we showed that alpha-actinin was associated with the actin bundles in the fiber cells by immunofluorescent double labeling and immunoblotting. It is suggested that this unique arrangement of actin bundles in fiber cells may provide a stabilizing structure for forming a sharp angle at each corner of fiber cells, thereby the hexagonal shape of the cells can be maintained.

Gap junction structures and distribution patterns of immunoreactive connexins 46 and 50 in lens regrowths of Rhesus monkeys.

Gap junction structures and distribution patterns of immunoreactive connexin46 (Cx46) and connexin50 (Cx50) in normal lenses and lens regrowths of rhesus monkeys were studied using electron microscopy and immunofluorescence double-labeling. Lens regrowths were collected from aphakic eyes of young monkeys whose natural lenses had been surgically removed 11-34 months earlier to simulate monocular congenital cataract surgery in human infants. Approximately 90% of the lens regrowths examined was in the form of a doughnut-shaped Soemmerring's ring located behind the iris. The lens regrowth consisted of lens epithelium and lens fibers enclosed within hypertrophied capsular material. The superficial equatorial region usually contained nucleated young fibers of normal appearance. The other regions consisted of many swollen fibers. Gap junctions were readily observed between fiber cells of both normal and swollen configuration in the lens regrowth. In superficial fibers, gap junctions were not associated with cytoskeletal components. In the intermediate and the deeper cortical regions, actin filament bundles were found specifically associated with gap junctions along both of their cytoplasmic surfaces. An immunofluorescence double-labeling study showed that Cx46 and Cx50 were labeled in the same gap junctions in both superficial and deeper cortical fibers of the normal lens. In contrast, in the lens regrowth strong co-labeling of Cx46 and Cx50 was only observed in the superficial fibers. The labeling for Cx50 was very weak or absent in the deeper cortex, whereas the strong labeling for Cx46 persisted throughout the major portion of the deeper cortex. The labeling for Cx46 finally disappeared in the much deeper cortex. This study shows that (1) the same distribution pattern of actin bundle/gap junction association found in normal lenses is seen in the lens regrowth, and (2) the immunoreactive distribution of Cx46 and Cx50 differ in the lens regrowths as compared with those in the normal lenses of rhesus monkeys.

Circadian rhythm in the visual system of the lizard Anolis carolinensis.

The electroretinogram (ERG) was recorded from free-moving Anolis lizards once per hour for 5 days. As in our previous work, the b-wave, but not the a-wave, showed a reliable circadian rhythm (CR) in amplitude, with an acrophase near projected noon. Both the a- and b-waves showed a CR in peak time (implicit time, or IT), with the a-wave IT being longest near midnight, and the b-wave IT at midday. Acrophases were shifted when animals were housed on a phase-shifted light-dark cycle. The ERG CR was unaffected by removal of the parietal organ, but it was virtually abolished by removal of the pineal gland, thus suggesting that pineal output (probably melatonin) modulates retinal responses. In addition to the ERG, the tectal light-evoked potential exhibited a CR--a finding compatible with a circadian variation in retinal output. Lastly, the amplitude of the ERG component waveforms showed a seasonal variation, but the ERG CR was constant across the year.

The altricial pigeon is born blind with a transient glycogen cataract.

The lens nucleus of altricial birds contains a large amount of glycogen. It is not known why glycogen in such concentration does not cause a trace of lens opalescence. Here we report that the altricial pigeon is born with a dense nuclear opacity; this opacity has practically disappeared by 4 weeks of age. Thin-section electron microscopy revealed that the opacity was specifically associated with an enormous number of large glycogen aggregates in nuclear fiber cells. These aggregates of various sizes (up to approximately 5 microns) were composed of smaller individual 35-nm beta glycogen particles. In contrast, glycogen aggregates were not seen in nuclear fiber cells of all transparent older lenses. The glycogen aggregates have gradually dissociated into a homogeneous distribution of individual beta particles in the entire cytoplasm of nuclear fibers which accompanies the development of lens transparency. This study suggests that an extensive accumulation of glycogen aggregates in the lens nucleus is the cause of light scattering and opacification. The transparency of the altricial pigeon lens during normal development is therefore regulated by two different forms of glycogen. Precocial birds such as chick have no lens glycogen, therefore never develop a glycogen cataract and have excellent visual acuity upon hatching.

Molecular and cellular biology of Wilms' tumour.

Wilms' tumour is an embryonal kidney tumour which exists in an hereditary and sporadic form. Apart from its obvious importance as a model for renal development and differentiation, the tumour has recently been exploited as an example of the action of tumour suppressor genes (or anti-oncogenes). The latter genes are characterised by a somatic loss of genetic information in tumour development, specifically from the short arm of human chromosome 11 in Wilms' tumour. To further study the developmental aspects of the tumour we have established in vitro cell cultures from tumour tissues, which, unlike the majority of Wilms' tumour cell lines, have been genotyped according to their chromosome 11 gene status and their antigen expression patterns, compared to the original normal kidney and tumour tissues. The cell cultures exist both as primary and secondary cultures, and their limited life span in culture has been extended by transfection of SV40 large T antigen. The mechanism of tumour suppression by the Wilms' locus has been explored by producing cell hybrids between the immortalised kidney cells, and an "indicator cell" (HeLa), whose chromosome 11 genotypes have been monitored in vivo and in vitro by restriction fragment length polymorphisms. Non-random patterns of inheritance of the mutant allele have also been investigated, both in tumour tissue and in syndromes, like the Beckwith-Wiedemann Syndrome, which pre-dispose to development of Wilms' tumour (and other embryonal tumours). It is also apparent that allele-specific methylation occurs in Wilms' tumour tissues, probably resulting in changes of gene expression patterns. Significant elevation of transcription of the N-myc oncogene was detected in the blastemal cells of the most malignant Wilms' tumours, whereas a marked decrease in the expression of HLA class I, at both RNA and protein levels was observed in the same cells. Wilm's tumour provides a clear illustration of the requirement for a combination of dominantly and recessively acting genes, in order to produce a malignant embryonal tumour.

Loss of chromosome 11p alleles in cultured cells derived from Wilms' tumours.

Cell cultures have been produced from five Wilms' tumours. All cultures had a finite lifespan and a pattern of antigen expression which indicated that the cells were derived from the differentiated components of the tumours. No cells showed any of the expected characteristics of the putative Wilms' tumour stem cell. Nevertheless, in both cases where the original tumours showed a loss of heterozygosity at chromosome 11p alleles, the cultured cells also demonstrated a loss of heterozygosity. Thus these cell cultures definitely originated from Wilms' tumour tissue. The results demonstrate that cell cultures can be produced from the differentiated tissues present in Wilms' tumours and that these non-immortal cells show no 'transformed' phenotype, even though they possess the genetic changes present in the original tumour.