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Inheritance and longevity of infectious pancreatic necrosis virus in the zebra fish, Brachydanio rerio (Hamilton Buchanan)
Applied and Environmental Microbiology
Abstract
Zebra fish (Brachydanio rerio) were injected with infectious pancreatic necrosis virus (IPNV) and then spawned to determine whether the virus was passed on to the eggs, and if it was, how long it remained in the free-swimming F1. The mating variations included parents receiving one or two injections of virus, and within these categories, matings in which both parents were treated or only one parent was treated. The results showed that transmission of IPNV to the egg did occur, and that this transmission was via the female alone. However, if the female was allowed to produce antibodies to the virus, as when she received two injections of IPNV, she transmitted the virus to the eggs for only a short period of time. In addition, when the virus was transmitted to the egg, it remained in the free-swimming F1 for a period of at least 5 months.
... Most of the pathogens that are known represent bacterial, fungal, or parasitic agents that were previously identified in commercially important fish species and later recognized in zebrafish. The lack of information about naturally occurring viral infections in zebrafish reflects a lack of investigation in this area rather than an inability of viral pathogens to infect zebrafish , as evidenced by studies documenting the experimental infection of zebrafish with viruses isolated from other fish species (LaPatra et al. 2000;Lopez-Munoz et al. 2010;Lu et al. 2008;Ludwig et al. 2011;Novoa et al. 2006;Phelan et al. 2005b;Sanders et al. 2003;Seeley et al. 1977;Xu et al. 2008) and the presence of multiple endogenous retroviruses, retrotransposons, and other retroid agents in the zebrafish genome (Basta et al. 2007;Shen and Steiner 2004). ...
... Infection studies designed to develop the zebrafish as a model for viral infection in commercially important fish species have demonstrated the experimental susceptibility of zebrafish to infection by several families of viruses, including Birnaviridae (IPNV) (LaPatra et al. 2000;Seeley et al. 1977); Rhabdoviridae (IHNV) (LaPatra et al. 2000;Ludwig et al. 2011), Spring viremia of carp virus (Lopez-Munoz et al. 2010;Sanders et al. 2003), VHSV (Novoa et al. 2006) and SHRV (Phelan et al. 2005b); Nodaviridae (Malabar grouper nervous necrosis virus) ; and Iridoviridae (infectious spleen and kidney necrosis virus) (Xu et al. 2008). The susceptibility of zebrafish to experimental infections with this broad range of viruses suggests not only that naturally occurring viruses occur in zebrafish but also that many viral families may be represented among the as-yet unidentified zebrafish viruses. ...
Naturally occurring viral infections have the potential to introduce confounding variability that leads to invalid and misinterpreted data. Whereas the viral diseases of research rodents are well characterized and closely monitored, no naturally occurring viral infections have been characterized for the laboratory zebrafish (Danio rerio), an increasingly important biomedical research model. Despite the ignorance about naturally occurring zebrafish viruses, zebrafish models are rapidly expanding in areas of biomedical research where the confounding effects of unknown infectious agents present a serious concern. In addition, many zebrafish research colonies remain linked to the ornamental (pet) zebrafish trade, which can contribute to the introduction of new pathogens into research colonies, whereas mice used for research are purpose bred, with no introduction of new mice from the pet industry. Identification, characterization, and monitoring of naturally occurring viruses in zebrafish are crucial to the improvement of zebrafish health, the reduction of unwanted variability, and the continued development of the zebrafish as a model organism. This article addresses the importance of identifying and characterizing the viral diseases of zebrafish as the scope of zebrafish models expands into new research areas and also briefly addresses zebrafish susceptibility to experimental viral infection and the utility of the zebrafish as an infection and immunology model.
... Survivors of IPNV infection can become lifelong carriers that transmit virus both horizontally and vertically [20]. These observations motivated the first study to use zebrafish for investigating virus infection biology, in which the authors demonstrated that IPNV can transmit to the eggs of infected adults and persist in the next generation [21]. Subsequent studies have confirmed that IPNV can infect zebrafish but does not cause observable disease [22,23]. ...
Zebrafish are popular research organisms selected for laboratory use due in part to widespread availability from the pet trade. Many contemporary colonies of laboratory zebrafish are maintained in aquaculture facilities that monitor and aim to curb infections that can negatively affect colony health and confound experiments. The impact of laboratory control on the microbial constituents associated with zebrafish in research environments compared to the pet trade are unclear. Diseases of unknown causes are common in both environments. We conducted a metatranscriptomic survey to broadly compare the zebrafish-associated microbes in pet trade and laboratory environments. We detected many microbes in animals from the pet trade that were not found in laboratory animals. Cohousing experiments revealed several transmissible microbes including a newly described non-enveloped, double-stranded RNA virus in the Birnaviridae family we name Rocky Mountain birnavirus (RMBV). Infections were detected in asymptomatic animals from the pet trade, but when transmitted to laboratory animals RMBV was associated with pronounced antiviral responses and hemorrhagic disease. These experiments highlight the pet trade as a distinct source of diverse microbes that associate with zebrafish and establish a paradigm for the discovery of newly described pathogenic viruses and other infectious microbes that can be developed for study in the laboratory.
... Survivors of IPNV infection can become lifelong carriers that transmit virus both horizontally and vertically (Wolf et al., 1963). These observations motivated the first study to use zebrafish for investigating virus infection biology, in which the authors demonstrated that IPNV can transmit to the eggs of infected adults and persist in the next generation (Seeley et al., 1977). Subsequent studies have confirmed that IPNV can infect zebrafish but does not cause observable disease (Bello-Perez et al., 2019;LaPatra et al., 2000). ...
Zebrafish are popular research organisms selected for laboratory use due in part to widespread availability from the pet trade. Many contemporary colonies of laboratory zebrafish are maintained in aquaculture facilities that monitor and aim to curb infections that can negatively affect colony health and confound experiments. The impact of laboratory control on the microbial constituents associated with zebrafish in research environments compared to the pet trade are unclear. Diseases of unknown causes are common in both environments. We conducted a metagenomic survey to broadly compare the zebrafish-associated microbes in pet trade and laboratory environments. We detected many microbes in animals from the pet trade that were not found in laboratory animals. Co-housing experiments revealed several transmissible microbes including a newly described non-enveloped, double-stranded RNA virus in the Birnaviridae family we name Rocky Mountain birnavirus (RMBV). Infections were detected in asymptomatic animals from the pet trade, but when transmitted to laboratory animals RMBV was associated with pronounced antiviral responses and hemorrhagic disease. These experiments highlight the pet trade as a distinct source of diverse microbes that associate with zebrafish and establish a paradigm for the discovery of newly described pathogenic viruses and other infectious microbes that can be developed for study in the laboratory.
... These viral families include the Iridoviridae, Birnaviridae, Rhabdoviridae, SVCV: spring viremia of carp virus, SHRV, and VHSV. In addition to implying that zebrafish are frequently infected with viruses spontaneously, the likelihood of the fragility of zebrafish to experimental infections with such a diverse array of viruses increases the chance that other viral family members are present among unreported zebrafish viruses (Crim and Riley, 2012;La Patra et al., 2000;López-Muñoz et al., 2010;Lu et al., 2008;Ludwig et al., 2011;Novoa et al., 2006;Phelan et al., 2005b;Seeley et al., 1977;Xu et al., 2008). ...
Emerging bio-contaminants such as viruses have affected health and environment settings of every country. Viruses are the minuscule entities resulting in severe contagious diseases like SARS, MERS, Ebola, and avian influenza. Recent epidemic like the SARS-CoV-2, the virus has undergone mutations strengthen them and allowing to escape from the remedies. Comprehensive knowledge of viruses is essential for the development of targeted therapeutic and vaccination treatments. Animal models mimicking human biology like non-human primates, rats, mice, and rabbits offer competitive advantage to assess risk of viral infections, chemical toxins, nanoparticles, and microbes. However, their economic maintenance has always been an issue. Furthermore, the redundancy of experimental results due to aforementioned aspects is also in examine. Hence, exploration for the alternative animal models is crucial for risk assessments. The current review examines zebrafish traits and explores the possibilities to monitor emerging bio-contaminants. Additionally, a comprehensive picture of the bio contaminant and virus particle invasion and abatement mechanisms in zebrafish and human cells is presented. Moreover, a zebrafish model to investigate the emerging viruses such as coronaviridae and poxviridae has been suggested.
... In 1977, the first study using zebrafish as a model for viral infections was conducted. Results showed that injected IPNV was transmitted to the eggs (vertical transfer), and that this transmission occurred via females alone [137]. It was later confirmed that zebrafish also could acquire the infection by the natural route through the water body [132]. ...
The use of zebrafish as a model for human conditions is widely recognized. Within the last couple of decades, the zebrafish has furthermore increasingly been utilized as a model for diseases in aquacultured fish species. The unique tools available in zebrafish present advantages compared to other animal models and unprecedented in vivo imaging and the use of transgenic zebrafish lines have contributed with novel knowledge to this field. In this review, investigations conducted in zebrafish on economically important diseases in aquacultured fish species are included. Studies are summarized on bacterial, viral and parasitic diseases and described in relation to prophylactic approaches, immunology and infection biology. Considerable attention has been assigned to innate and adaptive immunological responses. Finally, advantages and drawbacks of using the zebrafish as a model for aquacultured fish species are discussed.
... Evidence for vertical transmission of IPNV is documented for brook trout (Wolf et al., 1963), zebrafish (Seeley et al., 1977), rainbow trout (Dorson and Torchy, 1985) and arctic char (Ahne and Negele, 1985). For Atlantic salmon, there is no conclusive evidence of vertical transmission of IPNV yet. ...
Birnaviruses of aquatic organisms constitute small, nonenveloped icosahedral viruses with bisegmented, double-stranded RNA (dsRNA) genomes, and currently, two genera infect aquatic organisms; Aquabirnavirus and Blosnarvirus. Among aquabirnaviruses, the infectious pancreatic necrosis virus (IPNV) is the type species and causes severe diseases in salmonids, while there are a number of other aquabirnaviruses that infect other aquatic organisms. Blotched snakehead virus is the type strain of the Blosnarvirus genus, infecting blotched snakehead (Channa maculata). The genome of birnaviruses is organized into two segments, A and B. Segment A encodes the structural proteins VP2 and VP2 plus the virus protease (VP4) and a nonstructural protein, VP5. Segment B encodes the viral polymerase. The virulence traits of IPNV have been well defined, and for strains infecting Atlantic salmon, highly virulent strains carry defined amino acids in defined residues of the VP2 protein. Vaccination and selective breeding in Atlantic salmon have contributed to reducing the impact of IPNV infection in salmonid aquaculture worldwide.
... Infectious pancreatic necrosis virus has been recovered from a wide range of salmonid and nonsalmonid fish. Some isolations were made during natural epizootics or following experimental inoculation while others were made from healthy appearing fish (Adair and Ferguson 1981;Ahne 1978;Castric and Chastel 1980;Dorson 1982;McAllister et al. 1982;Munro and Duncan 1977;Sano et al. 1981;Seeley et al. 1977;Stephens et al. 1980 Munro et al. 1976). Viruses resembling that of IPN have been isolated from several species of marine mollusks and crustaceans (Underwood et al. 1977). ...
Infectious pancreatic necrosis (IPN) is a viral disease principally associated with salmonids, although IPN and lPN-like viruses have been isolated from various nonsa1rnonid fish and marine invertebrates. Acute infection occurs in 1- to 4-month-old salmonids and can result in cumulative mortality approaching 100%. In contrast, fish 6 months o~d or older can undergo subclinical or inapparent infection, but experience no significant mortality. Survivors of the disease can become lifelong carriers of the virus. Epizootics of IPN have been reported worldwide, and several virus serotypes are recognized.
The disease known as IPN was probably first described by M'Gonigle (1941) as acute catarrhal enteritis and attributed by him to nutritional factors. The viral etiology of IPN was established by Wolf and co-workers (1960). Comprehensive reviews of the disease and the virus have been made by Dorson (1982), McAllister (1979), Munro and Duncan (1977), Pilcher and Fryer (1980), Roberts (1978), and Wolf (1972, 1976).
... Experimental injections of virus into the adult fish have revealed that the males appear to play no role in the transmission between parents and offspring. In addition, the virus is maintained in young zebrafish for a period of at least five months (Seeley et al. 1977). ...
The zebrafish (Danio rerio) has become known as an excellent model organism for studies of vertebrate biology, vertebrate genetics, embryonal development, diseases and drug screening. Nevertheless, there is still lack of detailed reports about usage of the zebrafish as a model in veterinary medicine. Comparing to other vertebrates, they can lay hundreds of eggs at weekly intervals, externally fertilized zebrafish embryos are accessible to observation and manipulation at all stages of their development, which makes possible to simplify the research techniques such as fate mapping, fluorescent tracer time-lapse lineage analysis and single cell transplantation. Although zebrafish are only 2.5 cm long, they are easy to maintain. Intraperitoneal and intracerebroventricular injections, blood sampling and measurement of food intake are possible to be carry out in adult zebrafish. Danio rerio is a useful animal model for neurobiology, developmental biology, drug research, virology, microbiology and genetics. A lot of diseases, for which the zebrafish is a perfect model organism, affect aquatic animals. For a part of them, like those caused by Mycobacterium marinum or Pseudoloma neutrophila, Danio rerio is a natural host, but the zebrafish is also susceptible to the most of fish diseases including Itch, Spring viraemia of carp and Infectious spleen and kidney necrosis. The zebrafish is commonly used in research of bacterial virulence. The zebrafish embryo allows for rapid, non-invasive and real time analysis of bacterial infections in a vertebrate host. Plenty of common pathogens can be examined using zebrafish model: Streptococcus iniae, Vibrio anguillarum or Listeria monocytogenes. The steps are taken to use the zebrafish also in fungal research, especially that dealing with Candida albicans and Cryptococcus neoformans. Although, the zebrafish is used commonly as an animal model to study diseases caused by external agents, it is also useful in studies of metabolic disorders including fatty liver disease and diabetes. The zebrafish is also a valuable tool as a model in behavioral studies connected with feeding, predator evasion, habituation and memory or lateralized control of behavior. The aim of the present article is to familiarize the reader with the possibilities of Danio rerio as an experimental model for veterinary medicine.
The inflammatory response to viral infection in humans is a dynamic process with complex cell interactions that are governed by the immune system and influenced by both host and viral factors. Due to this complexity, the relative contributions of the virus and host factors are best studied in vivo using animal models. In this review, we describe how the zebrafish (Danio rerio) has been used as a powerful model to study host-virus interactions and inflammation by combining robust forward and reverse genetic tools with in vivo imaging of transparent embryos and larvae. The innate immune system has an essential role in the initial inflammatory response to viral infection. Focused studies of the innate immune response to viral infection are possible using the zebrafish model as there is a 4-6 week timeframe during development where they have a functional innate immune system dominated by neutrophils and macrophages. During this timeframe, zebrafish lack a functional adaptive immune system, so it is possible to study the innate immune response in isolation. Sequencing of the zebrafish genome has revealed significant genetic conservation with the human genome, and multiple studies have revealed both functional conservation of genes, including those critical to host cell infection and host cell inflammatory response. In addition to studying several fish viruses, zebrafish infection models have been developed for several human viruses, including influenza A, noroviruses, chikungunya, Zika, dengue, herpes simplex virus type 1, Sindbis, and hepatitis C virus. The development of these diverse viral infection models, coupled with the inherent strengths of the zebrafish model, particularly as it relates to our understanding of macrophage and neutrophil biology, offers opportunities for far more intensive studies aimed at understanding conserved host responses to viral infection. In this context, we review aspects relating to the evolution of innate immunity, including the evolution of viral pattern recognition receptors, interferons and interferon receptors, and non-coding RNAs.
The advent of fish cell and tissue culture in the mid-1950s provided the technical impetus for expanding fish virology beyond the confines of disease transmission studies. A variety of fish viruses and viruslike agents have now been recognized, and most are associated with pathological conditions. Not unexpectedly, research interests have focused on those fish viruses which impact most significantly on economic and aesthetic sensitivities. As a result, some of the fish viruses have been well characterized and classified into established viral taxonomic groupings while others have been only partly characterized or demonstrated solely by electron microscopy and their classification is tentative.
Fish Pathology is the definitive, classic and essential book on the subject, providing in-depth coverage across all major aspects of fish pathology. This new, fully updated and expanded fourth edition builds upon the success of the previous editions which have made Fish Pathology the best known and most respected book in the field, worldwide. Commencing with a chapter covering the aquatic environment, the book provides comprehensive details of the anatomy and physiology of teleosts, pathophysiology and sytematic physiology, immunology, neoplasia, virology, parasitology, bacteriology, mycology, nutritional pathology and other non-infectious diseases. A final chapter provides extremely useful details of the most widely-used and trusted laboratory methods in the area. Much new infomation is included in this new edition, including enhanced coverage of any diseases which have become commercially significant since publication of the previous edition. Beautifully illustrated in full colour throughout with many exceptional photographs, Fish Pathology, Fourth Edition, is an essential purchase for fish pathologists, fish veterinarians, biologists, microbiologists and immunologists, including all those working in diagnostic services worldwide. Personnel working in fish farming and fisheries will also find much of great use and interest within the book's covers. All libraries in universities and research establishments where biological and veterinary sciences are studied and taught should have copies of this landmark publication on their shelves.
Infectious pancreatic necrosis virus (IPNV) did not cause increased mortality in experimentally challenged striped bass, Morone saxatilis (Walbaum). Fry became transiently infected after waterborne challenge but fingerlings were resistant to that route. However, striped bass fingerlings readily became chronic virus carriers following ingestion of IPNV-contaminated food. Vertical transmission was not demonstrated using either IPNV-carrier striped bass adults or IPNV-exposed sex products.
Ornamental fish are susceptible to many viral pathogens, some of which are readily identifiable, whereas others remain obscure. Identification is not always possible owing to lack of resources or inability of the virus to grow in available fish cell lines. In many instances viral infection may remain latent until adverse environmental conditions, such as poor water quality, overcrowding, or rough handling, trigger the onset of disease. Frequently the only course is to destroy the fish and effectively disinfect all equipment. Consequently, for many viral pathogens, our knowledge of the etiology of the associated disease remains minimal. In this article we review not only those diseases of ornamental fish with a well-established viral etiology but also those conditions that may be associated with, but not necessarily caused by, a viral infection. Moreover, also included are other reports of single cases that are also important because they represent exotic incursions.
Las enfermedades infectocontagiosas de origen vírico son uno de los problemas con mayor impacto en el desarrollo de la acuicultura, ya que generalmente provocan unas altas mortalidades y frente a ellas no existen tratamientos efectivos ni vacunas. La vacunación sería el método más eficaz para controlar el impacto de estas enfermedades, sin embargo, para muchos de los virus más devastadores, las vacunas tradicionales (vacunas atenuadas, muertas) o la vacunación con antígenos virales han resultado ineficaces. Dentro de este contexto, la vacunación genética (vacunas ADN), representa en estos momentos la opción más viable. Desde hace unos años, se viene experimentando con las vacunas ADN para muchos de estos patógenos, con resultados positivos. La mayor parte de las vacunas ADN desarrolladas en el ámbito de la piscicultura son frente a rabdovirus, los virus de peces con mayor repercusión en la acuicultura continental, y entre los que se encuentran el virus de la necrosis hematopoyética infecciosa (IHNV) y el virus de la septicemia hemorrágica viral (VHSV). Sin embargo, hasta que no se resuelvan algunos problemas asociados con estas vacunas ADN, como son los aspectos relacionados con la seguridad y/o rentabilidad económica, éstas no estarán disponibles para el sector. En este trabajo, se revisa el estado actual de la investigación en vacunas ADN para virus de peces, así como de los problemas que tendrán que ser resueltos para conseguir su comercialización.
In this review, a survey is made of the published literature on the viral diseases of fish available up to and including the year 1978. It is divided into two main sections. Part 1 describes 11 diseases where a virus has been isolated and proven to be the causative agent. Part 2 discusses 16 diseases where there is reason to suspect viral etiology because of evidence deriving from electron microscopy or transmission experiments with bacteria-free filtrates of homogenates of diseased tissue, but where final proof of a causative relationship is lacking. The review attempts to provide the most significant information on the disease process itself, in most cases including external signs, fish species susceptible, pathology, geographic distribution, existence of carriers, methods of transmission, and control. It also gives the most recent and significant data concerning the nature of the causative virus, including its cultural, biological, and physicochemical properties, where such information is available.
The zebrafish (Danio rerio) is now the pre-eminent vertebrate model system for clarification of the roles of specific genes and signaling pathways in development. The zebrafish genome will be completely sequenced within the next 1-2 years. Together with the substantial historical database regarding basic developmental biology, toxicology, and gene transfer, the rich foundation of molecular genetic and genomic data makes zebrafish a powerful model system for clarifying mechanisms in toxicity. In contrast to the highly advanced knowledge base on molecular developmental genetics in zebrafish, our database regarding infectious and noninfectious diseases and pathologic lesions in zebrafish lags far behind the information available on most other domestic mammalian and avian species, particularly rodents. Currently, minimal data are available regarding spontaneous neoplasm rates or spontaneous aging lesions in any of the commonly used wild-type or mutant lines of zebrafish. Therefore, to fully utilize the potential of zebrafish as an animal model for understanding human development, disease, and toxicology we must greatly advance our knowledge on zebrafish diseases and pathology.
To improve our understanding of the genetic basis of fish disease, we developed a pathogen model, using zebrafish (Danio rerio) and spring virema of carp virus (SVCV). Replicate groups of 10 fish were acclimated to 20 or 24 degrees C, then were exposed to SVCV concentrations of 10(3) to 10(5) plaque-forming units per milliliter (PFU/ml) of water and observed daily. In a second trial, fish were acclimated to 15 degrees C, and replicate groups of 10 fish were exposed to SVCV at a concentration of 10(5) PFU/ml; however, the temperature was raised 1 degrees C/wk. Moribund fish were collected for histologic examination, and dead fish were assayed for virus by use of cell culture and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. Mortality exceeded 50% in fish exposed to 10(5) PFU of SVCV/ml at the lower temperatures. Clinical signs of disease became evident seven days after viral exposure and were observed most consistently in fish of the 10(5) PFU/ml groups. Affected zebrafish were anorectic and listless, with epidermal petechial hemorrhages followed by death. Use of plaque assays and RT-PCR analysis confirmed presence of SVCV at titers > or = 10(4) PFU/g of tissue. Histologic lesions included multifocal brachial necrosis and melanomacrophage proliferation in gills, liver, and kidneys. These results indicate that zebrafish are susceptible to infection by SVCV under conditions that mimic a natural route of exposure.
The first problem raised by CO2 sensitivity in Drosophila concerns the true nature of the determinative agent, whether it is a virus or an extrachromosomal genetic factor. Pathogenicity is surely not a valid criterion for a restrictive definition of viruses. Many virus infections are not accompanied by any pathologic symptoms and, on the other hand, true pathologic conditions can be the direct outcome of genetic factors. Infectiveness—that is, the capacity to spread from cell to cell—is also not an attribute that is restricted solely to viruses. On the other hand, the ability of cells to be freed from integrated virus under special environmental conditions is not a better criterion for distinguishing these biological elements from so called normal cellular components. The characterization of viruses as a taxonomic class might be achieved better on morphological ground. Notwithstanding the lack of any direct information on its intimate structure, there is a good evidence to consider σ as a true virus. On the other hand, σ shares with other insect viruses some common attributes that point to some sort of taxonomic relationship. Turning now to the stabilized condition, it must be admitted that the evidence is less compelling for denying mature virus any role in the viral genetic continuity through fly generations. The chapter concludes with a discussion on the effect of a rise in temperature on the host–virus relationships.
Infectious pancreatic necrosis virus (IPN) of salmonid fishes has been isolated and identified in suspect but normal-appearing stocks of adult brook trout (Salvelinus fontinalis), and thus a pattern for the epizootiology of the virus has been demonstrated. Virus titers as high as 106.5 ID50 were found in egg fluids from 7 of 12 fish tested. In contrast, egg homogenates contained much less virus; their maximum titer was 101.8 ID50. The presence of virus within the eggs, however, was not established. Viral neutralizing ability of serum from the same fish showed an inverse relationship to the presence of virus in “ovarian fluid.” The highest serum titers occurred in those fish from which little or no virus had been isolated.
A strain of Drosophila melanogaster in which the flies were infected with the heritable virus that causes CO2 sensitivity (sigma virus) was investigated in order to determine whether the flies suffered deleterious effects due to the infection. Eggs laid by virus-infected and virus-free females were counted and the resultant numbers of adult progeny were scored. It was found that deaths did occur among developing virus-infected progeny and that the deaths were in direct proportion to the logarithm of the number of infectious units inherited by the progeny. The fraction of surviving progeny was lowered from a value of 0.89 for the virus-free control line to 0.69 for the infected flies. The virus-infected flies that escaped death during development required 5–10 hours more than the noninfected control flies to develop from egg to adult.
The Western type of equine encephalomyelitis virus can be passed as an hereditary infection in a tick of the family Ixodidae, Dermacentor andersoni Stiles. Under experimental conditions, this virus has been carried in this tick for two successive generations, possibly for a third, passing certainly once, and possibly twice, from the female through the eggs to the larvae. The virus-carrying larval, nymphal, and adult stages of this tick, furthermore, are capable of infecting susceptible hosts when they are permitted to feed on them.
Colorado tick fever, also known as mountain fever and mountain tick fever, is a well-described, viral, tick-borne disease common to the Rocky Mountain region of the United States and Canada. The Rocky Mountain wood tick, Dermacentor andersoni, is the primary vector. The triad of high fever, severe myalgia, and headache is typical, but not specific. Although a self-limited disease in most cases, severe complications may occur. PCR techniques have been developed that allow the diagnosis to be established from the first day of symptoms. Ribavirin may merit consideration in the appropriate clinical setting.
Cold trypsin dispersion at pH 7.2 was used to obtain cultivable cells and cell groups from tissues of six species of fresh-water bony fishes, a frog, and a turtle. The cells readily attached to glass and were capable of at least limfted, and in some cases extended, division in media consisting of commercially available components.
An established line of fish cells has been propagated in vitro for 21 months and 48 subcultivations. Important characteristics
of the cells are described.
Excerpt
Since the discovery of CO² sensitivity in Drosophila by L'Héritier and Teissier (1937), a number of investigations have been carried out upon this phenomenon, with the aid of several workers. Without taking into account the historical order in which the facts were found, I shall try to make a synthesis of the whole subject in the perspective of the stage reached at present. I shall mention the names of my coworkers in connection with their chief contributions to our common knowledge, but I must apologize to every one of them for not referring to them in connection with each detail of their work.
CO² sensitivity is a physiological anomaly, sharply outlined and easy to recognize. Ordinary resistant flies can stand hours of contact with pure CO² without any permanent injury. When they awake from the narcosis which it produces, they at once recover complete mobility. On the contrary, sensitive flies...
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