Vertical Transmission Of Pathogens Research Articles

Vertical transmission of American foulbrood ( Paenibacillus larvae) in honey bees ( Apis mellifera)

The mode of transmission between hosts (horizontal versus vertical) of disease agents is important for determination of the evolution of virulence in pathogens. For disease management, it is imperative that the epidemiology of the disease is understood and pathogen transmission rates between hosts is a key factor for this understanding. Surprisingly little is known about transmission rates in honey bee pathology. We have studied the rate of vertical transmission of Paenibacillus larvae, the causative agent of American foulbrood (AFB) in honey bee colonies, as colonies reproduce by colony fission (swarming), by culturing for the spores from repetitive samples of adult bees. The results demonstrate vertical pathogen transmission to daughter swarms. The spore density declines over time in both mother colonies and daughter swarms if mother colonies do not exhibit clinical disease symptoms. Occasional positive samples more than a year post swarming, also in daughter swarms, indicate production of infectious spores from diseased larvae, without clinical disease observable by beekeepers, and/or maintenance of infective spores in the hive environment, allowing both horizontal and vertical transmission to be maintained. The results suggest that the virulence of AFB, being lethal at colony level in contrast to other bee diseases shaped by evolution, could be dependent on apicultural practices and that the pathogen probably would be maintained without causing frequent colony mortality in a natural system.

Implications of horizontal and vertical pathogen transmission for honey bee epidemiology

The degree to which a disease evolves to be virulent depends, in part, on whether the pathogen is transmitted horizontally or vertically. Eusocial insect colonies present a special case since the fitness of the pathogen depends not only on the ability to infect and spread between individuals within a colony, but also on the ability to spread to new individuals in other colonies. In honey bees, intercolony transmission of pathogens occurs horizontally (by drifting or robbing) and vertically (through swarming). Vertical transmission is likely the most important route of pathogen infection of new colonies. Theory predicts that this should generally select for benign host-parasite relation- ships. Indeed, most honey bee diseases exhibit low virulence. The only major exception is American foulbrood (AFB). In light of current ideas in evolutionary epidemiology, we discuss the implica- tions of horizontal and vertical pathogen transmission for virulence of AFB and other honey bee diseases.

A sensitive nested reverse transcriptase PCR assay to detect viable cells of the fish pathogen Renibacterium salmoninarum in Atlantic salmon (Salmo salar L.).

A nested reverse transcriptase (RT) PCR assay detected mRNA of the salmonid pathogen Renibacterium salmoninarum in samples of RNA extracts of between 1 and 10 cells. Total RNA was extracted from cultured bacteria, Atlantic salmon (Salmo salar L.) kidney tissue and ovarian fluid seeded with the pathogen, and kidney tissue from both experimentally challenged and commercially raised fish. Following DNase treatment, extracted RNA was amplified by both RT PCR and PCR by using primers specific for the gene encoding the major protein antigen of R. salmoninarum. A 349-bp amplicon was detected by polyacrylamide gel electrophoresis and silver stain. Inactivation of cultured bacteria by rifampin or erythromycin produced a loss of nested RT PCR mRNA detection corresponding to a loss of bacterial cell viability determined from plate counts but no loss of DNA detection by PCR. In subclinically diseased fish, nested RT PCR identified similar levels of infected fish as determined by viable pathogen culture. Higher percentages of fish testing positive were generated by PCR, particularly in samples from fish previously subjected to antibiotic chemotherapy where 93% were PCR positive, but only 7% were nested RT PCR and culture positive. PCR can generate false-positive data from amplification of target DNA from nonviable pathogen cells. Therefore, nested RT PCR may prove useful for monitoring cultured Atlantic salmon for the presence of viable R. salmoninarum within a useful time frame, particularly samples from broodstock where antibiotic chemotherapy is used prior to spawning to reduce vertical pathogen transmission.

The Structure of the Human Placenta: Implications for Initiating and Defending Against Virus Infections.

The architecture of the human placenta permits an extensive and intimate association between the maternal and fetal circulations. The fetal component consists of the elaborately branched villous tree, and this is bathed directly by maternal blood circulating within the intervillous space. Whilst this arrangement may favour metabolic exchange, it poses considerable risks for the vertical transmission of pathogens. Some features of placental structure can be considered potential impediments to transmission, such as the syncytial nature of the outer villous covering, the syncytiotrophoblast, and the ability of this tissue to secrete both nitric oxide and interferons. Other features may facilitate vertical transmission, including the lack of expression of MHC Class 1 antigens by the syncytiotrophoblast, and its vesicular and immunoglobulin transport pathways. More importantly, it is known that physical defects occur in the trophoblast layers at all stages in gestation. Whilst repair processes have been identified it must be assumed that pathogens or infected maternal white cells have access to the trophoblastic basement membrane, albeit transiently. The universal nature of these defects suggests that the trophoblast cannot be of paramount importance in the prevention of transmission. Rather, the defence mechanisms must lie either at the level of the basement membrane or within the villous core. There they may be represented by the resident macrophage population or the capillary endothelial cells and their junctional complexes. Consequently, the placenta should be viewed as an active rather than a passive barrier. Copyright 1997 by John Wiley & Sons, Ltd.

Survival of Arctic Grayling Eggs Water-Hardened in Various Concentrations of lodophor

Abstract Survival of eggs of Arctic grayling (Thymallus arcticus) following water hardening in various concentrations of an iodophor, povidone-iodine, solution was investigated. The treatment is effective in reducing the external bacterial load at the surface of the egg and is thought to reduce the risk of vertical transmission of pathogens from parent to offspring. However, in some cases, the use of iodophor during water hardening of salmon and trout eggs has resulted in significant egg losses. Treatment duration and concentrations similar to those commonly used during water hardening of eggs of other salmonid species were tested with Arctic grayling eggs. Water hardening in 50, 75, and 100 mg active iodine per liter resulted in significantly greater egg losses at eye-up than occurred when eggs were hardened in lake water. Mortality was highest in treatments with the strongest iodine concentrations.

The population dynamics of microparasites and their invertebrate hosts

We show how directly transmitted microparasites, broadly defined to include viruses, bacteria, protozoans and fungi, may regulate natural populations of invertebrate hosts. The study combines elements of conventional epidemiology (where the host population is assumed constant) with elements of prey-predator studies (which conventionally emphasize how prey and predator populations may be regulated by their interaction). To this end, we construct simple models embodying the essentials of the dynamical interaction between invertebrate hosts and their directly transmitted microparasites. In successive refinements, these models include the effects of recovery and disease-induced mortality, castration or diminished reproduction of infected hosts, vertical transmission, latent periods of infection, stress-related pathogenicity, the interplay between disease and other density-dependent constraints on host population growth, and free-living infective stages. In analysing the dynamical behaviour of these models, we focus on : the possible regulation of the host population by the parasite; the basic reproductive rate of the parasite, and the way in which it affects the dynamics and the evolution of the host-parasite association; and the threshold host density and its implications for endemic or epidemic maintenance of the infection. These are examined in the light of synoptic compilations of field and laboratory data on: birth rates (and disease-induced reduction thereof), natural death rates and disease-induced death rates of hosts; latent periods and efficiencies of vertical transmission of pathogens; the rate of production and lifetime of free-living infective stages; and some characteristics of long-term cycles and of epidemic outbreaks of disease in forest insects. In particular, our models suggest that the baculovirus and microsporidian infections of many temperate forest insects will tend to produce stable cycles in host abundance and in prevalence of infection, with periods in the range 5-12 years. Enough is known about the European larch budmoth and an associated granulosis virus for us to undertake a detailed comparison between theory and data that strongly suggests that the observed 9-10 year cycles are driven by the host-parasite interaction. We also discuss the possible control of invertebrate pest species by pathogens, showing how our models could guide laboratory or field studies, to help estimate whether a given pathogen is capable of regulating the target pest population, and, if so, roughly what quantity is needed to effect a specific level of (local) control. Throughout, the emphasis is on the biological ingredients of the models, and on the biological conclusions to be drawn; mathematical details are given in appendixes.

Calculation of Vertical Transmission Rates of Infection, Illustrated with Data on an Aphid-Borne Virus

Previous articleNext article No AccessLetters to the EditorsCalculation of Vertical Transmission Rates of Infection, Illustrated with Data on an Aphid-Borne VirusPaul E. M. Fine and Edward S. SylvesterPaul E. M. Fine Search for more articles by this author and Edward S. Sylvester Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 112, Number 986Jul. - Aug., 1978 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/283322 Views: 2Total views on this site Citations: 9Citations are reported from Crossref Copyright 1978 The University of ChicagoPDF download Crossref reports the following articles citing this article:Caetano Souto-Maior Host–Symbiont–Pathogen–Host Interactions: Wolbachia, Vector-Transmitted Human Pathogens, and the Importance of Quantitative Models of Multipartite Coevolution, (Jul 2015): 207–230.https://doi.org/10.1007/978-3-319-16345-1_8Rinaldo B. Schinazi Horizontal versus vertical transmission of parasites in a stochastic spatial model, Mathematical Biosciences 168, no.11 (Nov 2000): 1–8.https://doi.org/10.1016/S0025-5564(00)00043-2G. Lovison, S.D. Gore, G.P. Patil 4 Design and analysis of composite sampling procedures: A review, (Jan 1994): 103–166.https://doi.org/10.1016/S0169-7161(05)80006-9Laurence D. Hurst Parasite diversity and the evolution of diploidy, multicellularity and anisogamy, Journal of Theoretical Biology 144, no.44 (Jun 1990): 429–443.https://doi.org/10.1016/S0022-5193(05)80085-2Keizi Kiritani, Fusao Nakasuji, Shun’ichi Miyai Systems Approaches for Management of Insect-Borne Rice Diseases, (Jan 1987): 57–80.https://doi.org/10.1007/978-1-4612-4688-6_3Paul E. M. Fine Vertical Transmission of Pathogens of Invertebrates, (Jan 1984): 205–241.https://doi.org/10.1007/978-1-4615-9388-1_10Milton W. Loyer Bad Probability, Good Statistics, and Group Testing for Binomial Estimation, The American Statistician 37, no.11 (Feb 1983): 57–59.https://doi.org/10.1080/00031305.1983.10483091L.N. Payne, N. Bumstead Theoretical considerations on the relative importance of vertical and horizontal transmission for the maintenance of infection by exogenous avian lymphoid leukosis virus, Avian Pathology 11, no.44 (Jan 2008): 547–553.https://doi.org/10.1080/03079458208436129C A Mims Vertical transmission of viruses, Microbiological Reviews 45, no.22 (Jun 1981): 267–286.https://doi.org/10.1128/mr.45.2.267-286.1981