Pseudo-vertical Transmission Research Articles

Impact of the gut microecology on Campylobacter presence revealed by comparisons of the gut microbiota from chickens raised on litter or in individual cages

BackgroundPoultry is the major reservoir of Campylobacter that contributes to human campylobacteriosis and threatens food safety. Litter contact has been linked to Campylobacter colonization, but the gut microecological impact underlying this link remains not fully clear. Here, we sought to investigate the impact of the gut microecology on the presence of Campylobacter by examining the microbiota in the duodenum, jejunum, ileum, ceca, and feces from chickens raised on commercial litter and in individual cages at 0–57 days of age.ResultsThrough litter contact, the presence of Campylobacter was found to benefit from microecological competition among Lactobacillus, Helicobacter, and genera that are halotolerant and aerobic or facultatively anaerobic in the upper intestine, such as Corynebacterium and Brachybacterium. The presence was also promoted by the increased abundance in obligate anaerobic fermentation microbes, especially members of the orders Clostridiales and Bacteroidales. The longitudinal analysis supported the vertical or pseudo-vertical transmission but suggested that colonization might occur immensely at 7–28 days of age. We observed a host genetic effect on the gut microecology, which might lead to increased heterogeneity of the microecological impact on Campylobacter colonization.ConclusionsThe findings advance the understanding of the gut microecological impact on Campylobacter presence in the chicken gut under conditions of litter contact and suggest that manipulations of the gut microecology, as well as the microbes identified in the Campylobacter association networks, might be important for the development of intervention strategies.

Viral and bacterial factors of mother-to-child transmission of hepatitis B virus.

Hepatitis B virus (HBV) infection is the tenth leading cause of death worldwide. Mother-to-child transmission of HBV occurring mainly at delivery remains one of the most common routes of infection in developing countries. One of the main challenges concerning HBV in Africa is to implement a prevention policy aiming at interrupting the cycle of pseudo-vertical transmission of this infection. The aim of this study was to assess the implication of certain bacterial and viral factors in mother-to-child transmission of HBV. This prospective study was conducted on 165 pregnant women carriers of HBV surface antigen (HBsAg) and their 169 newborns who attended care at the Gynecology Department of the University Hospital of Cocody. Serological, molecular, and bacteriological analyses were performed on blood samples and vaginal secretions. Mean viral load (VL) was 4.5±1.3log10 IU/ml, while mean HBsAg titres were 3.5±0.9log10 IU/ml. HBV DNA was found in vaginal secretions in 13.3% of mothers and in the blood of 10.3% of the newborns. Six bacterial species were identified in the vaginal discharge of pregnant women during labour before delivery. Staphylococcus aureus and Enterococcus faecalis were the most frequent species found in 23.0% and 13.9% of cases. Mothers positive for vaginal HBV DNA displayed higher plasma HBV DNA loads than negative mothers (6.2±1.6log10 IU/ml vs. 4.3±1.0log10 IU/ml, p<.0001). In conclusion, our study showed that presence of HBV DNA in vaginal secretions and the presence of S.aureus could play a role in mother-to-child transmission of HBV. HBV DNA detection in vaginal discharge represents a promising biomarker to identify newborns at risk of perinatal persistent infection.

On mycorrhizal individuality

This paper argues that a plant together with the symbiotic fungus attached to its roots, a mycorrhizal collective, is an evolutionary individual, and further, that mycorrhizal individuality has important implications for evolutionary theory. Theoretical individuation is defended and then employed to show that mycorrhizal collectives function as interactors according to David Hull’s replicator-interactor model of evolution by natural selection, and because they have the potential to engage in pseudo-vertical transmission, mycorrhizal collectives also function as Darwinian individuals, according to Peter Godfrey-Smith’s Darwinian Populations model of evolution by natural selection. Mycorrhizae in nature usually connect the roots of multiple plants, so mycorrhizal individuality entails the existence of overlapping evolutionary individuals, and because the potential to engage in pseudo-vertical transmission comes in degrees, it follows that these overlapping evolutionary individuals also come in degrees. I suggest here that the degree of evolutionary individuality in a symbiotic collective corresponds to its probability of reproducing with vertical or pseudo-vertical transmission. This probability constitutes a fourth parameter of graded Darwinian individuality in collective reproducers and warrants an update to Godfrey-Smith’s 3D model.

ESBL-Producing Klebsiella pneumoniae in the Broiler Production Chain and the First Description of ST3128.

ESBL-producing Klebsiella pneumoniae (K. pneumoniae) represent an increasing problem both in human and veterinary medicine. As SHV-2 - encoding K. pneumoniae were recently detected in the broiler production we were interested in investigating a possible transmission along the broiler production chain and furthermore, in evaluating their possible impact on human health. Therefore, 41 ESBL-producing K. pneumoniae originating from a parent flock, from the hatcherys' environment during the hatching of that parent flocks' chickens, and from an associated fattening flock were investigated on an Illumina Miseq. Whole genome sequences were analyzed concerning their MLST-type, cgMLST-type, genotypic and phenotypic resistance, plasmid profiles and virulence genes. Irrespective of the origin of isolation all investigated isolates were multi-drug resistant, harbored the same ESBL-gene blaSHV−2, shared the same sequence type (ST3128) and displayed 100% similarity in core genome multilocus sequence typing (cgMLST). In addition, in silico plasmid typing found several Inc/Rep types associated with ESBL-plasmids. Summarizing, identical clones of SHV-2—producing K. pneumoniae were detected in different stages of the industrial broiler production in one out of seven investigated broiler chains. This proves the possibility of pseudo-vertical transmission of multi-resistant human pathogens from parent flocks to hatcheries and fattening flocks. Furthermore, the importance of cross-contamination along the production chain was shown. Although the ESBL-producing K. pneumoniae clone detected here in the broiler production has not been associated with clinical settings so far, our findings present a potential public health threat.

A pantropically introduced tree is followed by specific ectomycorrhizal symbionts due to pseudo-vertical transmission.

Global trade increases plant introductions, but joint introduction of associated microbes is overlooked. We analyzed the ectomycorrhizal fungi of a Caribbean beach tree, seagrape (Coccoloba uvifera, Polygonacaeae), introduced pantropically to stabilize coastal soils and produce edible fruits. Seagrape displays a limited symbiont diversity in the Caribbean. In five regions of introduction (Brazil, Japan, Malaysia, Réunion and Senegal), molecular barcoding showed that seagrape mostly or exclusively associates with Scleroderma species (Basidiomycota) that were hitherto only known from Caribbean seagrape stands. An unknown Scleroderma species dominates in Brazil, Japan and Malaysia, while Scleroderma bermudense exclusively occurs in Réunion and Senegal. Population genetics analysis of S. bermudense did not detect any demographic bottleneck associated with a possible founder effect, but fungal populations from regions where seagrape is introduced are little differentiated from the Caribbean ones, separated by thousands of kilometers, consistently with relatively recent introduction. Moreover, dry seagrape fruits carry Scleroderma spores, probably because, when drying on beach sand, they aggregate spores from the spore bank accumulated by semi-hypogeous Scleroderma sporocarps. Aggregated spores inoculate seedlings, and their abundance may limit the founder effect after seagrape introduction. This rare pseudo-vertical transmission of mycorrhizal fungi likely contributed to efficient and repeated seagrape/Scleroderma co-introductions.

Extended-Spectrum-Beta-Lactamase- and Plasmid-Encoded Cephamycinase-Producing Enterobacteria in the Broiler Hatchery as a Potential Mode of Pseudo-Vertical Transmission.

ESBL-/pAmpC-producing enterobacteria occur frequently in broiler-fattening farms. Recent studies investigated the prevalence and possible transmission route of these bacteria in the broiler production chain. It seemed very likely that the hatcheries play an important role in transmission and/or contamination events. There are only few data on transmission investigations from a grandparent or parent flock to their offspring. However, reliable data on direct or indirect vertical transmission events in the hatchery are not available. Therefore, we conducted our study and intensively investigated the broiler hatching eggs from ESBL-/pAmpC-positive broiler parent flocks as well as the hatchlings and the environment of the hatchery.

Seasonal spread and control of Bluetongue in cattle

Bluetongue is a seasonal midge-borne disease of ruminants with economic consequences on herd productivity and animal trade. Recently, two new modes of transmission have been demonstrated in cattle for Bluetongue virus serotype 8 (BTV8): vertical and pseudo-vertical transmission. Our objective was to model the seasonal spread of BTV8 over several years in a homogeneous population of cattle, and to evaluate the effectiveness of vaccination strategies. We built a deterministic mathematical model accounting for the seasonality in vector abundance and all the modes of transmission. We proposed a counterpart of the basic reproduction number ( R 0) in a seasonal context ( R S ). Set A( t) is the number of secondary cases produced by a primary case introduced at time t. R S is the average of A( t). It is a function of midge abundance and vaccination strategy. We also used A ⁎, the maximum of A( t), as an indicator of the risk of an epidemic. Without vaccination, the model predicted a large first epidemic peak followed by smaller annual peaks if R S >1. When R S <1, small epidemics could occur if A ⁎ >1. Vaccination reduced R S and A ⁎ to less than one, but almost perfect vaccine efficacy and coverage were required to ensure no epidemics occurred. However, a lower coverage resulting in R S>1 could decrease infection prevalence. A further step would be to optimize vaccination strategies by targeting an appropriate period of the year to implement the vaccination.

Simulation modeling to evaluate the persistence of Mycobacterium avium subsp. paratuberculosis (MAP) on commercial dairy farms in the United States

We developed a series of deterministic mathematical models of Mycobacterium avium subsp. paratuberculosis (MAP) transmission on commercial US dairies. Our models build upon and modify models and assumptions in previous work to better reflect the pathobiology of the disease. Parameter values were obtained from literature for animal turnover in US dairy herds and rates of transition between disease states.The models developed were used to test three hypotheses. (1) Infectious transmission following intervention is relatively insensitive to the presence of high-shedding animals. (2) Vertical and pseudo-vertical transmission increases prevalence of disease but is insufficient to explain persistence following intervention. (3) Transiently shedding young animals might aid persistence.Our simulations indicated that multiple levels of contagiousness among infected adult animals in combination with vertical transmission and MAP shedding in infected young animals explained the maintenance of low-prevalence infections in herds. High relative contagiousness of high-shedding adult animals resulted in these animals serving as the predominant contributor to transmission. This caused elimination of infection in herds using the test-and-cull intervention tested in these simulations. Addition of vertical transmission caused persistence of infection in a moderately complicated model. In the most complex model that allowed age-based contacts, calf-to-calf transmission was required for persistence.

MUTUALISTIC STABILITY IN THE ARBUSCULAR MYCORRHIZAL SYMBIOSIS: EXPLORING HYPOTHESES OF EVOLUTIONARY COOPERATION

The 450-million-year-old symbiosis between the majority of land plants and arbuscular mycorrhizal fungi (AMF) is one of the most ancient, abundant, and ecologically important mutualisms on Earth. Yet, the evolutionary stability of mycorrhizal associations is still poorly understood, as it follows none of the constraints thought to stabilize cooperation in other well-known mutualisms. The capacity of both host and symbiont to simultaneously interact with several partners introduces a unique dilemma; detecting and punishing those exploiting the mutualism becomes increasingly difficult if these individuals can continue to access resources from alternative sources. Here, we explore four hypotheses to explain evolutionary cooperation in the arbuscular mycorrhizal symbiosis: (1) pseudo-vertical transmission and spatial structuring of plant and fungal populations leading to local adaptation of partners; (2) luxury resource exchange in which plants trade surplus carbon for excess fungal nutrients; (3) partner choice allowing partners to associate with better cooperators; and (4) host and symbiont sanctions which actively reward good partners and punish less cooperative ones. We propose that mycorrhizal cooperation is promoted by an exchange of surplus resources between partners and enforced through sanctions by one or both partners. These mechanisms may allow plant and fungal genotypes to discriminate against individuals employing exploitative strategies, promoting patterns of partner choice. Together these selection pressures provide a framework for understanding the stabilization of mycorrhizal cooperation over evolutionary time.

Understanding the dynamics of Salmonella infections in dairy herds: a modelling approach

There is evidence of variation in the infection dynamics of different Salmonella serotypes in cattle—ranging from transient epidemics to long term persistence and recurrence. We seek to identify possible causes of these differences. In this study we present mathematical models which describe both managed population dynamics and epidemiology and use these to investigate the effects of demographic and epidemiological factors on epidemic behaviour and threshold for invasion. In particular, when the system is perturbed by higher culling or pathogen-induced mortality we incorporate mechanisms to constrain the lactating herd size to remain constant in the absence of pathogen or to lie within a fairly small interval in the presence of pathogen. A combination of numerical and analytical techniques is used to analyse the models. We find that the epidemiologically dominating management group can change from the dry/lactating cycle to the weaned group with increasing culling rate. Pseudovertical transmission is found to have little effect on the invasion criteria, while indirect transmission has significant influence. Pathogen-induced mortality, recovery, immune response and pathogen removal are found to be factors inducing damped oscillations; variation in these factors between Salmonella serotypes may be responsible for some of the observed differences in within herd dynamics. Specifically, higher pathogen-induced mortality, shorter infectious period, more persistent immune response and more rapid removal of faeces result in a lower number of infectives and smaller epidemics but a greater tendency for damped oscillations.

A model appropriate to the transmission of a human food-borne pathogen in a multigroup managed herd

We describe a model of microparasite transmission within a multigroup managed farming system. The model was formulated to represent transmission of Escherichia coli O157 within a typical UK dairy herd and was used to suggest possible on-farm control strategies. The model includes birth, death, maturation, the dry/lactating cycle and various types of transmission (i.e. direct, pseudovertical (representing direct faecal–oral transmission between dam and calf within the first 48 h) and indirect (via free-living infectious units in the environment)). A combination of numerical and analytical techniques was used to analyse the model. We found that pseudovertical transmission and indirect transmission via infectious units in the ‘general’ environment can lead to more groups being affected, but otherwise have relatively little effect on the invasion criteria. To reduce infection within the herd, we suggest that efforts be directed at reducing the opportunity for group-specific indirect transmission—particularly within the weaned group.

Field Investigation of Mycoplasma gallisepticum Infections in House Finch (Carpodacus mexicanus) Eggs and Nestlings

We conducted a field study to investigate the occurrence of Mycoplasma gallisepticum (MG) in eggs and nestlings from nests of house finches (Carpodacus mexicanus). Forty-three nests were located between the months of April and August 1998 and were followed with one to three sampling efforts. Vitelline membrane of fresh eggs, whole embryos, or swabs from the choanal cleft or conjunctiva of nestlings were inoculated into mycoplasma broth for MG isolation and polymerase chain reaction (PCR) testing. No isolation of MG was made from 39 eggs or 110 nestlings sampled during the study. Pooled choanal and conjunctival swab samples from two broods of nestlings, however, tested positive for MG by PCR. None of the nestlings examined showed clinical signs of conjunctivitis, and no nestling mortality could be linked to MG infection. Serologic tests from 37 older nestlings were negative for antibodies to MG. The results suggest transmission of MG is occurring between breeding adults and their dependent offspring (pseudovertical transmission). Evidence supporting transovarian transmission of MG was not found in these house finches.

Modelling the Control of Bovine Tuberculosis in Badgers in England: Culling and the Release of Lactating Females

1. A simulation model was used to evaluate the effect of different levels of culling on six badger social groups in an attempt to reduce or eradicate TB infection from the population. Apart from fecundity, all model parameters were derived from a comprehensive study of a naturally-infected badger population in England. 2. Badger control was simulated using a trap-and-cull of 80% of all badgers in either two social groups (localized strategy) or all six social groups (wide area strategy). Lactating females were permitted to infect none or all of their young, to simulate the extremes of sow-to-cub (pseudo-vertical) transmission. Trapped lactating sows were either all released or all killed. 3. Simulations where all infected badgers can be correctly diagnosed were also run to determine the importance of an improved live test for TB. 4. In the absence of badger control, pseudo-vertical transmission increased the persistence and prevalence of TB in the simulated population. 5. A single control operation was capable of eradicating TB from the population only if all six badger social groups were subjected to culling. If only infected individuals were killed, disease eradication was possible without a marked increase in population extinction. If all individuals were killed, the increased level of disease eradication occurred as a result of an increase in population extinction. 6. Killing lactating sows had no effect on the medium-term prevalence (up to 20 years) of the disease and resulted only in a reduced persistence of TB when a wide area badger control strategy was used.

Epidemiology of Mycobacterium bovis infection in feral ferrets (Mustela furo) in New Zealand: II. Routes of infection and excretion

Detailed necropsies of 228 ferrets captured from eight areas in the North and South Islands provided material for an investigation into the epidemiology of tuberculosis in wild ferrets. Seventy-three of the 228 (32%) animals examined were diagnosed as tuberculous, by culture of pooled lymph nodes and detailed histopathological examination. The prevalence of bovine tuberculosis was 96% in 24 ferrets taken from areas in which tuberculous possums were common. None of 35 animals under 4 months of age were found to be infected, and the prevalence of infection was shown to rise with age, such that for each 6 month age increment there was a 2.8 times greater risk of becoming infected. The most common route of infection appeared to be via the alimentary tract, as 79% of 38 animals, in which the initial lesions could be reasonably determined, had these lesions associated with the digestive tract. Samples from potential sites of excretion from infected ferrets were submitted for culturing. The most common route of excretion was via the oral cavity, with M. bovis recovered from 15 of 64 (23%) oral swabs. Mychocterium bovis was also isolated from four of 64 (6%) tracheobronchial lavage samples, ten of 63 (16%) faecal samples, two of 29 (7%) urine samples and one of 8 (12.5%) mammary glands. The disease in ferrets appears to be principally maintained by ingestion of tuberculous carrion. Although a moderate number of ferrets excrete M. bovis orally, there appears to be only minor intraspecific transmission by bite wounding. The findings provided no evidence to support the occurrence of pseudo-vertical transmission.

Naturally occurring tuberculosis caused byMycobacterium bovisin brushtail possums (Trichosurus vulpecula): III. Routes of infection and excretion

Mycobacterium bovis was cultured from nine of 25 (36%) tracheal washings but not from any of 38 urine and 38 faecal samples from tuberculous possums cross-sectionally sampled from the wild. One of three tracheal washings, one of three urine samples and one of three faecal samples from terminally ill possums were culture-positive. The respiratory route is implicated as the major route of excretion of Mycobacterium bovis from naturally infected possums in horizontal transmission. Tuberculosis was observed in two young possums and was evidence of probable pseudo-vertical transmission via the respiratory route or ingestion of milk. Discharging fistulae were present in 22 of 71 (31%) cross-sectionally sampled tuberculous possums and were associated with relatively advanced disease. Although the frequent involvement of superficial lymphocentres in early stage disease could not be explained satisfactorily, the respiratory route was implicated as the main route of infection from indirect evidence.

The epidemiology of Mycobacterium bovis infections

Mycobacterium bovis has an exceptionally wide host range, but until recent years there was little concern about infection in species other than cattle and man. Diversification of farming enterprises has led to cognizance of the need for control in other domestic animals, notably deer. There has also been recognition that self-maintaining infection is present in wildlife hosts in some countries - notably the European badger in the United Kingdom and Ireland, the Australian brush-tailed possum in New Zealand, and various species of ungulates in limited areas of a number of countries. Although transmission of M. bovis can occur by a number of different routes, control measures imposed on cattle and to a lesser extent on other species have reduced a number of the routes to insignificance. Hence the vast preponderance of transmission within host species is now by the airborne route, and predominantly between species as well. Transmission of infection from badgers to cattle may be an exception, with evidence remaining equivocal about the relative importance of pasture contamination by excretion in badger urine and airborne transmission. In general, contamination of feed and pasture appears to be unimportant in transmission of the disease, because survival times of infective doses of organisms on fomites are relatively short under realistic conditions and because animals are not commonly exposed to a dose high enough to be infective by the alimentary route. Infection through the oro-pharyngeal mucous membrane may be significant, although the infective dose for this route is not known. While many species of animals can become infected with M. bovis, only a few act as maintenance hosts and the rest are spillover hosts in which infection is not self-maintaining. With the exception of cattle and deer, other species have become maintenance hosts only within part of their ecological range. For both badgers and possums, maintenance of infection within a local population is due to pseudo-vertical transmission from mother to young, and horizontal transmission linked to breeding activity. Transmission from possums to domestic animals appears to occur mainly during atypical behavioural interactions between the species, and this may well be important for badgers as well. Difficulties in controlling the disease adequately in domestic animals generally result from administrative problems since the necessary technical procedures are available and have been shown to be effective. Where there is interplay between infection in wildlife and domestic animals, eradication of the disease becomes impractical. Although herd prevalence will then be inescapably higher and characteristically clustered in patches in both time and space, reduction of the incidence rate to a low level in domestic stock is nevertheless achievable with current methods. Furhter reduction of incidence in the presence of a wildlife host should be possible through application of ecologically designed management procedures at farm level, but greater gains could be made if new control measures could be developed, especially vaccines.

The dynamics and control of bovine tuberculosis in possums.

A model for the dynamics of an infectious disease in a wild animal population is analysed. The model incorporates susceptible, infected but not infectious, and infectious classes, with no recovery from disease, density-dependent regulation of host birth and death rates, and pseudo-vertical transmission. The existence and local stability of equilibrium levels are determined. Expressions for the intensity of three alternative control measures - the culling, sterilization, and vaccination of host animals - required to eradicate the disease are obtained. Finally, the model is applied to possible control measures against bovine tuberculosis infection in possums in New Zealand.