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PubMed2005

Transmission dynamics of Taenia solium and potential for pig-to-pig transmission.

Taenia solium taeniasis/cysticercosis is one of few potentially eradicable infectious diseases and is the target of control programs in several countries. The larval stage of this zoonotic cestode invades the human brain and is responsible for most cases of adult-onset epilepsy in the world. Our current understanding of the life cycle implicates humans as the only definitive host and tapeworm carrier, and thus the sole source of infective eggs that are responsible for cysticercosis in both human and pigs through oral-faecal transmission. Here we review transmission dynamics of porcine cysticercosis including an alternative pig-to-pig route of transmission, previously not suspected to exist. Second-hand transmission of T. solium eggs could explain the overdispersed pattern of porcine cysticercosis, with few pigs harbouring heavy parasite burdens and many more harbouring small numbers of parasites.

Animals↗
PubMed2004

Estimating transmission parameters of F4+ E. coli for F4-receptor-positive and -negative piglets: one-to-one transmission experiment.

F4+ Escherichia coli is an important agent of post-weaning diarrhoea in piglets. Piglets that express an adhesion site for F4+ E. coli in their small intestine (F4R+) shed higher numbers of F4+ E. coli than piglets lacking this site (F4R-). We hypothesized that F4R+ piglets are more infectious and more susceptible for F4+ E. coli. This implies that in populations with F4R+ and F4R- piglets, the transmission would be dependent on the frequency of both types of animals. To quantify the difference in infectiousness and susceptibility, a one-to-one transmission experiment was performed with 20 pairs consisting of one inoculated and one contact piglet. Based on the contact infections observed, transmission parameters were estimated with generalized linear models. F4R+ piglets were infectious for other piglets and the reproduction ratio (R0) for homogeneous F4R+ populations, that is the average number of secondary infections that one F4R+ pig will cause during its entire infectious period in a population of susceptible F4R+ individuals only, was estimated as 7.1. F4R+ piglets were more susceptible than F4R- piglets and reducing the fraction of F4R+ piglets of a population will reduce transmission. It was calculated that in order to prevent major outbreaks of F4+ E. coli (R0 < 1), the fraction of F4R+ piglets must be lower than 0.14.

Adhesins, Escherichia coli↗
PubMed1999

[Experimental transmission of Crimean-Congo hemorrhagic fever virus: role of 3 vector species in the maintenance and transmission cycles in Senegal].

In this article, we published the role of three species of ticks Amblyomma variegatum (Fabricius, 1974), Hyalomma marginatum rufipes (Koch, 1844) and Hyalomma truncatum (Koch, 1844) in the maintenance and transmission of the CCHF virus. The imagos of these species were infected by intracoelomic route. Vertical transmission (transtasial and transovarial) and horizontal transmission for different stases were studied by isolation on newborn mice, polymerase chain reaction, indirect immunofluorescence and ELISA. Our results proved that 15 days after inoculation, infection rates of 100% were noted with Hyalomma marginatum rufipes and Hyalomma truncatum. This rate is about 60% for Amblyomma variegatum. The imagos of the three species infected have transmitted the virus to their host during blood feeding (100%). A high transovarial transmission for Hyalomma marginatum rufipes and Hyalomma truncatum were observed (respectively 53 and 50%). This rate is about 12% for Amblyomma variegatum. The tick infection does not persist up to the first generation for the three species studied. Ticks are temporary reservoirs vectors but not permanent reservoirs of CCHF virus.

Animals↗
PubMedDate not supplied

Age trends in transmissible and non-transmissible components of family resemblance for stature.

Yearly measurements of recumbent length and stature on participants in the Fels Longitudinal Study of Growth and their first-degree relatives were submitted to path analysis. Using a model consistent with simple polygenic inheritance, two parameters were estimated at each age: t2 or transmissibility, and s, or non-transmissible sibling resemblance. Transmissibility showed no long-term age trends, whereas non-transmissible sibling resemblance declined steadily from age four years to the late teens. The factors controlling family resemblance for stature (genes and common family environment) make different contributions at different points in the growth cycle of these family members. These differences are more discernable in the Fels data because all family members, including parents, are measured at the same age throughout childhood.

Adolescent↗
PubMed1967

Experimental transmission of influenza virus infection in mice. 3. Differing effects of immunity induced by infection and by inactivated influenza virus vaccine on transmission of infection.

Immunization of mice by infection or intraperitoneal injection with homotypic A(2), heterotypic A(0), or recombinant A(0)A(2) virus have differing effects on transmission of influenza A(2) virus infection. Immunization by infection with A(2) virus resulted in refractoriness to reinfection either by artificial aerosols or by exposure to infected cage-mates. Immunization by inoculation with inactivated A(2) virus vaccine resulted in a decreased susceptibility to transmitted infection in immunized contacts, but following A(2) virus challenge, transmission of infection by immunized infectors was not altered. Immunization by infection with influenza A(0) virus or recombinant A(0)A(2) virus resulted in a decreased susceptibility to transmitted A(2) virus infection in immunized contacts, and to decreased transmission after A(2) virus infection in immunized infector mice. These differing effects on transmission of infection are attributed to differences in specific local immunologic responses following the various immunization procedures.

Animals↗
PubMed2004

Familial transmission of mood disorders: convergence and divergence with transmission of suicidal behavior.

OBJECTIVE: Both mood disorder and suicidal behavior are familial. In this study, the authors examine the factors associated with the familial transmission of these two related conditions to learn which are shared or unique risk factors for familial transmission. METHOD: The 285 offspring of 141 probands with mood disorder were studied. Proband and offspring characteristics associated with offspring mood disorder were examined by univariate statistics, logistic and Cox regression, and path analysis. RESULTS: Parental history of sexual abuse was associated with an increased risk of offspring mood disorder. The relationship between parent sexual abuse and offspring mood disorder was mediated by offspring impulsive aggression, sexual abuse, and anxiety disorder. In offspring, higher levels of impulsive aggression were associated with earlier age at onset of mood disorder. Offspring suicide attempt was mainly related to offspring mood disorder, with additional contributions from offspring sexual abuse and impulsive aggression. CONCLUSIONS: The pathways associated with the familial transmission of mood disorder and of suicide attempt are similar but not identical. Prevention of early-onset mood disorder by targeting high- risk families may help to prevent the transmission of suicidal behavior. Because these data are cross-sectional, these results must be confirmed by prospective follow-up.

Adolescent↗
PubMed1995

Antigenic analysis of nematode-transmissible and non-transmissible isolates of tobacco rattle tobravirus using monoclonal antibodies.

Murine monoclonal antibodies (MAbs) were produced against a nematode non-transmissible isolate of tobacco rattle tobravirus (TRV-PLB). Two of the MAbs (SCR 80 and 81) did not react with the serologically closely related isolate TRV-PPK20 (both isolates belong to the PRN serotype), which is readily transmissible by nematodes. When further isolates of the PRN serotype were tested, all the non-transmissible ones reacted with these two MAbs, but so also did some of those that are readily transmissible. SCR 80 and 81 were able to trap TRV-PLB particles onto electron microscope grids and reacted with metatopes located near the C terminus of the particle protein. The epitope recognized by SCR 81 was discontinuous. The MAbs that reacted with both TRV-PLB and TRV-PPK20 recognized either continuous cryptotopes (SCR 78) or discontinuous neotopes (SCR 79 and 82).

Amino Acid Sequence↗
PubMed1995

Transmission by aphids of a naturally non-transmissible plum pox virus isolate with the aid of potato virus Y helper component.

Two Spanish plum pox virus (PPV) isolates, 5.15 and 3.3, were used in transmission experiments involving the aphid vector Myzus persicae, with woody and herbaceous host plants. These isolates differ in the size of their coat protein (CP) and sequence analysis revealed that isolate 3.3 has a 15 amino acid deletion near the N terminus of the CP, affecting the same positions as in a previously reported non-aphid-transmissible PPV isolate from Germany. Aphid transmission experiments showed that isolate 5.15 was transmitted from infected plants whereas isolate 3.3 was not. In contrast, both isolates were readily aphid-transmitted when acquired through artificial membranes from purified virus preparations supplemented with purified helper component (HC) obtained from potato virus Y-infected plants. This indicates that non-transmissibility of isolate 3.3 may be due to a defect in the HC rather than in the CP.

Amino Acid Sequence↗
PubMed2006

Incorporation of system resolution compensation (RC) in the ordered-subset transmission (OSTR) algorithm for transmission imaging in SPECT.

In order to reconstruct attenuation maps with improved spatial resolution and quantitative accuracy, we developed an approximate method of incorporating system resolution compensation (RC) in the ordered-subset transmission (OSTR) algorithm for transmission reconstruction. Our method approximately models the blur caused by the finite intrinsic detector resolution, the nonideal source collimation and detector collimation. We derived the formulation using the optimization transfer principle as in the derivation of the OSTR algorithm. The formulation includes one forward-blur step and one back-blur step, which do not severely slow down reconstruction. The formulation could be applicable to various transmission geometries, such as point-source, line-source, and sheet-source systems. Through computer simulations of the MCAT phantom and transmission measurements of the air-filled Data Spectrum Deluxe single photo emission computed tomography (SPECT) Phantom on a system which employed a cone-beam geometry and a system which employed a scanning-line-source geometry, we showed that incorporation of RC increased spatial resolution and improved the quantitative accuracy of reconstruction. In simulation studies, attenuation maps reconstructed with RC correction improved the quantitative accuracy of emission reconstruction.

Algorithms↗
PubMed1995

Inhibitory activity in saliva of cell-to-cell transmission of human T-cell lymphotropic virus type 1 in vitro: evaluation of saliva as an alternative source of transmission.

Human T-cell lymphotropic virus type 1 (HTLV-1) is known to be transmitted vertically through breastfeeding and horizontally by blood transfusion and sexual contact. Our intervention study has suggested the presence of additional alternative maternal transmission pathways. To explore the possibility of transmission through saliva, we used PCR to quantify the HTLV-1 provirus in saliva samples from 18 carrier mothers and 10 patients with HTLV-1-associated myelopathy/tropical spastic paraparesis. The provirus was detected in 60 and 90%, respectively, of the samples, with estimated copy numbers in the range of 10 to 10(4)/ml. However, the saliva, regardless of the presence or absence of antibodies to the virus, showed a strong tendency to inhibit the cell-to-cell transmission of HTLV-1 in vitro, as examined by a syncytium inhibition assay. The natural inhibitory activity in saliva of seronegative volunteers was heat sensitive, and most of the activity was recovered by ultrafiltration in the fraction of macromolecules with a molecular weight of more than 100,000. In addition to this natural activity, saliva of HTLV-1-infected individuals contained immunoglobulin G molecules capable of neutralizing syncytium formation. These results strongly suggested that HTLV-1-infected cells in the carriers' saliva, which contains neutralizing antibodies in addition to the natural activity inhibiting cell-to-cell viral infection, barely transmit the virus. Transmission of HTLV-1 through the saliva would thus seem to be rare, if it occurs at all.

Adult↗
PubMed2000

Adaptation and selection of prion protein strain conformations following interspecies transmission of transmissible mink encephalopathy.

Interspecies transmission of the transmissible spongiform encephalopathies (TSEs), or prion diseases, can result in the adaptation and selection of TSE strains with an expanded host range and increased virulence such as in the case of bovine spongiform encephalopathy and variant Creutzfeldt-Jakob disease. To investigate TSE strain adaptation, we serially passaged a biological clone of transmissible mink encephalopathy (TME) into Syrian golden hamsters and examined the selection of distinct strain phenotypes and conformations of the disease-specific isoform of the prion protein (PrP(Sc)). The long-incubation-period drowsy (DY) TME strain was the predominate strain, based on the presence of its strain-specific PrP(Sc) following interspecies passage. Additional serial passages in hamsters resulted in the selection of the hyper (HY) TME PrP(Sc) strain-dependent conformation and its short incubation period phenotype unless the passages were performed with a low-dose inoculum (e.g., 10(-5) dilution), in which case the DY TME clinical phenotype continued to predominate. For both TME strains, the PrP(Sc) strain pattern preceded stabilization of the TME strain phenotype. These findings demonstrate that interspecies transmission of a single cloned TSE strain resulted in adaptation of at least two strain-associated PrP(Sc) conformations that underwent selection until one type of PrP(Sc) conformation and strain phenotype became predominant. To examine TME strain selection in the absence of host adaptation, hamsters were coinfected with hamster-adapted HY and DY TME. DY TME was able to interfere with the selection of the short-incubation HY TME phenotype. Coinfection could result in the DY TME phenotype and PrP(Sc) conformation on first passage, but on subsequent passages, the disease pattern converted to HY TME. These findings indicate that during TSE strain adaptation, there is selection of a strain-specific PrP(Sc) conformation that can determine the TSE strain phenotype.

Adaptation, Physiological↗
PubMed2003

Is maternal transmission of coronary heart disease risk stronger than paternal transmission?

OBJECTIVE: To test whether intergenerational transmission of coronary heart disease (CHD) to offspring is greater from the mother than from the father, the association between parental history of CHD and coronary mortality in male offspring was examined. DESIGN: Prospective cohort study with 43 years of follow up. SETTING: University of Glasgow. PARTICIPANTS: Male students (n = 8402) aged 16-30 years when examined in 1948 to 1968. MAIN OUTCOME MEASURE: Fatal CHD. MAIN RESULTS: Of the 8402 men studied, 615 (7.3%) reported a history of CHD in at least one of the parents: 479 (5.8%) for fathers only, 124 (1.6%) for mothers only, and a further 12 (0.2%) for both their parents. During follow up, 373 (4.4%) men died of CHD. Parental history of disease was associated with fatal CHD and controlling for personal risk factors such as cigarette smoking, body mass index, systolic blood pressure, and father's social class did not attenuate this relation. The fully adjusted hazard ratios were 1.53 (95% confidence interval (CI) 1.08 to 2.18), 1.19 (95% CI 0.61 to 2.32), and 8.65 (95% CI 2.65 to 28.31) for father only, mother only, and both parents with CHD, respectively, compared with men whose parents did not have CHD. There was some evidence for interaction between parental histories (p = 0.049), with particularly high risk if both parents reported a history of CHD. CONCLUSIONS: This study found no differential transmission of CHD. Paternal history of CHD was at least as important as maternal history. Data from other comparable cohorts provide no consistent evidence of differential transmission. Intergenerational transmission of CHD does not appear to have differential effects between mothers and fathers.

Adolescent↗
PubMed2006

Transmission potential of primary pneumonic plague: time inhomogeneous evaluation based on historical documents of the transmission network.

BACKGROUND: The transmission potential of primary pneumonic plague, caused by Yersinia pestis, is one of the key epidemiological determinants of a potential biological weapon, and requires clarification and time dependent interpretation. METHOD: This study estimated the reproduction number and its time dependent change through investigations of outbreaks in Mukden, China (1946), and Madagascar (1957). Reconstruction of an epidemic tree, which shows who infected whom, from the observed dates of onset was performed using the serial interval. Furthermore, a likelihood based approach was used for the time inhomogeneous evaluation of the outbreaks for which there was scarcity of cases. RESULTS: According to the estimates, the basic reproduction number, R(0), was on the order of 2.8 to 3.5, which is higher than previous estimates. The lower 95% confidence intervals of R(0) exceeded unity. The effective reproduction number declined below unity after control measures were introduced in Mukden, and before the official implementation in Madagascar. CONCLUSION: While the time course of the latter outbreak could be explained by intrinsic factors and stochasticity in this remote and scarcely populated area, the former in Mukden suggests the possible continued chains of transmission in highly populated areas. Using the proposed methods, the who infected whom information permitted the evaluation of the time inhomogeneous transmission potential in relation to public health measures. The study also tackles the problem of statistical estimation of R(0) based on similar information, which was previously performed simply by counting the number of secondary transmissions regardless of time.

China↗
PubMed2004

Criminalization of HIV transmission: can doctors be liable for the onward transmission of HIV?

The English Court of Appeal has recently confirmed that the reckless transmission of HIV can amount to a criminal offence, following on from a similar development in Scotland in 2001. This development has led to some concern as to whether doctors could, in certain circumstances, themselves be liable for the onward transmission of HIV by a patient. This article reviews the current scope of the criminal law, before considering the law on liability for onward transmission in the UK. It concludes that civil liability (liability in damages) for onward transmission will be imposed only in unusual cases, and probably only where a doctor has failed to discharge his or her duty of care towards one of his or her own patients. Criminal liability is perhaps theoretically possible but exceptionally unlikely.

Confidentiality↗
PubMedDate not supplied

Inter-relation of sylvatic and domestic transmission of Trypanosoma cruzi in areas with and without domestic vectorial transmission in Minas Gerais, Brazil.

During the period 1980-1986, we captured triatomine bugs and mammalian reservoir hosts from sylvatic and domestic situations in different municipalities of the State of Minas Gerais. Trypanosoma cruzi was isolated from captured bugs, mammals and patients. After cultivation in LIT medium, the electrophoretic enzyme profiles were determined. We obtained a total of 32 parasite isolates from regions with active domestic transmission, and 24 isolates from areas under control. For the first areas the results suggest introduction of T. cruzi from sylvatic habitats, through incursion of infected opossums and/or sylvatic T. sordida, which appears to have given rise to at least one acute human infection. Of particular interest is the finding of sylvatic opossums and a T. sordida nymph infected with ZB, that could indicate return of parasites from chronic human infections to sylvatic transmission cycles. For the areas under control we also interpret the results as interaction between sylvatic and domestic cycles of transmission, here through the invasion of houses by bugs carrying the Z1 zymodeme from the sylvatic environment. The Multivariate Correspondence Analysis gives a spatial description between the different parasite isolates and confirms the existence of a bridge in the opposite direction in the region with active vectorial transmission including the exporting of Z2 through the peridomestic environment into the sylvatic cycle. For the other areas this bridge corresponds especially to Panstrongylus megistus, importing Z1 into the domestic environment.

Animals↗
PubMed1998

Gametocyte infectivity by direct mosquito feeds in an area of seasonal malaria transmission: implications for Bancoumana, Mali as a transmission-blocking vaccine site.

Infectivity of gametocytemic volunteers living in Bancoumana, a village 60 km from Bamako, Mali, was determined by direct feeds of laboratory-reared Anopheles gambiae s. l. Gametocytemic adolescents (10-18 years old) were as infectious to mosquitoes as younger volunteers and appear to be a more suitable population for testing transmission-blocking efficacy as compared with adults (> 18 years old). To begin to validate the membrane-feeding assay, sera collected from these same volunteers were subjected to a standard membrane-feeding assay. The data suggest that areas with intense but seasonal transmission might be feasible sites for testing transmission-blocking vaccines because of the high gametocytemic rates, high mosquito infectivity rates, and lack of pre-existing humoral-mediated transmission-blocking activity. The differences observed between field-based direct mosquito feeds and laboratory-based membrane feeding assays suggests that caution be used in interpreting Phase I study results in which laboratory-based membrane-feeding assays are used as a surrogate for vaccine efficacy.

Adolescent↗
PubMed1992

Simultaneous acquisition of emission and transmission data for improved thallium-201 cardiac SPECT imaging using a technetium-99m transmission source.

Transmission computed tomography (TCT) data provides useful complementary information to single-photon emission computed tomography (SPECT) reconstructions, especially for cardiac studies. In particular, TCT data has been used to correct for nonuniform attenuation in the chest. Typically the transmission data are acquired in a separate acquisition, but simultaneous acquisition is preferable both to save time and to avoid difficulties involved with registration. In this work, we present a technique for simultaneously acquiring 201Tl SPECT and TCT data using a 99mTc sheet source that requires only minor equipment modifications. The use of these isotopes results in cross-contamination of the emission and transmission data. We present a practical technique to compensate for this contamination using post-acquisition image processing. This technique was evaluated by performing phantom and patient studies. The resulting images compare well with data obtained from separate emission and transmission studies.

Heart↗
PubMed1992

Mother-to-child transmission of human immunodeficiency virus type 1: risk of infection and correlates of transmission.

One thousand eight hundred eighty-seven children born to human immunodeficiency virus type 1 (HIV-1) seropositive mothers, including 1045 infants prospectively followed up from birth, were studied. Intravenous drug use was the most frequent maternal risk factor, although the percentage of women infected by sexual contact increased from 5.8% in 1985 to 28.5% in 1990. Of the 551 first children followed up from birth and older than 15 months of age, 101 (18.3%) acquired infection and seroconverted to HIV-1. Another 31 (5.6%) asymptomatic seronegative children showed the presence of viral markers, for an apparent mother-to-offspring transmission rate of 23.9%. Overlapping results were seen in 22 second-born children followed up from birth. Of 59 sibships with definite infection status, when the first child was infected, 14 (40%) of 35 second children were infected, whereas when the first child was not infected, only 2 of 24 (8.3%) second children were infected. Discordance in HIV-1 transmission was found in 1 of 18 pairs of twins. Univariate and multivariate analyses of possible risk factors for HIV-1 transmission performed on the entire population of children and in the cohort of those followed up from birth were basically in agreement in indicating that the development of symptoms in the mother before delivery and breast-feeding (indeed adopted in only 22 infants in whom HIV-1 infection was identified at birth) were significantly and independently associated with a higher transmission rate. In addition, girls were more frequently infected than boys.(ABSTRACT TRUNCATED AT 250 WORDS)

Breast Feeding↗