Search results for "infectivity"
showing 10 items of 103 documents
Equines as reservoirs of human fascioliasis: transmission capacity, epidemiology and pathogenicity inFasciola hepatica-infected mules
2020
AbstractFascioliasis is a zoonotic disease caused by liver flukes transmitted by freshwater lymnaeid snails. Donkey and horse reservoir roles have been highlighted in human endemic areas. Liver fluke infection in mules has received very limited research. Their role in disease transmission, epidemiological importance andFasciola hepaticapathogenicity are studied for the first time. Prevalence was 39.5% in 81 mules from Aconcagua, and 24.4% in 127 from Uspallata, in high-altitude areas of Mendoza province, Argentina. A mean amount of 101,242 eggs/mule/day is estimated. Lymnaeids from Uspallata proved to belong to ribosomal DNA internal transcribed spacer (ITS) markers ITS-1 and ITS-2 combined…
Isolation and characterization of Vibrio parahaemolyticus causing infection in Iberian toothcarp Aphanius iberus
1999
High mortality among laboratory cultured Iberian toothcarp Aphanius iberus occurred in February 1997 in Valencia (Spain). The main signs of the disease were external haemorrhage and tail rot. Bacteria isolated from internal organs of infected fish were biochemically homogeneous and identified as Vibrio parahaemolyticus. The bacteria were haemolytic against erythrocytes from eel Anguilla anguilla, amberjack Seriola dumerili, toothcarp A. iberus and humans, and were Kanagawa-phenomenon-negative. Infectivity tests showed that the virulence for A. iberus was dependent on salinity. Finally, all strains were virulent for amberjack and eel.
Heterocyclic Diamines with Leishmanicidal Activity.
2021
Leishmaniasis is one of the world's most neglected diseases with a worldwide prevalence of 12 million people. There are no effective human vaccines for its prevention, and outdated drugs hamper treatment. Therefore, research aimed at developing new therapeutic tools to fight leishmaniasis remains a crucial goal today. With this purpose in mind, here, we present 10 new compounds made up by linking alkylated ethylenediamine units to pyridine or quinoline heterocycles with promising in vitro and in vivo efficacy against promastigote and amastigote forms of Leishmania infantum, Leishmania donovani, and Leishmania braziliensis species. Three compounds (2, 4, and 5) showed a selectivity index muc…
Presence of Pomphorhynchus laevis in Salamandra salamandra
1995
AbstractInfection of Salamandra salamandra larvae (Amphibia: Urodela) with the fish acanthocephalan Pomphorhynchus laevis was detected in a fish-free mountain brook. Gammarus fossarum was found to be the intermediate host. The parasites were probably inadvertently introduced through fish breeding practices. Evidence was obtained that Pomphorhynchus laevis persists, at least for several months, in postmetamorphic fire salamanders.
Local adaptation of a holoparasitic plant, Cuscuta europaea: variation among populations
2000
Locally adapted parasites have higher infectivity and/or fitness on sympatric than on allopatric hosts. We tested local adaptation of a holoparasitic plant, Cuscuta europaea, to its host plant, Urtica dioica. We infected hosts from five sites with holoparasites from the same five sites and measured local adaptation in terms of infectivity and parasite performance (biomass) in a reciprocal cross-infection experiment. The virulence of the parasite did not differ between sympatric and allopatric hosts. Overall, parasites had higher infectivity on sympatric hosts but infectivity and parasite performance varied among populations. Parasites from one of the populations showed local adaptation in t…
Significance and relevance of serum preS1 antigen detection in wild-type and variant hepatitis B virus (HBV) infections
1993
These studies assessed whether the serum expression of preS1 antigen could be a useful HBV marker for monitoring the progress of antiviral therapy in the treatment of chronic active hepatitis B (CAH-B) virus infections. Our findings indicate that: 1) the rearrangements we observed in the preS region of mutated HBV DNA molecules during chronic infection did not effect the preS1 sequence (21–47) critical for HBV infectivity; 2) the persistence or even the rebound of preS1 antigen expression during follow-up in responders to antiviral therapy may indicate virus persistence, suggesting the possibility of relapse through wild-type HBV or the emergence of HBV variants following the immunoeliminat…
Manipulation of fish host by eye flukes in relation to cataract formation and parasite infectivity
2005
Trophically transmitted parasites may predispose infected hosts to predation by altering host behaviour, which can be either an adaptation of the parasites to enhance transmission to the next hosts in the life cycle or a nonadaptive side-effect of infection. In an experimental study, we investigated host manipulation by Diplostomum spathaceum (Trematoda), an eye fluke of fish, to evaluate its adaptive value as a parasite strategy to increase transmission efficiency to bird hosts. The parasite induces cataract formation in the lenses of fish eyes, and predisposes fish to predation by reducing their escape response. We examined the effect of developmental stage and the number of parasites on …
Is the Rigidity of SARS-CoV-2 Spike Receptor-Binding Motif the Hallmark for Its Enhanced Infectivity? Insights from All-Atom Simulations
2020
The severe acute respiratory syndrome coronavirus (SARS-CoV-2) pandemic is setting the global health crisis of our time, causing a devastating societal and economic burden. An idiosyncratic trait of coronaviruses is the presence of spike glycoproteins on the viral envelope, which mediate the virus binding to specific host receptor, enabling its entry into the human cells. In spite of the high sequence identity of SARS-CoV-2 with its closely related SARS-CoV emerged in 2002, the atomic-level determinants underlining the molecular recognition of SARS-CoV-2 to the angiotensin-converting enzyme 2 (ACE2) receptor and, thus, the rapid virus spread into human body, remain unresolved. Here, multi-m…
Latency versus persistence or intermittent recurrences: Evidence for a latent state of murine cytomegalovirus in the lungs
1997
The state of cytomegalovirus (CMV) after the resolution of acute infection is an unsolved problem in CMV research. While the term "latency" is in general use to indicate the maintenance of the viral genome, a formal exclusion of low-level persistent productive infection depends on the sensitivity of the assay for detecting infectious virus. We have improved the method for detecting infectivity by combining centrifugal infection of permissive indicator cells in culture, expansion to an infectious focus, and sensitive detection of immediate-early RNA in the infected cells by reverse transcriptase PCR. A limiting-dilution approach defined the sensitivity of this assay. Infectivity was thereby …
Identifying a key host in an acanthocephalan-amphipod system.
2015
SUMMARYTrophically transmitted parasites may use multiple intermediate hosts, some of which may be ‘key-hosts’, i.e. contributing significantly more to the completion of the parasite life cycle, while others may be ‘sink hosts’ with a poor contribution to parasite transmission. Gammarus fossarum and Gammarus roeseli are sympatric crustaceans used as intermediate hosts by the acanthocephalan Pomphorhynchus laevis. Gammarus roeseli suffers higher field prevalence and is less sensitive to parasite behavioural manipulation and to predation by definitive hosts. However, no data are available on between-host differences in susceptibility to P. laevis infection, making it difficult to untangle the…