Studies on the effects of cercarial concentration and length of exposure on the infection of mice by St Lucian Schistosoma mansoni cercariae in a natural running-water habitat

Parasitology ◽  
1974 ◽  
Vol 68 (2) ◽  
pp. 155-159 ◽  
Author(s):  
Edward Suchart Upatham
Keyword(s):  
Schistosoma Mansoni ◽  
Infection Rate ◽  
Worm Burden ◽  
Running Waters ◽  
Direct Proportion ◽  
Infection Rates ◽  
Domestic Water ◽  
Running Water ◽  
Long Period ◽  
Water Washing

The effects of cercarial concentration and length of exposure on the infection of mice by St Lucian Schistosoma mansoni cercariae were investigated in a running-water habitat.For all exposure times, mice exposed to cercarial concentrations from 2·5 to 40 cercariae per mouse acquired no infections. At higher concentrations, infection rates and worm burdens of mice increased in direct proportion to cercarial concentrations and exposure times. The highest infection rate (57·9 %) and worm burden (46 worms) were obtained in mice exposed for 256 mm to 1280 cercariae per mouse.Cercarial concentrations are low in St Lucian running waters, a fact suggesting that the risk of persons becoming infected while fording, collecting domestic water, washing clothes and swimming in habitats with reasonable flows is very low. It appears that most infected individuals acquire a low worm burden over a rather long period of time.

Studies on the effects of cercarial concentration and length of exposure on the infection of mice by Schistosoma mansoni

Parasitology ◽  
1973 ◽  
Vol 67 (2) ◽  
pp. 219-228 ◽  
Author(s):  
E. S. Upatham ◽  
R. F. Sturrock
Keyword(s):  
Schistosoma Mansoni ◽  
Prolonged Exposure ◽  
Short Exposure ◽  
Infection Rates ◽  
Domestic Water ◽  
Low Concentrations ◽  
Prolonged Contact ◽  
Main Factors ◽  
Low Exposure ◽  
High Concentrations

Groups of mice were exposed to Schistosoma mansoni cercariae in a large volume of water. A factorial design was used to investigate the effects of cercarial concentration and length of exposure on infection rates and worm burdens. Low exposure times and cercarial concentrations gave no infections, but prolonged exposure to high concentrations gave high infection rates and worm burdens. Prolonged exposure to low concentrations gave low worm burdens and moderate infection rates: short exposure to high concentrations gave moderate infection rates and worm burdens. Statistical analysis showed that both infection rates and mean worm burdens were significantly related to the two main factors, but the relationship was complicated in each case by curvilinear effects and by a significant interaction between the main factors. Field cercarial concentrations are generally low on St Lucia, a fact suggesting that brief human water contacts, such as fording and filling domestic water containers, play little part in transmission. Prolonged contact during swimming, bathing and washing clothes may produce significant infection rates accompanied by low worm burdens. However, on the rare occasions when high cercarial concentrations occur, even the briefest exposure may produce significant infection rates and moderate worm burdens.

scholarly journals Susceptibility of Biomphalaria tenagophila and Biomphalaria glabrata from the same region to two Brazilian strains of Schistosoma mansoni

1994 ◽  
Vol 36 (5) ◽  
pp. 409-415 ◽  
Author(s):  
Roney Elias da Silva ◽  
Alan Lane de Melo ◽  
Leógenes Horácio Pereira
Keyword(s):  
Schistosoma Mansoni ◽  
Infection Rate ◽  
Biomphalaria Glabrata ◽  
Infection Rates ◽  
Experimental Conditions ◽  
Belo Horizonte ◽  
Cabo Frio

B. tenagophila snails from Ouro Branco, MG, showed positivity for S. mansoni, with infection rates of 5%, 10%, (SJ strain), and 1% (LE strain) using a pool of miracidia. The mollusks were found to be susceptive from the 3rd generation reared in laboratory onwards. The B. tenagophila (OB, MG) when individually exposed to 10 miracidia, showed infection rate of 2% for LE strain. B. glabrata snails from Gagé, MG, showed a positivity rate of 58% for S. mansoni (LE strain), under experimental conditions. The B. tenagophila from Cabo Frio, RJ and B. glabrata from Belo Horizonte, MG used as a control for SJ strain showed infection rates of 47% - 85% and 36% respectivily. For the LE strain, B. glabrata (BH, MG) used as control showed infection rate of 40% - 75%.

scholarly journals Toxoplasma gondii in Sheep and Goats from Central Iran

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Mojtaba Bahreh ◽  
Bahador Hajimohammadi ◽  
Gilda Eslami
Keyword(s):  
Toxoplasma Gondii ◽  
Dna Extraction ◽  
Infection Rate ◽  
Nested Pcr ◽  
Prevention Programs ◽  
Central Iran ◽  
Infection Rates ◽  
Sheep And Goats ◽  
One Year ◽  
Undercooked Meat

Abstract Objective Toxoplasmosis, caused by Toxoplasma gondii, infects humans by consuming infected raw or undercooked meat and foods harboring mature oocysts. In this study, we assessed the prevalence of T. gondii in sheep and goats coming from central Iran. After completing the questionnaire, about one gram of liver or diaphragm tissue was taken as a sample from 90 sheep and 90 goats slaughtered in Yazd Province and stored at – 20 ºC. DNA extraction was done, and then T. gondii was detected using nested PCR. Results This study indicated that the prevalence of T. gondii in all slaughtered animals was 11.6% (21 of 180), including 14.4% (13/90) in sheep and 8.8% (8/90) in goats. The infection rates in liver and diaphragm samples were 12.2% (11/90) and 11.1% (10/90), respectively (p = 0.8163). The infection rate in animals older than one was 16.3% (15/92), and it was 6.8% (6/88) in animals under one year of age. Therefore, no significant differences were found (p = 0.475). Infection rates were 19.5% (18/92) in males and 3.4% (3/88) in females (p = 0.0007). In conclusion, the infection rates of toxoplasmosis in livestock in this area are almost high, and therefore, it is necessary to design appropriate prevention programs to control the disease.

scholarly journals The Effect of Vaccination Rates on the Infection of COVID-19 under the Vaccination Rate below the Herd Immunity Threshold

2021 ◽  
Vol 18 (14) ◽  
pp. 7491
Author(s):  
Yi-Tui Chen
Keyword(s):  
Infection Rate ◽  
Herd Immunity ◽  
The United States ◽  
Vaccination Rate ◽  
Infection Rates ◽  
Vaccination Rates ◽  
The United Kingdom ◽  
The World ◽  
Almost All ◽  
The Impact

Although vaccination is carried out worldwide, the vaccination rate varies greatly. As of 24 May 2021, in some countries, the proportion of the population fully vaccinated against COVID-19 has exceeded 50%, but in many countries, this proportion is still very low, less than 1%. This article aims to explore the impact of vaccination on the spread of the COVID-19 pandemic. As the herd immunity of almost all countries in the world has not been reached, several countries were selected as sample cases by employing the following criteria: more than 60 vaccine doses per 100 people and a population of more than one million people. In the end, a total of eight countries/regions were selected, including Israel, the UAE, Chile, the United Kingdom, the United States, Hungary, and Qatar. The results find that vaccination has a major impact on reducing infection rates in all countries. However, the infection rate after vaccination showed two trends. One is an inverted U-shaped trend, and the other is an L-shaped trend. For those countries with an inverted U-shaped trend, the infection rate begins to decline when the vaccination rate reaches 1.46–50.91 doses per 100 people.

Biological control of Fusarium wilt of cucumber with nonpathogenic isolates of Fusarium oxysporum

1987 ◽  
Vol 33 (5) ◽  
pp. 349-353 ◽  
Author(s):  
T. C. Paulitz ◽  
C. S. Park ◽  
R. Baker
Keyword(s):  
Biological Control ◽  
Fusarium Oxysporum ◽  
Infection Rate ◽  
Fusarium Wilt ◽  
Disease Incidence ◽  
Infection Rates ◽  
Control Activity ◽  
Significant Difference ◽  
Cucumber Roots ◽  
Linear Regressions

Nonpathogenic isolates of Fusarium oxysporum were obtained from surface-disinfested, symptomless cucumber roots grown in two raw (nonautoclaved) soils. These isolates were screened for pathogenicity and biological control activity against Fusarium wilt of cucumber in raw soil infested with Fusarium oxysporum f. sp. cucumerinum (F.o.c.). The influence of three isolates effective in inducing suppressiveness and three ineffective isolates on disease incidence over time was tested. The effective isolates reduced the infection rate (R), based on linear regressions of data transformed to loge (1/1 – y). Effective isolate C5 was added to raw soil infested with various inoculum densities of F.o.c. In treatments without C5, the increase in inoculum densities of F.o.c. decreased the incubation period of wilt disease, but there was no significant difference in infection rate among the inoculum density treatments. Isolate C5 reduced the infection rate at all inoculum densities of F.o.c. Various inoculum densities of C5 were added to raw soils infested with 1000 cfu/g of F.o.c. In the first trial, infection rates were reduced only in the treatment with 10 000 cfu/g of C5; in the second trial, infection rates were reduced in treatments with 10 000 and 30 000 cfu/g of C5.

Immunization efficacy of ozone-exposed cercariae against subsequent Schistosoma mansoni challenge infection

2011 ◽  
Vol 61 (3) ◽  
pp. 289-301
Author(s):  
Azza H. Mohamed
Keyword(s):  
Schistosoma Mansoni ◽  
Worm Burden ◽  
Structural Changes ◽  
Relative Weight ◽  
Challenge Infection ◽  
Total Leukocyte Count ◽  
Post Challenge ◽  
Igg Antibody ◽  
Sem Images ◽  
Infected Control

AbstractCD1 mice were immunized subcutaneously with 20 ozone-exposed (70μg/ml, 1 minute exposure) Schistosoma mansoni cercariae weekly/three weeks. The efficacy of immunization was assessed 10 weeks post challenge infection by the determination of the worm burden, ova count, oogram, granuloma diameter, IgG reactions against soluble egg antigen (SEA) and tegument structural changes of recovered worms that are immunized. A reduced worm length and a reduction in worm burden were observed in the immunized group as compared to the infected not immunized group. Moreover, no ova were found in liver and intestine from the immunized mice as compared with infected control mice. Also, immunization with ozonated cercariae showed a decrement in the mean relative weight of liver and spleen. Total leukocyte count was increased in the immunized animal as compared to the infected control. The level of total IgG antibody against SEA decreased in immunized mice as compared with the infected control mice. Scanning electron microscope (SEM) images of worms recovered 10 weeks post challenge from the immunized group revealed extensive tegumental destruction. This study underlines the significant role of ozone attenuated cercariae vaccine against S. mansoni infection, which generated specific immunity with a significant level of protection.

Age grades and infection rates of Rhipicephalus appendiculatus Neumann (Acari: Ixodidae) to assess theileriosis challenge in the field

1985 ◽  
Vol 75 (4) ◽  
pp. 653-660 ◽  
Author(s):  
Alan R. Walker ◽  
June D. Fletcher
Keyword(s):  
Salivary Glands ◽  
Infection Rate ◽  
Rhipicephalus Appendiculatus ◽  
Physiological Age ◽  
Methyl Green ◽  
Infection Rates ◽  
A Value ◽  
Type 3

AbstractData are presented from five series of 240 adults of Rhipicephalus appendiculatus Neumann kept in the laboratory, in which a steady decline in the numbers of granules in e cells of type 3 acini of the salivary glands occurred. This was readily detected in whole gland preparations of the salivary glands stained with methyl green and pyronin, and the same specimens could be used for detecting Theileria parasites in the salivary glands. Characteristics for grading these ticks into three physiological age grades are given, and a formula is provided for incorporating the age grade with infection rate. This gives a value for comparative estimates of the challenge posed by field populations of ticks for the transmission of Theileria to cattle.

Mitochondria as a potential target for the development of prophylactic and therapeutic drugs against Schistosoma mansoni infection

2021 ◽  
Author(s):  
Keith Kiplangat Talaam ◽  
Daniel Ken Inaoka ◽  
Takeshi Hatta ◽  
Daigo Tsubokawa ◽  
Naotoshi Tsuji ◽  
...  
Keyword(s):  
Drug Development ◽  
Schistosoma Mansoni ◽  
Worm Burden ◽  
Consumption Rate ◽  
Therapeutic Agent ◽  
Ex Vivo ◽  
Prophylactic Agent ◽  
Therapeutic Drugs ◽  
Pyrvinium Pamoate

Emergence of parasites resistant to praziquantel, the only therapeutic agent, and its ineffectiveness as a prophylactic agent (inactive against the migratory/juvenile Schistosoma mansoni ), makes the development of new antischistosomal drugs urgent. The parasite’s mitochondrion is an attractive target for drug development because this organelle is essential for survival throughout the parasite’s life cycle. We investigated the effects of 116 compounds against Schistosoma mansoni cercariae motility that have been reported to affect mitochondria-related processes in other organisms. Next, eight compounds plus two controls (mefloquine and praziquantel) were selected and assayed against motility of schistosomula ( in vitro ) and adults ( ex vivo ). Prophylactic and therapeutic assays were performed using infected mouse models. Inhibition of oxygen consumption rate (OCR) was assayed using Seahorse XFe24 Analyzer. All selected compounds showed excellent prophylactic activity, reducing the worm burden in the lungs to less than 15% that obtained in the vehicle control. Notably, ascofuranone showed the highest activity with a 98% reduction of the worm burden, suggesting the potential for development of ascofuranone as a prophylactic agent. The worm burden of infected mice with S. mansoni at the adult stage was reduced by more than 50% in mice treated with mefloquine, nitazoxanide, amiodarone, ascofuranone, pyrvinium pamoate, or plumbagin. Moreover, adult mitochondrial OCR was severely inhibited by ascofuranone, atovaquone, and nitazoxanide, while pyrvinium pamoate inhibited both mitochondrial and non-mitochondrial OCRs. These results demonstrate that the mitochondria of S. mansoni are feasible target for drug development.

scholarly journals Synergistic action of praziquantel and host specific immune response against Schistosoma mansoni at different phases of infection

2004 ◽  
Vol 46 (4) ◽  
pp. 231-233 ◽  
Author(s):  
Fabio Ribeiro ◽  
Rômulo Teixeira de Mello ◽  
Carlos Alberto Pereira Tavares ◽  
John Robert Kusel ◽  
Paulo Marcos Zech Coelho
Keyword(s):  
Immune Response ◽  
Schistosoma Mansoni ◽  
Worm Burden ◽  
Synergistic Action ◽  
Specific Immune Response ◽  
Concomitant Immunity

The interaction between specific immune response to Schistosoma mansoni and praziquantel (PZQ) was studied in mice. In mice harboring concomitant immunity, 6-day-old parasites treated with PZQ were more effectively removed than 24h treated parasites despite both had a significant worm burden reduction when compared with respective treated controls. These results show that PZQ can be effective at the skin and lung stages of parasite's development mainly acting with a established specific immune response, and particularly at the lung phase.

scholarly journals Results of 10 years sampling of Chironomidae from German lowland running waters differing in degradation

2018 ◽  
Author(s):  
Claus Orendt
Keyword(s):  
Water Body ◽  
Statistical Significance ◽  
Detrended Correspondence Analysis ◽  
Careful Examination ◽  
Running Waters ◽  
Assessment Practice ◽  
Body Type ◽  
Running Water ◽  
North East ◽  
Species Preferences

Based on data from monitoring in north-east Germany (Land Brandenburg) over a decade, chironomid taxa and their abundances were analysed for their preferences for certain running water types and degradation levels. A detrended correspondence analysis (DCA) revealed that the distribution of the taxa was determined by both, degradation level and water body type. A series of taxa was positively or negatively correlated to degradation, however, frequently only in certain water body types. In other types, they played no major role or were evenly distributed along the degradation gradient. Higher correlations were found for taxa favouring ‘good’ and 'poor' or 'bad' conditions than for preferers of ‘moderate’ status. The results allow to validate indices and weigths of indicators derived from high frequencies of the taxa in certain one or more quality class(es). The preferred ocurrencies elaborated have to be discussed or tested for plausiblity before using or evaluating powerful indicator taxa for classifications or revisions in assessment practice. A reduction of the taxonomical precision to genus level lowered the statistical significance and requires careful examination of the species preferences of the genus.

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