Physico-chemical properties of substances used as molluscicides: precipitation and adsorption

When molluscicide solutions are applied to natural waters, the active substance may be precipitated or adsorbed and its concentration in the water thus rapidly reduced below the effective minimum. In this paper the authors describe experiments in which factors affecting loss by precipitation and adsorption were examined separately for a number of molluscicidal chemicals. It was found that the amount lost by precipitation depended on the pH of the water and that at a given pH there was a maximum amount of chemical that would remain in solution. The amount lost by adsorption on a standard adsorbent (filter-paper) appeared to be negligible with certain compounds, but with others it was found to depend both on the salt content and on the pH of the water, decreasing with increased dissolved solids and increased pH. It is therefore essential to take into consideration the pH and turbidity of the water before applying molluscicidal treatment.     

Some laboratory investigations on Bayer 73 and ICI 24223 as molluscicides

The authors report on laboratory tests of the chemical properties and molluscicidal activity of the compounds Bayer 73 (70% wettable powder) and ICI 24223 (acid salt and emulsion), and describe the method used for the determination of ICI 24223.     

Filamentous phage as an immunogenic carrier to elicit focused antibody responses against a synthetic peptide

Filamentous bacteriophage are widely used as immunogenic carriers for "phage-displayed" recombinant peptides. Here we report that they are an effective immunogenic carrier for synthetic peptides. The f1.K phage was engineered to have an additional Lys residue near the N-terminus of the major coat protein, pVIII, so as to enhance access to chemical cross-linking agents. The dimeric synthetic peptide, B2.1, was conjugated to f1.K (f1.K/B2.1) in high copy number and compared as an immunogen to B2.1 conjugated to ovalbumin (OVA/B2.1) and to phage-displayed, recombinant B2.1 peptide. All immunogens were administered without adjuvant. The serum antibody titers were measured against: the peptide, the carrier, and, if appropriate, the cross-linker. All immunogens elicited anti-peptide antibody titers, with those elicited by OVA/B2.1 exceeding those by f1.K/B2.1; both titers were greater than that elicited by recombinant B2.1 phage. Comparison of the anti-peptide and anti-carrier antibody responses showed that f1.K/B2.1 elicited a more focused anti-peptide antibody response than OVA/B2.1. The anti-peptide antibody response against f1.K/B2.1 was optimized for the injection route, dose and adjuvant. Dose and adjuvant did not have a significant effect on anti-peptide antibody titers, but a change in injection route from intraperitoneal (IP) to subcutaneous (SC) enhanced anti-peptide antibody titers after seven immunizations. The optimized anti-peptide antibody response exceeded the anti-carrier one by 21-fold, compared to 0.07-fold elicited by OVA/B2.1. This indicates that phage as a carrier can focus the antibody response against the peptide. The results are discussed with respect to the advantages of phage as an alternative to traditional carrier proteins for synthetic peptides, carbohydrates and haptens, and to further improvements in phage as immunogenic carriers.     

Natural and synthetic plant compounds as anti-biofilm agents against Escherichia coli O157:H7 biofilm

Escherichia coli is a common gram-negative bacterium found in the gut and intestinal tract of warm-blooded animals including humans. An evolved seropathotype E. coli O157:H7 (STEC) came into existence in 1982, since then it has been evolved as a stronger and more robust drug-resistant pathotype of E. coli. This drug resistance is due to horizontal gene transfer, natural gene evolution for survival, and most of the cases due to the ability of STEC to switch to the biofilm growth mode from planktonic lifestyle. During the growth in biofilm mode, Escherichia coli O157:H7 opts more robust ability to grow in adverse environments i.e., in presence of antibiotics and other antimicrobial chemicals. Due to the biofilm matrix, the microbial community acquires drug resistance. This makes the treatment of diseases caused by E. coli O157:H7 a complex challenge. To address the illnesses caused by this biofilm-forming pathogen, there are several possible strategies such as antibiotic therapies, synthetic antimicrobial chemicals, adjunct therapy of synergistic effect of multiple drugs, and more importantly plant originated compounds as a new anti-biofilm candidate. The present review summarizes various phytochemicals and their derivatives reported in the last decade mostly to eliminate the biofilm of STEC. The review will progressively reveal the antibiofilm mechanism of the phytochemicals against STEC and to be a potential candidate for the development of the future antibacterial drugs to STEC induced infections.     

Movement control as an effective measure against Covid-19 spread in Malaysia: an overview

Journal of Public Health - The first Covid-19 cases were reported in Malaysia on 25 January 2019 followed by a quiescent period before an upward swing of the cases at the end of February 2020,...     

Assessment of the potential of competitor snails and African catfish (Clarias gariepinus) as biocontrol agents against snail hosts transmitting schistosomiasis

The objective of this study was to assess the potential of the snails Physa acuta and Melanoides tuberculata and the African catfish Clarias gariepinus as biological control agents against the Schistosoma mansoni intermediate host Biomphalaria pfeifferi under laboratory conditions. Groups of five target and five competitor snails were raised together in experimental aquaria and same number in separate aquaria as controls. Shell size, number of eggs and mortality rate were recorded for twelve consecutive weeks. The stocking density for C. gariepinus was one fish per aquarium. Fish were provided with adequate or inadequate supplementary food and fifteen B. pfeifferi were added to each aquarium. The snails and their eggs were counted daily. Significant differences in shell growth and fecundity were noted between B. pfeifferi and M. tuberculata. Physa acuta was noted to be voracious in food consumption. Snail consumption was faster by fish provided with inadequate supplementary food. Based on the present findings, it is suggested that the two competitor snails and African catfish could be used as biological control agents against B. pfeifferi. Nevertheless, the susceptibility of the competitor snails to other trematodes in Ethiopia must first be ruled out before introducing these snails into new habitats. Follow-up field observation and rigorous laboratory studies remain areas for further research.     

The path towards effective antivirals against rabies

Rabies virus remains an important burden of disease claiming an estimated 60,000 lives each year, mainly children, and having a huge economical and societal cost. Post-exposure prophylaxis (PEP) is highly effective, however in patients that present with neurological symptoms the case-fatality ratio is extremely high (>99%). During the last decades several attempts to identify potent and effective antivirals were made. Only a few of these demonstrated improvement in clinical signs in animal studies and none of the trials in humans showed significant efficacy. Here we explore novel opportunities to identify more potent anti-rabies molecules. In particular important progress has been made on antivirals against other Mononegavirales (paramyxoviruses, filoviruses) which should be an impetus to test and optimize these molecules towards anti-rabies virus therapies. Effective rabies antivirals for therapeutic use need to be molecules that can be dosed into the cerebrospinal fluid and that rapidly and potently block ongoing virus replication and as such stop the further spread of the virus. Antivirals for prophylactic use can also be envisaged and these should be able to prevent infection of peripheral nerve cells and should have the potential to replace the current anti-rabies immunoglobulins that are used in PEP.     

Physico-chemical properties of substances used as molluscicides: Hydrolysis of N-tritylmorpholine (Shell WL 8008)*

Under field conditions molluscicides can undergo hydrolysis to compounds that have no molluscicidal action. In a continuation of laboratory studies on hydrolysis, investigations have been made on N-tritylmorpholine (Shell WL 8008). The rate of hydrolysis increases with decreasing pH, being rapid below pH 7. An emulsion prepared from an emulsifiable concentrate was found to be much more stable than an aqueous solution of the compound, presumably because of the protective effect of oil droplets. The stability of the compound as a wheat-germ bait was also studied; there was about a 10% decrease in concentration in 22 hours. The portion that dissolved in the water was almost completely hydrolysed, whereas that remaining in the bait was much less so.     

合成无定型二氧化硅杀灭鸡皮刺螨试验研究

目的试验验证合成无定型二氧化硅对鸡皮刺螨的杀灭效果及应用的可行性。方法参照GB/T 13917.1-2009滞留喷洒剂的强迫接触法。结果 3%合成无定型二氧化硅喷射剂,按6 g a.i/m2用量,涂布于3种板面,对于鸡皮刺螨,在水泥板面24 h杀灭率100%,45 d观察期内效果未下降;硅酸盐玻璃面24 h杀灭率即为100%,醇酸清漆木板面48 h杀灭率100%。结论合成无定型二氧化硅对鸡皮刺螨具有良好的杀灭效果。     

天南星有效成分的杀螺活性分析

目的研究天南星提取物的灭螺有效成分。方法测试提取物作用后钉螺的死亡率。结果天南星正丁醇提取物的灭螺活性最强，其提取物100mg／L浓度处理2d，钉螺死亡率达76．67％，3d达100％；块茎的杀螺活性较地上部分强，如60mg／L浓度处理2d，地上部分和块茎正丁醇提取物对钉螺的致死率为13．33％和40．00％，处理4d后钉螺的死亡率分别为50．00％和100％。结论天南星块茎正丁醇提取物可能是最有效的火螺活性成分。     

Latex and synthetic polymers gloves: protective effectiveness against biological risk

BACKGROUND: The quick evolution of knowledge about latex and, especially, its effectiveness as protection against biological risks on one hand, and, on the other hand, as trigger of cutaneous, respiratory and sistemic allergic diseases, required a marked distinction between conditions in which latex is necessary and conditions in which latex could be substituted by syntetic polymers. OBJECTIVES: The aim of this study is to verify protective effectiveness of gloves made of syntetic polymers against biological risks compared with latex gloves which until now have been considered as the best protection. METHODS: Literature review. RESULTS: The most recent studies seem to consider neoprene gloves as the safest protection to replace latex in working activities with high biological risk exposure. CONCLUSION: The literature review marked the lack of studies exclusively focused on glove permeability towards biological agents. It seems therefore necessary to investigate this topic to validate results and to guarantee a suitable protection to workers daily exposed to biological risk.