ABSTRACT
Dengue fever is one of the most serious mosquito-borne infectious diseases in the tropical world, causing substantial human morbidity and mortality, yet there is no specific treatment till now, and the main measures preventing dengue fever include applying pesticide to kill adult vector mosquitos and removing standing water to prevent the breeding of mosquitoes etc. Appropriate uses of such approaches can reduce dengue epidemic risk via reducing mosquito density. In fact, vector control using insecticides is the most common method to prevent and control mosquito-borne disease transmission. Nevertheless, recent research has shown that Aedes albopictus and Aedes aegypti, the two key vectors for dengue fever transmission, have rapidly developed high resistance to the most commonly used adult insecticide pyrethroid (deltamethrin and permethrin) and larvicide organophosphate (temephos). Therefore, it is of great significance to obtain a new drug with longer-term efficacy to prevent dengue virus transmission. Pesticides currently used act on adult stage of mosquitoes, typically applying to the environment where mosquito bites (on humans) occur, and very few target on egg or juvenile stages of the mosquitoes in the water environment. Calcium cyanamide (CaCN2), widely used as a fertilizer in many different settings, was recently shown to have potential to prevent tropical diseases by eliminating or inhibiting the growth and development of intermediate hosts. The main compounds of calcium cyanamide (CaCN2) are CaCN2 (50%- 60%) and calcium oxide (15%). The representative products of calcium cyanamide (CaCN2) are PERLKA® from Germany and ROEBON® from China. CaCN2 has recently been recognized to have the fungicidal effect on the pathogens of the soil borne diseases and addition of CaCN2 could benefit the thermophilic phase and the composting could quickly reach the sanitary standard and will contribute to solve the feces disposal problems. According to our team's long-term investigation and research, we found that ROEBON® (50% CaCN2) can be used to eliminate Oncomelania and effectively control the spread of schistosomiasis. In the latest research, we have confirmed that 10 mg/L CaCN2 (20 mg/L ROEBON®) can completely inhibit the emergence of mosquito larvae and the population growth from the perspective of inhibiting development and the efficacy can lasts for three months. Calcium cyanamide is a good candidate drug to control mosquito-borne infectious diseases transmission, especiallly for dengue fever prevention. In 2014, Scientific Committee on Health and Environmental Risks in European Commission promoted preliminary opinion on potential risks to human health and the environment from the utilization of calcium cyanamide as fertilizer, but convincing evidences for the causal connections between the exposure to CaCN2 and human health damages are missed. Given a 96-h acute zebrafish toxicity study, the No Observed Effect Concentration (NOEC) of calcium cyanamide to zebrafish was 100 mg/L CaCN2. In summary, most of the data are based on the evaluation of the effect of CaCN2 as a fertilizer, and the related research as a mosquito inhibitor is still very scarce. The research on toxicity of CaCN2 in mosquitoes needs to be further strengthened.
ABSTRACT
Objective To study the morphological change of Schistosoma japonicum eggs processed by calcium cyanamide synthetic drug,so as to provide the basis for further study of the mechanism that calcium cyanamide synthetic drug to schisto?some eggs. Methods The calcium cyanamide synthetic drug was added to the cattle feces containing schistosome eggs and mixed up,and then the cattle feces was stacked as original shape on the marshland. Blank controls were set at the same time. The cattle feces samples were collected and the schistosome eggs were observed under a microscope on the 1st,2nd,3rd,7th day after the experiment. Results By the effect of calcium cyanamide synthetic drug,the color of eggs was deepening gradual?ly,the miracidia were atrophied,and the shells of eggs were thickened. The embryonic membrane of miracidia was no longer completed 3 days later,and the miracidia were deformed severely 7 days later. The atrophy of miracidia was not obvious in the blank controls. Conclusion The schistosome miracidia and embryonic membrane can be damaged by the calcium cyanamide synthetic drug,and worse damaged with time extending.
ABSTRACT
Objective To observe the effects of calcium cyanamide (Rongbao) on the histological and morphological changes of Oncomelania hupensis snails in order to explore its molluscicidal mechanisms.Methods The serial snails' slides were fixed after soaking in a concentration of Rongbao leached liquor at different time.The histological and morphological changes of the snails were compared among these slides.Results After soaking in the Rongbao leached liquor for 48 h,the mantle epithelia,respiratory epithelia of the gill,liver cells,and muscle cells of gastropods were injured seriously,which resulted in the death of the snails directly.The death rates of the snails were 96.70% and 100% after soaking in the Rongbao leached liquor for 48 h and 72 h,respectively.Conclusion Rongbao is an effective molluscicide by damaging the several snail tissues.