Rodents in the laboratory are often detected as aphid infections ( 1 ) . The use of experimental animals infected with aphids for scientific experiments not only interferes with the correctness of the conclusions of scientific experiments, but also reduces the scientificity, accuracy and stability of scientific research, and may also threaten the health of researchers.
The development of locusts has a direct life cycle, and it usually takes 7 to 15 days to complete the egg-to-adult changes. Adults are mainly found in the cecum. By ingesting the eggs stored by the female around the host anus, it can be found that the spread of the aphid infection is horizontal, that is, mainly through the mucosa. After about 6 hours of release and hatching in the small intestine, the eggs of the mites began to become infectious. The larvae feed on bacteria in the lumen and mature in the cecum after 7 to 11 days. A female will release about 450 to 550 eggs ( 2 ) . These eggs have a strong vitality and are easy to spread, forming a wide range of pollution. They can survive for a long time at room temperature and are difficult to eliminate using ordinary disinfectants ( 3 ) .
This paper attempts to investigate whether hydrogen peroxide vapor fumigation can successfully kill the mites that contaminate animal cages.
Animal and experimental design
The experiments were divided into 3 groups, each of which was repeated three times. There were 5 male, 4 week old SCID mice each time. All experimental animals were clean animals with no endoparasites. They were exposed to a rat litter cage contaminated with mites, placed in a ventilated rack, and kept under sterile conditions. These dirty cages were processed in three ways before placing the experimental animals in these dirty cages:
1. Test group: fumigation with hydrogen peroxide at room temperature of 30 ° C for 15 minutes;
2. Negative control group: autoclave for 20 minutes at a high temperature of 121 °C;
3. Positive control group: no treatment.
Two weeks after the experimental animals touched the dirty cage, all animals were transferred back to a clean cage. After four weeks, an anal adhesive tape test was taken; and after two weeks, all animals were killed and subjected to a direct cecal examination.
Detection of infection
1 Anal adhesive paper adhesion test method: Use a 20*30mm clean tape strip to wipe the skin around the anus of all animals, then stick it on the glass slide and use a microscope to magnify the egg 100 times.
2 Direct detection method of aphids: dissect the animal carcass, take the contents of the cecum into a petri dish containing warm physiological saline, and then use a dissecting microscope to perform a magnification of 10 to 20 times.
result
1
Treatment Group | 1 st test | 2 nd test | 3 rd test | Total |
Soiled bedding fumigated | 0/5 | 0/5 | 0/5 | 0/15 |
Soiled bedding autoclaved | 0/5 | 0/5 | 0/5 | 0/15 |
Soiled bedding untreated | 5/5 | 5/5 | 5/5 | 15/15 |
2
Treatment Group | 1 st test | 2 nd test | 3 rd test | Total |
Soiled bedding fumigated | 0/5 | 0/5 | 0/5 | 0/15 |
Soiled bedding autoclaved | 0/5 | 0/5 | 0/5 | 0/15 |
Soiled bedding untreated | 5/5 | 5/5 | 5/5 | 15/15 |
1. The litter group after vaporized hydrogen peroxide fumigation: the test mice were not infected with aphids after repeated three times;
2. The litter group after autoclaving: no repeated detection of aphids in the test rats;
3. The litter group without any treatment: The test rats were infected with aphids three times .
discuss
Research background and purpose
In the case of a murine-infected murine breeding population, two different ivermectin treatment regimens failed to eliminate rodent aphids without environmental disinfection. The literature controversially discusses the need for environmental disinfection ( 2, 5 ) . Further, research data on the survival of rodent aphid eggs in the environment and their sensitivity to common saline are very limited ( 2 ) . The purpose of this study was to understand whether hydrogen peroxide fumigation could successfully kill aphid eggs and whether it could eliminate parasitic aphids in rats by combining antibacterial therapy.
Research design
In preliminary experiments, eggs in the uterus of mature female worms were completely destroyed after 15 minutes of hydrogen peroxide fumigation. However, the perianal adhesive paper test showed that the mature eggs had no such destructive effect. The test showed that the mature eggs had no obvious microscopic lesions, probably because the mature eggs were too thick and more resistant. Therefore, the study decided to use highly sensitive SCID mice as a biological test model for in vivo infection testing. In a successful experiment, these animals should be infected if they are placed on untreated contaminated litter (positive control). All rats on the litter of hydrogen peroxide fumigation (test group) or autoclave (negative test group) should be kept clean. According to the literature, rats infected with aphids have a short incubation period of about 7 to 8 days ( 6 ) . In this study, in order to avoid the occurrence of false negative results, the experiment extended the exposure time and observation time (2 weeks + 6 weeks) to ensure that all animals were infected with a sufficient time range.
Method details
Our experiments used a small hyperbaric chamber for fumigation. Due to the relatively small size of the cabin, the sterilization process is relatively accelerated. In addition, it is easier to obtain a high concentration of hydrogen peroxide contact. Since the aphid eggs are highly resistant to common disinfectants, we have chosen a relatively high concentration of hydrogen peroxide. In the sterilization stage, a total of 75 g of a 30% strength hydrogen peroxide solution was injected. This corresponds to 27.57 g of hydrogen peroxide solution or 8.27 g of pure hydrogen peroxide per cubic meter. This hydrogen peroxide concentration is about twice as high as the previous disinfection for animal rooms ( 7 ) . These positive results make it possible to start large-scale experimental tests. It is hoped that in the future there will be more detailed studies to precisely define the dose dependence of hydrogen peroxide to inactivate aphid eggs.
in conclusion
The research in this paper clearly demonstrates that the use of hydrogen peroxide fumigation can completely make the aphid eggs susceptible to host infection. This experimental method can be recommended for animal cages that effectively eliminate mites contamination, as well as for the cleaning of heat sensitive equipment such as ventilators, blowers, clean benches, and other electronic equipment (computers, balance scales, behavioral test equipment).
references:
(1) Jacoby, R. and J. R. Lindsey (1988): ILAR J. 39: 266-271. (2) Pritchett, KR and N. A. Johnston (2002): Contemp. Top. Lab. Anim. 41: 36- 46.
(3) Suckow. MA et al. (2001): The laboratory mouse. CRC Press, 80-82.
(4) Krause, J. and H. Riedesel (2002): Lab. Anim. (submitted).
(5) Huerkamp. MJ. et al (2000): Contemp. Top. Lab. Anim. 34: 76-83.
(6) Lewis. JWand J. D'Silva (1986): J. Helminthol. 60: 39-46.
(7) KrauseJ. etal (2001): Contemp.Top.Lab.Anim.40:18-21.
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