Induced regression of dieldrin-resistance in the housefly (Musca domestica L.)

A high degree of resistance to cyclodiene insecticides, which appeared in a previously susceptible housefly strain maintained without exposure to insecticides but propagated from early-emerging adults to increase susceptibility to DDT, was found to be due to a single autosomal factor. Subsequent selection of a substrain for late adult emergence over 50 generations was unsuccessful in materially reversing the dieldrin-resistance or in demonstrating that selection of early-emerging flies was responsible for its appearance. However, selection and propagation of the knockdown-susceptible fraction of the population with lindane over 30 generations eliminated cyclodiene-resistance entirely. This method can be of value in maintaining laboratory strains at a normal level of susceptibility to cyclodiene insecticides. It is apparent, nevertheless, that various manipulations of a standard strain may affect its toxicological as well as other characteristics. The authors stress that when a standard reference strain is required for an extended period of time, it should be rigorously controlled and continuously evaluated.     

Studies on the population dynamics of the housefly, Musca domestica L

The population level and potential rate of increase of a population of houseflies, Musca domestica L., on Grand Turk Island was studied for about 2 years to determine what changes occurred when no control was applied (the first year) and when the population was totally suppressed by the application of chemosterilant baits (the second year). During the first year the population was relatively stable (the highest density occurred in June and the lowest in January) and the difference between the high and low levels was only 3-fold. When chemosterilant baits were applied over a 40-week period and total suppression was achieved, calculations based on the sterility achieved and the resulting control revealed that the population showed potential rates of increase ranging up to 4-fold during the period from June through October and from 4-fold to 11-fold from December through April. Thus, in the field, the potential rates of increase of the housefly are low despite its high biotic potential.     

Resistance of the housefly (Musca domestica L.) to insecticides in Egypt

Housefly resistance to DDT and lindane in Egypt was first reported 17 years ago, yet these insecticides continue to be used.     

Detection of anthrax vaccine virulence factors by polymerase chain reaction.

In Italy, an attenuated Bacillus anthracis strain, named 'Carbosap', is used for immunization against ovine and bovine anthrax. Analysis on 'Carbosap', Sterne vaccine strain F34 and Pasteur vaccine strain SS104, were performed using primers specific for the sequences, encoding the toxic factors, located on plasmids pXO1 and pXO2 and primers specific for the chromosome. The results obtained from polymerase chain reaction (PCR) assay revealed the presence of both plasmids pXO1 and pXO2 in 'Carbosap' strain. This study showed that the 'Carbosap' vaccine strain has a different plasmid pattern in comparison to Pasteur vaccine strain SS104 and Sterne vaccine strain F34.     

Studies on the inheritance of carbamate-resistance in the housefly (Musca domestica L.)

In view of the increasing importance of carbamic acid esters in insect control, the authors have conducted studies on the inheritance of carbamate-resistance in the housefly Resistance to Isolan (1-isopropyl-3-methyl-5-pyrazolyl dimethylcarbamate) in carbamate-selected strains is inherited as a partially dominant major single factor, without sex linkage or appreciable cytoplasmic influence. Inclusion of piperonyl butoxide as a synergist with Sevin (1-naphthyl methylcarbamate), Zectran (4-dimethylamino-3,5-xylyl methylcarbamate), or m-isopropylphenyl methylcarbamate also produced evidence of monofactorial inheritance.     

鼠疫耶尔森菌的多重PCR检测方法

目的研究一种快速、特异的检测鼠疫耶尔森菌(鼠疫菌)的多重聚合酶链反应(PCR)方法。方法选用针对鼠疫菌F1抗原基因、pla基因、inv基因和一段鼠疫特异染色体序列设计的4对引物,以鼠疫菌及其他肠道致病菌DNA为模板并加入内部对照模板,在同一扩增体系中进行PCR扩增。结果鼠疫菌DNA模板可扩增出预期产物,而其他菌株只能扩增出内部对照模板的片段。结论多重PCR方法具有较高的特异性。可迅速、有效地将鼠疫菌与其他肠道致病菌相鉴别,也可应用于鼠疫监测。     

A study of the genetics of dieldrin-resistance in the housefly (Musca domestica L.)

Reciprocal mass crosses and back-crosses were performed between two homogeneous strains of the housefly (Musca domestica L.), representing the extremes in susceptibility and resistance to dieldrin. The heterozygotes were found to be intermediate between susceptible and resistant parents, and showed no evidence of sex linkage or cytoplasmic effects. The F₂ generation segregated in an approximate ratio of 1:2:1 into susceptible, heterozygote and resistant phenotypes, while the back-cross to the susceptible parent yielded 49.8:50.2 susceptible: resistant males, and 48.8:51.2 susceptible: resistant females. Elimination of susceptible forms in the back-cross progeny by use of a discriminating dosage and interbreeding the survivors produced offspring segregating into 26% susceptible, 50.1% heterozygote and 23.9% resistant, in excellent statistical agreement with a ratio of 1:2:1 expected in simple Mendelian inheritance. It is concluded that resistance to dieldrin in the housefly strain studied is due primarily to a major single pair of alleles or to a number of closely linked alleles so that they are inherited as a single unit.     

家蝇对氯氰菊酯抗性的风险评估与预报

目的 评估家蝇(Musca domestica)对氯氰菊酯抗性风险，预测抗性发展速率。方法 采集自然种群家蝇带回室内饲养，采用点滴法用氯氰菊酯筛选抗性品系，测定LD50；采用Tabashnik的方法测定抗性遗传力和预测抗性发展速率。结果 家蝇在室内饲养并用氯氰菊酯连续筛选了10代，平均存活率54．5％，抗性上升了50倍。测得抗性遗传力h^2为0．1577。据此预测在50％～90％的杀死率的选择压力下，要获得10倍的抗性仅需2．2～4．8代。结论 家蝇对氰氰菊酯抗性上升迅速，10代内抗性遗传力基本稳定。     

多重聚合酶链反应检测流感嗜血杆菌

目的 建立检测流感嗜血杆菌的多重聚合酶链反应(M-PCR)方法 .方法 合成扩增流感嗜血杆菌编码P6外膜蛋白基因的引物(Hi),鉴定流感嗜血杆菌种特异性;合成扩增流感嗜血杆菌编码荚膜基因的引物(Hi-cap),鉴定菌株是否具有荚膜;设计并合成6对扩增流感嗜血杆菌不同血清型(荚膜型)编码摹因的引物(Hia-Hif),鉴定菌株的血清型,以其他呼吸道常见病原体菌株做对照,应用M-PCR方法 对200株临床分离的疑似流感嗜血杆菌菌株进行鉴定和血清分型.结果 M-PCR方法 检测流感嗜血杆菌具有高度的敏感性和特异性.对照菌株应用种(Hi)、荚膜(Hi-cap)和荚膜型(Hia-Hif)特异引物没有扩增出DNA片段.M-PCR方法 检测DNA的最低检测量为0.935 Pg.对临床分离的200株疑似流感嗜血杆菌鉴定,189株为流感嗜血杆菌,与API R NH鉴定结果 一致.其中1株具有荚膜,为f血清型,与玻片凝集法鉴定结果 一致.结论 M-PCR方法 检测流感嗜血杆菌具有较高的敏感性和特异性,可用于流感嗜血杆菌感染病例标本的快速检测和病例诊断.     

Detection of Leishmania braziliensis in naturally infected individual sandflies by the polymerase chain reaction.

The natural infection of sandflies by Leishmania in wild-caught specimens was studied, using the polymerase chain reaction (PCR)-hybridization technique. The PCR was carried out using 2 oligonucleotides (primers 3J1 and 3J2) derived from a repetitive nuclear DNA sequence. The primers support the enzymatic amplification of a fragment of approximately 500 bp, present in the nuclear DNA of Leishmania braziliensis. The expected band was observed in 5 of 65 sandflies containing flagellates. After hybridization with a species-specific probe, we confirmed natural infection by L. braziliensis. The technique allowed the identification of Lutzomyia gomezi and Lu. panamensis as vectors of L. braziliensis in an endemic area of cutaneous leishmaniasis in Urama, Puerto Cabello district in Venezuela. As far as we are aware, this work constitutes the first report of natural infection of Lu. panamensis with L. braziliensis in the study area. We also demonstrate that PCR-hybridization is a suitable approach to establish the Leishmania-sandfly relationship and will be useful in epidemiological studies of leishmaniasis in endemic areas.     

Detection of St. Louis encephalitis virus in mosquitoes by use of the polymerase chain reaction.

We recently developed an assay using the polymerase chain reaction (PCR) for the specific detection of St. Louis encephalitis (SLE) virus RNA. This assay was tested in a blind study on 7 samples of pooled mosquitoes (50 mosquitoes/pool) which were also characterized for SLE virus by plaque assay in Vero cell culture. One sample was positive for the SLE virus as determined by both the PCR assay and a combination of the plaque assay and the indirect fluorescent antibody assay. The remaining 6 samples were negative for the presence of SLE virus as determined by both methods. These data indicate that this PCR assay can be used to monitor for the presence of SLE virus in pools of homogenized mosquitoes. This approach could provide early data on which to base disease control decisions.     

The housefly (Musca domestica) as a carrier of pathogenic microorganisms in a hospital environment.

Houseflies have long been regarded as potential carriers of microorganisms. Since pathogenic microorganisms are widespread in the hospital environment, there is abundant opportunity for flies to become contaminated and, in turn, to contaminate the patient environment. In the present study, an attempt was made to isolate and identify pathogenic bacteria, fungi and parasites from the housefly Musca domestica collected in the surgical ward of the All India Institute of Medical Sciences Hospital and also in a remote residential area located 5 km from the hospital. A total of 113 flies were collected: 65 from a surgical ward (test) and 48 from a residential area for comparison. Ten genera of bacteria were isolated from the test group of flies compared with nine from the control group. In primary isolations, it was observed that the load of bacteria carried by the test group of flies was significantly more (P less than 0.001) than for the control flies. Pseudomonas aeruginosa, Enterococcus faecalis and viridans streptococci were isolated only from the test flies. The isolation rate of Staphylococcus aureus was significantly higher (P less than 0.001) in test houseflies than in the control houseflies. There was no significant difference in isolation of parasitic ova and cysts from test and control houseflies. Candida spp. were isolated in almost equal numbers from both groups of houseflies, yet none of these was Candida albicans. Houseflies therefore may act as vectors of potentially pathogenic bacteria in a hospital environment.