Studies on the carriage and transmission of porcine reproductive and respiratory syndrome virus by individual houseflies (Musca domestica)

The objectives of the study were to determine the site of porcine reproductive and respiratory syndrome virus (PRRSV) in individual houseflies, to assess whether an individual housefly could transmit PRRSV to a susceptible pig, and to compare the ability of PCR, virus isolation and a pig bioassay to detect PRRSV in houseflies. In the first experiment 26 houseflies were fed on a pig infected experimentally with PRRSV; 13 were processed as a whole fly homogenate, while an exterior surface wash and a gut homogenate were collected from the other 13. Infectious PRRSV was recovered from nine of the whole fly homogenates, 12 of the gut homogenates and one of the exterior surface washes. In the second experiment, two of 10 individual houseflies, which had fed on an infected pig, transmitted PRRSV to a susceptible pig in a controlled manual transmission protocol. In the third experiment, single flies or pools of 30 flies were immersed in different concentrations of a PRRSV inoculum, then tested by PCR, virus isolation and bioassay. The virus was detected at a concentration of 10(1) TCID50/ml by PCR, 10(2) TCID50/ml by the bioassay and 10(3) TCID50/ml by virus isolation.     

Influence of temperature and age on the recovery of pseudorabies virus from houseflies (Musca domestica)

In laboratory experiments, pseudorabies virus was readily recovered from within the body of houseflies (Musca domestica L) that had ingested the virus. Age of the fly and ambient temperature affected the rate of virus inactivation within the houseflies. Virus half-life in 3-day-old flies was 6.36 hours vs 2.81 hours in flies 8 or 13 days old. Half-life in 5-day-old flies was 12.92 hours at 10 C, 5.95 hours at 20 C, and 2.69 hours at 30 C. Virus half-life in dead flies was 9.06 hours at 10 C, 4.28 hours at 20 C, and 1.71 hours at 30 C. The data did not provide any evidence of virus replication in either living or dead flies.     

Further assessment of houseflies (Musca domestica) as vectors for the mechanical transport and transmission of porcine reproductive and respiratory syndrome virus under field conditions

The purpose of this study was to evaluate the potential for houseflies (Musca domestica) to mechanically transport and transmit porcine reproductive and respiratory syndrome virus (PRRSV) between pig populations under controlled field conditions. The study employed swine housed in commercial livestock facilities and a release-recapture protocol involving marked (ochre-eyed) houseflies. To assess whether transport of PRRSV by insects occurred, ochre-eyed houseflies were released and collected from a facility housing an experimentally PRRSV-inoculated population of pigs (facility A) and collected from a neighboring facility located 120 m to the northwest that housed a naïve pig population (facility B). All samples were tested for PRRSV RNA by polymerase chain reaction (PCR). To assess transmission between the 2 populations, blood samples were collected from naïve pigs in facility B at designated intervals and tested by PCR. A total of 7 replicates were conducted. During 2 of 7 replicates (1 and 5), PCR-positive ochre-eyed houseflies were recovered in facility B and pigs in this facility became infected with PRRSV. Chi-squared analysis indicated that the presence of PRRSV in an insect sample was significantly (P = 0.0004) associated with infection of facility B pigs. Porcine reproductive and respiratory syndrome virus was not recovered from other reported routes of transmission during the study period, including air, fomites, and personnel. In conclusion, while an insufficient number of replicates were conducted to predict the frequency of the event, houseflies may pose some level of risk for the transport and transmission of PRRSV between pig populations under field conditions.     

Transmission of Campylobacter jejuni by the housefly (Musca domestica)

Houseflies (Musca domestica) were infected with Campylobacter jejuni after being confined for 5 days in a Horsfall isolator containing 25-day-old chickens known to be fecal excretors of the organism. Contaminated flies, when subsequently transferred to a second unit, transmitted C. jejuni to specific-pathogen-free chickens. Allowing a sample of 32 houseflies to ingest C. jejuni in a liquid suspension resulted in recovery rates of 20% from the feet and ventral surface of the body and 70% from the viscera. These experiments demonstrated the potential role of flies in the dissemination of avian campylobacteriosis.     

Digestion of poultry manure by Musca domestica

Larvae of the house fly (Musca domestica) grew and developed normally in fresh poultry manure where the proper environmental conditions were maintained. A temperature of 27 °C and a moisture content ranging from 60 to 75% in fresh poultry manure was determined to be optimum for larval development. A moisture content of 80% or greater created anaerobic problems for larvae.

Optimum production of house fly pupae was obtained by inoculating 0.50 to 0.75 g of fly eggs per kg of fresh poultry manure. Five to eleven days were required for the eggs to be converted to pupae depending on the environmental conditions. After digestion, the poultry manure, was reduced to about half and was granular in texture. The digested residue readily dried, had less odour and contained approximately 15% protein.     

Identification of porcine transmissible gastroenteritis virus in house flies (Musca domestica Linneaus)

Transmissible gastroenteritis (TGE) virus was detected in house flies (Musca domestica Linneaus) by staining with specific fluorescent antibody. The flies were collected within a swine confinement facility in which TGE was enzootic. Laboratory-reared flies were infected experimentally with TGE virus and the virus was recovered from the insects for 72 hours after infection. The TGE virus was identified both by the fluorescent antibody technique and by isolation in cell culture. The nature of plaque formation in cell monolayers inoculated with the virus passaged through flies changed from a large plaque (4 mm or greater in diameter) to a small plaque (1 mm in diameter) over the period. Large plaques were observed early after infection and were attributed to TGE virus mechanically carried by the flies. Small plaques occurred 8 to 12 hours after infection and were considered to be produced by virus replicated in the dipterous cell.     

家蝇基因工程抗菌肽的研究进展

家蝇抗菌肽因具有独特的防御机制且不易产生耐药性而成为国内外科研工作者的研究热点,其在动物疫病防治上的应用也越发引人关注。利用基因工程技术获取家蝇抗菌肽能克服传统方法产量低、耗时长、无法实现大规模生产等缺点,是目前获取家蝇抗菌肽最为有效的方法。对家蝇基因工程抗菌肽的分类、编码基因的获得和表达以及生物活性方面进行了综述,以期为兽医临床早日研制出高效、低毒且不易产生耐药性的新兽药提供参考。     

Characterization of turkey coronavirus from turkey poults with acute enteritis.

The present study was to characterize turkey coronavirus associated with turkey poult enteritis and mortality. Intestinal contents or intestines from affected turkey poults and inoculated turkey embryos contained coronaviruses as revealed by electron microscopy or were positive for turkey coronavirus by immunofluorescent antibody assay. Sucrose density gradient ultracentrifugation of the virus-containing intestinal homogenate yielded two opalescent bands corresponding to the buoyant densities of 1.14-1.15 and 1.18-1.20 g/ml, respectively. Coronaviral particles from intestinal contents or the sucrose density gradient preparation were mainly spherical in shape and had envelope and central depression. They were surrounded by a fringe of regularly spaced petal-shaped projections attached to the particles by a short stalk. Purified viruses hemagglutinated rabbit erythrocytes with a titer of 16. Major protein bands of purified viruses analyzed by SDS-PAGE were located at 200, 100-110, 50-60, and 30-35 kDa. The patterns of protein bands were consistent with those of Minnesota or Quebec turkey coronavirus isolates. A 568 bp nucleotide fragment of turkey coronavirus spike protein gene was amplified from RNA of inoculated turkey embryo intestine or purified virus. Sequence analysis of the 568 bp PCR product revealed high degree of identity with the corresponding spike protein gene sequence of human and bovine coronaviruses. The results indicated that turkey coronavirus was associated with turkey poults with acute enteritis.     

家蝇抗菌肽的研究进展马红霞

从家蝇抗菌肽的分类、结构特点、作用机理、诱变、活性检验以及分子生物学研究等方面介绍了家蝇抗菌肽的研究进展。家蝇抗菌肽独特的作用机理、成熟的诱导、分离纯化技术及其相关基因的克隆、表达等研究成果均为对家蝇抗菌肽进行更深入的研究奠定了基础。采用分子生物学技术有望筛选并制备大量的高效家蝇抗菌肽。