Sheep Scab Mite Research Articles

The in vitro response of sheep scab mites to pyrethroid insecticides

The response of sheep scab mites to pyrethroid insecticides and organophosphate compounds was studied in vitro with the objective of finding a simple test for detecting insecticide resistance in scab mites. Psoroptes cuniculi from rabbits or P. ovis from sheep were enclosed in small ‘tea bags’ made from heat sealable paper prior to dipping in insecticide. Mites failed to die 24 h after a 1 min dip in working concentrations of insecticidal sheep dips. With flumethrin a variety of different conditions were tested but most failed to improve the efficacy of flumethrin. It is suggested with freshly collected mites pyrethroids may be taken up by ingestion.

The construction of a cDNA expression library for the sheep scab mite Psoroptes ovis

The need for alternative control strategies for sheep scab is critical. One approach is to develop vaccines based on ‘concealed’ antigens derived from Psoroptes ovis. This strategy requires the identification and characterisation of potential target antigens, which has been hampered by the problem of limited biological material for isolation of protein antigens. To aid the discovery of P. ovis antigens and to provide a resource for generating recombinant protein, we constructed a P. ovis cDNA expression library, using total RNA isolated from 250 mg of mixed-stage P. ovis and the Clontech SMART™ cDNA synthesis kit. The presence of P. ovis-specific sequences was confirmed using PCR amplification and sequencing of actin. The sequences of cDNA inserts from six random clones included one with high homology to the Dermatophagoides pteronyssinus (house dust mite) antigen p Dp15. This is a glutathione S-transferase known to be an important house dust mite antigen. We conclude that this library will be a useful tool for the identification of potential target antigens for the immunological control of P. ovis and to further our understanding of the pathology of sheep scab.

Sheep Scab Mite (Acari: Psoroptidae): General Morphology and Immunocytochemistry Using Serum from Infested Animals

The basic morphology of the digestive, reproductive, and nervous Systems of the sheep scab mite, Psoroptes ovis Hering, was defined by light microscopy. An understanding of the stricture of the digestive system of P. ovis is prerequisite to identification of target antigens in specific regions of the digestive tract using immunocytochemistry. Sera from a mite-infested animal and an animal with repeated mite infestations no longer able to maintain a population of P. ovis (acquired resistance) were used to determine antibody specificity to the mite digestive system, and these were compared with the sera from uninfested animals. Sera from naive animals with mite infestations and those animals with repeated infestations had antibodies that were specific against the digestive tract, whereas sera from uninfested control animals did not demonstrate any antibody specificity to mite antigens. Immunocytochemistry demonstrated that polyclonal antibodies to mite gut antigens were present in infested naive animals as well as in multiply infested animals, indicating that gut antigens have a possible role in host resistance.

Isolation of the gram-negative bacterium, Serratia marcescens, from the sheep scab mite, Psoroptes ovis.

Veterinary RecordVolume 138, Issue 9 p. 210-211 Short Communication Isolation of the Gram-negative bacterium, Serratia marcescens, from the sheep scab mite, Psoroptes ovis B. R. F. Mathieson, B. R. F. Mathieson School of Biological Sciences, University of Wales, Bangor, Gwynedd, LL57 2UWSearch for more papers by this authorM. J. Lehane, M. J. Lehane School of Biological Sciences, University of Wales, Bangor, Gwynedd, LL57 2UWSearch for more papers by this author B. R. F. Mathieson, B. R. F. Mathieson School of Biological Sciences, University of Wales, Bangor, Gwynedd, LL57 2UWSearch for more papers by this authorM. J. Lehane, M. J. Lehane School of Biological Sciences, University of Wales, Bangor, Gwynedd, LL57 2UWSearch for more papers by this author First published: March 1996 https://doi.org/10.1136/vr.138.9.210Citations: 6 Correspondence to Dr Lehane. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume138, Issue9March 1996Pages 210-211 RelatedInformation

Examination of possible transmission of sheep scab mite Psoroptes ovis between host species.

Examination of possible transmission of the Irish strain of the sheep scab mite (Psoroptes ovis) of ovine origin between host species involved calves and goats being placed with infected sheep and also directly challenged with live mites. Although mites remained on recipient species for up to a week, they failed to produce disease in either of these species. Calves and goats that had live mites placed on them likewise failed to infect sheep with which they were housed.

Haematological and immunological response of unrestrained cattle to Psoroptes ovis, the sheep scab mite

Cows were infected twice with 600 and 500 nymphs and adults of a bovine strain of Psoroptes ovis with a nine-week interval. The haematological response and the non-specific mitogen- and antigen-induced responsiveness of the peripheral blood lymphocytes of the animals was followed. Dermal reactivity to P ovis antigen injection was studied five weeks after reinfection. After the first infection with 600 mites none of the infected animals developed clinical psoroptic mange but a leucocytosis developed, contributed to primarily by an eosinophilia and by a slight lymphocytosis. Antigen-induced lymphocyte blastogenesis was used to measure the antigen-sensitive cell population in peripheral blood and this population showed a maximum increase 10 days after infection; however, antigen-sensitive cells remained above normal levels until reinfection. Upon challenge infection with 500 mites the infected animals showed an immediate hypersensitivity type reaction with a marked pruritus, scratching and exudation. Thereafter the lesions healed rapidly and none of the animals developed clinical mange. This clinical reaction was accompanied by a secondary eosinophilia but no change was apparent in the other blood elements. A marked increase in the blastogenic response of the peripheral blood lymphocytes was also apparent and this peaked three weeks after challenge. Following the intradermal injection of P ovis antigen there was an immediate swelling of the injection site in all infected and control animals and skin thickness was maximal one hour after injection. Thereafter there was a clear distinction in dermal reactions between P ovis infected and control animals; after 48 hours reactions were not seen in the control animals while marked dermal reactions were still present in the P ovis infected group.

Enzyme-linked immunosorbent assay for the detection of antibodies to the sheep scab mite Psoroptes ovis

An enzyme-linked immunosorbent assay has been shown to detect antibodies in the circulation of sheep infected with Psoroptes ovis. Strong positive reactions were obtained from 19 sheep with four-month-old infections. No cross reaction was observed with sera obtained from sheep infected with either Fasciola hepatica, Nematodirus battus, Ostertagia circumcincta or Damalinia ovis.

Some observations on the biology and control of the sheep scab mite Psoroptes ovis (hering) in Britain

Sheep scab was eradicated from Britain in 1952 but reappeared in 1973. The host specificity of the sheep scab mite is discussed; sheep are the only reservoir of the disease in Britain. Control is by single dipping in the approved acaricides, HCH, diazinon or propetamphos. Acaricides are approved only if the minimum use rate (maintenance level) will give at least 4 weeks' protection. The method of testing is described. Traditionally, compulsory dipping has been in the winter when the disease is most active. Although the mites were originally thought to enter a latent phase during the summer, new observations indicate that there is little difference between their summer and winter behaviour. In Britain, dipping is now compulsory in both the summer and winter.

Susceptibility of Hereford cattle to sheep scab mites after recovery from psoroptic scabies.

Cattle scabies is caused by Psoroptes ovis (Hering), and Hereford cattle with a history of psoroptic scabies were as susceptible after reexposure to P. ovis as cattle exposed for the first time. The first reexposure of cattle to P. ovis after a 5-month latency period failed to cause psoroptic scabies. But a second reexposure resulted in body scab as extensive as that on naive cattle. Cattle free of P. ovis infestation for 4 months after toxaphene treatment developed scabies with as many mites as cattle exposed for the first time. Two cattle had severe scabies with many mites only while stanchioned and unable to groom. The data indicate that cattle after a 2- to 5-month period of latency or recovery from scabies because of pesticide treatment are as susceptible to P. ovis as cattle exposed for the first time. Self grooming behavior was the only factor which consistently limited the size of P. ovis populations.

Ingestion of Rabbit Erythrocytes Containing 51Cr-Labeled Hemoglobin by Psoroptes Spp. (Acari: Psoroptidae) that Originated on Cattle, Mountain Sheep, or Rabbits1

Washed rabbit erythrocytes labeled with radioactive chromium in vitro were injected into 3 groups of 2 adult rabbits each. One group was heavily infested with the sheep scab mite, Psoroptes ovis ; the 2nd group was infested with Psoroptes mite from Mexican Mountain Sheep, and the 3rd group was infested with the ear canker mite, P. cuniculi . After 36 h, mites and scabs were harvested and the radioactivity determined. At time of collections, mites from all groups had an average of 8.9 ± 2.0 μl of blood per 100 mg of mites. More than 70% of the consumed hemoglobin had been digested by the mites. The data suggest that the ingestion of whole blood is not specific to a particular mite species but may be common to Psoroptes mites when feeding on rabbit hosts.

Feeding of Psoroptes ovis (Acari: Psoroptidae) on cattle.

Washed bovine erythrocytes labeled in vitro with radioactive chromium were resuspended in physiological saline and injected into an 11-month-old Hereford heifer that was heavily infested with the common scabies (sheep scab) mite of cattle and sheep, Psoroptes ovis . After 24 h the mites were harvested and the radioactivity measured. The mites contained an average of 1 μl of blood per 100 mg of mites and had digested ca. 37% of the hemoglobin. The data show that P. ovis mites ingest erythrocytes during feeding on cattle but not to the extent that they do while feeding on rabbits as determined in an earlier study.

Seasonal Independence and Relative Frequency of Motile Stages of Scab Mites, Psoroptes ovis,1 on Sheep

A study was made of possible seasonal influences on the relative abundance of the 7 motile stages of Psoroptes ovis (Hering), the sheep scab mite. Observations covered the 25-month period from Nov. 1965 through Nov. 1967, and March and April in 1971. One collection was made each calendar month, wherein all of the mites from a one-inch square of skin surface, at the site of an active lesion, were removed, counted, permanently mounted and identified. Although the overall parasite population was greater during the winter than in summer, there was no evidence that climatic influences at any time altered the frequencies of the components in relation to the whole population. On sheep where infestations survived the hot summer months, all stages were represented in each of the collections. There was no evidence of diapause.

Oversummering Location of Scab Mites, Psoroptes ovis,1 on Sheep in New Mexico

In the Southwest, during summer, sheep scab mites, Psoroptes ovis (Hering) (Acarina: Psoroptidae), are quiescent and are rarely associated with clinical symptomatology. A search for these mites, conducted each summer from 1961 through 1968 (except for 1965), involved 274 sheep, all of which were known to have heavy winter and spring infestations of scab mites. Each sheep was examined at least once between June and September for mites in suspected hiding places and on the broad body surfaces. Live mites, or dead mites found on swabs after potassium hydroxide maceration, occurred in midsummer in hiding places on only 7% of the sheep. Live mites occurred on major skin surfaces on 32% of the sheep. Thus, P. ovis may survive the summer anywhere on the body surface, including skin invaginations. However, the primary survival areas are the major body surfaces, where mites are in greatest number and where serous encrustations and the wool umbrella provide adequate summer shelter.

Variations among Strains of Psoroptes ovis (Acarina: Psoroptidae) on Sheep and Cattle

Evidence is presented to support the position that distinct strains of the common sheep scab mite, Psoroptes ovis (Hering), may exist. Differentiation between strains is based on observations that (1) some strains withstand population reduction more successfully than others during summer months, (2) members of such strains survived contact with the acaricide coumaphos, in contrast to less aggressive strains against which comparable coumaphos formulations were completely effective, (3) populations of these highly pathogenic strains survived longer than avirulent strains on sheep held in individual isolation, and (4) aggressive strains of mites of sheep origin were able to spread within herds of cattle more rapidly, and produce more obvious clinical responses than less pathogenic strains. Difficulties experienced in the eradication of scab from sheep and cattle in the United States are believed to be related, at least in part, to the existence of persistent, drug-resistant strains of mites.