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Comparative efficacy of injection routes and doses of ivermectin against Psoroptes in rabbits.

Rabbits infested with Psoroptes ovis (Hering) or with P cuniculi (Delafond) were injected IM or subcutaneously with ivermectin or with vehicle. A single injection of ivermectin (200 micrograms/kg) either IM or subcutaneously was inadequate to eliminate all mites in the ears of the rabbits. However, a single injection of ivermectin at 400 micrograms/kg, regardless of the route of injection, eliminated all P cuniculi mites, but eliminated P ovis mites in only 50% of the rabbits. Ivermectin was more effective against P cuniculi than against P ovis at both doses tested, regardless of the route of injection.

Animals↗

Spread and detection of psoroptic scabies of cattle in the United States.

Psoroptic scabies of cattle causes substantial economic losses. An eradication program begun in 1905 virtually eradicated the disease by 1950. Complacency was followed by a resurgence of the disease, particularly in the 1970s, when more than 1,000 outbreaks were reported. Program effectiveness was reduced when the disease was often not detected or reported for several months after herds became infested. Further spread was enhanced by infested cattle moving undetected through market channels.

Animals↗

Infestation potential of Psoroptes ovis (Hering) from cattle injected with ivermectin.

Cattle scabies mites, Psoroptes ovis (Hering), surviving on cattle injected subcutaneously with ivermectin were capable of infesting to unprotected cattle 3, 5, 7, and 9 days after injection. All recipient cattle exposed to mites from vehicle-injected cattle developed reproductive colonies in 5 weeks. All recipient cattle exposed to mites from ivermectin-injected cattle at 3 and 5 days after injection developed reproductive colonies in 5 weeks. By 8 weeks, 3 of 4 and 2 of 4 recipient cattle exposed to mites from ivermectin-injected cattle 7 and 9 days after injection, respectively, developed reproductive colonies. To prevent the spread of mites, injected cattle should be isolated from uninfested cattle for longer than 9 days.

Animals↗

Control of psoroptic scabies on calves with ivermectin.

Eleven Hereford or Angus-cross calves slightly to severely infested with common scabies mites (Psoroptes ovis) were treated with 22,23-dihydroavermectin B1a (ivermectin) at dosages given subcutaneously (SC)--300 micrograms/kg; orally--400 micrograms/kg; or IM--50, 100, or 200 micrograms/kg. At 14 days after treatment, live mites were not found on any of the calves treated SC or IM, but live mites were found on all of the orally treated calves at 14 days and on 1 of them at 28 days after treatment. Four nontreated calves retained their mite infestations during the course of the IM test. Biting lice (Bovicola bovis) were eliminated from 1 calf treated SC, but not from calves treated IM. Ear ticks (Otobius megnini) were not noticeably affected.

Animals↗

Treatment of psoroptic mange with avermectins.

Good control of Psoroptes cuniculi was achieved in rabbits treated with various avermectin analogues by topical application or by subcutaneous injection of the 22,23-dihydroavermectin B1.

Administration, Topical↗

Infestivity of Psoroptes cuniculi in rabbits.

Starving Psoroptes cuniculi were found to survive off the host for 4 to 21 days at relative humidities between 20% and 99% and temperatures between 5 and 30 C. Within these extremes, survival was greatest at low temperature and high relative humidity (RH). Mites were infestive for at least 50% of their survival times and may have infested new hosts in contaminated facilities. A temperature of 40 C and 20% RH maintained for 24 hours caused 100% mortality in test mites. Other selected combinations of temperature above 40 C and RH less than or equal to 75% also caused 100% mortality in 2 days or less. These conditions could be used to control these mites in vacated contaminated premises.

Animals↗

Psoroptic ear mites in dairy goats.

Of 24 adult dairy goats examined at necropsy, 21 were found to be infected with ear mites (Psoroptes cuniculi), but none had gross signs of ear scab. Clinical examination of approximately 200 live adult goats on 23 farms revealed ear scabs in only one animal; however, the frequency of head shaking and ear scratching was high. On one farm with 170 lactating does, most of 25 kids examined within 6 weeks of birth were found to be infested. Serial examination of growing kids on another farm revealed mites in the ears of kids by 10 days of age. The onset of clinical signs of ear mite infestation was evident in all kids on the property during the 3rd week of life. In one instance when infested adult goats and kids were penned with adult sheep and lambs, there was no evidence of cross infestation.

Animals↗

[Effectiveness of moxidectin (Cydectin inj.) in mixed Psoroptes ovis and Sarcoptes ovis infestations in sheep].

Field efficacy of moxidectin injectable was evaluated in sheep naturally infected with both Psoroptes ovis and Sarcoptes ovis mange. Three groups of fifteen ewes were selected from the flock based on parasitological and clinical status. Group 1 remained as untreated controls. Group 2 animals received a subcutaneous injection of moxidectin at 0.2 mg/kg body weight on Day 0; Group 3 animals received 0.2 mg/kg moxidectin twice on Day 0 and Day 7. Efficacy was assessed by taking skin scrapings from each animal on Days -4, 0, 7, 14, 28 and 35 post treatment (P.T.) and counting viable mite stages and species. In both treated groups the signs of itching disappeared within seven days P.T. Rapid clinical improvement was associated with reduction in numbers of mites compared with initial score which was over 90%. However, in skin scrapings on Day 7 P.T. several live mites of both species were present. The second injection of moxidectin removed all living mites and skin scrapings from group 3 animals that were negative for all mites on days 14, 28 and 35. The weight gain on average in group 2 was 2.0 kg and in group 3 2.7 kg, during the 35 days of trial. Untreated control animals have lost on average 3.1 kg from the weight at start of trial. All untreated animals remained positive and suffered from intensive scratching, anorexia and moist active skin lesions. Therefore they were given an emergency moxidectin treatment on days 35 and 37 each animal receiving 0.2 mg/kg b.w., subcutaneously. Moxidectin in both tested doses was well tolerated and no local reaction on injection sites was observed.

Animals↗

Acaricidal agents of natural origin against Psoroptes cuniculi.

Lavandula angustifolia Miller essential oil and some of its main constituents, i.e. linalool, linalyl acetate, and camphor were tested in vitro for their bioactivities against Psoroptes cuniculi (Delafond, 1859), mite of the rabbit. The essential oil and linalool were found to have very powerful miticidal activities.

Acyclic Monoterpenes↗

Immune recognition of Ornithodoros tick (Acari: Argasidae) salivary antigens by anti-Psoroptes cuniculi antibodies.

Rabbits infested with either Ornithodoros sp. ticks or Psoroptes cuniculi mites were assayed for anti-tick antibody by enzyme-linked immunosorbent assay. Titration of rabbit serum against Ornithodoros sp. salivary gland extract (SGE) demonstrated both mite- and tick-infested animals to have elevated anti-tick antibody titers. Western blot analysis demonstrated the anti-mite and anti-tick antisera to contain antibodies with affinities for both common and unique subsets of Ornithodoros SGE proteins.

Animals↗

Antigens of the sheep scab mite Psoroptes ovis.

Sheep scab caused by the mite Psoroptes ovis (Hering) is a highly contagious disease of sheep. As a first step in developing a mite-derived vaccine for controlling the disease, the soluble antigens in mite extracts which induce an immune response in sheep were identified by electrophoretic and immunoblotting techniques. At least 22 proteins were present in P. ovis extracts as revealed by Coomassie Blue staining. Mite-infested sheep serum recognised six antigenic bands in the extracts with approximate relative molecular weights ranging from 12 to 183 kDa. A deeply staining band at 31.2 kDa and another at 41.8 kDa are of particular diagnostic value. Immunoblotting studies showed that there was no cross reactivity between P. ovis and two other ectoparasites of sheep in the UK, the sheep louse Bovicola ovis (Schrank) and the sheep tick Ixodes ricinus L.

Animals↗

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.

Animals↗

The pathology of Psoroptes ovis infestation in cattle with a special emphasis on breed difference.

In cattle, infestations with P. ovis are responsible for a severe dermatitis. The disease is very common in some breeds of beef cattle whereas dairy cattle such as Frisian Holstein are considered as resistant. In order to investigate the factors responsible for this marked breed susceptibility, the immune response to P. ovis under experimental and field conditions has been studied using serology, lymphocyte transformation assay, intradermal tests and passive cutaneous anaphylaxis in susceptible Belgian White and Blue (BWB) and resistant Frisian Holstein (FH) cattle. The results of published studies are reviewed in this paper; original data on specific hypersensitivity reactions to P. ovisare also presented. The use of a sandwich ELISA allowed the detection of specific antibodies as early as 7 days post-infestation and very high titres were observed. There was a clear positive correlation between the antibody titre and the extent of lesions. This antibody response was associated with a marked in vitro lymphocyte proliferation but there was no difference between susceptible and resistant cattle. The passive cutaneous anaphylaxis test revealed the presence of specific Ig E in actively infested animals irrespective of the breed. Specific Ig E were detected fairly late during the course of an experimental infestation with P. ovis. The intradermal injection of P. cuniculi antigenic extract induced an immediate reaction in all animals including the controls; in contrast, a delayed hypersensitivity reaction was observed in infected BWB animals only. It is concluded that immunological as well as non-immunological factors may be responsible for the breed related susceptibility or resistance to P. ovis.

Animals↗

The behaviour of sheep with sheep scab, Psoroptes ovis infestation.

Methods of behavioural data collection as applied to the study of sheep scab are described. The behaviour of a number of marked animals within an affected flock was recorded using an event recorder. Focal sampled data were analysed for duration and frequency of the observed behaviours. In addition, the flock was observed at intervals and the instantaneous behaviour of each animal recorded. These data were compared with similar observational data from the same flock recorded at intervals during post-treatment recovery. Sheep scab resulted in pathological behaviours of rubbing, scratching and biting at the lesion, and these resulted in interruption of the normal behaviours, grazing, cudding and idling, but did not result in reduced levels of these behaviours. Infested sheep showed stereotypic mouthing behaviour, initiated by rubbing or scratching, or in some cases without any external stimulus. No stereotypic behaviour was seen in animals after treatment. The implications of the behavioural data for the welfare of the sheep is discussed.

Analysis of Variance↗

The use of moxidectin for the prevention and treatment of psoroptic mange (scab) in sheep.

The introduction of systemic injectable products, belonging to the avermectin/milbemycin class of antiparasitic compounds, has provided an alternative to dips for sheep scab control. Their main advantages are that they are quicker and safer to use, cause less stress to the sheep (hence can be used in heavily pregnant ewes), do not require any special handling facilities for their use and do not present the same environmental concerns over disposal of spent product. Moxidectin, a second generation milbemycin, has recently been registered as an injectable product for the prevention and treatment of sheep scab. Laboratory and field studies carried out in the UK and Ireland have shown that two injections at a dose rate of 200 mg/kg bwt., 10 days apart, are 100% effective in the treatment of scab. Further studies have shown that a single injection at the same dose rate will protect against infestation or reinfestation for a period of at least 28 days. This long persistent activity has been evaluated in two large-scale field prophylactic trials, one in Ireland and one in the UK, involving over 16,000 sheep, in which it was demonstrated that a single injection of moxidectin is a safe and effective alternative to dips for routine prevention of scab.

Administration, Topical↗

Characterisation of aminopeptidase activity in scab mites (Psoroptes spp.).

Soluble and membrane-bound aminopeptidase activities were demonstrated in extracts of P. cuniculi (Delafond). Leucine aminopeptidase (LAP) activity in the soluble fraction of P. cuniculi extracts displayed substrate preference for amino acid derivatives with terminal leucine and methionine over those with acidic, basic or heterocyclic groups. P. cuniculi LAP was inhibited by leucinethiol (IC(50) = 1.4 +/- 0.4 nM), bestatin (IC(50) = 3.9 +/- 1.7 microM), Arphamenine A (IC(50) = 0.37 +/- 0.03 mM) the chelating agent 1,10-phenanthroline (IC(50) = 2.3 +/- 0.5 mM), Zn(2+), Cu(2+) Ni(2+), and Co(2+), and activated by Mn(2+) and Mg(2+). The LAP activity was visualised as a single major band after electrophoresis on native gels and eluted from a size exclusion column as a single major peak representing a molecular mass range of 85-116 kDa. Degenerate oligonucleotide primers were used to amplify short fragments of genomic DNA containing nucleotide sequence coding for the cation-binding motifs of the co-catalytic Zn(2+) binding domains of dizinc leucine aminopeptidases in both P. cuniculi and P.ovis (Hering). The major soluble aminopeptidase from these mites therefore displays most of the characteristics associated with typical cytosolic leucine aminopeptidases belonging to the M17 family of metalloproteinases.

Animals↗