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PubMed2004

Growth and pathogenicity of isolates of the fungus Metarhizium anisopliae against the parasitic mite, Psoroptes ovis: effects of temperature and formulation.

Psoroptes mites (Acari: Psoroptidae) are important ectoparasites of mammals, and are of particular economic significance as the agents of mange in sheep. To be effective against mites, putative fungal biocontrol agents must be able to operate at the relatively high temperatures and humidities found at the sheep skin surface. To consider this, the growth rates of different isolates of the entomopathogenic fungus Metarhizium anisopliae (Metschnikoff) Sorokin (Deuteromycotina: Hyphomycetes) were compared and the pathogenicity of these isolates against Psoroptes derived from rabbits (Psoroptes ovis Hering, syn P cuniculi) were evaluated at temperatures between 28 degrees C and 40 degrees C, and when formulated in either Tween 80 or silicone oil. For this study four multi-conidia, arthropod-derived, isolates of M anisopliae were used: from the USA, France, Denmark and Brazil. One single-conidia culture derived from the US isolate was also included in the investigation. Fungal growth was higher at the lower temperatures and none of the isolates grew at 40 degrees C. The growth of the US and single-conidia isolate declined markedly with temperature. In contrast, the Danish, French and Brazilian isolates grew almost as well at 32 degrees C and 35 degrees C as at 28 degrees C and 30 degrees C. The French and Brazilian isolates showed some growth at 37.5 degrees C but the Danish and US isolates did not. The number of fatal infections which resulted from exposure of mites to the fungal isolates was also strongly influenced by temperature. At 30 degrees C all isolates gave between 70 and 90% infection. The number of infections declined with increasing temperature and no infections were seen at 40 degrees C. However, the French and Danish isolates of M anisopliae gave higher numbers of infections than the other isolates at elevated temperatures. When formulated in silicone oil, significantly higher levels of infection were obtained than when formulated in Tween 80, even at the relatively high temperature of 37.5 degrees C. It is suggested that high-temperature adapted isolates of M anisopliae formulated in silicone oil offer good candidates as control agents under the conditions found at the sheep skin surface.

Animals↗

PubMed1996

A sandwich enzyme-linked immunosorbent assay to study the antibody response against Psoroptes ovis in cattle.

A sandwich enzyme-linked immunosorbent assay (ELISA) was developed using polyclonal antibodies from Psoroptes cuniculi infested rabbit and a crude P. cuniculi antigen. Sera from 133 Psoroptes ovis infested and 137 uninfested cattle were serially diluted from 1:100 to 1:102,400 and analyzed. Curves obtained by plotting log dilution versus optical densities (OD) were used and a working dilution of 1:400 was selected. Positive/negative cut-off values were calculated using the mean OD percentage (6%) of all negative sera plus 3 standard deviations. Sensitivity and specificity according to the resulting cut-off (25%) were 98.5% and 97.8% respectively. Expressed as the dilution giving the cut-off value, results in ELISA revealed a wide range of antibody titres (from 1:19 up to 1:2,240,000) with a geometric mean value of 1:35,480, and this is probably related to the well-described hyperglobulinemia in P. ovis infestations. In two trials performed at a 1 year interval, 19 Belgian White and Blue and six Fresian-Holstein calves were experimentally infested, and sensitivity and specificity were calculated throughout the experimental period. Sensitivity reached 78% on day 70 in trial 1 and 100% on day 49 in trial 2 (sensitivity was calculated using data from three control animals, three infected Fresian-Holstein animals and seven (trial 1) or six (trial 2) infected Belgian White and Blue animals). Specificity on day 0 was 100% in trial 1 and 92% in trial 2. At the end of both trials, specificity decreased in 80%. The development of the serum antibody activity to Psoroptes antigens was correlated with the development of lesions: in trial 1, the coefficient of correlation between the percentage of body surface with lesions and antibody titre was 0.82 (probability of no relationship P < 0.005) on day 56 post-infection (PI) and in trial 2, 0.83 (P < 0.025) and 0.87 (P < 0.025) on days 35 and 63 PI respectively.

Animals↗

PubMed2006

In vitro entomopathogenic activity of Beauveria bassiana against Psoroptes spp. (Acari: Psoroptidae).

An indigenous strain (IHEM 18747) of Beauveria bassiana (Balsamo) Vuillemin (Deuteromycetes) was evaluated for its in vitro entomopathogenic activity against the parasitic mite Psoroptes ovis Hering (Acari: Psoroptidae) from rabbits. The following aspects were evaluated: (1) effects of conidial concentration on the viability of adult females; (2) influence of the infection on the fertility, and on the hatchability of eggs; (3) and transmission of infection between mites, and from contaminated surface. Adult females immersed into increasing concentrations of conidia (10(4)-10(9)conidia ml(-1)) showed a dose-related susceptibility. At the highest concentration of conidia, LT50 was 1.6 days while LT50 of the controls reached 5.8 days. The fungus was able to sporulate on the body surface and 100% of the mites were covered with mycelium after immersion in solutions containing 10(7)-10(9)conidia ml(-1). One hundred percent of healthy mites exposed to infected cadavers or surfaces acquired the infection (LT50 reached 1.9 and 1.73 days, respectively, versus 6.1 and 5.1 days in controls, respectively). Egg laying was not reduced by the fungal infection but both the hatchability of the eggs and the life span of the emerging larvae were significantly reduced. Eggs directly infected with the fungus did not show reduced hatchability but the life span of the larvae was shortened. It is concluded that B. bassiana has a high entomopathogenic activity against Psoroptes spp. The in vivo use of this biocontrol agent against Psoroptes spp. in rabbit, sheep and cattle deserves further attention.

Animals↗

PubMed2000

Field efficacy of moxidectin in dogs and rabbits naturally infested with Sarcoptes spp., Demodex spp. and Psoroptes spp. mites.

The efficacy of moxidectin 1% injectable for cattle was evaluated in dogs and rabbits with naturally acquired sarcoptic, demodectic or psoroptic mites. Twenty-two dogs with generalised demodicosis were orally treated with 0.4mg/kg moxidectin daily. Forty-one dogs suffering from sarcoptic mange were treated with 0.2-0.25mg/kg moxidectin either orally or subcutaneously every week for three to six times. Seven rabbits were treated orally with 0.2mg/kg moxidectin twice 10 days apart. Of the 22 dogs with demodicosis, 14% were stopped treatment because of side effects, 14% were lost and of the remaining 72% all were cured (mean therapy duration 2.4 months). Thirty-seven of the sarcoptic mange-infected dogs finished treatment and were cured. In 17% of dogs, side effects were noted. All seven rabbits treated for psoroptic mange were cured and did not show any side effect. Our results indicate that moxidectin is effective and a good alternative for the treatment of demodicosis and scabies in dogs and psoroptic mange in rabbits. Side effects seem to occur more frequently if applied subcutaneously, therefore the oral route should be preferred.

Animals↗

PubMed2001

Diagnosis of psoroptic sheep scab with an improved enzyme-linked immunosorbent assay.

An enzyme-linked immunosorbent assay (ELISA) was developed for the detection of specific antibodies against crude Psoroptes antigen. The diagnostic sensitivity was 93.7% in 191 sheep with clinical signs associated with mange. These animals originated from 29 flocks in which psoroptic mites were detected. All of 59 sheep infested with Psoroptes ovis were seropositive. Additionally, in 49% of 70 clinically unaffected sheep originating from P. ovis-infested flocks, specific antibodies could be detected, suggesting that asymptomatic infestations can be diagnosed by serology. The specificity of the ELISA was 96.5% as determined with 254 sheep originating from 44 flocks without clinical mange. Cross-reactivity in a low range was detected with selected sera of sheep with clinical chorioptic or forage mite infestations. Four sheep seroconverted 2 weeks after experimental P. ovis infestation, i.e. 2 weeks before clinical signs became obvious. After successful doramectin treatment of 14 sheep with naturally acquired P. ovis infestation, the ELISA values declined slowly but remained positive in seven cases beyond 17 weeks.

Animals↗

PubMed1997

Treatment and prophylaxis of psoroptic mange of sheep by a 10% w/w dip formulation of high CIS-cypermethrin.

A 10% w/w dip formulation of high CIS-cypermethrin (Ecofleece sheep dip) was evaluated as a prophylactic and treatment method against Psoroptes ovis of sheep. A laboratory trial using groups of healthy sheep under challenge showed that, when dipped as directed for 1 min, they were protected against infection for at least 4 weeks. Twelve sheep infected with psoroptic mange at the laboratory were effectively treated by one dipping in Ecofleece. A field outbreak of psoroptic mange in a flock of 237 crossbred ewes was likewise successfully treated by just one dipping. As this formulation is also effective against blowfly myiasis it is a useful alternative to organophosphate dual purpose dips.

Animals↗

PubMed1999

Treatment of psoroptic mange with reference to epidemiology and history.

Treatment methods in the last century involved the use of substances such as sulphur, mercury, hellebore, arsenic, nicotine and others, applied in various ways. The advent of dips in 1843 signalled an advance. However, the biology of the mite, Psoroptes ovis, the epidemiology of sheep scab and the lack of persistence of the acaricides necessitated repeated laborious treatments to ensure success. In 1947 this changed with the use of organo chlorines (OCs) which had up to 3 months residual activity. The use of OCs led to the eradication of psoroptic mange of sheep in USA. Organo phosphates (OPs) were introduced in the late fifties and synthetic pyrethroids (SPs) in the early seventies. In 1985, due to sheep tissue residues, lindane (OC) was withdrawn from the market and this greatly reduced the capacity for effective sheep scab control. Before the arrival of the endectocidal avermectin, ivermectin in 1978 and its successful use as an acaricide in 1992, control of psoroptic mange was limited to plunge dipping. In 1994 moxidectin, a milbemycin, was found to be effective and to have the added benefit of at least 4 weeks persistent activity. Another avermectin doramectin was shown, in 1995, to successfully treat scab and recently an ivermectin bolus has been introduced which has a 100 days' activity and is fully therapeutic and prophylactic. Strict attention to detail in the use of injectable products is essential in order to achieve satisfactory results. Work is progressing on the use insect growth regulators (IGRs) and also on naturally occurring substances such as linalool, neem and lavender oil. At the CVRL Dublin, promising results have been achieved with neem and some IGRs. Other areas of interest are allemones, synergists, microclimate manipulation, sheep breed resistance and vaccines. Successful control depends on epidemiological knowledge, accurate diagnostic techniques, intimate knowledge of the mite's life cycle, its behaviour on and off the host, its macro and molecular biology, the nature of the pathogenesis of the disease, sheep husbandry practices, nutritional and environmental factors; also farmer awareness and attitudes. The variable responses of sheep to the mite, the unpredictable incubation period, course, manifestations and outcome make this an intriguing and perplexing disease. Ways to overcome these problems and to achieve possible eradication are discussed.

Acyclic Monoterpenes↗

PubMed2001

Infection of Psoroptes mites with the fungus Metarhizium anisopliae.

The astigmatid mite, Psoroptes ovis (Hering) (Acari: Psoroptidae), is an obligatory ectoparasite that causes psoroptic mange in a range of domesticated animals, particularly sheep, where the clinical disease is known as sheep scab. A series of laboratory assays were used to assess the use of the fungus, Metarhizium anisopliae (Metchnikoff) (Deuteromycotina: Hyphomycetes) as a biocontrol agent for P. ovis derived from rabbits (syn. P. cuniculi). The immersion of mites in a suspension of conidia of M. anisopliae resulted in the acquisition of fatal infections. The number of mites which developed infections increased significantly with the increasing concentration of the conidial suspension to which they were exposed; 77% of mites developed infections when exposed to the highest concentration used (1 x 10(8) conidia ml(-1)). Controls developed no fungal infections. Mites allowed simply to walk across a surface which had been treated with a suspension of conidia also acquired fungal infections; the number infected was again related to the concentration of conidia present. After contact for 24 h with a surface treated with 1 x 10(8) conidia ml(-1), 73% of the mites became infected. To determine whether dead infected mites could act as sources of infection, infected cadavers were placed in chambers with live uninfected mites. The uninfected mites acquired fatal infections from the cadavers; a higher ratio of infected cadavers to uninfected mites resulted in greater transmission of infection. The time after death of the infected cadaver was also an important factor influencing the number infected, 5-day-old cadavers were the most infective and 18-day-old cadavers the least infective. The results indicate that M. anisopliae is a good candidate control agent for Psoroptes mites.

Animals↗

PubMed2004

Tactic responses of the parasitic mite, Psoroptes ovis, to light and temperature.

The astigmatid mite, Psoroptes ovis (Hering) (Acari: Psoroptidae), is an obligate, non-burrowing ectoparasite of vertebrates, of particular economic importance in domestic sheep flocks where it causes clinical psoroptic mange. To help understand the behaviour which facilitates transmission via the environment, the responses of P. ovis derived from rabbits (syn. Psoroptes cuniculi) to temperature and light were examined in the laboratory. On a vertical surface of uniform temperature, the presence and direction of illumination had a significant effect on the distance and direction moved by the mites. In darkness or with illumination from both above and below, the mites moved relatively little, but this movement was upwards. In contrast, with illumination from above only, mites moved downwards. When the direction of the illumination was reversed so that it came from below only, the mites moved upwards. On a vertical surface with a temperature gradient, in darkness or with illumination from both above and below, the mites moved up or down towards the area of highest temperature, depending on whether this was above or below, respectively. However, the movement of the mites in response to the temperature gradient was strongly displaced up or down by the presence of unidirectional illumination from above or below, respectively. The results indicate that the movement of these mites is strongly directed towards areas of high temperature but away from higher light intensity. These behaviours might be expected to maintain the position of the mites on a host animal and help them locate the skin surface of a new host when displaced into the environment.

Animals↗

PubMed2002

Structure and function of the gnathosoma of the mange mite, Psoroptes ovis.

Mites of the genus Psoroptes (Acari: Psoroptidae) are obligate, non-burrowing, astigmatid ectoparasites of mammals. A detailed understanding of the morphology of the gnathosoma is an important step towards elucidation of the feeding behaviour of this mite and, hence, the pathology of psoroptic mange. Scanning and transmission electron microscopy were used to examine Psoroptes ovis (Hering) (syn. P. cuniculi). The gnathosoma is composed of an infracapitulum (hypostome), which forms the floor of an extended U-shaped pre-oral trough, bounded by laterally compressed palps and enclosing paired chelicerae. Distally, each palp terminates in a flap-like process and four tapered terminal sensillae. The floor of the infracapitulum is interrupted along its length by a dorsally projecting ridge. At the distal end of the infracapitulum are paired, grooved pseudorutellae and, between them, paired, ungrooved lateral lips. Between the lateral lips is a grooved, elongate labium. Medially, a pair of finger-like projections emanates from the paraxial walls of the palps and project anteriorly. Each chelicera is made up of fixed and mobile digits, with a cheliceral membranous fold articulating the two. The distal ends of both digits are chelated. For much of its length, the mobile cheliceral digit appears to lie within a fold formed by the infracapitular ridge, thereby creating a central channel between the chelicerae. It is suggested that this arrangement of elements may facilitate a two-way flow of liquid, where saliva flows down a central salivary canal and spills out onto the host's skin over the labium at the point where the chelated tips of the chelicerae meet and abrade the skin. Liquid food may move along the grooves of the pseudorutellae and then be sucked up a food canal formed by the paraxial walls of the palps and the outer wall of the chelicerae.

Animals↗

PubMed2007

Use of selamectin for the treatment of psoroptic and sarcoptic mite infestation in rabbits.

Selamectin, a novel avermectin compound, was evaluated for its efficacy against naturally occurring infestations of Psoroptes cuniculi and Sarcoptes scabiei. A total of 42 New Zealand rabbits with psoroptic mange and 37 Angora rabbits with sarcoptic mange were used in the present study. On day 0, infested rabbits were treated topically with either selamectin at minimum dose of 6 mg kg(-1) (6-18 mg kg(-1) for New Zealand rabbits, n = 31 and 10-12 mg kg(-1) for Angora rabbits, n = 23) or vehicle only (control groups, n = 11 for New Zealand rabbits, n = 14 for Angora rabbits). The efficacy of selamectin was assessed both clinically and parasitologically by the presence or absence of viable mites. Rabbits were scraped for sarcoptic mites on days 7, 14, 28, 42 and 56 and had otoscopeic and/or microscopic examination for the detection of Psoroptes mites on days 7, 14, 42 and 56. Fisher's exact test was used to assess differences between the vehicle and selamectin treatment in the number of rabbits without mites (cure rates) on each assessment date. It was found that significantly fewer selamectin-treated rabbits had mites detected on skin scrapings (for S. scabiei) or otoscopeic and/or microscopic examination (for P. cuniculi) (P < 0.01) than the vehicle group. Results of the present study suggest that selamectin is effective against naturally infestations of P. cuniculi and S. scabiei in rabbits.

Administration, Cutaneous↗

PubMed2000

Phylogeny and host specificity of Psoroptic mange mites (Acarina: Psoroptidae) as indicated by ITS sequence data.

We used molecular phylogenetic techniques to study the systematic relationships and host specificity of Psoroptes mange mites, which are pests of numerous domestic and wild ungulates. Phylogenetic analysis of DNA sequence data from the internal transcribed spacer region 1 (ITS1) of nuclear ribosomal DNA indicated that populations of Psoroptes are not host specific. Furthermore, the currently used taxonomy of Psoroptes is not concordant with the phylogeny derived from ITS1. During the course of the study, we discovered apparent paralogous ITS sequences within individual mites as a result of varying polymerase chain reaction reaction conditions. This finding concords with other studies of ITS and suggests a cautious approach when interpreting data from ITS sequences. Host DNA contamination was also found to be a significant problem in data collection, and we report on the development of methods to overcome the problems of contamination in parasitic mites.

Animals↗

PubMed1983

Psoroptic scabies in desert bighorn sheep (ovis Canadensis nelsoni) from northwestern Arizona.

Scabies due to infestation by Psoroptes ovis was monitored from 1979 through 1981 in Nelson's desert bighorn sheep in northwestern Arizona. Visual examinations for ear lesions and evaluations of ear scrapings were used to assess the prevalence of mites in sheep that were live-captured or killed during the hunting season. The prevalence of psoroptic scabies in live-captured sheep for the years 1979, 1980, and 1981, was 25%, 25%, and 0%, respectively, and was higher in rams (1979, 65%; 1980, 100%) than in ewes (1979, 11%; 1980, 0%). The severity of ear lesions was also greater in the males. The prevalence in harvested rams was 23%, 44%, and 7%, respectively, for the years 1979-1981. The severity of the ear lesions was highest in 1980. Lesions were confined to the ears. An aerial census of bighorns in the Black Mountains during May of 1981 showed a 38% decrease in total observations from the previous year and a drop in the ewe/lamb ratio from 0.52 in 1980 to 0.29 (P less than or equal to 0.01) in 1981. In the Lake Mead area, there was a population census decline of 33% in 1981 and a non-significant decline in the ewe/lamb ratio from 0.46 to 0.40. The population decline in 1981 and the increased prevalence and severity of psoroptic scabies in the 1980 survey in both areas were believed to be related to the high bighorn population densities in 1980 and the prevailing drought.

Animals↗

PubMed1997

Contact transmission of psoroptic mange from bighorn to Stone sheep.

Psoroptes sp. mites and tan crusty lesions were detected in the ears of a captive Stone sheep (Ovis dalli stonei) in April 1996, after contact with infected captive Rocky Mountain bighorn sheep (Ovis canadensis canadensis). Psoroptes spp. have not been detected in free-ranging ungulates in Canada or Alaska (USA). This is the first report of Psoroptes sp. in Stone sheep, indicating their susceptibility to infection.

Animals↗

PubMed1991

Kinetic ELISA for detection of antibodies to Psoroptes sp. (Acari: Psoroptidae) in bighorn sheep (Ovis canadensis).

A kinetic enzyme-linked immunosorbent assay (ELISA) was developed using antigenic extracts prepared from Psoroptes cuniculi mites and sera from 37 Psoroptes sp.-infested and 43 uninfested bighorn sheep (Ovis canadensis). Serial dilutions of these serum samples, representing 3 bighorn sheep subspecies and 9 geographic areas, gave parallel responses when plotted as log dilution versus log kinetic rate. Therefore, all 80 samples were run at a single dilution (1:100) and positive/negative cutoff values were established as the mean kinetic rate of all negative sera plus either 2, 3, or 4 standard deviations. The resulting ELISA was highly reproducible and accurate with sensitivities and specificities of 100% and 97.7%, 94.6% and 97.7%, and 94.6% and 100%, respectively. This immunoassay will be useful for prospective and retrospective studies assessing the distribution and prevalence of Psoroptes sp. infestations in bighorn sheep.

Animals↗

PubMed1984

Effect of ivermectin in heifers on mortality and egg production of Psoroptes ovis.

Ten stanchioned heifers, heavily infested with Psoroptes ovis (Hering), were each given a single subcutaneous injection of 200 micrograms of ivermectin/kg. Another 10 heavily infested heifers (stanchioned) were injected subcutaneously with the solvent system (vehicle) used to formulate the ivermectin. Treatment with the vehicle did not reduce mite populations or total egg counts. The 10 heifers treated with ivermectin had an immediate reduction in live mite and egg counts (an increase in the percentage of mortality of mites) and were completely free of psoroptic mites by 20 days after treatment. Ivermectin was equally effective against adult and immature psoroptic mites.

Animals↗

PubMed1992

Subclinical psoroptic otocariasis in Brazilian sheep with comments on a technique for mite collection.

Subclinical psoroptic otocariasis associated with Psoroptes cuniculi (Delafond) was diagnosed in four out of ten herds of sheep. Transmission of mites between sheep and goats and vice versa was detected in herds kept on the same pastures for over 2 years. Flushing the ear canals of sheep and goats with approximately 50 ml of water appeared to be more efficient than swabbing or otoscopic examination for diagnosis and/or mite collection.

Animals↗

PubMed1982

The infectivity of surviving Psoroptes ovis (Hering) on cattle treated with ivermectin.

Ivermectin, 22,23-dihydroavermectin B1 (Merck MK-933), injected intramuscularly at the rate of 200 microgram kg-1 body wt., completely eliminated Psoroptes ovis populations from 6 Hereford cattle within 2 weeks after treatment. However, mites surviving 1, 3, and 5 days after treatment were viable and infective when transferred to untreated cattle. Mites surviving 7 days after treatment did not cause scabies or establish a colony of mites when transferred to untreated cattle. These results indicate that cattle treated with ivermectin for control of psoroptic scabies should be isolated from other cattle for at least 5 days after treatment.

Animals↗