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Biomedical subjects

F S Guillot

Publications and source records attributed to F S Guillot.

At least 19 recordsLinked to original sources
PubMed1992

Moxidectin: systemic activity against common cattle grubs (Hypoderma lineatum) (Diptera: Oestridae) and trichostrongyle nematodes in cattle.

Moxidectin, a systemic insecticide, was evaluated for its efficacy against the migrating first instars of the common cattle grub, Hypoderma lineatum, and against nematode egg production in beef cattle. It was observed that all three levels (0.1, 0.2 and 0.4 mg moxidectin kg-1) were 100% effective against cattle grubs when administered as a s.c. injection. The same levels of treatment were very effective (90-100%) in reducing trichostrongyle nematode egg production. However, there was a slight indication that at least one species, Cooperia oncophora, was not completely eliminated, as it was observed that small numbers of eggs began to appear after 2 weeks post-treatment when there had been no opportunity for reinfection.

Animals↗
PubMed1989

Pathogenesis of psoroptic scabies in Hereford heifer calves.

Hereford heifer calves were experimentally infested with Psoroptes ovis. Histologic examination of skin specimens was conducted at weekly intervals before and after treatment with ivermectin on postinfestation week 7. Electron microscopy revealed numerous degranulating mast cells in the skin of infested but not in control calves. many active, as well as degenerate, neutrophils were in the scab on infested calves. Microscopic epidermal ulcers developed on infested calves when live mites were present but not after treatment. Numbers of dermal neutrophils and plasma cells decreased and numbers of circulating neutrophils increased 1 week after treatment. Numbers of dermal eosinophils and mast cells in calves with eosinophilia increased for several weeks after treatment. Statistical analysis indicated significant correlations (P less than 0.05) among numbers of dermal inflammatory cells, hemogram values, and changes in dermal thickness. Seemingly, mite-induced epidermal damage was the key pathogenic event in psoroptic scabies in calves. Mast cell degranulation contributed to the pathogenesis of the dermatitis, and neutropenia was caused by sustained, poorly compensated efflux of neutrophils into the scab through mite-induced breaks in the epidermis.

Animals↗
PubMed1988

Efficacy of acaricides against chorioptic mange of goats.

Angora goats heavily infested with Chorioptes bovis were dipped one time in either 0.05% amitraz, 0.27% coumaphos, 0.05% fenvalerate, or 0.03% lindane. Control of the mites by the single dips was evaluated for 21 days. Amitraz caused 98% mortality of the mites initially. Both coumaphos and lindane caused greater than 85% mortality at 3 days, but mite numbers increased rapidly thereafter. Only fenvalerate killed all of the mites.

Animals↗
PubMed1987

Influence of Psoroptes ovis on the energy metabolism of heifer calves.

To determine the effect of Psoroptes ovis on the energy metabolism of heifers, 32 calves were randomly assigned to four treatments in a 2 X 2 factorial arrangement. Calves were fed the same diet at two intake levels, high or low, and were either infested or were not infested with P. ovis mites. Calves were housed in antigrooming stanchions. Body composition was determined by urea dilution on Days 0 and 63. Ration digestibility was determined on fecal grab samples using acid-insoluble ash as a marker. Infested calves had developed a severe P. ovis infestation 7 weeks following exposure and had significantly lower daily gain, gain:feed, and energy retention and higher serum glutamic-oxaloacetic transaminase than control calves. P. ovis infestation increased the maintenance energy requirement of calves by greater than 50% (79 vs. 123 kcal of net energy kg-1 body wt.75). For each 10% increase in the body surface affected by P. ovis, maintenance energy requirement increased 0.5 mcal day-1.

Animal Feed↗
PubMed1987

Bone marrow response in cattle with chronic dermatitis caused by Psoroptes ovis.

Six Hereford heifer calves were infested with Psoroptes ovis and compared to six uninfested control calves. Infested calves developed severe exudative dermatitis which covered 100% of the body surface by 7 weeks after infestation. They developed moderate nonregenerative anemia, decreased numbers of neutrophils and lymphocytes, and increased plasma protein and fibrinogen concentrations. Sternal marrow core biopsies taken 7 weeks after infestation were 75 to 90% cellular, while cores from uninfested calves were 10 to 20% cellular. Comparison of myelograms between the two groups of calves revealed increased M:E ratio, myelocyte and metamyelocyte hyperplasia with depletion of mature neutrophils and eosinophils in the P. ovis-infested calves. It was concluded that P. ovis-infested calves develop myeloid hyperplasia and that mange-related neutropenia is not due to bone marrow suppression by a mite or scab-associated toxin.

Agranulocytosis↗
PubMed1987

Hematology in the regressive phase of bovine psoroptic scabies.

Hereford calves were infested with Psoroptes ovis. Hemograms were evaluated weekly for 7 weeks during progressively extensive dermatitis and compared to uninfested control calves. Calves were treated with ivermectin and weekly hemograms were compared for 4 weeks during regression of clinical disease. They developed extensive dermatitis and marked decreases in total white blood cells, neutrophils, and lymphocytes. Infested calves also had moderate anemia, increased plasma proteins, and increased plasma fibrinogen. Some calves developed marked eosinophilia. Within 1 week after ivermectin treatment, nearly all hematologic parameters returned or began to return to normal values, even though scabs remained on the calves at 4 weeks. Peak eosinophilia in calves which responded occurred 1 to 2 weeks after treatment. The findings indicate that most of the hematologic changes occurring with psoroptic scabies in cattle are associated with living mites and not with toxic substances in the scab on the skin surface.

Animals↗
PubMed1986

Development and decline of serum antibody activity to Psoroptes ovis antigens in infested cattle in an endemic and nonendemic scabies area of Texas.

The serum antibody activity to Psoroptes ovis antigens, as determined by enzyme-linked immunosorbent assay (ELISA), was monitored during the development and decline phase of scabies in cattle herds under feedlot conditions in an endemic (Bushland) and a nonendemic (Kerrville) scabies area of Texas. The infestations were initiated by exposing six calves in each of the herds to P. ovis and allowing the infestations to spread to other members of the herd. The cattle in the endemic area developed more lesions and a higher incidence of the disease than did the cattle in the nonendemic area; also, there were more cattle with specific serum antibody activity in the Bushland herd than in the Kerrville herd at the peak of the infestations (late January--early February). As infestations declined because of summer latency, the number of calves with specific serum antibody activity declined in both herds. Specific serum antibody activity disappeared in the Kerrville cattle when P. ovis was no longer detected. However, specific serum antibody activity was still detected in some of the Bushland cattle in late summer (August) and fall (October) examinations, when low numbers of P. ovis were detected. These results indicate that the ELISA would be very useful in detection of specific serum antibody activity in lightly infested calves, especially during the developmental and decline phases of the disease.

Animals↗
PubMed1986

Humoral and cellular immunoresponsiveness of stanchioned cattle infested with Psoroptes ovis.

Bovine scabies in a clinical problem during the cool autumn and cold winter months. In south Texas it is necessary to stanchion animals in order to elicit patent infestation during summer months. Environmental factors and grooming have been purported to account for summer resistance to infestation. However, stanchioned animals exhibit varied levels of susceptibility to infestation, suggesting that the noted variability may be influenced by the host immune response. In this study, animals were infested with Psoroptes ovis while in stanchions. The development of anti-P. ovis antibody activity was measured by the enzyme-linked immunosorbent assay and cellular immune function was monitored with mitogens and P. ovis antigens. A correlation was noted between the development of anti-P. ovis antibody activity and the increase in mite numbers and dermatitis. Coincident with the developing infestation was a suppression of T-cell function that appeared to be stress-related as a result of stanchioning. A working hypothesis is presented that attempts to correlate the developing humoral response and the depressed T-cell response with both an increasing dermatitis and mite population.

Animal Husbandry↗
PubMed1986

Systemic pathologic responses in experimental Psoroptes ovis infestation of Hereford calves.

Nine Hereford calves were infested with Psoroptes ovis and were allowed to develop clinical mange during a 9-week period. Blood, serum, and urine samples were obtained before and after calves were infested and were compared with those from 3 noninfested control calves. All calves were euthanatized and necropsied 9 weeks after they were infested. Gross and microscopic anatomic changes occurred only in the skin. Calves developed typical exudative dermatitis, the extent of which was dependent on population density of mites. Severely infested calves (50% to 70% of skin with dermatitis) developed a mild anemia and lymphopenia with marked neutropenia and variable eosinophilia. There were also increases in fibrinogen, gamma-globulin, and in vitro lymphocyte response to mitogen stimulation and decreases in anion gap cortisol, albumin, albumin/globulin ratio, and fractional Na clearance values. The severity of many of the changes could be correlated with the extent of dermatitis.

Animals↗
PubMed1986

Concentration of ivermectin in bovine serum and its effect on the fecundity of psoroptic mange mites.

The concentration-time profile of ivermectin in serum was determined for 3 Hereford heifers. The mean maximum serum concentration, 29 ng of ivermectin/ml, was obtained 48 hours after single subcutaneous injection of 200 micrograms/kg of body weight. The fecundity of mites placed on 9 treated animals at 5, 9, 12, 15, 18, and 21 days after injection was reduced by 96% to 99%. At 24 days after treatment, when serum concentration had decreased to about 2 ng/ml, the capability of mites to produce eggs increased to 50% of mites from nontreated calves. At 27 and 30 days after the drug was injected, egg production by mites on treated calves was equivalent to that of mites on nontreated calves. The reduced fecundity resulted from an almost complete cessation of oviposition by females after only a 1-day exposure to ivermectin-treated calves.

Animals↗
PubMed1984

Development and transmission of psoroptic mange of cattle in feed lots in endemic and non-endemic regions.

A test was begun in November 1982 to evaluate the development of Psoroptes ovis, the severity of psoroptic mange of cattle, and the incidence of transfer of P. ovis from artificially infested cattle to non-infested cattle held in feed lots in either an endemic (Bushland, TX) or non-endemic region (Kerrville, TX). The 2 herds each consisted of 24 Hereford steers. The 24 steers were randomly assigned to 3 pens of 8 steers per pen. Two steers from each pen that were randomly selected were artificially exposed to ca. 1000 P. ovis (AINF). The development of mange on these 6 AINF steers and the incidence of transfer to the other steers (INF) were monitored approximately every 3 weeks for 17 weeks. The 6 AINF steers at Bushland (endemic region) developed significantly more lesions than the 6 AINF steers at Kerrville. Three AINF steers in Bushland died from hypothermia and mange while no deaths were recorded at Kerrville. The numbers of mites sampled from affected skin areas of AINF steers from both regions were not significantly different. All 18 of the naturally exposed steers (INF) in Bushland contracted mange; whereas, only 9 INF steers in Kerrville did. The severity (% lesions) and number of mites per sample from affected skin were significantly greater on the INF steers in Bushland. These differences among INF steers in Bushland and Kerrville may be attributed to the higher level of parasitism attained in Bushland on the AINF steers. We propose that the extremely cold weather in Bushland contributed to the greater level of parasitism attained on AINF steers in Bushland by stressing the host steers.

Animals↗
PubMed1984

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↗
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↗
PubMed1983

Cross-mating studies with Psoroptes ovis (hering) and Psoroptes cuniculi delafond (Acarina: psoroptidae).

Reciprocal cross-matings of Psoroptes ovis and P. cuniculi occurred and produced viable offspring through the F2 generation. Hybrids of these crosses were infective to both rabbits and cattle. Mean lengths of the male l4 setae of the parental species differed significantly from each other as well as from those of the hybrid males. These data show that P. ovis and P. cuniculi are not reproductively isolated. Because viable, fertile hybrids are produced, cross-matings of P. ovis and P. cuniculi are not suitable as a suppression method of cattle scabies.

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↗