The detection and distribution of organophosphorus and carbamate insecticide-resistant Myzus persicae (Sulz.) in Britain in 1976

Examination of the enzyme that determines the level of resistance to organophosphorus insecticides and carbamates in Myzus persicae (Sulz.) and bioassays were used to establish the frequency and resistance levels of resistant aphids on outdoor crops in Britain in 1976. The biochemical tests, staining esterase-4 after electrophoresis and total esterase determination, were more sensitive than bioassays. However the dip-test, a simple, rapid and inexpensive bioassay designed to detect resistance and its different levels gave satisfactory results which warrant its use where biochemical detection of resistance is not possible. Carboxylesterase activities of M. persicae collected in 1976 fell into three groups: low, moderate and high, and these were correlated with differences in tolerance to dimethoate, demeton-S-methyl and pirimicarb. Aphids with low esterase activity were susceptible(S). Those with the moderately active enzyme (R₁) had five- to seven-fold resistance to the two organophosphorus insecticides and were marginally resistant (about two-fold) to pirimicarb. The insects with the most active esterase (R₂) were strongly resistant to dimethoate (resistance factor, RF × 126) and moderately resistant to demeton-S-methyl (RF × 17) and pirimicarb (RF × 8). Some R₁, but no S aphids survived the recommended dose of demeton-S-methyl on field crops probably because they were under the lowest leaves and therefore protected from direct contact with the spray. Laboratory tests demonstrated that these R₁ aphids tolerated the residual deposit and systemic dose present in the leaves of the treated potato-plants. This enabled their numbers to recover in treated fields much faster than the susceptible insects which could do so by immigration only when the residual dose in the plant was no longer toxic. R₁ aphids were common throughout the country particularly in eastern England where susceptible aphids were rare, but in the Shardlow area of Derbyshire susceptible aphids were in the majority throughout the summer. R₂ aphids were found only in samples from the west of Scotland and northern England. The implications of the presence of aphids with different levels of resistance for aphid control are discussed.     

Eyeworms (Thelazia lacrymalis) in one- to four-year-old Thoroughbreds at necropsy in Kentucky (1984 to 1985)

From Mar 1, 1984, to Feb 28, 1985, both eyes from 189 one- to four-year-old Thoroughbreds (88 males, 90 females, and 11 geldings) in Kentucky were examined at necropsy for eyeworms. Thelazia lacrymalis was recovered from 45% of 1-year-old horses, 26% of 2-year-old horses, 45% of 3-year-old horses, and 50% of 4-year-old horses; overall, 43% of 1- to 4-year old horses were infected. Prevalence of eyeworms in horses in the present study was comparable with that in horses of similar ages examined at necropsy in Kentucky in 2 previous studies (1975 to 1976 and in 1979), except for the lower percentage of infected 2-year-old Thoroughbreds in the present study.     

The effects of temperature and humidity on the toxicity of three organophosphorus insecticides to adult Oryzaephilus surinamensis (L.)

The toxicities, to a laboratory susceptible strain and to a resistant strain of Oryzaephilus surinamensis (L.), of water-dispersible powder formulations of pirimiphos-methyl, fenitrothion or chlorpyrifos-methyl under constant conditions of 25°C and 70% r. h. were compared to the toxicities when the insects were exposed to a diurnal cycle of 12.5–20–12.5°C and 70–50–70% r. h. to simulate grain store conditions in the UK during spring and autumn. All the insecticides were more effective at 25°C and 70% r. h. The LD₅₀ values for the susceptible strain were low, being 4.4 and 1.4 mg m^?2 at 12.5-20°C and 25°C, respectively, for chlorpyrifos-methyl, 18.3 and 4.1 mg m^?2, respectively, for pirimiphos-methyl, and 4.0 and < 1.O mg m^?2, respectively, for fenitrothion. The LD₅₀ values obtained from the two sets of environmental conditions for a resistant strain (484) differed by factors of 1.8 for chlorpyrifos-methyl, 4.8 for pirimiphos-methyl, and 7.3 for fenitrothion. Toxicity studies were also made with chlorpyrifos-methyl under various constant conditions of temperature and humidity from 5–30°C (5°C intervals) and 30, 50, 70 and 90% r. h., and also at O°C and 60% r. h. Chlorpyrifos-methyl was very effective and there was little or no cross resistance to chlorpyrifos-methyl in the resistant strain. From 15 to 30°C, mortality was high, and differences in mortality at the LD₅₀ level for the various humidities were slight, but there was a decrease in mortality with decreasing humidity at any one temperature, in particular, at 5°C, 50 and 70% r. h., and 10°C and 50% r. h. Chlorpyrifosmethyl was more toxic to both strains at the highest humidity (90%) throughout the whole temperature range. The LD₅₀ values for each strain decreased at each temperature as the water vapour concentration was increased. At O°C and 60% r. h., all the insects from both strains died but the cause of death was not clear.     

Critical tests of morantel-trichlorfon paste formulation against internal parasites of the horse

Critical tests were completed on six horses to evaluate the antiparasitic activity of a paste formulation mixture of morantel citrate and trichlorfon, administered intraorally at the dose rate of 6 mg morantel base kg-1 and trichlorfon at 30 mg kg-1. Aggregate average removals were: 78% for two horses infected with 2nd instar Gasterophilus intestinalis; 100% for one infected with 2nd instar G. nasalis; 96% for six infected with 3rd instar G. intestinalis; 100% for four infected with 3rd instar G. nasalis; 100% for five infected with Parascaris equorum; 100% for one infected with mature Oxyuris equi; 100% for five infected with Strongylus vulgaris; 72% for five infected with S. edentatus; and partial removal (25%) of Anoplocephala perfoliata infection from one infected animal. Pre- and post-treatment EPG and LPG data indicated a reduction of 97% of the mature small strongyle infections. Evidence of toxicosis was not observed in any of the horses.     

Different forms of insensitive acetylcholinesterase in insecticide-resistant house flies (Musca domestica)

A new form of acetylcholinesterase insensitive to organophosphorus inhibitors was identified in house flies collected from animal farms in the U.K. Its degree of insensitivity to a number of inhibitors ranged from 4-fold (omethoate) to >40-fold (tetrachlorvinphos and dichlorvos) compared with our standard susceptible enzyme, and its spectrum of response to inhibitors differed widely from that of a previously studied insensitive form. In addition, the form of acetylcholinesterase reported here is unusual in having a 3.4-fold greater affinity (lower K_m) for acetylthiocholine than the normal enzyme. The possible toxicological significance of this is discussed.     

形态日趋完美的菟葵植物

毛茛科黑儿菠属菟葵(Hcllborus)植物全世界共有20种左右,主要分布在欧洲中部和地中海一带,我国产两种:‘黑儿菠’(H.Chinensis Maxim)和‘中国菟葵’(H.thibetanus)。中国菟葵原名“铁筷子”,是中国西北民间常用的中草药。     

Diagnosis of swine trichinosis by enzyme-linked immunosorbent assay (ELISA) using an excretory- secretory antigen

An excretory-secretory (ES) antigen was used in a serodiagnostic enzyme-linke immunosorbent assay (ELISA) for swine trichinosis. ELISA procedures included a double- antibody test, using either an anti-swine IgG or a protein A enzyme conjugate, and a triple-antibody test using a pig IgG heavy-chain specific second antibody with a conjugated third antibody. The ES antigen was effective in eliminating all false-positive reactivity in sera from farm-raised hogs. The triple-antibody procedure was more sensitive and demonstrated a greater efficiency in detecting positive animals and early seroconversions. Naturally-infected pigs with worm burdens as low as 0.01 larvae per gram (LPG) of diaphragm were seropositive using these procedures. Seroconversion in experimentally-infected animals receiving low doses of muscle larvae (500) occurred considerably later than in animals receiving high doses (10000). This might account for false-negative reactions in naturally-infected animals with very low (less than 0.1 LPG) worm burdens.     

Autologous marrow transplantation as consolidation therapy for canine lymphoma: efficacy and toxicity of various regimens of total body irradiation

Dogs with malignant lymphoma were given chemotherapy consisting of nitrogen mustard, vincristine sulfate, prednisone, L-asparaginase, and 6-mercaptopurine (MOPA-6) for 14 days. Among 62 dogs that completed treatment with MOPA-6, 47 (76%) had complete remission, and 13 (21%) had partial remission and 2 had no response to chemotherapy. Twenty-two of the 62 dogs were not returned by their owners for additional therapy and died 15 to 391 (median 21) days after MOPA-6 from infections or recurrent disease. A median of 1 month after starting MOPA-6 therapy, 40 dogs (35 in complete remission, 5 in partial remission) were given total body irradiation (TBI), followed by infusion of fresh autologous marrow. Twenty dogs were given 13.5 Gray (Gy) of TBI at 4 centi-Gray (cGy)/min. Among 16 evaluable dogs, 7 had recurrence of lymphoma at a median of 169 days. Two dogs died with veno-occlusive disease of the liver, 3 with pneumonia, 3 with hemorrhage, and 1 was killed. Twenty dogs were given 11.8 to 14.7 Gy of TBI at 2 cGy/min. Among 14 evaluable dogs, 9 had recurrence of lymphoma at a median of 117 days. The remaining 5 dogs were killed at 110 to 680 days; lymphoma was not present at necropsy. The results indicated that doses of TBI of 11.8 to 14.7 Gy did not reduce the recurrence of lymphoma, compared with results obtained in a previous study with 8.4 Gy of TBI. Furthermore, increased doses of TBI increased acute and delayed toxicities. Alternatively, recurrent disease may have been due to lymphoma cells contained in the infused remission marrow.