Inhibitor Report for: Fenitrothion

We reviewed 130 admissions of organophosphate poisoning and analyzed the causes of death. Fenitrothion, malathion, dichlorvos, trichlorfon and fenitrothion/malathion were the most frequent chemicals involved. Mortality was 25% (32/130); delay in discovery and transport (18 cases), insufficient respiratory management (8 cases), and severe underlying or co-existing diseases (6 cases) were noted in the lethalities. Insufficient respiratory management consisted of delay in endotracheal intubation (5 cases) and failure in weaning (3 cases). About 3/4 of the severely serum cholinesterase-depressed cases needed ventilators. This suggests that better respiratory management would improve the outcome of organophosphate poisonings. Close observation of the clinical symptoms is essential, and detection of changes in serum cholinesterase may be helpful.

Resistance to fenitrothion was investigated in housefly populations in Danish farms 1964--72 in connection with trials of fenitrothion, dimethoate and other organophosphorus compounds for fly control. Resistance was tested by topical application and expressed as resistance ratios, R/S, relative to normal susceptible strains. In 1964--70 fly populations on farms sprayed with fenitrothion (one year each) only developed mode-rate fenitrothion-resistance, R/S at LD 95 below 21 and fly control was generally satisfactory. However, in 1972 high fenitrothion-resistance, R/S 100--400 at LD 95, was found in several fly populations, both on farms treated with fenitrothion and on farms treated with dimethoate, fenitrothion, or bromophos. In all cases the high fenitrothion-resistance was associated with high resistance to dimethoate. Some characteristics of this, apparently complex, resistance are discussed including the effect of certain synergists. Resistance to fenitrothion in Danish flies is only partly reduced by pretreatment with high dosages of sesamex, which inhibits microsomal detoxication, and very little by TBTP (S, S, S tributyl phosphorotrithioate), which inhibits other types of break-down of organophosphorus compounds, e.g. by ali-esterases. The occurrence of fenitrothion- resistance in field populations of houseflied in other regions is briefly reviewed. Widespread, partly very high, resistance has recently been reported from Japan.

The development of chemical control of Musca domestica on Danish farms 1945--72 is outlined. It has been strongly influenced by successive development of resistance and failure of control by one insecticide after another. The chlorinated hydrocarbons used as residual sprays failed 1947--51. Organophosphorus compounds (OPC) were widely used from 1953, first as strips impregnated with parathion and residual sprays with diazinon. Resistance to OPC was first found in 1955, diazinon was given up in 1957--59 and parathion strips failed in the early '60's. Trichlorfon paint-on baits were widelyused 1958--64 and serious resistance did not appear until 1967, induced by selective pressure of fenthion and dimethoate used as residual sprays. High resistance to the contact effect of trichlorfon now occurs everywhere in Denmark. However, trichlorfon baits are still able to kill many flies. Residual sprays with fenthion, ronnel and fenitrothion were used to some extent 1960--70, but increased resistance reducing the residual effect developed in 2--3 years. Dimethoate was used on the majority of farms 1965--72. It was very effective the first years and resistance increased slowly until 1971--72, when high to extreme dimethoate-resistance became general on Danish farms. This was associated with high resistance to other OPC for fly control, e.g. fenthion, fenitrothion, bromophos, and tetrachlorvinphos, and to carbamates, with the result that no generally effective residual sprays were available. In 1971--72 frequent treatments with synergized pyrethroids have been tried. However, the method is often expensive, and serious resistance problems have appeared on a few farms. In this situation preventive, sanitary measures to eliminate or reduce fly breeding in manure are becoming decisive again, but difficult to practise due to lack of farm labour. The extreme Danish situation is compared with those in other areas, and probable reasons for differences in resistance and control problems are discussed, as well as possibilities for strategies to reduce resistance development.

To establish an insecticidal resistance surveillance program, Culex quinquefasciatus mosquitoes from So Paulo, Brazil, were colonized (PIN95 strain) and analyzed for levels of resistance. The PIN95 strain showed low levels of resistance to organophosphates [malathion (3.3-fold), fenitrothion (11.2-fold)] and a carbamate [propoxur (3.0-fold)]. We also observed an increase of 7.4 and 9.9 in alpha and beta esterase activities, respectively, when compared with the reference IAL strain. An alteration in the sensitivity of acetylcholinesterase to insecticide inhibition was also found in the PIN95 mosquitoes. The resistant allele (Ace.1R), however, was found at low frequencies (0.12) and does not play an important role in the described insecticide resistance. One year later, Cx. quinquefasciatus mosquitoes were collected (PIN96 strain) at the same site and compared to the PIN95 strain. The esterase activity patterns observed for the PIN96 strain were similar to those of the PIN95 mosquitoes. However the occurrence of the Ace.1R allele was statistically higher in the PIN96 strain. The results show that esterase-based insecticide resistance was established in the PIN95 Cx. quinquefasciatus population and that an acethylcholinesterase based resistant mechanism has been selected for. A continuous monitoring of this phenomenon is fundamental for rational mosquito control and insecticide application programs.

The purpose of this work was to integrate existing chemical residue and food consumption data for individuals to improve estimates of the dietary intake of chemical residues in the population of Brisbane. Previous estimates of intakes from the Australian Market Basket Survey (AMBS) have been based on energy-adjusted 'hypothetical national diets' and so allow no assessment of variation in intakes between individuals or groups. Data on concentration of fenitrothion, chlorpyrifos-methyl, pirimiphos-methyl, heptachlor and dieldrin in selected foods were taken from reports of the AMBS. Food consumption data were based upon the National Dietary Survey of Adults (NDSA) 1983; the same data from which the hypothetical diets are derived. The distribution of estimated 24-hour intakes was adjusted to represent usual intakes. Mean intakes of all residues were about one third those reported previously. None of the observed diets contained levels of residues that were greater than the Acceptable Daily Intakes. These findings support reassurances to the public that residues of agricultural chemicals monitored in the AMBS do not pose a health risk.

A field population of Lutzomyia longipalpis from La Rinconada, Lara State, an endemic focus of visceral leishmaniasis in Venezuela, was tested for susceptibility to organochlorine (DDT 2%), carbamate (propoxur 0.01%), organophosphate (malathion 2%, fenitrothion 1%, and pirimiphos methyl 1%), and pyrethroid (deltamethrin 0.06%, lambdacyhalothrin 0.06%, and permethrin 0.2%) insecticides. Susceptibility to the insecticides tested was evaluated in the field population of L. longipalpis and compared with a laboratory reference strain. The (LT95) to propoxur and malathion insecticides for the field population was lower than the LT95 for the laboratory reference strain, demonstrating high susceptibility to these compounds. A low level of resistance at LT50 (< 3-fold) was found for fenitrothion, pirimiphos methyl, and permethrin insecticides, but no resistance was detected at LT95. No significant resistance at the LT50 and LT95 was detected for the pyrethroids deltamethrin and lambdacyhalothrin. The susceptibility levels of L. longipalpis to the insecticides tested are discussed in view of a future control program against endophilic vectors of leishmaniases based on the use of pesticides.

European eels (Anguilla anguilla) were exposed to sublethal fenitrothion concentrations (0.02 and 0.04 mg/liter) in a continuous flow-through system for 4 days. Gill Mg2+- and Na+,K+-ATPase activities were evaluated after 2, 8, 12, 24, 32, 48, 56, 72, and 96 h of pesticide exposure. Results indicated that ATPase activity in gill tissue decreased as concentration of fenitrothion increased. Pesticide induced significant inhibitory effects on the Na+, K+-ATPase activity of A. anguilla, ranging from >56% inhibition at a sublethal concentration of 0.02 ppm to >73% inhibition at a sublethal concentration of 0.04 ppm. Eels were exposed to both fenitrothion concentrations for 96 h and then allowed a period of recovery in pesticide-free water. Samples were removed at 8, 12, 24, 48, 72, 96, 144, and 192 h and eel gill ATPase activity was evaluated. Following 1 week of recovery, the Na+,K+-ATPase activity for those animals previously exposed to 0.04 ppm fenitrothion was still different from that of the controls.

European eel (Anguilla anguilla) were exposed to sublethal fenitrothion concentrations in a continuous flow-through system for 4 days. Brain acetylcholinesterase (AChE) activity was evaluated after 2, 8, 12, 24, 32, 48, 56, 72, and 96 h pesticide exposure. Results indicated that AChE activity in eel brains decreased as the concentration of fenitrothion increased. The pesticide induced significant inhibitory effects on the AchE activity of A. anguilla, ranging from > 40% inhibition at a sublethal concentration of 0.02 ppm to > 60% inhibition at a sublethal concentration of 0.04 ppm. Eel were exposed to both fenitrothion concentrations for 96 h and then allowed a period of recovery in pesticide-free water. Samples were removed at 8, 12, 24, 48, 72, 96, 144, and 192 h and eel brain AChE activity was evaluated. Following 1 week of recovery, the AChE activity of those animals previously exposed to 0.02 and 0.04 ppm fenitrothion was still different from that of the controls. So, the AChE activity of eel brains at the end of the recovery phase remained significantly depressed.

Approximately 200 citrus samples from markets of the Valencian Community (Spain) were analyzed to establish their residue levels in 12 organophosphorus pesticide residues during the 1994-1995 campaign. The organophosphorus pesticides carbophenothion, chlorpyriphos, chlorfenvinphos, diazinon, ethion, fenitrothion, malathion, methidation, methylparathion, phosmet, quinalphos, and tetradifon were simultaneously extracted by matrix solid-phase dispersion and determined by gas chromatography-mass spectrometry using selected ion monitoring mode. A total of 32.25% contained pesticide residues and 6.9% exceeded the European Union Maximum Residue Levels (MRLs). The pesticides found in the samples with residues above MRLs were carbophenothion, ethion, methidathion, and methyl parathion. Lower level residues of these and the other pesticides studied (except diazinon) were frequently found. The estimated daily intake of the 12 organophosphorus pesticide residues during the studied period was 4.87 x 10(-4) mg/kg body weight/day. This value is lower than the provisional tolerances dairy intakes proposed by the Food and Agriculture Organization and the World Health Organization.

We reviewed 130 admissions of organophosphate poisoning and analyzed the causes of death. Fenitrothion, malathion, dichlorvos, trichlorfon and fenitrothion/malathion were the most frequent chemicals involved. Mortality was 25% (32/130); delay in discovery and transport (18 cases), insufficient respiratory management (8 cases), and severe underlying or co-existing diseases (6 cases) were noted in the lethalities. Insufficient respiratory management consisted of delay in endotracheal intubation (5 cases) and failure in weaning (3 cases). About 3/4 of the severely serum cholinesterase-depressed cases needed ventilators. This suggests that better respiratory management would improve the outcome of organophosphate poisonings. Close observation of the clinical symptoms is essential, and detection of changes in serum cholinesterase may be helpful.

A rapid procedure has been developed that allows a single-step, selective extraction and cleanup of organophosphate (OP) pesticide residues from milk dispersed on solid-matrix diatomaceous material filled into disposable cartridges by means of light petroleum saturated with acetonitrile and ethanol. Recovery experiments were carried out on homogenized commercial milk (3.6% fat content) spiked with ethanolic solutions of 24 OP pesticides, viz., ethoprophos, diazinon, dimethoate, chlorpyrifos-methyl, parathion-methyl, chlorpyrifos-ethyl, malathion, isofenphos, quinalphos, ethion, pyrazophos, azinphosethyl, heptenophos, omethoate, fonofos, pirimiphos-methyl, fenitrothion, parathion, chlorfenvinphos, phenthoate, methidathion, triazophos, phosalone, azinphos-methyl, at levels ranging for the different OP pesticides from 0.02 mg/kg to 1.11 mg/kg. Average recoveries of four replicates were in the range 72-109% for the different OP pesticides, with relative standard deviations (R.S.D.) from ca. 1 to 19%, while dimethoate and omethoate were not recovered. Coextracted fatty material amounted to an average of about 4.0 mg/ml of milk. The extraction procedure requires about 30 min. The main advantages are that extraction and cleanup are carried out in a single step, emulsions do not occur, several samples can be run in parallel by a single operator, reusable glassware is not needed and simple operations are required.

A multiresidue extraction method based on matrix solid-phase dispersion (MSPD) is optimized for the extraction and gas chromatographic screening of eighteen insecticides (aldrin, carbophenothion, captafol, chlorpyriphos, chlorfenvinphos, diazinon, dicofol, alpha-endosulfan, beta-endosulfan, ethion, fenitrothion, folpet, methidathion, malathion, methyl-azinphos, methyl-parathion, phosmet, and tetradifon) from oranges. After optimization of different parameters, such as type of solid phase used and the amount of solid phase or eluent, recoveries ranged from 67 to 102% with relative standard deviations ranging from 2 to 10%. The limits of detection, calculated as 3 times the baseline noise ranged from 2 to 171 micrograms/kg. These limits of detection were about 10 times lower than the maximum residue levels established by the European Community. Compared with classical methods, the described procedure is simple, less labour intensive and does not require preparation and maintenance of equipment. Troublesome emulsions, such as those frequently observed in liquid-liquid partitioning did not occur.

During the experimental use of fenitrothion to replace malathion for the control of malaria in North West Frontier Province of Pakistan, serious intoxication of Afghan refugee spraymen occurred. A few weeks after commencement of the spraying operations, cholinesterase levels had fallen to 43.8% in personnel mixing the insecticide, and to 60.7% in spraymen, as measured by tintometry. Most of the personnel reported symptoms of overexposure and the spraying operations had to be discontinued. Intoxication of personnel resulted in poor coverage of the target area. High ambient temperatures during Pakistan's spray season discourage the use of full-protective clothing. Fenitrothion intoxication observed in the Afghan refugee programme, and similar experiences in Pakistan in the past, suggest that this insecticide is too toxic for routine use, when the compliance with safety precautions cannot be effectively supervised.

Fenitrothion has been reported as one of the organophosphates causing so called "intermediate syndrome"--clinical entity of still unclear reasons. That is why we decided to perform a retrospective examination of oral intoxication with this compound. Clinical course of 16 cases were analysed. Clinical state on admission, AChE activity and pesticide concentration in blood were considered. Gastric lavage, atropine and oximes were included in the treatment. 6 patients died in the period of 5 to 22 days (mean 11.8) from poison intake. All 6 revealed slight signs of poisoning at the time of admission (first 24th). AChE was moderately inhibited. Patients' clinical state was deteriorating and AChE activity was decreasing during next 48 h even though oximes therapy was applied. Intubation and mechanical ventilation was required. Fenitrothion concentration in blood varied from 470 to 8350 ng/ml (mean 2823 ng/ml). In 3 fatal cases toxicological examination of autopsy tissue was done. High fenitrothion concentration was found in adipose tissue and also in the brain. In the group of 10 recovered patients "intermediate syndrome" was not observed in 3 only. AChE activity returned to normal quickly. Fenitrothion concentration ranged from 96 to 360 ng/ml (mean 202 ng/ml). In the remaining 7 clinical state became worse during next 48-72 hours after temporary improvement. Respiratory failure and increasing AChE activity inhibition were major signs. Fenitrothion concentration varied from 180 to 3020 ng/ml (mean 1690 ng/ml). AChE inhibition persisted even for 30 days from poisoning.

Susceptibility to six organophosphate (OP), two pyrethroid (PY), and one carbamate (C) insecticides was investigated in Culex pipiens quinquefasciatus Say, Aedes aegypti (L.), and Aedes polynesiensis Marks larvae from the island of Tahiti. Cx. p. quinquefasciatus and Ae. aegypti were compared with susceptible reference strains treated simultaneously. A low, but significant, resistance to bromophos (4.6x), chlorpyrifos (5.7x), fenthion (2.4x), fenitrothion (5.0x), temephos (4.3x) and permethrin (2.1x) was found in Cx. p. quinquefasciatus, and to malathion (1.5x), temephos (2.3x), permethrin (1.8x) and propoxur (1.7x) in Ae. aegypti. Cx. p. quinquefasciatus was shown to possess over-produced esterases A2 and B2, which are known to be involved in resistance to OPs in other countries. Ae. polynesiensis was less resistant than the Ae. aegypti reference strain to all insecticides except temephos (1.8x) and permethrin (6.7x). To determine whether Ae. polynesiensis had developed resistance to these insecticides in Tahiti, a geographical survey covering 12 islands of the Society, Tuamotu, Tubuai, Marquesas, and Gambier archipelagoes was undertaken with three insecticides (temephos, deltamethrin, and permethrin). Two- to threefold variations in LC50S were observed among collections. Results are discussed in relationship to the level of insecticide exposure on the different islands.

Susceptibility status of five populations of Ae. albopictus mosquitoes from Maharashtra state, to DDT, malathion, fenitrothion, bromophos, propoxur and deltamethrin was studied and compared with the laboratory population. Four populations survived when adults were exposed to 4 per cent DDT impregnated paper for 2 h; though three of these populations had lower DDT-LC50 values at larval stages in comparison with the laboratory population. Results of topical application of DDT on these four populations supported these findings by showing comparatively higher LD50 values at adult stages in comparison with the laboratory population. All the populations were highly susceptible to other pesticides tested i.e., malathion, fenitrothion, bromophos, propoxur and deltamethrin. These populations were distinguished from each other by esterase isoenzyme patterns.

The O-dealkylation of pentoxyresorufin, a substrate for P450 2B1, was decreased in lung microsomes from rats dosed with O,O,S-trimethylphosphorodithioate, O,O,O-trimethylphosphorothioate, bromophos, fenitrothion, p-xylene and 2,4-dichloro-(6-phenylphonoxy)ethylamine. This activity was decreased by antibodies to P450 2B1 but unaffected by antibodies to P450 1A1 or 4B1. This reduction reflected both inactivation and destruction of P450 2B1; destruction of this protein was particularly marked after bromophos and fenitrothion. Pyrazole was the only compound in this study to induce the O-dealkylation of pentoxyresorufin. None of these compounds altered the rate of ethoxyresorufin O-dealkylation, an indicator of P450 1A1 activity, but this activity was induced greatly by both Aroclor and beta-naphthoflavone, p-Xylene was the only compound to decrease P450 4B1 activity, as determined by the N-hydroxylation of 2-aminofluorene. In the liver, bromophos, fenitrothion, p-xylene and 2,4-dichloro-(6-phenylphonoxy)ethylamine all had marked effects on the O-dealkylation of ethoxyresorufin and pentoxyresorufin but, at the dose used, O,O,O-trimethylphosphorothioate and O,O,S-trimethylphosphorodithioate had minimal effects in this tissue. Thus, both O,O,O-trimethylphosphorothioate and O,O,S-trimethylphosphorodithioate are exquisitely selective inhibitors of pulmonary P450 2B1 activity. Their use, together with pyrazole, will facilitate future studies of the pulmonary activation of toxins by P450 2B1.

Various organophosphorus compounds with low acute toxicity levels are widely used as insecticides. Human acute poisoning by organophosphates has often occurred accidentally. We determined the activity and isoenzyme patterns of serum cholinesterase (ChE) obtained from 13 human patients who attempted suicide with various organophosphates, i.e. Fenitrothion, Malathion, Isoxathion, Pyridaphenthion and Trichlorfon, and studied on the changes in the activity and isoenzyme patterns of serum ChE after ingestion. The following results were obtained. 1) Twenty ChE isoenzyme bands from normal human serum were detected by electrophoretic separation on polyacrylamide gradient gel. The main bands in the ChE isoenzyme pattern in normal serum were bands 4 and 5 which had the highest activity of acetylcholinesterase (AChE) with a molecular weight of 600,000-800,000, and bands 7, 12, 14, 17 and 18. 2) Inhibition of serum ChE activity was more severe as the amount ingested increased in patients who took Fenitrothion and Malathion. Reactivation of serum ChE activity was very slow in patients treated with PAM (2-pyridine aldoxime methiodide) in the late stage of ingestion or whose symptoms reappeared. 3) There were no differences in the patterns of serum ChE isoenzyme by organophosphorus compound. Band 7 disappeared in the serum ChE isoenzyme of almost every patient, and bands 12, 18, 14 and 17 of the serum ChE isoenzyme disappeared successively with the decline of serum ChE activity. Only band 5 of the isoenzyme remained in cases who had serum ChE activity lower than 5% of normal. 4) All 13 patients were treated with PAM and atropine immediately after being admitted to hospitals. We could not clearly determine the efficacy of PAM on reactivation of serum ChE activity and isoenzyme, because it was impossible in human poisoning to compare PAM efficacy with no treatment and with pre- and post-PAM treatment. 5) The activity and isoenzyme patterns of serum ChE recovered rapidly after combined hemoperfusion and hemodialysis treatment (HP-HD treatment) of the patients poisoned with Malathion. But HP-HD treatment had no effect on poisoning by Fenitrothion and Isoxathion. These findings demonstrated the changes in the activity and isoenzyme pattern of serum ChE in patients poisoned with several organophosphates after PAM and HP-HD treatment.

A flow injection system, incorporating an acetylcholinesterase (AChE) single bead string reactor (SBSR), for the determination of some organophosphorous (azinphos-ethyl, azinphos-methyl, bromophos-methyl, dichlorovos, fenitrothion, malathion, paraoxon, parathion-ethyl and parathion-methyl) and carbamate insecticides (carbofuran and carbaryl) is presented. The detector is a simple pH electrode with a wall-jet entry. Variations in enzyme activity due to inhibition are measured from pH changes when the substrate (acetylcholine) is injected before and after the passage of the solution containing the insecticide. The percentage inhibition of enzyme activity is correlated to the insecticide concentration. Several parameters influencing the performance of the system are studied and discussed. The detection limits of the insecticides ranged from 0.5 to 275 ppb. The determination of these compounds was conducted in Hepes buffer and a synthetic sea water preparation. The enzyme reactor can be regenerated after inhibition with a dilute solution of 2-PAM and be reused for analysis. The immobilized enzyme did not lose any activity up to 12 weeks when stored at 4 degrees C.

Responses of Paramecium caudatum, a ciliated protozoan, to acute exposures of certain organic solvents and organophosphorus insecticides (OPI) were studied by determining their lethal concentration (10 min-LC100) and median lethal concentration (4 h-LC50). The solvents and OPI evoked a distinct sequence of responses. Among the five solvents tested, acetone proved most toxic [LC-2.9% and LC50-0.68% (v/v)], while dimethyl sulphoxide (DMSO) showed least toxicity [LC-11.0% and LC50-3.16% (v/v)]. The order of toxicity of solvents was: acetone greater than ethanol greater than methanol greater than N, N-dimethylformamide greater than dimethylsulphoxide. The LC values of six OPI dissolved in either acetone or DMSO indicated that they were more toxic when dissolved in acetone and least toxic in DMSO. Among the OPI, bromophos proved most toxic (LC-10 ppm) while malathion showed least toxicity (LC-200 ppm) in DMSO. The order of toxicity of OPI was: bromophos greater than pirimiphos-methyl greater than parathion methyl greater than dichlorvos greater than fenitrothion greater than malathion. The 4 h-LC50 values computed for bromophos and malathion (dissolved in DMSO) were 575 ppb and 19.9 ppm, respectively, indicating the high susceptibility of P. caudatum to bromophos. The results indicate that the Paramecium toxicity assay could be used as a complementary system to rapidly elucidate the cytotoxic potential of compounds.

Studied was the effect of the preparations phenitrothion (Agria-1050) and phosalon (Agria-1060) on the immunologic reactivity of sheep through following up the phenomena of agglutination and phagocytosis at the injection of a Salm. gallinarum antigen. An unknown property of these preparations was established, consisting in the stimulation of some defense immunobiologic processes in the body of animals, at their application in minimum doses per os, simultaneously with the injection of a bacterial antigen. Phenitrothion applied orally to sheep at the rate of 50 mg per kg body mass daily, seven times in the course of sixty days, with the injection of a suspension of a killed Salmonella gallinarum culture (containing 10(7) microbial cells per 1 cm3-3 cm3 i/v, and 5 cm3 four days later, s/c per animal) stimulated agglutinin production, increasing it from 9 to 17 times; it raised the phagocytic number by 2.5 to 3 times, and the phagocytic index--by 1.7 to 2.14 times. With control animals the increase was 3-4, 1.4-1.5, and 1.10-1.19 times, respectively. Phosalon applied to sheep in following the same pattern at the rate of 13 mg per kg body mass led to a rise of the agglutinintiter from 22 to 26 times; the phagocytic number was raised by 2.6 to 4.3 times, and the phagocytic index--by 1.6-2.3 times.

Details of cases involving the inadvertent exposure of birds to eight toxic substances are recorded. The organophosphate insecticides dichlorvos, diazinon and malathion produced respiratory symptoms which in the former and latter cases were initially thought to be caused by infectious disease. Birds which consumed feed containing fenitrothion showed nervous signs before death. On three separate occasions feral starlings (Sternus vulgaris) were found dead and their gizzard contents contained mevinphos. The rodenticide warfarin was associated with petechial haemorrhages in the skeletal muscles and on the serosal surfaces of one hen. Cyanogenic glycosides from Eucalyptus cladocalyx were responsible for the sudden deaths of ducks and guinea fowl. 'Ornamental dough' containing sodium chloride was fed to birds which were deprived of water and they showed diarrhoea and nervous disorders before death.

Common house mosquito Culex pipiens molestus Forskal was used to test biologically the residual toxicity of 15 organophosphorus, 5 carbamate and 5 pyrethroid insecticide preparations sprayed on whitewashed or limewashed wall surfaces. The doses of 0.1 g and 1.0 g of active ingredient per 1 m2 of wall surface were used in this experiment. At the dose of 1 g/m2, organophosphates chlorpyriphos, diazinon, fenitrothion, malathion, pirimiphos-methyl and propetamphos, cambamates bendiocarb, dioxacarb, propoxur and promecarb, and pyrothroids bioresmethrin, decamethrin-permethrin and tetramethrin produced on whitewashed wall surfaces the residual toxicity persisting for at least four months. At the dose of 0.1 g/m2, a long-lasting residual toxicity persisting on whitewashed wall surfaces for at least two months was observed after bendiocarb, decamethrin, fenitrothion, permethrin, pirimiphos-methyl and propoxur application. The residual toxicity of organophosphates, carbamates except for bendiocarb and pyrethroids except for permethrin sprayed on limewashed wall surfaces was considerably shorter than on whitewashed surface.

A series of in vitro trials using unfed larvae and fully fed adult ticks confirmed ixodicidal resistance in the one-host Pantropical Blue Tick, Boophilus microplus (Canestrini). Fifty-seven of 64 field isolates were resistant to arsenic; 10 of 56 were resistant to toxaphene; 1 of 5 were resistant to lindane; 3 of 5 were resistant to dieldrin; 3 of 19 were resistant to DDT and 8 of 55 were resistant to the organophosphorus ixodicide, dioxathion. One of the field isolates resistant to dioxathion was also highly resistant to the carbamate, carbaryl, and to the organophosphorus ixodicides benoxophos and diazinon. A second was resistant to the organophosphorus ixodicides benoxophos, diazinon, carbophenothion, dicrotophos, ethion, fenitrothion and quintiofos. Low levels of resistance, less than 3X, were shown to chlorfenvinphos and coumaphos. No resistance was shown to chlorpyrifos, bromophos ethyl or the diamidine ixodicide, amitraz. In hand-spraying trials no variation in the susceptibility of an organophosphorus resistant strain or the susceptible laboratory strain to amitraz was observed. This is the first recorded resistance to ixodicides by B. microplus in Africa.

A screening method has been developed for determining organophosphorus pesticides at ng/L levels in drinking water. Sixteen organophosphorus pesticides, diazinon, diazinon-oxon, dimethoate, ronnel, beta-phosphamidon, methyl parathion, ethyl parathion, malathion, chlorpyrifos, fenitrothion, ruelene, methidathion, ethion, EPN, phosalone, and phosmet, were extracted by Amberlite XAD-2 resin from 100 and 200 L drinking water previously spiked with these pesticides. The pesticides were eluted from the XAD-2 resin with acetone-hexane (15+85). The concentrated extract was analyzed by gas chromatography using a nitrogen-phosphorus selective detector and by gas chromatography-mass spectrometry using selected ion monitoring. Recoveries at the 10 and 100 ng/L spiking levels were greater than 90%, except recoveries for dimethoate and phosphamidon were 37 and 42%, respectively. The analysis of 300 L Ottawa tap water showed no detectable amounts (less than 1 ng/L) of any of the 16 organophosphorus pesticides.

Resistance to fenitrothion was investigated in housefly populations in Danish farms 1964--72 in connection with trials of fenitrothion, dimethoate and other organophosphorus compounds for fly control. Resistance was tested by topical application and expressed as resistance ratios, R/S, relative to normal susceptible strains. In 1964--70 fly populations on farms sprayed with fenitrothion (one year each) only developed mode-rate fenitrothion-resistance, R/S at LD 95 below 21 and fly control was generally satisfactory. However, in 1972 high fenitrothion-resistance, R/S 100--400 at LD 95, was found in several fly populations, both on farms treated with fenitrothion and on farms treated with dimethoate, fenitrothion, or bromophos. In all cases the high fenitrothion-resistance was associated with high resistance to dimethoate. Some characteristics of this, apparently complex, resistance are discussed including the effect of certain synergists. Resistance to fenitrothion in Danish flies is only partly reduced by pretreatment with high dosages of sesamex, which inhibits microsomal detoxication, and very little by TBTP (S, S, S tributyl phosphorotrithioate), which inhibits other types of break-down of organophosphorus compounds, e.g. by ali-esterases. The occurrence of fenitrothion- resistance in field populations of houseflied in other regions is briefly reviewed. Widespread, partly very high, resistance has recently been reported from Japan.

The development of chemical control of Musca domestica on Danish farms 1945--72 is outlined. It has been strongly influenced by successive development of resistance and failure of control by one insecticide after another. The chlorinated hydrocarbons used as residual sprays failed 1947--51. Organophosphorus compounds (OPC) were widely used from 1953, first as strips impregnated with parathion and residual sprays with diazinon. Resistance to OPC was first found in 1955, diazinon was given up in 1957--59 and parathion strips failed in the early '60's. Trichlorfon paint-on baits were widelyused 1958--64 and serious resistance did not appear until 1967, induced by selective pressure of fenthion and dimethoate used as residual sprays. High resistance to the contact effect of trichlorfon now occurs everywhere in Denmark. However, trichlorfon baits are still able to kill many flies. Residual sprays with fenthion, ronnel and fenitrothion were used to some extent 1960--70, but increased resistance reducing the residual effect developed in 2--3 years. Dimethoate was used on the majority of farms 1965--72. It was very effective the first years and resistance increased slowly until 1971--72, when high to extreme dimethoate-resistance became general on Danish farms. This was associated with high resistance to other OPC for fly control, e.g. fenthion, fenitrothion, bromophos, and tetrachlorvinphos, and to carbamates, with the result that no generally effective residual sprays were available. In 1971--72 frequent treatments with synergized pyrethroids have been tried. However, the method is often expensive, and serious resistance problems have appeared on a few farms. In this situation preventive, sanitary measures to eliminate or reduce fly breeding in manure are becoming decisive again, but difficult to practise due to lack of farm labour. The extreme Danish situation is compared with those in other areas, and probable reasons for differences in resistance and control problems are discussed, as well as possibilities for strategies to reduce resistance development.