Use of insecticides to control screw-worm fly strike by Chrysomya bezziana in cattle

Some insecticides to control and prevent screw-worm fly strike by Chrysomya bezziana in calves and adult cattle were tested in field trials on cattle in Sabah, East Malaysia. Ivermectin injected subcutaneously in newborn calves at 200 mu/kg provided 10 days protection from screw-worm fly strike, which allowed navels to dry. Ivermectin, 1% dichlofenthion plus gentian violet and 3% lindane plus pine oil smear were all effective in preventing re-strike of treated wounds in adult cattle. A single subcutaneous injection of ivermectin at 200 mu/kg was effective, whereas it was necessary to re-apply the dichlofenthion and lindane smear preparations every 48h.     

The efficacy of some acarieides against screw-worm fly larvae

Thirteen acaricides used for control of cattle tick in Queensland were evaluated for their potential in the chemical control of the screw-worm fly, Chrysomya bezziana. Laboratory evaluations and in vivo tests using artificially infested cattle were made in Papua New Guinea. Most of the acaricides caused some mortality of screw-worm larvae in infested cattle and in laboratory tests. Acaricides of the organophosphorous, carbamate and organophosphorous/synthetic pyrethroid groups showed reasonable activity against screw-worm fly, but the amidines were less effective.     

The efficacy of ivermectin against larvae of the screw-worm fly (Chrysomya bezziana)

An in vitro technique for screening systemic insecticides against larvae of the screw-worm fly, Chrysomya bezziana is described. Susceptibilities of screw-worm larvae of different ages to ivermectin (MK-933) were determined. Based on 24 h larval mortality, the LD50 of 1-,2-,3-,4- and 5-day larvae was 0.01, 0.02, 0.03, 0.2 and 0.4 ppm of ivermectin. LD50 based on adult emergence following treatment of 4- and 5-day larvae was 0.02 and 0.05 ppm. The LD99.9 for 4-day larvae based on 24 h larval mortality and adult emergence was 11.0 and 0.15 ppm respectively and for 5-day larvae, was 44.3 and 0.4 ppm respectively. Pen and field trials with cattle infested with screw-worm fly demonstrated the potential of ivermectin as a systemic insecticide. Dosages of 50, 100 and 200 micrograms/kg, of ivermectin administered subcutaneously to experimentally infested cattle gave complete control for 6, 12 and 14 days respectively. Ivermectin at 200 micrograms/kg caused 100% mortality of screw-worm larvae up to 2 days old at the time of treatment with 70, 64 and 21% mortality of 3-, 4- and 5-day old larvae at the time of treatment. The residual protection from a single dose of 200 micrograms/kg was 16 to 20 days. When bull calves were treated with ivermectin at a dose of 200 micrograms/kg at the time of castration and branding, none of the 77 treated animals sustained a screw-worm strike in the scrotal area compared with 47 strikes (44%) in the 106 control cattle.     

Field assessment of synthetic attractants and traps for the Old World screw-worm fly, Chrysomya bezziana

The performance of newly developed trapping systems for the Old World screw-worm fly, Chrysomya bezziana has been determined in field trials on cattle farms in Malaysia. The efficacy of non-sticky traps and new attractants to trap C. bezziana and non-target flies was compared with the standard sticky trap and Swormlure. The optimal trap was a modified LuciTrap(?) with a new attractant mixture, Bezzilure-2. The LuciTrap/Bezzilure-2 caught on average 3.1 times more C. bezziana than the sticky trap with Swormlure (P<0.05) and provided selectivity for C. bezziana against Chrysomya megacephala and Chrysomya rufifacies with factors of 5.9 and 6.4, respectively. The LuciTrap also discriminates with factors of 90 and 3.6 against Hemipyrellia sp. and sarcophagid flesh flies respectively, compared to the sticky trap. The LuciTrap/Bezzilure-2 system is recommended for screwworm fly surveillance as it is more attractive and selective towards C. bezziana and provides flies of better quality for identification than the sticky trap.     

The use of irradiated embryos of Chrysomya bezziana for the detection of the Old World screw-worm fly

Irradiation of Chrysomya bezziana embryos 1 h before hatching with doses less than or equal to 7 kilorad (kr) had a significant effect on percentage egg hatch, weights and survival of larvae. Doses greater than or equal to 1 kr allowed larval development to the end of the 3rd instar stage in vitro, but prevented normal pupal development. Cattle with wounds infested with 1st instar larvae derived from irradiated embryos had 3rd instar larvae present after 3 d but these failed to pupate. Thus it would be feasible to use such larvae for wound infestation for the enhanced detection of screw-worm fly in areas where the release of fertile flies is undesirable.     

Diversity of Ectoparasites in Sheep Flocks in Sa~o Paulo,Brazil

The occurrence of ectoparasites in sheep flocks is frequently reported but seldom quantified. Sheep production used to be a predominantly family activity in the state of Sa~o Paulo (Brazil), but it began to become a commercial activity in the past decade. Thus, information about the ectoparasites existing in sheep flocks has become necessary. The present data were obtained by means of questionnaires sent to all sheep breeders belonging to the `Associaça~o Paulista de Criadores de Ovinos' (ASPACO; Sa~o Paulo State Association of Sheep Breeders). Response reliability was tested by means of random visits paid to 10.6% of the respondents. Most of the properties (89.5%) reported the presence of one or more ectoparasites. Screw-worm (Cochliomyia hominivorax) was the most frequent ectoparasite (72.5%), followed by bot fly larvae (Dermatobia hominis, 45.0%), ticks (Amblyomma cajennense) and Boophilus microplus, 31.3%) and finally lice (Damalinia ovis, 13.8%). Combined infestations also occurred, the most common one being screw-worm with bot fly larvae (36.0%) followed by bot fly larvae with ticks (13.9%), screw-worm with ticks (9.3%), bot fly larvae with lice (6.9%), and ticks with lice (5.0%). The most common triple combination was screw-worm, bot fly larvae and ticks (12.8%). Breeds raised for meat or wool were attacked by bot fly larvae and ticks more often than other breeds. Lice were only absent from animals of indigenous breeds. The relationships among these ectoparasites are discussed in terms of sheep breeds, flock size, seasonality and the ectoparasitic combinations on the host.     

The effect of the brown ear-tick Rhipicephalus appendiculatus on the growth of Sanga and European breed cattle

The effects of larvae, nymphs and adults of the brown ear-tick Rhipicephalus appendiculatus on the growth of Bos indicus X B. taurus (Sanga) steers and on B. taurus steers and heifers was measured by exposing groups, maintained in the same pastures, to different levels of tick challenge. Larvae and nymphs had no significant effect on liveweight gains, but adults had a large effect. Each engorging female tick counted was associated with a loss of 4 g. Their effect on the Sanga cattle was minimised by host resistance which severely limited the number of ticks feeding on them. The B. taurus animals were severely affected and suffered extensive ear damage. Both breeds were subjected to screw-worm fly (Chrysomya bezziana) strike in the lesions caused by heavy tick infestations, but the B. taurus animals were much more prone to attack. The results provide a basis for calculating losses in production caused by this species of tick which is widespread in Africa.     

EVALUATION OF INSECTICIDE SMEARS FOR THE CONTROL OF SCREW-WORM FLY, CHRYSOMYA BEZZIANA, IN PAPUA NEW GUINEA

Three new insecticide smear preparations for the control of Chrysomya bezziana larvae infesting wounds of cattle have been tested under field and laboratory conditions and compared with an established preparation EQ 335 which is based on 3% lindane. Two preparations based on 3% coumaphos proved comparable to EQ 335 in the field trials and exhibited more prolonged residual effectiveness in laboratory tests. A smear preparation based on 2.5% methoxychlor was only effective in controlling 1 and 2 day-old larvae in wounds and was generally inferior to other smears tested in the laboratory.     

Control of horn flies on cattle with insecticide pellets fired from a CO2-operated pistol

A method is needed to control pyrethroid-resistant horn flies (Haematobia irritans) which would involve the intermittent application of insecticides to cattle without their confinement for treatment. Our objective was to test a CO2 gas-operated pistol, designed to shoot marking pellets, to determine the number of pellet applications required to obtain season-long control. Also, since horn fly resistance to pyrethroid insecticides is widespread, we tested ten other insecticides as concentrates in pellets. Six pellet pistol applications of 38% permethrin provided 84% control of horn flies for 15 weeks. Single pellet applications of ten non-pyrethroid insecticides indicated that none of these insecticides, at the concentrations tested, were as effective as permethrin for control of pyrethroid-resistant horn flies. Our field evaluation of the pellet-pistol method indicates that it has sufficient merit to justify further testing for horn fly control.     

Retrospective study of Old World screwworm fly (Chrysomya bezziana) myiasis in 59 dogs in Hong Kong over a one year period

This retrospective study examined the case records of Old World screw-worm fly myiasis in dogs in Hong Kong's New Territories. Myiasis due to OWSWF was identified and treated in 59 dogs at our clinic over a period of 1 year. Signalment, causes of initial wound, and treatments implemented, are reported. All cases recovered from myiasis with a combination of larvae removal and wound debridement, antibiotics, and topical and systemic insecticides. Whilst this parasite is currently exotic to Australia, much of the country is environmentally suitable (tropical and subtropical) for establishment of OWSWF.     

The effect of the bont tick (Amblyomma hebraeum) on the weight gain of Africander steers

The effects of the bont tick Amblyomma hebraeum on the productivity of cattle need to be quantified in order to design economically optimal control programs. Liveweight gains (LWGs) of three groups of Africander steers, maintained in the same pasture and exposed to zero, medium or high numbers of larvae, nymphs and adults of the tick, were measured. Larvae and nymphs had no significant effect on LWG but adults had a large, statistically significant effect (P less than 0.05). The tick-free group had an average LWG of 20 kg more than the heavily infested group after 3.5 months. No mortality was recorded from ticks or tick-borne diseases during the experiment. There was no relationship between the number of engorging adult female ticks counted and loss of LWG of individual animals. The latter suggests that exposure to ticks as well as engorgement by female ticks causes losses. The loss per adult female that completed engorgement was estimated, by relating the LWGs of individual animals to their tick infestations, to be 4 +/- 2 g per adult female tick. An alternative estimate, made by comparing the average LWG and tick infestations of each treatment group, was equal to 10 +/- 4 g. This latter estimate includes the effect of challenge (and rejection) as well as tick feeding and so was accepted as giving the best estimate. Screw-worm fly (Chrysomya bezziana) struck an average of 7.5% of the cattle infested with ticks in any week but the effects on the productivity of the cattle were minimized by immediate treatment. There was a significant, positive correlation between the incidence of screw-worm fly strike and the numbers of adult ticks counted on the experimental animals. The results provide data for calculating losses caused by A. hebraeum in different parts of its geographical range.     

Horn fly (Diptera: Muscidae) resistance to organophosphate insecticides

Insecticidal ear tags impregnated with organophosphate (OP) insecticides were used each year from 1989 to 1998 at Rosepine, LA. Weekly fly counts were conducted to evaluate control efficacy of the treatments, and bioassays were conducted at least twice per year to measure fly susceptibility to OP and pyrethroid insecticides. Between 1989 and 1992, the efficacy of 20% diazinon-impregnated ear tags was reduced from >20 to just 1 week of control. A high risk of control failure was observed when a resistance frequency of approximately 5% was measured in pre-season bioassays. Resistance to diazinon, fenthion, ethion, pirimiphos-methyl, and tetrachlorvinphos was observed. Esterase activity toward alpha-naphthyl acetate was significantly higher in flies collected at Rosepine in 1997 than in flies from a laboratory colony and from a susceptible field population.     

Dust bag and backrubber applications of insecticides for control of pyrethroid-resistant horn flies, Haematobia irritans (L.)

Pyrethroid-resistant horn flies, Haematobia irritans (L.), were controlled (92–100%) by fenvalerate, permethrin, coumaphos, dioxathion, crotoxyphos, malathion and chlorpyrifos applied by dust bags or backrubbers. Only methoxychlor and stirofos were not effective, indicating possible cross resistance to these insecticides.

Pyrethroids, which were not effective when applied from ear tags, were effective in dust bags or oil-type backrubbers, indicating that resistance may be overcome by high doses of insecticides.

Except for methoxychlor and stirofos, it appears that insecticides being recommended for horn fly control in dust bags and backrubbers are effective against pyrethoid-resistant horn flies.     

Chrysomya bezziana in pet dogs in Hong Kong: a potential threat to Australia

The Old World Screwworm fly (Chrysomya bezziana) has recently been causing aggressive myiasis in pet dogs in Hong Kong, and the Agriculture, Fisheries and Conservation Department of Hong Kong has confirmed the presence of Chrysomya bezziana in the territory. This report describes screwworm infestation in pet dogs presented for treatment at our clinic in the past year. Screwworm fly larvae were found in typically punched out round wounds or embedded in exposed or neglected wounds. Infested wounds had a characteristic strong offensive smell and oozed a sero-sanguineous exudate or frank blood. Removal of the larvae, wound treatment, continuous monitoring for re-infestation, application of insect repellants and protective housing were essential for successful treatment. Because Hong Kong is a source of pet migration or a transit point to Australia, the fly could threaten Australia.     

Toxicity of cypermethrin and diazinon to Haematobia irritans (Diptera: Muscidae) in its American southern range

Synthetic pyrethroids are considered currently less effective than organophosphate insecticides for controlling Haematobia irritans on cattle in its American southern range. To test the validity of this hypothesis, horn fly populations from 95 cattle herds in central-northern Argentina and southern Brazil were evaluated to determine 50% lethal concentrations (LC(50)) to cypermethrin and diazinon, respectively. Horn flies were exposed to filter papers and glass vials treated with cypermethrin and diazinon, respectively, and LC(50) values were determined using probit analysis. Two and 78 fly populations showed LC(50) values indicating susceptibility and resistance to cypermethrin, respectively, in comparison to historical LC(50) values obtained when the horn fly populations were susceptible to cypermethrin. Five fly populations had an undetermined resistance status to cypermethrin. The diazinon tests showed no obvious indications of H. irritans resistance. Thirty nine percent of farmers still rely on pyrethroids to control horn fly populations on cattle which represents a decreasing proportion from a few years ago when horn fly control was carried out using pyrethroids almost exclusively. Organophosphates could provide control for horn flies resistant to pyrethroids; however, the reliance on chemicals alone to control H. irritans is not considered a proper approach for the future.     

Effect of tiamulin on antipyrine kinetics in chickens

Tiamulin {14-deoxy-14[(2-diethylaminoethyl)-mercaptoacetoxy]-mutilin} hydrogen fuma-rate is a semisynthetic antibiotic. It is clinically effective against pathogenic mycoplasma organisms, e.g. Treponema hyodysenteriae , a large number of Gram-positive and some Gram-negative organisms (Drews et al. , 1975). Tiamulin has been shown, under controlled laboratory conditions (Laber & Schutze, 1975; Baughn et al. , 1978) and against natural infection under field conditions (Stipkovits et al. , 1977), to control respiratory tract infections effectively involving Mycoplasma galliseptkum in chickens and turkeys. It has also been demonstrated that tiamulin could be used as an aid in the control of avian coccidiosis produced by Eimeria acervulina and E. tenella in broilers chickens (Cruthers et al. , 1980).     

Efficacy of macrocyclic lactones for the control of larvae of the Old World screw-worm fly (Chrysomya bezziana)

OBJECTIVE: To assess the efficacy of four macrocyclic lactones for the control of larvae of the Old World Screw-worm Fly (OWS), Chrysomya bezziana, and to examine the effects of excreted residues on the dung fauna. ANIMALS: 100 heifers were divided into five groups of 20 animals. One group remained untreated, whereas the other groups were treated respectively with pour-on formulations of moxidectin, eprinomectin or doramectin, or a sustained-release bolus of ivermectin. PROCEDURES: At intervals of 1 to 15 weeks after treatment, five cattle from each group were challenged with newly-laid eggs of OWS. The efficacy of each treatment was determined 48 h later by comparing the number of myiases in the treated and untreated groups. Abundance of fly larvae in naturally-voided dung pads and the survival of a species of dung beetle, Onthophagus sagittarius, were used to assess the effects of drug residues on the dung fauna. RESULTS AND CONCLUSIONS: Moxidectin showed no activity against larvae of OWS during the first 14 days after treatment. Eprinomectin provided protection for 3 days after dosing, but failed at days 7 and 14, whereas doramectin was effective at day 7, but not at days 14 or 21. In contrast, no myiases were established on bolus-treated cattle from 14 to 102 days after treatment. Faecal residues of moxidectin had no effect on the survival of larvae of dung-feeding flies, whereas those of eprinomectin and doramectin reduced survival for 1 to 2 weeks. Dung voided by bolus-treated cattle inhibited fly breeding and had adverse effects on the development and survival of O sagittarius for up to 15 weeks after treatment.     

The activity of Bacillus thuringiensis var. israelensis against black fly larvae under field conditions in South Bohemia

The effectiveness of Bacillus thuringiensis var. israelensis spore suspension against black fly larvae was tested in two regulated brooks in the Ceské Bud?jovice district, South Bohemia. The sites under study were small, regulated, paved brooks of trapezoidal profile, with vegetation of different density, and with stream flow rates ranging from 40 to 90 cm/sec. Lyophilized spores (produced by Roger Belon) at a final concentration of 1 X 10(5) spores per ml were used. The spore efficacy was determined in both natural and artificial substrates in the field and under laboratory conditions, on the larvae collected at the control sites. A 90-100% mortality of the larvae was recorded in all parts of the brooks examined both in the natural samples studied in laboratory and in those kept on artificial substrates. In the area of fading spore suspension action, a higher percentage of the last-instar larvae was found in larval population which may be ascribed, in agreement with other authors, to an increased susceptibility of younger larvae to the preparation. The results of the tests demonstrated that Bacillus thuringiensis var. israelensis is an effective agent to control the black fly species occurring in Central Europe and may be of value mainly in the control of some species of veterinary importance overpopulated in regulated brooks.     

大田常用农药对家蚕的熏蒸毒性测试

为减少粮桑混栽地区大田使用农药不当对蚕桑生产造成的损失,采用密闭熏蒸法测定了7种大田常用农药对家蚕的熏蒸毒性。在30℃环境中经过24 h,对2龄起蚕的LC50:敌敌畏0.1860 mg/m3,敌畏.毒1.3241 mg/m3,毒死蜱48.4111 mg/m3,氟腈.唑磷139.8818 mg/m3,三唑磷161.1514 mg/m3,氟虫腈208.330 mg/m3,吡虫啉333.330mg/m3时2龄起蚕仍无中毒症状。在25℃下经过24 h,对2龄起蚕的LC50:敌敌畏0.2020 mg/m3,敌畏.毒3.7282mg/m3,毒死蜱91.3669 mg/m3。结果表明:农药对家蚕的熏蒸毒性随着温度的升高而增强;敌敌畏、敌畏.毒对家蚕的熏蒸毒性最强,毒死蜱有一定的熏蒸毒性,三唑磷、氟腈.唑磷、氟虫腈、吡虫啉对家蚕的熏蒸毒性较小。     

Knowledge and attitudes of cattle owners regarding trypanosomosis control in tsetse-infested areas of Uganda

A pilot survey using a structured questionnaire was conducted in Tororo and Busia districts of Uganda on the knowledge and attitudes of cattle owners regarding tsetse fly and trypanosomosis control, in order to understand factors that hindered their full participation. A total of 81 cattle owners was randomly selected and interviewed, of which 92.5% were aware of tsetse flies and trypanosomosis and 87.6% recognised animal trypanosomosis as a problem in the area. Most cattle owners were aware of tsetse fly trapping (76.5%), isometamidium chloride use (55.5%), diminazene aceturate use (48%) and pour-on applications (18.5%). However, knowledge did not coincide with the application of control measures. Despite the widespread awareness, tsetse fly trapping and pour-on applications were used by only a small percentage of cattle owners (7.5% applied tsetse fly trapping while 76.5% were aware of it; 1.2% applied pour-on insecticides while 18.5% were aware of them). Differences between awareness and application were highly significant for tsetse fly trapping (chi2 = 67.8, d.f. = 1, P < 0.001) and pour-on applications (chi2 = 10.8, d.f. = 1, P < 0.05), but not for isometamidium chloride use (chi2 = 0.08, d.f. = 1, P = 0.77) and diminazene aceturate use (chi2 = 0.00, d.f. = 1, P = 1.00). Most cattle owners (97.5%) were willing to participate in future control programmes, but preferred participating on a group basis (85.2%) rather than individually (14.8%). The 4 most favoured control options in order of importance were: fly traps supplied by the government and maintained by cattle owners; contribution of labour by cattle owners for trap deployment; self-financing of trypanocidal drugs and self-financing of pour-on insecticide. The control options that should be selected in order to elicit full participation by cattle owners are discussed.