Field trials to confirm the efficacy of ivermectin jetting fluid for control of blow fly strike in sheep

Traumatic sheep myiasis: A review of the current understanding

Myiasis, or the infestation of live humans and vertebrate animals by dipterous larvae, is a health issue worldwide. The economic impact and potential threat to animal health and wellbeing of this disease under the animal husbandry sector is considerable. Sheep are a highly vulnerable livestock category exposed to myiasis (sheep strike), due to several unique predisposing factors that attract flies. The successful mitigation of this disease relies on a thorough understanding of fly population dynamics associated with the change in weather patterns and the evaluation of this disease through different branches of science such as chemistry, molecular biology, and microbiology. The present review provides a summary of the existing knowledge of strike in sheep, discussed in relation to the application of volatile organic compounds, metagenomics, and molecular biology, and their use regarding implementing fly control strategies such as traps, and to increase the resilience of sheep to this disease through improving their health and wellbeing.

Treatment of nasal myiasis with ivermectin irrigation

We describe a case of nasal myiasis due to Musca domestica in a 97-year-old Peruvian farmer with a previously undiagnosed mucocutaneous leishmaniasis. Initial attempts to remove the fly larvae using manual extraction with a toothed forceps and normal saline irrigation were unsuccessful. On subsequent nasal irrigation with ivermectin solution, the patient self-expulsed approximately 50 larvae within 15 min. He also received a course of oral ivermectin. A post-treatment CT scan revealed clear sinuses. Here, we propose that ivermectin irrigation is a simple and effective treatment for nasal myiasis.

Ovine cutaneous myiasis: effects on production and control

Ovine cutaneous myiasis ('fly strike') remains a major sheep health problem in many areas of the world. Myiasis risk is the result of a complex interaction of factors, such as fly and host abundance, host susceptibility, climate and, critically, husbandry and management strategies, all of which change seasonally in space and time. Given the complexity of the interacting factors, changes in myiasis incidence are hard to predict, as accordingly are the optimal husbandry responses required to manage the problem. Here the important risk factors are briefly reviewed and the future changes in myiasis incidence under conditions of anticipated climate change are considered. It is concluded that future work should focus in particular on evaluating the optimum use of integrated management, such as the combination of insecticide and trap use, in different environments under a range of farming regimes.

Field efficacy of an ivermectin jetting fluid for control of the sheep body louse Bovicola (Damalinia) ovis in New Zealand

The efficacy of an ivermectin jetting fluid against the sheep body louse, Bovicola (Damalinia) ovis, in long-woolled sheep was investigated in three field trials. In all trials, louse populations in hand-jetted sheep were reduced to nondetectable numbers within 2 weeks of treatment. Bv comparison, shorn and unshorn control sheep maintained detectable infestations for the duration of the trials.

Toxicity and behavioural effects of diet-borne alkaloids on larvae of the black blowfly, Phormia regina

Larvae of the black blowfly, Phormia regina (Meigen) (Diptera: Calliphoridae) were exposed for 24 h to artificial diets that contained one of the following alkaloids: arecoline, caffeine, nicotine, quinine, sparteine or strychnine at either 1000 or 100 p.p.m. Each of the alkaloids caused reduced weight gain, relative to a control population in a no-choice bioassay and, with the exception of quinine, all alkaloids caused reduced larval weights in a choice bioassay. Larvae were unable to move away from diets containing arecoline (1000 and 100 p.p.m) and congregated away from diets containing 1000 p.p.m. quinine. Arecoline (1000 p.p.m) and both concentrations of nicotine caused significant mortality of larvae. Over a longer period (120 h), 10 and 1 p.p.m. nicotine resulted in significant numbers of larvae congregating away from a treated diet. Ten p.p.m. nicotine caused reduced weight gain over 120 h, although larvae provided with a choice were less affected. Exposure of larvae to dried residues of nicotine for 2 h did not affect subsequent development.

Persistent activity of topical ivermectin against artificial infestations with Hypoderma lineatum (Diptera: Oestridae)

In controlled experiments utilizing artificial infestations, a topical formulation of ivermectin (IVOMEC Pour-On for Cattle) was 100% effective against migrating first instar Hypoderma lineatum for 3 weeks following treatment. Larvae were apparently killed early in the infestation as no significant level of specific antibodies was found in the treated calves. At 4 weeks post-treatment the efficacy remained high at 96%; mortality of larvae in the one calf in which warbles were observed and from which mature third instars were collected, was higher than that seen in the untreated calves, indicating some level of treatment induced effect. No specific antibodies were detected in calves that did not develop palpable warbles. Antibody kinetics in those calves from which viable larvae emerged were typical. The length of activity of this product against early stages of the cattle grub makes it practical to apply treatment up to 3 weeks before the end of fly activity.

Control of blowfly strike in sheep: current strategies and future prospects

Blowfly strike is a cutaneous myiasis in sheep caused by infestations of larvae principally from the family Calliphoridae, particularly the species Lucilia cuprina and Lucilia sericata. These larval infestations cause considerable economic losses to the wool industry. Established control methods have served the industry well in the past, but there are growing deficiencies with these methods. In particular, there is widespread resistance to organophosphorus insecticides and potential difficulties associated with the presence of chemical residues derived from insecticides in wool and waste products which must be disposed of by the industry. There is also growing opposition to the radical surgical procedures used to decrease the susceptibility of sheep to blowfly strike. Consequently, there is a need for the development of alternative control measures. This review examines critically the present control methods and discusses the range of options available for the development of new control strategies. Many of the latter involve novel approaches which will strongly complement current control measures.

Efficacy of ivermectin and moxidectin injection against larvae of Wohlfahrtia magnifica (Diptera: Sarcophagidae) in sheep

The therapeutic efficacies of ivermectin (Ivomec injection, Merck Sharp & Dohme B.V.) and moxidectin (Cydectin 1% injection, American Cyanamid Company) were evaluated in sheep naturally infested with larvae of Wohlfahrtia magnifica. Sheep were randomly allocated to one of the 2 groups, each consisting of 19 animals. Sheep in one group received ivermectin and those in the other, moxidectin by subcutaneous injection at a dose of 0.2 mg/kg body weight. Evaluation was performed at 19, 24, 28, 39, 43, 48, 52, 63, 67, 72, 87, 96, 120, 144 and 168 h after treatment. At 144 and 168 h post-treatment, late third-instar larvae were collected from wounds of four sheep in both groups and from untreated, infested sheep. These larvae were reared in the laboratory to assess adult emergence. Neither ivermectin nor moxidectin was effective as a rapid acting treatment or as a long-term, or even short-term, prophylactic. Despite the treatment, 30-40% of sheep had live larvae at every evaluation. Although larvae disappeared from the wounds of some sheep in both groups after the treatment, the wounds in these animals failed to recover and were reinfested by larvae of W. magnifica. On day 7 post-treatment the trial had to be finished because the majority of treated sheep were severely infested by Wohlfahrtia maggots. The average number of infested sheep in the two groups and the number of adults that were produced from larvae collected from treated sheep indicate that ivermectin and moxidectin did not differ significantly in efficacy.