Abstract
BackgroundDespite intensive control measures including governmental campaigns using highly-efficacious systemic insecticides, there is evidence for persisting or recurring bovine Hypoderma species populations in parts of Europe, the USA and Canada. The present study evaluated the efficacy of LONGRANGE® (eprinomectin 5% w/v extended-release injection) against the infestation of cattle with Hypoderma lineatum, which is considered to be the predominant bovine warble fly in southern Europe and in North America.MethodsThirty-six local breed cattle sourced in an endemic area in southern Italy and confirmed positive for Hypoderma exposure by ELISA were randomly assigned to three groups of 12 animals each. Cattle of one group served as control and received saline injectable solution, whereas those in the two other groups received LONGRANGE® by subcutaneous injection. LONGRANGE® was administered once, either when Hypoderma larvae were expected to be first-instars (L1) or after warbles development, with Hypoderma larvae moulting to the second-(L2) and third-(L3) instars. Cattle were checked at intervals for warbles and Hypoderma larvae were collected, examined for their viability and morphologically identified. The detection of Hypoderma on cattle was terminated when warbles were no longer emerging.ResultsAll intact larvae collected were identified as H. lineatum. No live larvae were collected from any animal treated with LONGRANGE® while live specimens were sampled from nine of the 12 control cattle (1 to 9 larvae per animal) (P = 0.0001 at α = 0.05). LONGRANGE® treatment was well accepted and no adverse events related to treatment or other health problems were observed.ConclusionsThis study confirmed the continued ‘preventive’ (efficacy against migrating L1) and ‘therapeutic’ (efficacy against L2 and L3 in warbles) efficacy of LONGRANGE® against H. lineatum infestation of cattle under contemporary field conditions.
Highlights
Despite intensive control measures including governmental campaigns using highly-efficacious systemic insecticides, there is evidence for persisting or recurring bovine Hypoderma species populations in parts of Europe, the USA and Canada
The development in the late 1950s of systemic organophosphate insecticides for use in cattle followed by the introduction of the macrocyclic lactones in the 1980s [3, 4] resulted in a marked decrease in the prevalence of bovine hypodermosis in most developed countries in the northern hemisphere and even eradication in some areas following the implementation of area-wide campaigns or national control programs [5, 6]
Both species are still known to occur in North America and Europe [7], only scarce data are available on the current relative distribution of the two cattle warble fly species
Summary
Despite intensive control measures including governmental campaigns using highly-efficacious systemic insecticides, there is evidence for persisting or recurring bovine Hypoderma species populations in parts of Europe, the USA and Canada. The species established in cattle in North America and Europe are H. bovis, referred to as the larger warble fly or northern cattle grub, and H. lineatum, the lesser warble fly or common cattle grub. Both species are still known to occur in North America and Europe [7], only scarce data are available on the current relative distribution of the two cattle warble fly species This general lack of knowledge about the current prevalence of the two Hypoderma species in endemic countries is due to the overall significant decrease in incidence and the preferred use of ELISAs in surveillance programs in place of clinical examination of cattle or of carcasses at abattoirs. Seems to be the predominant species in North America and southern Europe [9, 10] where it has been rarely reported to infest humans causing creeping subdermal myiasis [11,12,13] as the host specificity is not absolute
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