Fly larvicidal activity in the faeces of cattle and pigs treated with endectocide products

A look into the Medical and Veterinary Entomology crystal ball

Medical and Veterinary Entomology (MVE) represents a leading periodical in its field and covers many aspects of the biology and control of insects, ticks, mites and other arthropods of medical and veterinary importance. Since the first issue of the journal, researchers working in both developed and developing countries have published in MVE, with direct impact on current knowledge in the field. An increasing number of articles dealing with the epidemiology and transmission of vector-borne pathogens have been published in MVE, reflecting rapid changes in vector distribution, pathogen transmission and host-arthropod interactions. This article represents a gaze into the crystal ball in which we identify areas of increasing interest, discuss the main changes that have occurred in the epidemiology of parasitic arthropods since the first issue of MVE, and predict the principal scientific topics that might arise in the next 25 years for scientists working in medical and veterinary entomology.

A xenodiagnostic method using Musca domestica for the diagnosis of gastric habronemosis and examining the anthelmintic efficacy of moxidectin

Equine habronematidosis has a global distribution and is caused by three spirurid species, Habronema muscae, Habronema microstoma and Draschia megastoma. A case of cutaneous habronematidosis in a stallion in a stable in Dubai, UAE gave occasion to investigate the parasite situation on the farm. Patent H. muscae infections were diagnosed in 18 out of 49 horses in a stable in Dubai, UAE with a xenodiagnostic test using houseflies as indicator host. All horses in the stable were treated with a single dose of moxidectin administered orally as 2% gel in a dosage of 0.4 mg/kg body weight and the efficacy of this targeted treatment was studied. Habronema infection was terminated in all horses. A fly survey conducted at the farm prior and after treatment revealed two muscid species: Musca domestica and Stomoxys calcitrans. Only M. domestica caught at the farm showed a natural infection with Habronema larvae prior and shortly after anthelmintic treatment. Later, examination of flies caught at the farm in monthly intervals up to the end of observation (8 months after treatment) gave negative results. The absence of infection in the intermediate host was an indication of the eradication of stomach worms. The described xenodiagnostic test is a useful tool to diagnose H. muscae infections and can be used to evaluate the efficacy of nematocides in equines.

A review on the toxicity and non-target effects of macrocyclic lactones in terrestrial and aquatic environments

The avermectins, milbemycins and spinosyns are collectively referred to as macrocyclic lactones (MLs) which comprise several classes of chemicals derived from cultures of soil micro-organisms. These compounds are extensively and increasingly used in veterinary medicine and agriculture. Due to their potential effects on non-target organisms, large amounts of information on their impact in the environment has been compiled in recent years, mainly caused by legal requirements related to their marketing authorization or registration. The main objective of this paper is to critically review the present knowledge about the acute and chronic ecotoxicological effects of MLs on organisms, mainly invertebrates, in the terrestrial and aquatic environment. Detailed information is presented on the mode-of-action as well as the ecotoxicity of the most important compounds representing the three groups of MLs. This information, based on more than 360 references, is mainly provided in nine tables, presenting the effects of abamectin, ivermectin, eprinomectin, doramectin, emamectin, moxidectin, and spinosad on individual species of terrestrial and aquatic invertebrates as well as plants and algae. Since dung dwelling organisms are particularly important non-targets, as they are exposed via dung from treated animals over their whole life-cycle, the information on the effects of MLs on dung communities is compiled in an additional table. The results of this review clearly demonstrate that regarding environmental impacts many macrocyclic lactones are substances of high concern particularly with larval instars of invertebrates. Recent studies have also shown that susceptibility varies with life cycle stage and impacts can be mitigated by using MLs when these stages are not present. However information on the environmental impact of the MLs is scattered across a wide range of specialised scientific journals with research focusing mainly on ivermectin and to a lesser extent on abamectin doramectin and moxidectin. By comparison, information on compounds such as eprinomectin, emamectin and selamectin is still relatively scarce.

Area-wide impact of macrocyclic lactone parasiticides in cattle dung

Following the treatment of cattle with veterinary parasiticides and insecticides, residues are excreted into the dung in concentrations that may be toxic to functionally important dung-colonizing insects. In the dung, these residues cause a range of well-studied lethal and sub-lethal effects, the magnitudes of which vary with the compound used, mode of administration and concentration, and the insect species in question. Particular concern has been associated with the use of macrocyclic lactones in this context. Loss of insect colonizers may delay pat decomposition, but field studies report contrasting results that reflect confounding factors such as weather conditions, pat moisture content, pat location, time of year and dung insect species phenologies. The question of fundamental concern is whether the impacts seen in experimental or laboratory studies are likely to have a functional impact on insect populations, community interactions and the economically important process of dung decomposition. Recent studies which have attempted to address these wider, landscape-level impacts in temperate ecosystems are reviewed here. These show that the extent to which chemical residues may have any sustained ecological impact will depend on both a range of farm management factors, such as the temporal and spatial patterns of chemical use, the number of animals treated and the choice of active ingredient, and a range of insect-related factors, such as abundance, population dynamics and dispersal rates. However, they also demonstrate that considerable uncertainty remains about the likely extent of such effects and that current data are insufficient to support firm conclusions regarding sustained pasture-level effects. More large-scale, longterm field experiments are required, particularly in relation to insect dispersal and functional interactions within the dung insect community.

RESISTÊNCIA À IVERMECTINA EM POPULAÇÕES DE MUSCA DOMESTICA (DIPTERA: MUSCIDAE) PROVENIENTES DE GRANJAS DE GALINHAS POEDEIRAS

RESUMO Bioensaios concentração-resposta foram realizados com o objetivo de estudar o efeito larvicida e detectar possível resistência à ivermectina em dez populações de M. domestica provenientes de granjas de galinhas poedeiras. Para tal finalidade, o meio de cultura para larvas foi tratado com diferentes concentrações de ivermectina (0,015; 0,03; 0,06; 0,125; 0,25 e 0,5 ppm). Atividade larvicida da ivermectina e anomalias nas pupas foram detectadas. A população mais resistente à ivermectina foi Monte Mor, SP (CL= 0,262 ppm e FR= 13,1). As populações de Campinas, SP (CL= 0,141 ppm 50 50 e FR = 7,1), Promissão, SP (CL= 0,110 ppm e FR = 5,5), Santa Cruz da Conceição, SP (CL= 0,102 50 50 ppm e FR = 5,1), Holambra, SP (CL= 0,071 ppm e FR = 3,6) e Hortolândia, SP (CL= 0,068 ppm e 50 50 FR = 3,4) foram mais resistentes que as de Sumaré, SP (CL= 0,052 ppm e FR = 2,6), Sarapuí, SP (CL 50 50 = 0,050 ppm e FR = 2,5) e Itanhandu, MG (CL50 = 0,047 ppm e FR = 2,4). A população mais susceptível à ivermectina foi Grande Porto Alegre, RS (CL50 = 0,020 ppm e FR = 1,0). Os resultados indicam que a ivermectina pode ser eficaz contra larvas deM. domestica. Entretanto, resistência foi suspeitada em algumas das populações, sendo importante a realização de novos estudos nesses locais.