Dermatobia hominis : Potencial risk of resistance to macrocyclic lactones

Abstract

Dermatobia hominis is an ectoparasite that infests various species of mammals, including cattle, impairing the quality of cowhides and leather. After observing natural infestation with D. hominis larvae in cattle on two farms in the state of São Paulo, Brazil, we evaluated the efficacy of two macrocyclic lactones, ivermectin and moxidectin, against this parasite. The drugs were administered to 10 animals in each group, following the manufacturer's instructions. The groups were: Group 1-treated with ivermectin (0.2mg/kg of body weight (BW)); Group 2-treated with moxidectin (0.2mg/kg BW); and Group 3-control (untreated). On the farm in Pardinho, a total of 12 and 16 live larvae were found in 6 and in 8 animals 10 days after the treatment with ivermectin and moxidectin, respectively, while in the control group 4 bovines had a total of 7 live larvae. On the farm in Anhembi, 2, 4 and 6 live larvae were extracted from ivermectin, moxidectin and control groups, respectively, after the treatment. This is the first report of the presence of live D. hominis larvae after the treatment of cattle with ivermectin and moxidectin in Brazil.

Control of Dermatobia hominis larvae by manual extraction is effective and does not cause abscesso

“…Many cattle breeders having the empirical perception of loss or decrease in efficacy of insecticides against D. hominis larvae and attributing this to the emergence of resistant parasites choose to discontinue the use of certain insecticides in order to employ more broadspectrum drugs (Oliveira-Sequeira et al 2014). Regarding injectable endectocidal products, ivermectin and moxidectin, launched in the 1980s and 1990s, respectively (Roncalli & Benitez Usher 1988, Silva Netto et al 2001, and are still widely used in our environment for botfly control, have already reports of resistance of botfly to these products (Neves et al 2015). Not to mention that injectable endectocides and other chemical groups in the Pour on formulation cause negative environmental impacts by reducing the coprophagous fauna, which causes a delay in manure decomposition (Bang et al 2007) and the possibility of inducing resistance to other parasite species, such as nematodes, ticks and other flies, by the amount or by unnecessary exposure to these products (Alegría-López et al 2015).…”

“…When the L3 is mature, it spontaneously leaves the host, usually at night (Ribeiro & Oliveira 1983), actively seeking to bury itself in the ground, where it will pupate and turn into a new fly in 26 to 31 days (25 o C, UR 70%) (Barbosa et al 2002). Its control is usually done with chemicals, and those based on macrocyclic lactones have been used successfully (Roncalli & Benitez Usher 1988, Moya-Borja et al 1993, Silva Netto et al 2001; nevertheless, there have been reports of failure in the control of this myiasis with the use of these products (Neves et al 2015). The nodules of the botfly do not seem to cause much harm from a clinical point of view to the point of impairing the weight gain of the animals that harbor them (Magalhães & Lesskiu 1982.…”

Prophylactic Effects of Ivermectin and Closantel Treatment in the Control of Oestrus ovis Infestation in Sheep

“…The intensification of sheep farming and emergence of drug-resistant parasites have brought new challenges regarding the prophylaxis and treatment of small ruminant parasitism. Frequent cases of anthelmintic resistance have been reported ( 12 – 14 ) as well as ectoparasites, such as Dermatobia hominis ( 15 , 16 ), Rhipicephalus microplus ( 17 ) and Cochliomyia hominivorax ( 18 ), with resistance to the treatments with macrocyclic lactones. For this reason, the aim of this work was to verify whether closantel and ivermectin that have been used for decades are still effective in sheep naturally infested with O. ovis .…”

Eficácia da associação de cipermetrina, clorpirifós, butóxido de piperonila e fluazuron contra larvas de Dermatobia hominis em bovinos naturalmente infestados

“…O controle desta mosca depende unicamente da aplicação de inseticidas nos animais. Apesar de não existirem indícios de resistência, novos ativos ou associações devem testados com a finalidade de facilitar seu controle (Moya-Borja, 2003;Oliveira-Sequeira et al, 2014;Neves et al, 2015).…”