Ectoparasites of medical and veterinary importance: drug resistance and the need for alternative control methods

Abstract

Objectives Despite multiple attempts at eradication, many ectoparasites of humans and domestic livestock remain a persistent problem in the modern world. For many years, a range of pesticide drugs including organophosphates, organochlorides and synthetic pyrethroids provided effective control of these parasites; but intensive use of these drugs has led to the evolution of resistance in many target species. This paper aims to review the effectiveness of current control methods and discuss potential alternatives for the long term sustainable control of ectoparasites. Key Findings Important medical ectoparasites such as scabies mites, head lice and bed bugs present a significant public health problem, and so adequate control methods are essential. Ectoparasites of domestic livestock and farmed fish (for example sheep scab mites, poultry mites and sea lice) are also of concern given the increasing strain on the world's food supply. These parasites have become resistant to several classes of pesticide, making control very difficult. Recently, an increasing amount of research has focussed on alternative control methods such as insect growth regulators, biological control using essential oils or fungi, as well as vaccine development against some ectoparasites of medical and veterinary importance. Summary Drug resistance is prevalent in all of the ectoparasites discussed in this review. A wide variety of alternative control methods have been identified, however further research is necessary in order for these to be used to successfully control ectoparasitic diseases in the future.

Tick vaccines: current status and future directions

“…In this context, research on tick vaccine development is more advanced than that reported for other major ectoparasites. Therefore, tick vaccine research may provide models for development of vaccines against other arthropod pests [20,83,[85][86][87][88]. In this direction, recent efforts using tick Subolesin or the Akirin homolog in mosquitoes have shown how vaccination with these antigens protects against multiple ectoparasites and the infection with vector-borne pathogens [42,43,89] (BOX 1).…”

Behaviour in the toolbox to outsmart parasites and improve fish welfare in aquaculture

“…). The use of chemotherapeutants in aquaculture creates a strong selection pressure, and the fast generation time of parasites and pathogens allows for rapid adaptation to treatments (Boots ; McNair ). The use of chemotherapeutants to limit and combat disease and parasites is, thus, unlikely to remain effective in areas where genetic resistance can penetrate the population quickly (e.g.…”

The eco-evolutionary impacts of domestication and agricultural practices on wild species

“…For example, at least 10 species of gastrointestinal nematodes associated with cattle have evolved resistance to antihelmintic drugs [35] and numerous ectoparasitic arthropods affecting cattle, sheep, poultry and farm-raised salmon have evolved resistance to insecticides and acaricides [43]. In addition, the widespread use of antimicrobials in both livestock and crop production has led to the evolution of resistance in numerous disease agents [39,40].…”