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Epidemiological Aspects
Published in Yamuna Deepani Siriwardana, Leishmaniasis in Sri Lanka, 2023
Potential for the local vector to develop insecticide resistance has also been identified recently (Surendran et al., 2005). Irrational use of insecticides has been shown to result in undesired sequelae, including insecticide resistance in the past (Sanyal et al., 1979). The beneficial effects of sandfly control in the numerous Old-World foci of zoonotic cutaneous leishmaniasis have often been transient. Timely treatment of humans and dogs in such foci is recommended (Desjeux, 1992). Studies to identify sand fly gut microbiota for paratransgenesis, a vector-based method of control of Leishmania parasites, have shown encouraging results (Gunathilaka et al., 2020).
The Challenge of Parasite Control
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
The use of transgenic vectors is not without important problems. Any reduction strategy, for instance, requires regular and repeated introduction of the transgenic organism to ensure sustained control. Furthermore, genetically modified vectors are frequently at a competitive disadvantage as compared to their wild-type conspecifics. The genetic manipulation itself often renders transgenic vectors less fit than more vector-competent and robust wild-type vectors. Consequently, some of the same issues that plague more conventional control efforts, such as the need for regular reintroduction and sustained effort, are relevant for modified vectors as well. One strategy to help overcome the potential reduced fitness of transgenic vectors would be the use of paratransgenesis: the genetic manipulation of the vector’s microbiota rather than the vector itself. To cite just one example, Asaia bogorensis, a vertically transmitted bacterium found in the digestive tract and reproductive organs of Anopheles mosquitoes, has been genetically modified to express a protein called scorpine, derived from scorpion venom. The transgene is accompanied by promoters that are activated by nutrients found in a mosquito’s blood meal. Thus, scorpine is only produced immediately following a blood meal, which reduces or eliminates any fitness cost on the mosquito. Scorpine prevents the development of the Plasmodium ookinete stage within the mosquito (see Figure 2, Page 525 in the Rogues’ Gallery). Not only do such mosquitoes fail to produce the sporozoites infective to humans, but because the bacterium is vertically transmitted, it is able to spread through the mosquito population. Other issues relate to potential environmental problems that may result from the introduction of transgenic organisms. The unintended or unanticipated effects of such an introduction are largely unknown.
Modeling tick vaccines: a key tool to improve protection efficacy
Published in Expert Review of Vaccines, 2020
José de la Fuente, Agustin Estrada-Peña, Marinela Contreras
In the upcoming years, advancements in tick genome sequencing and annotation (i.e. [58–60]) and the characterization of tick-host-pathogen interactions (i.e. [61–63]) will also contribute to these objectives. As previously proposed [6], in the near future novel genetic editing technologies such as clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein-9 nuclease (Cas9) (CRISPR-Cas9) [64] together with paratransgenesis using tick commensal or pathogenic bacteria [65–68] could be developed for autocidal tick control and the production of ticks with lower vector competence. These new developments could be combined with vaccines and traditional control methods for an effective control of tick-borne diseases.