Blocking Transmission of Vector‐borne Diseases

Abstract

a b s t r a c tVector-borne diseases are responsible for significant health problems in humans, as well as in companion and farm animals. Killing the vectors with ectoparasitic drugs before they have the opportunity to pass on their pathogens could be the ideal way to prevent vector borne diseases. Blocking of transmission might work when transmission is delayed during blood meal, as often happens in ticks. The recently described systemic isoxazolines have been shown to successfully prevent disease transmission under conditions of delayed pathogen transfer. However, if the pathogen is transmitted immediately at bite as it is the case with most insects, blocking transmission becomes only possible if ectoparasiticides prevent the vector from landing on or, at least, from biting the host. Chemical entities exhibiting repellent activity in addition to fast killing, like pyrethroids, could prevent pathogen transmission even in cases of immediate transfer. Successful blocking depends on effective action in the context of the extremely diverse life-cycles of vectors and vector-borne pathogens of medical and veterinary importance which are summarized in this review. This complexity leads to important parameters to consider for ectoparasiticide research and when considering the ideal drug profile for preventing disease transmission.

Haemoplasmas in wild rodents: Routes of transmission and infection dynamics

“…Four pieces of evidence support this “dead bacterial copies” explanation, namely (a) the absence of a correlation between the probability of a rodent and its fleas to be infected by MHLB in nature (Messika‐Madmon, ), (b) the absence of a correlation between flea burden and the probability of a flea being infected by MHLB (Kedem et al., ), (c) the similarity between the MHLB loads of dead and live fleas and between those of fleas fed on donor and those fed on recipient rodents in Experiment 1 and (d) the lack of MHLB in fleas that were allowed to complete bloodmeal digestion during Experiment 1. Even if we are wrong, and fleas can transmit MHLB by their gut or their mouth parts without replication (Schorderet‐Weber, Noack, Selzer, & Kaminsky, ; Shaw, Kenny, Tasker, & Birtles, ; Vobis, D'Haese, Mehlhorn, & Mencke, ), our results indicate that fleaborne transmission is likely not their main transmission route.…”

Antiparasitics in Animal Health: Quo Vadis?

“…If so, isoxazolines might also be able to impede arthropod-borne diseases, such as Lyme disease, as demonstrated in dogs [31], or even neglected tropical diseases of humans, such as human African trypanosomiosis (sleeping sickness), leishmaniosis, and malaria, for which respective claims have already been made in the patent literature [32][33][34][35][36][37]. However, for the time being, the question remains open as to how fast systemic isoxazolines act on the different feeding arthropod vectors [38,39]. It would be essential that the ectoparasite vector is killed before the disease-causing agent is transmitted [7].…”

Risk factors associated with tick infestations on equids in Khyber Pakhtunkhwa, Pakistan, with notes on Rickettsia massiliae detection

“…Ticks cause substantial economic losses in various communities around the world, but especially in low-income livestock holders in tropical and subtropical regions, where approximately 80% of the world’s cattle population is at risk of infestation [ 1 ]. These hematophagous ectoparasites play a major role in the transmission of pathogens, including bacteria, such as intracellular coccobacilli of the genus Rickettsia , and several protozoans and viruses that cause disease and are a threat to human and veterinary health [ 2 – 4 ]. Only 10% of tick species have been identified as carriers of pathogens; the remaining species require further research to determine whether they are vectors of disease.…”