Identification of the G184C, C190A and T2134A mutations in the para-sodium channel gene of the southern cattle tick Rhipicephalus (Boophilus) microplus associated with resistance to cypermethrin in northern Veracruz, Mexico.

The southern cattle tick (Rhipicephalus microplus) represents one of the ectoparasites with the greatest distribution worldwide. Infestations by this arthropod can cause a decrease in the production of meat and milk, as well as anaemia and the transmission of bacterial and parasitic agents. For this reason, several active molecules have been developed to control these arthropods. A widely used group of ixodicides are pyrethroids, especially cypermethrin, which have knockdown effects on ticks. Resistance to cypermethrin has been reported in ticks since the 2000s; it was registered for the first time in Mexico in 2009. Even though multiple studies have evaluated resistance with conventional tests, there are few studies in Mexico that have identified the presence of single nucleotide polymorphisms (SNPs) associated with resistance. Hence, the aim of this work was to monitor three mutations associated with resistance in the sodium/chlorine channel in eight populations of ticks from northern Veracruz. Engorged adult females were collected from which genomic DNA was extracted. Subsequently, three mutations in domains II and III of para­sodium channel gene were detected by conventional PCR and sequencing. Global alignments were done with the reference sequences deposited in GenBank. A total of 116 engorged females were analysed, of which 10 tested positive for G184C and C190A of domain II of the para­sodium channel gene. T2134A was present in domain III in a single production unit. This is the first work where molecular monitoring of cypermethrin resistance has been carried out in the northern zone of the state of Veracruz.

Molecular detection of Rickettsia felis in fleas and ticks collected from dogs and cats of Puebla, Mexico.

Fleas and ticks represent the two main groups of ectoparasites that infest companion animals. In particular, the flea Ctenocephalides felis felis and several members of the Rhipicephalus sanguineus complex are the main vectors of a wide range of pathogens on the American continent. They are competent vectors for several members of the genus Rickettsia, which encompass at least 15 pathogenic obligate intracellular bacteria that colonize the endothelial cells of vertebrates. In Mexico, 10 species of Rickettsia belonging to three groups have been detected in six species of ectoparasites from dogs in 9 of the 32 states of the country. However, in some larger regions of the country, active epidemiological surveillance has not been carried out. For this reason, the aim of this study was to identify the presence of members of the genus Rickettsia in fleas and ticks of dogs and cats in the state of Puebla, Mexico. A cross-sectional study was carried out to collect ectoparasites of dogs and cats during August to November 2019. Samples were fixed in 70% ethanol and examined to identify the presence of Rickettsia DNA by the amplification and sequencing of specific fragments of the gltA and ompB genes using conventional PCR. The recovered sequences were compared with those deposited in GenBank, and phylogenetic analyses were carried out to identify the position of the pathogens detected with respect to the valid species previously reported worldwide. Additionally, ecological parameters of the ectoparasite infestations were also calculated. We recovered 196 ectoparasites belonging to two species, 33 C. felis felis and 163 R. sanguineus s.l. (Rhipicephalus linnaei), parasitizing 46 hosts (42 dogs and 4 cats) in 11 localities of the state of Puebla. We detected the presence of Rickettsia felis in three pools of C. felis felis, and five from R. sanguineus s.l. Our work provides the first record of R. felis in hard ticks of Mexico and Central America, with new collection localities for this pathogen in central Mexico.