Genetic structure analysis of Amblyomma mixtum populations in Veracruz State, Mexico

Abstract

Amblyomma mixtum Koch, 1844 parasitizes livestock, humans, and wildlife in Mexico. However, information on population genetics for this tick species in the country is missing. Tick samples were collected from livestock in ten regions across the state of Veracruz (22°28'N, 17°09'S, 93°36'E, 98°39'W) to analyze the genetic structure of A. mixtum populations. Ticks were morphologically identified using taxonomic keys. In order to test the intra-specific variability of A. mixtum fragments of the mitochondrial gene 16S-rRNA and cytochrome oxidase subunit 1 (COI) were amplified. Ninety-six sequences were amplified from the 50 specimens' analyzed (96% amplification success). Eleven haplotypes were detected in 16S-rRNA gene and 10 more for COI. Neutrality tests showed negative results in most of the locations analyzed, which is indicative of an excess of recently derived haplotypes. However, these results were not statistically significant. Minimal union network analysis revealed that there is no separation of populations by geography, and that there is an overlap of several haplotypes among diverse populations. Significant genetic differentiation was not detected in the A. mixtum populations sampled in the state of Veracruz, Mexico, this may be due to the frequent movement of livestock hosts. This is the first report on the genetic structure of A. mixtum populations in Mexico.

Morphometrics of Amblyomma mixtum in the State of Veracruz, Mexico

“…Results of the morphometric analyses confirmed that the only species from the A. cajennense complex parasiting cattle in Veracruz state, Mexico is A. mixtum . This is in agreement with results from previous studies on the reinstatement of A. mixtum as a valid species and the documentation of its geographic range [ 7 , 15 , 17 ]. It is important to understand the actual distribution of A. mixtum because of its relevance in veterinary medicine and public health as an ectoparasite and vector of tick-borne pathogens [ 6 , 18 ].…”

“…Intraspecific morphological variation was not detected in the male and female A. mixtum analyzed in this study. This seemingly homogenous phenotype may reflect the lack of genetic separation between A. mixtum populations across the natural regions of Veracruz state [ 15 ]. Although it can inhabit diverse ecosystems in Mexico parasitizing multiple vertebrate host species [ 8 , 23 , 24 ], similar morphometric characteristics were detected in adult A. mixtum .…”

“…The indiscriminate use of acaricides is a major driver for the emergence of acaricide resistance among populations of A. mixtum infesting livestock in Veracruz state [ 14 ]. This is concerning because evidence for the emergence of resistance to multiple classes of acaricides is in this three-host tick species even when gene flow associated with lack of genetic differentiation was documented for A. mixtum populations in the same region [ 15 ]. However, studies to determine if morphological variation among A. mixtum population in Veracruz state remained to be conducted.…”

Entomopathogenic Fungi for Tick Control in Cattle Livestock From Mexico

“…Currently, it seems that A. mixtum has a greater distribution, since this species has been able to adapt to various ecological niches, including semi-arid grasslands and subtropical secondary forests (Estrada-Peña et al, 2004); in addition to its great capacity to occupy the ecological niches of other ticks (i.e., R. microplus under high pressure from acaricides) (Alonso- Díaz et al, 2013b). This ectoparasite has a heteroxenous life cycle and is a generalist species that infests livestock, humans and, wildlife in Mexico (Aguilar-Domínguez et al, 2019;Higa et al, 2020). It causes economic losses due to the large amount of blood taken from its hosts and the transmission of infectious diseases to domestic/wild animals (Anaplasma marginale) and humans (Rickettsia ricketsii) (Alonso- Díaz et al, 2013b;Aguilar-Domínguez et al, 2019).…”

“…This ectoparasite has a heteroxenous life cycle and is a generalist species that infests livestock, humans and, wildlife in Mexico (Aguilar-Domínguez et al, 2019;Higa et al, 2020). It causes economic losses due to the large amount of blood taken from its hosts and the transmission of infectious diseases to domestic/wild animals (Anaplasma marginale) and humans (Rickettsia ricketsii) (Alonso- Díaz et al, 2013b;Aguilar-Domínguez et al, 2019). Additionally, other potentially zoonotic species such as Rickettsia amblyommatis have been detected in A. mixtum from Mexico (Sánchez-Montes et al, 2016;Merino et al, 2020), making this parasite one of the most important tick species in veterinary medicine and public health in the country (Pérez de León et al, 2020).…”