Population genetics of the Ixodes affinis (Ixodida: Ixodidae) complex in America: new findings and a host-parasite review.

Ticks are hematophagous ectoparasites associated with a wide range of vertebrate hosts. Within this group, the Ixodidae family stands out, in which the Ixodes genus contains at least 245 species worldwide, from which 55 species are present in the Neotropical region. Ixodes affinis, a tick described in 1899, has a wide distribution from the Southern Cone of America to the United States. However, since its description, morphological variability has been reported among its populations. Furthermore, attempts have been made to clarify its status as a species complex using mitochondrial markers, but mainly in restricted populations of South and Central America. Thus, information related to populations of the transition region between the Neotropical and Nearctic zones is lacking. For these reasons, the objectives of the study were to evaluate the genetic diversity and structure of I. affinis across the Americas and to compile all the published records of I. affinis in America, to elucidate the host-parasite relationships and to identify their geographical distribution. For this, a phylogeny, and AMOVA analyses were performed to assess the genetic structure of samples obtained by field work in South Carolina, USA and Yucatán, Mexico. A total of 86 sequences were retrieved from a fragment of the 16S region. Phylogeny and genetic structure analysis showed four groups that were geographically and genetically related with high branch support and Fst values, all of them statistically significant. The results obtained support the hypothesis that I. affinis it corresponds to a complex of four species, which must be validated through future morphological comparisons.

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.

First morphological and molecular report of Lagochilascaris minor (Nematoda, Ascarididae) in a domestic cat from Veracruz, Mexico.

The clinical presentation and the morphological and molecular findings of Lagochilascaris minor in a domestic cat from Veracruz, Mexico are described. In the physical examination of the cat, a fistula with purulent exudate was observed in the ventral middle and left lateral region of the neck, with the presence of nematodes inside. Thirty-two worms were recovered from the lesion, which were identified based on their morphological characteristics as Lagochilascaris spp. To determine the species of the nematode, DNA was extracted from the worms and a fragment of the cytochrome C oxidase subunit 1 was amplified. The product obtained was 100% similar with L. minor from Costa Rica. This is the first morphological and molecular report of L. minor parasitizing a domestic cat from Veracruz, Mexico, and emphasizes the circulation of this zoonotic parasite in the country.

Monitoring the resistance of Rhipicephalus microplus to amitraz, flumethrin, coumaphos, and ivermectin on cattle farms in Mexico.

The prevalence, resistance ratios and factor associated with Rhipicephalu microplus populations resistant to amitraz, flumethrin, coumaphos, and ivermectina (IVM) in Mexico were studied. Field tick populations were collected from 54 farms in 15 different states of Mexico. The dose-response bioassays were carried out using the larval immersion test (amitraz and IVM) and the modified larval packet test (flumethrin and coumaphos) against R. microplus. Mortality data were subjected to probit analysis to calculate lethal concentrations at 50%. A logistic regression model was used to evaluate the relation between resistance and possible associated factors. The phenotype was defined as high resistant (HR), low resistant (LR) or susceptible (S). The overall prevalence of cattle farms with R. microplus resistant to coumaphos, amitraz, flumethrin and IVM were 25.9, 46.2, 31.5 and 68.5%, respectively. For coumaphos, 74.1, 22.2, and 3.7% were classified as S, LR, and HR, respectively, whereas, for amitraz, 53.7, 24.1, and 22.2% of phenotypes were S, LR, and HR, respectively, for flumethrin 68.5, 14.8, and 16.7% were S, LR and HR respectively, and for IVM, 31.5, 46.3, and 22.2% were S, LR, and HR, respectively. We identified that cattle farms without acaricide rotation program (OR: 7.66, CL95%: 1.70-34.47, P: 0.008) had a higher probability of developing R. microplus resistant to amitraz. We concluded that amitraz and IVM resistance in R. microplus is frequent, but mainly at a low level in cattle farms of Mexico. Cattle farms without acaricide rotation program had higher probability of developing R. microplus resistant to amitraz.

Frequency of sheep farms with anthelmintic resistant gastrointestinal nematodes in the Mexican Yucatán peninsula.

The present study explored the frequency of hair-sheep farms with gastrointestinal nematodes (GIN) resistant to albendazole sulfoxide (AS), ivermectin (IVM) and levamisole (LEV) in the Yucatán peninsula, México, using the faecal egg count reduction test (FECRT), and compared the frequency of farms diagnosed with resistance using three different formulae. The survey included farms from the states of Campeche (9) and Yucatán (14) (2016-2019). Collaborating farms had >100 grazing ewes. Animals in the FECRT were > 12 months old, received no anthelmintic for >8 weeks and had ≥150 GIN eggs per gramme of faeces (EPG). Animals were distributed to respective groups: untreated controls, AS (5 mg/kg BW), IVM (0.2 mg/kg BW), and LEV (7.5 mg/kg BW). Due to low EPG, some farms only included one or two AH groups. Second faecal samples were obtained on day 14 post-treatment to estimate the percentage reduction (%R) and 95% confidence interval (95%CI). Criteria to declare resistance were those proposed by the World Association for the Advancement of Veterinary Parasitology. Three formulae were used to estimate resistance frequency: The RESO© and eggCounts-T:C, which considered treated and control EPG means post-treatment, but differed in their 95%CI estimation, while the eggCounts-T:T only considered pre- and post-treatment EPG means with 95%CI. The RESO© and eggCounts-T:C formulae resulted in the same frequency of IVM resistant farms for Campeche (100%; 9/9) and Yucatán (92.9%; 13/14), while, the eggCount-T:T formula resulted in a frequency of 85.7% (12/14) IVM resistance in Yucatán. The three formulae estimated the same frequency of AS resistant farms in Campeche (100%; 9/9) and Yucatán (87.5%; 7/8). The RESO© and the eggCounts-T:C formulae resulted in the same frequency of LEV resistant farms for Campeche (44.4%; 4/9), and Yucatán (60.0%; 6/10), but the eggCounts-T:T formula resulted in a frequency of 40.0% (4/10) LEV resistance in Yucatán. The FECRT using RESO© or eggCounts-T:C formulae are stricter than the eggCounts-T:T as the latter cannot identify what proportion of the %R cannot be attributed to the AH. The untreated control group helped adjusting the %R calculation and seemed more adequate considering the propensity of hair-sheep to reduce their EPG on their own. .

The genus Rickettsia in Mexico: Current knowledge and perspectives.

The genus Rickettsia encompasses 35 valid species of intracellular, coccobacilli bacteria that can infect several eukaryotic taxa, causing multiple emerging and re-emerging diseases worldwide. This work aimed to gather and summarise the current knowledge about the genus Rickettsia in Mexico, updating the taxonomy of the bacteria and their hosts by including all the records available until 2020, to elucidate host-parasite relationships and determine the geographical distribution of each Rickettsia species present in the country. Until now, 14 species of Rickettsia belonging to four groups have been recorded in Mexico. These species have been associated with 26 arthropod species (14 hard ticks, three soft ticks, two sucking lice, and seven fleas) and 17 mammal species distributed over 30 states in Mexico. This work highlights the high biological inventory of rickettsias for Mexico and reinforces the need to approach the study of this group from a One Health perspective.

Ehrlichia canis in dogs of Mexico: Prevalence, incidence, co-infection and factors associated.

Rickettsial infections in dogs of Mexico were investigated. A total of 246 dogs were blood sampled and initially screened to detect Ehrlichia canis, E. chaffeensis, E. ewingii, Anaplasma phagocytophilum and Rickettsia rickettsii by a quantitative real-time PCR (qPCR) assay. Sixty-five dogs were monitored and sampled twice 7-8 months apart. Using the qPCR, 72 positive dogs to E. canis were detected (prevalence of 29.26%). These dogs were also tested by nested PCR to detect the same pathogens. None of the studied dogs were positive to E. chaffeensis, E. ewingii, R. rickettsii nor A. phagocytophilum by both PCR assays. The cumulative incidence of E. canis infection was 38.46%. Sequencing analysis of the nested PCR products revealed 100% and 98.1% identity of E. canis and R. parkeri, respectively. We found a dog co-infected with E. canis and R. parkeri.

Onthophagus landolti and Canthon indigaceus chevrolati (Coleoptera: Scarabaeinae) are attracted to the feces of ivermectin-treated cattle in the Mexican tropics / Onthophagus landolti y Canthon indigaceus chevrolati (Coleoptera: Scarabaeinae) son atraídos por las heces de ganado tratado con ivermectina en el trópico mexicano

Abstract Ivermectin (IVM) is widely used for parasite control in livestock in the tropics. Residual IVM in feces conserves its insecticide activity for weeks and can harm dung beetle (DB) species. Attraction to the feces of IVM-treated cattle was tested using the DB species Onthophagus landolti (Harold) and Canthon indigaceus chevrolati (Harold) as models. Experiments were done under controlled laboratory conditions, semi-controlled field conditions and uncontrolled field conditions. Olfactometers were used in the controlled and semi-controlled trials. The control treatment was baited IVM-free feces, and the experimental treatments were the feces of cattle treated with 1 % IVM (subcutaneous administration; single, 0.2 mg/kg bw dosage) and collected at 5, 14, 21 and 28 days post-treatment. The uncontrolled field trial involved pitfall traps baited with IVM-free feces or feces from IVM-treated cattle collected five days post-treatment. Under controlled and semi-controlled conditions, the feces of IVM-treated cattle (at 5, 14, 21 or 28 days post-treatment) attracted more O. landolti and C. i. chevrolati individuals than IVM-free feces (P < 0.05). The same response occurred under uncontrolled conditions. This clear attraction for IVM-containing cattle feces by the studied DB species highlights that incorrect IVM use may pose a risk to DB communities in cattle production systems.(AU)

Resumen La ivermectina (IVM) es ampliamente utilizada para el control de parásitos en el ganado en los trópicos. La IVM residual en las heces conserva su actividad insecticida durante semanas y puede dañar diversas especies de escarabajos estercoleros. La atracción a las heces del ganado tratado con IVM se probó usando a las especies Onthophagus landolti (Harold) y Canthon indigaceus chevrolati (Harold) como modelos de estudio. Los experimentos se realizaron bajo condiciones de laboratorio controladas, condiciones de campo semicontroladas y condiciones de campo no controladas. Se utilizaron olfatómetros en los ensayos controlados y semicontrolados. El tratamiento de control consistió en heces exentas de IVM, y los tratamientos experimentales fueron heces de ganado tratado con IVM al 1 % (administración subcutánea, dosis única, 0.2 mg / kg pv) las cuales se recogieron a los 5, 14, 21 y 28 días después del tratamiento al ganado. El ensayo de campo no controlado incluyó trampas de caída libre o pitfall cebadas con heces libres de IVM y con heces de ganado tratado con IVM recogido cinco días después del tratamiento. En condiciones controladas y semicontroladas, las heces del ganado tratado con IVM (a los 5, 14, 21 y 28 días después del tratamiento) atrajeron más individuos O. landolti yC. i. chevrolati que las heces sin IVM (P < 0.05). La misma respuesta ocurrió bajo condiciones no controladas. Esta clara atracción a las heces de ganado que contienen IVM por las especies estudiadas pone de relieve que el uso incorrecto de IVM puede plantear un riesgo para las comunidades de escarabajos estercoleros en los sistemas de producción ganadera.(AU)

Ticks infesting dogs in rural communities of Yucatan, Mexico and molecular diagnosis of rickettsial infection.

Rickettsial infection in dog-associated ticks in three rural communities of Yucatan, Mexico was investigated using qPCR and nested PCR assays. A total of 319 dogs were studied and ticks samples were collected. A total of 170 dogs were infested with ticks (frequency of 53.4%). Overall, 1,380 ticks representing seven species were collected: Amblyomma mixtum, A. ovale, A. parvum, A. cf. oblongoguttatum, Ixodes affinis, Rhipicephalus microplus, and R. sanguineus sensu lato. The most abundant species was R. sanguineus s.l. with a mean intensity of 7.4 ticks/host. Dogs in the communities of Chan San Antonio and Yaxcheku were 2.84 and 2.41 times more likely to be infected with R. sanguineus compared with Sucopo (p < 0.05). Adult pools of A. mixtum, A. parvum, I. affinis, R. microplus, and A. c.f. oblongoguttatum were negative to E. chaffeensis, E. ewingii, A. phagocytophilum, and R. rickettsii. However, pools of R. sanguineus s.l. adults and A. ovale adults, as well as nymphs of Amblyomma spp. were positive to E. canis. Sequencing analysis of the nested PCR products amplifying the 16S rRNA gene fragment of E. canis confirmed the results and revealed 100% identity with sequences of E. canis. This is the first report worldwide of E. canis infection in A. ovale by PCR. This finding does not necessarily indicate that A. ovale is a competent vector of E. canis because pathogen transmission of this specific tick to a naïve dog remains to be documented. This study documented that different tick species parasitize dogs in Yucatan, Mexico, where R. sanguineus s.l., A. ovale, and nymphs of Amblyomma spp. were shown to be infected with E. canis. These findings highlight the need for control strategies against tick infestations in dogs to prevent the risk of tick-borne disease transmission among companion animal and probably human populations.

Molecular detection of rickettsial tick-borne agents in white-tailed deer (Odocoileus virginianus yucatanensis), mazama deer (Mazama temama), and the ticks they host in Yucatan, Mexico.

Twenty-five white-tailed deer (Odocoileus virginianus yucatanensis) (WTD), 4 mazama deer (Mazama temama) (MD), and the ticks they host in Yucatan, Mexico were sampled to run a molecular survey for tick-borne rickettsial agents. The prevalence of rickettsial agents was 20% in WTD (5/25) and 50% in MD (2/4). When sequencing the nested PCR products, E. chaffeensis, A. phagocytophilum and A. odocoilei, were identified as single infection or coinfecting cervids. None of the cervid samples were positive for E. ewingii, E. canis, nor Rickettsia spp. Overall, 355 individual ticks were collected. Species identified based on adult stages infesting cervids included Amblyomma mixtum, A. parvum, A. cf. oblongoguttatum, Ixodes affinis, Rhipicephalus microplus, R. sanguineus sensu lato, and Haemaphysalis juxtakochi. Rhipicephalus microplus was the tick species most commonly found infesting cervids with a frequency of 28.4%, and intensity of 25.2 ticks per animal. A pool of Amblyomma cf. oblongoguttatum adults and one of Amblyomma spp. nymphs were positive for E. canis and E. chaffeensis, respectively. None of the studied tick pools were positive for E. ewingii, A. phagocytophilum, nor R. rickettsii. To the best of our knowledge, this study is the first to report the prevalence of rickettsial agents in WTD and MD in Mexico. Our molecular study is the first to report the detection of E. chaffeensis, A. phagocytophilum, and A. odocoilei in MD in Mexico. The molecular detection of E. chaffeensis, A. phagocytophilum, and A. odocoilei in deer, and E. chaffeensis in Amblyomma spp. nymphs reported here raises the concern for the risk of human exposure to tick-borne rickettsial pathogens. Our findings highlight the need to apply the "One Health" approach to study ticks and tick-borne diseases. This science-based information could be used by state public-health programs to assess the risk for exposure to tick-borne Anaplasmataceae in Yucatan, Mexico.

Rhipicephalus (Boophilus) microplus resistant to acaricides and ivermectin in cattle farms of Mexico.

Ticks and the diseases they transmit cause great economic losses to livestock in tropical countries. Non-chemical control alternatives include the use of resistant cattle breeds, biological control and vaccines. However, the most widely used method is the application of different chemical classes of acaricides and macrocyclic lactones. Populations of the cattle tick, Rhipicephalus (Boophilus) microplus, resistant to organophosphates (OP), synthetic pyrethroids (SP), amitraz and fipronil have been reported in Mexico. Macrocyclic lactones are the most sold antiparasitic drug in the Mexican veterinary market. Ivermectin-resistant populations of R. (B.) microplus have been reported in Brazil, Uruguay and especially in Mexico (Veracruz and Yucatan). Although ivermectin resistance levels in R. (B.) microplus from Mexico were generally low in most cases, some field populations of R. (B.) microplus exhibited high levels of ivermectin resistance. The CHPAT population showed a resistance ratio of 10.23 and 79.6 at lethal concentration of 50% and 99%, respectively. Many field populations of R. (B.) microplus are resistant to multiple classes of antiparasitic drugs, including organophosphates (chlorpyrifos, coumaphos and diazinon), pyrethroids (flumethrin, deltamethrin and cypermethrin), amitraz and ivermectin. This paper reports the current status of the resistance of R. (B.) microplus to acaricides, especially ivermectin, in Mexican cattle.

Rhipicephalus (Boophilus) microplus resistant to acaricides and ivermectin in cattle farms of Mexico / Rhipicephalus (Boophilus) microplus resistentes aos acaricidas e ivermectina nas fazendas de gado do México

Ticks and the diseases they transmit cause great economic losses to livestock in tropical countries. Non-chemical control alternatives include the use of resistant cattle breeds, biological control and vaccines. However, the most widely used method is the application of different chemical classes of acaricides and macrocyclic lactones. Populations of the cattle tick, Rhipicephalus (Boophilus) microplus, resistant to organophosphates (OP), synthetic pyrethroids (SP), amitraz and fipronil have been reported in Mexico. Macrocyclic lactones are the most sold antiparasitic drug in the Mexican veterinary market. Ivermectin-resistant populations of R. (B.) microplus have been reported in Brazil, Uruguay and especially in Mexico (Veracruz and Yucatan). Although ivermectin resistance levels in R. (B.) microplus from Mexico were generally low in most cases, some field populations of R. (B.) microplus exhibited high levels of ivermectin resistance. The CHPAT population showed a resistance ratio of 10.23 and 79.6 at lethal concentration of 50% and 99%, respectively. Many field populations of R. (B.) microplus are resistant to multiple classes of antiparasitic drugs, including organophosphates (chlorpyrifos, coumaphos and diazinon), pyrethroids (flumethrin, deltamethrin and cypermethrin), amitraz and ivermectin. This paper reports the current status of the resistance of R. (B.) microplus to acaricides, especially ivermectin, in Mexican cattle.

Carrapatos e as doenças por eles transmitidas causam grandes perdas econômicas ao gado dos países tropicais. Alternativas não-químicas incluem o uso de raças de gado que sejam resistentes, controle biológico e vacinas. No entanto, o método mais utilizado é a aplicação de diferentes classes químicas de acaricidas e lactonas macrocíclicas. Populações de piolhos de gado, Rhipicephalus (Boophilus) microplus, resistentes aos organofosfatos (OP), piretoides sintéticos (SP), amitraz e fipronil, foram descritas no México. Lactonas macrocíclicas são as drogas antiparasitárias mais vendidas no mercado veterinário mexicano. Populações de R. (B.) microplus resistentes à irvemectina foram relatadas no Brasil, Uruguai e especialmente no México (Veracruz e Yucatan). Embora os níveis de resistência à ivermectina no R. (B.) microplus do México tenha sido relativamente baixa, na maioria dos casos, algumas populações campestres de R. (B.) microplus mostraram altos níveis de resistência à ivermectina. A população CHPAT mostrou uma razão de resistência de 10,23 e 79,6 na concentração letal de 50% e 99%, respectivamente. Muitas populações campestres de R. (B.) microplus são resistentes a múltiplas classes de drogas antiparasitárias, incluindo organofosfatos (clorpirifós, coumafos e diazinon), piretoides (flumetrina, deltametrina e cipermetrina), amitraz e ivermectina. Este artigo relata o estado atual de resistência do R. (B.) microplus aos acaricidas, especialmente ivermectina, no gado mexicano.