[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: 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, farm management, and anti-tick vaccines. Chemical acaricides have played an essential role, and are used traditionally to control infestations in livestock, but intensive acaricide use has enabled the emergence of tick populations resistant to them. Populations of the cattle tick, Rhipicephalus microplus, single and multiresistant to organophosphates (OP), synthetic pyrethroids (SP), amitraz and fipronil have been reported worldwide including Mexico. Macrocyclic lactones (MLs) have been used to mitigate the negative effects of ticks, including tick populations resistant to other acaricides. In Mexico, the pharmaceutical industry reported from 2007 to 2009 that MLs are the most used antiparasitic drugs in ruminants (45-50% of the total market). In the MLs family, ivermectin is the most commonly used followed by moxidectin and doramectin. Ivermectin-resistant populations of R. microplus have been reported in Brazil, Uruguay and especially in Mexico (Veracruz and Yucatan). Although ivermectin resistance levels in R. microplus from Mexico were generally low in most cases, some field populations of R. microplus exhibited high levels of ivermectin resistance. Some tick populations exhibited a resistance ratio >10 at the lethal concentration of 50% and 99%. CONCLUSIONS: Worldwide, many field populations of R. microplus are resistant to multiple classes of antiparasitic drugs, including OPs, SPs, fipronil, amitraz and ivermectin. Ivermectin-resistant populations of R. microplus have been reported in Latin America, especially in Mexico. Although ivermectin resistance levels in R. microplus from Mexico were generally low in most cases, some field populations of R. microplus exhibited high levels of ivermectin resistance. Strategies involving the early detection of resistance and the use of integrated tick control are recommended.
[Show abstract][Hide abstract] ABSTRACT: The prevalence of fleas and gastrointestinal parasites in free-roaming and domestic cats in central Mexico was evaluated. Three hundred and fifty eight cats captured in the street or brought in by owners to the Animal Control Center Unit, a unit of State Government, from June 2010 to May 2011, were included in the study. All cats were examined for the presence of fleas and gastrointestinal worms. One-hundred and ninety (53%) cats were infested with at least one flea species. Single infestations were observed in 106 (30%) cats and mixed infestations in 84 (23%) cats. Four species of fleas were recovered: Ctenocephalides felis in 53% of the cats, C. canis in 18%, Echidnophaga gallinacea in 7% and Pulex irritans in 1%. One-hundred and sixty three (45%) cats were infected with one or more species of gastrointestinal parasites: 48 (13%) with nematodes, 145 (40%) with cestodes, and one animal presented Moniliformis moniliformis. Prevalences and mean intensity of infection were: Physaloptera praeputialis 7 and 18; T. cati 3 and 2; Ancylostoma tubaeforme 2.5 and 2; Toxascaris leonina 0.5 and 2; Dipylidium caninum 36 and 32; Taenia taeniformis 4 and 3 and Moniliformis moniliformis 0.3 and 106, respectively. There was significant association (P<0.01), between season and ectoparasites load, more fleas were obtained in the summer and autumn than in the winter and spring; however, no statistical difference was observed for endoparasites load (P>0.05). The correlation between the total number of ectoparasites and endoparasites was not significant (r = 0.089, P = 0.094).
[Show abstract][Hide abstract] ABSTRACT: Babesiosis is a disease with a world-wide distribution affecting many species of mammals principally cattle and man. The major impact occurs in the cattle industry where bovine babesiosis has had a huge economic effect due to loss of meat and beef production of infected animals and death. Nowadays to those costs there must be added the high cost of tick control, disease detection, prevention and treatment. In almost a century and a quarter since the first report of the disease, the truth is: there is no a safe and efficient vaccine available, there are limited chemotherapeutic choices and few low-cost, reliable and fast detection methods. Detection and treatment of babesiosis are important tools to control babesiosis. Microscopy detection methods are still the cheapest and fastest methods used to identify Babesia parasites although their sensitivity and specificity are limited. Newer immunological methods are being developed and they offer faster, more sensitive and more specific options to conventional methods, although the direct immunological diagnoses of parasite antigens in host tissues are still missing. Detection methods based on nucleic acid identification and their amplification are the most sensitive and reliable techniques available today; importantly, most of those methodologies were developed before the genomics and bioinformatics era, which leaves ample room for optimization. For years, babesiosis treatment has been based on the use of very few drugs like imidocarb or diminazene aceturate. Recently, several pharmacological compounds were developed and evaluated, offering new options to control the disease. With the complete sequence of the Babesia bovis genome and the B. bigemina genome project in progress, the post-genomic era brings a new light on the development of diagnosis methods and new chemotherapy targets. In this review, we will present the current advances in detection and treatment of babesiosis in cattle and other animals, with additional reference to several apicomplexan parasites.
Full-text · Article · Feb 2012 · Current Medicinal Chemistry
[Show abstract][Hide abstract] ABSTRACT: Dialelic crosses and backcrosses of pyrethroid resistant (RR) and susceptible (SS) Rhipicephalus (Boophilus) microplus tick strains were carried out and the substitution (Phe-Ile) within the sodium channel gene was monitored in order to analyze the effects of the genotype on the pyrethroid resistance phenotype as measured by the larval packet test (LPT). Parental strains: susceptible (SS) and resistant (RR); dialelic crosses: RS (♂RR × ♀SS), and SR (♂SS × ♀RR); and backcrosses: RS × SS, RS × RR, SR × SS and SR × RR were infested on 280 kg calves. Resistance type (monogenic or polygenic) and effective dominance were determined based on the discriminant concentration (DC) for cipermethrine (0.5%), deltamethrine (0.09%) and flumethrine (0.01%). Allele specific PCR (AS-PCR) was used for genotyping, looking at a sodium channel mutation (Phe-Ile substitution). The mortality rates and allele frequency of susceptible and pyrethroid resistant reference strains were 0% mortality and 90% RR alleles for resistant strain, and 100% mortality and 0% RR alleles as measured by the larval packet test (LPT) and allele specific PCR (AS-PCR) respectively. Backcrossed strain SR × RR showed an effective dominance (D(ML)) of 0.605 for cypermethrin, 0.639 for deltamethrin and 0.498 for flumethrin, while survival of backcrosses RS × SS, RS × RR and SR × SS showed a significant tendency to recesivity. Backcrossed strain SR × RR (69.4%) also showed a higher RR genotype frequency with regards to RS × SS (25.5%), RS × RR (36.7%) and SR × SS (32.0%), however, susceptible allele was inherited in general as an incomplete dominant trait. Monogenic inheritance hypothesis was tested and the results showed monogenic inheritance for cypermethrin and flumethrin (P < 0.05) but not for deltamethrin (P > 0.05). However, significant correlation was found between RR genotype and the survival rate for all three pyrethroids used (P < 0.05), suggesting that a single substitution on the sodium channel gene can be responsible for resistance to pyrethroids as a class, due to the high frequency for RR genotypes. Combination with different mutations or metabolic resistance mechanisms cannot be excluded.
Full-text · Article · Mar 2011 · Experimental and Applied Acarology
[Show abstract][Hide abstract] ABSTRACT: A substitution (Phe→Ile) within the sodium channel gene sequence has been associated with pyrethroid resistance in Boophilus microplus. The aim of the present study was to analyze the inheritance of pyrethroid resistance and the mutant allele, on reciprocal crosses of a susceptible (SS) and a resistant (RR) strain. Bioassays and genotypes were determined to evaluate pyrethroid resistance. The resistance allele frequency of both parental strains were 100% and 2.27% for RR and SS, respectively. The reciprocal crosses show a predominance of the heterozygote genotype, in agreement with the significant decrease of the acaricide resistance to cypermethrin, deltamethrin, and flumethrin. However, the RS progeny showed a complete recessive survival (D
ML = 0) for deltamethrin and flumethrin, suggesting a complete dominance of the susceptible allele and incomplete dominance for cypermethrin (D
ML = 0.169). On the other hand, SR progeny showed a partially recessive survival for cypermethrin (D
ML = 0.380), deltamethrin (D
ML = 0.319), and flumethrin (D
ML = 0.258), indicative of a partially dominant inheritance of the resistance. A possible maternal strain effect should be considered for practical purposes and prediction of acaricide resistance and further work needs to be done to elucidate the underlying inheritance of pyrethroid resistance and the sodium channel mutation in B. microplus.
Full-text · Article · Aug 2008 · Parasitology Research
[Show abstract][Hide abstract] ABSTRACT: The study was divided in to two trials and carried out in a ranch in eastern Yucatan state, Mexico. In the first trial, two groups of 15 BostaurusxBosindicus heifers, 6-12 month of age and naturally infested with Boophilus microplus ticks were used. Heifers in Group 1 were treated with a 1% injectable formulation of moxidectin at the dose of 0.20mg/kg body weight by subcutaneous injection. The other group remained as untreated controls. Number of immature and engorging female ticks were assessed on days 0, 7, 14, 21, 28 and 35 post-treatment (PT). The efficacy of moxidectin on adult ticks from day 7 to 28 PT was greater than 95%. The efficacy decreased to 74.9% by day 35. In the second trial, animals in Group 1 were treated with the moxidectin product as before, while cattle in Group 2 were treated according to the routine procedure for the control of ticks on that property (125 g/l amitraz as a dip). Treatment of all cattle was repeated four times at intervals of 28 days. The efficacy of the experimental moxidectin treatment was similar to that of the routine amitraz treatment, i.e., greater than 99%.
Full-text · Article · Mar 2003 · Veterinary Parasitology