Control of Rhipicephalus microplus tick larvae in the field based on distancing from the host - Lone tick system.

The aim of this study was to evaluate a host-tick distancing control system using Rhipicephalus microplus in cattle. Its impact on the profiles of the pathogens Anaplasma marginale and Babesia bigemina was also assessed using enzyme-linked immunosorbent and real-time polymerase chain reaction. Experiments were conducted in Mato Grosso do Sul, Brazil. A total of 37 Senepol animals with natural tick infestation were used in this study. The ticks on the animals were counted, and pasture rotation was performed at 28-day intervals. This approach was repeated until the end of the experiment to maintain a low number of ticks, resulting in a final average of 6.3 ticks/host. Cattle maintained an immune response to the cattle tick fever (CTF) agents. DNA copies of A. marginale (X̄ 1.1) and B. bigemina (X̄ 0.05) did not vary significantly with the decrease in tick count throughout the study period. Based on these results, we conclude that a distancing period of 84 days between ticks and cattle in conditions of the Cerrado biome can control ticks in animals and maintain enzootic stability. Thus, it is possible to create productive breeds with lower tick control costs.

Seasonal fluctuations of Babesia bigemina and Rhipicephalus microplus in Brangus and Nellore cattle reared in the Cerrado biome, Brazil.

BACKGROUND: The tick Rhipicephalus microplus (Ixodida: Ixodidae, Canestrini, 1888) causes substantial economic and health losses in cattle production and is the main vector of Babesia bigemina (Piroplasmidae: Babesidae, Smith & Kilborne, 1893). Babesia bigemina is responsible for a tick-borne disease known as babesiosis that can cause hemolytic anemia, fever and death. In the study reported here, we investigated the relationship between the number of ticks per animal and the number of B. bigemina cytochrome b gene (cbisg) copies in the blood of Brangus and Nellore cattle reared without acaricidal treatment in the Brazilian Cerrado biome over a 1-year period. METHODS: Ticks on 19 animals (9 Brangus and 10 Nellore cattle) were counted every 18 days, and blood was collected every 36 days for 12 months. Serological samples were analyzed with an indirect enzyme-linked immunosorbent assay, and genomic DNA was analyzed by conventional PCR and quantitative PCR. The PCR products were sequenced by the Sanger method. RESULTS: The Brangus and Nellore breeds showed similar weight development and no clinical signs of babesiosis. Statistically significant differences (P < 0.05) between the breeds were observed for the number of ticks and the number of B. bigemina cbisg gene copies. CONCLUSIONS: No correlation between the number of ticks and the number of circulating copies of cbisg was observed, although Nellore cattle presented with fewer ticks than Brangus cattle and the number of cbisg copies was higher for Nellore cattle than for Brangus cattle.

Control Strategies for the Tick Rhipicephalus Microplus (Canestrini, 1888) on Cattle: Economic Evaluation and Report of a Multidrug-Resistant Strain.

PURPOSE: The aim of this study was to evaluate four strategies for application of acaricides to control the tick Rhipicephalus microplus among infested cattle, and to show which of these has the best cost-benefit ratio. METHODS: For this, 72 cattle were selected and divided into four groups: Group 1 (G1): fipronil, pour-on; Group 2 (G2): fluazuron, pour-on; Group 3 (G3): moxidectin, injectable; and Group 4 (G4): chlorpyrifos 30 g, cypermethrin 15 g and fenthion 15 g, spraying (atomizing chamber). Every seven days, the numbers of semi-engorged females were counted and laboratory tests were conducted using different commercial technical-grade products for resistance monitoring. RESULTS: G4 showed the best percentage reduction, with the highest rate on the seventh day post-treatment (DPT) (83.23%). G3 was the second best strategy, with a percentage of inverse reduction such that the best results were on the 28th DPT (82.85%), while G1 and G2 reached their best results on the 21st DPT (32.63% and 2.79%). CONCLUSION: It was noteworthy that the formulation used in G4 was the only one that was efficient for strategic control and that, based on the economic analysis, was shown to be economically viable over the medium term due to the need for investment. The presence of a multidrug-resistant strain in the state of Mato Grosso do Sul in vitro, for the chemical bases amitraz, cypermethrin and cypermethrin + DDVP, is reported here for the first time.

Effect of low temperature and relative humidity on reproduction and survival of the tick Rhipicephalus microplus.

The objective of this study was to evaluate the survival of Rhipicephalus microplus females under low temperature, to determine the influence of temperature and relative humidity (RH) on the biological parameters of this tick. In total 300 viable engorged female ticks collected from cattle were used. On the day of collection (D0), 30 female ticks were divided into three groups: G1, kept at 28 °C and 80% RH; G2, kept at 20 °C and 80% RH; and G3, kept at 20 °C and 30% RH. The remaining females were stored in a refrigerator at 4 °C. Over the next 9 days (D+1 to D+9), 30 female ticks were removed daily from the refrigerator and distributed among the three treatments. Egg mass, feed conversion rate, egg incubation period, larval hatch rate, number of dead females per group, weight of female tick removed from the refrigerator, and female tick weight loss were recorded. At 20 °C and 80% RH hatching was delayed. Among the female ticks kept in the refrigerator and then allocated to groups G1, G2, and G3, there was a reduction in reproductive efficiency and a rise in mortality as time in the refrigerator increased. The female ticks expressed their best reproductive capacity when subjected to the refrigeration temperature for a maximum of 3 days and then kept at 28 °C and 80% RH. Thus, although female ticks can be stored in the refrigerator before being sent to research centers for use in bioassays, the storage time should be as short as possible, not exceeding 3 days.

Serological evaluation of Neospora caninum in pregnant women treated at referral center for prenatal screening in Mato Grosso do Sul, Brazil.

Neospora caninum is an obligate intracellular protozoan with canids (Canis domesticus, Canis lupus dingo, Canis latrans, Canis lupus) as its definitive hosts. The objective of this study was to detect anti-N. caninum antibodies in pregnant women seen at referral center for prenatal screening in the state of state Mato Grosso do Sul, Brazil. A total of 188 serum samples from pregnant women provided by the Instituto de Pesquisa, Ensino e Diagnósticos da APAE de Campo Grande (IPED/ APAE) were subjected to IFA test and western blot analysis. The samples were divided into three groups: 23/99 samples from the seropositive group for toxoplasmosis were positive for anti-N. caninum IgG antibodies, and 9/99 positive for IgM; in the HIV group, 7/33 were positive for IgG; and in the HIV+toxoplasmosis group, 13/56 were positive for IgG and two positive for IgM. The seropositivity for IgG was assessed by western blot by testing 43 IFA test positive samples using rNcSRS2 (Nc-p43) as antigen. The serological results of the present study suggest that exposure of these pregnant women to the parasite N. caninum and presence of IgM antibodies are indicative of recent infection. Further studies are needed to establish the possibility of active infection.

Correlation between Rhipicephalus microplus ticks and Anaplasma marginale infection in various cattle breeds in Brazil.

The tick Rhipicephalus microplus is responsible for the transmission of Anaplasma marginale, which causes hemolytic anemia, abortion, decreased production, and mortality in cattle in Brazil. However, A. marginale can also persist in cattle herds without any clinical signs. This study investigated the relationship between the number of ticks present on each cattle and the circulating number of A. marginale msp1ß gene copies in the blood of Brangus and Nellore cattle reared in the Brazilian Cerrado through a year period. Twenty-three animals (11 Brangus and 12 Nellore) were raised for 12 months with ticks counted every 18 days, and blood collected every 36 days. Blood sera was used for total antigen iELISA, genomic DNA was extracted from whole blood by the phenol/chloroform method and then analyzed by PCR to confirm A. marginale presence with the msp5 gene. Positive samples were quantified by qPCR using msp1ß gene. Brangus cattle presented 4.5 fold more ticks than Nellore group. Although Brangus cattle carried a higher overall A. marginale msp1ß gene presence than Nellore cattle, no relationship of tick count and copy number could be achieved due to high variability in copy number. Moreover, both breeds showed similar weight gain and a similar serological pattern throughout the year. None of the animals showed any clinical signs of anaplasmosis during the experimental period, indicating that a low level of tick infestation may be sufficient to maintain a stable enzootic situation.

Spotted fever group Rickettsia and Borrelia sp. cooccurrence in Amblyomma sculptum in the Midwest region of Brazil.

More than 70 tick species are found in Brazil, distributed over five genera and including main vectors of infectious disease agents affecting both animals and humans. The genus Amblyomma is the most relevant for public health in Brazil, wherein Amblyomma aureolatum, Amblyomma ovale and Amblyomma sculptum have been incriminated as vectors of Rickettsia and Borrelia pathogens. The objective of this study was to investigate the presence of Rickettsia spp. and Borrelia spp. in ticks in the Brazilian mid-western savannah. DNA extraction, PCR for Borrelia spp. (flgE gene) and Rickettsia spp. (ompA and gltA genes) and subsequent sequencing were performed. A total of 1875 ticks were collected and identified as A. sculptum except for two Amblyomma coelebs ticks. Molecular evidence for Borrelia spp. and Rickettsia parkeri was found in A. sculptum. This is the first molecular evidence for R. parkeri in A. sculptum ticks in the Midwest region and Borrelia spp. circulating in a tick of the Amblyomma genus in Brazil.

Serological and molecular detection of Neospora caninum and Toxoplasma gondii in human umbilical cord blood and placental tissue samples.

Neosporosis primarily affects cattle and dogs and is not currently considered a zoonotic disease. Toxoplasmosis is a zoonosis with a worldwide distribution that is asymptomatic in most cases, but when acquired during pregnancy, it can have serious consequences. The seropositivity rates determined by the indirect fluorescent antibody test for Neospora caninum (N. caninum) and Toxoplasma gondii (T. gondii) were 24.3% (49 samples) and 26.8% (54 samples), respectively. PCR positivity for N. caninum was observed in two samples of cord blood (1%) using the Nc5 and ITS1 gene, positivity for T. gondii was observed in 16 samples using the primer for the B1 gene (5.5% positivity in cord blood and 2.5% positivity in placental tissue). None of the samples showed structures characteristic of tissue cysts or inflammatory infiltrate on histopathology. Significant associations were observed only between N. caninum seropositivity and the presence of domestic animals (p = 0.039) and presence of dogs (p = 0.038) and between T. gondii seropositivity and basic sanitation (p = 0.04). This study obtained important findings regarding the seroprevalence and molecular detection of N. caninum and T. gondii in pregnant women; however, more studies are necessary to establish a correlation between risk factors and infection.

Evidence of acaricide resistance in different life stages of Amblyomma mixtum and Rhipicephalus microplus (Acari: Ixodidae) collected from the same farm in the state of Veracruz, Mexico.

The objectives of this study were to evaluate the resistance of Amblyomma mixtum and Rhipicephalus microplus ticks from co-infested bovines from the Veracruz region in Mexico to different acaricide families and to demonstrate the viability of the packet test on different A. mixtum instars. The following acaricide families were used: a combination (cypermethrin 15 g + chlorpyrifos 25 g + citronella 1 g + butoxide piperonyl 15 g), amidine (formamidine 12.5 g), pyrethroid (cypermethrin 15 g), and organophosphate (dichlorvos 60 g + chlorpyrifos 20 g). Regarding the packet test in both species, resistance was found for the pyrethroid and amidine families in A. mixtum and R. microplus, as efficacy did not surpass 40 %, including in immature instars; regarding the adult immersion test in R. microplus, the efficacy was 93.3 % for the amidine family and 26.2 % for the pyrethroid family. The proposed methodology is an alternative technique to optimize resistance detection in immature ticks with a heteroxenous life cycle.

Serological evaluation of Neospora caninum in pregnant women treated at referral center for prenatal screening in Mato Grosso do Sul, Brazil / Avaliação sorológica de Neospora caninum em gestantes atendidas em centro de referência para triagem pré-natal em Mato Grosso do Sul, Brasil

Abstract Neospora caninum is an obligate intracellular protozoan with canids (Canis domesticus, Canis lupus dingo, Canis latrans, Canis lupus) as its definitive hosts. The objective of this study was to detect anti-N. caninum antibodies in pregnant women seen at referral center for prenatal screening in the state of state Mato Grosso do Sul, Brazil. A total of 188 serum samples from pregnant women provided by the Instituto de Pesquisa, Ensino e Diagnósticos da APAE de Campo Grande (IPED/ APAE) were subjected to IFA test and western blot analysis. The samples were divided into three groups: 23/99 samples from the seropositive group for toxoplasmosis were positive for anti-N. caninum IgG antibodies, and 9/99 positive for IgM; in the HIV group, 7/33 were positive for IgG; and in the HIV+toxoplasmosis group, 13/56 were positive for IgG and two positive for IgM. The seropositivity for IgG was assessed by western blot by testing 43 IFA test positive samples using rNcSRS2 (Nc-p43) as antigen. The serological results of the present study suggest that exposure of these pregnant women to the parasite N. caninum and presence of IgM antibodies are indicative of recent infection. Further studies are needed to establish the possibility of active infection.

Resumo Neospora caninum é um protozoário intracelular obrigatório que possui os canídeos (Canis domesticus, Canis lupus dingo, Canis latrans, Canis lupus) como seus hospedeiros definitivos. O objetivo deste trabalho foi detectar anticorpos anti-N. caninum em gestantes, atendidas em centro de referência para triagem pré-natal, em Mato Grosso do Sul, Brasil. Um total de 188 amostras de soro de gestantes, cedidas pelo Instituto de Pesquisa, Ensino e Diagnósticos da APAE de Campo Grande (IPED/ APAE), foram submetidas ao teste de RIFI e western blot para a detecção de anticorpos anti-N. caninum. As amostras foram divididas em três grupos: 23/99 amostras do grupo soropositivo para toxoplasmose demonstraram positividade para anticorpos IgG anti-N. caninum e 9/99 positivos para IgM. No grupo HIV 7/33 apresentaram positividade para IgG. No grupo HIV+Toxoplasmose 13/56 apresentaram positividade para IgG e duas para IgM. A soropositividade para IgG foi avaliada por western blot, testando 43 amostras positivas para RIFI, usando-se rNcSRS2 (Nc-p43) como antígeno. Os resultados sorológicos do presente estudo sugerem exposição dessas gestantes ao parasita N. caninum e a positividade para anticorpos IgM são indicativos de infecção recente. Mais estudos na área são necessários para estabelecer a possibilidade de infecção ativa.

Economic efficiency of Rhipicephalus microplus control and effect on beef cattle performance in the Brazilian Cerrado.

The cattle tick Rhipicephalus microplus causes significant economic losses to cattle production systems and is a main barrier to the introduction of Bos taurus breeds and their crosses in Brazil. These breeds have the genetic potential to generate animals that are more productive, but they are also more susceptible to R. microplus. One of the alternatives for conventional tick control is the use of strategic control, aiming at delaying or even preventing the development of its resistance to acaricides. The present study aimed to evaluate the economic losses caused by tick infestation on the productive performance of two breeds of beef cattle and to evaluate the economic efficiency of tick strategic control and its impacts on beef cattle production systems. Animal weights were obtained from the literature and were used to calculate the weight loss in kilograms (kg) and the economic loss (US$) caused by R. microplus infestation. The cost/loss ratio of performing strategic control was also calculated. The data show that tick infestation causes economic losses to the breeds and groups of animals evaluated and reduces animal performance (weight loss). The results show a loss of US$34.61/animal in the backgrounding phase and US$7.97/animal in the finishing phase for Brangus animals and its crosses. In conclusion, the data show that strategic control is economically efficient for Brangus animals in the backgrounding phase, independent of the methods used for acaricide application.

Economic performance evaluation of Brangus and Nellore cattle breed naturally infested with Rhipicephalus microplus in an extensive production system in Central-West Brazil.

The objective of the present study was to evaluate the performance of Brangus and Nellore cattle in an extensive production system. Sixty growing bulls, 30 of the Brangus and 30 of the Nellore breeds that were naturally infested with Rhipicephalus microplus were subdivided into four groups: control Nellore (15 animals), treated Nellore (15), control Brangus (15), and treated Brangus (15). The animals in the treated groups underwent acaricidal treatments for 1 year. Tick counts, acaricidal treatments and animal weighing were performed every 18 days, and the costs of acaricidal, anti-myiasis, and preventive treatments for tick fever were recorded for cost evaluation. The treated Brangus and Nellore groups did not show a significant difference in weight gain, whereas Nellore weight gain was superior in the control groups. The cost of acaricidal treatment throughout the experimental period was $494 US. The costs of the preventive treatment for tick fever and myiasis were $98 US and $15 US, respectively. The highest rates of tick infestation were found in the control group of the Brangus animals, which served as the basis for the suggested implementation of a strategic control program for animals in the growth phase. Nellore animals showed low rates of infestation. Under the conditions of this study, the Nellore animals were more efficient than the Brangus animals because they achieved satisfactory weight gain, similar to the Brangus, and a low tick count even in the control group. This finding demonstrates that expenses related to the acaricidal, anti-myiasis and tick fever treatments are unnecessary in Nellore cattle, making these animals more profitable.

Free-living ticks in a cerrado fragment, state of Mato Grosso do Sul, Brazil / Carrapatos de vida livre em fragmento de cerrado, no Estado de Mato Grosso do Sul, Brasil

The fatal cases of spotted fever reported in some Brazilian municipalities are generally associated with the presence of ticks and capybaras (Hydrochoerus hydrochaeris). The urban forest fragments where this rodent is present are of great concern. We investigated the diversity of free ticks as well as the occurrence of ticks infected by Rickettsia in one of these fragments, in Campo Grande city, Mato Grosso do Sul state, Brazil. From winter 2012 until the autumn of 2015, using CO2 traps, we collect 1219 ticks, of which 1045 belonged to the species Amblyomma sculptum and 174 belonged to A. dubitatum. Both species were more abundant in spring (September to December) and summer (December to March). Rickettsial DNA was not detected in any of the specimens collected; however, one of the species found, A. sculptum is considered the main vector of Brazilian Spotted Fever, thus deserving constant vigilance by the public health organs.

Casos fatais de febre maculosa que foram relatados em alguns municípios brasileiros geralmente estão associados à presença de carrapatos e capivaras (Hydrochoerus hydrochaeris). Os fragmentos florestais urbanos onde este roedor está presente são de grande preocupação. Investigou-se aqui a diversidade de carrapatos livres e a ocorrência de carrapatos infectados por riquétsias em um desses fragmentos em Campo Grande, Mato Grosso do Sul. Desde o inverno de 2012 até o outono de 2015, usando armadilhas de CO2, foram coletados 1219 carrapatos, dos quais 1045 pertenciam à espécie Amblyomma sculptum e 174 pertenciam a A. dubitatum. Ambas as espécies foram mais abundantes na primavera (Setembro a Dezembro) e no verão (Dezembro a Março) . O DNA riquetsial não foi detectado em nenhum dos espécimes coletados; entretanto, uma das espécies encontradas, o A. sculptum é considerado o principal vetor da Febre Maculosa Brasileira, merecendo assim vigilância constante pelos Orgãos de Saúde Pública.

Efficacy profile of Cypermethrin and Chlorpyrifos based acaricides on Rhipicephalus microplus control on cattle in the rearing phase, naturally infested and exposed to tick fever agents in central Brazil.

The objective of this work was to evaluate the efficacy of two cypermethrin- and chlorpyrifos-based acaricides in controlling Rhipicephalus microplus in a naturally infested bovine herd and in in vitro tests, as well as to monitor the animals for tick fever. Male bovines in the rearing phase were used, with 30 Brangus and 30 Nellore animals naturally infested. The groups were composed as follows: 15 Nellore treated, 15 Nellore control, 15 Brangus treated and 15 Brangus control. Every 18 days, the animals were monitored for tick count, acaricide treatment, weight, blood pack cell volume, and clinical signs. For in vitro tests, the larval packet test, adult immersion test and DNA amplification for tick fever diagnosis were performed. In the first animal treatment period, product 1 (cypermethrin, 15 g + chlorpyrifos, 25 g + citronellal, 1 g) was used; in the second period, product 2 (cypermethrin, 15 g + chlorpyrifos, 30 g + fenthion, 15 g) was used. In Brangus animals, the mean efficacy was 35.1% and 95.8% in the first and second periods, respectively, for the same animals. For Nellore animals, the efficacy in periods one and two was 51% and 97.1%, respectively. The in vitro results showed efficacy above 95% for the two challenged acaricides. The Brangus animals showed a high production of ticks associated with the presence of tick fever agents, which could generate risks for the disease's enzootic stability.

Life cycle of Amblyomma mixtum (Acari: Ixodidae) parasitizing different hosts under laboratory conditions.

Amblyomma mixtum is a tick species in the Amblyomma cajennense complex. The known geographic range of A. mixtum extends from Texas in the USA to western Ecuador and some islands in the Caribbean. Amblyomma mixtum is a vector of disease agents of veterinary and public health importance. The objective of this study was to describe the life cycle of A. mixtum under laboratory conditions. Bovines, rabbits and sheep were infested with larvae, nymphs, and adult ticks under controlled conditions to assess several biological parameters. Eggs, larvae, nymphs and adults were kept in an incubator (27 °C temperature and 80% relative humidity) when they were off the host. The average life cycle of A. mixtum was 88 and 79 days when fed on rabbits and cattle, respectively. Sheep were found to be unsuitable because no ticks attached. The rabbit is a more practical host to maintain a colony of A. mixtum under laboratory conditions. The data from this study can be considered as an example for the life cycle of A. mixtum. However, caution must be exercised when making comparisons to the biology of A. mixtum in its natural habitat.

Life cycle and parasitic competence of Dermacentor nitens Neumann, 1897 (Acari: Ixodidae) on different animal species.

The objective of this study was to evaluate the life cycle and parasitic competence of Dermacentor nitens (Neumann, 1897) on different animal species. Experimental infestations were induced in five specimens each of seven species of possible hosts: rabbits, horses, sheep, cows, guinea pigs, birds and dogs. Rabbits were infested in the ear using artificial feeding chambers, and the horses, sheep, cows and dogs were infested in the ear without feeding chambers. For the infestation of guinea pigs, artificial feeding chambers were fixed on the back. Birds were infested by placing larvae on the back and under the wings without the use of chambers. All animals were inspected daily until the end of the parasitic phase (when the engorged females detached). The average period of engorgement was 25.1days on a horse, with larvae requiring 8days and nymphs 9days to reach engorgement; the average weight of engorged females was 271.4mg; the average weight of egg batches produced was 159.3mg, and the feed conversion rate was 56.8%. On rabbits, the average engorgement period was 27.6days, larvae and nymphs reached engorgement after 7.4 and 11days, respectively, the average weight of an engorged female was 108.4mg and the egg mass was 30.6mg. The feed conversion rate on rabbits was 30%. Cows, sheep, guinea pigs, dogs and birds were not competent hosts, since no engorged females were recovered. Rabbits, when artificially infested, can be used as an alternative host for the maintenance of these ticks in the laboratory. The parasitic specificity of D. nitens for horses was demonstrated in this study.

Evaluation of Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) resistance to different acaricide formulations using samples from Brazilian properties.

The Rhipicephalus (Boophilus) microplus tick is responsible for considerable economic losses in Brazil, causing leather damage, weight loss and reduced milk production in cattle and results in the transmission of pathogens. Currently, the main method for controlling this tick is using acaricides, but their indiscriminate use is one of the major causes of resistance dissemination. In this study, the adult immersion test (AIT) was used to evaluate resistance in ticks from 28 properties located in five different states (Mato Grosso do Sul, Mato Grosso, Ceará, São Paulo, e Minas Gerais) and the Distrito Federal (DF) of Brazil. The resistance was found in 47.64% of the repetitions demonstrating an efficacy of less than 90% in various locations throughout the country. The larvae packet test was used to evaluate samples from ten properties in four states (Mato Grosso do Sul, Mato Grosso, Minas Gerais and Espírito Santo). Spray products belonging to the main classes of acaricides, including combination formulations, were used in both types of test. New cases of resistance were found on properties within the states of Ceará, Espírito Santo and Mato Grosso, where such resistance was not previously reported.

Evaluation of Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) resistance to different acaricide formulations using samples from Brazilian properties / Avaliação da resistência de Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) a diferentes formulações acaricidas utilizando amostras de propriedades brasileiras

Abstract The Rhipicephalus (Boophilus) microplus tick is responsible for considerable economic losses in Brazil, causing leather damage, weight loss and reduced milk production in cattle and results in the transmission of pathogens. Currently, the main method for controlling this tick is using acaricides, but their indiscriminate use is one of the major causes of resistance dissemination. In this study, the adult immersion test (AIT) was used to evaluate resistance in ticks from 28 properties located in five different states (Mato Grosso do Sul, Mato Grosso, Ceará, São Paulo, e Minas Gerais) and the Distrito Federal (DF) of Brazil. The resistance was found in 47.64% of the repetitions demonstrating an efficacy of less than 90% in various locations throughout the country. The larvae packet test was used to evaluate samples from ten properties in four states (Mato Grosso do Sul, Mato Grosso, Minas Gerais and Espírito Santo). Spray products belonging to the main classes of acaricides, including combination formulations, were used in both types of test. New cases of resistance were found on properties within the states of Ceará, Espírito Santo and Mato Grosso, where such resistance was not previously reported.

Resumo O carrapato Rhipicephalus (Boophilus) microplus é responsável por consideráveis perdas econômicas no Brasil, causando, nos bovinos, danos ao couro, perda de peso, redução na produção de leite, o que resulta na transmissão também de patógenos. Atualmente, o principal método de controle para esse carrapato é o uso de acaricidas, porém seu uso indiscriminado é uma das principais causas da disseminação da resistência. Neste estudo, o teste de imersão de adultos (TIA) foi utilizado para avaliar a resistência em carrapatos provenientes de 28 propriedades, localizadas em cinco diferentes estados brasileiros (Mato Grosso do Sul, Mato Grosso, Ceará, São Paulo, e Minas Gerais) e no Distrito Federal (DF). A resistência foi encontrada em 47,64% das repetições, demonstrando uma eficácia de menos de 90% em vários lugares do país. O teste de pacote de larva foi utilizado para avaliar amostras de 10 propriedades em quatro estados (Mato Grosso do Sul, Mato Grosso, Minas Gerais e Espírito Santo). Produtos de pulverização, pertencentes às principais classes de acaricidas, incluindo-se associações, foram utilizados em ambos os testes. Novos casos de resistência foram encontrados em propriedades nos estados do Ceará, Espírito Santo e Mato Grosso, nas quais a resistência ainda não havia sido previamente reportada.

Formula to evaluate efficacy of vaccines and systemic substances against three-host ticks.

The control of ticks with vaccines is of global interest. Experimental vaccines incorporate new technologies as soon as they are available. Historically, the main vaccine studies have focused on the one-host cattle tick Rhipicephalus microplus, and efficacy evaluations have been standardised for this tick species. On the other hand, evaluations of vaccine candidates for three-host ticks are being done somewhat arbitrarily and thus comparisons within the current literature on the efficacy of vaccines, as well as other methods of control, are difficult. We herein provide a formula for the evaluation of efficacy of a vaccine designed against three-host ticks that incorporates the whole life cycle of the tick.

Contributions of the hair sheep breed Santa Ines as a maintenance host for Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) in Brazil.

BACKGROUND: Hair sheep breeds are a new, cost-effective option for the diversification of livestock in the Midwest region of Brazil. They are grazed extensively with cattle as well as in isolation in small areas. Hair sheep breeds are vulnerable to infestation by parasites such as the cattle tick, Rhipicephalus microplus, which causes various types of damage and can transmit diseases. METHODS: In this study, Santa Inês hair sheep were naturally infested in an area contaminated by infested cattle and then monitored to determine the ability of these animals to maintain the local tick population in the absence of cattle. After engorged tick females of each generation fell off, the animals were placed in another pasture and were returned only after larvae reappeared in the original pasture. RESULTS: Tick counts were performed every ten days for three generations of sheep, and average infestations per animal of 34, 12 and 4 ticks were observed for each successive generation. These numbers suggest the acquisition of resistance; however, additional studies are needed to ensure resistance is achieved. The average length of the parasitic phase for each generation of ticks was 25 days. CONCLUSION: We concluded that this hair sheep breed, even if kept separate from cattle, is able to maintain tick populations for at least three generations, although a gradual decrease in the population levels of R. microplus over three generations was observed. We also detected two positive cases of Anaplasma spp. Therefore, it appears that the Santa Inês hair sheep breed contributes to the circulation of this bacterium among other ruminants.