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The current status of resistance to alpha-cypermethrin, ivermectin, and amitraz of the cattle tick ( Rhipicephalus microplus ) in Ecuador

View Article: PubMed Central - PubMed

ABSTRACT

Rhipicephalus microplus is widely distributed in tropical and subtropical areas of the world where livestock is a principal activity with great veterinary and economic importance. In Ecuador, this hematophagous ectoparasite has been observed between 0 and 2600 masl. One of the main tick control measures is the use of acaricides, which have been indiscriminately used worldwide and in Ecuador. In this country, no studies on acaricide resistance in Rhipicephalus microplus have been published. The current study aims to characterise the level of resistance of R. microplus against three main acaricides commonly used in Ecuador i.e. amitraz, alpha-cypermethrin and ivermectin to determine the level and pattern of dose-responses for R. microplus in 12 field populations (farms). The level of acaricide resistance was evaluated using three different bioassays: adult immersion test (AIT), larval package test (LPT) and larval immersion test (LIT), as recommended by the FAO. The predictive dose-responses were analysed by binomial logistics regression of the larval survival rate (resistance). In general, we found resistance of 67% for amitraz; 50% for alpha-cypermethrin and from 25 to 42% for ivermectin in the twelve field populations analysed. Resistance levels were studied in larval and adult bioassays, respectively, which were slightly modified for this study. For larval bioassays based on corrected mortality i.e. high (above 51%), medium (21–50%) and low (11–20%) resistance, percentages less than 10% were considered as susceptible. For the adult test, two resistance levels were used i.e. high (more than 76%) and medium (51 to 75%) resistance. Percentages lower than 50% were considered as susceptible. In this context, for larval bioassays, amitraz showed 21%, 38% and 8% for high, medium and low resistance, respectively. Alpha-cypermethrin presented 8%, 4 and 38% for high, medium and low resistance, respectively. Ivermectin presented 8%, 25% and 8% for high, medium and low resistance, respectively. For adult tests with amitraz 50% and 17% of the field populations showed average and high resistance, with evidences of average resistance to alpha-cypermethrin in 50% of the samples and average resistance against ivermectin in 25% of the farms. No statistical difference amongst the three bioassays was found and acaricide resistance was confirmed by logistic regression analysis; hence resistance (dose-responses) in each field populations differed, depending on the choice of the acaricide, frequent usage, frequency of treatment and farm management. The effective estimated dose needed to eliminate 99% of ticks is higher than dose recommended by the manufacturer. In conclusion, amitraz showed the highest resistance followed by ivermectin and alpha-cypermethrin and reveals differences on resistance in each individual field population. This information is important in order to establish the monitoring of resistance on each farm individually, contributing to the rational use of acaricides included in an integrated control program for R. microplus.

No MeSH data available.


Study area.Twelve livestock dairy farms distributed in four areas of the coastal area of Ecuador were surveyed. Farm range temperatures between 15 and 35°C and an altitude from 500 to 1,500 masl. Source: MAGAP (2017): http://geoportal.sigtierras.gob.ec:8080/GeoserverViewer/.
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pone.0174652.g001: Study area.Twelve livestock dairy farms distributed in four areas of the coastal area of Ecuador were surveyed. Farm range temperatures between 15 and 35°C and an altitude from 500 to 1,500 masl. Source: MAGAP (2017): http://geoportal.sigtierras.gob.ec:8080/GeoserverViewer/.

Mentions: The study was undertaken on 12 livestock dairy where a field populations were collected from each. The farms are distributed in four areas: three in San Miguel de los Bancos county, three in Pedro Vicente Maldonado county, three in Santo Domingo de los Tsáchilas county and three in El Carmen county. The farms were located in the coastal area of Ecuador with temperatures ranging from 15 to 35°C and an altitude from 200 to 1,500 masl [20] (Fig 1). Ticks were collected on each farm from October to December 2015, following the methods described by Junte in 2008 [21]. Farms were selected based on their history of use of acaricides i.e. different acaricide types, concentration, combinations and application frequencies that were different in each farm. The number of animals with ticks and livestock management systems were also considered. In addition, none or few technical criteria were reported by farmers; hence the conditions to evaluate acaricides resistance was ideal for this study. Each farm was surveyed and geographically referenced with a Garmin GPSmap64®. For this study, no specific permissions were required because ticks a serious problem for farmers and any endangered or protected species were involved.


The current status of resistance to alpha-cypermethrin, ivermectin, and amitraz of the cattle tick ( Rhipicephalus microplus ) in Ecuador
Study area.Twelve livestock dairy farms distributed in four areas of the coastal area of Ecuador were surveyed. Farm range temperatures between 15 and 35°C and an altitude from 500 to 1,500 masl. Source: MAGAP (2017): http://geoportal.sigtierras.gob.ec:8080/GeoserverViewer/.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384665&req=5

pone.0174652.g001: Study area.Twelve livestock dairy farms distributed in four areas of the coastal area of Ecuador were surveyed. Farm range temperatures between 15 and 35°C and an altitude from 500 to 1,500 masl. Source: MAGAP (2017): http://geoportal.sigtierras.gob.ec:8080/GeoserverViewer/.
Mentions: The study was undertaken on 12 livestock dairy where a field populations were collected from each. The farms are distributed in four areas: three in San Miguel de los Bancos county, three in Pedro Vicente Maldonado county, three in Santo Domingo de los Tsáchilas county and three in El Carmen county. The farms were located in the coastal area of Ecuador with temperatures ranging from 15 to 35°C and an altitude from 200 to 1,500 masl [20] (Fig 1). Ticks were collected on each farm from October to December 2015, following the methods described by Junte in 2008 [21]. Farms were selected based on their history of use of acaricides i.e. different acaricide types, concentration, combinations and application frequencies that were different in each farm. The number of animals with ticks and livestock management systems were also considered. In addition, none or few technical criteria were reported by farmers; hence the conditions to evaluate acaricides resistance was ideal for this study. Each farm was surveyed and geographically referenced with a Garmin GPSmap64®. For this study, no specific permissions were required because ticks a serious problem for farmers and any endangered or protected species were involved.

View Article: PubMed Central - PubMed

ABSTRACT

Rhipicephalus microplus is widely distributed in tropical and subtropical areas of the world where livestock is a principal activity with great veterinary and economic importance. In Ecuador, this hematophagous ectoparasite has been observed between 0 and 2600 masl. One of the main tick control measures is the use of acaricides, which have been indiscriminately used worldwide and in Ecuador. In this country, no studies on acaricide resistance in Rhipicephalus microplus have been published. The current study aims to characterise the level of resistance of R. microplus against three main acaricides commonly used in Ecuador i.e. amitraz, alpha-cypermethrin and ivermectin to determine the level and pattern of dose-responses for R. microplus in 12 field populations (farms). The level of acaricide resistance was evaluated using three different bioassays: adult immersion test (AIT), larval package test (LPT) and larval immersion test (LIT), as recommended by the FAO. The predictive dose-responses were analysed by binomial logistics regression of the larval survival rate (resistance). In general, we found resistance of 67% for amitraz; 50% for alpha-cypermethrin and from 25 to 42% for ivermectin in the twelve field populations analysed. Resistance levels were studied in larval and adult bioassays, respectively, which were slightly modified for this study. For larval bioassays based on corrected mortality i.e. high (above 51%), medium (21–50%) and low (11–20%) resistance, percentages less than 10% were considered as susceptible. For the adult test, two resistance levels were used i.e. high (more than 76%) and medium (51 to 75%) resistance. Percentages lower than 50% were considered as susceptible. In this context, for larval bioassays, amitraz showed 21%, 38% and 8% for high, medium and low resistance, respectively. Alpha-cypermethrin presented 8%, 4 and 38% for high, medium and low resistance, respectively. Ivermectin presented 8%, 25% and 8% for high, medium and low resistance, respectively. For adult tests with amitraz 50% and 17% of the field populations showed average and high resistance, with evidences of average resistance to alpha-cypermethrin in 50% of the samples and average resistance against ivermectin in 25% of the farms. No statistical difference amongst the three bioassays was found and acaricide resistance was confirmed by logistic regression analysis; hence resistance (dose-responses) in each field populations differed, depending on the choice of the acaricide, frequent usage, frequency of treatment and farm management. The effective estimated dose needed to eliminate 99% of ticks is higher than dose recommended by the manufacturer. In conclusion, amitraz showed the highest resistance followed by ivermectin and alpha-cypermethrin and reveals differences on resistance in each individual field population. This information is important in order to establish the monitoring of resistance on each farm individually, contributing to the rational use of acaricides included in an integrated control program for R. microplus.

No MeSH data available.