Use of anti-tick drugs in dairy farms in the microregion of Alfenas, Minas Gerais, Brazil

Braz J Vet Parasitol 2021; 30(1): e020620 | https://doi.org/10.1590/S1984-29612021016 This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Use of anti-tick drugs in dairy farms in the microregion of Alfenas, Minas Gerais, Brazil


Introduction
Minas Gerais, a state located in Southeastern Brazil, has the largest milk production in the country. During the first trimester of 2019, the state processed 1,566,954 liters of this product, leading the milk purchase ranking from dairy companies (EMBRAPA, 2019).
In order to obtain greater production, it is necessary to control the environmental factors that might negatively affect the herd. The infestation by ectoparasites determines a greater reduction in the productive indexes since, in addition to poor weight gain, milk production and animal welfare, it transmits pathogens that increase the occurrence of diseases (Fraga et al. 2003;Pereira & Labruna, 2008).
The cattle tick, Rhipicephalus (Boophilus) microplus, is responsible for an annual economic impact of 3.24 billion dollars in Brazil, and for 2.7% reduction in the milk production of Minas Gerais (Grisi et al., 2014;Rodrigues & Leite, 2013). Rhipicephalus (Boophilus) microplus can be found mainly in areas of tropical climate, and is a one-host parasite. The cycle happens in two different phases: the non-parasitic phase occurs when the engorged female detaches from the host, falls and starts laying eggs. The parasitic phase takes place when the young ticks are already in their parasitic phase and consequently attach themselves to the host.
The comprehension of this biological cycle is important for the accomplishment of an effective and strategical control of the ticks. However, research carried out in Brazil showed that the majority of producers have no knowledge of this cycle, fomenting the indiscriminate and unregulated use of antiparasitic drugs (EMBRAPA, 2003;Veríssimo et al., 2016), or few know the form of strategic control and none use it correctly (Rocha et al., 2006).
Brazil has registered 380 different veterinary products in Ministry of Agriculture, Livestock and Food Supply (MAPA) used to combat ticks, formulated with 15 active ingredients from 9 different chemical classes (SIDAN, 2017). This fact can make it difficult for the producer to choose a new product. There is little technical knowledge available, both on the part of the producers and the clerks of agricultural houses, in order to know, at the time of choice, the differences in the forms of action of the products that enable them to make the right decision (Furlong et al., 2007). The indiscriminate rotation without criteria of products can favor the selection of individuals tolerant to all these products and, in this situation, the resistance process can be underway (Furlong et al., 2007).
Knowledge of practices adopted in the tick control properties is important to help the researcher design more viable control methods and to assist the producer in the introduction of these methodologies in the field (Bertolucci, 2011), as done by Jonsson & Matschoss (1998) and the Dairy TickCON program in Australia, encouraging producers to adopt methods that minimize the use of chemicals and maximize their effectiveness.
The production factor can positively influence the control of Rhipicephalus (Boophilus) microplus. Less productive properties with less educated owners were where ticks were found with more frequency, promoting greater pressure for the selection of resistant ticks (Rocha et al., 2006).
The growing phenomenon of resistance to the active ingredients used and the presence of residues in milk or meat are some of the most important and damaging aspects resulting from the use of acaricides on a larger scale (Fraga et al., 2003;Veríssimo et al., 2016). Thus, the aim of this study was to understand the perception of milk producers of three scaled-productions of the micro region of Alfenas, Minas Gerais (Brazil) about the use of acaricides.

Material and Methods
The experiment was carried out in the micro region of Alfenas, south of the State of Minas Gerais, Brazil ( Figure 1). The micro region is formed by 12 cities (Alfenas, Alterosa, Areado, Carmo do Rio Claro, Carvalhópolis, Conceição da Aparecida, Divisa Nova, Fama, Machado, Paraguaçu, Poço Fundo and Serrania). In the region, there are 4,313 milk producing establishments and a bovine herd of 40,871 milk cows (IBGE, 2017).
The information was obtained through semi-structured questionnaires ( Figure 2) applied in-person to 100 owners of dairy establishments. All procedures involving humans were approved by the Research Ethics Committee of UNIFENAS (protocol number 2746625, Plataforma Brazil). Prior to the application of the questionnaires, the participants signed the Free and Informed Consent Term and the research was classified as low risk (Resolution 196/96).
The selection of milk producing establishments was carried out by simple occasional sampling in the defined region independent of daily production scale. Property names were omitted.  To analyze the influence of the production scale by the management of ectoparasites, the 100 milk producing establishments were allocated to one of the three production strata: small, medium and large, characterized by daily milk production of less than 151 kg, from 151 to 400 kg and over 400 kg, respectively, as proposed by Lopes et al. (2006).
The producers were questioned about the total number of cattle, number of lactating cows, average daily production and animal productivity. Regarding the management of ectoparasites, the type of drug used on their cattle was elevated (accepting more than one answer). The application form questions the effectiveness of the chosen treatment, if they changed the active ingredient frequently, handling the tick and the person responsible for the indication of the active ingredient. When the commercial name was mentioned, the package insert was consulted to confirm the active ingredient mentioned in the medication formula to catalog the data. In addition, they were also questioned about any knowledge of the "withdrawal period" of the medication they were using and the instructions on the package insert were followed.
Out of the evaluated population of 4,313 establishments, 100 were sampled at random, that is, 2.3% of the population. The open responses were categorized through content analysis (Minayo, 1993), thus, each question was transformed into a variable, mostly nominal qualitative. Subsequently, descriptive statistical analysis using frequency (Gil, 1991) was performed and a chi-square test was done to assess the influence of the production scale. Anova analysis of variance was performed for the productive variables (number of cows, milk production and productivity), with Tukey's test at 5% probability.

Results
The survey participants were owners responsible for 100 milk producing establishments, 39% of which were small-scale (up to 151 liters / day); 24 medium-scale production (151 to 400 liters/day) and 37 produced more than 400 liters per day, classified as large-scale production. On average, the herds had 150 cows (Median = 70, SD = 277.5), with an average of 50 lactating animals (Median = 25; SD = 86.6). The average daily production was 973.7 liters (Median = 225; SD = 2278.3 liters), while productivity was 13.1 liters per cow per day (Median = 10, SD = 7.4 liters per cow per day).
There was a statistical difference (P> 0.01) between the establishments evaluated for the variables of total cows, lactating cows, daily production and animal productivity ( Table 1), which is related to the production scale. Large-scale production properties showed, on average, a higher number of cows (292), lactating cows (109) and, consequently, higher milk production (2443.5 liters / day) and productivity (20.9 liters / cow / day) when comparing small scale properties (66 cows, 8 in lactation, 58.1 liters / day and 7.2 liters / cow / day) and medium scale productions (71 cows, 25 in lactation, 256.5 liters / day and 10.7 liters / cow / day) that did not differ.
Of the 100 (one hundred) dairy farms that answered the questionnaire, all of them used at least one or more types of tick medicament products and 129 active ingredient responses were obtained ( Table 1). The most used acaricides were a mixture of Cypermethrin + Chlorpyrifos + Citronellal 31% (n = 40), followed by Fluazuron 18.6% (n = 24), Fipronil 17% (n = 22) and Amitrax 10.8% (n=14) ( Table 2). The production scale did not interfere with the choice Table 1. Profile of milk producing establishments participating in the survey in relation to the scale of milk production (small up to 151 liters / day; averages 151 to 400 liters and large production greater than 400 liters/day).  of the medication used (P = 0.229). As for the "withdrawal period", 15% of milk producers answered that they did not have knowledge of the "withdrawal period" of tick medicament used in their dairy herd and 9% answered that they did not use tick medication products according to the dose manufacturer's recommendations (Table 3), small-scale producers are the ones who least consult the package insert for the medication (P = 0.02).

Variable
The variables choice of acaricides, problems with the use of acaricides, use of the recommended dose, change of acaricides and use of personal protective equipment (PPE) during application were influenced by the production scale (P <0.05) according to the chi-square test ( Table 3).
The veterinary recommendation is the main reason for choosing acaricides in 46.2% (n = 18) of small-scale properties and 73% (n = 27) of large-scale properties. 41.7% (n = 10) of the medium-scale production properties choose acaricides based on recommendations of friends or relatives.
The moment of application most used in the 100 properties is during the infestation (n = 47), and in 36 establishments the application is made in lots and the acaricide is applied to the whole body (n = 46) or pour-on (n = 44).
The answers related to the problems with the use of acaricides was influenced by the production scale (P = 0.017). 78.4% (n = 29) of the respondents of large-scale properties reported that resistance was the main problem. Differently, 56.4% (n = 22) of the owners of small-scale establishments responded that they had no problems.
Of the 100 milk producers, 73 said they had already changed their active ingredient, with large-scale producers having changed the most, 89.2% (n = 33).
The production scale influenced (P = 0.016) the response on the use of PPE. The majority of respondents (41/100) stated that they used incomplete PPE at the time of application of the acaricide, followed by those who claimed (31/100) that they did not use any equipment and only 28 establishments made complete use of PPE, 14 of which were of large-scale production, 8 medium and 6 small-scale. The majority of small-scale production owners, 48.7% (n = 19) responded that they did not use any PPE equipment.

Discussion
Although the properties participating in the study differed in cattle numbers, production and productivity, due to their production scales (Table 1), they showed to be above the average in productivity indexes of the State of Minas Gerais of 5.9 liters per cow per day (IBGE, 2017).
The higher productivity observed in large-scale production properties (20.9 liters per cow per day), compared to small scales (7.2 liters per cow per day), may be related to genetics and animal management. In this study, the producers were not asked about the genetics of the dairy cattle, but the hypothesis is that the cattle of large producers consist of a greater degree of animals of European blood, Holstein, which are animals of higher production by lactation. Factor that may also have influenced low tick resistance. According to Miranda & Freitas (2009), the choice of the genetic resource is related to the milk production system. Properties with high milk production per lactation (> 8,000 kg) use specialized European breeds, properties with average productivity (3,500 to 6,000 kg / lactation) use crossbred breeds, triple crossbreeding, and properties with milk production below 3,500 kg per lactation use breeds with greater zebu blood.
Some studies show that dairy B. taurus x B. indicus crosses, mainly Girolando cows, prevail in Minas Gerais dairy farms (Madalena et al., 2012;Embrapa, 2019). Crossbreeding has been used to generate cows that would combine the high milk production capacity of Holsteins and the adaptability to tropical conditions of the Gyr breed (Stafuzza et al., 2017).
About the tick resistance, Lemos et al. (1985), when studying and natural infestations in heifers of different genetic groups, which ranged from ¼ Holstein x Zebu to pure Holstein, a higher parasitic load as the proportion of Holstein genes increased was observed, making this additive effect significant and evidencing the lower resistance of the European breed.
Other factors to consider to increase productivity, according to Faria & Corsi (1993), are rational use of labor, improvement in reproduction rates, improvement in feed efficiency and improvement in the health status of the herd. Within sanitary management, parasitosis is worth mentioning, which can cause indirect losses, expenses with control, direct losses, decrease in the production and transmission of diseases, which affects animal productivity (Bertolucci, 2011).
Currently, six classes of acaricides can be easily found to purchase in the Brazilian market: phenylprazoles (fipronil), organophosphates, formamidines (amitraz), synthetic pyrethroids, macrocyclic lactones and benzoylphenylureas (fluazuron). The indiscriminate use of acaricides to promote tick control might generate resistant strains of Rhipicephalus (Boophilus) microplus, and it is already mentioned in some studies in Brazil and the world (Leal et al., 2003;Li et al., 2007;Mendes et al., 2011;Fernández-Salas et al., 2012;Miller et al., 2013;Rodríguez-Vivas et al., 2014). The occurrence of resistant ticks leads to an increase of commercialized products that contain two or more compounds in its formulations (Reck et al., 2014).
When asked which acaricide was used on the property, being able to quote more than one product, most milk producers (31%, 40/129) responded to using products with more than one active ingredient (Cypermethrin + Chlorpyrifos + Citronella) in their composition ( Table 2). The pyrethroid-organophosphate association increase efficiency against populations of Rhipicephalus (Boophilus) microplus. Santana (2000) observed higher mean efficiencies of such associated compounds, compared to isolated pyrethrins. Rodrigues et al. (2018) when using a product composed of cypermethrin (15 g) + chlorpyrifos (25 g) + citronellal (1 g), observed an average efficacy of 35% in Brangus animals and 51% in Nelore cows. Higa et al., (2019) evaluated the effectiveness of the association cypermethrin + chlorpyrifos + piperonylbutoxide, observed a reduction in the number of ticks parasitizing Brangus cows after application. According to Campos & Oliveira (2005), despite the fact that organophosphates are older products and with reports of resistance worldwide, this chemical group associated with pyrethroids can be used effectively, if a functioning tick management program is implemented.
In addition, cypermethrin (pyrethroid) is an active ingredient that can be found in 81 veterinary products. Its use can result in milk residues; therefore, the withdrawal period must be of at least 14 days (Bastos et al., 2011;Hernandes et al., 2009). However, 15% (15/100) of milk producers affirmed they weren't aware of the "withdrawal period" of tick medication products they used (Table 3), which can lead to an increase in drug residues in milk.
Fluazuron has been in the market since 1994 and the first case of resistance occurred in 2014 (Yessinou et al., 2016). Additionally, this is a lipophilic drug that demands milk fat as an excretion route, resulting in high levels of residues in milk. For this reason, the use of fluazuron is not allowed in lactating or gestational cows in their last trimester (Bull et al., 1996;de Oliveira et al., 2013;Reck et al., 2014).
Other drugs that have active ingredients with milk as an excretion route were mentioned in this study. The avermectins (ivermectin, abamectin, doramectin and eprinomectin) belong to the macrocyclic lactones group, and other than accumulate in milk, they can also be responsible for changes in dairy products, since its base might generally interfere with microrganisms (Whelan et al., 2010).
Fipronil, belonging to the Phenylpyrazoles class (Le Faouder et al., 2007), shows affinity to fat. Spagnol et al. (2010) confirmed that fipronil had greater effectiveness in properties in Itamaraju (Bahia), and the authors justified the high efficiency due to the cost and the fact that its use is prohibited in lactating cows.
Of the 100 milk producers, 73 said they had already switched active ingredients, with 89.2% (33/37) of large-scale producers, 65.2% (16/24) of medium-scale and 61.5% (24/39) of small-scale productions. 68.4% of those who have already replied that the reason for the change was because of a drop in product efficiency. This results may be related to the genetics of the animals used in the properties, since how many the resistance or susceptibility of these animals is dependent on the proportion of European genes (Lemos et al., 1985) and in high-productivity properties the proportion of Holstein genes increased (Miranda & Freitas, 2009).
The indiscriminate manner of changing products without criteria favors the selection of resistant tick populations to all active principle. The accelerated development of resistance to an active principle is a problem that has caused great concern in society and government agencies (Leal et al., 2003). In the present work, resistance was the problem pointed out by 61% (61/100) of the interviewed milk producers, mainly large-scale producers ( Table 3).
Most producers of small-scale properties (56.4%) stated that they had no problem with the use of acaricides. This answer may be related to the degree of understanding about the mechanism by which the loss of efficiency of tick products occurs and the occurrence of resistance, with little technical knowledge on the part of the producer. Rocha et al. (2006) pointed out the lack of knowledge of the way in which acaricides act by producers in the south of Minas Gerais. In another study, it was observed that properties with low production and productivity demonstrated that they did not have the necessary knowledge to improve the control of ticks or their importance (Rocha, 1995).
One way to improve herd resistance is to through the selection of resistant cattle, since the heritability estimates indicate that the selection for resistance to the parasite can be highly efficient. Therefore, the selection of resistant cattle as a tick control strategy will enable the earlier and punctual identification of genetically superior animals (Biegelmeyer et al., 2012) According to Andreotti et al. (2019), for more efficient control, some aspects must be considered, among which include: the knowledge of the tick's life cycle and its relationship with variations in environmental conditions. The population dynamics, especially seasonality, is crucial to identify when the tick population is at the most vulnerable stage to carry out treatments with acaricides. European gene level of the animals should also be considered, associated with the type and management of pasture as well as the stocking rate and system.
The choice of acaricides was influenced by the scale of production. 73% (27/39) of properties with a production greater than 400 liters per day chose their product by the hand of a veterinarian. 41.7% (10/24) of medium-scale properties take into account the indication of friends or relatives and 41% (16/37) of the small-scale properties choose the acaricide by indication of friends, relatives or by the low cost (Table 3). This data corroborates with Rocha (1995) about the lower importance given to the control of ticks by lower production properties.
What determined the timing of application in 47% (47/100) of dairy farms was the degree of tick infestation, a practice inconsistent with the technical criteria for reducing resistance. According to EMBRAPA (2000) the application of acaricides at the time of infestation favors the high frequency of tick baths, which select and propagate the resistance allele by selection pressure. Rocha et al. (2006) observed that less productive properties were where acaricides were applied more frequently, promoting greater pressure from resistant ticks.
Other inappropriate practices of the use of acaricides can also favor the appearance of resistance in the populations of Rhipicephalus (Boophilus) microplus (Rocha et al., 2006). The use of doses can be classified as inappropriate without meeting the manufacturer's recommendation, being the response of 9% (9/100) of the owners. A difference was observed for the scale of production in this variable, where 20.5% (8/37) of the small-scale properties did not use the recommended dose in the package insert, which reinforces the conclusions of Bertolucci (2011) that in the properties of South Minas Gerais, the control of tick occurs empirically. In addition, this data is worrying, because along with resistance, it can increase residues in milk (Rocha et al., 2006).
The moderate use of acaricides should be a practice on the properties, the solutions should be prepared with the amount of acaricides indicated on the package insert, which should be added to a small amount of water (syrupy liquid), so after the necessary volume of water is added to complete the total amount of the solution to be prepared (Furlong et al., 2007). It is very important to always read the package insert and follow the manufacturer's recommendations.
Acaricides are toxic products that act mainly on the central nervous system, causing allergies, intoxications, organ malformations and tumor growth (Furlong et al., 2007). Thus, the use of PPE (overalls or plastic cover, mask, boots and gloves) is essential at the time of application. In the present study, it was found that only 28% (28/100) of the properties use complete PPE, and 41% (41/100) used some PPE at the time of application, with the glove being the most cited PPE (33%). Small-scale production properties differed in response, being 48.7% (19/39) of respondents said they did not use any PPE during the application of the acaricide. The hypothesis for this difference is that in small-scale properties there are few workers, and the person responsible for the application becomes familiar with the activity, believing that the use of PPE is not necessary. According to Furlong et al. (2007), when the employee frequently has contact with the product, they tend to decrease the care needed when handling these toxic substances. Santos et al. (2000) observed an excessive and inefficient use of chemical acaricide to control Rhipicephalus (Boophilus) microplus during their research, leading to risks of contamination of the environment, poisoning and development of resistant tick strains. The author emphasizes the need for convincing campaigns to implement strategic control measures, including operator safety with the use of PPE's.
When asked about their knowledge of other forms of tick control, 83% (83/100) of the interviewees said they knew about it, the most cited being the vaccine and pour-on products. No producer cited biological control or strategic control. Demonstrating more than a decade of the study by Rocha et al. (2006), the conclusions are the same; few producers in South Minas Gerais are aware of strategic tick control or biological control.
The grace periods for each product for later use of milk must be respected to ensure food security. The efficiency of the acaricide used on an annual basis or whenever suspected of failures should be assessed using samples of adult ticks (engorged females -teleogens) and sent to prepared laboratories. In Brazil, there is a network of accredited laboratories that routinely perform in vitro sensitivity profile of dairy cattle ticks to commercial acaricides. This practice leads to a reduction in animal stress and labor costs, environmental preservation and minimizing residues in products derived from treated animals, increasing quality and adding value to them. The delay in the resistance process ensures longer use of the few chemical bases available (Andreotti et al., 2019).

Conclusions
The majority of milk producers interviewed in the present study used antiparasitic drugs with restricted use in lactating dairy cows because it presented a more effective control against ectoparasites.
Small-scale production properties promote empirical practices of using acaricides, favoring the appearance of resistance, residues in milk products and practices that put the health of the worker at risk. However, all the properties, regardless of the scale of production, demonstrated that they did not adopt technical criteria for the control of ticks, had little information on other forms of control and were unconcern with the use of inappropriate acaricides and worker safety.
In order to revert this antiparasitic drug's resistance situation and contamination of milk with drug residues, it is necessary to focus on the awareness of milk producers and training of labor.