Gastrointestinal nematodes resistant to anthelmintics have been reported in several regions of Brazil, and they may be associated with economic losses for the cattle industry. This study aimed to evaluate the resistance status of gastrointestinal nematodes from naturally infected beef cattle to several commercially available anthelmintics, as well as to test the efficacy of combinations of anthelmintics against multi-resistant gastrointestinal nematodes. Ten farms located in Rio Grande do Sul state were selected by: farmers' consent; extensive raising system; availability of calves aged from 7 to 9 months naturally infected by gastrointestinal nematodes; absence of anthelmintic treatment for 60 days before the study; and presence of 70–100 calves or more of both genders with ≥200 eggs per gram of feces (EPG) (sensitivity of 50 EPG). These calves were distributed into 10 groups (of 7–10 animals) per farm and treated with ivermectin, doramectin, eprinomectin, fenbendazole, closantel, nitroxynil, disophenol, levamisole, albendazole, or moxidectin. Feces were collected 2 days before treatment and 14 days after treatment. Additional groups of 7–10 calves were used to test six different two-drug combinations at four of the studied farms. In general terms, fenbendazole was the most effective drug, followed by levamisole, disophenol, and moxidectin. However, parasite resistance to multiple drugs was found in all herds, especially in the genera Cooperia spp., Trichostrongylus spp., and Haemonchus spp.. Some of the two-drug combinations were effective against nematode populations identified as resistant to the same compounds when used as single drugs. The most effective combinations were moxidectin + levamisole, doramectin + fenbendazole, and levamisole + closantel. In this study, parasites resistant to the main commercially available anthelmintics were found in all herds, and some combinations of two active components belonging to different chemical groups were effective against multi-drug resistant gastrointestinal nematodes.

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Background: Balantidium coli is a commensal protozoan that infects several animals, but it has pigs as its natural reservoir. In the presence of predisposing factors, B. coli can become pathogenic for swine, causing enteric lesions. Infections determined by this protozoan may be a risk to public health, due to dysentery in animal keepers and veterinarians. This study aimed to determine the occurrence of infection by B. coli in pigs of distinct husbandry categories, as well as unlike physiological state, kept in farms with different hygienic-sanitary standards, located in the central region of Rio Grande do Sul State in Brazil.Materials, Methods & Results: Stool samples were collected from 12 different farms with different hygienic-sanitary standards being four farms of finisher pigs (G1; n = 287), four farms with pregnant females (G2; n = 60) and four farms with lactation sows (G3;  n = 40), and all samples were submitted to coproparasitological analyses to verify the presence of cysts or trophozoites of B. coli. The infection levels were considered mild (1-100 cyst/trophozoite), moderate (101300 cyst/trophozoite) and high (>300 cysts/trophozoite). In addition, information about hygienic-sanitary conditions of each farm was collected. The occurrence of B. coli infection in all swine stool samples analyzed was 60.9% (236/387); however, in G1, G2 and G3 was 54.7% (157/287), 91.7% (55/60) and 65% (26/40) respectively. There was significant difference in the occurrence of G1 (P < 0.05) except between farms B and C (67.9% and 56.6% respectively). There was also a significant difference (P < 0.05) between the occurrence of B. coli found in G2 and G3. The infection levels were considered predominantly mild in G1; and mild to moderate in G2 and G3.Discussion: In this research it was confirmed the presence of B. coli in swine farms located in the central region of Rio Grande do Sul State in Brazil. This area is known as being an important producer of pigs in Brazil. The results obtained in this study, demonstrated that swine farms with better hygienic and sanitary standards, had mild infections by B. coli. However, the presence of intestinal parasites, especially protozoa, can occur even in properties with good management practices. However, protozoa infections can cause important production losses, especially when associated with other pathogens or nutritional problems. The occurrence of B. coli observed in pregnant (G2) and lactating (G3) females was significant, and the infection level was mild to moderate. These conditions suggest that pregnancy, childbirth and lactation are critical stages for females, mainly due to physiological stress, resulting in a change in the hormonal levels and immune status of the animals. Thus, these factors cause declines in the immune response of pigs making them susceptible to infections and the increase of cyst excretion of B. coli in feces. The abundance of protozoan cysts in feces contaminates the environment and increases the risk of infections in humans. In addition, it was demonstrated the occurrence of B. coli in an important site of swine production in RS, Brazil. B. coli is related to the physiological state of the animals and the hygienic and sanitary management in different categories of swine. In conclusion, this study highlights the epidemiological importance of swine as natural reservoir of Balantidium coli and the risk potential of infection to animals and humans. Additionally, sanitary program in farming pigs must be improved in order to guarantee healthy and food-safe product for consumers.

Semi-intensive equine breeding system favors gastrointestinal nematode infections. The treatment of these infections is based on the use of anthelmintics. However, the inappropriate use of these drugs has led to parasitic resistance to the available active principles. The objective of this study was to evaluate the efficacy of the main classes of antiparasitic (ATP) used in control in adult and young animals, including: benzimidazoles (fenbendazole), pyrimidines (pyrantel pamoate), macrocyclic lactones (ivermectin and moxidectin), as well as the combination of active ingredients (ivermectin + pyrantel pamoate). The study was carried out in two military establishments, located in Rio Grande do Sul (RS), from January to December, 2018. The intervals between the treatments of the animals were performed from 30 to 90 days. Coproparasitological evaluations were determined by the egg count reduction in the faeces. Cyatostomine larvae were identified in pre and post-treatment cultures. The results demonstrated the multiple parasitic resistance of cyathostomins to fenbendazole, moxidectin in young animals, and to fenbendazole, pyrantel pamoate in adult animals. Thus, it is necessary to define or diagnose parasitic resistance to assist in the creation of prophylactic parasitic control, using suppressive treatment with ATP associated with integrated alternatives. The progress of parasitic resistance can be slowed.

Given the numerous reports of anthelminthic resistance of sheep nematodes to different anthelmintic compounds, this study aimed to evaluate the resistance status of gastrointestinal nematodes from naturally infected sheep to monepantel in the state of Rio Grande do Sul. Four farms that present extensive raising system and absence of anthelmintic treatment for 60 days were selected for the study. Lambs that present counts of eggs per gram of feces (EPG) ≥200 (sensitivity of 50 EPG) one day (D-1) before the treatment were select for the study and randomly separated into two groups, a control group and an experimental group treated with monepantel. Feces were collected 9 days after the treatment (D+9) for EPG counts and fecal culture. The monepantel was 100% effective only on 2. The efficacy found on farm 1, 3, and 4 were 2.82%, 25.8%, and 78.4%, respectably. There were no viable larvae post-treatment at farm 2, but the genera Haemonchus, Trichostrongylus, Cooperia, and Strongyloides were resistant to it at the other farms. This study shows the presence of parasites resistant to the treatment with monepantel, pointing to the importance of monitoring its efficacy in sheep flocks of Rio Grande do Sul, Brazil.

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Considering the importance of Haemonchus contortus infection in herds along with parasitic resistance, the goal of this study was to evaluate the influence of the administration of adjuvants alone or in combination with anthelmintics for the treatment of H. contortus, in experimentally infected sheep. Thirty sheep of the Texel breed of both genders, raised in a herd located in the subtropical region of Brazil, were used in this experiment. Experimental infection with H. contortus was performed in sheep, and the infected sheep were then separated into groups for the administration of antiparasitic and immunostimulant drugs. The results obtained from the excretion of eggs per gram of feces and the count of parasites during necropsy affirm that the use of adjuvants in combination with anthelmintics is associated with higher efficacy of treatment, lower rate of reinfection, and retardation in the development of anthelmintic drug resistance by H. contortus. Based on these results, we can conclude that the combination of anthelmintics and immunostimulants may favor potential anthelmintic treatments for H. contortus.

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