Detection of ectoparasites and investigation of infection by Rickettsia spp. and Trypanosoma spp. in bats from Rio Grande do Sul, Brazil.

This study aimed to investigate the presence of ectoparasites and the occurrence of natural infection by Rickettsia spp. and Trypanosoma spp. in bats from Rio Grande do Sul (RS), Brazil. The evaluated animals were obtained from the Instituto de Pesquisas Veterinárias Desidério Finamor, sent by the Centro Estadual de Vigilância Sanitária, to carry out rabies diagnostic tests, during the period from 2016 to 2021. The bats came from 34 municipalities in RS. Of the 109 animals surveyed, 35.8% (39/109) had 385 ectoparasites, with an average of 9.9 parasites per animal. Of these bats, all had insectivorous feeding habits, with 35.9% (14/39) females and 64.1% (25/39) males. The co-parasitism of Chirnyssoides sp., Ewingana inaequalis, and Chiroptonyssus robustipes on Molossus currentium (Mammalia, Chiroptera) was recorded for the first time. All bats surveyed were negative for infection by the protozoan and bacteria. Thus, the expansion of the occurrence of these ectoparasites in insectivorous bats in RS was observed. Furthermore, this study corresponds to the first recorded interspecific associations for the species.

Antimicrobial activity of cationic water-soluble porphyrin against multidrug-resistant bacteria in biofilms and canine skin samples.

Multidrug-resistant (MDR) microorganisms pose a threat to animal health, particularly in integumentary diseases, which can be caused by multiple organisms and often manifest as biofilms, hindering treatment effectiveness. We evaluated the antimicrobial activity of antimicrobial photodynamic therapy (aPDT) using a water-soluble tetra-cationic porphyrin (4-H2TMeP) against MDR bacteria cultured in biofilm and in mono and polyculture grown on canine skin samples. We utilized 4-H2TMeP porphyrin against MDR Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus pseudintermedius. A non-cytotoxic concentration of 4-H2TMeP (40 µM), previously shown to be effective in vitro against these bacteria cultured in solution, was employed. Biofilms were treated with 4-H2TMeP and subjected to light irradiation for 30, 60, and 90 min. Monocultures on canine skin samples were treated with 4-H2TMeP and irradiated for 30 (S. pseudintermedius), 60 (E. coli), or 60 and 90 min (P. aeruginosa). Polycultures of S. pseudintermedius and E. coli were treated with light for 60 and 90 min. The efficacy of aPDT was evaluated by plating light-exposed biofilms, mono and polycultures of bacteria obtained from skin samples exposed to light and kept in the dark. Colony-forming units were counted after 24 h of incubation at 37 °C. aPDT using 4-H2TMeP reduced bacterial concentrations of S. pseudintermedius and E. coli biofilms. Additionally, it significantly reduced bacterial concentrations cultivated on skin samples, with a particular emphasis on S. pseudintermedius. These findings indicate that aPDT with 4-H2TMeP is a promising alternative treatment against MDR bacteria in animal skin infections and should be further explored through in vivo research.

Economic losses caused by mastitis and the influence of climate variation on the occurrence of the disease in a dairy cattle farm in southern Brazil.

This study evaluated the economic impacts caused by mastitis in a small dairy farm with similar characteristics and production to most dairy farms in southern Brazil and investigated if climatic variations influenced mastitis occurrence in the region. A farm with, on average, 45 lactating Holstein cattle was monitored from November 2021 to October 2022, and data on mastitis cases, bulk tank milk somatic cell count, animal treatment costs, milk production, animal disposal costs, and production losses were collected. Monthly averages of temperature, relative humidity (RH), and rainfall in the region were obtained. The greatest loss was related to the drop in milk production, resulting in 63.8% of total losses, followed by animal disposal (29.5%), milk disposal (4.6%), and treating animals with mastitis (2.0%), totaling a 10.6% reduction in the annual gross income. There were negative correlations between the clinical mastitis rate and monthly RH and between subclinical mastitis and temperature; the occurrence of subclinical mastitis and average RH were positively correlated. Our findings showed that mastitis negatively impacted the economy and that climate influenced mastitis occurrence.

Antibiofilm action using water-soluble tetra-cationic porphyrin and antibacterial photodynamic therapy against Moraxella spp. from cattle.

Infectious bovine keratoconjunctivitis (IBK) is the most important eye disease in ruminants worldwide. Moraxella bovis and Moraxella bovoculi can form biofilm and are frequently isolated from affected animals. Antimicrobials are used worldwide to treat clinical cases of IBK, although they have limited success in clearing the infection. Therefore, photodynamic therapy using porphyrins as photosensitizing molecules is an alternative method to eliminate microorganisms, including biofilms. We evaluated the antibacterial activity of a zinc(II) metalloporphyrin (ZnTMeP) against M. bovis and M. bovoculi biofilms since this compound can efficiently inactivate planktonic Moraxella spp. This study was carried out with two reference strains of Moraxella spp. (M. bovis: ATCC® 10900 and M. bovoculli: ATCC® BAA1259). The antibacterial activity of 4.0 µM of the ZnTMeP porphyrin was evaluated on forming and consolidate biofilms with three 30-min cycles of white-light exposure for three days. The ZnTMeP porphyrin reduced M. bovis and M. bovoculi biofilm formation. In addition, ZnTMeP partially destroyed consolidated M. bovoculi biofilms in the second white-light irradiation cycle, although the porphyrin had no effect against the consolidated biofilm of M. bovis. Despite the biofilm still not being completely inactivated, our findings are promising and encourage further experiments using the phototherapy protocol.

Detection of anti-Sarcocystis spp. antibodies in domestic cats, in southern Brazil.

Parasites of the genus Sarcocystis can infect several species of animals and cause multiple diseases such as equine protozoal myeloencephalitis. Felines are considered hosts of this protozoa; therefore, the present study aimed to detect anti-Sarcocystis spp.-specific antibodies in domestic cats that were under clinical evaluation, using the indirect immunofluorescence antibody test. Anti-Sarcocystis-specific immunoglobulin Gs were detected in 24 out of 497 (4.82%) cat serum samples. These findings support the fact that natural Sarcocystis infections do occur in cats. Furthermore, it highlights the importance of domestic cats as both intermediate and definitive hosts in the Sarcocystis life cycle, maintaining the parasite and serving as a source of infection for various other animals. To the best of our knowledge, this is the first study to identify antibodies against the genus Sarcocystis in cats from a region in southern Brazil.

Production performance and economic analysis of broiler chickens after vaccination with a live attenuated vaccine against avian coccidiosis.

The objective of this study was to evaluate the effectiveness of live attenuated commercial vaccine LIVACOX® T against avian coccidiosis upon parasite exposure through its correlation with productive and economic performance, clinical observation, and oocyst excretion of broiler chickens. For this purpose, 420 1-day-old Cobb chicks were divided into five groups of 84 birds: (G1) unvaccinated and unchallenged control; (G2) vaccinated on day 0; (G3) challenged on day 1; (G4) vaccinated on day 0 and challenged on day 14; and (G5) challenged on day 14. For 28 days, the clinical signs of infection, weight and feed conversion of the birds, and excretion of oocysts in the feces were evaluated. Macroscopic analysis of intestinal lesions in birds was also performed. After vaccination in G2, G3, and G4 as well as after challenge in G3, G4, and G5, there was an increase in oocyst excretion. In the analysis of weight gain, the difference in final weight between groups G3 and G4 is - 105.74 g per bird. Therefore, if we multiply this value by the average number of birds slaughtered per day in a medium/large slaughterhouse (250,000), we have 26,435 kg of chicken meat per day of slaughter, representing 581,570 kg of monthly losses (22 days of slaughter/month), or approximately R$3,489,420.00 (US$872,355.00), considering the commercial value at R$6.00/kg (US$ 1.5/kg). Thus, the productive and economic impact of coccidiosis in broiler chickens is evident, and the importance of vaccination to prevent the occurrence of the disease and reduce subsequent loss is highlighted.

Increased seroprevalence of anti-Toxoplasma gondii antibodies in dogs in southern Brazil after an outbreak of human toxoplasmosis.

Toxoplasmosis is a worldwide disease caused by Toxoplasma gondii, which can infect diverse hosts, including dogs. Although T. gondii infection in dogs is usually subclinical, they are susceptible to infection and develop a specific immune response to the parasite. In 2018, the largest outbreak of human toxoplasmosis in the world occurred in Santa Maria, in southern Brazil; however, the impact of this outbreak on other hosts was not investigated at the time. Considering that dogs often share the same environmental sources of infection as humans, mainly water sources, and that in Brazil, the detection rates of anti-T. gondii immunoglobulin G (IgG) in dogs is very high, this study investigated the frequency of anti-T. gondii IgG in dogs in Santa Maria before and after the outbreak. A total of 2.245 serum samples were analyzed, 1159 collected before the outbreak and 1086 collected after the outbreak. Serum samples were tested for anti-T. gondii antibodies using an indirect immunofluorescence antibody test (IFAT). The infection detection of T. gondii was 16% (185/1159) before the outbreak and 43% (466/1086) after the outbreak. These results showed the infection of dogs with T. gondii and the high frequency of anti-T. gondii antibodies in dogs after the outbreak in humans in 2018, reinforcing water as a possible source of infection and the importance of including toxoplasmosis in the differential diagnosis of dogs.

Anti-Leishmania spp. antibody detection in domestic cats from a visceral leishmaniasis transmission area.

Feline leishmanial infection is reported worldwide, but the epidemiological role of domestic cats in the leishmaniasis cycle remains unclear, and cats might act as cryptic reservoir hosts in endemic areas with no feline leishmaniosis cases. Considering that, a serological screening for anti-Leishmania spp. antibodies was performed by indirect immunofluorescence antibody test (IFAT) in 389 necropsied cats' serum samples from a new visceral leishmaniasis transmission area with no feline leishmanial infection reported to unveil if the cats are being exposed to the parasite. The overall seroprevalence for Leishmania spp. was 11.05% (43/389). No association was found between sex, neutering status, age group, breed, coat length, feline immunodeficiency virus (FIV) infection, and Leishmania spp. antibody detection. A positive association was found with coat color (cats within the orange spectrum with white [particolor]) (OR = 2.47, CI 95% 1 - 6.13, P = 0.044) and a negative association (OR = 0.38, CI 95% 0.18 - 0.79, P = 0.01) between feline leukemia virus (FeLV) infection and IFAT positivity for Leishmania spp. Therefore, it is concluded that the seroprevalence found was greater than 10%, indicating contact of the protozoan with cats in the region served.

Five years of the biggest outbreak of human toxoplasmosis in Santa Maria, Brazil: a review.

Toxoplasmosis is a parasitic disease caused by infection with the protozoan Toxoplasma gondii. In 2018, the first cases of people with clinical signs of acute febrile syndrome were reported, and in the same year, the largest outbreak of human toxoplasmosis ever described in the literature was reported. In this sense, the present work sought to describe the evolution of the outbreak cases in the municipality of Santa Maria, Rio Grande do Sul State, Brazil, as well as the studies conducted and published during and after the outbreak in the municipality (the period between 2018 and 2023). In addition, the discussion of public policies and their modifications after the notification of this outbreak. As a result of this research, verifying the evolution of notified and confirmed cases, the possibility of detection and genotypic characterization of T. gondii and the possibility of co-infections and evaluation of the humoral response is possible. With regard to public policies, the importance of detecting the agent through the heel prick test and increasing the monitoring of water quality to prevent outbreaks.

Identification of infection by Leishmania spp. in wild and domestic animals in Brazil: a systematic review with meta-analysis (2001-2021).

Leishmaniasis is a zoonosis caused by protozoan species of the genus Leishmania. It generates different clinical manifestations in humans and animals, and it infects multiple hosts. Leishmania parasites are transmitted by sandfly vectors. The main objective of this systematic review was to identify the host, or reservoir animal species, of Leishmania spp., with the exception of domestic dogs, that were recorded in Brazil. This review included identification of diagnostic methods, and the species of protozoan circulating in the country. For this purpose, a literature search was conducted across index journals. This study covered the period from 2001 to 2021, and 124 studies were selected. Eleven orders possible hosts were identified, including 229 mammalian species. Perissodactyla had the highest number of infected individuals (30.69%, 925/3014), with the highest occurrence in horses. In Brazil, the most commonly infected species were found to be: horses, domestic cats, rodents, and marsupials. Bats, that were infected by one or more protozoan species, were identified as potential reservoirs of Leishmania spp. Molecular tests were the most commonly used diagnostic methods (94 studies). Many studies have detected Leishmania spp. (n = 1422): Leishmania (Leishmania) infantum (n = 705), Leishmania (Viannia) braziliensis (n = 319), and Leishmania (Leishmania) amazonensis (n = 141). Recognizing the species of animals involved in the epidemiology and biological cycle of the protozoan is important, as this allows for the identification of environmental biomarkers, knowledge of Leishmania species can improve the control zoonotic leishmaniasis.

Increased frequency of detection of anti-Toxoplasma gondii antibodies in domestic cats after outbreak of human toxoplasmosis.

Toxoplasmosis affects various organisms, including humans. In 2018, the largest outbreak of human toxoplasmosis described so far was reported in southern Brazil, with 809 human cases reported, and water as the potentially primary source of infection. Therefore, in this study, we aimed to evaluate the seroprevalence of Toxoplasma gondii in naturally infected domestic cats before and after the human toxoplasmosis outbreak, as well as the potential for environmental contamination by the number of cats infected after the outbreak. We evaluated 381 serum samples from domestic cats in southern Brazil, using an indirect immunofluorescence assay, with samples considered positive at a titer of 1:20. We found that 73% (204/279) and 27% (75/279) of the samples analyzed before the outbreak were negative and positive, respectively. After the outbreak, 62% (69/112) were negative of the samples were and 38% (43/112) were positive. Notably, the proportion of positive samples before the outbreak before (27%) was significantly lower than that after the outbreak (38%; P = 0.020). Therefore, the increased seroprevalence of T. gondii in cats was probably correlated with the ingestion of contaminated water. Therefore, it is important to monitor animals, mainly definitive hosts, after toxoplasmosis outbreaks, considering that these animals can contaminate the environment and, consequently, humans.

First identification of Lutzomyia longipalpis in an area of visceral leishmaniasis transmission in central Rio Grande do Sul State, southern Brazil.

Sand flies are hematophagous dipterans and are considered vectors of the parasites belonging to the genus Leishmania, which can infect mammals, including humans, and subsequently cause leishmaniasis. Rio Grande do Sul State (RS), southern Brazil, was considered free of this disease for the last few decades. However, several autochthonous cases of visceral leishmaniasis (VL) have been recorded in different municipalities in recent years. Since 2017, cases of canine visceral leishmaniasis (CVL) have been reported in the municipality of Santa Maria, located in the central region of RS. In 2021, two cases of human VL were confirmed in the city, resulting in one death. To capture the possible vectors involved in the disease transmission cycle, Centers for Disease Control (CDC) modified light traps were installed in the peridomestic residential areas. These points were situated in two city districts where cases of CVL had been reported from January 2021 to January 2022. In the 41 sample collections of sand flies, 9 specimens of Lutzomyia longipalpis were identified, confirming the municipality as an area of VL transmission, according to Brazilian sanitary standards. The spread of Leishmania spp. has been occurring efficiently, resulting in a negative impact on the One Health. This study reports the first detection of L. longipalpis in the central region of RS.

Dynamics of Leishmania spp. infection in dogs from an unaffected region in transition to a visceral leishmaniasis transmission area, Rio Grande do Sul, Brazil.

In Brazil, visceral leishmaniasis (VL) has been expanding and urbanizing, mainly in non-endemic areas such as the State of Rio Grande do Sul. Considering that infected dogs are the main reservoirs of VL in urban areas, the present study aimed to evaluate the propagation of canine visceral leishmaniasis (CVL) infection from an unaffected region in transition to a VL transmission area. For this, 1159 and 1087 samples of canine serum from 2015 and 2021, respectively, were analyzed, using the indirect immunofluorescence test. In addition, necropsy reports between 2007 and 2021 were evaluated. The results showed a prevalence of anti-Leishmania spp. antibodies of 7.5% in the samples from 2015, while in 2021 samples, it was 23.5%, with an incidence of 0.4 cases per 100 dogs. It is noteworthy that in 2007, there was no record of CVL as the cause of death in the pathological reports, and in 2021, 41 diagnoses were made with the protozoan being a determinant of the death of the animal. These values indicate an increasing trend in the prevalence and incidence coefficients of CVL. The results of this study allowed us to verify the spread of the disease from an unaffected region to a transmission area of the agent, as well as provide subsidies for health authorities to implement improvements in the CVL control program in the municipality, to mitigate the emergence of human cases of the disease.

Prevalence and molecular detection of Leishmania spp. in bats from Rio Grande do Sul state, Brazil.

This study aimed to detect the occurrence of infection by Leishmania spp.in bats from 34 municipalities of Rio Grande do Sul state (RS; southern Brazil) from 2016 to 2021. A total of 109 bats were provided by the Centro Estadual de Vigilância em Saúde of RS, including six species belonged to Molossidae family, six to Vespertilionidae family, and two to Phyllostomidae family. Leishmania spp. was identified using the nested-PCR method by amplifying the SSU rDNA ribosomal subunit gene into four organ pools: (1) the liver, spleen, and lymph node; (2) heart and lungs; (3) skin; and (4) bone marrow of each bat. Three (3/109, 2.7%) animals tested positive for Leishmania spp. The respective PCR-positive organs came from pools 1 and 3. Two bats (Tadarida brasiliensis) were from the municipality of Canoas, and sequences analysis confirms the species identification as Leishmania infantum. In the third bat (Molossus molossus), from Rio Grande, it was not possible to determine the protozoa species, being considered Leishmania spp. Our results indicate that bats can participate in the biological cycle of Leishmania spp. and perform as host, reservoir, and/or source of infection of the protozoa in different areas of RS. More studies will be needed to elucidate the role of these Chiropteras in the circulation of Leishmania spp. This is the first study reporting the occurrence of Leishmania spp. in bats in Rio Grande do Sul state, southern Brazil.

Acaricide activity of organo-modified siloxane and acaricide associations in Rhipicephalus microplus.

Search to a new alternative to control bovine ticks (Rhipicephalus microplus), the present study aimed to evaluate the acaricidal activity of organo-modified siloxane alone and in association with different commercial products or with piperonyl butoxide (BPO). Engorged females were subjected to an in vitro immersion test and 10 groups were used: control, 0.5% siloxane, 1% siloxane, 2% siloxane, 0.5% siloxane + 5% BPO, 1% siloxane + 5% BPO, 2% siloxane + 5% BPO, commercial product, 0.5% siloxane + commercial product, and 1% siloxane + commercial product. After immersion, engorged females were incubated for 14 days for oviposition and hatchability tests. Another immersion test was performed with 5% siloxane and 2.5% siloxane + 10% BPO to evaluate the histopathological changes. Then, engorged females were incubated for 0, 2, 4, 8, 12, 24, 36, 48, 60, 72, 84, 96, 120, 144, and 168 h and immersed in 10% formaldehyde for later analyses. The unassociated siloxane showed an acaricide efficacy of 93.88% at 2% concentration, and when associated with 5% BPO, it reached 100% efficacy at all tested concentrations. The tested commercial products showed enhanced efficacy when associated with siloxane. Histopathological analysis showed cell changes in both treatments and total cell disintegration after 120 h in the 5% siloxane group and after 96 h in the 2.5% siloxane + 10% BPO group. Therefore, siloxane alone or in combination is an alternative against R. microplus, and siloxane enhances the efficacy of available commercial products.

Efficiency of 5% toltrazuril in the metaphylactic treatment of coccidiosis in naturally infected and extensively reared beef calves.

Eimeria spp. infection is one of the main diseases that affect young cattle in beef and dairy herds, leading to economic losses and compromising the performance and growth of animals. This study aimed to evaluate the effectiveness of different protocols of metaphylactic treatment with 5% toltrazuril (15 mg/kg) in naturally infected, extensively reared beef calves from birth to 1 year of age. We used 92 calves aged up to 2 weeks of life, initially divided into two experimental groups: treated and control. The animals were evaluated fortnightly with individual count of oocysts per gram of feces (OPG) tests until weaning; thereafter, they were again divided into four subgroups: I-treated at both birth and weaning; II-treated at birth but not treated at weaning; III-not treated at birth but treated at weaning; and IV-neither treated at birth nor at weaning (control). During the experimental period, the animals were evaluated for weight gain, excretion of oocysts, and presence of pathogenic species of Eimeria spp. In the first stage of the study, less oocysts were excreted in the treated group for up to 75 days and at 150 days of age (p < 0.05). In the final stage of the study, significant differences occur between groups I and II, I and IV, II and III, and III and IV (p = 0.3512), in the collection 20 days after treatment. Eimeria bovis was the most frequently identified species during the experimental period. Moreover, there was a positive correlation between the presence of diarrhea in the calves and the number of oocysts excreted, treated group (p = 0.0092) and untreated group (p = 0.2). There was no significant difference in weight gain of animals in any of the study periods (p > 0.05).

Economic losses caused by the use of low-efficacy anthelmintic drugs in growing heifers.

The aim of this study was to compare the economic revenue related to the use of low- or high-efficacy anthelmintic drugs within suppressive or strategic schemes of treatment in growing heifers. Heifers raised in a semi-intensive grazing system in southern Brazil were used. Levamisole and ivermectin were selected as the high- and the low-efficacy drugs, respectively, based on a previous efficacy test. Subsequently, these drugs were used within strategic (Strat; four times per year) or suppressive (Supp; once a month) treatment regimens in the heifers, and their liveweight and eggs per gram of feces counts were monthly evaluated during a 13-month period. The total costs of the treatments and their cost-benefit ratio in regard to liveweight gain were calculated. Final mean liveweight gains (kg) observed were 126.7 (Strat-Low), 133.6 (Supp-Low), 141.3 (Strat-High), 142.9 (Supp-High), and 125.8 (Control). Treatments with a high-efficacy drug resulted in monetary gains of US$ 19.56 (Strat-High) and US$ 14.98 (Supp-High), but Supp-Low and Strat-Low treatments caused economic losses. Total cost of the efficacy test (US$ 374.79) could be paid by the additional liveweight gain of 20 heifers from the Strat-High group. These results showed that it would be preferable not to treat the heifers against GIN if compared with treating them with a low-efficacy drug. In addition, we showed that the use of four treatments per year with a high-efficacy drug-selected by efficacy test-resulted in a profitable management to control GIN in growing heifers raised in a semi-intensive gazing system in southern Brazil.

Molecular detection of Cryptosporidium spp. and the occurrence of intestinal parasites in fecal samples of naturally infected dogs and cats.

Cats and dogs are hosts of a large number of gastrointestinal parasites and can shed helminth eggs and protozoan oocysts in their feces. The close relationship between companion animals and humans intensifies human exposure to zoonosis caused by parasites. In this study, 177 fecal samples were collected: 128 from dogs and 49 from cats of both sexes and varied ages. One or more intestinal parasites were observed in 56.2% (72/128) of the dog fecal samples and in 53.0% (26/49) of the cat fecal samples. Parasitic monoinfection was present in 70.8% (51/72) of dog samples and in 46.1% (12/26) of cat samples, whereas multi-infection was observed in 29.2% (21/72) and 53.8% (14/26) of dog and cat samples, respectively. The detection frequency of Cryptosporidium spp. was 22.6% (40/177) using Ziehl-Neelsen staining. DNA was extracted from all samples and the Cryptosporidium small subunit ribosomal ribonucleic acid (SSU rRNA) gene was amplified from 5.6% (10/177) of the fecal samples using nested polymerase chain reaction (PCR). Amplification was achieved in 4.6% (6/128) of the dog samples and in 8.2% (4/49) of the cat samples. DNA sequencing of the nested PCR positive samples identified Cryptosporidium canis in 66.6% (4/6) and Cryptosporidium parvum in 33.3% (2/6) of the dog samples and Cryptosporidium felis in 75% (3/4) and Cryptosporidium parvum in 25% (1/4) in the cat samples. The present study thus demonstrated significant levels of gastrointestinal parasite infection in companion animals and highlighted the presence of zoonosis agents.

Economic viability of anthelmintic treatment in naturally infected beef cattle under different nutritional strategies after weaning.

The aim of the present study was to evaluate the effects of treatment with different anthelmintic compounds on the productivity of naturally infected calves and the economic viability of these treatments within extensive breeding systems employing different nutritional strategies after weaning. For this purpose, 4 farms with 42-60 calves naturally infected with gastrointestinal nematodes were selected. The calves were distributed into 6 groups (7-10 animals each) per farm and treated with ivermectin 1%, ivermectin 3.15%, eprinomectin 5%, levamisole 7.5%, albendazole 15%, and control group (no treatment). These animals were evaluated over an experimental period of 150 days. Levamisole 7.5% presented the best capacity for the reduction of eggs per gram (EPG) of feces in all herds evaluated, followed by albendazole 15% and eprinomectin 5%. Parasite resistance to multiple drugs was found in all herds, especially those of Cooperia, Haemonchus, Oesophagostomum, and Trichostrongylus. For farm 1, differences in weight gain and EPG reduction percentages led to a difference of US$285.06 between the levamisole and ivermectin 3.15% groups. Similar findings were noted for the levamisole and ivermectin 1% groups of farm 3, with a difference of US$399.37 because of the final weight gain in these groups. For farms 2 and 4, the ivermectin 3.15% and control groups, respectively, were the most profitable; these unexpected results were possibly influenced by variables not measured during the experimental period. This study suggested that anthelmintic treatments should always precede an efficacy test, once they are demonstrated to be most profitable under adequate breeding conditions, to ensure adequate control of gastrointestinal nematode infection.