Doenças parasitárias em bovinos e ovinos no sul do Brasil: frequência e estimativa de perdas econômicas

In vitro evaluation of the potential of mites of the family Macrochelidae (Acari: Mesostigmata) as macrobiological agents against the nematode Haemonchus contortus (Strongylida: Trichostrongylidae)

Small ruminants (sheep and goats) constantly suffer from endoparasitoses caused by gastrointestinal nematodes. Among these, the species Haemonchus contortus (Rudolphi, 1803) is considered to be the one of greatest importance within sheep farming. This nematode is difficult to control due to its resistance to most commercial anthelmintics. The aim of the present study was to assess the potential of macrochelid mites as macrobiological agents for controlling endoparasitoses of sheep caused by the nematode, H. contortus. For this, novel in vitro methodology was used, in which assessments were made not only of the predatory ability but also the population growth of mite species (Macrocheles merdarius, Macrocheles robustulus and Holostaspella bifoliata) when offered larvae of the nematode, H. contortus. The predatory ability of the mites, M. merdarius and H. bifoliata were efficient regarding their predatory ability against H. contortus nematode larvae. The mite, M. merdarius exhibited the highest predation rate with mean distribution values for the treated group of 18656 ± 10091 and for the control group of 1178 ± 712 (P < 0.0001). The species, H. bifoliata presented the highest population growth rate, with a percentage acarid recovery rate of 263% in relation to the number added initially. The data from this in vitro predation experiment suggest that, M. merdarius and H. bifoliata showed promise as macrobiological agents for controlling gastrointestinal endoparasitoses of sheep caused by the nematode, H. contortus given that both species reduced the population of this helminth by more 70% and the number of mites recovered was three times greater than the number added.

Validation of targeted selective treatment (TST) methodology for gastrointestinal parasites of adult sheep in different physiological states

We aimed to validate a targeted selective treatment (TST) methodology for treating parasitic gastrointestinal infections in ewes in different physiological states using parasitological and hematological parameters. Forty ewes were monitored from December 2021 to June 2022 and evaluated during various physiological stages in their life cycle. Before starting the experiment, a fecal egg count (FEC) reduction test was performed to evaluate the efficacy of the anthelmintic (AH) treatment. Weekly assessments were performed based on the Famacha© (F) system and body condition score (BCS), and ewes were subjected to AH treatment when necessary, with their physiological states recorded. Ewes were treated when they presented F ≥ 3, BCS ≤ 2.0 (when F = 2), or submandibular edema. Parasitological, i.e., FEC, and hematological, i.e., hematocrit (Ht), parameters were evaluated monthly to determine the efficiency of the TST methodology. Comparisons between the mean Ht and FEC values in ewes subjected to AH treatment and untreated ewes were performed using analysis of variance, followed by Tukey's test. Spearman's correlation was performed to determine the correlation between the variables, i.e., F scores, BCS, Ht, and FEC. All tests were performed at a significance level of 5 %. During the experimental period, 1138 evaluations were performed. The main reason for AH treatment was F ≥ 3. Ewes in early pregnancy, lactation and late pregnancy received comparatively more AH treatments than the other physiological states. Ewes in late pregnancy and lactation exhibited lower mean Ht values (23.5 % and 22.9 %) and higher mean FEC values (3269 and 1426) compared with those in early pregnancy (30.2 % and 727 EPG). In addition, a statistically significant difference was observed in the Ht and FEC values of ewes that presented submandibular edema (P < 0.001) compared with those that did not exhibit submandibular edema. The genus Haemonchus sp. showed a 96.4 % prevalence in coprocultures. A positive correlation existed between F scores and FEC (r = 0.3819) and a negative correlation between F scores and Ht (r = -0.4728). Ewes that needed AH treatment had lower mean Ht values than ewes that did not need the treatment (19.2 % × 29.3 %; P < 0.001) and higher mean FEC values (8747 × 1163; P < 0.001), confirming that these ewes needed AH treatment. The TST methodology based on F scores, BCS, and submandibular edema could effectively identify individuals in the herd needing AH treatment, identifying 13 % additional cases requiring treatment than using only the F score criterion.

Seropositivity of Anti-Toxoplasma gondii and Anti-Neospora caninum Antibodies in Cattle Intended for Human Consumption in an Amazonian Area of North Brazil

Toxoplasma gondii and Neospora caninum are obligate intracellular intestinal coccidia distributed worldwide, and are causative agents of toxoplasmosis and neosporosis, respectively. The aim of this study was to evaluate the prevalence of anti-T. gondii and anti-N. caninum antibodies and the factors associated with infections in beef cattle intended for human consumption in an Amazonian area of North Brazil. We collected blood samples of 387 cattle from 50 herds located in different municipalities of the State of Rondônia. An epidemiological questionnaire was distributed to farmers, with regard to nutritional, sanitary and reproductive herd management. The samples were identified, refrigerated and sent for serological analyses via IFAT (Immunofluorescent Antibody Test). Among the 387 analyzed animals, 91 (23.5%; CI 95%: 18.8-27.2) were positive for anti-T. gondii antibodies, with titers varying from 1:64 (75.8%) to 1:512 (2.2%). For anti-N. caninum antibodies, only four animals (1%; CI 95%: 0-2.7) were positive, with titers ranging from 1:400 (50%) to 1:1600 (25%). We observed a significant rate of anti-T. gondii antibodies in the variables "pure breed" and "contact with free-range chickens" (p < 0.2). There were no risk factors associated with the presence of anti-T. gondii or anti-N. caninum antibodies. In conclusion, there was a high prevalence of anti-T. gondii antibodies in beef cattle intended for human consumption in the State of Rondônia, Brazil, and a low prevalence of anti-N. caninum antibodies. Longitudinal studies can better elucidate the cause of these prevalence levels and how they could be better prevented and controlled.

Epidemiological aspects of cattle tick fever in Brazil

The present work reviews the epidemiologic situation of Anaplasma marginale and Babesia spp. infections and the occurrence of cattle tick fever outbreaks in Brazil. In areas of tick fever enzootic instability, environmental conditions interfere with the development of Rhipicephalus (Boophilus) microplus: chilly winter in the southern region, floods in the Pantanal, and low humidity in the Caatinga. In contrast, the climatic conditions of stable zones (Cerrado, Amazon and Atlantic Forest biomes) favor tick development. In enzootic areas, tick fever is uncommon because the animals are in frequent contact with the parasite, acquiring immunity naturally during the period of innate resistance; however, outbreaks may occur when calves become infested by considerable numbers of infected ticks during this period or in adults raised in tick-free environments that become infested for the first time when transporting to stable areas. It is necessary to better understand the disease's risk factors under stable conditions and the implications of the mechanical and other vector transmission of A. marginale. To prevent tick fever outbreaks in Brazil, it is important to develop and use anaplasmosis and babesiosis vaccines in cattle from enzootic unstable regions, especially when animals are moved to stable areas.

Global genomic methylation related to the degree of parasitism in cattle

The objective of the present study was to characterize a herd of 72 ½ Angus × ½ Nellore heifers, identify the resistant, resilient and susceptible animals to parasites, relate the overall DNA methylation of these animals with the degree of parasitism, evaluated by the egg count per gram of feces (EPG), Haematobia irritans count (horn fly) and Rhipicephalus microplus count (bovine tick). The experiment was carried out in a completely randomized design, containing 72 treatments, with each animal considered a treatment, and 11 repetitions, with each collection within a year considered a repetition. The data obtained from the counts of the evaluated parasites were subjected to statistical analysis using the SISVAR program, to classify heifers according to the degree of parasitism in low (resistant), intermediary (resilient) and high (susceptible) parasite load for infection by nematodes, infestation by ticks and flies. Addition the animals in these three groups, by hierarchical grouping using the GENES program, heifers were classified as to the degree of parasitism by the three parasites along with the DNA methylation content of the animals in each group. A negative relationship was observed between resistance and methylated DNA content in both classifications, with the resistant, resilient, and susceptible animals showing the highest, intermediate, and lowest methylated DNA quantifications, respectively. Thus, the methodologies used herein enabled the classification of 72 heifers according to the degree of collective infection by gastrointestinal nematodes and infestation by ticks and horn flies, thereby establishing a link between the degree of parasitic resistance in cattle and the global methylated DNA quantification.

Genome-Wide Association Study for Haemonchus contortus Resistance in Morada Nova Sheep

Among the gastrointestinal nematodes affecting sheep, Haemonchus contortus is the most prevalent and virulent, resulting in health problems and production losses. Therefore, selecting sheep resistant to H. contortus is a suitable and sustainable strategy for controlling endoparasites in flocks. Here, 287 lambs of the native Brazilian Morada Nova hair sheep breed were subjected to two consecutive artificial infections with H. contortus and assessed for fecal egg count (FEC), packed cell volume (PCV), and live weight (LW). Forty-four animals ranked as having extreme resistance phenotypes were genotyped using the Illumina OvineSNP50v3 chip. A case−control genome-wide association study (GWAS) detected 37 significant (p < 0.001) markers in 12 ovine chromosomes in regions harboring quantitative trait loci (QTL) for FEC, Trichostrongylus spp. adults and larvae, weight, and fat; and candidate genes for immune responses, mucins, hematological parameters, homeostasis, and growth. Four single-nucleotide polymorphisms (SNP; OAR1_rs427671974, OAR2_rs419988472, OAR5_rs424070217, and OAR17_rs401006318) genotyped by qPCR followed by high-resolution melting (HRM) were associated with FEC and LW. Therefore, molecular markers detected by GWAS for H. contortus resistance in Morada Nova sheep may support animal selection programs aimed at controlling gastrointestinal nematode infections in flocks. Furthermore, genotyping of candidate genes using HRM qPCR may provide a rapid and efficient tool for animal identification.

Economic impact of gastrointestinal nematodes in Morada Nova sheep in Brazil

This study evaluated the economic impact of gastrointestinal nematode (GIN) infection in Morada Nova lambs under different parasite chemical control conditions. For this, 246 lambs, in the rainy and dry season, were randomized into groups according to their anthelmintic treatment with levamisole: control (CT: no treatment); routine treatment (RT: treated every 42 days); and targeted selective treatment (TST: treated according to the average daily weight gain, DWG). From 63 days of age (D63) to D210, the lambs were weighed and monitored for GIN infection parameters. Spending on anthelmintics in the production system was 1.3% of the total economic result. The economic result per animal (R$ 5.00 = US$ 1.00) was higher in the RT group, amounting to US$ 6.60 in the rainy and US$ 5.69 in the dry season, due to higher DWG. Thus, RT presented economic results 14.4% and 10.9% higher than CT, and 7.2% and 1.9% higher than TST, in the rainy and dry season, respectively. However, fast development of resistance made RT unfeasible. Here, the economic impact of GIN infection on a national scale is discussed, demonstrating its importance and the impossibility of profitable and sustainable sheep production without adequate control.

Causes of death and organs condemnation at slaughter of sheep in a feedlot system in Southern Rio Grande do Sul

ABSTRACT: In Brazil the second largest sheep herd is in Rio Grande do Sul and in recent years the demand for meat consumption of this specie has increased. Intensive farming systems have made considerable progress in this region with the objective of increasing the production of sheep for slaughter and obtaining a uniform batch to ensure better quality of sheep meat to consumers. However, the agglomeration and stress that animals go through can lead to the occurrence of illnesses and economic loss to producers. The objectives of this paper were to determine the main causes of death that affected sheep in a feedlot system, to establish forms of control and prophylaxis of diagnosed illnesses, and to estimate the economic losses resulting from them. The objective was also to determine the causes of condemnation of organs or carcasses in the slaughterhouses that processed the sheep were sent, and to estimate the losses in this productive sector. For this, a follow-up work was carried out in an establishment located in the city of São Lourenço do Sul, Rio Grande do Sul, from October 2020 to September 2021. The dead sheep at the feedlot were necropsied, and the diagnosis was made based on clinical signs, pathology, and bacteriology. The main diseases diagnosed were parasitic enteritis (15.4%), pneumonia (13%), and listeriosis (9.6%). In the slaughterhouse study, the lesions that led to the highest number of condemnations were hydatidosis (29.9%), renal congestion (26.2%), and renal ischemia (25.8%). The economic losses estimated for the death of sheep in 2021 was R$17,480.00, significantly lower than the approximate losses in 2019 and 2020 of R$50,000.00 and R$54,000.00, respectively. This highlights the importance of technical assistance to reduce these losses due to mortality in sheep raised in a feedlot system. It was also observed the kidneys of the sheep were the organs most frequently selected for condemnation. The economic value of the kidneys sold as disposed waste was eight time lower than that the value of kidneys suitable for consumption.

Effect of growing forage legumes on the migration and survival in the pasture of gastrointestinal nematodes of sheep

In order to identify types of forage that inhibit pasture contamination, an evaluation was performed of the effect of the forage legumes Trifolium repens (white clover), Trifolium pratense (red clover) and Lotus corniculatus (bird's-foot-trefoil) on the survival and migration of infective larvae (L3) of gastrointestinal nematodes (GIN) of sheep. An experimental area of 441 m2 was divided into four blocks, subdivided into areas of 1.20 × 1.20 in which the three forage legumes were separately overseeded. After growth of the forage in each subdivision, experimental units were established that were later artificially contaminated with sheep faeces containing GIN eggs. Between October and December 2018, pasture, faecal and soil samples were collected on four occasions during weeks 1, 2, 4 and 8 after the deposition of faeces. In week 6, the forage legumes in all the experimental units were mown to simulate grazing. The number of L3 was quantified to determine their survival in the pasture, faeces and soil. In addition, the horizontal migration of L3 was measured at two distances from the faecal pellets (10 and 30 cm), as well as their vertical migration at two heights of the plant stems, that is, lower half and upper half. Larvae vertical migration was affected by the forage species (P < 0.001), in that bird's-foot-trefoil contained fewer larvae in the upper stratum. Bird's-foot-trefoil restricted the migration of L3 to the upper stratum of the plant, which could potentially decrease the risk of infection by intestinal nematodes in grazing sheep.

Gastrointestinal Parasites in Sheep from the Brazilian Pampa Biome: Prevalence and Associated Factors

Parasitic infections are common in sheep farming worldwide. A cross-sectional study was carried out to determine the prevalence and associated risk factors among gastrointestinal parasites and sheep herds from the Brazilian Pampa biome, Rio Grande do Sul state, Brazil. Twenty-one farms were visited, where rectal faecal samples were individually collected from 309 animals. The sheep industry on the studied farms was characterised by small farms with a low level of technification, an extensive grazing system and meat production. Of all samples analysed, strongyle nematodes had the highest prevalence (77.02%), followed by Eimeria spp. (70.55%), Moniezia expansa (20.39%) and Strongyloides papillosus (17.48%). Mixed infection, between helminths and protozoans, was detected in 68.61% of samples. All herds were positive for strongyle and Eimeria spp. A predominance of Haemonchus spp. and Trichostrongylus spp. nematodes was observed in the herds. Younger animals were significantly more affected by Eimeria and M. expansa. In the semi-intensive and intensive systems, a higher frequency of Eimeria and strongyle infections was observed. Parasite infection was significantly reduced at low animal densities. The Brazilian Pampa region presents a high prevalence of gastrointestinal parasites among sheep; age, breeding system and stocking density were factors associated with parasite infection.

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).

In vivo selection for Haemonchus contortus resistance to monepantel

Gastrointestinal nematodes significantly affect the ovine industry, and Haemonchus contortus is considered the most pathogenic parasite in tropical regions. This situation is aggravated when the main strategy to control worms fails because of the genetic resistance that parasites acquire against anthelmintics. Aiming to anticipate the events involved in anthelmintic resistance, we induced monepantel resistance in H. contortus by in vivo subdosing of sheep hosts. Four successive passages of a monepantel-susceptible H. contortus isolate in Santa Ines or Ile de France sheep hosts resulted in three monepantel-resistant (efficacy varying from 0 to 58.5%) H. contortus isolates. Sheep hosts were treated from 0.075 mg/kg to the therapeutic dose of 2.5 mg/kg of monepantel in 19-26 rounds of selection for 112-133 weeks. Success in inducing H. contortus resistance to monepantel may have been affected by worm burden and by host-parasite interactions, including a possible effect of the breed of sheep hosts. We conclude that subdosing of sheep, although time-consuming, is an efficient in vivo strategy for the induction of monepantel resistance in H. contortus. The resistant parasites can be used in further studies to elucidate the genetic and biochemical events involved in the acquisition of anthelmintic resistance.