Benzimidazole Resistance in Cattle: The First Report of the Presence of F200Y Mutation in Cooperia in Ecuador.

Anthelmintic resistance among GINs in cattle is a worldwide issue. Identifying the early signs of anthelmintic resistance (AR) is necessary to sustainably manage bovine parasitic infections. This study aimed to evaluate the resistance status of bovine parasitic nematodes against FBZ on a farm with a known history of broad-spectrum anthelmintic usage in Ecuador. FBZ efficacy was analyzed using a fecal egg count reduction test (FECR test) and ß-tubulin 1 mutation identification in Cooperia spp., the dominant nematode parasite identified before and after treatment. According to the FECR test, the nematode population was susceptible to FBZ. After amplifying and cloning the ß-tubulin 1 of Cooperia spp., an F200Y mutation was found in 43% of the pooled larva coproculture after treatment. This study reports, for the first time, the presence of F200Y resistance-conferring mutation in Cooperia spp. in Ecuador. Although the nematode population was phenotypically susceptible to FBZ, the presence of F200Y suggests the existence of resistance in the early stages. Our findings highlight the need to implement alternative control strategies for parasitic infections besides broad-spectrum anthelmintics.

Impact on beef cattle productivity of infection with anthelmintic-resistant nematodes.

ABSTRACTAims: The main goal of the current study was to evaluate, on a commercial beef cattle farm, the impact of infection with gastrointestinal nematodes resistant to both ivermectin (IVM) and moxidectin (MXD) on the productivity of calves.Methods: Male Aberdeen Angus calves, aged 9-11 months, with faecal nematode egg counts (FEC) ≥200 epg and body weight ≥190 kg, were allocated to two herds. Herd A (n = 90) grazed a maize-winter forage crop rotation and Herd B (n = 90) grazed a 2-year-old Agropyrum pasture. On Day 0 in each herd, calves were randomly allocated into five groups (n = 18), which were treated with 0.2 mg/kg IVM; 0.2 mg/kg MXD; 3.75 mg/kg ricobendazole (RBZ), both IVM and RBZ, or remained untreated. Faecal samples collected on Days -1 and 19 were used to determine the percentage reduction in FEC, and genera of the nematodes were determined by the identification of the third-stage larvae recovered from faecal cultures. Total weight gain was determined from body weights recorded on Days -1 and 91.Results: Overall mean reduction in FEC was 42% for IVM, 67% for MXD, 97% for RBZ and 99% for IVM + RBZ. The reduction in FEC for Cooperia spp. was ≤78% for IVM and MXD, and for Haemonchus spp. was 0 and 36% for IVM and MXD, respectively, confirming the presence of parasites resistant to both anthelmintics. Only IVM + RBZ treatment resulted in 100% efficacy against Haemonchus spp. The overall estimated mean total weight gain for calves treated with IVM was 15.7 (95% CI = 11.9-19.7) kg and for calves treated with IVM + RBZ was 28.8 (95% CI = 25-32.5) kg (p < 0.001). Mean total weight gain for calves treated with MXD was 23.5 (95% CI = 19.7-27.2) kg.Conclusions and clinical relevance: In calves naturally infected with resistant nematodes, under the production system assessed here, weight gains were lower in calves treated with anthelmintics that were moderately or highly ineffective compared to those treated with highly effective anthelmintics. These results demonstrate to farmers and veterinarians the importance of a sustainable and effective nematode control under field conditions.

Economic analysis of strategic control program (5, 8, 11) for gastrointestinal nematodes in grazing beef cattle during the growing phase in Central Brazil / Análise econômica do programa de controle estratégico (5, 8, 11) de nematodas gastrointestinais em bovinos de corte em recria a pasto no Brasil Central

This study aimed to analyze economically different control protocols for beef cattle gastrointestinal nematodes in Brazil. Field study data previously published was used to compare three groups: 1) non-dosed; 2) current deworming program with two doses - May and November; and 3) alternative strategic control program with three doses - May, August, and November. An economic sensitivity analysis was performed based on beef carcass price (BCP) variation, thus creating three economic scenarios: 1) more probable (M) using the mean BCP in the studied region; 2) optimistic (O) using the mean BCP plus standard deviation; and 3) pessimistic (P) using the mean BCP minus standard deviation. Stock valuation (SV), operational result (OP), and treatment differential (TD) were calculated for each scenario. Average BCP was US$ 2.93 kg-1 carcass (± US$ 0.27 kg-1 carcass). The mean annual cost of deworming per animal was US$ 5.43 and US$ 7.97 for protocols with two and three doses, respectively. The cost of anthelmintic treatment represented 0.63% and 0.74% of operating results, both in M scenario. TD ranged from 9.5% to 27.6% for the assessed protocols. Regardless of the scenario, the protocol with three annual dosages presented the highest SV and OP, which economically justifies its implementation in strategic control of gastrointestinal nematodes in grazing beef cattle in Central Brazil. These results also demonstrate the relevance of strategic anthelmintic treatments in weaned stocker calves in tropical and humid subtropical areas.(AU)

O objetivo deste estudo foi analisar diferentes protocolos de controle de nematodas gastrointestinais em bovinos de corte no Brasil. Dados de estudo de campo publicados anteriormente foram utilizados para comparar três grupos: 1) não dosificado; 2) o programa de desverminação utilizado atualmente com duas dosificações - maio e novembro; e 3) um programa de controle estratégico com três dosificações - maio, agosto e novembro. A análise de sensibilidade econômica foi realizada com base na variação do Preço da Carcaça Bovina (PCB), assim criando três cenários econômicos: mais provável (M), utilizando o PCB médio na região do estudo; Otimista (O), usando o PCB mais o desvio padrão e pessimista (P), usando o PCB menos o desvio padrão. Para cada cenário, a valorização de estoque (VE), o resultado operacional (OP) e o diferencial de tratamento (DT) foram calculados. O PCB médio foi de US$ 2.93 kg-1 de carcaça (± US$ 0.27 kg-1 de carcaça). O custo médio anual de desverminação por animal foi US$ 5.43 e US$ 7.97 no protocolo com duas e três doses, respectivamente, e o custo do anti-helmíntico representou 0.63% e 0.74% do resultado operacional, ambos no cenário M. Os diferenciais de tratamento dos protocolos avaliados variaram de 9.5% a 27.6%. Independentemente do cenário econômico simulado, o protocolo com três dosagens anuais apresentou a maior VE e OP entre os protocolos avaliados, justificando economicamente sua implementação para o controle estratégico de nematodas gastrointestinais de bovinos de corte criados em pastagem no Brasil Central e também demonstram a relevância de tratamentos anti-helmínticos estratégicos em bezerros desmamados em áreas subtropicais tropicais e úmidas.(AU)

Economic analysis of strategic control program (5, 8, 11) for gastrointestinal nematodes in grazing beef cattle during the growing phase in Central Brazil / Análise econômica do programa de controle estratégico (5, 8, 11) de nematodas gastrointestinais em bovinos de corte em recria a pasto no Brasil Central

This study aimed to analyze economically different control protocols for beef cattle gastrointestinal nematodes in Brazil. Field study data previously published was used to compare three groups: 1) non-dosed; 2) current deworming program with two doses - May and November; and 3) alternative strategic control program with three doses - May, August, and November. An economic sensitivity analysis was performed based on beef carcass price (BCP) variation, thus creating three economic scenarios: 1) more probable (M) using the mean BCP in the studied region; 2) optimistic (O) using the mean BCP plus standard deviation; and 3) pessimistic (P) using the mean BCP minus standard deviation. Stock valuation (SV), operational result (OP), and treatment differential (TD) were calculated for each scenario. Average BCP was US$ 2.93 kg-1 carcass (± US$ 0.27 kg-1 carcass). The mean annual cost of deworming per animal was US$ 5.43 and US$ 7.97 for protocols with two and three doses, respectively. The cost of anthelmintic treatment represented 0.63% and 0.74% of operating results, both in M scenario. TD ranged from 9.5% to 27.6% for the assessed protocols. Regardless of the scenario, the protocol with three annual dosages presented the highest SV and OP, which economically justifies its implementation in strategic control of gastrointestinal nematodes in grazing beef cattle in Central Brazil. These results also demonstrate the relevance of strategic anthelmintic treatments in weaned stocker calves in tropical and humid subtropical areas.

O objetivo deste estudo foi analisar diferentes protocolos de controle de nematodas gastrointestinais em bovinos de corte no Brasil. Dados de estudo de campo publicados anteriormente foram utilizados para comparar três grupos: 1) não dosificado; 2) o programa de desverminação utilizado atualmente com duas dosificações - maio e novembro; e 3) um programa de controle estratégico com três dosificações - maio, agosto e novembro. A análise de sensibilidade econômica foi realizada com base na variação do Preço da Carcaça Bovina (PCB), assim criando três cenários econômicos: mais provável (M), utilizando o PCB médio na região do estudo; Otimista (O), usando o PCB mais o desvio padrão e pessimista (P), usando o PCB menos o desvio padrão. Para cada cenário, a valorização de estoque (VE), o resultado operacional (OP) e o diferencial de tratamento (DT) foram calculados. O PCB médio foi de US$ 2.93 kg-1 de carcaça (± US$ 0.27 kg-1 de carcaça). O custo médio anual de desverminação por animal foi US$ 5.43 e US$ 7.97 no protocolo com duas e três doses, respectivamente, e o custo do anti-helmíntico representou 0.63% e 0.74% do resultado operacional, ambos no cenário M. Os diferenciais de tratamento dos protocolos avaliados variaram de 9.5% a 27.6%. Independentemente do cenário econômico simulado, o protocolo com três dosagens anuais apresentou a maior VE e OP entre os protocolos avaliados, justificando economicamente sua implementação para o controle estratégico de nematodas gastrointestinais de bovinos de corte criados em pastagem no Brasil Central e também demonstram a relevância de tratamentos anti-helmínticos estratégicos em bezerros desmamados em áreas subtropicais tropicais e úmidas.

Changes in biochemical analytes in calves infected by nematode parasites in field conditions.

Parasitic infections caused by nematodes are a major problem in bovines that resulting in losses in animal health and production. Thus, the aim of this study was to evaluate alterations in selected serum biochemical analytes in calves naturally infected with gastrointestinal (GI) and pulmonary nematodes without clinical signs. For this, samples of feces and blood of 86 calves were collected. Fecal egg counts (FEC) were determined using the modified McMaster technique with a sensitivity of 50 eggs per gram of feces (EPG). Positive nematode FEC was processed for coproculture using pooled samples to identify Strongylidae infective larvae (L3). First stage-larvae (L1) of Dictyocaulus viviparous were identified by a modified Baermann method. The biochemical analytes determined were: acute phase proteins such as haptoglobin and paraoxonase type 1; the enzymes acetylcholinesterase; butyrylcholinesterase; the lipid profile (triglycerides and total, HDL, and LDL-cholesterol); serum iron profile (iron and unsaturated iron-binding capacity); total protein and albumin; pancreatic profile (amylase and lipase); and minerals (phosphorus and calcium). The calves were divided into four groups according to the results of EPG and the modified Baermann method. Group 1: healthy control animals (n=16); Group 2: calves with only GI parasites (n=51): This group was sub-divided into sub-groups according to the EPG threshold: 2a-GI parasites with low EPG (n=23), and 2b-GI parasites with high EPG (n=28). Group 3: animals with only lungworms (n=5), and Group 4: calves with lung+GI parasites (n=14). The more prevalent genera in all coprocultures were: Cooperia spp., Haemonchus spp., Oesophagostomum spp., and Trichostrongylus spp. The nonparametric Kruskal-Wallis test was used to compare the groups and Dunn's post-test was used for multiple comparisons as the data was not normally distributed (P<0.05). The haptoglobin concentration increased in calves with GI and pulmonary parasites. A significant increase in acetylcholinesterase was observed in calves infected with lungworms. Cholesterol, triglycerides, HDL, and LDL concentrations decreased but lipase concentration increased in calves with GI parasites. Therefore, this paper provides an overview of the biochemical effects produced by nematode parasites in calves in field conditions. These findings in calves without any evident clinical signs of disease could provide an indication of GI parasites and lungworm infection, especially in an endemic area for these parasites.

Seasonal distribution of gastrointestinal nematode infections in sheep in a semiarid region, northeastern Brazil / Distribuição sazonal de infecção por nematóides gastrintestinais em ovinos em área semiárida, nordeste do Brasil

The objective of this study was to determine the seasonal distribution and gastrointestinal nematode parasite load in crossbred Santa Inês tracer lambs, and to correlate the rainfall during the study period with occurrences of parasitic infections. Sixty-four male tracer lambs between the ages of four and eight months were used in the study. Two tracer lambs were inserted into the herd every 28 days to determine the pattern of infective larvae available in the environment. Variation in the fecal egg count (FEC) of nematodes was observed at the study site, with many samples containing undetectable parasite loads during the dry season. The larvae identified in coprocultures were Haemonchus sp., Trichostrongylus sp., Cooperia sp., Strongyloides sp. and Oesophagostomum sp. The nematodes recovered at necropsy were Haemonchus contortus, Trichostrongylus colubriformis, Cooperia punctata, C. pectinata, Trichuris sp., Oesophagostomum sp. and Skrajabinema ovis. The total number of larvae and the total number of immature and adult forms recovered from the tracers showed seasonal distributions that significantly correlated with the amount of rainfall received that month (p value ≅ 0.000 in all cases ). The species H. contortus was predominant in the herd and should be considered to be main pathogenic nematode species in these hosts under these conditions.

O objetivo deste estudo foi determinar a distribuição sazonal e a carga parasitária de nematóides gastrintestinais em cordeiros traçadores, mestiços da raça Santa Inês, e relacionar a ocorrência dessas infecções com a variável chuva no mês. Foram utilizados 64 animais, machos, com idade variando entre quatro e oito meses. Em intervalos de 28 dias, dois traçadores foram inseridos no rebanho para determinar o padrão de disponibilidade de larvas infectantes no ambiente. Variação na contagem de ovos por grama (OPG) de nematóides foi observada no local do estudo, com alta frequência de amostras com carga parasitária indetectável no período seco. Das coproculturas foram identificadas larvas de Haemonchus sp., Trichostrongylus sp., Cooperia sp.,Strongyloides sp. e Oesophagostomum sp. Os nematóides recuperados à necropsia foram Haemonchus contortus, Trichostrongylus colubriformis, Cooperia punctata, C. pectinata, Trichurissp., Oesophagostomum sp. e Skrajabinema ovis. O total de larvas, de formas imaturas e de adultos recuperados dos traçadores, mostraram distribuição sazonal significativamente relacionada com a ocorrência de chuva no mês (valor-p ≅ 0,000, para todos os casos, ). A espécie H. contortus foi predominante no rebanho e deve ser considerada a espécie de nematóide mais importante nesses hospedeiros, sob as condições do estudo.

Seasonal distribution of gastrointestinal nematode infections in sheep in a semiarid region, northeastern Brazil

The objective of this study was to determine the seasonal distribution and gastrointestinal nematode parasite load in crossbred Santa Inês tracer lambs, and to correlate the rainfall during the study period with occurrences of parasitic infections. Sixty-four male tracer lambs between the ages of four and eight months were used in the study. Two tracer lambs were inserted into the herd every 28 days to determine the pattern of infective larvae available in the environment. Variation in the fecal egg count (FEC) of nematodes was observed at the study site, with many samples containing undetectable parasite loads during the dry season. The larvae identified in coprocultures wereHaemonchus sp., Trichostrongylus sp.,Cooperia sp., Strongyloides sp. andOesophagostomum sp. The nematodes recovered at necropsy were Haemonchus contortus, Trichostrongylus colubriformis, Cooperia punctata, C. pectinata, Trichuris sp.,Oesophagostomum sp. and Skrajabinema ovis. The total number of larvae and the total number of immature and adult forms recovered from the tracers showed seasonal distributions that significantly correlated with the amount of rainfall received that month (p value 0.000 in all cases ). The species H. contortus was predominant in the herd and should be considered to be main pathogenic nematode species in these hosts under these conditions.

O objetivo deste estudo foi determinar a distribuição sazonal e a carga parasitária de nematóides gastrintestinais em cordeiros traçadores, mestiços da raça Santa Inês, e relacionar a ocorrência dessas infecções com a variável chuva no mês. Foram utilizados 64 animais, machos, com idade variando entre quatro e oito meses. Em intervalos de 28 dias, dois traçadores foram inseridos no rebanho para determinar o padrão de disponibilidade de larvas infectantes no ambiente. Variação na contagem de ovos por grama (OPG) de nematóides foi observada no local do estudo, com alta frequência de amostras com carga parasitária indetectável no período seco. Das coproculturas foram identificadas larvas de Haemonchus sp.,Trichostrongylus sp., Cooperia sp.,Strongyloides sp. e Oesophagostomum sp. Os nematóides recuperados à necropsia foram Haemonchus contortus,Trichostrongylus colubriformis, Cooperia punctata, C. pectinata, Trichurissp., Oesophagostomum sp. e Skrajabinema ovis. O total de larvas, de formas imaturas e de adultos recuperados dos traçadores, mostraram distribuição sazonal significativamente relacionada com a ocorrência de chuva no mês (valor-p 0,000, para todos os casos, ). A espécie H. contortus foi predominante no rebanho e deve ser considerada a espécie de nematóide mais importante nesses hospedeiros, sob as condições do estudo.

Controle biológico de tricostrongilídeos (Nematoda: Trichostrongyloidea) gastrintestinais de bovinos pelo fungo Monacrosporium sinense / Biological control of gastrointestinal trichostrongylids (Nematoda: Trichostrongyloidea) of cattle by pellets of Monacrosporium sinense

Avaliou-se a resistência do fungo nematófago Monacrosporium sinense (isolado SF 470) em passar pelo trato gastrintestinal de bovinos e testou-se sua capacidade predatória sobre larvas infectantes de tricostrongilídeos após a passagem. Cem gramas de péletes formulados em matriz de alginato de sódio do isolado fúngico de M. sinense foram administrados, por via oral (VO), a dois bezerros mestiços holandês×zebu de seis meses de idade. Para o controle utilizaram-se dois outros animais, de igual padrão, aos quais foram administrados 100g de péletes, VO, livre do isolado fúngico. Amostras fecais, coletadas nos tempos de 12h, 18h, 24h, 48h, 72h e 96h após os tratamentos, foram acondicionadas em placas de Petri e em coproculturas a 25ºC por 15 dias. Houve redução (P<0,05) no número de larvas infectantes de Cooperia spp. e Haemonchus spp. nos animais tratados em relação ao grupo-controle. A diferença ao final do experimento foi de 69,9% nas placas e 61,3% nas coproculturas. O fungo M. sinense demonstrou ser efetivo no controle de larvas infectantes de Cooperia spp e Haemonchus spp em condições de laboratório.(AU)

This study aimed to evaluate the viability of the predatory fungi Monacrosporium sinense (SF 470 isolate) to prey infective trichostrongylids larvae of cattle after the test of passage through the gastrointestinal tract. One hundred grams of pellets with the isolate of M. sinense were orally administered to two six-month-old holstein×zebu crossbred calves. Two similar animals that orally received 100g of pellets without the fungal isolate were used as control. Fecal samples collected at 12, 18, 24, 48, 72 and 96 hours after the treatments were allocated in Petri dishes and in fecal cultures and incubated for 15 days at 25ºC. There was significant reduction (P<0.05) of the average number of infective larvae of Cooperia spp. and Haemonchus spp. in the animals treated with the fungus when compared to the control calves. At the end of the experiment, the differences were 69.9% in the Petri dishes and 61.3% in the fecal cultures. The fungi M. sinense was effective in the control of infective gastrointestinal trichostrongylids larvae of cattle in laboratory conditions.(AU)