Haemonchus contortus: A multiple-resistant Brazilian isolate and the costs for its characterization and maintenance for research use

The aim of this work was to determine the resistance level of Haemonchus contortus isolated from the Santa Inês flock of the Embrapa (Brazilian government's Agricultural Research Company), Southeast Livestock Unit (CPPSE), as well as to determine costs of characterizing and maintaining this isolate in host donors. Forty-two male Santa Inês lambs were experimentally infected with 4000 H. contortus infective larvae of the field isolate of CPPSE, called Embrapa2010, and divided into six treatment groups, which received triclorfon, albendazol plus cobalt sulfate, ivermectin, moxidectin, closantel and levamisole phosphate, as well as a negative control group (water). Egg per gram (EPG) counts were performed at 0, 3, 7, 10 and 14. days post treatment when the animals were slaughtered for parasite count. The data were analyzed using the RESO statistical program, considering anthelmintic resistance under 95% of efficacy. EPG and worm count presented a linear and significant relation with 94% determination coefficient. The susceptibility results obtained by RESO through both criteria (EPG and worm count) were equal, except for closantel, showing that the isolate Embrapa2010 is resistant to benzimidazoles, macrocyclic lactones and imidazothiazoles. The need of a control group did not appear to be essential since the result for susceptibility in the analyses with or without this group was the same. Suppression in egg production after treatment did not occur in the ivermectin and moxidectin groups. In the control group, the establishment percentage was just 12.5 because of the low number of third-stage larvae, resistance (innate and infection immunity) of the animals studied plus good nutrition. Drug classes presented similar efficacy between adults and immature stages. The costs for isolate characterization were calculated for 42 animals during 60. days. The total cost based on local market rates was approximately US$ 8000. The precise identification of Brazilian isolates and their establishment in host donors would be useful for laboratorial anthelmintic resistance diagnoses through in vitro tests, which has an annual cost of approximately US$ 2500 for maintenance in host donors. © 2012 Elsevier B.V.

Effects of macrocyclic lactones on the reproductive parameters of engorged Rhipicephalus (Boophilus) microplus females detached from experimentally infested cattle

The present study therefore assessed the deleterious effects of MLs (ivermectin, abamectin, doramectin and moxidectin) on the reproductive parameters of engorged Rhipicephalus (Boophilus) microplus females that naturally detached from experimentally infested cattle in two experiments. The following reproductive parameters of engorged female ticks were analyzed: female weight, egg mass weight, percentage of hatchability, percentage of reduction in oviposition, percentage of reduction in hatchability, reproductive efficiency and percent control/efficacy of formulations with respect to reproductive parameters. In the experiment I, statistical analysis of the data grouped into 5-days intervals revealed that pour-on application of abamectin (500. mcg/kg) had significantly (p≤. 0.05) reduced engorged female weight, egg mass weight and percent hatchability on days 6-15, 6-20 and 11-20 post-treatment (p. t.) compared to the respective data for detached and pre-selected engorged females in the control group. The abamectin, demonstrated 33.41% of reduction in oviposition, 6.77% in hatchability and abamectin efficacy was of 13.99%. In the experiment II, statistically significant reductions (p≥. 0.05) were observed in animals treated subcutaneous with ivermectin (630. mcg/kg), doramectin (700. mcg/kg) and moxidectin (1000. mcg/kg) relative to the control for days 6-40, 6-48 and 6-40 p. t., respectively. Ivermectin reduced hatchability only on days 16-20 p. t., whereas doramectin significantly reduced (p≤. 0.05) hatchability on days 6-10 and 16-35 p. t. For moxidectin, deleterious effects on hatchability were observed on days 16-35 p. t. The percent reductions in oviposition of engorged female ticks were 46.31%, 62.17% and 61.02% with ivermectin, doramectin and moxidectin treatments, respectively. The percent efficacy of the formulations on the reproductive parameters of engorged female ticks was 21.22% for ivermectin, 36.03% for doramectin and 35.45% for moxidectin. Among the MLs assessed, doramectin and moxidectin had the highest acaricidal efficacies and the most deleterious effects on the reproductive parameters of engorged R. (B.) microplus females. However, future studies will be necessary to assess the extent to which these effects, along with acaricidal activity, can be used to control the ectoparasite in cattle. © 2013 Elsevier Inc..

Caracterização da resistência a anti-helmíntico de isolados de Haemonchus contortus e trichostrongylus colubriformis orieundo de ovinos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação comparativa de duas formulações anti-helmínticas em caprinos naturalmente infectados

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Farmacocinética e eficácia endectocida de uma nova formulação contendo doramectina 3,5% em bovinos

Pós-graduação em Medicina Veterinária - FCAV

Eficácia anti-helmíntica comparativa da associação albendazole, levamisole e ivermectina à moxidectina 1% em ovinos naturalmente infectados por nematódeos gastrintestinais

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influência do parasitismo e da suplementação no desenvolvimento ponderal de novilhos mestiços Angus-Nelore e da raça Guzerá

Pós-graduação em Zootecnia - FEIS

Diagnóstico de resistência anti-helmíntica em bovinos

Pós-graduação em Medicina Veterinária - FMVZ

Resistência anti-helmíntica em equinos na Região Oeste do Estado de São Paulo

Pós-graduação em Ciência e Tecnologia Animal - FEIS

Diagnóstico molecular da alteração mutagênica nt 230 (del4) no gene MDR1 em cães

P-glycoprotein is an adenosine triphosphate (ATP)-driven drug efflux carrier responsible for transport of xenobiotics and multiple classes of drugs, many usually use in veterinary medicine. Encoded by MDR1 gene, also referred to as ABCB1, located on chromosome 14, is expressed in many tissues with secretory or excretory functions, such as liver, kidney and intestine, where it limits drug absorption from the gut and promotes drug excretion into the bile and urine of their substrates. In 2001, a 4 base pair gene deletion mutation in the canine MDR1 gene was identified as MDR1-1▲, ABCB1-1▲, MDR1 MDR1 nt 230 (del4) and associated with an non-functional Pglycoprotein. The clinical correlation is the (hyper) sensitivity of certain dogs breeds, mostly collies, to a few classes of drugs such as anticancer drugs (doxorubicin, vincristine, vinblastine), immunosuppressants (cyclosporine), antiparasitic drugs (ivermectin, moxidectin), steroids hormones (aldosterone, cortisol, dexamethasone), antimicrobial agents (tetracycline, doxycycline, levofloxacin, ketoconazole, itraconazole), analgesics (morphine, methadone), antidiarrheals (loperamide), antiepileptic agents (phenothiazine), cardiac drugs (digoxin, diltiazem, verapamil, talinolol) and others. Dogs with homozygous MDR1 nt 230 (del4) MDR1 mutations (MDR1 - / -) have a higher predisposition to intoxication with substrates of P-gp than heterozygous (MDR1 + / -) and these are more likely than dogs homozygous nonmutant (MDR1 +/ +). After the identification of nt230 (del4) mutation, several molecular techniques have been developed for identification of mutant animals as a diagnostic method. The importance of molecular diagnosis is, after the identification of mutant animals, establish treatment protocols safe, exclude this animals from reproduction (genetic selection program) and investigating the history of adverse drugs reactions... (Complete abstract click electronic access below)

Diagnosis of anthelmintic resistance in cattle in Brazil: a comparison of different methodologies

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Dermatobia hominis: potencial risk of resistance to macrocyclic lactones

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Susceptibility of helminth species from horses against different chemical compounds in Brazil

By means of parasitological necropsies, the present study aimed to evaluate, in six experiments, the degree of susceptibility or resistance of different helminth species which naturally infect horses to ivermectin 0.2mg/kg, abamectin 0.2mg/kg, moxidectin 0.4mg/kg, trichlorfon 35mg/kg, ivermectin 0.2mg/kg+praziquantel 2.5mg/kg, abamectin 0.2mg/kg+praziquantel 2.5mg/kg and ivermectin 0.2mg/kg+6.6 mg/kg pyrantel. At experimental day zero, the horses were allocated to treatment groups based on average counts of strongylid eggs per gram of feces (EPG) obtained on days -3, -2 and -1. Oxyuris sp. infections were confirmed as positive or negative. All the animals in the six experiments were naturally infected by this helminth species. Each group (control or treated) consisted of six animals. All the assessed Habronema muscae populations analyzed were susceptible to ivermectin, abamectin and moxidectin. Of the six Trichostrongylus axei populations, four were susceptible to ivermectin, abamectin, moxidectin, trichlorfon and ivermectin+praziquantel, and two were resistant to abamectin+praziquantel and ivermectin+pyrantel. Both Strongyloides westeri populations analyzed were susceptible to ivermectin, abamectin, moxidectin and abamectin+praziquantel. For O. equi, resistance was found in four different populations treated with ivermectin, abamectin, moxidectin, trichlorfon and ivermectin+praziquantel. Only combinations of abamectin+praziquantel and ivermectin+pyrantel were effective against this parasite species. All the large strongyles diagnosed in the present study (Strongyus edentatus, Strongyus vulgaris and Triodontophorus serratus) were susceptible to all the chemicals tested, with the exception of trichlorfon. Of the Cyathostominae populations, one was diagnosed as resistant to ivermectin and another to trichlorfon. The remaining populations from this nematode group were considered to be sensitive to ivermectin, abamectin, moxidectin, ivermectin+praziquantel, abamectin+praziquantel and ivermectin+pyrantel. New studies should be performed in different regions to evaluate the efficacy of trichlorfon in others field populations of helminthes.

Clinical, laboratory and pathological findings in dogs experimentally infected with Angiostrongylus vasorum

The aim of this comparative study was to investigate the development of clinical signs and accompanying haematological, coproscopic and pathological findings as a basis for the monitoring of health condition of Angiostrongylus vasorum infected dogs. Six beagles were orally inoculated with 50 (n=3) or 500 (n=3) A. vasorum third stage larvae (L3) obtained from experimentally infected Biomphalaria glabrata snails. Two dogs were treated with moxidectin/imidacloprid spot-on solution and two further dogs with an oral experimental compound 92 days post infection (dpi), and were necropsied 166 dpi. Two untreated control dogs were necropsied 97 dpi. Prepatency was 47-49 days. Dogs inoculated with 500 L3 exhibited earlier (from 42 dpi) and more severe respiratory signs. Clinical signs resolved 12 days after treatment and larval excretion stopped within 20 days in all four treated dogs. Upon necropsy, 10 and 170 adult worms were recovered from the untreated dogs inoculated with 50 and 500 L3, respectively. Adult worms were also found in two treated dogs, in the absence of L1 or eggs. Despite heavy A. vasorum infection load and severe pulmonary changes including vascular thrombosis, only mild haematological changes were observed. Eosinophilia was absent but the presence of plasma cells was observed. Neutrophilic leucocytes showed a transient increase but only after treatment. Signs for coagulopathies were slight; nevertheless coagulation parameters were inoculation dose dependent. Ten weeks after treatment pulmonary fibrosis was still present. Infections starting from 50 L3 of A. vasorum had a massive impact on lung tissues and therefore on the health of affected dogs, particularly after prepatency, although only mild haematological abnormalities were evident.

Factors that influence the prevalence of acaricide resistance and tick-borne diseases

This manuscript provides a summary of the results presented at a symposium organized to accumulate information on factors that influence the prevalence of acaricide resistance and tick-borne diseases. This symposium was part of the 19th International Conference of the World Association for the Advancement of Veterinary Parasitology (WAAVP), held in New Orleans, LA, USA, during August 10-14, 2003. Populations of southern cattle ticks, Boophilus microplus, from Mexico have developed resistance to many classes of acaricide including chlorinated hydrocarbons (DDT), pyrethroids, organ ophosphates, and formamidines (amitraz). Target site mutations are the most common resistance mechanism observed, but there are examples of metabolic mechanisms. In many pyrethroid resistant strains, a single target site mutation on the Na+ channel confers very high resistance (resistance ratios: >1000x) to both DDT and all pyrethroid acaricides. Acetylcholine esterase affinity for OPs is changed in resistant tick populations. A second mechanism of OP resistance is linked to cytochrome P450 monooxygenase activity. A PCR-based assay to detect a specific sodium channel gene mutation that is associated with resistance to permethrin has been developed. This assay can be performed on individual ticks at any life stage with results available in a few hours. A number of Mexican strains of B. microplus with varying profiles of pesticide resistance have been genotyped using this test. Additionally, a specific metabolic esterase with permethrin-hydrolyzing activity, CzEst9, has been purified and its gene coding region cloned. This esterase has been associated with high resistance to permethrin in one Mexican tick population. Work is continuing to clone specific acetylcholinesterase (AChE) and carboxylesterase genes that appear to be involved in resistance to organophosphates. Our ultimate goal is the design of a battery of DNA- or ELISA-based assays capable of rapidly genotyping individual ticks to obtain a comprehensive profile of their susceptibility to various pesticides. More outbreaks of clinical bovine babesisois and anaplasmosis have been associated with the presence of synthetic pyrethroid (SP) resistance when compared to OP and amidine resistance. This may be the result of differences in the temporal and geographic patterns of resistance development to the different acaricides. If acaricide resistance develops slowly, herd immunity may not be affected. The use of pesticides for the control of pests of cattle other than ticks can affect the incidence of tick resistance and tick-borne diseases. Simple analytical models of tick- and tsetse-bome diseases suggest that reducing the abundance of ticks, by treating cattle with pyrethroids for example, can have a variety of effects on tick-bome diseases. In the worst-case scenario, the models suggest that treating cattle might not only have no impact on trypanosomosis but could increase the incidence of tick-bome disease. In the best-case, treatment could reduce the incidence of both trypanosomosis and tick-bome diseases Surveys of beef and dairy properties in Queensland for which tick resistance to amitraz was known were intended to provide a clear understanding of the economic and management consequences resistance had on their properties. Farmers continued to use amitraz as the major acaricide for tick control after the diagnosis of resistance, although it was supplemented with moxidectin (dairy farms) or fluazuron, macrocyclic lactones or cypermethrin/ chlorfenvinphos. (C) 2004 Published by Elsevier B.V.