Cargando…

Controlled efficacy trial confirming toltrazuril resistance in a field isolate of ovine Eimeria spp.

BACKGROUND: Coccidiosis due to Eimeria spp. infections in lambs causes increased mortality and substantial production losses, and anticoccidials are important for control of the infection. Anticoccidial resistance has been reported in poultry and swine, and we recently described reduced toltrazuril...

Descripción completa

Detalles Bibliográficos
Autores principales: Odden, Ane, Enemark, Heidi L., Ruiz, Antonio, Robertson, Lucy J., Ersdal, Cecilie, Nes, Silje K., Tømmerberg, Vibeke, Stuen, Snorre
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2018
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6034276/
https://www.ncbi.nlm.nih.gov/pubmed/29976240
http://dx.doi.org/10.1186/s13071-018-2976-4
_version_ 1783337846630776832
author Odden, Ane
Enemark, Heidi L.
Ruiz, Antonio
Robertson, Lucy J.
Ersdal, Cecilie
Nes, Silje K.
Tømmerberg, Vibeke
Stuen, Snorre
author_facet Odden, Ane
Enemark, Heidi L.
Ruiz, Antonio
Robertson, Lucy J.
Ersdal, Cecilie
Nes, Silje K.
Tømmerberg, Vibeke
Stuen, Snorre
author_sort Odden, Ane
collection PubMed
description BACKGROUND: Coccidiosis due to Eimeria spp. infections in lambs causes increased mortality and substantial production losses, and anticoccidials are important for control of the infection. Anticoccidial resistance has been reported in poultry and swine, and we recently described reduced toltrazuril efficacy in ovine Eimeria spp. in some Norwegian sheep farms using a newly developed faecal oocyst count reduction test (FOCRT). The aim of the present study was to use a controlled efficacy trial to assess the efficacy of toltrazuril against a field isolate suspected of being resistant. METHODS: Twenty lambs, 17–22 days old and raised protected against exposure to coccidia, were infected with a field isolate of 100,000 Eimeria spp. oocysts. This isolate was obtained from a farm with a previously calculated drug efficacy of 56% (95% confidence interval: -433.9 to 96.6%). At day 7 post-infection, 10 of the lambs were orally treated with 20 mg/kg toltrazuril (Baycox Sheep vet., Bayer Animal Health), while the other 10 lambs (controls) were given physiological saline. Clinical examinations were conducted, and weight gains recorded. Daily faecal samples were scored for diarrhoea on a scale from 1 to 5, and oocyst excretion was determined using a modified McMaster technique. Oocysts were morphologically identified to species level. At 17–24 days post-infection, the lambs were euthanized and necropsied. RESULTS: The tested Eimeria isolate was resistant against toltrazuril, and resistance was seen in both pathogenic and non-pathogenic species. In addition, no significant differences in faecal score, growth, gross pathology or histological changes were identified between the two groups. The pathogenic E. ovinoidalis was the dominant species, and no significant difference in the individual prevalence of E. ovinoidalis post-treatment was found between treated (66.9%) and control lambs (61.9%). Other species identified included E. crandallis/weybridgensis, E. parva, E. marsica, E. faurei, E. pallida, E. ahsata and E. bakuensis. CONCLUSIONS: This study confirms toltrazuril resistance in ovine Eimeria spp.; in addition, the data support the use of FOCRT as an appropriate tool for field evaluation of anticoccidial efficacy. Due to limited anticoccidial treatment alternatives, these findings may have important implications for the sheep industry, particularly in northern Europe. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s13071-018-2976-4) contains supplementary material, which is available to authorized users.
format Online
Article
Text
id pubmed-6034276
institution National Center for Biotechnology Information
language English
publishDate 2018
publisher BioMed Central
record_format MEDLINE/PubMed
spelling pubmed-60342762018-07-12 Controlled efficacy trial confirming toltrazuril resistance in a field isolate of ovine Eimeria spp. Odden, Ane Enemark, Heidi L. Ruiz, Antonio Robertson, Lucy J. Ersdal, Cecilie Nes, Silje K. Tømmerberg, Vibeke Stuen, Snorre Parasit Vectors Research BACKGROUND: Coccidiosis due to Eimeria spp. infections in lambs causes increased mortality and substantial production losses, and anticoccidials are important for control of the infection. Anticoccidial resistance has been reported in poultry and swine, and we recently described reduced toltrazuril efficacy in ovine Eimeria spp. in some Norwegian sheep farms using a newly developed faecal oocyst count reduction test (FOCRT). The aim of the present study was to use a controlled efficacy trial to assess the efficacy of toltrazuril against a field isolate suspected of being resistant. METHODS: Twenty lambs, 17–22 days old and raised protected against exposure to coccidia, were infected with a field isolate of 100,000 Eimeria spp. oocysts. This isolate was obtained from a farm with a previously calculated drug efficacy of 56% (95% confidence interval: -433.9 to 96.6%). At day 7 post-infection, 10 of the lambs were orally treated with 20 mg/kg toltrazuril (Baycox Sheep vet., Bayer Animal Health), while the other 10 lambs (controls) were given physiological saline. Clinical examinations were conducted, and weight gains recorded. Daily faecal samples were scored for diarrhoea on a scale from 1 to 5, and oocyst excretion was determined using a modified McMaster technique. Oocysts were morphologically identified to species level. At 17–24 days post-infection, the lambs were euthanized and necropsied. RESULTS: The tested Eimeria isolate was resistant against toltrazuril, and resistance was seen in both pathogenic and non-pathogenic species. In addition, no significant differences in faecal score, growth, gross pathology or histological changes were identified between the two groups. The pathogenic E. ovinoidalis was the dominant species, and no significant difference in the individual prevalence of E. ovinoidalis post-treatment was found between treated (66.9%) and control lambs (61.9%). Other species identified included E. crandallis/weybridgensis, E. parva, E. marsica, E. faurei, E. pallida, E. ahsata and E. bakuensis. CONCLUSIONS: This study confirms toltrazuril resistance in ovine Eimeria spp.; in addition, the data support the use of FOCRT as an appropriate tool for field evaluation of anticoccidial efficacy. Due to limited anticoccidial treatment alternatives, these findings may have important implications for the sheep industry, particularly in northern Europe. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s13071-018-2976-4) contains supplementary material, which is available to authorized users. BioMed Central 2018-07-05 /pmc/articles/PMC6034276/ /pubmed/29976240 http://dx.doi.org/10.1186/s13071-018-2976-4 Text en © The Author(s). 2018 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
spellingShingle Research
Odden, Ane
Enemark, Heidi L.
Ruiz, Antonio
Robertson, Lucy J.
Ersdal, Cecilie
Nes, Silje K.
Tømmerberg, Vibeke
Stuen, Snorre
Controlled efficacy trial confirming toltrazuril resistance in a field isolate of ovine Eimeria spp.
title Controlled efficacy trial confirming toltrazuril resistance in a field isolate of ovine Eimeria spp.
title_full Controlled efficacy trial confirming toltrazuril resistance in a field isolate of ovine Eimeria spp.
title_fullStr Controlled efficacy trial confirming toltrazuril resistance in a field isolate of ovine Eimeria spp.
title_full_unstemmed Controlled efficacy trial confirming toltrazuril resistance in a field isolate of ovine Eimeria spp.
title_short Controlled efficacy trial confirming toltrazuril resistance in a field isolate of ovine Eimeria spp.
title_sort controlled efficacy trial confirming toltrazuril resistance in a field isolate of ovine eimeria spp.
topic Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6034276/
https://www.ncbi.nlm.nih.gov/pubmed/29976240
http://dx.doi.org/10.1186/s13071-018-2976-4
work_keys_str_mv AT oddenane controlledefficacytrialconfirmingtoltrazurilresistanceinafieldisolateofovineeimeriaspp
AT enemarkheidil controlledefficacytrialconfirmingtoltrazurilresistanceinafieldisolateofovineeimeriaspp
AT ruizantonio controlledefficacytrialconfirmingtoltrazurilresistanceinafieldisolateofovineeimeriaspp
AT robertsonlucyj controlledefficacytrialconfirmingtoltrazurilresistanceinafieldisolateofovineeimeriaspp
AT ersdalcecilie controlledefficacytrialconfirmingtoltrazurilresistanceinafieldisolateofovineeimeriaspp
AT nessiljek controlledefficacytrialconfirmingtoltrazurilresistanceinafieldisolateofovineeimeriaspp
AT tømmerbergvibeke controlledefficacytrialconfirmingtoltrazurilresistanceinafieldisolateofovineeimeriaspp
AT stuensnorre controlledefficacytrialconfirmingtoltrazurilresistanceinafieldisolateofovineeimeriaspp