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Lundin, Sara, 2011. Determination of anthelmintic resistance of Haemonchus contortus to three classes of anthelmintics in a Kenyan sheep flock based on results from faecal egg count reduction test. Second cycle, A1N, A1F or AXX ( AXX). Uppsala: SLU, Dept. of Biomedical Sciences and Veterinary Public Health

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Abstract

Haemonchus contortus is the most important bloodsucking gastrointestinal nematode in small ruminants worldwide. It is often controlled by anthelmintics. Even though other methods to control are available, the most efficient way to treat an animal with clinically manifested haemonchosis is to use one of the available broad spectrum anthelmintics: benzimidazoles (BZ), macrocyclic lactones (ML) or imidothiazoles-tetrahydropyromidines or the narrow spectrum drugs salisylanilides or nitrophenols. Anthelmintic resistance (AR) against all groups of anthelmintics in nematode parasites has been reported from many countries, and even multiple AR has been observed. In this study I have investigated the resistance levels to all major classes of broad spectrum anthelmintics in a naturally infected flock of sheep of Red Maasai sheep (RM), Dorper sheep (D) and their offsprings on a research farm in Kenya. Resistance to the BZ albendazole (ALB) and most likely also to the imidothiazole levamisole (LEV) had previously been seen in this flock. Faecal Egg Count Reduction Test (FECRT) was now performed. The efficacy of ALB, IVM and levamisole (LEV) were tested. Faecal egg counts (FEC) and reductions after deworming were analysed according to the AHs used. Accordingly, a total of 88 sheep were divided into three treatment groups per breed or crosses (n=5-7) i.e. the number of sheep subjected to each AH were 27-31 animals. One untreated control group (n=15) was also included in the study. Prior to AH treatment animals were weighed and they were then treated orally by a veterinarian with either of the three substances. In addition, blood and faeces were collected and examined for the packed cell volume (PCV) and the number of parasite eggs per gram of faeces (EPG) both at the day of treatment plus at day 10 and day 22-24 post treatment. Furthermore, nematode larvae were cultured from pooled faeces per group at day 0 and day 10 and larval differential counts were performed. Results showed that the majority of the nematodes were H. contortus both at days 0 and 10. The FECRTs showed efficacy of all three tested substances, between 98 % and 99 % reduction of egg counts per gram faeces, on days 22-24. Thus, there was no resistance against any of the tested substances, even though resistance had been seen only about two years earlier in the same flock.

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Den stora löpmagsmasken, Haemonchus contortus, är den viktigaste gastrointestinala nematoden hos små idisslare och är en blodsugande parasit som finns utbredd över hela världen. Parasiten kontrolleras ofta genom avmaskning. Även om det finns andra metoder att kontrollera H. contortus, är ofta den effektivaste metoden att behandla kliniskt sjuka djur med antihelmintika (AH). Tillgängliga AH på marknaden är benzimidazoler (BZ), makrocykliska laktoner (ML), imidothiazoler-tetrahydropyromidiner eller closantel. Läkemedelsresistens har rapporterats hos H. contortus från många länder, framför allt mot substanser inom gruppen BZ, men även resistens mot ML, levamisol och multipel resistens finns beskriven. Syftet med denna studie var att undersöka läkemedelsresistens hos nematoder i en fårflock med renrasiga Red Maasai- och Dorper-får samt olika korsningar av dessa på en fårfarm i Kenya. Tidigare hade man hos parasiter från denna besättning sett antihelmintikaresistens (AR) mot albendazol (ALB) och med stor sannorlikhet också mot levamisol (LEV). Vi utförde en så kallad ”faecal egg count reduction test” (FECRT) där effekterna av ALB, IVM och LEV testades. Totalt 88 får ingick i studien. Djuren indelades i tre behandlingsgrupper per ras eller korsning (n=5-7). Antalet får som behandlades med respektive AH varierade mellan 27 och 31 djur. En kontrollgrupp (n=15) inkluderades också i studien. Innan avmaskningen vägdes alla får. Därefter behandlades de oralt av en veterinär med någon av de tre substanserna. I samband med detta togs även blod- och avföringsprover som analyserades avseende hematokrit (PCV) respektive antal parasitägg per gram avföring (EPG). Alla får provtogs på samma sätt även 10 och 22-24 dagar efter behandlingen. Äggutskiljningen (FEC) och reduktionen analyserades slutligen med avseende på behandlingen med respektive substans. Även nematodlarver odlades fram från poolade träckprover i samtliga behandlingsgrupper både från dag 0 och 10 varefter differentialräkningar utfördes, och som visade att en majoritet av larverna var H. contortus både dag 0 och dag 10. FECRT visade effekter mellan 98 % och 99 % hos alla de tre testade substanserna. Enligt FECRT fanns det således ingen resistens mot någon av de testade substanserna trots att man sett AR i samma flock endast cirka 2 år tidigare.

Main title:Determination of anthelmintic resistance of Haemonchus contortus to three classes of anthelmintics in a Kenyan sheep flock based on results from faecal egg count reduction test
Authors:Lundin, Sara
Supervisor:Höglund, Johan and Githiori, John
Examiner:Berg, Mikael
Series:Examensarbete (Sveriges lantbruksuniversitet, Fakulteten för veterinärmedicin och husdjursvetenskap, Veterinärprogrammet)
Volume/Sequential designation:2011:52
Year of Publication:2011
Level and depth descriptor:Second cycle, A1N, A1F or AXX
Student's programme affiliation:3050A Veterinary Medicine Programme (admitted before July 1, 2007) 330 HEC
Department:(VH) > Dept. of Biomedical Sciences and Veterinary Public Health
Keywords:Haemonchus contortus, sheep, Kenya, anthelmintic resistance, FECRT
URN:NBN:urn:nbn:se:slu:epsilon-s-794
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-s-794
Subjects:Animal diseases
Language:English
Deposited On:08 Dec 2011 12:37
Metadata Last Modified:20 Apr 2012 14:24

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