Anticoccidial resistance, development of immunity and alternative control strategy in Norwegian lambs

Coccidiosis in Norwegian lambs Protozoan parasites in genus Eimeria may cause severe clinical disease (coccidiosis (syn. eimeriosis)) in Norwegian lambs, typically 2-3 weeks after turnout on spring pasture. The present project investigated possible anticoccidial drug resistance (ACR), by describing the current use of anticoccidial drugs, investigate possible ACR via establishment of both in vitro and in vivo test methods for evaluation of anticoccidial resistance. The results indicate that several farmers treat against coccidiose without knowing if they have any problem with coccidia and often without a laboratory-confirmed diagnosis, In addition, several farmers do not follow the recommended guidelines concerning treament procedures, which may lead to unnecessary treatment. A field method (FOCRT) and an in vivo method (CET) were established to test for resistence against Eimeria. A FOCRT study involving farms from all over Norway indicate that ACR may occur on several farm, of which resistence was verified in one farm using CET. The investigation so far indicates that several farms experience reduced efficacy of treatment due to treatment at the wrong time compared to the time of infection. In the future, it is crucial to know then the infection occur - indoors or outdoors. This is necessary information to obtain in order to evaluate the occurrence of ACR. The project also investigated if iron treatment of newborn lambs could protect against coccidiosis. However, the result show no effect of iron supplementation on oocyst excretion or weight gain. In summary, the project described the first evidence of toltrazuril-resistence against Eimeria-infection in lambs, and established methods for future ACR-testing.

Prosjektet har etablert metoder for påvisning av resistens mot koksidie-midler (egentlig mot toltrazuril) hos lam. Dette vil gjøre det lettere å undersøke årsaken til manglende effelt av behandling, om det skyldes feil behandlingstidspunkt, resistens mot koksidie-midler eller andre faktorer. Prosjektet har også avslørt at resistens mot toltrazuril forekommer her i landet. I tillegg har prosjektet også kartlagt at flere bønder ikke følger anbefalte rettningslinjer for korrekt medisinbehandling. Prosjektet har etablert svært nyttige redskaper for kartlegging av manglende effekt av koksidie-behandling både her i landet, men også til bruk i utlandet. Resultatet av undersøkelsen vil derfor ha stor betydning for sauenæringa med tanke på korrekt parasittbehandling og forbygging av resistens mot koksidie-midler

Protozoan parasites in genus Eimeria may cause severe clinical disease (coccidiosis (syn. eimeriosis)) in Norwegian lambs, typically 2-3 weeks after turnout on spring pasture. Impaired weight gain and in some cases death represent a considerable economic loss for the sheep farmers. Coccidiosis is regarded as an emerging and potentially devastating problem by the Norwegian sheep industry. In our country, approximately 50 % of the sheep flocks use prophylactic or metaphylactic treatment with an anticoccidial drug in order to control coccidiosis. Anticoccidial drug resistance (ACR) against sheep-specific Eimeria will therefore represent a great threat to animal welfare and limitations in achieving economic and sound sheep production. Earlier treatment studies in Norway indicate the presence of resistant Eimeria species. In addition, an increased number of sheep flocks which experience problems in controlling coccidiosis have been observed during recent years. The present project will investigate possible anticoccidial drug resistance and improve the prevention of coccidiosis in the Norwegian sheep farming industry, by describing the current use of anticoccidial drugs, investigate possible ACR, establish in vitro and in vivo test methods for evaluation of anticoccidial resistance, investigate variations in the development of immunity between different treatment strategies and determine whether iron supplementation can reduce the risk of clinical coccidiosis in lambs. Prevention of development and spread of ACR is crucial to ensure good animal welfare, an economically sustainable lamb production and utilisation of grazing areas. A strong and innovative research group involving both national and international partners will increase the knowledge regarding coccidiosis not only in sheep, but may also contribute with knowledge important to all farmers with intensive production systems where coccidiosis occurs.