Value of present diagnostic methods for gastrointestinal nematode infections in ruminants

In this paper the different options for the diagnosis of gastrointestinal n ematode infections are discussed. Diagnostic tests have a role in confirmin g the clinical diagnosis of parasitic gastroenteritis, but are more importa nt for herd health monitoring of nematode infections, in particular for cat tle. Therefore, emphasis is placed on discussing the available diagnostic p arameters on their usefulness for that purpose. For clinical diagnosis the clinical signs, combined with the history of the animals is usually suffici ent and a laboratory confirmation is not required. Faecal egg counts are, w ith two exceptions, not suitable for confirmation of the clinical diagnosis , because correlation between faecal egg counts and infection levels is usu ally low. These exceptions are the diagnosis of haemonchosis in small rumin ants and the detection of anthelmintic resistance. This also limits the val ue of DNA-based tests of faecal material; even quantitative tests of nemato de species specific DNA will have little value for diagnosis and monitoring . Pasture larval counts and worm counts are useful parameters for basic epi demiological studies on nematode infections. How-ever, they are too laborio us to be used for either routine diagnosis or monitoring. Blood parameters, such as gastrin and pepsinogen and serology are valuable tools for diagnos is. Pepsinogen and ELISAs based on recombinant proteins show most promise a s parameters for herd health monitoring. However, extensive epidemiological studies are still needed before these parameters can be implemented in rou tine herd health monitoring schemes for parasitic gastroenteritis.