Next-generation molecular-diagnostic tools for gastrointestinal nematodes of livestock, with an emphasis on small ruminants: a turning point?

Abstract

Parasitic nematodes of livestock have major economic impact worldwide. Despite the diseases caused by these nematodes, some advances towards the development of new therapeutic agents and attempts to develop effective vaccines against some of them, there has been limited progress in the development of practical diagnostic methods. The specific and sensitive diagnosis of parasitic nematode infections of livestock underpins effective disease control, which is now particularly important given the problems associated with anthelmintic resistance in parasite populations. Traditional diagnostic methods have major limitations, in terms of sensitivity and specificity. This chapter provides an account of the significance of parasitic nematodes (order Strongylida), reviews conventional diagnostic techniques that are presently used routinely and describes advances in polymerase chain reaction (PCR)-based methods for the specific diagnosis of nematode infections. A particular emphasis is placed on the recent development of a robotic PCR-based platform for high-throughput diagnosis, and its significance and implications for epidemiological investigations and for use in control programmes.

Keywords: Biotechnology; Diagnosis; Livestock; Molecular biology; Parasitic nematodes.

Figure 4.1

Life cycle representing gastrointestinal nematodes (order Strongylida) of small ruminants. First-, second- and third-stage larvae (L1, L2 and L3, respectively) are free-living in the environment. The fourth larval (L4) and adult stages (dioecious) are parasitic in the gastrointestinal tract of the ruminant host.

Figure 4.2

Relationship among host, parasites and environment, and factors that affect parasite control.

Figure 4.3

Third-stage larvae (L3s) of key species of gastrointestinal nematodes of sheep, encountered following larval culture (LC).