The unpredictable epidemiology of Dictyocaulus viviparus lungworm infection of cattle

Together, helminth parasites are the most important animal health constraint to global ruminant livestock production. Better control of gastrointestinal and lungworm nematodes (and liver flukes) in Irish and UK cattle is a priority to meet the need for food security through efficient livestock production. Persistent acting macrocyclic lactone anthelmintics are convenient to use and highly effective against the main gastrointestinal roundworm parasites of cattle, Ostertagia ostertagi. Most cattle farmers worldwide depend upon the use of macrocyclic lactone anthelmintics for the control of nematode parasites, creating a scenario whereby global ruminant livestock production would be untenable without these drugs. Macrocyclic lactone anthelmintic treatment programmes aimed at the control of O ostertagi sometimes create opportunities for completion of the life cycles of other parasites, such as Cooperia spp and Nematodirus helvetianus gastrointestinal worms, and Dictyocaulus viviparus lungworms. Consequently, in many parts of Ireland and the UK, D viviparus has become the major parasitic roundworm challenge to cattle production.