Epidemiology of Ostertagia ostertagi in warm temperate regions of the United States

摘要: Abstract For many years our general knowledge on the epidemiology of Ostertagia ostertagi in U.S.A. was based research conducted Scotland and England. During last 10 years, epidemiologic investigations O. other gastrointestinal nematodes cattle have been various sections Canada. Definite seasonal patterns larval inhibition demonstrated, but occurrences Type I II clinical entities not adequately described associated with parasite. All information to present time suggests that there are differences ostertagiasis a north south plane, occurring during autumn spring parts west. Under environmental management conditions those regions where is significant summer dominant season, some minimal numbers inhibition-prone may be acquired winter. However, early pre-Type phaphase (acquisition larvae) begins late winter reaches peak levels spring. From January April, young between weaning 16 months age affected by disease. Pasture transmission basically ceases from into consistent high temperature alternating wet dry periods. through (occasionally earlier), disease possible primarily yearling also order cattle. September October greatest prevalence. The probability effects occurring, i.e. ranging mild signs production loss acute deaths, dictated worms characteristics maturation inhibited larvae, which turn influenced current weather factors conditions, as well previous