Entrocasso C M
Departamento de Producción Animal, INTA-Balcarce, Argentina.
Vet Parasitol. 1988 Feb;27(1-2):59-65. doi: 10.1016/0304-4017(88)90061-1.
Gastrointestinal parasitism has been recognized by practitioners as the most common disease in beef cattle, mainly in weaning calves and fattening steers. Among the different genera, Ostertagia ostertagi is the predominant parasite in the temperate climate, in which the major beef and dairy cattle area of South America is situated. Outbreaks of Type I ostertagiasis are usually seen after weaning time (autumn-winter) when larvae counts are high and food availability is low. The development of the disease is rapidly established and 15-30 kg are lost in 30-50 days. Epidemiological studies have demonstrated a fast evolution of parasite eggs to larvae (L3) in summer (1 week or less), evolution being 30-45 days during winter. Inhibition O. ostertagi occurs during spring (September-December) and development resumes in late summer and early autumn. The production effect is seen as a significant reduction in body weight gain and occasionally clinical Type II ostertagiasis appears. A similar epidemiological pattern of inhibition of Ostertagia sp. has been recorded in Uruguay and temperate areas in southern Brazil.
胃肠道寄生虫病已被从业者认定为肉牛最常见的疾病，主要发生在断奶犊牛和育肥牛中。在不同的属中，奥斯特他线虫是温带气候下的主要寄生虫，南美洲主要的肉牛和奶牛产区就位于温带地区。I型奥斯特他线虫病通常在断奶期（秋冬）后出现，此时幼虫数量多而食物供应少。该病发展迅速，30至50天内体重会减轻15至30千克。流行病学研究表明，寄生虫卵在夏季（1周或更短时间）内可快速发育为幼虫（L3），而在冬季则需要30至45天。奥斯特他线虫的滞育发生在春季（9月至12月），发育在夏末和初秋恢复。生产效应表现为体重增加显著减少，偶尔会出现临床II型奥斯特他线虫病。在乌拉圭和巴西南部的温带地区也记录到了类似的奥斯特他线虫滞育的流行病学模式。
