Bovine coccidiosis: Retrospective study in Central Argentina

Bovine coccidiosis is a gastrointestinal disease of cattle with worldwide distribution caused by protozoan parasites of the genus Eimeria. Bovine coccidiosis mainly affects calves worldwide, frequently triggered by stressful management events, with consequent impact on cattle production and economic outcome. Most reports are from subtropical to tropical regions, where environmental conditions favor continuous oocyst survival and dissemination. In the present study we describe 63 outbreaks of bovine coccidiosis that occurred in the central region of Argentina, recorded by the Veterinary Specialized Diagnostic Service (SDVE) INTA Balcarce. Epidemiological information and clinical signs were registered, and 43 necropsies from 35 outbreaks were performed, followed by histopathological evaluation. In addition, 192 fecal samples from 52 outbreaks were analyzed for oocysts per gram of feces and eggs per gram of feces quantification, for identification of Eimeria spp. and gastrointestinal nematodes, respectively. Outbreaks occurred throughout the year but occurred significantly more often in autumn and predominantly in cow-calf systems. Calves younger than 12 months were the most affected group, with outbreaks commonly associated to stress factors such as weaning, recent transportation, and overcrowding. Mean morbidity and mortality were 5.6 % and 2.6 %, respectively. Affected animals generally presented diarrhea containing blood and/or mucosal debris and nervous signs were frequently recorded. Gross findings included multifocal to coalescing segmental hemorrhages in the large intestine. Histopathological findings revealed diffuse necrotizing and mononuclear enteritis with abundant intraepithelial parasitic structures consistent with Eimeria zuernii and E. bovid. Oocyst counts in feces varied widely, from 0 up to 2,240,000 per gram. Overall, a high prevalence of bovine coccidiosis in central Argentina was evident, mostly under suboptimal husbandry conditions. The findings provide valuable insights into the epidemiology and pathology of the disease and may contribute to more effective diagnostic approaches and control strategies in cattle production systems.