Risk factors for bovine cysticercosis in a large commercial South African cattle feedlot

Abstract

Taeniid tapeworms have very simple lifecycles with the adult stage developing in the intestine of the obligate human host, after the ingestion of viable cysticerci in raw/undercooked meat. Bovine Cysticercosis follows epidemic outbreak patterns in a cattle feedlot. These peaks/point source epidemics have been related to contaminated feed or water, and/or to specific infected workers. Taeniosis in humans caused by T. saginata is a relatively mild condition; easy to control through regular deworming and improved personal sanitation practices, while positive cysticercosis carcasses caused by T. saginata result in very costly decontamination processes through freezing, that have a huge negative financial impact on the beef industry. This study is a Retrospective Analysis of all abattoir data from 645 634 Karan Beef feedlot cattle slaughtered during 1 January 2009 to 31 December 2010. The main objective was to establish a scientific basis for the development of an effective cysticercosis risk avoidance and impact mitigation strategy at this feedlot. Positive cysticercosis carcasses based on standard meat inspection procedures by independent meat inspectors at the Karan Beef Balfour Abattoir were related to their individual carcass classification and feedlot production histories as well as group/lot identities. A total of 17 561 cysticercosis infected carcasses were found, giving an overall prevalence of 2.72%. Data were examined using Descriptive Univariate and Multivariable Analyses, followed by detailed univariate analyses of putative risk factors. Individual risk factors were: Sex [Male (Bulls & Steers) vs Heifers], Arrival live weight groups (4), Breed, Days on Feed. Lot based risk factors were: Buyer, Geographical origin/loading point, purchase channel, farm type, number of measles/lot, rainfall season when purchased, drinking water turbulence vs stagnation during their feeding period, risk period per geographical area (high vs low) using high/low population density areas during high/low rainfall periods as categories, Bovine Respiratory Disease Risk as proxy indicator for cysticercosis. Cattle sourced via speculators and from small farms or communal herds as well as from certain dry areas where humans and cattle congregate/concentrate around limited water sources and similarly collection/concentration strategies such as holding stations, carried a significantly higher cysticercosis risk compared to controls. In addition cattle that arrived at a younger age (weight class) as well as cattle fed through the rainy season carried a higher risk. All of these factors indicate practical control measures in terms of purchase strategies, periods of more important staff deworming programmes and even future targeted vaccination strategies.