Interpretive Summary: Internal parasites, primarily helminths, are common pathogens of the cattle industry and substantially impact the economics of cattle production worldwide. Helminths can reduce the reproductive performance of the cow herd, reduce weaning weights, and, in general, negatively impact animal health. As such, a survey was performed collecting data from the major cattle producing regions of the US to evaluate parasite prevalence in weaned beef calves. Data from the USDA National Health Monitoring System’s (NAHMS) Beef 2007-08 study showed that cow/calf producers consider parasites to be a major problem in production. Results further demonstrated that there has been little change in parasite prevalence and numbers of eggs shed in the past 40 to 60 years, even with the extensive use of chemical treatment and less reliance on pasture management; this has been attributed to the rise in drug resistance. As resistance has emerged and production systems have become more high intensity, we are once again approaching the “steady state” in dissemination of GI nematodes observed back in the 40’s, 50’s and 60’s when drug treatments were either not available or not as effective as current treatments. As such the results of this study suggest that reconsideration must be given to a joint role for animal management and anthelmintic therapy to effectively control parasitic nematodes. These studies can be used by scientists and producers to help recognize and address the emergence of drug resistance in their cow/calf operations and to better manage the emergence of drug resistance in their cattle herds.
Technical Abstract: During the USDA National Animal Health Monitoring System’s (NAHMS) Beef 2007-08 study, 567 producers from 24 states were offered the opportunity to collect fecal samples from weaned calves and have them evaluated for the presence of parasite eggs (Phase 1). Producers choosing to participate were provided with instructions and materials to collect fecal samples. Up to 20 fresh fecal samples from weaned beef calves were collected on each of the 99 participating operations. Fresh fecal samples were submitted to one of 3 randomly assigned laboratories for evaluation. In the laboratories, all samples were processed for the enumeration of ‘strongyle’, Nematodirus, and Trichuris eggs using the modified Wisconsin technique. The presence or absence of coccidian oocysts and tapeworm eggs was also noted. In submissions where the ‘strongyle’ eggs per gram exceeded 30, aliquots from 2-6 animals were pooled for DNA extraction. Extracted DNA was subjected to genus level PCR identification for the presence of Ostertagia, Cooperia, Haemonchus, Oesophagostomum and Trichostrongylus. In this study 85.6% of the samples had ‘‘strongyle’’ type, Nematodirus and Trichuris eggs. Among the samples evaluated, 91% had Cooperia, 79% Ostertagia, 53% Haemonchus, 38% Oesophagostomum, 18% Nematodirus, 7% Trichuris and 3% Trichostrongylus. The prevalence of coccidia and tapeworm eggs was 59.9% and 13.7%, respectively.