Drug resistance in horses refers to the reduced effectiveness of medications, particularly antimicrobials and anthelmintics, in treating infections and parasitic infestations. This phenomenon occurs when pathogens such as bacteria, parasites, or viruses evolve mechanisms to withstand the effects of drugs that were once effective against them. In equine medicine, drug resistance poses challenges in managing diseases and maintaining the health of horses. Common areas of concern include resistance to antibiotics used for bacterial infections and resistance to anthelmintic drugs targeting parasitic worms. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, prevalence, and management strategies of drug resistance in equine populations.
Taylor MA, Hunt KR.The term 'anthelmintic drug resistance' describes the heritable ability of some nematode parasites to survive treatment with anthelmintic drugs at the recommended therapeutic dose levels. Genes for resistance appear to be present in many of the important pathogenic nematodes of ruminants and horses. Under intensive management systems, where heavy reliance is placed on anthelmintic drugs for worm control, the selection of resistant genotypes may result in increased reports of the drugs failing to control the nematode populations against which they are aimed. Anthelmintic resistance has been rep...
Herd RP.The serious and widespread problem of drug resistance has forced a re-thinking of basic philosophy regarding control of equine parasites. It has illustrated the dangers of total reliance on chemical control and stimulated the use of alternate strategies. Two new approaches are described. Prophylactic treatments in the spring and summer provide effective strongyle and colic control with less selection pressure for drug resistance. A nonchemical approach of pasture cleaning twice a week offers the same advantages with the added bonus of a 50 per cent increase in grazing area.
Drudge JH, Lyons ET.This review cites recent advances in the knowledge pertaining to infections of large strongyles in equids. Emphasis is placed on Strongylus vulgaris and attention is focused on pathogenesis of clinical manifestations of infections and treatment and control, including chemotherapy of migrating larvae and drug resistance.
Koterba A, Torchia J, Silverthorne C, Ramphal R, Merritt AM, Manucy J.A base-line study of bacteria isolated from horses admitted to the Veterinary Medical Teaching Hospital during a 6-month period was performed to determine the extent of multiresistant nosocomial infections caused by gram-negative aerobic bacteria other than Salmonella spp. Results of this study indicated that 21.9% of the 105 horses from which cultures and sensitivities were available had developed nosocomial gram-negative aerobic infections, with high rates of resistance to gentamicin, kanamycin, and trimethoprim sulfadiazine, three of the most often prescribed antibiotics in this hospital. I...
Benson CE, Palmer JE, Bannister MF.The antibiograms of 408 Salmonella species isolated from large animals were collected during a three year study from 1981 through 1983. The predominant Salmonella serogroup among these isolates was group B. A consistently high percentage of all isolates were resistant to ampicillin and tetracycline. A pattern of increasing resistance to chloramphenicol and gentamicin was documented for serogroup B isolates while the susceptibility of the isolates to neomycin increased. There was a decrease in the incidence of susceptibility to sulfamethoxazole-trimethoprim among the group E isolates. These cha...
Drudge JH, Lyons ET, Swerczek TW, Tolliver SC.Cambendazole (CBZ) treatments (20 mg/kg) given at 8-week intervals were used for parasite control in a breeding band of ponies (n = 33 to 43) during the period July 1974 to August 1978. Pre- and posttreatment worm egg counts on feces were used to evaluate efficacy of treatments after every 2nd treatment interval by monitoring changes in strongyle egg counts. Initially, effective reductions (expressed as 92% to 96% fewer worm eggs) were lessened to 70% by the 9th treatment (18 months) and to 28% by the 12th treatment, and thereafter, they fluctuated between 0% and 38%. Critical tests on animals...
Wray C, Sojka WJ, Bell JC.During the period 1973 to 1979 the number of recorded incidents of equine salmonellosis increased from 23 in 1973 to a peak of 111 incidents in 1976, but has since decreased to 32 in 1979. Of the 416 incidents recorded during the period of the survey 292 were caused by Salmonella typhimurium and 121 by 33 different serotypes; in three instances rough strains of salmonella were involved. The number of incidents caused by serotypes other than S typhimurium increased from one in 1973 to 32 in 1976. The number of different salmonella serotypes increased from two in 1973 to 23 in 1977 and has subse...
Apolinário ECF, Oliveira LLDS, Rocha RHF, Silva FVE, Santos IS, Alves CA, Dias Júnior JA, Mendes LJ, Lima WDS.The intensive use of anthelmintics has resulted in resistant parasite populations in horses. The objective of this trial was to evaluate the anthelmintic efficacies of the anthelmintics fenbendazole, ivermectin and abamectin in 24 horse farms in Northern Minas Gerais. Egg counts per gram of faeces (EPG) were performed individually in 619 animals. Animals presenting EPG counts greater than or equal to 150 were used in the tests on faecal egg count reduction (FECR), totalling 436 equines. These animals received the anthelmintics, fenbendazole, ivermectin, and abamectin. Faeces were collected 14Â...
Daugschies A.Drug resistance of parasites is a worldwide problem of increasing importance in animal production. Considerable information is available on the development of resistance in chicken coccidia and in strongyles of horses, sheep, goats and pigs. A review is given of the development, incidence, and management of drug resistance with emphasis on the situation in Germany.
Rivera-Velez A, Huber L, Sinha S, Cohen ND.Rhodococcus equi is a common cause of severe pneumonia in foals. Emergence of macrolide-resistant R. equi isolated from foals and their environment has been reported in the United States. A novel erm(51) gene was recently identified in R. equi in soil from horse farms in Kentucky. Our objective was to determine the effect of the erm(51) gene and associated rpoB mutation on the fitness of multidrug resistant-R. equi (MDR-R. equi) under different nutrient conditions. Bacterial growth curves were generated for 3 MDR-R. equi isolates and 3 wild-type (WTN) R. equi isolates recovered from environmen...
Hu B, Gao S, Zhang H, Li Q, Li G, Zhang S, Xing Y, Huang Y, Han S, Tian Y, Zhang W, He H.Rhodococcus equi (R. equi) is a Gram-positive zoonotic pathogen that frequently leads to illness and death in young horses (foals). This study presents the complete genome sequence of R. equi strain BJ13, which was isolated from a thoroughbred racehorse breeding farm in Beijing, China. Results: The BJ13 genome has a length of 5.30Â Mb and consists of a complete chromosome and a plasmid measuring 5.22Â Mb and 0.08Â Mb, respectively. We predicted 4,929 coding gene open reading frames, along with 52 tRNAs and 12 rRNAs. Through analysis of mobile genetic elements, we identified 6 gene islands and ...