Biomedical subjects
Publications and source records attributed to C Uhlinger.
Leukoencephalomalacia in horses is caused by fumonisins. These mycotoxins are produced by Fusarium spp. that contaminate corn and corn byproducts while in the field. The most common clinical presentation is a multifocal neurologic disease that affects multiple horses in a herd. Although the majority of affected horses die, treatment directed at decreasing inflammation and edema in the CNS may result in recovery in some animals.
Anthelmintic schedules that alternate between drug classes are widely used in horses. However, the results of investigations in which ovine nematode parasites were used have established that alternation of drug classes does not delay the development of drug resistance. This field study was designed to assess the effect of alternation of drug classes on the development of oxibendazole (OBZ) resistance in benzimidazole (BZD)-resistant equine small strongyles. A privately owned herd of horses was used for this study. These animals grazed the same pasture and had been treated with the same anthelmintic schedule for several years. Prior studies had determined that the animals were parasitized with BZD-resistant small strongyles. The herd was divided into 2 groups of 20 and 21 horses. Group-1 horses were given OBZ 6 times a year and had a total of 25 treatments with the drug. Group-2 horses were given OBZ 3 times a year, in alternation with non-BZD drugs, and had a total of 16 treatments. Statistical analysis revealed no difference between groups for the change in pretreatment fecal egg count following treatments 1, 4, 7, 10, 13, and 16. Alternation of drug classes did not effect the development of drug resistance in this trial. The efficacy of OBZ decreased with repeated treatments with the drug. By treatment 13, the efficacy, as evaluated by the fecal egg count reduction test, had decreased to less than 70% in both groups.
The prevalence of drug-resistant ovine parasites in the United States has not been widely reported. Thirteen flocks, typical of commercial sheep production units, were selected for survey. Four anthelmintics (fenbendazole, ivermectin, pyrantel pamoate, and levamisole) were tested for their ability to reduce herd mean pretreatment fecal egg count. If a properly dosed and administered drug failed to reduce herd mean pretreatment fecal egg count by 80%, it was considered ineffective in that flock, and the presence of parasites resistant to that drug was inferred. Fenbendazole administration changed pretreatment fecal egg counts by +9% to -100%. On the basis of the aforementioned definition, drug resistance existed in 6 of 13 flocks. Posttreatment larval culture indicated that Haemonchus contortus survived administration of fenbendazole. Levamisole, pyrantel pamoate, and ivermectin reduced pretreatment fecal egg count by -83% to -100%; resistance to these products was not evident in the flocks surveyed.
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A comparison was made between two different methods of reproductive management in the dairy cow. One protocol administered prostaglandin to open cows weekly; the other administered prostaglandin to open cows with a corpus luteum identified by rectal palpation. Survival analysis was used to analyze the data. Cows receiving weekly doses of prostaglandin had a 30% higher pregnancy rate (number of pregnancies per time) than the cows receiving prostaglandin based on rectal palpation of a corpus luteum. The average number of days to first insemination was shorter in cows given prostaglandin weekly.
A herd of 15 mature riding horses with a history of anorexia, weight loss, and lethargy was examined. The animals had been fed a 50/50 mixture of commercial sweet feed and corn screenings contaminated with a heavy growth of Fusarium moniliforme. Thirteen of the horses had one or more neurologic signs. The most characteristic signs were profound depression and mild ataxia. Over the 19-day course of the epizootic, the horses had increasing severe neurologic deficits, including unilateral blindness and delirium. Despite the clinical appearance of dehydration, 12 horses had low PCV (16 to 27%), hematocrit (21.2 to 31.0%; determined by automated cell counter), and RBC counts (3.76 to 5.5 x 10(6) RBC/microliters). White blood cell counts were variable (4,900 to 17,000 WBC/microliters). Necropsy findings included diffuse malacia of the white matter of the frontal cortex and severe multifocal perivascular hemorrhage in the white matter of the temporal cortex, basal ganglia, anterior medulla, and pons. One horse had a hepatic lesion consisting of a mixed inflammatory cell infiltrate and bile duct proliferation. The attack rate of this epizootic was 100%. The course of disease was unusually long in some animals. In an experiment, the fusarium-infected corn screenings were fed to horses and did not cause clinical signs or alterations in blood or serum biochemical values.
Four privately owned herds (25 to 49 animals per herd) were used in a five-year trial designed to evaluate the effect of anthelmintic schedules on the incidence of colic. These herds had been treated bi-monthly with non-ivermectin, non-benzimidazole drugs for two years before the trial. Prior parasitological studies showed that they had substantial pre-treatment faecal egg counts (900 to 2200 eggs per gramme), and that they were infected with benzimidazole-resistant cyathostomes. In Years 1 and 2 of the trial, all herds (A, B, C, D) were treated bi-monthly with non-ivermectin anthelmintics (Schedule I). In Years 3 to 5, Herd A received monthly non-ivermectin anthelmintics (Schedule II) and Herd C was treated with bi-monthly ivermectin (Schedule III). Herd B was treated with Schedule II in Years 3 and 4 and Schedule III in Year 5. Herd D was maintained on Schedule I throughout the study period. In each herd, the incidence of colic, while on Schedule I, was compared to the incidence while on Schedule II or III. The risk of colic for horses on Schedule I was 2.61 to 13.04 times that of the same horses while on Schedule II and 2.27 to 9.64 times that of the same horses while on Schedule III. In Herd D, treated according to Schedule I for five years, the incidence of colic did not vary significantly throughout the study period. More effective anthelmintic treatment schedules decreased the incidence of colic in these herds, supporting the conclusion that bimonthly treatment with non-ivermectin drugs may not maximise horses' health in all management conditions.(ABSTRACT TRUNCATED AT 250 WORDS)
Black walnut toxicosis was diagnosed in 10 horses at one stable. The time from exposure to shavings to development of clinical signs was 8 to 12 hours. Most common clinical signs were moderate to severe laminitis (Obel grade 2 or 3), pitting edema of the distal portion of the limbs, and rapid respiratory rate. Two horses had clinical signs of colic and 2 other horses had anorexia and lethargy. All 10 horses recovered without complications.
A survey was conducted to determine the prevalence of benzimidazole (BZ)-resistant small strongyles in horses in a southeastern Pennsylvania practice. Resistant parasites were found in 291 of 342 horses surveyed. Anthelmintic practices and pasture management factors in use for 3 to 6 years did not correlate with the presence of resistant small strongyles. Benzimidazole-resistant small strongyles were recovered in horses that had been treated alternately with BZ and non-BZ products and in horses receiving BZ products as infrequently as twice a year. However, inasmuch as the horses may have been infected with resistant small strongyles before the various anthelmintic schedules were implemented, it was not possible to attribute BZ-resistance to any particular pattern of drug use. Fifty-one (14.9%) horses had BZ-susceptible small strongyles: these horses were on poor overall parasite control programs and had received BZ products no more than once a year. Benzimidazole-piperazine and non-BZ drugs were effective in herds infected with BZ-resistant small strongyles.
A study was conducted to investigate the efficacy of six anthelmintics in a herd of dairy goats. Pretreatment larval cultures indicated that the goats were infected with Haemonchus contortus and Trichostrongylus colubriformis. Three separate treatment regimens were administered. In each trial, mature nonlactating goats were allocated into two treatment groups and a control group. Treatment groups received thiabendazole (TBZ) or levamisole (LEV), mebendazole (MBZ) or fenbendazole (FBZ), and morantel tartrate (MOR) or ivermectin (IVR). LEV, MOR, and IVR reduced fecal strongyle egg counts by 99% to 100% of pretreatment values. The benzimidazole (BZD) drugs changed pretreatment fecal egg counts by +2% to -32%. Results of posttreatment larval culture demonstrated the presence of H contortus larvae following the administration of BZD drugs.