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Biomedical subjects

A C Todd

Publications and source records attributed to A C Todd.

At least 91 records · Page 5Linked to original sources
PubMed1976

Development of the large American liver fluke, Fascioloides magna, in white-tailed deer, cattle, and sheep.

The comparative development of Fascioloides magna in white-tailed deer, cattle and sheep has been studied. Flukes were recovered from 72% of 32 deer administered 40 to 500 metacercariae, from 82% of 11 cattle administered 10 to 500 metacercariae, and from 53% of 15 sheep administered 8 to 200 metacercariae. The percentage recovery of the flukes administered as metacercariae was 4.1% of 6,130 in deer, 5.7% of 2,510 in cattle, and 4.7% of 1,213 in sheep. Flukes were recovered only from livers of infected deer, while in cattle, 1 fluke was also found in the lungs of each of 2 animals. In sheep, all but 10 flukes were recovered from the livers; 6 were found in the lungs and 4 in the abdominal cavities. The black iron porphyrin pigment associated with F. magna infection was found to be most widespread in cattle and sheep, but was also a pathognomonic feature in deer. Growth of the fluke was similar in all 3 host species tested, but eggs were passed only from deer, the normal definitive host. In cattle, the eggs were retained in the liver, and F. magna was lethal to sheep before its own maturity was attained. In cattle and deer, flukes matured approximately 7 months after exposure, but immature migrating flukes were found 12 months after infection and apparently can remain in this retarded state for an undetermined period of time.

Animals↗
PubMed1976

Controlled evaluation of fenbendazole as a bovine anthelmintic.

Calves experimentally infected with Haemonchus, Ostertagia, and Cooperia, and to lesser degrees with Trichostrongylus, Oesophagostomum, Nematodirus, and Bunostomum were used in a controlled experiment to record the anthelmintic efficacy of a benzimidazole compound methyl 5-(phenylthio)-2-benzimidazolecarbamate at dosage levels of 3.5, 5, and 7.5 mg/kg bodyweight. With the 3 dosages, reductions of Haemonchus were 96.7, 99.2, and 99.8%; of Ostertagia, 97.2, 97.2, and 99.5%; and of Cooperia, 99.9, 99.9, and 99.9%. Pronounced reductions were also recorded for Trichostrongylus, Nematodirus, Oesophagostomum, Trichuris, and Capillaria, but these populations were too numerically small or too unevenly distributed within the control groups to be given much emphasis. The experimental parasitic populations which developed in the 10 control calves amounted to 91, 763 worms (total).

Animals↗
PubMed1976

Suppression and control of experimentally induced procine coccidiosis with chlortetracycline combination, buquinolate, and lincomycin hydrochloride.

Weaned pigs were divided into nonmedicated control and medicated principal groups and 3 days later were exposed to infective oocysts comprised of mixed species of swine origin. In separate experiments, a chlortetracycline combination (plus sulfamethazine and penicilin), buquinolate, or lincomycin was administered prophylactically to the principals, starting 3 days before they were exposed to infection, and then was evaluated for efficacy against the experimental exposures. Comparisons between control and principal groups were made on the basis of fecal oocyst counts, fecal consistencies, and body weight gains. On the basis of oocyst counts, both chlortetracycline combination and buquinolate minimized the development of coccidial populations in groups given medicated feed; nonmedicated controls discharged substantial numbers of oocysts. Lincomycin medication was not effective in pigs given 111 mg/kg of feed; it was effective at dose levels of 330 mg/kg of feed and at 22 mg/kg body weight, intramuscularly. Medicated principals always gained more weight on the average than did their infected nonmedicated controls during the experiments. The data on oocyst production support the position that the 3 compounds can function as coccidiostats in swine.

Animals↗
PubMed1976

Efficacy of oxibendazole against adult and larval nematodes of cattle.

Calves which were artificially infected with Haemonchus, Ostertagia, Trichostrongylus, Cooperia, and Oesophagostomum but which were also carrying natural infections of Nematodirus and Trichuris were treated with 15.0 mg of oxibendazole (methyl-5-n-propoxy-2-benzimidazole-carbamate)/kg of body weight at 3 days, 7 days, and 42 days after exposure to the infective trichostrongylid and strongylid larvae. Efficacies against adult populations of these genera treated on day 42, except Trichostrongylus, exceeded 98%. The chemical was highly effective against immature nematodes of the genera, except Oesophagostomum (0%). Data were not obtained on Trichostrongylus. The oxibendazole premix was palatable, and toxicosis due to the chemical was not seen in these calves.

Animals↗
PubMed1975

Age group interaction of Haemonchus contortus in premunized lambs.

Lambs premunized with a relatively less pathogenic (RLP) isolate of Haemonchus contortus were challenge exposed each day with 500 3rd-stage larvae (L3) of a normally pathogenic isolate of the same worm, starting on day 9 of the premunition-induced infection. In 6-month-old lambs, there was a fourfold decrease in egg production by the premunizing RLP isolate with challenge exposure compared with egg production in lambs given only the premunizing RLP isolate and not challenge exposed. Premunized lambs were able to carry larger worm burdens with less hemoglobin loss than were nonpremunized challenge-exposed control lambs. Although challenge exposure had affected parasitic egg production by the 9-day-old premunizing RLP worms, the same young infective isolates were able to survive and protect lambs against the additional parasitism.

Abomasum↗
PubMed1975

Efficacy of Fenbendazole against gastrointestinal parasites of sheep.

Lambs severely parasitized by Haemonchus, Ostertagia, Trichostrongylus, Cooperia, Oesophagostomum, and Nematodirus were treated with fenbendazole (methyl 5-(phenylthio)-2-benzimidazolecarbamate) given at 3 dose levels: 3.5, 5.0, and 7.5 mg/kg of body weight. Efficacies against these genera, except Haemonchus and Nematodirus, were 100% at the 3 dose levels. Efficacies for the 3 doses against Haemonchus were 93.4, 95.3, and 99.8%, respectively, and against Nematodirus, 99.5, 99.6, and 100%. Efficacies for the doses against Trichuris were 69.1, 83.6, and 98.2%. Toxicosis due to the durg was not seen in these lambs, although they were severely debilitated.

Animals↗