Stilbazium Iodide as an Anthelmintic. II. Against Various Nematodes of Dogs and Cats

Abstract

Stilbazium iodide, which was effective against the mouse pinworm Syphacia obvelata, was tested against three species of hookworms, three of roundworms, and one of whipworm in 120 dogs and cats. Two or three 25 mg base/kg doses removed most Ancylostoma caninum, A. tubaeforme, Uncinaria stenocephala, Toxocara canis, and T. cati, but Toxascaris leonina was more resistant. The drug is active against Trichuris vulpis in dogs when it is given in courses of 3 to 6 doses of 25 mg base/kg or higher. Two or more courses may be necessary for puppies and for dogs having narrow cecal openings or extensively coiled ceca. Except for five dogs with atypical ceca, 24 of 29 dogs given these multiple doses averaged over 90% elimination of whipworms, with 18 of the 24 having complete clearance. Vomiting is negligible in these animals provided the dose is less than 50 mg base/kg. This compound is in human clinical trial against hookworms, ascaris, whipworms, and pinworms. Some of the pyridines found active against the mouse pinworm Syphacia obvelata were tested against various nematodes of dogs and cats and were found effective against a number of species (Phillips and Burrows, 1961; Burrows, Hunt, and Lillis, 1961). The most active against Syphacia, stilbazium iodide, is relatively nontoxic (Burrows and Hunt, 1962) and it was found also to be the best against dog and cat nematodes. A series of trials was set up to test the effectiveness of stilbazium against three species of hookworms, three of roundworms, and one of whipworm in these animals. Several different dosage levels were used in these experiments in an endeavor to find the optimum dosage for the various species. MATERIALS AND METHODS From stool examinations done on all stray dogs and cats and from registered beagle puppies received by this laboratory, those animals showing moderate to large numbers of eggs of one or more species of nematodes in zinc sulfate flotation preparations were selected for trial. One hundred and twenty animals (55 dogs, 32 puppies, and 33 cats) were used in the trials. There were 207 infections (106 in the dogs, 56 in the puppies, and 45 in the cats) in these animals against which stilbazium was tested. Dogs and puppies selected for treatment were switched from a Gaines meal diet to a canned dog food diet the day prior to treatment as it is less time-consuming to search for passed worms in the canned food debris. Cats were kept on canned cat food before and during treatment. The compound was administered orally in gelatin Received for publication 1 August 1962. capsules according to mg of base per kg of body weight. As the iodide salt makes up nearly onefourth of the weight of the compound, it was necessary, for example, to give 32 mg of the compound per kg in order to have 25 mg of base per kg. Animals given a single dose in a day received the drug between 0830 and 0930 and were fed between 1230 and 1330. Those given 2 doses a day had the second dose at about 1600. All fecal specimens were collected from all animals after treatment began, and this was continued until the animals were autopsied. Those given a single dose were autopsied after 48 hr; those dosed for 2 or more days were autopsied 48 hr after the last dose, except that those treated for whipworm infection were followed for 7 days after the initial dose. Animals were killed with a lethal dose of Nembutal given in the heart and were autopsied i mediately. Fecal material was washed through a 40-mesh sieve and the sieve contents examined, a little at a time, in a black-bottomed pan for worms passed. At autopsy the stomach and intestines were examined carefully for worms remaining. The contents of the large intestine were considered part of the last fecal specimen, except for living whipworms still attached to the cecum or large intestine. The percentage of elimination of worms was computed for each species of helminth of each animal by dividing the number passed by the number harbored. The average percentage of elimination of a species, to the nearest whole digit, was found by averaging the percentages of all animals harboring that species and having been given the same dosage level. It was not possible to autopsy six of the dogs or the 32 puppies used in these experiments, but the percentage of elimination was determined from the averages of three preand three post-treatment Stoll egg counts, the former being done the week prior to treatment and the latter beginning 7 or 8 days after the initial dose.