Anthelmintic Activities of Cambendazole in Calves: Effect on Nematode Morphogenesis from Ova to the Infective Larval Stage

Abstract

Ten calves with natural gastrointestinal nematode parasitisms were used in an evaluation of the effects of cambendazole on nematode morphogenesis from ova to the infective larval stage. Five calves (Group I) were used as nonmedicated controls and 5 others (Group II) were given cambendazole orally at 25 mg/kg. Nematode eggs per gram of host feces (EPG) were recorded at 48 hr before treatment, at the time of treatment, and at 1, 2, 4, 6, 8, 16, 24, 48, 72, 96, 120, 144, and 168 hr after treatment (HAT). Fecal cultures were prepared at these same times and infective larvae per gram of feces (LPG) were enumerated 8 to 10 days later. LPG reductions in the Group II medicated calves were highly significantly different (P < 0.01) from the controls as early as 4 HAT and these reductions were nearly complete by 16 HAT. EPG reductions in the medicated calves were highly significantly different (P < 0.01) from the controls at 24 HAT and thereafter. The distribution of infective larvae identified from the control calves during the trial and from the treated calves until 2 HAT included 4% Haemonchus, 37% Ostertagia, 18% Trichostrongylus, 21% Cooperia, 3% Bunostomum, and 17% Oesophagostomum. Anthelmintic activities of cambendazole [isopropyl N (2-4 thiazolyl benzimidazole 5 yl) carbamate, Merck & Co., Rahway, N. J.] were first indicated by Hoff et al. (1970). The effectiveness and spectrum of the drug when given to calves was described in subsequent reports (Baker and Walters, 1971; Benz, 1971a, b; Ciordia and McCampbell, 1971; Egerton et al., 1970). Effects of a chemically similar compound, thiabendazole, on ova and development of larvae were reviewed and studied by Egerton (1969). Cambendazole was administered in this project to calves suffering from natural nematode gastrointestinal parasitisms to evaluate the effects of the drug on nematode development from ova to the infective larval stage. MATERIALS AND METHODS Ten calves of mixed Hereford and Angus breeds and approximately 6 to 8 months of age were used in this experiment. They were in satisfactory health and were passing numerous nematode ova in their feces when purchased. Received for publication 6 June 1972. *Publication No. 1110, School of Veterinary Medicine, Auburn University, Auburn, Alabama. Supported in part by a grant-in-aid from Merck Sharp & Dohme Research Laboratories, Rahway, New Jersey 07065. A ration of Coastal Bermuda hay and water was provided ad lib. throughout the trial. Each calf was placed in a separate portable pen 4 days before treatments were administered and confined there until the procedures were completed 11 days later. The pens were 4 to 5 m2 in area and were equipped with wooden slatted floors. Running water was used to clean the pens daily. The calves were randomly assigned either to the nonmedicated control group (I) or to the group (II) treated orally with cambendazole at 25 mg/kg in a previously described manner (Benz, 1971a). Three calves from each group were started in the trial sequence on the same day and the other 2 calves in each group were started a week later. A fecal sample was collected from the rectum of each calf at 7 AM 2 days (-48 hr) before treatments were administered. Samples were also collected at the time of treatment (0 hr), and at 1, 2, 4, 6, 8, 16, 24, 48, 72, 96, 120, 144, and 168 HAT. The EPG from each sample was estimated by using the modified McMaster technique (Whitlock, 1948). A fecal culture was also prepared from each sample by mixing 30 g of feces with 7 g of vermiculite in a waxed paper cup (7.8 g). Water was added to bring the total weight to 65 g. A plastic lid was placed on the cup and the culture was incubated at 25 C for 8 to 10 days. Each culture was weighed daily and water was added as necessary to maintain a constant weight. Infective larvae were collected from each culture by using the Baermann technique (Todd et al., 1970). Collections were made by draining all the water from each funnel and adjusting the total