The Effects of Various Constant Temperatures on the Development of the Free Living-Stages of Some Nematode Parasites of Cattle

Abstract

The eggs and larvae of Cooperia punctata, C. oncophora, Ostertagia ostertagi, Trichostrongylus axei, and T. colubriformis displayed a similar rate of development in fecal cultures at various constant temperatures. In general, the rate of development for the five species accelerated as the temperature increased. There was an appreciable variability in the rate of embryonic and larval development in any one culture. The optimal temperature, based on the rate of development and percentage of eggs developing into infective larvae, was 25 C. No development beyond the gastrula stage occurred below 6 C. Above 32 C, development was faster than at lower temperatures, but mortality rate of the preinfective stages was very high. Various ecologic factors regulate the bionomics of the free-living stages of nematodes (Wallace, 1961). Of these factors, the temperature of the microenvironment has the greatest effect on rate of embryonation and development of the larvae of nematodes parasitic in cattle. Information on the effects of temperature on development has dealt primarily with Haemonchus contortus (Berberian and Mizelle, 1957; Silverman and Campbell, 1959). Data are also available on Ostertagia ostertagi (Rose, 1961) and Trichostrongylus spp. (Dinaburg, 1945; Silverman and Campbell, 1959). Results of investigations with other species of parasitic nematodes not covered in this work have also been reported, but most of them had primary interests other than the effects of temperature. The study reported here deals with the effects of various constant temperatures on the development of the free-living stages of Cooperia punctata, Cooperia oncophora, Ostertagia ostertagi, Trichostrongylus axei, and Trichostrongylus colubriformis. Some of these data have been presented in an abstract (Ciordia and Bizzell, 1960). MATERIALS AND METHODS To minimize the variables which characterize fecal cultures, each series of experiments was conducted with freshly voided feces from one calf. At least ten series of experiments were conducted at each of the temperatures studied. Each experiment consisted of from 3 to 18 replicate cultures at each of the temperatures, depending on the amount of feces available at that time. Feces were obtained from dairy calves with experimental monospecific infections of C. punctata, C. oncophora, O. ostertagi, T. axei, and T. colubriformis. Feces were also obtained from calves harboring mixed infections of these nematode species. The calves were kept in separate portable pens on a concrete floor, which was washed thoroughly daily. They were maintained on a ration of alfalfa hay ad lib. and 1 lb of grain/day. Freshly voided feces were thoroughly mixed, whereupon 10-g samples were taken out for routine nematode egg counts. When necessary, enough water was added to the feces to standardize the consistency to approximate that of normal feces (60 to 70% moisture). Feces for each series of experiments were divided into 100-g samples which were placed in 8 oz waxed paper cups (Lily-Tulip Cup Corp., No. 8S) and covered with snap-over lids (No. 16S-16) before being placed in constant temperature cabinets (low temperature incubators, mechanical convection, range 5 to 50 C, accuracy of ?1.0 C). Temperatures used were: 5, 10, 15, 20, 25, 32, 35, and 40 C. In addition, some cultures were incubated at 6 and 8 C to determine the lowest temperature at which larvae would develop. Cultures were kept moist by the periodic addition of water. This was necessary even though Received for publication 23 July 1962. * In cooperation with the Georgia Agricultural Experiment Station. Station Journal Series No. 424. Portions of this study were conducted as part of Southern Regional Project (S-21)-a cooperative study involving agricultural experiment stations in the Southern Region.