Development and Survival on Pasture of Gastrointestinal Nematode Parasites of Cattle

Abstract

Development and survival of the larvae of gastrointestinal nematode parasites of cattle under nearly natural conditions were studied in 14 trials during 1960-64 at the Agricultural Research Center, Beltsville, Maryland. Fecal pats containing nematode eggs were deposited on pasture; at subsequent intervals, the pats and surrounding herbage were examined for larvae. Trials with Ostertagia ostertagi, Cooperia oncophora, and C. punctata were begun in spring, autumn, and winter, with Oesophagostomum radiatum in spring and winter, with Haemonchus contortus sensu lato in summer, and with Nematodirus helvetianus in spring. The average monthly temperatures for good development of Ostertagia larvae were 55 to 70.3 F, and for Cooperia and Oesophagostomum, 60.3 to 70.3 F. The monthly precipitations for good development of all three genera were 1.04 to 3.75 inches. The average monthly temperatures for good recovery of Ostertagia larvae from the herbage were 44 to 70.3 F, for Cooperia, 50.9 to 75.6 F, for Oesophagostomum, 69.8 F, and recovery of all three genera was maximal at 69.8 F. The monthly precipitations for good recovery of larvae from the herbage were 1.77-5.42 inches. Initial, peak, and final recoveries of infective larvae from the feces occurred 1.5 to 9 (avg 4), 1.5 to 23 (avg 6), and 1.5 to 26.5 (avg 14) weeks after deposition of the pats, respectively. Initial, peak, and final recoveries of infective larvae from the herbage occurred 1 to 11 (avg 5), 1.5 to 23 (avg 11), and 5 to 35 (avg 16) weeks after deposition of the pats, respectively. The ranges in periods of recovery were attributed primarily to differences between seasons. Summaries of some of our knowledge of factors affecting the development and survival of the free-living stages of gastrointestinal nematode parasites of ruminants on pasture are given by Lucker (1941), Kates (1950), Gordon (1957), Crofton (1963), and Levine (1963). In six trials at the Agricultural Research Center, Beltsville, Maryland (Goldberg and Rubin, 1956; Goldberg and Lucker, 1959, 1963), infectiousness of different pasture plots was determined in four to six tests per trial by grazing helminth-free calves on the plots at various intervals after contaminating them with feces containing worm eggs. The trials were begun in spring, summer, and autumn. The study of development and survival of larvae within feces, under natural conditions, has been very limited. Information on development and survival of larvae within the feces, as well as infectiousness of the herbage, was obtained in the autumn trials (Goldberg and Lucker, 1963) by examination of the feces and herbage for infective larvae at intervals after deposition of the feces. In the present study, development and survival of larvae in feces and infectiousness of herbage were studied by direct examination. The trials were Received for publication 31 May 1968. begun under a wider range of weather conditions than in the previous trials, and tests per trial were more numerous. MATERIALS AND METHODS Fourteen trials were conducted during 1960-64. Development and survival of Ostertagia ostertagi and Cooperia (C. oncophora and C. punctata) larvae were studied in 11 and nine of them, respectively, begun in spring, autumn, and winter. Oesophagostomum radiatum was studied in seven of them begun in spring and winter, Haemonchus contortus sensu lato in the three begun in July, and Nematodirus helvetianus in the one begun in May. A few Trichuris eggs were present in some trials. In 11 of the trials, the feces containing nematode eggs were obtained from naturally infected cattle; in three, feces were obtained from experimentally inoculated calves. Batches of feces were thoroughly mixed in an electric mixer and from 7 to 18 (avg 9) pats per batch were prepared. The pats were nearly hemispherical, approximately 11 cm in diameter and 5 cm high, and had the consistency of normal cattle feces. They weighed 300 g in 10 trials, 200 g in two, and 150 and 50 g in one each. In each trial, two pats were mixed with amounts of charcoal and water considered close to optimum for larval development and were cultured in the laboratory under approximately optimal ambient temperatures, except in summer when the ambient temperature was usually above optimum. The numbers of larvae recovered from these cultures provided an index of the potential for production of infective larvae by the eggs in the pats. These cultures are referred to hereinafter