The Life History of Cooperia oncophora (Railliet, 1898) Ransom, 1907, a Nematode Parasite of Cattle

Abstract

A pure strain of C. oncophora was established by injecting mature worms into the duodenum of a laparotomized, parasite-free calf. Eggs cultured at room temperature (26 to 30 C, 79 to 86 F) hatched within 16.5 hr and reached the first molt 28 hr after hatching. Infective third-stage larvae were observed 124 hr after hatching. Larvae completed the third ecdysis approximately 4 days after being fed to a calf. The final molt occurred 10 days postinfection, and eggs were present in the uteri of females 15 days after infection. The prepatent period ranged from 17 to 22 days. In the United States four species of the genus Cooperia are considered of primary importance in the aggregate parasitism of domestic ruminants. Only C. curticei, primarily a parasite of sheep, and C. punctata, a parasite of cattle, studied by Andrews (1939) and Stewart (1954), respectively, have had their life histories described adequately. The remaining two species, C. oncophora and C. pectinata, both principally parasites of cattle, have had insufficient study; therefore, a study was made of the life cycle of C. oncophora, comparing some aspects of the development of this nematode with C. punctata and C. curticei in similar stages of development. MATERIALS AND METHODS Day-old calves, obtained from local dairies, were raised in portable pens as described by Davis, Bowman, and Porter (1952). Infections were carried out in concrete-floored stalls that were swept and hosed with water daily. Pure cultures of C. oncophora were established in the following manner: Upon necropsy of a calf harboring a mixed helminth infection, gravid female C. oncophora together with some mature males were isolated from the intestinal contents and placed in 0.85% physiological saline. After administration of a general anesthetic, a laparotomy was performed on a parasite-free calf that had been deprived of food for 24 hr. The adult C. oncophora worms were thereupon injected into the duodenum of the calf. The injection was made with a 50-cc syringe equipped with a 16-gauge needle. Larvae were cultured from the feces of this animal in sphagnum moss (Cauthen, 1940) and collected, with the use of a Baermann apparatus, for study and for experimental inoculations. Eggs were recovered from feces by a modification of Stoll's method (Stoll, 1930, 1936). Larvae studied in their preparasitic stages were collected from cultures developing at room temperature (26 to 30 C, 79 to 86 F). Parasitic larvae were recovered from nine experimentally infected calves that were necropsied at varying intervals after infection (Table III). Measurements were made of worms that had been heat-killed and preserved in a 10% formalinRinger's solution. Drawings were made with the aid of a microprojector after Davis and Bowman (1954). In order to determine the endogenous distribution of this species, the intestines of two necropsied calves were ligated every 6 feet and the number of worms from each washed and scraped section was counted. RESULTS AND DISCUSSION Egg: The eggs of C. oncophora tend to be larger and somewhat more rounded than the eggs of C. pectinata, C. punctata, and C. curticei (Fig. E). The average length and width of 101 eggs were 84.3 (SD 4.7) and 42.4 a (sD 2.5), respectively. The mean form index (width divided by length, multiplied by 100) Received for publication 23 October 1962. * From a thesis submitted as partial fulfillment of the requirements for the degree of Master of Science in Zoology, Auburn University. The writer acknowledges the assistance of Dr. Dale A. Porter, Director, Regional Laboratory, under whose direction this study was made.