Studies on Nematode Infections of Beef Cattle in New South Wales

Abstract

The occurrence and seasonal trends of nematode parasite infections in beef cattle on the Tablelands and North Coast regions of New South Wales are described, based on worm counts from 627 spring-born steers slaughtered at 2-monthly intervals from 6 to 24 months of age. The predominant parasites were Ostertagia ostertagi, Trichostrongylus axei and Cooperia spp. Large burdens of adult Ostertagia were seen in 12-month-old animals in late winter and early spring, and later in 18- to 20-month-old cattle in the following late summer and autumn. These infections often resulted in outbreaks of clinical parasitism. Massive numbers of inhibited early fourth stage larvae (EL4) also accumulated in the yearlings during their first spring, reached peaks in mid-summer and then declined. The possibility of their resumption of development to mature worms in the late summer and autumn period is discussed. Adult T. axei showed a similar seasonal trend to Ostertagia and may have increased the severity of outbreaks of clinical disease. Cooperia populations of EL4 and adult worms were highest in weaners during winter, but lower numbers thereafter indicated a strong resistance to re-infection. In addition, Haemonchus placei occurred frequently on the North Coast both as EL4 and adults in cattle of all ages up to 20 months. Of the other cattle nematodes, Oesophagostomum radiatum and Trichuris spp occurred in low numbers, mainly in weaners. Bunstomum phlebotomum and H. contortus occurred sporadically on the North Coast and Tablelands respectively. Intestinal Trichostronglyus spp, Oesophagostomum venulosum and Dictyocaulus viviparus were seen occasionally and Nematodirus spp were not seen. There was a poor relationship between worm counts and faecal egg counts. Cooperia spp dominated the egg counts, while those for other genera were generally low and did not reflect the relative abundance or seasonal changes in worm numbers.

The epidemiology of Ostertagia ostertagi and other gastrointestinal nematodes of cattle in Louisiana

“…Michel, Lancaster & Hong (1976a) reported that just as inhibited development may be induced by more than one cause, resumption of development might be induced in at least 3 circumstances: (a) a small, constant number resumes its development every day, (b) the rate is very greatly increased during March (northern temperate conditions) and (c) the increase may also occur earlier, apparently through a breakdown of host resistance. Other investigators (Bowen, 1979;Smeal, Hotson, Mylrea, Jackson, Campbell & Kirton, 1977;Smeal & Donald, 1981) have indicated the occurrence of variations of the 0. ostertagi population structure during the time of larval inhibition (mid-summer onward in Australia), but their conclusions were primarily concerned with adult worm burdens being supplied by summer transmission of new infection as well as by maturation of inhibited larvae. The present data indicate an early triggering of maturation of large numbers of spring-acquired EL 4 during May, followed by persistence of smaller numbers of EL 4 during summer, and lastly, a concommitant final decrease in numbers of EL 4 and substantial rise in numbers of adult worms during August-October 1981.…”

“…Continuous sub-normal rainfall from spring into summer and decreasing quantities in August and September, very low herbage larval counts throughout the period, and low to near nil 0. ostertagi worm counts in tracer calves from June through October, indicated rather conclusively, that the severe parasitism observed in yearlings during August through October 1982, was due solely to maturation of large burdens of 0. ostertagi, compounded by large numbers of newly acquired or earlier accumulated T. axei. The additive, combined pathogenic effect of T. axei with large 0. ostertagi burdens has been emphasized by Smeal et al (1977).…”

Inhibition of development of Ostertagia ostertagi – effect of temperature on the infective larval stage

“…Source and maintenance of 0. ostertagi A field isolate was obtained in autumn 1975 from an 18-month-old Hereford heifer which had grazed on a farm in the Northern Tablelands of New South Wales since birth. At this time of year an animal of this age would have some mature worms and a pool of inhibited larvae acquired in the previous spring (Smeal, Hotson, Mylrea, Jackson, Campbell & Kirton, 1977). At the beginning of autumn, the animal was housed and treated with levamisole a t 10 mg/kg to remove adult worms.…”

“…All calves were killed 24 days after infection. Abomasal worm counts were performed by the technique of Smeal et al (1977), except that the contents and washings were combined, in a 2 1 volume before counts were made.…”

PRODUCTION EFFECTS OF LIVER FLUKE (FASCIOLA HEPATICA) INFECTION IN BEEF CATTLE

“…Total worm counts were undertaken on abomasums and digests of abomasal mucosa according to the method of Smeal et al(1977).…”