Seasonal Availability of Nematode Larvae on Pastures Grazed by Cattle in New South Wales

Abstract

Trends in the numbers of infective menatode larvae on pasture plots contaminated by cattle at different seasons of the year were defined in 3 different climatic regions. The main nematodes were Ostertagia ostertagi, Trichostrongylus spp, Haemonchus spp and Cooperia spp. On the North Coast of New South Wales with a sub-tropical climate, the numbers of infective larvae of all 4 nematodes rose rapidly to peak levels soon after each seasonal period of contamination began, then fell quickly within a few months. On the Central Coast of New South Wales, the trends were similar to those on the North Coast, except that the larvae persisted on the pasture for a much longer time. On the Northern Tablelands of New South Wales, where temperatures were much colder than on the coast, larval development was slower and major peaks of larval availability did not occur until early spring. These different seasonal trends in each region were considered to be related to the climatic differences between the regions. On pastures which were contaminated continuously, larval numbers reached maximum levels in mid-winter on the Central Coast and in early spring on the Northern Tablelands. It was concluded that the majority of these larvae were derived from the contamination of pastures in autumn and winter. Subsequently in summer, a rapid dying out of larvae was observed in all the regions, probably due to the effect of hotter weather. The studies suggest that a reduction in the contamination of pasture with nematode eggs in autumn and winter could result in pastures carrying fewer larvae and thus form the basis of effective worm control programs for cattle.

The ecology of infective larvae of bovine gastrointestinal trichostrongylids in dry season contaminated pastures in the Nigerian derived savanna

“…Similar observations have been reported from some temperate countries following prolonged dry weather (DURIE, 1961;ROSE, 1961ROSE, , 1962CHIEJINA & CLEGG, 1978;Young & ANDERSON, 1981;BARGER et al, 1984). In the summer rainfall areas of Australia, for instance, herbage larval counts in winter and spring following abnormally dry summers may exceed those encountered during the same seasons in years of normal rainfall (SMEAL et al, 1980). In these countries bovine faeces provide satisfactory conditions for development and survival of free-living stages of trichostrongylids during drought, so much so that their infective larvae (L 3 ) survive much better and longer inside dry faeces than they do on herbage during wet weather.…”

Dynamics of Infestation of Cattle and Pasture by Gastrointestinal Nematodes in an Atlantic Temperate Environment

“…Humidity has been shown to be a limiting factor that determines the level of infestation by larvae (Smeal et al, 1980;Baker et al, 1984). However, in temperate and cold areas, such as Great Britain, temperature is the factor that limits infestation (Pandey, 1974).…”

“…In Great Britain, the highest levels of infestation usually occur in July, whereas in southern European countries maximum levels occur earlier, and in colder countries they tend to occur later (Euzeby, 1977). Humidity has been shown to be a limiting factor that determines the level of infestation by larvae (Smeal et al., 1980; Baker et al., 1984). However, in temperate and cold areas, such as Great Britain, temperature is the factor that limits infestation (Pandey, 1974).…”

Epidemiologia das helmintoses pulmonares e gastrintestinais de bezerros em região de baixada do Estado do Rio de Janeiro

“…Segundo Smeal et al (1980), as chuvas causam desintegração do bolo fecal, e os estágios infectantes são submetidos aos efeitos deletérios do calor e da luz solar. Braga (1986) Durante o verão, as médias mensais das temperaturas má-ximas foram de 33,1°C, e as temperaturas das fezes, observadas diretamente, variaram de 36°C a 40°C.…”