IMPACT OF MIXED STRONGYLE INFECTIONS IN FOALS AFTER ONE MONTH ON PASTURE

Twelve Standardbred foals (age 3-6 months), with little previous expos ure to parasites, were allocated to 2 groups and put onto pasture with low (Group L) or high (Group H) levels of larval contamination of lar ge strongyles and cyathostomes. After 4 weeks grazing in September, th e foals were housed indoors until necropsy 15 weeks later. Foals in Gr oup A became clinically more affected than those of Group L in that th ey showed loss of vigour, weight gain depression, intermittent soft fa eces and inappetence, One foal of Group H had persistent diarrhoea and was subjected to euthanasia 12 weeks after housing. Signs of colic we re not observed, Faecal egg counts were significantly higher in Group A than in Group L (P<0.05). At necropsy, the mean number of S. vulgari s and cyathostomes was 20 and 18,000, respectively, in Group L, and 16 7 and 25,000 in Group H. Routine blood chemistry did not specifically reveal presence of S. vulgaris in pre-patency, A transient neutrophili a and eosinophilia, most prominent in Group Ei, was seen 2-8 weeks aft er start of exposure and anaemia was observed later in Group H. Serum albumin and albumin/globulin ratio were reduced, particularly in Group H, and a marked hyperbetaglobulinaemia was observed at 16-20 weeks in Group H, In conclusion, heavy infections with strongyles including S. vulgaris may become established in weaned foals after a brief period on pasture, Infections may be expressed clinically as debilitation, in appetence and intermittent diarrhoea without colic, and the need for c ontrol is imperative.