Two to four impala in the Nylsvley Nature Reserve were culled each month from February 1975- February 1976.
Two trematode species, 1 cestode species and 13 species of nematodes were recovered from these antelope. Of these, Fasciola gigantica, Gongylonema pulchrum, Haemonchus placei and Trichostrongylus falculatus are new records for impala.
In general, H. placei, Longistrongylus sabie and Impalaia tuberculata exhibited a similar pattern of seasonal occurrence. Adult worms were present during November-February, while marked inhibition in the development of large numbers of 4th stage larvae occurred from April-September or October. Cooperia hungi, Cooperioides hamiltoni and Cooperioides hepaticae followed a similar pattern, but inhibition in the 4th larval stage was not as marked and lasted from June-September.
No seasonal pattern of prevalence could be determined for Trichostrongylus spp. The worm burdens of young impala increased with the age of the animals and reached a peak when the impala were 1 year old.