A novel method for counting eimerian oocysts at very low concentrations inaqueous suspensions

A novel method for counting eimerian oocysts in samples of drinking water h as been developed to fulfil the need for monitoring the delivery of very lo w concentrations of live anticoccidial vaccines to poultry via pipeline nip ple-drinker systems. Advantages of the method are the case of sample collec tion and processing, high degrees of accuracy and precision, and a sensitiv ity of one oocyst in ml(-1). Results of a validation test are presented, wi th a protocol for the method and notes on its use. The coefficient of varia tion (CoV) of 10 sets of oocyst counts with nominal means of 10 to 160 oocy sts ml(-1) ranged from about 16 per cent down to 6 per cent. The recovery e fficiency for all 100 validation counts averaged 100.2 per cent with a rang e of 70-130 per cent. A practical example of field use of the method is giv en, including a modification to decrease the time taken for counting. In th is case, when oocysts were pumped around a pipeline circuit of 129 m for 2. 5 hours, the CoV of a mean of 112 oocysts ml(-1) (n = 10) was 12.4 per cent . (C) 2001 Harcourt Publishers Ltd.