Coccidiosis had been known as a significant problem in cattle since at least the early 1940's. Initially it was considered to be a disease of limited clinical importance, mainly affecting calves kept indoors in unhygienic conditions. VIDA data for diagnoses from faecal samples showed a rapid rise in positive levels for coccidiosis from 1993 to 1997, so that levels found positive were double to those seen pre-1993. This suggests some factor changed rapidly in the mid 1990's and it is postulated that this was the result of the removal of antimicrobial growth promoters (AGPs) by most major feed manufacturers. Data show that numbers of positive diagnoses is high in the seven months May to November and low from December to April. Thus whilst coccidiosis occurs throughout the year, coccidiosis incidence is variable with most cases occurring in June and fewest in February. Thus seasonally, coccidiosis levels are highest in the summer (July to September) and lowest in the winter (January to March). Diagnosis of outbreaks is often difficult because frequently faecal sampling is undertaken after, or occasionally before, the period of maximum oocyst shedding which is of relatively short duration. It is thus important to take samples from several animals within the group and not just those with signs. Various criteria are suggested to assist in diagnosis besides just relying on a faecal oocyst count usually considered to be over 5,000 oocysts per gram from affected animals as being diagnostic. Again in the mid 1990's, at a time when coccidiosis diagnoses were increasing, an alimentary syndrome became more prominent often referred to as chronic periweaning diarrhoea. This condition probably embraced several different problems and has been suggested to be due to various management, feed and infectious causes. However it is hypothesised that some outbreaks were in fact coccidial in origin, possibly aided by an alteration in concentrate fermentation patterns following the removal of AGPs from the feed. The costs of all diseases are hard to evaluate and coccidiosis is no exception. Calculable losses from clinical coccidiosis include: reduced production, mortality and the cost of treatment. However the losses due to subclinical infections probably far outweigh those of clinical disease. This is partly because of the widespread incidence of coccidial infestation in young cattle. Many of these subclinical effects are unquantifiable but they include impaired alimentary function, reduced feed conversion efficiency, reduced growth and increased susceptibility to disease. An attempt has been made to determine the costs of coccidiosis for cattle being produced for beef or as dairy replacements. At current prices quantifiable losses in affected animals are probably at least 24.50 pound to 59.25 pound plus the cost of any treatment at current farm prices.
