This report addresses various aspects of the protozoan parasite Eimeria which contribute to their increasing recognition as important protozoal pathogens in cattle. Among others, questions of parasite biology and epidemiology, its impact on host physiology, and control strategies are dealt with. The tenacious oocysts are found ubiquitously in the environment making an infection of calves and young cattle, the most susceptible age group, almost inevitable. Further development, comprising of asexual multiplication, the merogony, and a subsequent sexual stage, the gamogony, takes place within cells of the small and large intestines, after which numerous unsporulated oocysts are formed and shed with the faeces. Of the more than a dozen species, Eimeria bovis and Eimeria zuernii only are made responsible for severe clinical disease characterized by haemorrhagic diarrhoea with sometimes fatal outcome. To a lesser extent, Eimeria alabamensis also can cause clinical disease. Because of the damage inflicted on the intestinal tissue, the digestive process and overall homeostasis can become severely affected, even with absence of clinical disease, with adverse effects on animal welfare and performance. The consequent economic losses for the cattle industry are thus substantial. Active (species specific) immunity, both humoral and cellular, develops rapidly after first antigen contact, its intensity being dependent on the number of oocysts ingested. However, no absolute protection is achieved and even older animals can excrete oocysts, contributing to a state of endemic stability. For efficient control, exact diagnosis of the Eimeria species involved and the evaluation of animal management and husbandry practices are of utmost importance. Mixed infections are the rule and only an occurrence of pathogenic species, together with clinical symptoms, justifies the assumption of a coccidiosis. Proper hygiene regime and ensuring unfavourable conditions for oocyst survival in the environment (cool and dry, disinfection procedures) will help to reduce infection pressure on the herd. Of the various pharmacological compounds used to treat coccidiosis, those which act against the late developmental stages, administered during prepatency (metaphylactically rather than therapeutically), are currently considered most effective.

No abstract

In vitro culture of Cryptosporidium parvum oocysts in HCT-8 cells was combined with immunofluorescent labelling and digital image analysis to quantify the development of the parasite by detecting and measuring the labelled area in the respective cell cultures. The number of inoculated oocysts and the labelled area correlated reliably and significantly (R (2), 0.98-0.99). The effects of various concentrations of halofuginone bromide (0.00039 to 50 microM) and monensin (0.00225 to 0.144 microM) on in vitro parasite development were determined in further trials in cultures inoculated each with 10(5) oocysts. Monensin reduced the detected area in a dose-dependant manner. In comparison to the untreated controls, the area positive for C. parvum in the cultures treated with 0.144 to 0.009 microM monensin reached a maximum of 17%, and inhibition of 40% was observed at 0.0045 microM. Halofuginone bromide also efficiently inhibited parasite in vitro reproduction, albeit at higher concentrations. At 12.5 microM or more, inhibition was at least 90%; 0.05 microM still yielded 80% inhibition, whereas at concentrations below 0.00625 microM, labelled areas abruptly increased. Both drugs appeared efficient under in vitro conditions; the applied system is suited to screen drugs for their anti-cryptosporidial capacity.

The survival of Cryptosporidium parvum oocysts in anaerobic digesters treating manure was investigated for mesophilic, thermophilic, and a combined treatment (mesophilic-thermophilic-mesophilic) under different retention times of oocysts in the reactors. C. parvum DNA was extracted with an optimised protocol, and its amount determined by quantitative real-time PCR (qPCR). Results indicated noteworthy differences in DNA content after the different treatments. DNA was not degraded during the process. However, excystation and infectivity tests showed a reduction of viable oocyst numbers of > or = 2 and > or = 5 log units after the thermophilic treatment in two different experiments. Thus qPCR-targeting DNA can overestimate the number of oocysts that survive and remain viable after anaerobic digestion. However, targeting DNA is suitable to indicate the presence or absence of oocysts. Reverse transcription qPCR (RT-qPCR) targeting C. parvum hsp70 mRNA successfully indicated the presence of viable fraction of oocysts.

No abstract