The biological and genetic diversity of Neospora caninum is very limited because of availability of only a few viable isolates worldwide. This study describes the isolation and biological and molecular characterization of a new viable isolate of N. caninum (NC-SP1), from a cattle in Brazil. Approximately 400 g of brain from a naturally infected adult male cattle from an abattoir was fed to a 2-month-old dog. Neospora-like oocysts were observed on day 7 post-inoculation (PI) and the duration of oocyst shedding was 14 days. The DNA obtained from oocysts was characterized molecularly and the final sequence was 99% identical to homologous sequences of N. caninum available in GenBank®. For bioassay, gerbils (Meriones unguiculatus) were orally inoculated with 10 100 and 1000 oocysts; all gerbils remained clinically normal but developed N. caninum antibodies 14 days PI. Cell culture isolation was successful using the brain homogenate from one of the gerbils and tachyzoites were observed 24 days PI. Microsatellite genotyping revealed a unique genetic profile for this new reference isolate.

Cryptosporidium is a zoonotic protozoan parasite with public health importance worldwide. The objectives of this study were to (1) conduct a meta-analysis of published literature for oocyst shedding and diarrhoea outcomes, and (2) develop recommendations for standardization of experimental dose–response studies. Results showed that for the outcome of oocyst shedding in faeces, the covariates ‘experimental species’, ‘immunosuppression’, ‘oocyst dose’ and ‘oocyst dose’ × ‘age’ were all significant (P ⩽ 0·05). This study suggests that exposing mice, piglets, or ruminants, and using immunosuppressed experimental hosts, is more likely to result in oocyst shedding. For the outcome of diarrhoea in experimentally infected animal species, the key covariates ‘experimental species’, ‘age’ and ‘immunosuppression’ were significant (P ⩽ 0·2). Therefore, based on the results of this meta-analysis, these variables should be carefully reported and considered when designing experimental dose–response studies. Additionally, detection of possible publication bias highlights the need to publish additional studies that convey statistically non-significant as well as significant results in the future.

Genetic studies have demonstrated profound differences between the ‘porcine’ genotype of Cryptosporidium parvum, versus ‘human’ and ‘bovine’ genotypes. The study analysed infectivity and pathogenicity of the ‘porcine’ genotype (CPP-13 isolate) of C. parvum, and compared the results with published data on the ‘bovine’ genotype (CPB-0 isolate). This was investigated in calves and piglets from commercial herds. Piglets were mildly affected by the CPP-13 isolate, contrary to piglets infected with the CPB-0 isolate, which caused diarrhoea of a mean duration of 3·5 days. CPP-13 produced no or very mild clinical signs in piglets despite the excretion of high numbers of oocysts. Concomitant infection with rotavirus, however, caused a dramatic aggravation of the clinical signs, and 5 of 6 experimentally infected piglets died. CPP-13 appeared to be adapted to porcine hosts as illustrated by the lack of infectivity to 1 experimentally inoculated calf, and the absence of clinical signs, the long pre-patent period (15 days), and the excretion of very low numbers of oocysts following experimental infection of another calf. Thus, in accordance with other molecular studies, our results support the genetic evidence for the existence of a new species of Cryptosporidium adapted to pigs.