Cryptosporidium-associated diarrhoea in neonatal calves in Algeria

Neonatal calf diarrhoea triggered by the enteric protozoan parasite Cryptosporidium is a leading cause of morbidity and mortality in calves aged 1-month-old or younger globally. Infected cattle in general and calves in particular have also been demonstrated as major contributors of zoonotic C. parvum oocysts in the environment and have been linked to a number of waterborne outbreaks of human cryptosporidiosis. Little is known on the occurrence, geographical distribution, and molecular diversity of Cryptosporidium infections affecting bovine populations in Algeria. In this study faecal specimens were randomly collected from 460 cattle aged between two days and 18 months on 10 farms located in the provinces of Aïn Defla, Blida, Sétif, and Tizi Ouzou between the autumn of 2015 and the spring of 2016. Faecal samples were microscopically examined using the modified Ziehl-Neelsen acid-fast technique as screening method. Microscopy-positive samples were confirmed by a commercial coproantigen enzyme-linked immunosorbent assay (Bio-X Diagnostics). The identification of Cryptosporidium species and sub-genotypes in confirmed samples was conducted by PCR and sequence analyses of the small subunit ribosomal RNA (ssu rRNA) and the 60 kDa glycoprotein (gp60) genes of the parasite. Overall, 52.2% (240/460) of the investigated cattle tested positive to Cryptosporidium by microscopy. The infection was widespread in all 10 farms surveyed, but was significantly more prevalent in those from Blida in the central part of the country. Bovine cryptosporidiosis affected cattle of all age groups but with different outcomes. Pre-weaned (up to one month old) calves typically presented with diarrhoea, whereas older animals mostly harboured sub-clinical infections. The commercial ELISA used only detected 15.8% (38/240) of the samples that previously tested positive by microscopy, demonstrating a poor performance in field epidemiological surveys. Sequence analysis of the 29 isolates generated at the ssu rRNA loci confirmed the presence of four Cryptosporidium species including C. parvum (72.4%), C. bovis (13.8%), C. andersoni, (3.4%), and C. ryanae (3.4%). Two additional isolates (7.0%) could only be identified at the genus level. Eight out of the 21 isolates assigned to C. parvum were identified as sub-genotype IIaA16G2R1 at the gp60 locus. C. parvum was almost exclusively found infecting pre-weaned calves, whereas C. ryanae and C. andersoni were only detected in asymptomatic animals. Bovine cryptosporidiosis is highly endemic in the surveyed area and represents a veterinary public health concern that should be adequately tackled by Algerian veterinary health authorities and policy makers.